Academic literature on the topic 'Constant speed flows'
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Journal articles on the topic "Constant speed flows"
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Holyoake, Alex J., and Jim N. McElwaine. "High-speed granular chute flows." Journal of Fluid Mechanics 710 (August 31, 2012): 35–71. http://dx.doi.org/10.1017/jfm.2012.331.
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AbstractThis paper reports experimental findings on the flow of sand down a steep chute. Nearly all granular flow models have a maximum value for the friction and therefore predict that flows on steep slopes will accelerate at a constant rate until the interaction with the ambient fluid becomes important. This prediction has not been tested by previous work, which has focused on relatively low slope angles where steady, fully developed flows occur after short distances. We test this by investigating flows over a much greater range of slope angles (30–50${}^{\ensuremath{\circ} } $) and flow depths (4–130 particle diameters). We examine flows with two basal conditions, one flat and frictional, the other bumpy. The latter imposes a no-slip condition for slow, deep flows, but permits some degree of slip for high flow velocities. The data suggests that friction can be much larger than theories such as the $\ensuremath{\mu} (I)$ rheology proposed by Jop, Forterre & Pouliquen (Nature, vol. 441, 2006) suggest and that there may be constant velocity states above the angle of vanishing ${h}_{\mathit{stop}} $. Although these flows do not vary in time, all but the flows on the bumpy base at low inclinations accelerate down the slope. A recirculation mechanism sustains flows with a maximum mass flux of $20~\mathrm{kg} ~{\mathrm{s} }^{\ensuremath{-} 1} $, allowing observations to be made at multiple points for each flow for an indefinite period. Flows with Froude number in the range 0.1–25 and bulk inertial number 0.1–2.7 were observed in the dense regime, with surface velocities in the range 0.2–5.6 $\mathrm{m} ~{\mathrm{s} }^{\ensuremath{-} 1} $. Previous studies have focused on $I\lessapprox 0. 5$. We show that a numerical implementation of the $\ensuremath{\mu} (I)$ rheology does not fully capture the accelerating dynamics or the transverse velocity profile on the bumpy base. We also observe the transverse separation of the flow into a dense core flanked by dilute regions and the formation of longitudinal vortices.
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Huang, Yangyang, Monika Nitsche, and Eva Kanso. "Hovering in oscillatory flows." Journal of Fluid Mechanics 804 (September 9, 2016): 531–49. http://dx.doi.org/10.1017/jfm.2016.535.
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We investigate the hovering dynamics of rigid bodies with up-down asymmetry placed in oscillating background flows. Recent experiments on inanimate pyramid-shaped objects in oscillating flows with zero mean component demonstrate that the resulting aerodynamic forces are sufficient to keep the object aloft. The mechanisms responsible for this lift production are fundamentally unsteady and depend on the shed vorticity. Here, we consider a model system of a two-dimensional flyer and compute the unsteady, two-way coupling between the flyer and the surrounding fluid in the context of the vortex sheet model. We examine in detail the flow properties (frequency and speed) required for hovering and their dependence on the flyer’s characteristics (mass and geometry). We find that, at low oscillation frequencies, a flyer of a fixed mass and shape requires a constant amount of flow acceleration to hover, irrespective of the frequency and speed of the oscillating flow. Meanwhile, at high oscillation frequencies, the flow speed required to hover is constant. In either case, the aerodynamic requirements to hover (flow acceleration or flow speed) are an intrinsic property of the flyer itself. This physical insight could potentially have significant implications on the design of unmanned air vehicles as well as on understanding active hovering of live organisms that can manipulate their flapping motion to favour a larger oscillation amplitude or frequency.
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Flack, Ronald D., Steven B. Ainley, Klaus Brun, and Leonard Whitehead. "Laser Velocimeter Measurements in the Pump of an Automotive Torque Converter Part II – Effect of Pump Speed and Oil Viscosity." International Journal of Rotating Machinery 6, no. 3 (2000): 181–90. http://dx.doi.org/10.1155/s1023621x00000178.
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The velocity field inside a torque converter pump was studied for two separate effects: variable pump rotational speed and variable oil viscosity. Three-dimensional velocity measurements were taken using a laser velocimeter for both the pump mid- and exit planes. The effect ofvariable pump rotational speed was studied by running the pump at two different speeds and holding speed ratio (pump rotational speed]turbine rotational speed) constant. Similarly, the effect of viscosity on the pump flow field was studied by varying the temperature and]or using two different viscosity oils as the working fluid in the pump. Threedimensional velocity vector plots, through-flow contour plots, and secondary flow profiles were obtained for both pump planes and all test conditions. Results showed that torque converter mass flows increased approximately linearly with increasing pump rotational speed (and fixed speed ratio) but that the flow was not directly proportional to pump rotational speed. However, mass flows were seen to decrease as the oil viscosity was decreased with a resulting increased Reynolds number; for these conditions the high velocity regions were seen to decrease in size and low velocity regions were seen to increase in size. In the pump mid-plane strong counter-clockwise secondary flows and in the exit plane strong clockwise secondary flows were observed. The vorticities and slip factors were calculated from the experimental results and are presented. The torque core-to-shell and blade-to-blade torque distributions were calculated for both planes. Finally, the flow fields were seen to demonstrate similitude when Reynolds numbers were matched.
