Статті в журналах з теми "Swirling cross flows"

The flow inside the volute of a centrifugal pump is threedimensional and, depending upon the position of the inlet relative to the cross-section center line, a single or double swirling flow occurs. The purpose of this study was the calculation of the three-dimensional swirling flow inside the centrifugal pump volute.The developed flow solver provides detailed pressure and velocity distribution information inside the volute, and the calculated results are verified by means of the experimental results presented in the literature.Three-dimensional continuity and momentum equations are solved by means of an artificial compressibility technique. The finite volume approach is applied for space discretization, and an explicit fourth-order modified Runge-Kutta scheme is used for time discretizetion.Calculations are performed at three different mass flows, one of which corresponds to the design's point mass flow. The calculated volute flow conditions—namely, the variation in static pressure and total pressure and the through-flow and swirling component of the flow velocity over the cross-sections, which are located at various circumferential positions—are compared with the experimental data in detail, and they exhibit a good agreement with the measured flow field.

The current trends for next generation turbofan engines are towards shorter nacelles and increased distances between the fan and the outlet guide vanes. This leads to an overall reduction in lined surface areas as well as an increase in the relative importance of the interstage liner, which is the liner placed between the rotor blades and the stator vanes. So far most of the efforts have been on liners for intakes and bypass ducts. The interstage is different in that the liner is subject to a mean flow with a strong swirl component and shear. The SwirlProp code was developed to contribute to understanding and predicting the effect of the swirl on liner attenuation. The code is based on the linearized Euler equations together with the Ingard–Myers boundary condition. An eigenvalue problem is formulated and discretized using a finite difference method. The code is exhaustively compared against predicted values obtained by other methods for uniform, sheared and swirling mean flows and hard-walled and lined ducts. A cross-validation between SwirlProp and an in-house code from Rolls-Royce was carried out for a more realistic case. Also, details on the implementation of the boundary condition are proposed and details are presented.

Nonsymmetric branching flow through a three-dimensional (3D) vessel is considered at medium-to-high flow rates. The branching is from one mother vessel to two or more daughter vessels downstream, with laminar steady or unsteady conditions assumed. The inherent 3D nonsymmetry is due to the branching shapes themselves, or the differences in the end pressures in the daughter vessels, or the incident velocity profiles in the mother. Computations based on lattice-Boltzmann methodology are described first. A subsequent analysis focuses on small 3D disturbances and increased Reynolds numbers. This reduces the 3D problem to a two-dimensional one at the outer wall in all pressure-driven cases. As well as having broader implications for feeding into a network of vessels, the findings enable predictions of how much swirling motion in the cross-plane is generated in a daughter vessel downstream of a 3D branch junction, and the significant alterations provoked locally in the shear stresses and pressures at the walls. Nonuniform incident wall-shear and unsteady effects are examined. A universal asymptotic form is found for the flux change into each daughter vessel in a 3D branching of arbitrary cross-section with a thin divider.

This paper is devoted to experimental study of the instantaneous and average flow structure in the pre-mixed propaneair swirling flames using optical noncontact PIV (Particle Image Velocimetry) method in stereoscopic configuration. A visualization of the typical regimes of combustion for the swirling and non-swirling flame in a wide range of Reynolds numbers and equivalence ratios is presented. In addition, boundaries of steady combustion are defined. Measurements of instantaneous velocity fields for typical combustion regimes are performed. Instantaneous velocity fields were used to calculate the spatial distribution of the mean velocity and turbulence kinetic energy component. Interaction of the flame with a large-scale vortex structures is studied. It shows significantly different effects of burning on the turbulent structure of twisted jet. The paper describes algorithms of data processing, in particular, adaptive cross-correlation method of calculating the instantaneous velocity fields based on an analysis of the local particle image concentration. This method allows to effectively filtering out the velocity vector outliers, which appear in areas with low concentration of tracers during gas flows diagnostics, and calculate the spatial distribution of such characteristics as the intensity of turbulent pulsations.

Transient, steady and oscillatory flows in a $180^{\circ }$ curved pipe are investigated both numerically and experimentally to understand secondary flow vortex formation and interactions. The results of numerical simulations and particle image velocimetry experiments are highly correlated, with a low error. To enable simulations in a smaller domain with shorter inlet section, an analytical solution for the unsteady Navier–Stokes equation is obtained with non-zero initial conditions to provide physical velocity profiles for the simulations. The vorticity transport equation is studied and its terms are balanced to find the mechanism of vorticity transfer to structures in the curved pipe. Several vortices are identified via various vortex identification (ID) methods and their results are compared. Isosurfaces of the $\unicode[STIX]{x1D706}_{2}$ vortex ID are used to explain the temporal and spatial evolution of vortices in the curved pipe. Eigenvalues and eigenvectors of the velocity gradient tensor are calculated for the swirling strength vortex ID method, which also determines vortex axis orientation. The classical Lyne vortex in oscillatory flow with an inviscid core is also revisited and its results are compared with the transient and steady flows. These in-depth analyses provide a better understanding and characterization of vortical structures in the curved pipe flow. Our findings show that, although there are some visual similarities between cross-sectional views of steady/transient flows and oscillatory flows, the structure herein designated as Lyne-type vortex detected in the cross-sections (under steady, transient and pulsatile flows) is not the same as the classical Lyne vortex pair (in oscillatory flows).

A brief review on three problems from the multiphase media mechanics area related to the study of the dynamic behavior of disperse systems under various conditions and methods of interaction with external fields or the environment is presented. The problems are an integral part of the scientific project “Hydrodynamic effects in multiphase and thermoviscous media under wave and thermal effects”. The review is carried out in the context of the vector of development of modern research in the relevant areas. As a part of solving the problem of acoustic wave scattering by a set of spherical bubbles or drops, taking into account their sound permeability, the fast multipole method was developed to expand the possibilities of its application in the considered cases. On the basis of addition theorems for spherical wave functions, a new formula for the total scattering cross section for a set of interacting sound-permeable spheres arbitrarily located in space is obtained. An important aspect of the research was the estimation of the region in the parameter space of the problem, in which the effects of multiple scattering are significant. The second problem is related to mathematical modeling of a swirling turbulent flow containing particles of a dispersed phase. For numerical studies of temperature stratification in a vortex tube, an algorithm and a computer code were created using an orthogonalized finite-volume mesh with separation of the near-wall layer. A number of parametric studies have been carried out, in particular, the dependence of the temperature of the outgoing air in the cold diaphragm channel depending on the diameter of the diaphragm has been considered. In order to increase the efficiency of geological exploration in solving the third problem for describing the process of magmatic ore formation, a system of equations based on the methods of mechanics of multiphase media and thermohydrodynamics is proposed. The mathematical model provides for the heat exchange of the magmatic melt flow with the surrounding host rocks, as well as the release of heavy and light fractions from basaltic magma during its cooling. The results obtained in the course of the computational experiment indicate the possibility of a periodically inhomogeneous nature of the distribution of ore-forming fractions.

The article is devoted to the theoretical study of the operation process of the borehole ejection system as part of the tubing string, jet pump and packer installed below; the system implements the hydrojet method of oil well operation. The improved design of the jet pump contains inclined guiding elements placed in its receiving chamber for swirling the injected flow, which results in an increase in the efficiency of the borehole ejection system. Based on the law of conservation of liquid momentum in the mixing chamber of the jet pump and taking into account the inertial pressure component caused by the swirling of the injected flow, there is obtained the relative form of the equation of the ejection system pressure characteristic, the structure of which contains a component that determines the value of the additional dynamic head. According to the results obtained, the additional dynamic head caused by swirling of the injected flow is determined by the ratio of the geometric dimensions of the flow path of the jet pump, the angle of inclination of the elements for creating vortex flows, and the ratio of the power and reservoir fluids. In the case of asymmetric swirling of the injected flow, an increase in the value of the relative displacement of the jet pump decreases the value of the additional dynamic pressure. In order to study the effect of flow swirling on the energy characteristic of the ejection system, the pressure characteristic of the jet pump was transformed into the dependence of its efficiency on the injection coefficient. Jet pump models with the ratio of the cross-sectional areas of the mixing chamber and the nozzle of 5.012 and 6.464, respectively, were used to check the adequacy of the theoretical pressure and energy characteristics obtained during the simulation of the performance process of the concentric ejection system. The average error in the theoretical determination of the pressure and efficiency of the vortex jet does not exceed 8.65% and 6.48%, respectively.

