Journal articles on the topic 'Rotating flow'
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1
LOPEZ, J. M. "Characteristics of endwall and sidewall boundary layers in a rotating cylinder with a differentially rotating endwall." Journal of Fluid Mechanics 359 (March 25, 1998): 49–79. http://dx.doi.org/10.1017/s002211209700829x.
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The flow in a rotating cylinder driven by the differential rotation of its top endwall is studied by numerically solving the time-dependent axisymmetric Navier–Stokes equations. When the differential rotation is small, the flow is well described in terms of similarity solutions of individual rotating disks of infinite radius. For larger differential rotations, whether the top is co-rotating or counter-rotating results in qualitatively distinct behaviour. For counter-rotation, the boundary layer on the top endwall separates, forming a free shear layer and this results in a global coupling between the boundary layer flows on the various walls and a global departure from the similarity flows. At large Reynolds numbers, this shear layer becomes unstable. For a co-rotating top, there is a qualitative change in the flow depending on whether the top rotates faster or slower than the rest of the cylinder. When the top rotates faster, so does the bulk of the interior fluid, and the sidewall boundary layer region where the fluid adjusts to the slower rotation rate of the cylinder is centrifugally unstable. The secondary induced meridional flow is also potentially unstable in this region. This is manifested by the inflectional radial profiles of the vertical velocity and azimuthal vorticity in this region. At large Reynolds numbers, the instability of the sidewall layer results in roll waves propagating downwards.
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Torii, Shuichi, and Wen-Jei Yang. "Secondary Flow Phenomena in an Axially Rotating Flow Passage with Sudden Expansion or Contraction." International Journal of Rotating Machinery 5, no. 2 (1999): 117–22. http://dx.doi.org/10.1155/s1023621x9900010x.
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This paper investigates rotational effects on secondary flow in rotating flow passages with sudden expansion or contraction. Consideration is given to laminar flow. The governing boundary-layer equations are discretized by means of a finite-difference technique and numerically solved to determine the distributions of velocity vector under the appropriate boundary conditions. The Reynolds number (Re) and rotation rate are varied to determine their effects on the formation ofsecondary flows. It is disclosed from the study that: (i) when laminar flow is introduced into an axially rotating pipe with expansion, the stretch ofthe secondary flow zone is amplified with an increase in the rotation rate and Re, and (ii) in contrast, for axially rotating pipe flows with contraction, the secondary flow region is somewhat suppressed due to pipe rotation, and the change is slightly affected by the rotation rate and Re. Results may find applications in automotive and rotating hydraulic transmission lines.
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Geng, Xinge, Weiguo Wu, Erpeng Liu, Yongshui Lin, Wei Chen, and Chang-Kyu Rheem. "Experimental Study on Vibration of a Rotating Pipe in Still Water and in Flow." Polish Maritime Research 30, no. 1 (March 1, 2023): 65–77. http://dx.doi.org/10.2478/pomr-2023-0007.
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Abstract To illustrate the vibration characteristics of a rotating pipe in flow, experiments were conducted for a pipe in flow, a rotating pipe in still water and a rotating pipe in flow. For the pipe in flow without rotation, the trajectory diagram is ‘8’ shaped. For the rotating pipe in still water, a multiple frequency component was induced, and a ‘positive direction whirl’ was found. For the flow and rotation, at a flow velocity of 0.46 m/s, the vibration is dominated by the combination of flow and rotation. With an increase in rotating frequency, the trajectory of the rotating pipe varies from an ‘8’ shape to a circular shape and the ‘reverse direction whirl’ is induced, which is different from ‘positive direction’ in still water. The vibration frequency ratio increases uniformly with flow velocity. At a flow velocity of 1.02 m/s, at which the frequency is close to the theoretical natural frequency, the vibration frequency ratio is f*≈1. Predominantly governed by vortex-induced vibration (VIV), the vibration behavior of a rotating pipe subjected to fluid flow conditions has been found to exhibit complete vanishing of whirl. The vibration characteristics of a rotating pipe in flow are studied by the experiments which is benefit for structural drilling design.
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Jose, Sharath, and Rama Govindarajan. "Non-normal origin of modal instabilities in rotating plane shear flows." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 476, no. 2233 (January 2020): 20190550. http://dx.doi.org/10.1098/rspa.2019.0550.
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Small variations introduced in shear flows are known to affect stability dramatically. Rotation of the flow system is one example, where the critical Reynolds number for exponential instabilities falls steeply with a small increase in rotation rate. We ask whether there is a fundamental reason for this sensitivity to rotation. We answer in the affirmative, showing that it is the non-normality of the stability operator in the absence of rotation which triggers this sensitivity. We treat the flow in the presence of rotation as a perturbation on the non-rotating case, and show that the rotating case is a special element of the pseudospectrum of the non-rotating case. Thus, while the non-rotating flow is always modally stable to streamwise-independent perturbations, rotating flows with the smallest rotation are unstable at zero streamwise wavenumber, with the spanwise wavenumbers close to that of disturbances with the highest transient growth in the non-rotating case. The instability critical rotation number scales inversely as the square of the Reynolds number, which we demonstrate is the same as the scaling obeyed by the minimum perturbation amplitude in non-rotating shear flow needed for the pseudospectrum to cross the neutral line. Plane Poiseuille flow and plane Couette flow are shown to behave similarly in this context.
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Kazachkov, Ivan. "Modeling of the Flow due to Double Rotations Causing Phenomenon of Negative Pressure." WSEAS TRANSACTIONS ON FLUID MECHANICS 18 (December 31, 2023): 259–71. http://dx.doi.org/10.37394/232013.2023.18.25.
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This paper is devoted to mathematical modeling and computational experiments of a flow with negative pressure. A previously unknown class of fluid flow under the action of counter-current centrifugal forces is in focus. Volumetric forces in a non-conducting fluid can arise from gravity, vibrations, or rotations. In this paper, we consider controlled variable volumetric forces in a system with two rotations around the vertical axis and the tangential axis of a horizontal disk rotating around the vertical axis. The study of the coordinate system during double rotation showed that the double rotation about two perpendicular axes, one of which moves along a tangential direction to the rotating horizontal disk, is equal to the rotation around the oscillating axis inclined at some angle to the vertical axis.
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Yang, Wen-Jei, Shin Fann, and John H. Kim. "Heat and Fluid Flow Inside Rotating Channels." Applied Mechanics Reviews 47, no. 8 (August 1, 1994): 367–96. http://dx.doi.org/10.1115/1.3111084.
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Power generation and refrigeration accomplished by means of rotating or reciprocating machinery. One of the basic elements of rotating machinery is the rotating channel system. With the desire for ever increasing efficiency in power generation and refrigeration, higher or lower operating temperatures are achieved. It has provided motivation for the pursuit of knowledge on heat transfer and fluid flow characteristics. This paper reviews the literature pertinent to studies of fluid flow and/or heat transfer in channel flows subjected to radial rotation, parallel rotation, and coaxial revolution. Special problems unique to rotating systems are discussed and future study areas are suggested.
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MITTAL, SANJAY, and BHASKAR KUMAR. "Flow past a rotating cylinder." Journal of Fluid Mechanics 476 (February 10, 2003): 303–34. http://dx.doi.org/10.1017/s0022112002002938.
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Flow past a spinning circular cylinder placed in a uniform stream is investigated via two-dimensional computations. A stabilized finite element method is utilized to solve the incompressible Navier–Stokes equations in the primitive variables formulation. The Reynolds number based on the cylinder diameter and free-stream speed of the flow is 200. The non-dimensional rotation rate, α (ratio of the surface speed and freestream speed), is varied between 0 and 5. The time integration of the flow equations is carried out for very large dimensionless time. Vortex shedding is observed for α < 1.91. For higher rotation rates the flow achieves a steady state except for 4.34 < α < 4:70 where the flow is unstable again. In the second region of instability, only one-sided vortex shedding takes place. To ascertain the instability of flow as a function of α a stabilized finite element formulation is proposed to carry out a global, non-parallel stability analysis of the two-dimensional steady-state flow for small disturbances. The formulation and its implementation are validated by predicting the Hopf bifurcation for flow past a non-rotating cylinder. The results from the stability analysis for the rotating cylinder are in very good agreement with those from direct numerical simulations. For large rotation rates, very large lift coefficients can be obtained via the Magnus effect. However, the power requirement for rotating the cylinder increases rapidly with rotation rate.