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GARRETT, CHRIS, and FRANK GERDES. "Hydraulic control of homogeneous shear flows." Journal of Fluid Mechanics 475 (January 25, 2003): 163–72. http://dx.doi.org/10.1017/s0022112002002884.
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If a shear flow of a homogeneous fluid preserves the shape of its velocity profile, a standard formula for the condition for hydraulic control suggests that this is achieved when the depth-averaged flow speed is less than (gh)1/2. On the other hand, shallow-water waves have a speed relative to the mean flow of more than (gh)1/2, suggesting that information could propagate upstream. This apparent paradox is resolved by showing that the internal stress required to maintain a constant velocity profile depends on flow derivatives along the channel, thus altering the wave speed without introducing damping. By contrast, an inviscid shear flow does not maintain the same profile shape, but it can be shown that long waves are stationary at a position of hydraulic control.
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Wang, B. Y., and I. I. Glass. "Boundary layer flows behind constant speed shock waves moving into a dusty gas." Shock Waves 1, no. 2 (June 1991): 135–44. http://dx.doi.org/10.1007/bf01414908.
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BOWERSOX, RODNEY D. W. "Extension of equilibrium turbulent heat flux models to high-speed shear flows." Journal of Fluid Mechanics 633 (August 25, 2009): 61–70. http://dx.doi.org/10.1017/s0022112009007691.
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An algebraic heat flux truncation model was derived for high-speed gaseous shear flows. The model was developed for high-temperature gases with caloric imperfections. Fluctuating dilatation moments were modelled via conservation of mass truncations. The present model provided significant improvements, up to 20%, in the temperature predictions over the gradient diffusion model for a Mach number ranging from 0.02 to 11.8. Analyses also showed that the near-wall dependence of the algebraic model agreed with expected scaling, where the constant Prandtl number model did not. This led to a simple modification of the turbulent Prandtl number model. Compressibility led to an explicit pressure gradient dependency with the present model. Analyses of a governing parameter indicated that these terms are negligibly small for low speeds. However, they may be important for high-speed flow.
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Kim, YC, Y. Tamura, A. Yoshida, T. Ito, W. Shan, and Q. Yang. "Experimental investigation of aerodynamic vibrations of solar wing system." Advances in Structural Engineering 21, no. 15 (May 7, 2018): 2217–26. http://dx.doi.org/10.1177/1369433218770799.
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The general characteristics of aerodynamic vibrations of a solar wing system were investigated through wind tunnel tests using an aeroelastic model under four oncoming flows. In total, 12 solar panels were suspended by cables and orientated horizontally. Distances between panels were set constant. Tests showed that the fluctuating displacement increases proportionally to the square of the mean wind speed for all wind directions in boundary-layer flows. Larger fluctuating displacements were found for boundary-layer flows with larger power-law indices. Under low-turbulence flow, the fluctuating displacement increased proportionally to the square of the mean wind speed for wind directions between 0° and 30°, but an instability vibration was observed at high mean wind speed for wind directions larger than 40°. And when the wind direction was larger than 60°, a limited vibration was observed at low mean wind speed and the instability vibration was also observed at high mean wind speed. Fluctuating displacements under grid-generated flow showed a similar trend to that of the boundary-layer flows, although the values became much smaller.
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Venkateswaran, S. "Experimental Study of Casing Boundary Layers in a Multistage Axial Compressor." Journal of Fluids Engineering 113, no. 2 (June 1, 1991): 240–44. http://dx.doi.org/10.1115/1.2909486.
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Measurements of the casing boundary layers were obtained in a four-stage, low speed axial flow compressor, to verify the ‘law of the wall’ applicability to these complex flows. Some of the available shear stress models of the two-dimensional flows have been examined towards the quantitative assessment of skin friction. The shear stress prediction obtained from the Ludwieg-Tillmann relation applied to the streamwise or untwisted profile agreed closely with the measured shear stress by the hot wire. The skin friction was fairly constant for rotor and stator flows and was close to the flat plate values. The boundary layer profiles exhibited a well pronounced semi-logarithmic region with the universal constants of the law of the wall far removed from the standard two dimensional values, especially for rotor flows. Stator flows showed signs of similarity to two dimensional flows.