Measurements of the three-dimensional flow in a simplified model of a centrifugal compressor volute at design and off-design operation are presented. A nearly constant swirl velocity is observed near the walls and a forced vortex type of flow is observed in the center. This velocity distribution is almost identical at all cross sections and all operating points. An explanation is given on how this swirl distribution results from the specific way a volute is filled with fluid. The throughflow velocity component shows a large crosswise variation. A minimum or maximum velocity is observed at the volute center depending on the operating point. A simple analytic model, based on the radial equilibrium of forces, is described. Calculations for isentropic flows reveal the relation between the swirl distribution and the large increase of throughflow velocity toward the center. This explains why volutes should be designed with negative blockage. Nonisentropic calculations, using the experimental loss distribution, correctly reproduce the measured throughflow velocity and static pressure distribution.

In this article, a theoretical analysis of the flows arising in the cross sections of fluid and gas flows is performed. Such flows are subdivided into secondary flows and coherent structures. From experimental studies it is known that both types of flows are long-lived large-scale movements (LSM) stretched along the flow. The relative stability of the vortices is traditionally explained by the fact that the viscous friction forces that inhibit the rotation are compensated by the intensification of the swirl when moving slowly rotating peripheral layers to the center of the vortex due to longitudinal tension. An analysis of this mechanism made it possible to develop a relatively simple model of vortex structures in which the viscous friction forces and axial expansion are considered to be infinitesimal. Under these assumptions, one can use the equations of motion of an ideal fluid in the variables “stream function - vorticity”. It is shown that under certain assumptions these equations take the form of a wave equation, and the boundary conditions are the condition that the stream function on the solid walls of the flow equals zero. The obtained solutions of the wave equation describe the following special cases: Goertler’s vortices between rotating cylinders, secondary flows in a pipe with a square cross section, swirling flow in a round pipe, paired vortex after bend of the pipe. The physical sense of more complex solutions of the wave equation has become clear relatively recently. Very similar structures were found in experimental studies using orthogonal decomposition (POD) of a turbulent pulsations field. This may mean that the eigenfunctions in the POD correspond to coherent structures that really arise in the flow. The results obtained confirm the hypothesis that secondary flows and coherent structures have a common nature. The solutions obtained in this paper can be used in processing the experiment as eigenfunctions for the orthogonal decomposition method. In addition, they can be used in direct numerical simulation (DNS) of turbulent flows

The theoretical investigation here of a three-dimensional array of jets of fluid (air guns) and their interference is motivated by applications to the food sorting industry especially. Three-dimensional motion without symmetry is addressed for arbitrary jet cross-sections and incident velocity profiles. Asymptotic analysis based on the comparatively long axial length scale of the configuration leads to a reduced longitudinal vortex system providing a slender flow model for the complete array response. Analytical and numerical studies, along with comparisons and asymptotic limits or checks, are presented for various cross-sectional shapes of nozzle and velocity inputs. The influences of swirl and of unsteady jets are examined. Substantial cross-flows are found to occur due to the interference. The flow solution is non-periodic in the cross-plane even if the nozzle array itself is periodic. The analysis shows that in general the bulk of the three-dimensional motion can be described simply in a cross-plane problem but the induced flow in the cross-plane is sensitively controlled by edge effects and incident conditions, a feature which applies to any of the array configurations examined. Interference readily alters the cross-flow direction and misdirects the jets. Design considerations centre on target positioning and jet swirling.

The article presents the results of a numerical study of the behavioral characteristics of the process of burning sawdust with a diameter from dmin = 25 μm to dmax = 750 μm in a vortex furnace with counter swirling air flows. The fields of static pressure and absolute velocity in the furnace volume are given. The change in flow density, volume concentration of particles along the height of the furnace is shown. Consumption concentration of particles is 0.094 kg / kg of air. Currently, one of the main directions of Ukraine's strategic development is to achieve energy independence. To achieve this, it is necessary to implement systems for the use of energy resources available in our country. Since a significant part of the country's economic activity is occupied by agricultural activities, the use of low-grade fuels, most of which are waste in this area, is relevant and profitable for economic and environmental reasons. Reconstruction of boilers, improvement of methods and ways of combustion in vortex furnaces of low-grade fuels will significantly reduce the consumption of imported natural gas and bring the country closer to the status of energy-independent state. coke burnout is 100%. The value of the volume concentration of particles β <3 · 10-2 characterizes the aerodynamic mode of motion of particles in the furnace as the mode of gas suspension. In the course of research, the main characteristics of the process of burning sawdust in a vortex furnace with counter-swirling air flows, namely: higher gas velocity is observed in the near-wall area in the lower part of the furnace; when the diameter of the fuel particles increases, the zone with the maximum coke content in them moves from the lower zone of the furnace to the upper; the gas pressure varies slightly both in height and in the cross section of the furnace.

In this paper, we introduce a novel passive control method to mitigate the unsteadiness effects associated to the swirling flows with self-induced instabilities. The control method involves a progressive throttling cross-section flow at the outlet of the conical diffuser. It adjusts the cross-section area with a diaphragm while maintaining all positions of the circular shape centered on the axis. It improves the pressure recovery on the cone wall while the pressure fluctuations associated with the self-induced instability are mitigated as it adjusts the cross-section area. It can adjust the diaphragm in correlation with the operating conditions of the turbine. We investigated the passive control method on a swirl generator, which provides a similar flow as a hydraulic turbine operated at a partial discharge. The plunging and rotating components are discriminated using the pressure fluctuation on the cone wall to provide a clear view of the effects induced by this passive control method. As a result, the novel proof of concept examined in this paper offers valuable benefits as it fulfils a good balance between the dynamical behavior and the hydraulic losses.

The structure of labyrinth cavity flow has been experimentally investigated in a three fin axial turbine labyrinth seal (four cavities). The geometry corresponds to a generic steam turbine rotor shroud. The relative wall motion has not been modeled. The measurements were made with specially developed low-blockage pneumatic probes and extensive wall pressure mapping. Instead of the classical picture of a circumferentially uniform leakage sheet exiting from the last labyrinth clearance, entering the channel, and uniformly spreading over the downstream channel wall, the results reveal uneven flow and the existence of high circumferential velocity within the entire exit cavity. The circumferential momentum is brought into the cavity by swirling fluid from the main channel. This fluid penetrates the cavity and breaks up the leakage sheet into individual jets spaced according to the blade passages. This gives rise to strong local cross flows that may also considerably disturb the performance of a downstream blade row.

The flow and heat transfer characteristics in the corrugated tube mainly depend on flow parameters and geometric configurations of the tube, such as corrugated cross-section, corrugated angle, corrugated arrangement, corrugated pitch and depth, pulsating flow frequency, coolant types, and Reynolds number. This paper presents the pulsating thermal characteristics of ferrofluid flowing in the fluted tube using the de-ionized water and 0.015% by volume as working fluid flowing in the test section. Eulerian two-phase turbulence model validation has been performed in both steady and pulsating flow. The finite volume approach discretizes the Eulerian two-phase model. Numerical results indicate that the longitudinal and transverse secondary flows are induced differently via the pulsating flow. The heat transfer characteristics of pulsating fluid flow are significantly larger than that of continuous fluid flow. A higher pulsating frequency induces a heat transfer enhancement. However, pulsating flow increases pressure due to more flow complexity and rough augmentation. Due to the disturbed fluid flow and higher swirling motion, the heat transfer augmentation increases and corresponds with the published results.

The flow through a smooth axisymmetric constriction (a stenosis in medical applications) of 75% restriction in area is measured using stereoscopic and time-resolved particle image velocimetry (PIV) in the Reynolds number range Re ~ 100–1100. At low Reynolds numbers, steady flow results reveal an asymmetry of the flow downstream of the constriction. The jet emanating from the throat of the nozzle is deflected towards the wall causing the formation of a one-sided recirculation region. The asymmetry results from a Coanda-type wall attachment already observed in symmetric planar sudden expansion flows. When the Reynolds number is increased above the critical value of 400, the separation surface cannot remain attached and an unsteady flow regime begins. Low-frequency axial oscillations of the reattachment point are observed along with a slow swirling motion of the jet. The phenomenon is linked to a periodic discharge of the unstable recirculation region inducing alternating laminar and turbulent flow phases. The resulting flow is highly non-stationary and intermittent. Discrete wavelet transforms are used to discriminate between the large-scale motions of the mean flow and the vortical and turbulent fluctuations. Continuous wavelet transforms reveal the spectral structure of flow disturbances. Temporal measurements of the three velocity components in cross-sections are used with the Taylor hypothesis to qualitatively reconstruct the three-dimensional velocity vector fields, which are validated by comparing with two-dimensional PIV measurements in meridional planes. Visualizations of isosurfaces of the swirling strength criterion allow the identification of the topology of the vortices and highlight the formation and evolution of hairpin-like vortex structures in the flow. Finally, with further increase of the Reynolds number, the flow exhibits less intermittency and becomes stationary for Re ~ 900. Linear stochastic estimation identifies the predominance of vortex rings downstream of the stenosis before breakdown to turbulence.