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Bech, Knut H., and Helge I. Andersson. "Secondary flow in weakly rotating turbulent plane Couette flow." Journal of Fluid Mechanics 317 (June 25, 1996): 195–214. http://dx.doi.org/10.1017/s0022112096000729.
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As in the laminar case, the turbulent plane Couette flow is unstable (stable) with respect to roll cell instabilities when the weak background angular velocity Ωk is antiparallel (parallel) to the spanwise mean flow vorticity (-dU/dy)k. The critical value of the rotation number Ro, based on 2Ω and dU/dy of the corresponding laminar flow, was estimated as 0.0002 at a low Reynolds number with fully developed turbulence. Direct numerical simulations were performed for Ro = ±0.01 and compared with earlier results for non-rotating Couette flow. At the low rotation rates considered, both senses of rotation damped the turbulence and the number of near-wall turbulence-generating events was reduced. The destabilized flow was more energetic, but less three-dimensional, than the non-rotating flow. In the destabilized case, the two-dimensional roll cells extracted a comparable amount of kinetic energy from the mean flow as did the turbulence, thereby decreasing the turbulent kinetic energy. The turbulence anisotropy was practically unaffected by weak spanwise rotation, while the secondary flow was highly anisotropic due to its inability to contract and expand in the streamwise direction.
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Takayama, Shinichi, and Katsumi Aoki. "Flow Characteristics around Rotating Circular Cylinder with Grooves(Flow around Cylinder 2)." Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2005 (2005): 533–37. http://dx.doi.org/10.1299/jsmeicjwsf.2005.533.
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Toplosky, N., and T. R. Akylas. "Nonlinear spiral waves in rotating pipe flow." Journal of Fluid Mechanics 190 (May 1988): 39–54. http://dx.doi.org/10.1017/s0022112088001193.
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A numerical investigation of finite-amplitude, non-axisymmetric disturbances, in the form of travelling spiral waves, is made in pipe flow with superimposed solid-body rotation. Rotating pipe flow is found to be supercritically unstable both in the rapid and slow-rotation regimes. Earlier weakly nonlinear calculations, suggesting subcritical instability in the slow-rotation limit, are shown to be in error. Bifurcating neutral waves are calculated for various axial and azimuthal Reynolds numbers and wavenumbers. For fixed axial mean pressure gradient, the axial mean flow induced by these waves gives rise to a significant flux defect, in certain cases as large as 40-50% of the undisturbed mass flux; the possible relevance of this finding to the phenomenon of vortex breakdown is pointed out. In non-rotating pipe flow, no neutral disturbances in the assumed form of spiral waves are found for moderate Reynolds numbers; this indicates that previous conjectures, regarding a possible connection between nonlinear spiral waves in slowly rotating pipe flow and the asymptotic neutral states of Smith & Bodonyi (1982) in non-rotating pipe flow, are not valid.
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Kazachkov, Ivan V. "Stability Analysis for Complex Rotational Flow." WSEAS TRANSACTIONS ON APPLIED AND THEORETICAL MECHANICS 16 (August 10, 2021): 62–72. http://dx.doi.org/10.37394/232011.2021.16.7.
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Based on the earlier developed mathematical model of the complex flow due to the double rotations in two perpendicular directions, the stability analysis is performed in the paper. The Navier-Stokes equations are derived in the coordinate system rotating around the two perpendicular different axes, the vertical one of them is arranged on some distance from the other axis of rotation, the horizontal axis is directed along the tangential line to the circle of the vertical rotation. The two centrifugal and Coriolis forces create the unique features in high oscillating flow, with localities of the stretched liquid, due to their action varying by the circumferential cylindrical coordinate in the channel flow. Stability analysis for the complex rotational flow under double rotations creating strongly varying mass forces and stretching of the liquid is considered at first
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Bourguet, Rémi, and David Lo Jacono. "Flow-induced vibrations of a rotating cylinder." Journal of Fluid Mechanics 740 (February 6, 2014): 342–80. http://dx.doi.org/10.1017/jfm.2013.665.
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AbstractThe flow-induced vibrations of a circular cylinder, free to oscillate in the cross-flow direction and subjected to a forced rotation about its axis, are analysed by means of two- and three-dimensional numerical simulations. The impact of the symmetry breaking caused by the forced rotation on the vortex-induced vibration (VIV) mechanisms is investigated for a Reynolds number equal to $100$, based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate freely up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to $4$. Under forced rotation, the vibration amplitude exhibits a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency) and reaches $1.9$ diameters, i.e. three times the maximum amplitude in the non-rotating case. The free vibrations of the rotating cylinder occur under a condition of wake–body synchronization similar to the lock-in condition driving non-rotating cylinder VIV. The largest vibration amplitudes are associated with a novel asymmetric wake pattern composed of a triplet of vortices and a single vortex shed per cycle, the ${\rm T} + {\rm S}$ pattern. In the low-frequency vibration regime, the flow exhibits another new topology, the U pattern, characterized by a transverse undulation of the spanwise vorticity layers without vortex detachment; consequently, free oscillations of the rotating cylinder may also develop in the absence of vortex shedding. The symmetry breaking due to the rotation is shown to directly impact the selection of the higher harmonics appearing in the fluid force spectra. The rotation also influences the mechanism of phasing between the force and the structural response.
13
Soong, C. Y. "Thermal Buoyancy Effects in Rotating Non-Isothermal Flows." International Journal of Rotating Machinery 7, no. 6 (2001): 435–46. http://dx.doi.org/10.1155/s1023621x01000380.
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The present paper is concerned with the non-isothermal flow mechanisms in rotating systems with emphasis on the rotation-induced thermal buoyancy effects stemming from the coexistence of rotational body forces and the nonuniformity of the fluid temperature field. Non-isothermal flow in rotating ducts of radial and parallel modes and rotating cylindrical configurations, including rotating cylinders and disk systems, are considered. Previous investigations closely related to the rotational buoyancy are surveyed. The mechanisms of the rotation-induced buoyancy are manifested by the author's recent theoretical results and scaling analyses pertaining to the rotation-induced buoyancy in rotating ducts and two-disk systems. Finally, the open issues for future researches in this area are proposed.
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GRUNDESTAM, OLOF, STEFAN WALLIN, and ARNE V. JOHANSSON. "Direct numerical simulations of rotating turbulent channel flow." Journal of Fluid Mechanics 598 (February 25, 2008): 177–99. http://dx.doi.org/10.1017/s0022112007000122.
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Fully developed rotating turbulent channel flow has been studied, through direct numerical simulations, for the complete range of rotation numbers for which the flow is turbulent. The present investigation suggests that complete flow laminarization occurs at a rotation number Ro = 2Ωδ/Ub ≤ 3.0, where Ω denotes the system rotation, Ub is the mean bulk velocity and δ is the half-width of the channel. Simulations were performed for ten different rotation numbers in the range 0.98 to 2.49 and complemented with earlier simulations (done in our group) for lower values of Ro. The friction Reynolds number Reτ = uτδ/ν (where uτ is the wall-shear velocity and ν is the kinematic viscosity) was chosen as 180 for these simulations. A striking feature of rotating channel flow is the division into a turbulent (unstable) and an almost laminarized (stable) side. The relatively distinct interface between these two regions was found to be maintained by a balance where negative turbulence production plays an important role. The maximum difference in wall-shear stress between the two sides was found to occur for a rotation number of about 0.5. The bulk flow was found to monotonically increase with increasing rotation number and reach a value (for Reτ = 180) at the laminar limit (Ro = 3.0) four times that of the non-rotating case.