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WYLIE, JONATHAN J., and HUAXIONG HUANG. "Extensional flows with viscous heating." Journal of Fluid Mechanics 571 (January 4, 2007): 359–70. http://dx.doi.org/10.1017/s0022112006003338.
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In this paper we investigate the role played by viscous heating in extensional flows of viscous threads with temperature-dependent viscosity. We show that there exists an interesting interplay between the effects of viscous heating, which accelerates thinning, and inertia, which prevents pinch-off. We first consider steady drawing of a thread that is fed through a fixed aperture at given speed and pulled with a constant force at a fixed downstream location. For pulling forces above a critical value, we show that inertialess solutions cannot exist and inertia is crucial in controlling the dynamics. We also consider the unsteady stretching of a thread that is fixed at one end and pulled with a constant force at the other end. In contrast to the case in which inertia is neglected, the thread will always pinch at the end where the force is applied. Our results show that viscous heating can have a profound effect on the final shape and total extension at pinching.
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ZHU, DAVID Z., and GREGORY A. LAWRENCE. "Holmboe's instability in exchange flows." Journal of Fluid Mechanics 429 (February 25, 2001): 391–409. http://dx.doi.org/10.1017/s002211200000286x.
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A laboratory study of the exchange of two fluids of different density through a constant-width channel with an underwater sill has enabled us to study Holmboe's instability in greater detail than has been possible in mixing-layer experiments. The internal hydraulics of the exchange flow are such that we have been able to observe the initiation of instability, the development and behaviour of both symmetric and asymmetric Holmboe instabilities, and the suppression of the instability at bulk Richardson numbers above about 0.7. A number of stability criteria resulting from previous numerical investigations have been verified experimentally. Our laboratory measurements are consistent with theoretical predictions of wave speed and wavenumber.
Dissertations / Theses on the topic "Constant speed flows"
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Grice, Glenn Noel Mathematics UNSW. "Constant speed flows and the nonlinear Schr??dinger equation." Awarded by:University of New South Wales. Mathematics, 2004. http://handle.unsw.edu.au/1959.4/20509.
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This thesis demonstrates how the geometric connection between the integrable Heisenberg spin equation, the nonlinear Schr??dinger equation and fluid flows with constant velocity magnitude along individual streamlines may be exploited. Specifically, we are able to construct explicitly the complete class of constant speed flows where the constant pressure surfaces constitute surfaces of revolution. This class is undoubtedly important as it contains many of the specific cases discussed earlier by other authors.
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Akiyama, Shinsaku. "Measurement of the flow past a sphere descending at a constant speed in a salt stratified fluid." Kyoto University, 2018. http://hdl.handle.net/2433/235086.
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Guillou, Arnaud. "Détermination de la constante de Boltzmann au plus haut niveau d’exactitude par spectroscopie acoustique dans un résonateur quasi sphérique : Vers une nouvelle définition de l’unité internationale de température." Thesis, Paris, CNAM, 2012. http://www.theses.fr/2012CNAM0843/document.
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Depuis 2005, il existe un intérêt important dans la communauté internationale de métrologiepour de nouvelles déterminations précises de la constante de Boltzmann kB ; lebut étant de redéfinir en 2015 l’unité internationale de température, le kelvin. Actuellement,cinq techniques sont utilisées pour déterminer kB avec comme objectif d’atteindreune incertitude relative inférieure à 1 × 10−6. La méthode retenue pour cette thèse est latechnique acoustique.La constante de Boltzmann est liée à la vitesse du son u dans un gaz parfait par l’équationdu viriel acoustique. La méthode décrite dans cette thèse consiste à mesurer u en utilisantun résonateur de forme quasi sphérique et de volume intérieur de 0,5 L, rempli d’argon.Ces mesures sont effectuées lors d’un isotherme à la température du point triple de l’eau,T = 273,16 K, pour des pressions statiques P allant de 0,05 MPa à 0,7 MPa. La constantede Boltzmann est ensuite déterminée en estimant u à pression nulle par une régressionpolynomiale.Dans cette thèse, un modèle de propagation des ondes acoustiques dans un résonateur quasisphérique est défini. Aussi, les moyens techniques utilisés pour contrôler soigneusement lesparamètres de l’expérience qui ont un effet sur les mesures de u (comme la température,la pression statique, la composition du gaz, etc) sont présentés. De nouvelles techniquesexpérimentales et des nouveaux moyens d’analyse des données sont proposés, comme lamesure du rayon du résonateur par spectroscopie électromagnétique, mais aussi l’utilisationde l’écart-type d’Allan comme un outil efficace pour étudier la présence d’impuretélors d’une expérience de longue durée. Les effets systématiques sont analysés puis corrigés.Pour certains, la