Currently, there are a lot of applications of vortex technologies. The vortex effect is used in gasdynamic cold generators and vortex cooling chambers. Vortex devices are also used as dehumidifiers, separators, for cooling and heating hydraulic fluids, separating two-phase media, gas mixtures, evacuating, etc. Scientists study the applicability of vortex equipment for traditional and freeze-drying of agricultural products. However, the influence of geometric parameters of vortex devices on the productivity and energy efficiency of temperature separation of gas flows is poorly studied. Research aimed at finding opportunities and expanding the field of application of vortex tubes is an urgent task. The paper describes twodimensional and three-dimensional mathematical models of the swirling gas flow arising in a vortex tube. It presents results of its implementation in the Anсs-Fluent software package. Thermodynamic and hydrodynamic characteristics confirm the effect of temperature separation in a vortex tube. The dependences of temperature separation on the swirl angle and inlet pressure were obtained. For a two-dimensional vortex tube model, calculations were carried out using various turbulence models. The influence of the cross-sectional area at the hot gas flow outlet on temperature separation was studied.

Abstract A study of the aerodynamics and heat transfer of a jet modular recuperator with a change in its geometric characteristics has been carried out. The influence of the in-line and staggered arrangement of the blowing holes, as well as the diameter of the perforated pipe is considered. In all considered variants, the number of holes, their diameter and gas flow rate through the recuperator remained unchanged. Numerical modeling of the problem was carried out in a three-dimensional setting using the ANSYS Fluent 15.0 software package. It was found that with the in-line arrangement of the blowing holes, secondary flows are formed between their longitudinal rows in the form of swirling jets of opposite rotation directed towards the outlet section of the recuperative device, through which the main part of the heated air flows out. With the staggered arrangement of the blowing holes, the formation of spiral vortices is disturbed, the air flow is carried out along the entire cross section of the annular channel, increasing the drift effect of the flow on the impact jets, which leads to a decrease in the intensity of heat transfer and its uniformity along the length of the working surface. An increase in the diameter of the inner perforated pipe leads to a decrease in the drift effect of the cocurrent flow on the jets, an increase in the distribution uniformity of the heat flux along the length of the heat transfer surface, and an increase in the heat transfer coefficient.

This paper reports a detailed investigation of the interaction between a wall-bounded precessing vortex core (PVC) occurring in swirling flows after vortex breakdown and a wall asymmetry. Experiments are carried out in an axisymmetric diffuser downstream of an axial swirl generator inducing a swirling flow with a swirl number of S = 1.1. Wall pressure measurements and two-component particle image velocimetry (PIV) are conducted for Reynolds numbers (Re) ranging from 20 000 to 76 000 in the initial axisymmetric configuration and several asymmetric configurations, with an additional cylindrical protrusion placed on the diffuser wall at different streamwise and circumferential positions. It is first confirmed that synchronous pressure fluctuations at the PVC frequency are only produced in asymmetric configurations. Furthermore, the analysis of the pressure data in several asymmetric configurations revealed for the first time a resonator-like behavior of a wall-bounded PVC. While a change of the protrusion circumferential position in a given cross section of the diffuser only affects the phase of the synchronous pressure fluctuations, the amplitude of the latter features successive minima (pressure node) and maxima (pressure anti-node) as the protrusion is moved along the diffuser in the streamwise direction. In addition, as the protrusion is moved closer to a pressure node, the phase of the synchronous pressure fluctuations exhibits a sudden variation of [Formula: see text]. Similar results are observed for all tested values of Reynolds number, whereas the PVC frequency linearly increases with Re. A reconstruction of the PVC helical structure based on PIV measurements showed that these consecutive pressure nodes are spaced by a distance equal to approximately one third of the PVC helical pitch. Finally, it also revealed that two different states are observed, depending on the position of the protrusion along the diffuser: the synchronous pressure component reaches its maximum value as the PVC center is approaching either its closest or farthest angular position with respect to the protrusion. The transition from one state to another one depends on the streamwise position of the protrusion with respect to the pressure nodes. These unprecedented experimental observations pave the way to novel theoretical developments for a better understanding and modeling of synchronous pressure fluctuations induced by wall-bounded PVC in asymmetric geometries.

The starting point in the formulation of most acoustic problems is the acoustic wave equation. Those most widely used, the classical and convected wave equations, have significant restrictions, i.e., apply only to linear, nondissipative sound waves in a steady homogeneous medium at rest or in uniform motion. There are many practical situations violating these severe restrictions. In the present paper 36 distinct forms of the acoustic wave equation are derived (and numbered W1–W36), extending the classical and convected wave equations to include cases of propagation in inhomogeneous and∕or unsteady media, either at rest or in potential or vortical flows. The cases considered include: (i) linear waves, i.e., with small gradients, which imply small amplitudes, and (ii) nonlinear waves, i.e., with steep gradients, which include “ripples” (large gradients with small amplitude) or large amplitude waves. Only nondissipative waves are considered, i.e., excluding and dissipation by shear and bulk viscosity and thermal conduction. Consideration is given to propagation in homogeneous media and inhomogeneous media, which are homentropic (i.e., have uniform entropy) or isentropic (i.e., entropy is conserved along streamlines), excluding nonisentropic (e.g., dissipative); unsteady media are also considered. The medium may be at rest, in uniform motion, or it may be a nonuniform and∕or unsteady mean flow, including: (i) potential mean flow, of low Mach number (i.e., incompressible mean state) or of high-speed (i.e., inhomogeneous compressible mean flow); (ii) quasi-one-dimensional propagation in ducts of varying cross section, including horns without mean flow and nozzles with low or high Mach number mean flow; or (iii) unidirectional sheared mean flow, in the plane, in space or axisymmetric. Other types of vortical mean flows, e.g., axisymmetric swirling mean flow, possibly combined with shear, are not considered in the present paper (and are left to follow-up work together with dissipative and other cases). The 36 wave equations are derived either by elimination among the general equations of fluid mechanics or from an acoustic variational principle, with both methods being used in a number of cases as cross-checks. Although the 36 forms of the acoustic wave equation do not cover all possible combinations of the three effects of (i) nonlinearity in (ii) inhomogeneous and unsteady and (iii) nonuniformly moving media, they do include each effect in isolation and a variety of combinations of multiple effects. Altogether they provide a useful variety of extensions of the classical (and convected) wave equations, which are used widely in the literature, in spite of being restricted to linear, nondissipative sound waves in an homogeneous steady medium at rest (or in uniform motion). There are many applications for which the classical and convected wave equations are poor approximations, and more general forms of the acoustic wave equation provide more satisfactory models. Numerous examples of these applications are given at the end of each written section. There are 240 references cited in this review article.

We report the detailed multi-scale and multi-directional geometric study of both evolving Lagrangian and instantaneous Eulerian structures in turbulent channel flow at low and moderate Reynolds numbers. The Lagrangian structures (material surfaces) are obtained by tracking the Lagrangian scalar field, and Eulerian structures are extracted from the swirling strength field at a time instant. The multi-scale and multi-directional geometric analysis, based on the mirror-extended curvelet transform, is developed to quantify the geometry, including the averaged inclination and sweep angles, of both structures at up to eight scales ranging from the half-height δ of the channel to several viscous length scales δν. Here, the inclination angle is on the plane of the streamwise and wall-normal directions, and the sweep angle is on the plane of streamwise and spanwise directions. The results show that coherent quasi-streamwise structures in the near-wall region are composed of inclined objects with averaged inclination angle 35°–45°, averaged sweep angle 30°–40° and characteristic scale 20δν, and ‘curved legs’ with averaged inclination angle 20°–30°, averaged sweep angle 15°–30° and length scale 5δν–10δν. The temporal evolution of Lagrangian structures shows increasing inclination and sweep angles with time, which may correspond to the lifting process of near-wall quasi-streamwise vortices. The large-scale structures that appear to be composed of a number of individual small-scale objects are detected using cross-correlations between Eulerian structures with large and small scales. These packets are located at the near-wall region with the typical height 0.25δ and may extend over 10δ in the streamwise direction in moderate-Reynolds-number, long channel flows. In addition, the effects of the Reynolds number and comparisons between Lagrangian and Eulerian structures are discussed.