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ESLER, J. G., O. J. RUMP, and E. R. JOHNSON. "Transcritical rotating flow over topography." Journal of Fluid Mechanics 590 (October 15, 2007): 81–106. http://dx.doi.org/10.1017/s0022112007007719.
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The flow of a one-and-a-half layer fluid over a three-dimensional obstacle of non-dimensional height M, relative to the lower layer depth, is investigated in the presence of rotation, the magnitude of which is measured by a non-dimensional parameter B (inverse Burger number). The transcritical regime in which the Froude number F, the ratio of the flow speed to the interfacial gravity wave speed, is close to unity is considered in the shallow-water (small-aspect-ratio) limit. For weakly rotating flow over a small isolated obstacle (M → 0) a similarity theory is developed in which the behaviour is shown to depend on the parameters Γ = (F−1)M−2/3 and ν = B1/2M−1/3. The flow pattern in this regime is determined by a nonlinear equation in which Γ and ν appear explicitly, termed here the ‘rotating transcritical small-disturbance equation’ (rTSD equation, following the analogy with compressible gasdynamics). The rTSD equation is forced by ‘equivalent aerofoil’ boundary conditions specific to each obstacle. Several qualitatively new flow behaviours are exhibited, and the parameter reduction afforded by the theory allows a (Γ, ν) regime diagram describing these behaviours to be constructed numerically. One important result is that, in a supercritical oncoming flow in the presence of sufficient rotation (ν ≳ 2), hydraulic jumps can appear downstream of the obstacle even in the absence of an upstream jump. Rotation is found to have the general effect of increasing the amplitude of any existing downstream hydraulic jumps and reducing the lateral extent and amplitude of upstream jumps. Numerical results are compared with results from a shock-capturing shallow-water model, and the (Γ, ν) regime diagram is found to give good qualitative and quantitative predictions of flow patterns at finite obstacle height (at least for M ≲ 0.4). Results are compared and contrasted with those for a two-dimensional obstacle or ridge, for which rotation also causes hydraulic jumps to form downstream of the obstacle and acts to attenuate upstream jumps.
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Durst, F., and H. Raszillier. "Flow in a Rotating Straight Pipe, With a View on Coriolis Mass Flow Meters." Journal of Fluids Engineering 112, no. 2 (June 1, 1990): 149–54. http://dx.doi.org/10.1115/1.2909378.
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The fully developed flow through a straight pipe, which rotates about an axis perpendicular to its own, is considered. The perturbation of the Hagen-Poiseuille flow, produced by the pipe rotation, is computed to second order and its features are described. The force of the fluid on the rotating pipe is correlated with other parameters of the flow, among them the mass flow rate Q˙. Possible relevance of the flow field and of the fluid forces in the rotating pipe for Coriolis flow meters are discussed.
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Baekt, Je Hyun, and Chang Hwan Ko. "Numerical Flow Analysis in a Rotating Square Duct and a Rotating Curved-Duct." International Journal of Rotating Machinery 6, no. 1 (2000): 1–9. http://dx.doi.org/10.1155/s1023621x00000014.
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A numerical study is conducted on the fully-developed laminar flow of an incompressible viscous fluid in a square duct rotating about a perpendicular axis to the axial direction of the duct. At the straight duct, the rotation produces vortices due to the Coriolis force. Generally two vortex cells are formed and the axial velocity distribution is distorted by the effect of this Coriolis force. When a convective force is weak, two counter-rotating vortices are shown with a quasi-parabolic axial velocity profile for weak rotation rates. As the rotation rate increases, the axial velocity on the vertical centreline of the duct begins to flatten and the location of vorticity center is moved near to wall by the effect of the Coriolis force. When the convective inertia force is strong, a double-vortex secondary flow appears in the transverse planes of the duct for weak rotation rates but as the speed of rotation increases the secondary flow is shown to split into an asymmetric configuration of four counter-rotating vortices. If the rotation rates are increased further, the secondary flow restabilizes to a slightly asymmetric double-vortex configuration. Also, a numerical study is conducted on the laminar flow of an incompressible viscous fluid in a90°-bend square duct that rotates about axis parallel to the axial direction of the inlet. At a90°-bend square duct, the feature of flow by the effect of a Coriolis force and a centrifugal force, namely a secondary flow by the centrifugal force in the curved region and the Coriolis force in the downstream region, is shown since the centrifugal force in curved region and the Coriolis force in downstream region are dominant respectively.
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Citro, V., J. Tchoufag, D. Fabre, F. Giannetti, and P. Luchini. "Linear stability and weakly nonlinear analysis of the flow past rotating spheres." Journal of Fluid Mechanics 807 (October 18, 2016): 62–86. http://dx.doi.org/10.1017/jfm.2016.596.
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We study the flow past a sphere rotating in the transverse direction with respect to the incoming uniform flow, and particularly consider the stability features of the wake as a function of the Reynolds number $Re$ and the sphere dimensionless rotation rate $\unicode[STIX]{x1D6FA}$. Direct numerical simulations and three-dimensional global stability analyses are performed in the ranges $150\leqslant \mathit{Re}\leqslant 300$ and $0\leqslant \unicode[STIX]{x1D6FA}\leqslant 1.2$. We first describe the base flow, computed as the steady solution of the Navier–Stokes equation, with special attention to the structure of the recirculating region and to the lift force exerted on the sphere. The stability analysis of this base flow shows the existence of two different unstable modes, which occur in different regions of the $Re/\unicode[STIX]{x1D6FA}$ parameter plane. Mode I, which exists for weak rotations ($\unicode[STIX]{x1D6FA}<0.4$), is similar to the unsteady mode existing for a non-rotating sphere. Mode II, which exists for larger rotations ($\unicode[STIX]{x1D6FA}>0.7$), is characterized by a larger frequency. Both modes preserve the planar symmetry of the base flow. We detail the structure of these eigenmodes, as well as their structural sensitivity, using adjoint methods. Considering small rotations, we then compare the numerical results with those obtained using weakly nonlinear approaches. We show that the steady bifurcation occurring for $Re>212$ for a non-rotating sphere is changed into an imperfect bifurcation, unveiling the existence of two other base-flow solutions which are always unstable.
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Brady, John F., and Louis Durlofsky. "On rotating disk flow." Journal of Fluid Mechanics 175, no. -1 (February 1987): 363. http://dx.doi.org/10.1017/s0022112087000430.
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Alexakis, A. "Rotating Taylor–Green flow." Journal of Fluid Mechanics 769 (March 13, 2015): 46–78. http://dx.doi.org/10.1017/jfm.2015.82.
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The steady state of a forced Taylor–Green flow is investigated in a rotating frame of reference. The investigation involves the results of 184 numerical simulations for different Reynolds numbers $\mathit{Re}_{F}$ and Rossby numbers $\mathit{Ro}_{F}$. The large number of examined runs allows a systematic study that enables the mapping of the different behaviours observed to the parameter space ($\mathit{Re}_{F},\mathit{Ro}_{F}$), and the examination of different limiting procedures for approaching the large $\mathit{Re}_{F}$ small $\mathit{Ro}_{F}$ limit. Four distinctly different states were identified: laminar, intermittent bursts, quasi-two-dimensional condensates and weakly rotating turbulence. These four different states are separated by power-law boundaries $\mathit{Ro}_{F}\propto \mathit{Re}_{F}^{-{\it\gamma}}$ in the small $\mathit{Ro}_{F}$ limit. In this limit, the predictions of asymptotic expansions can be directly compared with the results of the direct numerical simulations. While the first-order expansion is in good agreement with the results of the linear stability theory, it fails to reproduce the dynamical behaviour of the quasi-two-dimensional part of the flow in the nonlinear regime, indicating that higher-order terms in the expansion need to be taken into account. The large number of simulations allows also to investigate the scaling that relates the amplitude of the fluctuations with the energy dissipation rate and the control parameters of the system for the different states of the flow. Different scaling was observed for different states of the flow, that are discussed in detail. The present results clearly demonstrate that the limits of small Rossby and large Reynolds numbers do not commute and it is important to specify the order in which they are taken.