correction est estimée grâce à un modèle analytique, comme l’effet lié auxcouches limites thermiques. Pour d’autres, des corrections basées sur des fonctions empiriquessont proposées ; c’est le cas pour l’effet du débit de gaz continu sur les mesures deu, effet qui est caractérisé expérimentalement dans cette thèse.Enfin, l’analyse des données acquises en 2009 au LCM/LNE-CNAM lors de deux isothermeseffectuées avec de l’argon est présentée. Celle-ci a permis d’obtenir la valeur kB =1, 3806475 (16) × 10−23 J · K−1, c’est à dire avec une incertitude relative de 1, 14 × 10−6Since 2005, there is an important interest in the international metrology community fornew accurate determinations of the Boltzmann constant kB ; the purpose is to redefine in2015 the unit of thermodynamic temperature, the kelvin. Currently, five techniques areimplemented for determining kB with the objective to achieve a relative uncertainty below1 × 10−6. The method used in the present work is based on acoustic measurements.The Boltzmann constant is linked to the speed of sound u in a noble gas by the virial acousticalequation. The method described here consists in measuring u inside a quasi-sphericalacoustic resonator of inner volume of 0.5 L filled with argon. Measurements are performedduring an isotherm process at the temperature of the triple point of water, T = 273.16 K,at static pressures P from 0.05 MPa to 0.7 MPa. The Boltzmann constant is then determinedby estimating u at zero pressure limit with a polynomial regression.In the present work an acoustic wave propagation model within a quasi-spherical resonatoris defined. Also, the technical means used to carefully control the parameters of theexperiment with an effect on the measurement of u (like temperature, static pressure, gascomposition, etc.) are presented. New exprimental methods and data analyses are described,like the measurement of the radius of the resonator by electromagnetic spectroscopy,as well as the use of the Allan deviation as an efficient tool to study the gas impuritypresence during a long-term experience. Systematic effects are analyzed and corrected. Insome cases the corrections are based on analytical models like the thermal layer boundaryeffect. In other cases, empirical correction functions are proposed, as for the case of changesin the measurements of u related to the continuous gas flow, which was experimentally characterizedin the present work.Finally, the analysis of the data acquiered in 2009 at LCM/LNE-CNAM during two isothermprocesses using argon is presented. This leads to the value kB = 1.3806475 (16) ×10−23 J · K−1, i.e. with a relative uncertainty of 1.14 × 10−6
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WU, DENG-YUAN, and 吳登淵. "Optimization of wing structures in subsonic flow under flutter speed constraint." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/80168159350938328520.
Full textBooks on the topic "Constant speed flows"
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Wang, B. Y. Boundary layer flows behind constant speed shock waves moving into a dusty gas. [S.l.]: [s.n.], 1991.
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Rajeev, S. G. Ideal Fluid Flows. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198805021.003.0004.
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Some solutions of Euler’s equations are found here. The simplest are the steady flows: water flowing out of a tank at a constant rate, the Venturi and Pitot tubes. Another is the static solution of a self-gravitating fluid of variable density (e.g., a star). If the total mass is too large, such a star can collapse (Chandrasekhar limit). If the flow is both irrotational and incompressible, it must satisfy Laplace’s equation. Complex analysismethods can be used to solve for the flow past a cylinder or inside a disk with a stirrer. Joukowski used conformal transformations on the cylinder to find the lift of the wing of an airplane, in the limit of zero viscosity. Waves on the surface of a fluid are studied as another example. The speed of these waves is derived as a function of their wavelength and the depth of the fluid.
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Rajeev, S. G. Euler’s Equations. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198805021.003.0002.
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Euler derived the fundamental equations of an ideal fluid, that is, in the absence of friction (viscosity). They describe the conservation of momentum. We can derive from it the equation for the evolution of vorticity (Helmholtz equation). Euler’s equations have to be supplemented by the conservation of mass and by an equation of state (which relates density to pressure). Of special interest is the case of incompressible flow; when the fluid velocity is small compared to the speed of sound, the density may be treated as a constant. In this limit, Euler’s equations have scale invariance in addition to rotation and translation invariance. d’Alembert’s paradox points out the limitation of Euler’s equation: friction cannot be ignored near the boundary, nomatter how small the viscosity.
Book chapters on the topic "Constant speed flows"
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Chatterjee, Krishnendu, Amir Kafshdar Goharshady, Rasmus Ibsen-Jensen, and Andreas Pavlogiannis. "Optimal and Perfectly Parallel Algorithms for On-demand Data-Flow Analysis." In Programming Languages and Systems, 112–40. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44914-8_5.