Steady axially invariant (fully developed) incompressible laminar flow of a Newtonian fluid in helical pipes of constant circular cross-section with arbitrary pitch and arbitrary radius of coil is studied. A loose-coiling analysis leads to two dominant parameters, namely Dean number, Dn = Reλ½, and Germano number, Gn = Reη, where Re is the Reynolds number, λ is the normalized curvature ratio and η is the normalized torsion. The Germano number is embedded in the body-centred azimuthal velocity which appears as a group in the governing equations. When studying Gn effects on the helical flow in terms of the secondary flow pattern or the secondary flow structure viewed in the generic (non-orthogonal) coordinate system of large Dn, a third dimensionless group emerges, γ = η/(λDn)½. For Dn < 20, the group γ* = Gn Dn-2 = η/(λRe) takes the place of γ.Numerical simulations with the full Navier-Stokes equations confirmed the theoretical findings. It is revealed that the effect of torsion on the helical flow can be neglected when γ ≤ 0.01 for moderate Dn. The critical value for which the secondary flow pattern changes from two vortices to one vortex is γ* > 0.039 for Dn < 20 and γ > 0.2 for Dn ≥ 20. For flows with fixed high Dean number and A, increasing the torsion has the effect of changing the relative position of the secondary flow vortices and the eventual formation of a flow having a Poiseuille-type axial velocity with a superimposed swirling flow. In the orthogonal coordinate system, however, the secondary flow generally has two vortices with sources and sinks. In the small-γ limit or when Dn is very small, the secondary flow is of the usual two-vortex type when viewed in the orthogonal coordinate system. In the large-γ limit, the appearance of the secondary flow in the orthogonal coordinate system is also two-vortex like but its orientation is inclined towards the upper wall. The flow friction factor is correlated to account for Dn, A and γ effects for Dn ≤ 5000 and γ < 0.1.

Global absolute and convective stability analysis of flow past a circular cylinder with symmetry conditions imposed along the centreline of the flow field is carried out. A stabilized finite element formulation is used to solve the eigenvalue problem resulting from the linearized perturbation equation. All the computations carried out are in two dimensions. It is found that, compared to the unrestricted flow, the symmetry conditions lead to a significant delay in the onset of absolute as well as convective instability. In addition, the onset of absolute instability is greatly affected by the location of the lateral boundaries and shows a non-monotonic variation. Unlike the unrestricted flow, which is associated with von Kármán vortex shedding, the flow with centreline symmetry becomes unstable via modes that are associated with low-frequency large-scale structures. These lead to expansion and contraction of the wake bubble and are similar in characteristics to the low-frequency oscillations reported earlier in the literature. A global linear convective stability analysis is utilized to find the most unstable modes for different speeds of the disturbance. Three kinds of convectively unstable modes are identified. The ones travelling at very low streamwise speed are associated with large-scale structures and relatively low frequency. Shear layer instability, with relatively smaller scale flow structures and higher frequency, is encountered for disturbances travelling at relatively larger speed. For low blockage a new type of instability is found. It travels at relatively high speed and resembles a swirling flow structure. As opposed to the absolute instability, the convective instability appears at much lower Re and its onset is affected very little by the location of the lateral boundaries. Analysis is also carried out for determining the convective stability of disturbances that travel in directions other than along the free stream. It is found that the most unstable disturbances are not necessarily the purely streamwise travelling ones. Disturbances that move purely in the cross-stream direction can also be convectively unstable. The results from the linear stability analysis are confirmed by carrying out direct time integration of the linearized disturbance equations. The disturbance field shows transient growth by several orders of magnitude confirming that such flows act as amplifiers. Direct time integration of the Navier–Stokes equation is carried out to track the time evolution of both the large-scale low-frequency oscillations and small-scale shear layer instabilities. The critical Re for the onset of convective instability is compared with earlier results from local analysis. Good agreement is found.

We have conducted two-dimensional computations of vortex-induced vibration of an elastically mounted circular cylinder colliding with a rigid wall at a Reynolds number of 300. For wide ranges of reduced velocities, we have identified C (chaotic), P (periodic), and QP (quasi-periodic) vortex shedding modes at two gap and mass ratios. The deflected gap flow induced by the wall shear layer during the descending motion of the cylinder cause stretching of the vortex strands, while both the P and QP modes show the “S”-type shedding signature. The pathlines for the C-mode yield unstable hyperbolic behavior, whereas twisted knots and spirals are seen for the P-mode. Criss-cross interactions with the swirling pathlines are observed in the QP-mode.

The present study numerically investigates the influence of introducing a spin-type mixer and different angular orientations of the mixer blades on the spray-wall interaction and mixing, following cross-stream injection of a pulsed spray into airflow in a circular duct. This is relevant to the Selective Catalytic Reduction system in diesel engines for exhaust gas after-treatment. The spin-type static mixer is located downstream of the injector and generates a swirling airflow in the duct. All simulations were carried out using ANSYS Fluent V18.0. The standard k– ω model is used to simulate the turbulent continuous phase flow, while the discrete phase model is employed to track the spray droplets. The Taylor Analogy Breakup and Kuhnke wall film models are adopted to model droplet breakup and wall-film formation, respectively. First, the swirling airflow characteristics without spray injection are validated against in-house particle image velocimetry measurements. Second, the spray computations are compared with the experiment. Overall, good agreement between simulation and experiment is achieved. Furthermore, the choice of water and urea water solution injection liquid on the in-channel spray characteristics is also studied. The main focus of the present work is on the study of the influence of spin mixer clocking on the post-impingement spray evolution, droplet redistribution and mixing, and wall-film characteristics. The results show that the choice of the angular orientation of the mixer governs the extent of droplet deposition and splashing on the mixer blades and, as a result, strongly influences the spatial uniformity of droplets and ammonia species at the channel exit.

Abstract Countercurrent–cocurrent dissolved air flotation (CCDAF), the popular water purification device, which consists of collision and adhesion contact zones, showed favorable flotation conditions for micro-bubble adhesion and stability. In this study, computational fluid dynamics (CFD) numerical simulation was employed to confirm that the unique CCDAF configuration create reasonable and that the flow field characteristics were good no matter for single phase or gas–liquid two-phase conditions. In addition, the turbulence of the flow field was enhanced with the increasing influent load; the swirling was remarkably reduced with the increase of gas holdup. Meanwhile, a thick micro-bubble filter layer was formed in the separation zone, which favored bubble-flocs agglomerating and rising. The force analysis also showed that the cross section within the tank contribute to the uniformity of the bottom water collection as well as enlargement of the bottom outflow area, therefore improving the overall flotation performance. The simulation results revealed for the CCDAF process can provide technical guidance for engineering design and application.

The present work aims to investigate the behavior of drying kaffir lime leaves in a swirling solar drying chamber (S-SDC) fitted with an inclined slotted angle air distributor. A distributor plated with inclined slotted angle was located at the air inlet at the bottom of the chamber. Experimental and numerical methods have been applied to analyze the efficiency of developed S-SDC assisted solar drying system based on the moisture content (MC), moisture content ratio (MR) and drying rate (DR) were examined. The experimental results showed that the S-SDC can reduce the moisture content of kaffir lime leaves more rapidly than a conventional solar drying chamber (CSDC). The S-SDC gave a higher DR and decreased drying time compared to that of C-SDC. The results also indicated that operation at higher air velocities resulted in a greater DR, especially at the beginning stage of the drying process. For the S-SDC, the reduced of MC, MR and DR at a high air velocity (v = 2.0 m/s) was better than at low air velocities (v = 0.5 and 1.0 m/s). Drying chamber efficiency is also observed at a higher air velocity of 2 m/s for both SSDC and CSDC. In addition, obtained experimental findings are in line with numerical results. The outcomes of this study present the potential of using the S-SDC compared to the C-SDC to be used in drying crops.

A frequently employed method for aerodynamic flame stabilization in modern premixed low emission combustors is the breakdown of swirling flows; with carefully optimized tailoring of the swirler, a sudden transition in the flow field in the combustor can be achieved. A central recirculation zone evolves at the cross-sectional area change located at the entrance of the combustion chamber and anchors the flame in a fixed position. In general, premixed combustion in swirling flows can lead to flame flashback that is caused by combustion induced vortex breakdown near the centerline of the flow. In this case, the recirculation zone suddenly moves upstream and stabilizes in the premix zone (Kröner , 2007, “Flame Propagation in Swirling Flows—Effect of Local Extinction on the Combustion Induced Vortex Breakdown,” Combust. Sci. Technol., 179, pp. 1385–1416). This type of flame flashback is caused by a strong interaction between the flame chemistry and vortex dynamics. The analysis of the vorticity transport equation shows that the axial gradient of the azimuthal vorticity is of particular importance for flame stability. A negative azimuthal vorticity gradient decelerates the core flow and finally causes vortex breakdown. Based on fundamental fluid mechanics, guidelines for a proper aerodynamic design of gas turbine combustors are given. These guidelines summarize the experience from several previous aerodynamic and combustion studies of the authors.