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BARNES, D. R., and R. R. KERSWELL. "New results in rotating Hagen–Poiseuille flow." Journal of Fluid Mechanics 417 (August 25, 2000): 103–26. http://dx.doi.org/10.1017/s0022112000008909.
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New three-dimensional finite-amplitude travelling-wave solutions are found in rotating Hagen–Poiseuille flow (RHPF[Ωa, Ωp]) where fluid is driven by a constant pressure gradient along a pipe rotating axially at rate Ωa and at Ωp about a perpendicular diameter. For purely axial rotation (RHPF[Ωa, 0]), the two-dimensional helical waves found by Toplosky & Akylas (1988) are found to become unstable to three-dimensional travelling waves in a supercritical Hopf bifurcation. The addition of a perpendicular rotation at low axial rotation rates is found only to stabilize the system. In the absence of axial rotation, the two-dimensional steady flow solution in RHPF[0, Ωp] which connects smoothly to Hagen–Poiseuille flow as Ωp → 0 is found to be stable at all Reynolds numbers below 104. At high axial rotation rates, the superposition of a perpendicular rotation produces a ‘precessional’ instability which here is found to be a supercritical Hopf bifurcation leading directly to three-dimensional travelling waves. Owing to the supercritical nature of this primary bifurcation and the secondary bifurcation found in RHPF[Ωa, 0], no opportunity therefore exists to continue these three-dimensional finite-amplitude solutions in RHPF back to Hagen–Poiseuille flow. This then contrasts with the situation in narrow-gap Taylor–Couette flow where just such a connection exists to plane Couette flow.
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Tanasheva, N. K. "NUMERICAL SIMULATION OF THE FLOW AROUND A WIND WHEEL WITH ROTATING CYLINDRICAL BLADES." Eurasian Physical Technical Journal 18, no. 1 (March 30, 2021): 51–56. http://dx.doi.org/10.31489/2021no1/51-56.
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The article discusses the results of numerical simulation of the flow around a wind wheel with blades in the form of rotating cylinders using the software package ANSYS. The advantage of a wind turbine with rotating cylindrical blades in comparison with traditional blade installations is the starting moment and the beginning of energy production at a wind speed of (2 - 3) m/s. A mathematical model has been developed based on threedimensional Navier-Stokes equations in a rotating system. The corresponding boundary conditions are formulated. A calculated pattern of the flow around the wind wheel with rotating cylindrical blade is obtained. There are shown regions of the velocity field with turbulent vortices, which are formed at high Reynolds numbers. The degree of influence of the angular speed of rotation of the wind wheel on the magnitude of the moment of forces at various speeds of the incoming air flow has been determined.
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Lopez, Juan M., and Paloma Gutierrez-Castillo. "Three-dimensional instabilities and inertial waves in a rapidly rotating split-cylinder flow." Journal of Fluid Mechanics 800 (July 13, 2016): 666–87. http://dx.doi.org/10.1017/jfm.2016.419.
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The nonlinear dynamics of the flow in a differentially rotating split cylinder is investigated numerically. The differential rotation, with the top half of the cylinder rotating faster than the bottom half, establishes a basic state consisting of a bulk flow that is essentially in solid-body rotation at the mean rotation rate of the cylinder and boundary layers where the bulk flow adjusts to the differential rotation of the cylinder halves, which drives a strong meridional flow. There are Ekman-like layers on the top and bottom end walls, and a Stewartson-like side wall layer with a strong downward axial flow component. The complicated bottom corner region, where the downward flow in the side wall layer decelerates and negotiates the corner, is the epicentre of a variety of instabilities associated with the local shear and curvature of the flow, both of which are very non-uniform. Families of both high and low azimuthal wavenumber rotating waves bifurcate from the basic state in Eckhaus bands, but the most prominent states found near onset are quasiperiodic states corresponding to mixed modes of the high and low azimuthal wavenumber rotating waves. The frequencies associated with most of these unsteady three-dimensional states are such that spiral inertial wave beams are emitted from the bottom corner region into the bulk, along cones at angles that are well predicted by the inertial wave dispersion relation, driving the bulk flow away from solid-body rotation.
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Kim, Kyung Min, Sang In Kim, Yun Heung Jeon, Dong Hyun Lee, and Hyung Hee Cho. "Detailed Heat/Mass Transfer Distributions in a Rotating Smooth Channel With Bleed Flow." Journal of Heat Transfer 129, no. 11 (March 10, 2007): 1538–45. http://dx.doi.org/10.1115/1.2759974.
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In this study, the effects of bleed flow on heat/mass transfer in a rotating smooth square channel were investigated. The hydraulic diameter (Dh) of the channel was 40.0mm, and the diameter of the bleed holes (d) on the leading surface was 4.5mm. Tests were conducted under various bleed flow rates (0%, 10%, 20%) and rotation numbers (0, 0.2, 0.4), while the Reynolds number was fixed at 10,000. A naphthalene sublimation method was employed to determine the detailed heat transfer coefficients using a heat and mass transfer analogy. The results suggested heat/mass transfer characteristics in the internal cooling passage to be influenced by tripping flow as well as Coriolis force induced by bleed flow and channel rotation. In cases influenced by bleed flow, the heat/mass transfer on the leading surface was higher than that without bleed flow. The heat/mass transfer on the leading surface increased with the number of rotations to Ro=0.2, after which it decreased due to rotation effects.
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Wong, K. W. L., J. Zhao, D. Lo Jacono, M. C. Thompson, and J. Sheridan. "Experimental investigation of flow-induced vibration of a rotating circular cylinder." Journal of Fluid Mechanics 829 (September 21, 2017): 486–511. http://dx.doi.org/10.1017/jfm.2017.540.
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While flow-induced vibration of bluff bodies has been extensively studied over the last half-century, only limited attention has been given to flow-induced vibration of elastically mounted rotating cylinders. Since recent low-Reynolds-number numerical work suggests that rotation can enhance or suppress the natural oscillatory response, the former could find applications in energy harvesting and the latter in vibration control. The present experimental investigation characterises the dynamic response and wake structure of a rotating circular cylinder undergoing vortex-induced vibration at a low mass ratio ($m^{\ast }=5.78$) over the reduced velocity range leading to strong oscillations. The experiments were conducted in a free-surface water channel with the cylinder vertically mounted and attached to a motor that provided constant rotation. Springs and an air-bearing system allow the cylinder to undertake low-damped transverse oscillations. Under cylinder rotation, the normalised frequency response was found to be comparable to that of a freely vibrating non-rotating cylinder. At reduced velocities consistent with the upper branch of a non-rotating transversely oscillating cylinder, the maximum oscillation amplitude increased with non-dimensional rotation rate up to $\unicode[STIX]{x1D6FC}\approx 2$. Beyond this, there was a sharp decrease in amplitude. Notably, this critical value corresponds approximately to the rotation rate at which vortex shedding ceases for a non-oscillating rotating cylinder. Remarkably, at $\unicode[STIX]{x1D6FC}=2$ there was approximately an 80 % increase in the peak amplitude response compared to that of a non-rotating cylinder. The observed amplitude response measured over the Reynolds-number range of ($1100\lesssim Re\lesssim 6300$) is significantly different from numerical predictions and other experimental results recorded at significantly lower Reynolds numbers.