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AbstractInterprocedural data-flow analyses form an expressive and useful paradigm of numerous static analysis applications, such as live variables analysis, alias analysis and null pointers analysis. The most widely-used framework for interprocedural data-flow analysis is IFDS, which encompasses distributive data-flow functions over a finite domain. On-demand data-flow analyses restrict the focus of the analysis on specific program locations and data facts. This setting provides a natural split between (i) an offline (or preprocessing) phase, where the program is partially analyzed and analysis summaries are created, and (ii) an online (or query) phase, where analysis queries arrive on demand and the summaries are used to speed up answering queries.In this work, we consider on-demand IFDS analyses where the queries concern program locations of the same procedure (aka same-context queries). We exploit the fact that flow graphs of programs have low treewidth to develop faster algorithms that are space and time optimal for many common data-flow analyses, in both the preprocessing and the query phase. We also use treewidth to develop query solutions that are embarrassingly parallelizable, i.e. the total work for answering each query is split to a number of threads such that each thread performs only a constant amount of work. Finally, we implement a static analyzer based on our algorithms, and perform a series of on-demand analysis experiments on standard benchmarks. Our experimental results show a drastic speed-up of the queries after only a lightweight preprocessing phase, which significantly outperforms existing techniques.
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Kennel, Charles F. "Bursty Magnetopause Reconnection and its Consequences." In Convection and Substorms. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195085297.003.0011.
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There is at least one way in which the reconnection model of substorms is unrealistic. Rarely if ever will the interplanetary field rotate southward, stay southward, and remain constant. Even on those infrequent occasions when it does do so, steady reconnection may not be established on the dayside: We will see that dayside reconnection proceeds in bursts even then. How likely is it then that steady convection will be established on the nightside? In the next two chapters, we will fit together observations of bursty convection at the magnetopause, in the polar cap and auroral ionosphere, at various distances downtail in the plasma sheet, and beyond the average position of the neutral line in the deep tail. In this chapter, we deal with unsteady magnetopause reconnection. We start with one simple observation: The magnetopause is a source of escaping particles with energies higher than can be generated by the average convection potential across the ionosphere (Section 8.2). This, together with the fact that high-speed magnetopause flows can turn on and off between successive magnetopause crossings only minutes apart, suggests that the rate of reconnection is high for short periods of time and low for longer intervals. When the reconnection events are shorter than or comparable to MHD wave propagation times to the ionosphere, we call the reconnection “bursty.” We then let observation define the properties of bursty magnetopause reconnection. First, we discuss “flux transfer events” (FTEs), the traveling magnetic perturbations near the magnetopause (Section 8.3) that are signatures of bursty reconnection elsewhere on the magnetopause (Section 8.4). The magnitudes of the fluxes reconnected in FTEs are estimated in Section 8.5. Next, we discuss some of the ionospheric signatures of flux transfer events that might be expected on general theoretical grounds (Section 8.6). Variable dayside reconnection could be responsible for ULF magnetic activity in the polar cusp region (Section 8.7). We expect sudden magnetopause reconnection events to send Alfven waves (Section 8.8) and velocity-dispersed ions along field lines towards the polar cusp ionosphere (Section 8.9).
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Lighton, John R. B. "Flow-through Respirometry: The Basics." In Measuring Metabolic Rates, 71–93. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198830399.003.0008.
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This chapter describes the basic theory behind the most widely used method for measuring metabolic rates: flow-through or open-system respirometry. The advantages and disadvantages of the technique are summarized and the two major types of flow-through respirometry systems are described. Recommendations are given on choosing an appropriate flow rate to compromise between speed of response and signal amplitude; on the nature and importance of the cage time-constant; on using mathematical techniques for response correction by compensating for first-order wash-out kinetics and avoiding mixing errors; the essential differences between oxygen and carbon dioxide analysis; choosing a data acquisition system; generating and measuring flow rates; removing or mathematically compensating for water vapor; important tools; and checklists for deciding on system configuration for a given investigation.
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Cantor, Brian. "Fick’s Laws." In The Equations of Materials, 141–61. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198851875.003.0007.
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Atoms and molecules are not completely immobile within a solid material. They move by jumping into vacancies or interstitial sites in the crystal lattice. The laws describing their motion were discovered by Adolf Fick in the mid-19th century, modelled on analogous laws for the flow of heat (Fourier’s law) and electricity (Ohm’s law). According to Fick’s first law, the rate at which atoms move is proportional to the concentration gradient, with the diffusion coefficient defined as the constant of proportionality. Fick’s second law generalises the first law to a wide range of situations and is called the diffusion equation. This chapter examines a number of characteristic diffusion profiles; the difference between self, intrinsic, inter- and tracer diffusion coefficients; the Kirkendall effect and porosity formation when different components move at different speeds; and the Arrhenius temperature dependence of diffusion. Fick was a physiologist and derived his laws initially to describe the flow of blood through the heart. He made advances in anatomy, physiology and medicine, developing methods of monitoring blood pressure, muscular power, corneal pressure and glaucoma. He lived at the time of Bismarck’s post-Napoléonic unification of Germany and the associated flowering of German science, engineering, medicine and culture.