Abstract This paper presents the experimental analysis of the impact of swirl number of cross-flowing air stream on liquid jet spray trajectory at a fixed air flow velocity of 42 m/s with the corresponding Mach number of 0.12. The experiments were conducted for 4 different swirl numbers (0, 0.2, 0.42 and 0.73) using swirl vanes at air inlet having angles of 0°, 15°, 30° and 45° respectively. Liquid to air momentum flux ratio (q) was varied from 5 to 25. High speed (@ 500 fps) images of the spray were captured and those images were processed using MATLAB to obtain the path of the spray at various momentum flux ratios. The results show interesting trends for the spray trajectory and the jet spread in swirling air flow. High swirling flows not only lead to spray with lower radial penetration due to sharp bending and disintegration of liquid jet, but also result in spray with high jet spread and spray area. Based on the results, correlations for the spray path have been proposed which incorporates the effects of the swirl number of the air flow.

By generating helical swirling motion inside a tube with a twisted-tape insert, forced convective heat transfer is significantly enhanced. The primary mechanism entails imparting a centrifugal force component to the longitudinal fluid motion, which superimposes secondary circulation over the main axial flow to promote cross-stream mixing. Based on experimental flow visualization and computational modeling of single-phase laminar flows, a fundamental scaling of the cross-sectional vortex structure and a parametric analysis of the primary enhancement mechanisms in single-phase flows are delineated. Heat transfer coefficient and friction factor correlations for both laminar and turbulent regimes are presented, and the damping effect of swirl on the transition region is highlighted. In flow boiling with net vapor generation, tape-twist-induced helical swirl pushes liquid droplets from the core to the wall to enhance heat transfer and delay dryout. In subcooled boiling, the radial pressure gradient due to the swirl promotes vapor removal from the heated surface to retard vapor blanketing and accommodate higher heat fluxes. The scaling and phenomenological descriptions of the underlying vapor-liquid transport in these different boiling modes and regimes are presented along with any available predictive correlations.

Flow data are often decomposed using proper orthogonal decomposition (POD) of the space–time separated form, $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (t\right )\boldsymbol {\phi }_j\left (\boldsymbol {x}\right )$ , which targets spatially correlated flow structures in an optimal manner. This paper analyses permuted POD (PPOD), which decomposes data as $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (\boldsymbol {n}\right )\boldsymbol {\phi }_j\left (s,t\right )$ , where $\boldsymbol {x}=(s,\boldsymbol {n})$ is a general spatial coordinate system, $s$ is the coordinate along the bulk advection direction and $\boldsymbol {n}=(n_1,n_2)$ are along mutually orthogonal directions normal to the advection characteristic. This separation of variables is associated with a fundamentally different inner product space for which PPOD is optimal and targets correlations in $s,t$ space. This paper presents mathematical features of PPOD, followed by analysis of three experimental datasets from high-Reynolds-number, turbulent shear flows: a wake, a swirling annular jet and a jet in cross-flow. In the wake and swirling jet cases, the leading PPOD and space-only POD modes focus on similar features but differ in convergence rates and fidelity in capturing spatial and temporal information. In contrast, the leading PPOD and space-only POD modes for the jet in cross-flow capture completely different features – advecting shear layer structures and flapping of the jet column, respectively. This example demonstrates how the different inner product spaces, which order the PPOD and space-only POD modes according to different measures of variance, provide unique ‘lenses’ into features of advection-dominated flows, allowing complementary insights.

Abstract The swirling secondary flow in curved pipes is studied in three-space dimensions using a weakly compressible smoothed particle hydrodynamics (WCSPH) formulation coupled to new nonreflecting outflow boundary conditions. A large eddy simulation (LES) model for turbulence is benchmarked with existing experimental data. After validation of the present model against experimental results for a 90 deg pipe bend, a detailed numerical study aimed at reproducing experimental flow measurements for a wide range of Reynolds numbers has been performed for different pipe geometries, including U pipe bends, S-shaped pipes, and helically coiled pipes. In all cases, the SPH calculated behavior shows reasonably good agreement with the measurements across and downstream the bend in terms of streamwise velocity profiles and cross-sectional contours. Maximum mean-root-square deviations from the experimentally obtained profiles are always less than ∼1.8%. This combined with the very good matching between the SPH and the experimental cross-sectional contours shows the uprising capabilities of the present scheme for handling engineering applications with streamline curvature, such as flows in bends and manifolds.

Abstract Particulate deposition effects on flow and heat transfer in an internal swirl tube subjected to fly ash ingestion were investigated by constructing an unsteady simulation framework, in which a particle-wall interaction model and a mesh morphing technique were implemented. Swirling flows in the swirl tube were induced by two tangential jet nozzles. Particles having a mean diameter of 6.5 micron were released from the nozzle inlets to model an exposure duration of 4,500 hours for engine operation in real fly ash environment using scale factors in the unsteady simulations. Particle deposition and its dynamic process were examined and the effects of deposition on the swirling flow were quantified by comparing time-averaged flow fields and heat transfer with those from a clean tube. Results reveal that the most upstream section of the swirl tube captures the majority of the particles and the deposition distributions show a spiral pattern over the tube wall. The deposition can generate a maximum of 15% reduction in cross-sectional area of the tube within the exposure duration, resulting in a reduced swirl number and further lower heat transfer in the downstream section of the tube relative to the clean tube case. However, as the heat transfer in the upstream deposition section is enhanced by the roughness deposition, area-averaged heat transfer throughout the entire swirl tube is slightly improved by 4.0% but simultaneously a 179% higher pressure loss is observed, leading to an overall thermal performance value of 0.79.

The present paper simplifies the naturally formed dunes (riverbeds) as large-scale three-dimensional staggered wavy walls to investigate the features of the accompanying secondary flows and streamwise vortices via large-eddy simulation. A comparison between the swirling strength and the mean velocities suggests where a secondary flow induces upwash or downwash motions. Moreover, we propose a pseudo-convex wall mechanism to interpret the directionality of the secondary flow. The centrifugal instability criterion is then used to reveal the generation of the streamwise vortices. Based on these analytical results, we found that the streamwise vortices are generated in the separation and reattachment points on both characteristic longitudinal–vertical and horizontal cross-sections, which is related to the curvature effect of the turbulent shear layer. Furthermore, the maximum Görtler number characterized by the ratio of centrifugal to viscous effects suggests that, for fixed ratio of spanwise- to streamwise-wavelength cases, the strongest centrifugal instability occurring on the longitudinal–vertical cross-section gradually dominates with the increases in amplitude. A similar trend for the cases with varied spanwise wavelength can also be found. It is also found that the streamwise vortices are generated more readily via transverse flow around the crest near the separation and reattachment points when the ratio of spanwise- to streamwise-wavelength equals 1.

A full-scale Francis turbine has been experimentally investigated over its full range of operation to detect draft tube swirling flows and cavitation. The unit is of interest due to the presence of severe pressure fluctuations at part load and of advanced blade suction-side cavitation erosion. Moreover, the turbine has a particular combination of guide vanes (20) to runner blades (15) that makes it prone to significant rotor-stator interaction (RSI). For that, a complete measurement system of dynamic pressures, temperatures, vibrations, and acoustic emissions has been setup with the corresponding transducers mounted at selected sensitive locations. The experiments have comprised an efficiency measurement, a signal transmissibility evaluation, and the recording of the raw signals at high sampling rates. Signal processing methods for demodulation, peak power estimation, and cross correlation have also been applied. As a result, draft tube pressure fluctuations have been detected around the Rheingans frequency for low loads and at 4% of the rotating frequency for high loads. Moreover, maximum turbine guide bearing acoustic emissions have been measured at full load with amplitude modulations at both the guide vane passing frequency and the draft tube surge frequency.

Abstract This study features a rotating, blade-shaped, two-pass cooling channel with a variable aspect ratio. The effect of passage orientation on the heat transfer and pressure loss is investigated by comparing to a planar channel design with a similar geometry. The first pass of the channel is angled at 50-deg from the direction of rotation while the second pass has an orientation angle of 105-deg. The coolant flows radially outward in the first passage with an aspect ratio (AR) = 4:1 and radially inward in the second passage with AR = 2:1. In addition to the smooth surface case, 45-deg angled ribs with a profiled cross section are also placed on the leading and trailing surfaces in both the passages. The ribs are placed such that P/e = 10 and e/H= 0.16. The Reynolds number varies from 10,000 to 45,000 in the first passage and 16,000 to 73,000 in the second passage. The maximum rotation numbers are 0.38 and 0.15 in the first and second passes, respectively. In the second passage, the heat transfer on the outer wall and trailing surface is higher due to flow impingement and the swirling motion induced by the blade-shaped tip turn. The overall heat transfer and pressure loss are higher than the planar geometry due to the blade-shaped feature. The heat transfer and pressure loss characteristics from this study provide important information for the gas turbine blade internal cooling designs.