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Jain, Kiran, Rudolf Komm, Irene González Hernández, Sushant C. Tripathy, and Frank Hill. "Subsurface flows associated with rotating sunspots." Proceedings of the International Astronomical Union 6, S273 (August 2010): 356–60. http://dx.doi.org/10.1017/s1743921311015547.
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AbstractIn this paper, we compare components of the horizontal flow below the solar surface in and around regions consisting of rotating and non-rotating sunspots. Our analysis suggests that there is a significant variation in both components of the horizontal flow at the beginning of sunspot rotation as compared to the non-rotating sunspot. The flows in surrounding areas are in most cases relatively small. However, there is a significant influence of the motion on flows in an area closest to the sunspot rotation.
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Schulmeister, James C., J. M. Dahl, G. D. Weymouth, and M. S. Triantafyllou. "Flow control with rotating cylinders." Journal of Fluid Mechanics 825 (July 21, 2017): 743–63. http://dx.doi.org/10.1017/jfm.2017.395.
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We study the use of small counter-rotating cylinders to control the streaming flow past a larger main cylinder for drag reduction. In a water tunnel experiment at a Reynolds number of 47 000 with a three-dimensional and turbulent wake, particle image velocimetry (PIV) measurements show that rotating cylinders narrow the mean wake and shorten the recirculation length. The drag of the main cylinder was measured to reduce by up to 45 %. To examine the physical mechanism of the flow control in detail, a series of two-dimensional numerical simulations at a Reynolds number equal to 500 were conducted. These simulations investigated a range of control cylinder diameters in addition to rotation rates and gaps to the main cylinder. Effectively controlled simulated flows present a streamline that separates from the main cylinder, passes around the control cylinder, and reattaches to the main cylinder at a higher pressure. The computed pressure recovery from the separation to reattachment points collapses with respect to a new scaling, which indicates that the control mechanism is viscous.
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ERN, PATRICIA, and JOSÉ EDUARDO WESFREID. "Flow between time-periodically co-rotating cylinders." Journal of Fluid Mechanics 397 (October 25, 1999): 73–98. http://dx.doi.org/10.1017/s0022112099006059.
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We consider oscillatory flows between concentric co-rotating cylinders at angular velocity Ω(t) = Ωm + Ωo cos ωt as a prototype to investigate the competing effects of centrifugal and Coriolis forces on the flow stability. We first study by flow visualization the effect of the mean rotation Ωm on the centrifugal destabilization due to the temporal modulation. We show that increasing the mean rotation first destabilizes and then restabilizes the flow. The instability of the purely azimuthal basic flow is then analysed by investigating the dynamics of the axial velocity component of the vortex structures. Velocity measurements performed in the rotating frame of the cylinders using ultrasound Doppler velocimetry show that secondary flow appears and disappears several times during a flow period. Based on a finite-gap expression for the basic flow, linear stability analysis is performed with a quasi-steady approach, providing the times of appearance and disappearance of secondary flow in a cycle as well as the effect on the instability threshold of the mean rotation. The theoretical and numerical results are in agreement with experimental results up to intermediate values of the frequency. Notably, the flow periodically undergoes restabilization at particular time intervals.
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SUN, CHAO, TOM MULLIN, LEEN VAN WIJNGAARDEN, and DETLEF LOHSE. "Drag and lift forces on a counter-rotating cylinder in rotating flow." Journal of Fluid Mechanics 664 (October 12, 2010): 150–73. http://dx.doi.org/10.1017/s0022112010003666.
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Results are reported of an experimental investigation into the motion of a heavy cylinder free to move inside a water-filled drum rotating around its horizontal axis. The cylinder is observed to either co-rotate or, counter-intuitively, counter-rotate with respect to the rotating drum. The flow was measured with particle image velocimetry, and it was found that the inner cylinder significantly altered the bulk flow field from the solid-body rotation found for a fluid-filled drum. In the counter-rotation case, the generated lift force allowed the cylinder to freely rotate without contact with the drum wall. Drag and lift coefficients of the freely counter-rotating cylinder were measured over a wide range of Reynolds numbers, 2500 < Re < 25000, dimensionless rotation rates, 0.0 < α < 1.2, and gap to cylinder diameter ratios 0.003 < G/2a < 0.5. Drag coefficients were consistent with previous measurements on a cylinder in a uniform flow. However, for the lift coefficient, considerably larger values were observed in the present measurements. We found the enhancement of the lift force to be mainly caused by the vicinity of the wall.
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Hathaway, David H., and Richard C. J. Somerville. "Nonlinear interactions between convection, rotation and flows with vertical shear." Journal of Fluid Mechanics 164 (March 1986): 91–105. http://dx.doi.org/10.1017/s0022112086002483.
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A three-dimensional and time-dependent numerical model is used to study the nonlinear interactions between thermal convective motions, rotation, and imposed flows with vertical shear. All cases have Rayleigh numbers of 104 and Prandtl numbers of 1.0. Rotating cases have Taylor numbers of 104.For the non-rotating cases, the effects of the shear on the convection produce longitudinal rolls aligned with the shear flow and a downgradient flux of momentum. The interaction between the convection and the shear flow decreases the shear in the interior of the fluid layer while adding kinetic energy to the convective motions. For unit Prandtl number the dimensionless flux of momentum is equal to the dimensionless flux of heat.For rotating cases with vertical rotation vectors, the shear flow favours rolls aligned with the shear and produces a downgradient flux of momentum. However, the Coriolis force turns the flow induced by the convection to produce a more complicated shear that changes direction with height. As in the non-rotating cases, the convective motions become more energetic by extracting energy from the mean flow. For Richardson numbers larger than about − 1.0, the dominant source of eddy kinetic energy is the shear flow rather than buoyancy.For rotating cases with tilted rotation vectors the results depend upon the direction of the shear. For weak shear, convective rolls aligned with the rotation vector are favoured. When the shear flow is directed to the east along the top, the rolls become broader and the convection weaker. For large shear in this direction, the convective motions are quenched by the competition between the shear flow and the tilted rotation vector. When the shear flow is directed to the west along the top, strong shear produces rolls aligned with the shear. The heat and momentum fluxes become large and can exceed those found in the absence of a tilted rotation vector. Countergradient fluxes of momentum can also be produced.
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Hyun, Jae Min. "Transient Starting Flow in a Cylinder With Counter-Rotating Endwall Disks." Journal of Fluids Engineering 107, no. 1 (March 1, 1985): 92–96. http://dx.doi.org/10.1115/1.3242447.
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Spin-up from rest in a cylinder with top and bottom endwall disks rotating in opposite directions (ΩT and ΩB are the respective rotation rate, but S[≡ ΩT/ΩB] < 0) is investigated. The sidewall is fixed to the faster-rotating disk. A finite-difference numerical model is adopted to integrate the unsteady Navier-Stokes equations. We consider a cylinder of aspect ratio 0(1) and minute Ekman numbers. Numerical solutions are presented to show the transient azimuthal flow structures, axial vorticity profiles, and meridional flow patterns. An azimuthal velocity front, which separates the rotating from the nonrotating fluid, propagates radially inward from the sidewall. The appearance of the front is similar to the front propagation in spin-up in a rigid cylinder. As S decreases from zero, the direction of rotation in the bulk of the interior fluid becomes the same as that of the faster-rotating disk. The azimuthal velocities are still vertically uniform in the bulk of the interior. The scaled time to reach the steady state decreases. The angular velocities of the interior fluid near the central axis become very small. Under counter-rotation, the meridional circulation forms a two-cell structure. A stagnation point appears on the slower-rotating disk. During spin-up, the stagnation point moves from the sidewall to its steady-state position. As counter-rotation increases, the radial distance traveled by the stagnation point decreases.
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Froitzheim, A., S. Merbold, and C. Egbers. "Velocity profiles, flow structures and scalings in a wide-gap turbulent Taylor–Couette flow." Journal of Fluid Mechanics 831 (October 13, 2017): 330–57. http://dx.doi.org/10.1017/jfm.2017.634.