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Nikolaev, Evgeny, and Maria Nikolaeva. "Discrete Vortex Cylinders Method for Calculating the Helicopter Rotor-Induced Velocity." In Vortex Dynamics Theories and Applications. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93186.
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A new vortex model of a helicopter rotor with an infinite number of blades is proposed, based on Shaidakov’s linear disk theory for calculating inductive speeds at any point in space in the helicopter area. It is proposed to consider the helicopter rotor and the behind vortex column as a system of discrete vortex cylinders. This allows building a matrix of the influence of the vortex system under consideration on any set of points, for example, the calculated points on the rotor itself, on the tail rotor, etc. The model allows calculating inductive velocities at any point near the helicopter using matrix multiplication operation. It is shown that the classical results for the momentum theory remain constant even in the discrete simulation of the helicopter rotor vortex system. The structure of the air flow behind the rotor and the simulation results obtained by the proposed method is compared with the structure of the tip vortices and the results of the blade vortex theory. In addition, the experimental data were compared with the simulation results to verify the correctness of the model under real operating conditions by the helicopter trimming.
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Han, Chang Dae. "Wire-Coating Extrusion." In Rheology and Processing of Polymeric Materials: Volume 2: Polymer Processing. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195187830.003.0010.
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The process of coating a wire with a polymeric material is basically an extrusion operation in which either the molten polymer is extruded continuously over an axially moving wire or the wire is pulled through the extruded molten polymer. As schematically shown in Figure 5.1, the typical wire-coating unit consists of a pay-off device, a wire preheater, an extruder equipped with a cross-head die, a cooling trough, and a take-off device. Various control and measuring instruments are utilized in the commercial line (Griff 1962). The two basic wire-coating dies are pressure-type dies and tubing-type dies, as shown schematically in Figure 5.2. The tubing-type dies are annular in cross-section. The flow geometry outside the tubing die is important from the point of view of obtaining a coating with better mechanical and electrical properties and surface smoothness. However, little effort has been spent on studying this particular aspect of the process. The pressure-type wire-coating die is an annulus, the side surface of which is the wire to be coated, moving at a constant speed. The flow through this type of die is analogous to the flow through an annulus formed by coaxial cylinders with the inner cylinder moving in the axial direction. In the past, analysis of wire-coating extrusion for pressure-type die has been carried out for Newtonian and power-law fluids (Bagley and Storey 1963; Bernhardt 1962; Carley et al. 1979; Han and Rao 1978; McKelvey 1963). Like in the film coextrusion process presented in Chapter 9, in wire-coating coextrusion two different polymers may be concentrically coated on the wire in a single step (LeNir 1974). Tough abrasive-resistant nylon, for example, can be coated over a much less expensive polyethylene core, or one can have a thin coat of color compound over unpigmented insulator, thus taking advantage of the different properties of two components at a reduced cost. Considerable savings in the cost of processing can be achieved by applying two coats in a single step.
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Lienhard, John H. "Looking Inside the Inventive Mind." In The Engines of Our Ingenuity. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195135831.003.0005.
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An inventor—any creative person—knows to look under the surface of what things seem to be, to learn what they are. I have been able to find only one constant in the creative mind. It is that surprise is the hidden face of the coin of invention. In their operetta Pinafore, Gilbert and Sullivan warn us: . . . Things are seldom what they seem, Skim milk masquerades as cream; Highlows pass as patent leathers; Jackdaws strut in peacock’s feathers. . . . For example, an engineer designing a highway system wants to include crossroads between the major arteries. Common sense says that crossroads will increase driver options and speed traffic. Only very keen insight, or a complex computer analysis, reveals that crossroads tend to make matters worse. They often create localized traffic jams where none would otherwise occur. We are caught off guard when common sense fails us. Yet it is clear we would live in a deadly dull world if common sense alone were sufficient to lead us through all the mazes around us. If what we learn is no more than what we expect to learn, then we have learned nothing at all. Sooner or later, every student of heat flow is startled to find out that insulation on a small pipe can sometimes increase heat loss. Common sense is the center of gravity we return to after our flights of fancy. But it is the delicious surprise—the idea that precedes expectation—that makes science, technology, and invention such a delight. A wonderful old expression calls creativity “a fine madness,” and it is. Invention lies outside the common ways and means. If it is sane to respond predictably to reality, then invention surely is madness. A well-known riddle shows us something of the way that madness works. You are asked to connect nine dots, in a square array, with four straight lines. Each line has to continue from the end of the last line. The problem seems to have no solution.