AbstractThe gas distribution in the shaft is of key importance for the performance of the blast furnace process, since it affects the way in which the burden is heated and reduced, and also the pressure drop in the shaft and cohesive zone. Traditionally, the gas distribution is followed by gas temperature measurements at several points over the radius or diagonal by the above-burden probes, but novel acoustic techniques can estimate the gas temperature over the full cross section of the throat. A fundamental problem is that the gas is redistributed in the upper bed and above it, so the measured profile may no longer reflect the conditions in the shaft. This paper studies the gas redistribution by a CFD model of the throat region, neglecting heat transfer to the bed and walls. It is demonstrated that strong redistribution and downward-swirling flows may occur, which affect the measurements. The arising conditions under different assumptions of the bed state are studied, and the dynamics of the changes are also briefly analyzed. A comparison of the findings of the computational model with acoustic measurements of the gas temperatures in the throat of two industrial blast furnaces reveals a good resemblance. The results of the study sheds light on the complex flow conditions of the gas in the blast furnace throat region and can be used to interpret information from measuring devices and to study how their positioning affects the measurements.

Whatever a work of art may be, the artist certainly cannot dare to be simple. (Rebecca West) Van Gogh's Sunflowers is [not] considered worthy of inclusion in a new selection of the world's finest art. The compilers of the Folio Society's lavish and expensive Book of the 100 Greatest Paintings believe that some works are so overexposed and have been reproduced so often that they can no longer be viewed with a fresh eye. The Independent, 24.8.2001. Sometimes the day just falls down on you. One day they'll measure the weight of a day. One day science will be able to measure the density of 24 hours. And then I can claim the burden of getting through a day as part of my fitness programme. She imagined filling in her exercise diary. Lifted three fallen days from shoulders. Pumped up biceps, triceps, amassed muscle gain in legs. Strengthened heart tissue. Deepened lung capacity. She shouldn't joke about it. But of course she did. Sometimes it was how she coped. She'd tried not joking, joking, paying attention, ignoring, running away from, facing head on, talking, not talking, sharing, selfishly selflessly, hopefully hopelessly, alone and in company. Of course some methods of dealing with it were more fun than others. She used to have sex a lot when she felt most depressed. What she'd liked most about the sex was the feeling of being what she called underneath, somewhere darker, more primal. Crawling around on the inside of things. That was how she eventually looked at it. As if it was a special sort of art she had created, woven through the threads of her brain cells and tendrils of her nerve endings. Sometimes profoundly scary, sometimes just a cheap thrill. Why can't you just be happy? she'd heard people ask. People who cared and those who didn't particularly. As if she had willed it upon herself and could just as easily will herself out of it. I choose. Or I do not choose, she might say. Either way it remains because I have understood it ultimately is not a matter of choice. I will be happy when happiness comes around again. Just the same as the sunshine comes out after the rain clouds disappear. It is a cycle and I am part of its nature. And I haven't yet learnt to control the weather. Of course shamans could do it. Certain sorts of yogis. Witches. Tap into energy flows and seismic quivers. Even then it was not a matter of controlling shifts in temperature but rather surrendering to it. Making them not just observers of natural phenomena. But participants. Adding their own energy to the natural energy. Bringing about change through focus and attention rather than resistance and will. It would be hard to stay that sensitive in the city. Too hard with all the relentless metal, the swabs of smoke and smog blinding the eyes, the clang and grrrs of the smashing traffic, all the urban thoughts circling your brain like gangs out for some kicks. She made herself scarce when the days fell like this one. Right on top of her like a mountain of collapsing ash. Even though the others had what always seemed a grudging respect for it. As if she limped. Or was blind in one eye. They sensed its genetic implications. And almost admired the way she wore it like a piece of dark, sombre clothing. Instead of letting it wear her. Still These dark days. These black moods. Like a monstrous pet She had to walk Endlessly through the city streets Until it had walked off Its rage. She closed her eyes. Somewhere in the distance she could faintly detect the scent of a certain sort of coffee, which she craved. She opened her eyes and headed up King St, peering into cafes as she passed, twitching her nostrils like a sniffer dog, nosing out the secret stash of illicit nectar that would, of course, be the momentary answer to all her problems. She walked past Café Bleu. Too stark, too gloomy. Past El Bache. Too fluorescent, too sugary. Straight past CITRUS. Too friendly, too trendy. Criss-crossed King St to Macro Whole Foods. Too positive, too pure. Back over the other side to the Marleborough Hotel. Oh no, too desperate before midday. Turned left, walked down past the hospital, briefly thought about their cafeteria. But no, way too hopeless and pessimistic. Back onto City Road, past the Uni. Way too cool and know it all. Across Broadway, past IKU. Same problem as Macro, and almost up to Badde Manors. Eek! Way, way too hip. She got herself back down almost to Paramatta Road and stopped. She briefly wondered whether she should go back to Essential Energies and see the Clairvoyant. But she was sick at the idea of handing over forty bucks for someone to tell her that everything, even depression, eventually had to pass. She may as well go up to a complete stranger on the street and ask them: Tell me what to do, please tell me what to do. In certain cultures she was sure this would work. Older, more spiritual ethnicities, which had long ago given up the idea that human beings could control everything that happened in life. They'd even laugh at the concept. They might say something ancient and wise and comforting. Something about death and rebirth and transformation and illness being a sign of health and everything the other way round. But here, pioneer's children, building, growing, planning, committing, grasping, holding on, they'd tell her to pull herself together and get on with it. If you'd just tell me what IT was, maybe I'd be able to get on with it. She might answer them if she was in the mood for a conversation. But of course she wasn't going to accost anyone. Not today. Not in Glebe. Not just down the road from Gleebooks. Too literary, too secure. She bought some Turkish bread from the Lebanese place next door, intending to feed the ducks in City Park, but slipped back inside Essential Energies, with the bread tucked under her arm, just to stand for a few moments near the oil burner. The scents were Orange, Marjoram and Lavender, a soothing combination, the sign said, to calm the troubled mind and open the third eye. Jesus, she thought to herself, suddenly laughing out loud, on days like this I'm lucky if I can keep one good eye open. Let alone two. Without realizing it, she'd been making a racket. Aware of the shop assistant staring disapprovingly at her, she backed out the door, chattering to herself like a madwoman, fleetingly remembering how being in a church always seemed to create the same sense of misadventure as being in a New Age Shop. Too clean, too quiet, too affluent, too aromatic. Back on Paramatta Road she felt like crying. Some days that was all she felt like doing, tears gathering inside her, not like great thunderstorms about to explode, but grey sheets of drizzle with their slow, maddening incessant drip drip drip on the brain. She remembered Emerald Green telling her that depression would be the Super Disease of the Millennium. Sometimes she wondered how she would last that long. If you chart your course through it, you'll mark the map for others, Emerald had told her. Maybe the true pioneers of tomorrow are those with the courage to go out alone into the most forbidding terrain and return intact. It sounded encouraging when Emerald said it, but it never helped when she was standing at crossroads such as these wondering which way to go. Walk down Broadway into Chinatown. Wolf down a Laksa for lunch. Burn her mouth and body back to life. Halfway down Broadway she stopped as she always did, at the Broadway Framers. They'd taken down the Whitely that had been in the window for ages, and replaced it with the usual assortment of famous and popular prints, framed unnecessarily, she'd always thought, in ostentatious gold. Matisse's Blue Nude, Picasso's Harlequin from his Rose period and Van Gogh's Sunflowers. When she was younger and more easily impressed, her post modernist friends had told her painting was dead and that figurative art was bogus. They seemed so sure of everything, she'd never been sure of anything and so she'd been almost ashamed to admit that one of her favourite pictures was Sunflowers. She'd never analyzed why she liked it. If pressed to give an intelligent answer it would have been something along the lines of the visceral textures of the flowers, still so apparently immediate even in the hundreds of flat prints that had crowded the waiting rooms of her life since she was a little girl. It would have had something to do with the extravagance with which the stems were stuffed into the case, the overloaded slightly bedraggled, lushness of nature crammed by the artist into the humble little pot on which he'd scrawled his name. It could have been the energy of the brush strokes, which seem to thrust the flowers towards you with such force, as if Vincent is saying to you personally: LOOK LOOK. Have you ever seen anything so beautiful? He was just doing his job, Painter Bob had said, the job that artists do. To make us look at things that mostly we're too distracted, too busy, too depressed to see. The stars in the sky at night. Swirling clouds. The sloping downwards of a face and all the stories which that particular angle tells. She thought of Van Gogh whenever she saw that picture. On his lonely road to pure painting, too crazy, to stubborn to do anything else. Painter Bob had said he'd been a shaman, a channel through which his subjects passed in order to be delivered onto paper so that … we, the rest of the world, us, the rest of history, decade after decade of casual and not so casual observers of art, could see, feel, absorb through the nerve endings in our eyes the essence of what is was, not just to see the sunflowers but to be the sunflowers. Yellow, she thought. And amber. Orange. Bits of gold. They've always made me feel so happy. It couldn't be that simple, she thought. To have the courage to cross the gap that separates the subject from the object. To become the thing which you see. To empathize. To inhabit. To break down the disconnection between matter. Plump, healthy flowers, slightly past their prime. Still, she thought, they'd cost a packet at the florists. She liked sunflowers. Despite their larger than life, exotic qualities they'd always seemed to her to be completely and utterly ordinary. ..in the end only someone who suffered deeply could see the radiance in such simple things Painter Bob was right. He was after all an expert in such things. Sometimes she felt as if she didn't know much about anything at all. Here she was looking at reproductions through plate glass windows, while above her the sun was almost coming out. Feeling hopeful, she put on her sunglasses. Citation reference for this article MLA Style Neil, Linda. "Sunflowers " M/C: A Journal of Media and Culture 5.2 (2002). [your date of access] < http://www.media-culture.org.au/0205/sunflower.php>. Chicago Style Neil, Linda, "Sunflowers " M/C: A Journal of Media and Culture 5, no. 2 (2002), < http://www.media-culture.org.au/0205/sunflower.php> ([your date of access]). APA Style Neil, Linda. (2002) Sunflowers . M/C: A Journal of Media and Culture 5(2). < http://www.media-culture.org.au/0205/sunflower.php> ([your date of access]).