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Fully turbulent Taylor–Couette flow between independently rotating cylinders is investigated experimentally in a wide-gap configuration ($\unicode[STIX]{x1D702}=0.5$) around the maximum transport of angular momentum. In that regime turbulent Taylor vortices are present inside the gap, leading to a pronounced axial dependence of the flow. To account for this dependence, we measure the radial and azimuthal velocity components in horizontal planes at different cylinder heights using particle image velocimetry. The ratio of angular velocities of the cylinder walls $\unicode[STIX]{x1D707}$, where the torque maximum appears, is located in the low counter-rotating regime ($\unicode[STIX]{x1D707}_{max}(\unicode[STIX]{x1D702}=0.5)=-0.2$). This point coincides with the smallest radial gradient of angular velocity in the bulk and the detachment of the neutral surface from the outer cylinder wall, where the azimuthal velocity component vanishes. The structure of the flow is further revealed by decomposing the flow field into its large-scale and turbulent contributions. Applying this decomposition to the kinetic energy, we can analyse the formation process of the turbulent Taylor vortices in more detail. Starting at pure inner cylinder rotation, the vortices are formed and strengthened until $\unicode[STIX]{x1D707}=-0.2$ quite continuously, while they break down rapidly for higher counter-rotation. The same picture is shown by the decomposed Nusselt number, and the range of rotation ratios, where turbulent Taylor vortices can exist, shrinks strongly in comparison to investigations at much lower shear Reynolds numbers. Moreover, we analyse the scaling of the Nusselt number and the wind Reynolds number with the shear Reynolds number, finding a communal transition at approximately $Re_{S}\approx 10^{5}$ from classical to ultimate turbulence with a transitional regime lasting at least up to $Re_{S}\geqslant 2\times 10^{5}$. Including the axial dispersion of the flow into the calculation of the wind amplitude, we can also investigate the wind Reynolds number as a function of the rotation ratio $\unicode[STIX]{x1D707}$, finding a maximum in the low counter-rotating regime slightly larger than $\unicode[STIX]{x1D707}_{max}$. Based on our study it becomes clear that the investigation of counter-rotating Taylor–Couette flows strongly requires an axial exploration of the flow.
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Gutierrez-Castillo, Paloma, and Juan M. Lopez. "Nonlinear mode interactions in a counter-rotating split-cylinder flow." Journal of Fluid Mechanics 816 (March 10, 2017): 719–45. http://dx.doi.org/10.1017/jfm.2017.103.
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The flow in a split cylinder with each half in exact counter rotation is studied numerically. The exact counter rotation, quantified by a Reynolds number $\mathit{Re}$ based on the rotation rate and radius, imparts the system with an $O(2)$ symmetry (invariance to azimuthal rotations as well as to an involution consisting of a reflection about the mid-plane composed with a reflection about any meridional plane). The $O(2)$ symmetric basic state is dominated by a shear layer at the mid-plane separating the two counter-rotating bodies of fluid, created by the opposite-signed vortex lines emanating from the two endwalls being bent to meet at the split in the sidewall. With the exact counter rotation, the additional involution symmetry allows for steady non-axisymmetric states, that exist as a group orbit. Different members of the group simply correspond to different azimuthal orientations of the same flow structure. Steady states with azimuthal wavenumber $m$ (the value of $m$ depending on the cylinder aspect ratio $\unicode[STIX]{x1D6E4}$) are the primary modes of instability as $\mathit{Re}$ and $\unicode[STIX]{x1D6E4}$ are varied. Mode competition between different steady states ensues, and further bifurcations lead to a variety of different time-dependent states, including rotating waves, direction-reversing waves, as well as a number of slow–fast pulse waves with a variety of spatio-temporal symmetries. Further from the primary instabilities, the competition between the vortex lines from each half-cylinder settles on either a $m=2$ steady state or a limit cycle state with a half-period-flip spatio-temporal symmetry. By computing in symmetric subspaces as well as in the full space, we are able to unravel many details of the dynamics involved.
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Li, Ting, Qing Jia, and Zhi Gang Yang. "The Influence of Rotating Wheels on Vehicle Aerodynamics." Applied Mechanics and Materials 246-247 (December 2012): 543–47. http://dx.doi.org/10.4028/www.scientific.net/amm.246-247.543.
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Full scaled simplified model and production vehicle were applied to make a research on the local and global flow characteristics. Two different conditions including stationary and rotation were employed in computational simulation by steady RNS Navier-Stokes calculation. Further, detailed analysis on flow, surface pressure coefficient, drag coefficient and lift coefficient affected by rotating wheel figure out that rotating wheel has a significant influence on the flow around wheel and vehicle. Pressure difference, drag coefficient and lift coefficient are decreased by rotation, which improve aerodynamic performance.
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Mittal, S. "Flow Past Rotating Cylinders: Effect of Eccentricity." Journal of Applied Mechanics 68, no. 4 (November 29, 2000): 543–52. http://dx.doi.org/10.1115/1.1380679.
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Computational results are presented for flows past a translating and rotating circular cylinder. A stabilized finite element method is utilized to solve the incompressible Navier-Stokes equations in the primitive variables formulation. To validate the formulation and its implementation certain cases, for which the flow visualization and computational results have been reported by other researchers, are computed. Results are presented for Re=5, 200 and 3800 and rotation rate, (ratio of surface speed of cylinder to the freestream speed of flow), of 5. For all these cases the flow reaches a steady state. The values of lift coefficient observed for these flows exceed the limit on the maximum value of lift coefficient suggested by Goldstein based on intuitive arguments by Prandtl. These observations are in line with measurements reported, earlier, by other researchers via laboratory experiments. To investigate the stability of the computed steady-state solution, receptivity studies involving an eccentrically rotating cylinder are carried out. Computations are presented for flow past a rotating cylinder with wobble; the center of rotation of the cylinder does not match its geometric center. These computations are also important from the point of view that in a real situation it is almost certain that the rotating cylinder will be associated with a certain degree of wobble. In such cases the flow is unsteady and reaches a temporally periodic state. However, the mean values of the aerodynamic coefficients and the basic flow structure are still quite comparable to the case without any wobble. In this sense, it is found that the two-dimensional solution is stable to purely two-dimensional disturbances.
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Ostilla-Mónico, Rodolfo, Erwin P. van der Poel, Roberto Verzicco, Siegfried Grossmann, and Detlef Lohse. "Exploring the phase diagram of fully turbulent Taylor–Couette flow." Journal of Fluid Mechanics 761 (November 18, 2014): 1–26. http://dx.doi.org/10.1017/jfm.2014.618.
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AbstractDirect numerical simulations of Taylor–Couette flow, i.e. the flow between two coaxial and independently rotating cylinders, were performed. Shear Reynolds numbers of up to $3\times 10^{5}$, corresponding to Taylor numbers of $\mathit{Ta}=4.6\times 10^{10}$, were reached. Effective scaling laws for the torque are presented. The transition to the ultimate regime, in which asymptotic scaling laws (with logarithmic corrections) for the torque are expected to hold up to arbitrarily high driving, is analysed for different radius ratios, different aspect ratios and different rotation ratios. It is shown that the transition is approximately independent of the aspect and rotation ratios, but depends significantly on the radius ratio. We furthermore calculate the local angular velocity profiles and visualize different flow regimes that depend both on the shearing of the flow, and the Coriolis force originating from the outer cylinder rotation. Two main regimes are distinguished, based on the magnitude of the Coriolis force, namely the co-rotating and weakly counter-rotating regime dominated by Rayleigh-unstable regions, and the strongly counter-rotating regime where a mixture of Rayleigh-stable and Rayleigh-unstable regions exist. Furthermore, an analogy between radius ratio and outer-cylinder rotation is revealed, namely that smaller gaps behave like a wider gap with co-rotating cylinders, and that wider gaps behave like smaller gaps with weakly counter-rotating cylinders. Finally, the effect of the aspect ratio on the effective torque versus Taylor number scaling is analysed and it is shown that different branches of the torque-versus-Taylor relationships associated to different aspect ratios are found to cross within 15 % of the Reynolds number associated to the transition to the ultimate regime. The paper culminates in phase diagram in the inner versus outer Reynolds number parameter space and in the Taylor versus inverse Rossby number parameter space, which can be seen as the extension of the Andereck et al. (J. Fluid Mech., vol. 164, 1986, pp. 155–183) phase diagram towards the ultimate regime.