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Walker, James C. G. "How to Calculate a Compositional History." In Numerical Adventures with Geochemical Cycles. Oxford University Press, 1991. http://dx.doi.org/10.1093/oso/9780195045208.003.0004.
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The most interesting theoretical problems in Earth system science cannot be solved by analytical methods; their solutions cannot be expressed as algebraic expressions; and so numerical solutions are needed. In this chapter I shall introduce a method of numerical solution that can be applied to a wide range of simulations and yet is easy to use. In later chapters I shall elaborate and apply this method to a variety of situations. All numerical solutions of differential equations involve some degree of approximation. Derivatives—properly defined in terms of infinitesimally small increments—are approximated by finite differences: dy/dx is approximated by dely/delx, whose accuracy increases as the finite difference, delx, is reduced. A large value of delx may even cause numerical instability, yielding a numerical solution that is altogether different from the true solution of the original system of differential equations. But a small value of delx generally implies that many steps must be taken to evolve the solution from a starting value of x to a finishing value. A numerical solution, therefore, requires a trade-off between computational speed and accuracy. We seek an efficient and stable method of calculation that provides accuracy appropriate to our knowledge of the physical system being simulated. The problem described in this chapter can be easily solved analytically, and the analytical solution serves as a check on the accuracy of the numerical solutions. As a simple example of a global geochemical simulation, consider the exchange of carbon dioxide between the ocean and the atmosphere. The atmosphere contains 5.6 × 1016 moles of carbon dioxide (cf. Walker, 1977), a quantity that I assume to be in equilibrium with the ocean. In this illustration I assume that the oceanic reservoir is very large and therefore does not change with time. According to Broecker and Peng (1982, p. 680) the annual exchange of carbon dioxide between ocean and atmosphere is 6.5 × 1015 moles. The rate of transfer from atmosphere to ocean is proportional to the amount in the atmosphere; the flow from ocean to atmosphere is constant. Figure 2-1 summarizes this system. The amount of carbon dioxide in the atmosphere is proportional to the partial pressure.
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Louvros, Spiros. "Towards Unified Services in Heterogeneous Wireless Networks Based on Soft-Switch Platform." In Encyclopedia of Multimedia Technology and Networking, Second Edition, 1416–22. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-014-1.ch191.
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The last two decades, after the telecommunication and computer technology convergence, the world of telecommunication applications has changed dramatically. The traffic needs of the customers have moved from circuit switched applications towards packet switched applications (Cox, 1995). Data traffic, with the characteristics of information transmission in the form of packets and the bursty flow characteristics rather than constant rate, nowadays accounts for slightly more than 60% of the traffic that is transmitted over the backbone telecommunication networks (Esmailzadeh, Nakagawa, & Jones, 2003). In addition to data traffic, multimedia applications like video calls, IP TV, and multimedia messaging traffic (variable rate with real time constraints) was made possible by low cost video digitizing equipment (Houssos, Alonistioti, Merakos, Mohyeldin, Dillinger, Fahrmair, & Schoenmakers, 2003). Different Radio Access Technology (RAT) networks offer different services to their subscribers. This is a big problem for the multimedia industry since it poses certain constraints to the subscribers regarding specific technology handsets. The ideal solution might be a unified handset with a unified service subscriber identity module (SIM) card (Louvros & Iossifides, 2004). This handset should be able to access the service by any radio access network, like Global System Mobile (GSM) (Siegmund, Redl, Weber, & Oliphant, 1995), General Packet Radio System (GPRS), Universal Mobile Telecommunications System (UMTS), and IEEE802.11 standard (WiFi or WLAN) towards a common core platform. In order to achieve such a unification, the service request should be seamless to the radio access technology network and the core platform should support certain protocols to provide again seamless to the user access to the requested service. Such a platform is already designed and is known as the soft-switch solution. The idea behind the soft-switch solution is the layering of the core network management procedures (mobility management, call control, session management, charging) in such a way that the operator can support all requests as a unified routing process. Moreover the operator can deploy its core switch and transmission network based on a common backbone, designed according to the 3GPP standards on IP or ATM infrastructure, and also to be able to accommodate in the future any new radio access technology network simply and without any serious rearrangement of the existing backbone, thus eliminating cost implementation. Asynchronous Transfer Mode (ATM) technology is proposed by the telecommunication industry to accommodate multiple traffic types (packet and voice) in a high speed wire-line backbone network. Briefly, ATM is based on very fast (on the order of 2.5 Gbits/sec or higher (Q.2931 ATM Network Signaling Specification, ITU)) packet switching technology with 53 byte long packets called cells being transmitted through wireline networks running usually on fiber optical equipment (Louvros, Karaboulas, Iossifides, & Kotsopoulos, 2003).