IntroductionAustralia is at a particular point in its history where there is a noticeable diaspora of artists and creative practitioners away from the major capitals of Sydney and Melbourne (in particular), driven in no small part by ballooning house prices of the last eight years. This has meant big changes for some regional spaces, and in turn, for the face of Australian cultural life. Regional cultural precincts are forming with tourist flows, funding attention and cultural economies. Likewise, there appears to be growing consciousness in the ‘art centres’ of Melbourne and Sydney of interesting and relevant activities outside their limits. This research draws on my experience as an art practitioner, curator and social researcher in one such region (Castlemaine in Central Victoria), and particularly from a recent interview series I have conducted in collaboration with art space in that region, Wide Open Road Art. In this, 23 regional and city-based artists were asked about the social, economic and local conditions that can and have supported their art practices. Drawing from these conversations and Bourdieu’s ideas around cultural production, the article suggests that authentic, diverse, interesting and disruptive creative practices in Australian cultural life involve the increasingly pressing need for security while existing outside the modern imperative of high consumption; of finding alternative ways to live well while entering into the shared space of cultural production. Indeed, it is argued that often it is the capacity to defy key economic paradigms, for example of ‘rational (economic) self-interest’, that allows creative life to flourish (Bourdieu Field; Ley “Artists”). While regional spaces present new opportunities for this, there are pitfalls and nuances worth exploring.Changes in Regional AustraliaAustralia has long been an urbanising nation. Since Federation our cities have increased from a third to now constituting two-thirds of the country’s total population (Gray and Lawrence 6; ABS), making us one of the most urbanised countries in the world. Indeed, as machines replaced manual labour on farms; as Australia’s manufacturing industry began its decline; and as young people in particular left the country for city universities (Gray and Lawrence), the post-war industrial-economic boom drove this widespread demographic and economic shift. In the 1980s closures of regional town facilities like banks, schools and hospitals propelled widespread belief that regional Australia was in crisis and would be increasingly difficult to sustain (Rentschler, Bridson, and Evans; Gray and Lawrence 2; Barr et al.; ABS). However, the late 1990s and early 21st century saw a turnaround that has been referred to by some as the rise of the ‘sea change’. That is, widespread renewed interest and idealisation of not just coastal areas but anywhere outside the city (Murphy). It was a simultaneous pursuit of “a small ‘a’ alternative lifestyle” and escape from rising living costs in urban areas, especially for the unemployed, single parents and those with disabilities (Murphy). This renewed interest has been sustained. The latest wave, or series of waves, have coincided with the post-GFC house price spike, of cheap credit and lenient lending designed to stimulate the economy. This initiative in part led to Sydney and Melbourne median dwelling prices rising by up to 114% in eight years (Scutt 2017), which alone had a huge influence on who was able to afford to live in city areas and who was not. Rapid population increases and diminished social networks and familial support are also considered drivers that sent a wave of people (a million since 2011) towards the outer fringes of the cities and to ‘commuter belt’ country towns (Docherty; Murphy). While the underprivileged are clearly most disadvantaged in what has actually been a global development process (see Jayne on this, and on the city as a consumer itself), artists and creatives are also a unique category who haven’t fared well with hyper-urbanisation (Ley “Artists”). Despite the class privilege that often accompanies such a career choice, the economic disadvantage art professions often involve has seen a diaspora of artists moving to regional areas, particularly those in the hinterlands around and train lines to major centres. We see the recent ‘rise of a regional bohemia’ (Regional Australia Institute): towns like Toowoomba, Byron Bay, Surf Coast, Gold Coast-Tweed, Kangaroo Valley, Wollongong, Warburton, Bendigo, Tooyday, New Norfolk, and countless more being re-identified as arts towns and precincts. In Australia in 2016–17, 1 in 6 professional artists, and 1 in 4 visual artists, were living in a regional town (Throsby and Petetskaya). Creative arts in regional Australia makes up a quarter of the nation’s creative output and is a $2.8 billion industry; and our regions particularly draw in creative practitioners in their prime productive years (aged 24 to 44) (Regional Australia Institute).WORA Conservation SeriesIn 2018 artist and curator Helen Mathwin and myself received a local shire grant to record a conversation series with 23 artists who were based in the Central Goldfields region of Victoria as well as further afield, but who had a connection to the regional arts space we run, WideOpenRoadArt (WORA). In videoed, in-depth, approximately hour-long, semi-structured interviews conducted throughout 2018, we spoke to artists (16 women and 7 men) about the relocation phenomenon we were witnessing in our own growing arts town. Most were interviewed in WORA’s roving art float, but we seized any ad hoc opportunity we had to have genuine discussions with people. Focal points were around sustainability of practice and the social conditions that supported artists’ professional pursuits. This included accessing an arts community, circles of cultural production, and the ‘art centre’; the capacity to exhibit; but also, social factors such as affordable housing and the ability to live on a low-income while having dependants; and so on. The conversations were rich with lived experiences and insights on these issues.Financial ImperativesIn line with the discussion above, the most prominent factor we noticed in the interviews was the inescapable importance of being able to live cheaply. The consistent message that all of the interviewees, both regional- and city-based, conveyed was that a career in art-making required an important independence from the need to earn a substantial income. One interviewee commented: “I do run my art as a business, I have an ABN […] it makes a healthy loss! I don’t think I’ve ever made a profit […].” Another put it: “now that I’m in [this] town and I have a house and stuff I do feel like there is maybe a bit more security around those daily things that will hopefully give me space to [make artworks].”Much has been said on the pervasive inability to monetise art careers, notably Bourdieu’s observations that art exists on an interdependent field of cultural capital, determining for itself an autonomous conception of value separate to economics (Bourdieu, Field 39). This is somewhat similar to the idea of art as a sacred phenomenon irreducible to dollar terms (Abbing 38; see also Benjamin’s “aura”; “The Work of Art”). Art’s difficult relationship with commodification is part of its heroism that Benjamin described (Benjamin Charles Baudelaire 79), its potential to sanctify mainstream society by staying separate to the lowly aspirations of commerce (Ley “Artists” 2529). However, it is understood, artists still need to attain professional education and capacities, yet they remain at the bottom of the income ladder not only professionally, but in the case of visual artists, they remain at the bottom of the creative income hierarchies as well. Further to this, within visual arts, only a tiny proportion achieve financially backed success (Menger 277). “Artistic labour markets are characterised by high risk of failure, excess supply of recruits, low artistic income level, skewed income distribution and multiple jobholding” (Mangset, Torvik Heian, Kleppe, and Løyland; Menger). Mangset et al. point to ideas that have long surrounded the “charismatic artist myth,” of a quasi-metaphysical calling to be an artist that can lead one to overlook the profession’s vast pitfalls in terms of economic sustainability. One interviewee described it as follows: “From a very young age I wanted to be an artist […] so there’s never been a time that I’ve thought that’s not what I’m doing.” A 1% rule seems widely acknowledged in how the profession manages the financial winners against those who miss out; the tiny proportion of megastar artists versus a vast struggling remainder.As even successful artists often dip below the poverty line between paid engagements, housing costs can make the difference between being able to live in an area and not (Turnbull and Whitford). One artist described:[the reason we moved here from Melbourne] was financial, yes definitely. We wouldn’t have been able to purchase a property […] in Melbourne, we would not have been able to live in place that we wanted to live, and to do what we wanted to do […]. It was never an option for us to get a big mortgage.Another said:It partly came about as a financial practicality to move out here. My partner […] wanted to be in the bush, but I was resistant at first, we were in Melbourne but we just couldn’t afford Melbourne in the end, we had an apartment, we had a studio. My partner was a cabinet maker then. You know, just every month all our money went to rent and we just couldn’t manage anymore. So we thought, well maybe if we come out to the bush […] It was just by a happy accident that we found a property […] that we could afford, that was off-grid so it cut the bills down for us [...] that had a little studio and already had a little cottage on there that we could rent that out to get money.For a prominent artist we spoke to this issue was starkly reflected. Despite large exhibitions at some of the highest profile galleries in regional Victoria, the commissions offered for these shows were so insubstantial that the artist and their family had to take on staggering