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Habibi, Fahimeh. "Time dependence of advection-dominated accretion flow around a rotating compact object." Monthly Notices of the Royal Astronomical Society 498, no. 4 (September 10, 2020): 5952–59. http://dx.doi.org/10.1093/mnras/staa2739.
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ABSTRACT Time evolution of advection-dominated accretion flow (ADAF) around a rotating compact object is presented. The time-dependent equations of fluid including the Coriolis force along with the centrifugal and pressure gradient forces are derived. In this research, it is assumed that angular momentum transport is due to viscous turbulence and the α-prescription is used for the kinematic coefficient of viscosity. Moreover, the general relativistic effects are neglected. In order to solve the equations, we have used a self-similar solution. The solutions show that the behaviour of the physical quantities in a dynamical ADAF is different from that for a steady accretion flow. Our results indicate that the physical quantities are dependent of rotation parameter which is defined as the ratio of the intrinsic angular velocity of the central body to the angular velocity of disc. Also, the effect of rotation parameter on these quantities is different for co and counter-rotating flows. The solution shows that by increasing the rotation parameter a, inflow–outflow region approaches the central object for co-rotating flow and moves outwards for counter-rotating flow. We find that when flow is fully advection dominated (f → 1), the entire gas has positive Bernoulli function. Also, we suggest that the Bernoulli function becomes more positive when the effect of rotation on the structure of disc decreases.
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Song, Te, Xin Liu, and Feng Xu. "Moving Surface Boundary-Layer Control on the Wake of Flow around a Square Cylinder." Applied Sciences 12, no. 3 (February 4, 2022): 1632. http://dx.doi.org/10.3390/app12031632.
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In this paper, the entire process of the flow around a fixed square cylinder and the moving surface boundary-layer control (MSBC) at a low Reynolds number was numerically simulated. Two small rotating circular cylinders were located in each of the two rear corners of the square cylinder, respectively, to transfer momentum into the near wake behind the square cylinder. The rotations of the two circular cylinders were realized via dynamic mesh technology, when the two-dimensional incompressible Navier–Stokes equations for the flow around the square cylinder were solved. We analyzed the effects of different rotation directions, wind angles θ, and velocity ratios k (the ratio of the tangential velocity of the rotating cylinder to the incoming flow velocity) on the wake of flow around a square cylinder to evaluate the control effectiveness of the MSBC method. In the present work, the aerodynamic forces, the pressure distributions, and the wake patterns of the square cylinder are discussed in detail. The results show that the high suction areas near the surfaces of the rotating cylinders can delay or prevent the separation of the shear layer, reduce the wake width, achieve drag reduction, and eliminate the alternating vortex shedding. For a wind angle of 0°, the inward rotation of the small circular cylinders is the optimal arrangement to manipulate the wake vortex street behind the square cylinder, and k=2 is the optimal velocity ratio between the control effectiveness and external energy consumption.
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TSUKAHARA, T., N. TILLMARK, and P. H. ALFREDSSON. "Flow regimes in a plane Couette flow with system rotation." Journal of Fluid Mechanics 648 (April 7, 2010): 5–33. http://dx.doi.org/10.1017/s0022112009993880.
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Flow states in plane Couette flow in a spanwise rotating frame of reference have been mapped experimentally in the parameter space spanned by the Reynolds number and rotation rate. Depending on the direction of rotation, the flow is either stabilized or destabilized. The experiments were made through flow visualization in a Couette flow apparatus mounted on a rotating table, where reflected flakes are mixed with the water to visualize the flow. Both short- and long-time exposures have been used: the short-time exposure gives an instantaneous picture of the turbulent flow field, whereas the long-time exposure averages the small, rapidly varying scales and gives a clearer representation of the large scales. A correlation technique involving the light intensity of the photographs made it possible to obtain, in an objective manner, both the spanwise and streamwise wavelengths of the flow structures. During these experiments 17 different flow regimes have been identified, both laminar and turbulent with and without roll cells, as well as states that can be described as transitional, i.e. states that contain both laminar and turbulent regions at the same time. Many of these flow states seem to be similar to those observed in Taylor–Couette flow.
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Núñez, Manuel. "An Analytic Study of the Reversal of Hartmann Flows by Rotating Magnetic Fields." International Journal of Mathematics and Mathematical Sciences 2012 (2012): 1–15. http://dx.doi.org/10.1155/2012/641738.
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The effects of a background uniform rotating magnetic field acting in a conducting fluid with a parallel flow are studied analytically. The stationary version with a transversal magnetic field is well known as generating Hartmann boundary layers. The Lorentz force includes now one term depending on the rotation speed and the distance to the boundary wall. As one intuitively expects, the rotation of magnetic field lines pushes backwards or forwards the flow. One consequence is that near the wall the flow will eventually reverse its direction, provided the rate of rotation and/or the magnetic field are large enough. The configuration could also describe a fixed magnetic field and a rotating flow.
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Tang, Fei, and Li Jia Wen. "Characterization of Rotating Cavitation in a High Speed Inducer of Liquid Rocket Engine." Advanced Materials Research 320 (August 2011): 196–201. http://dx.doi.org/10.4028/www.scientific.net/amr.320.196.
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Rotating cavitation is one of the most important problems in the development of modern high performance rocket pump inducers. In this paper, a numerical simulation of rotating cavitation phenomenon in a 2D blade cascade of liquid rocket engine inducer was carried out using a mixture model based on Rayleigh-Plesset equation. The purpose is to investigate the characterization of rotating cavitation in a high speed inducer. The results show that when sub-synchronous rotating cavitation occurs, the speed for the length of the blade surface cavitation is lower than the speed frequency of rotation shaft with the same direction. The external aspect is that the pressure at the upstream of blades changes synchronous. Thus, the generation of sub-synchronous rotating cavitation is closely related to the changes of flow angel which caused by the flow fluctuations. Hence, elimination of the flow rate redistribution among the flow channel can effectively suppress the occurrence of this phenomenon.
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Patarashvili, K. I., Z. J. Tsakadze, M. V. Kalashnik, V. O. Kakhiani, R. J. Chanishvili, J. I. Nanobashvili, and M. A. Zhvania. "Topographic instability of flow in a rotating fluid." Nonlinear Processes in Geophysics 13, no. 2 (June 21, 2006): 231–35. http://dx.doi.org/10.5194/npg-13-231-2006.
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Abstract. Here are presented the results of experimental and theoretical studies on a stability of zonal geostrophic flows in the rotating layer of the shallow water. In the experiments, a special apparatus by Abastumani Astrophysical Observatory Georgian Academy of Science was used. This apparatus represents a paraboloid of rotation, which can be set in a regulable rotation around the vertical axis. Maximal diameter of the paraboloid is 1.2 m, radius of curvature in the pole is 0.698 m. In the paraboloid, water spreads on walls as a layer uniform on height under the period of rotation 1.677 s. Against a background of the rotating fluid, the zonal flows are formed by the source-sink system. It consists of two concentric circular perforations on the paraboloid bottom (width is 0.3 cm, radiuses are 8.4 and 57.3 cm, respectively); water can be pumped through them with various velocities and in all directions. It has been established that under constant vertical depth of the rotating fluid the zonal flows are stable. There are given the measurements of the radial profiles for the water level and velocity in the stationary regime. It has been found that zonal flows may lose stability under the presence of the radial gradient of full depth formed by a change of angular velocity of paraboloid rotation. An instability origin results in the loss of flow axial symmetry and in the appearance of self-excited oscillations in the zonal flow. At the given angular velocity of rotation, instability is observed only in the definite range of intensities of the source-sink system. The theoretical estimations are performed in the framework of the equations of the shallow water theory, including the terms describing the bottom friction. It has been shown that the instability of zonal flows found experimentally has a topographical nature and is related with non-monotone dependence of the potential vorticity on radius.