sums of personal debt to execute the ambitious and critically acclaimed shows. Another very successful artist we interviewed who had shown widely at ‘A-list’ international arts institutions and received several substantial grants, spoke of their dismay and pessimism at the idea of financial survival. For all artists we spoke to, pursuing their arts practice was in constant tension with economic imperatives, and their lives had all been shaped by the need to make shrewd decisions to continue practising. There were two artists out of the 23 we interviewed who considered their artwork able to provide full-time income, although this still relied on living costs remaining extremely low. “We are very lucky to have bought a very cheap property [in the country] that I can [also] have my workshop on, so I’m not paying for two properties in Melbourne […] So that certainly takes a fair bit of pressure off financially.” Their co-interviewee described this as “pretty luxurious!” Notably, the two who thought they could live off their art practices were both men, mid-career, whose works were large, spectacular festival items, which alongside the artists’ skill and hard work was also a factor in the type of remuneration received.Decongested LivingBeyond more affordable real estate and rental spaces, life outside our cities offers other benefits that have particular relevance to creative practitioners. Opera and festival director Lindy Hume described her move to the NSW South Coast in terms of space to think and be creative. “The abundance of time, space and silence makes living in places like [Hume’s town] ideal for creating new work” (Brown). And certainly, this was a theme that arose frequently in our interviews. Many of our regionally based artists were in part choosing the de-pressurised space of non-metro areas, and also seeking an embedded, daily connection to nature for themselves, their art-making process and their families. In one interview this was described as “dreamtime”. “Some of my more creative moments are out walking in the forest with the dog, that sort of semi-daydreamy thing where your mind is taken away by the place you’re in.”Creative HubsAll of our regional interviewees mentioned the value of the local community, as a general exchange, social support and like-minded connection, but also specifically of an arts community. Whether a tree change by choice or a more reactive move, the diaspora of artists, among others, has led to a type of rural renaissance in certain popular areas. Creative hubs located around the country, often in close proximity to the urban centres, are creating tremendous opportunities to network with other talented people doing interesting things, living in close proximity and often open to cross-fertilisation. One said: “[Castlemaine] is the best place in Australia, it has this insane cultural richness in a tiny town, you can’t go out and not meet people on the street […] For someone who has not had community in their life that is so gorgeous.” Another said:[Being an artist here] is kind of easy! Lots of people around to connect—with […] other artists but also creatively minded people [...] So it means you can just bump into someone from down the street and have an amazing conversation in five minutes about some amazing thing! […] There’s a concentration here that works.With these hubs, regional spaces are entering into a new relevance in the sphere of cultural production. They are generating unique and interesting local creative scenes for people to live amongst or visit, and generating strong local arts economies, tourist economies, and funding opportunities (Rentschler, Bridson, and Evans). Victoria in particular has burgeoned, with tourist flows to its regions increasing 13 per cent in 5 years and generating tourism worth $10 billion (Tourism Victoria). Victoria’s Greater Bendigo is Australia’s most popularly searched tourist destination on Trip Advisor, with tourism increasing 52% in 10 years (Boland). Simultaneously, funding flows have increased to regional zones, as governments seek to promote development outside Australia’s urban centres and are confident in the arts as a key strategy in boosting health, economies and overall wellbeing (see Rentschler, Bridson, and Evans; see also the 2018 Regional Centre for Culture initiative, Boland). The regions are also an increasingly relevant participant in national cultural life (Turnbull and Whitford; Mitchell; Simpson; Woodhead). Opportunities for an openness to productive exchange between regional and metropolitan sites appear to be growing, with regional festivals and art events gaining importance and unique attributes in the consciousness of the arts ‘centre’ (see for example Fairley; Simpson; Farrelly; Woodhead).Difficulties of Regional LocationDespite this, our interviews still brought to light the difficulties and barriers experienced living as a regional artist. For some, living in regional Victoria was an accepted set-back in their ambitions, something to be concealed and counteracted with education in reputable metropolitan art schools or city-based jobs. For others there was difficulty accessing a sympathetic arts community—although arts towns had vibrant cultures, certain types of creativity were preferred (often craft-based and more community-oriented). Practitioners who were active in maintaining their links to a metropolitan art scene voiced more difficulty in fitting in and successfully exhibiting their (often more conceptual or boundary-pushing) work in regional locations.The Gentrification ProblemThe other increasingly obvious issue in the revivification of some non-metropolitan areas is that they can and are already showing signs of being victims of their own success. That is, some regional arts precincts are attracting so many new residents that they are ceasing to be the low-cost, hospitable environments for artists they once were. Geographer David Ley has given attention to this particular pattern of gentrification that trails behind artists (Ley “Artists”). Ley draws from Florida’s ideas of late capitalism’s ascendency of creativity over the brute utilitarianism of the industrial era. This has got to the point that artists and creative professionals have an increasing capacity to shape and generate value in areas of life that were previous overlooked, especially with built environments (2529). Now more than ever, there is the “urbane middle-class” pursuing ‘the swirling milieu of artists, bohemians and immigrants” (Florida) as they create new, desirable landscapes with the “refuse of society” (Benjamin Charles Baudelaire 79; Ley New Middle Class). With Australia’s historic shifts in affordability in our major cities, this pattern that Ley identified in urban built environments can be seen across our states and regions as well.But with gentrification comes increased costs of living, as housing, shops and infrastructure all alter for an affluent consumer-resident. This diminishes what Bourdieu describes as “the suspension and removal of economic necessity” fundamental to the avant-garde (Bourdieu Distinction 54). That is to say, its relief from heavy pressure to materially survive is arguably critical to the reflexive, imaginative, and truly new offerings that art can provide. And as argued earlier, there seems an inbuilt economic irrationality in artmaking as a vocation—of dedicating one’s energy, time and resources to a pursuit that is notoriously impoverishing. But this irrationality may at the same time be critical to setting forth new ideas, perspectives, reflections and disruptions of taken-for-granted social assumptions, and why art is so indispensable in the first place (Bourdieu Field 39; Ley New Middle Class 2531; Weber on irrationality and the Enlightenment Project; also Adorno’s the ‘primitive’ in art). Australia’s cities, like those of most developed nations, increasingly demand we busy ourselves with the high-consumption of modern life that makes certain activities that sit outside this almost impossible. As gentrification unfolds from the metropolis to the regions, Australia faces a new level of far-reaching social inequality that has real consequences for who is able to participate in art-making, where these people can live, and ultimately what kind of diversity of ideas and voices participate in the generation of our national cultural life. ConclusionThe revival of some of Australia’s more popular regional towns has brought new life to some regional areas, particularly in reshaping their identities as cultural hubs worth experiencing, living amongst or supporting their development. Our interviews brought to life the significant benefits artists have experienced in relocating to country towns, whether by choice or necessity, as well as some setbacks. It was clear that economics played a major role in the demographic shift that took place in the area being examined; more specifically, that the general reorientation of social life towards consumption activities are having dramatic spatial consequences that we are currently seeing transform our major centres. The ability of art and creative practices to breathe new life into forgotten and devalued ideas and spaces is a foundational attribute but one that also creates a gentrification problem. Indeed, this is possibly the key drawback to the revivification of certain regional areas, alongside other prejudices and clashes between metro and regional cultures. It is argued that the transformative and redemptive actions art can perform need to involve the modern irrationality of not being transfixed by matters of economic materialism, so as to sit outside taken-for-granted value structures. This emphasises the importance of equality and open access in our spaces and landscapes if we are to pursue a vibrant, diverse and progressive national cultural sphere.ReferencesAbbing, Hans. Why Artists Are Poor: The Exceptional Economy of the Arts. Amsterdam: Amsterdam UP, 2002.Adorno, Theodor. Aesthetic Theory. London: Routledge, 1983.Australian Bureau of Statistics. “Population Growth: Capital City Growth and Development.” 4102.0—Australian Social Trends. 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