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Masanori, Kudo, Nishibe Koichi, Takahashi Masayuki, Sato Kotaro, Kang Donghyuk, and Yokota Kazuhiko. "1146 CHARACTERISTICS OF ROTATING FLOW DOWNSTREAM OF INLET GUIDE VANES." Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2013.4 (2013): _1146–1_—_1146–6_. http://dx.doi.org/10.1299/jsmeicjwsf.2013.4._1146-1_.
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Zhang, N., J. Chiou, S. Fann, and W. J. Yang. "Local Heat Transfer Distribution in a Rotating Serpentine Rib-Roughened Flow Passage." Journal of Heat Transfer 115, no. 3 (August 1, 1993): 560–67. http://dx.doi.org/10.1115/1.2910725.
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Experiments are performed to determine the local heat transfer performance in a rotating serpentine passage with rib-roughened surfaces. The ribs are placed on the trailing and leading walls in a corresponding posited arrangement with an angle of attack of 90 deg. The rib height-to-hydraulic diameter ratio, e/Dh, is 0.0787 and the rib pitch-to-height ratio, s/e, is 11. The throughflow Reynolds number is varied, typically at 23,000, 47,000, and 70,000 in the passage both at rest and in rotation. In the rotation cases, the rotation number is varied from 0.023 to 0.0594. Results for the rib-roughened serpentine passages are compared with those of smooth ones in the literature. Comparison is also made on results for the rib-roughened passages between the stationary and rotating cases. It is disclosed that a significant enhancement is achieved in the heat transfer in both the stationary and rotating cases resulting from an installation of the ribs. Both the rotation and Rayleigh numbers play important roles in the heat transfer performance on both the trailing and leading walls. Although the Reynolds number strongly influences the Nusselt numbers in the rib-roughened passage of both the stationary and rotating cases, Nuo and Nu, respectively, it has little effect on their ratio Nu/Nuo.
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Kang, Changwoo, Kyung-Soo Yang, and Innocent Mutabazi. "Thermal effect on large-aspect-ratio Couette–Taylor system: numerical simulations." Journal of Fluid Mechanics 771 (April 14, 2015): 57–78. http://dx.doi.org/10.1017/jfm.2015.151.
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We have performed numerical simulations of the flow in a large-aspect-ratio Couette–Taylor system with rotating inner cylinder and with a radial temperature gradient. The aspect ratio was chosen in such a way that the base state is in the conduction regime. Away from the endplates, the base flow is a superposition of an azimuthal flow induced by rotation and an axial flow (large convective cell) induced by the temperature gradient. For a fixed rotation rate of the inner cylinder in the subcritical laminar regime, the increase of the temperature difference imposed on the annulus destabilizes the convective cell to give rise to co-rotating vortices as primary instability modes and to counter-rotating vortices as secondary instability modes. The space–time properties of these vortices have been computed, together with the momentum and heat transfer coefficients. The temperature gradient enhances the momentum and heat transfer in the flow independently of its sign.
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Wang, Sha, Jixian Dong, Haozeng Guo, Lijie Qiao, Shulin Zhang, and Jianyong Wang. "Experimental study on condensation friction pressure drop in rotating channels and proposal of new correlation." Thermal Science, no. 00 (2022): 111. http://dx.doi.org/10.2298/tsci220313111w.
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The multi-channel cylinder dryer uses the small channels with high heat transfer efficiency to improve the drying efficiency. In practical working conditions, the multi-channel cylinder dryer runs under the rotating state, which would greatly affect the pressure drop of inside two-phase steam. However, the condensation friction pressure drop of two-phase flow in rotating channels has not been well explored. Here in, the condensation pressure drop of two-phase steam in rotating rectangular channels are elaborately studied based on a homemade rotating experiment system. The results show that the friction pressure drop of two-phase flow decreases with the increase of rotation Reynolds number, while increases with the increase of mass flux. Finally, a new correlation of friction pressure drop for two-phase flow condensation in rotating channels is proposed and evaluated by the experimental data.
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Hasan, Mohammad Sanjeed, Md Tusher Mollah, Dipankar Kumar, Rabindra Nath Mondal, and Giulio Lorenzini. "Effects of Rotation on Transient Fluid Flow and Heat Transfer Through a Curved Square Duct: The Case of Negative Rotation." International Journal of Applied Mechanics and Engineering 26, no. 4 (December 1, 2021): 29–50. http://dx.doi.org/10.2478/ijame-2021-0048.
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Abstract The fluid flow and heat transfer through a rotating curved duct has received much attention in recent years because of vast applications in mechanical devices. It is noticed that there occur two different types of rotations in a rotating curved duct such as positive and negative rotation. The positive rotation through the curved duct is widely investigated while the investigation on the negative rotation is rarely available. The paper investigates the influence of negative rotation for a wide range of Taylor number (−10 ≤ Tr ≤ −2500) when the duct itself rotates about the center of curvature. Due to the rotation, three types of forces including Coriolis, centrifugal, and buoyancy forces are generated. The study focuses and explains the combined effect of these forces on the fluid flow in details. First, the linear stability of the steady solution is performed. An unsteady solution is then obtained by time-evolution calculation and flow transition is determined by calculating phase space and power spectrum. When Tr is raised in the negative direction, the flow behavior shows different flow instabilities including steady-state, periodic, multi-periodic, and chaotic oscillations. Furthermore, the pattern variations of axial and secondary flow velocity and isotherms are obtained, and it is found that there is a strong interaction between the flow velocities and the isotherms. Then temperature gradients are calculated which show that the fluid mixing and the acts of secondary flow have a strong influence on heat transfer in the fluid. Diagrams of unsteady flow and vortex structure are further sketched and precisely elucidate the curvature effects on unsteady fluid flow. Finally, a comparison between the numerical and experimental data is discussed which demonstrates that both data coincide with each other.
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Chavanne, Cédric P., Eric Firing, and François Ascani. "Inertial Oscillations in Geostrophic Flow: Is the Inertial Frequency Shifted by ζ/2 or by ζ?" Journal of Physical Oceanography 42, no. 5 (May 1, 2012): 884–88. http://dx.doi.org/10.1175/jpo-d-12-031.1.
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Abstract The short answer to the question posed in the title is that it depends on the frame of reference chosen to describe the motions. In the inertial limit, the frequency in a rotating frame of reference corresponds to the rotation rate of the inertial current vectors relative to that frame. When described in a reference frame rotating with a geostrophic flow having a relative vertical vorticity ζ, inertial oscillations have a frequency f + ζ, equal to twice the fluid’s rotation rate around the local vertical axis. From a nonrotating frame of reference, one would measure only half this frequency; the other half arises from describing inertial motions in a reference frame rotating with the background flow. However, when described in a reference frame rotating with Earth, hence rotating at −ζ/2 relative to the geostrophic frame, inertial oscillations have a frequency reduced to f + ζ/2.
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Ueki, Yoshinori, and Katuhiko Tachibana. "Wavelet Analysis of Rotating Flow." Journal of the Visualization Society of Japan 17, Supplement1 (1997): 61–64. http://dx.doi.org/10.3154/jvs.17.supplement1_61.
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Donaghy-Spargo, C. "Rotating electrical machines: Poynting flow." European Journal of Physics 38, no. 5 (August 15, 2017): 055204. http://dx.doi.org/10.1088/1361-6404/aa7dcc.
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