Conference papers on the topic "Constant speed flows"
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Tuncer, Onur. "Cavity Flame Holding for High Speed Reacting Flows." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-25081.
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Combustion phenomena in a ramjet combustor with cavity flame-holder is studied numerically. Combustor follows a constant area isolator and comprises of hydrogen fuel injected sonically upstream of the cavity. Secondary fuel injection is performed at the cavity backwall. A diverging section follows the cavity to prevent thermal choking. These concepts are also utilized in practice. Calculations were performed for an entrance Mach number of 1.4. Stagnation temperature is 702 K, corresponding to a flight Mach number of 3.3 at an altitude of 12.5 km. Detailed chemical kinetics are taken into account with a reaction mechanism comprising of 9 species and 25 reaction steps. Turbulence is modeled using Menter’s k–ω shear stress transport model, which is appropriate for high speed internal flows. It is observed that flame anchors at the leading edge of the cavity, and the flame is stabilized in the cavity mode rather than the jet-wake mode. Numerical simulation captures all the essential features of the reacting flowfield.
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Shields, Allison, Swetadri Vasan Setlur Nagesh, Ciprian Ionita, Daniel Bednarek, and Stephen Rudin. "Characterization of velocity patterns produced by pulsatile and constant flows using 1000 fps high-speed angiography (HSA)." In Biomedical Applications in Molecular, Structural, and Functional Imaging, edited by Barjor S. Gimi and Andrzej Krol. SPIE, 2021. http://dx.doi.org/10.1117/12.2580888.
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Lee, Kuen-Bae, Mark Wilson, and Mehdi Vahdati. "Validation of a Numerical Model for Predicting Stalled Flows in a Low-Speed Fan." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63245.
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This paper investigates the rotating stall for a low-speed/low-pressure ratio fan blade. The type of stall studied in this paper is similar to the multi cell, part span rotating stall, which can occur on the front stages of the core compressors. Although this type of rotating stall may not result in surge or massive loss of power, it can cause excessive vibration and noise. It was found that the standard Spalart-Allmaras (SA) model implemented in the CFD solver used in this work predicts premature stall, which is in line with the observation of other researchers who use the SA model. Therefore, to improve the prediction of the stall boundary, the standard SA model was modified by scaling the source term in the model based on the local pressure gradient and the velocity helicity of the flow. Furthermore, a generalized wall function valid for non-zero wall pressure gradient was implemented to improve the accuracy of boundary conditions at the wall. The turbulence modelling part of this work aims to produce a turbulence model which can be used to model the flows near the stall boundary for the transonic fan blades on relatively coarse grids of around 300k points per passage. Initially, two fan blades with different design and operating speeds were used to optimize the new parameters in the modified turbulence model. The optimization was based on improving the correlation between measured and numerical radial profiles of the pressure ratio. Thereafter, steady computations were performed for two other blades (with the same parameters) and the predictions were compared with the experimental data for all the four fan blades. Numerical results showed a significant improvement over those obtained with the original SA model, when compared against the measured data. In the second part, the modified turbulence model was used to study the flow near the stalled region. Three-dimensional, whole assembly unsteady simulations were performed for a modern low speed fan rig for which extensive measured data were available. Stall simulations were conducted at 80% speed, which contained a part with positive slope on the measured constant speed characteristic. The results indicated that by using an unsteady whole assembly approach and the modified turbulence model, it is possible to predict the flow for all the points on the measured constant speed characteristic (including those on the positive slope part).
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Arthurs, David, and Samir Ziada. "The Effect of Fluid-Resonant Coupling in High-Speed Impinging Planar Jet Flows." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97141.
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This study investigates the effect of fluid-resonant coupling, i.e. the coupling between unstable modes of an impinging jet with resonant acoustic modes occurring between the nozzle and the impingement surface, on the self-excited oscillations of high-speed impinging planar jet. In order to investigate this phenomenon, a series of experiments have been performed using a high-speed impinging planar jet with varying nozzle thickness (h) and impingement distance (xo), for a single Mach number in the compressible flow regime. The test results reveal that the jet oscillation is controlled by a fluid-dynamic mechanism for small impingement distances, where the unstable mode of the jet is controlled by the impingement ratio. At larger impingement distances, the response is dominated by a fluid-resonant mechanism, in which the various hydrodynamic modes of the jet couple with different resonant acoustic modes occurring between the nozzle and the impingement surface. Within the fluid-resonant regime the system produces acoustic tones that are excited predominantly as a function of the impingement distance, with the nozzle thickness and impingement ratio having only minor effects on the tone frequency. Flow visualization images show that the same unstable mode is excited for multiple nozzle thicknesses at a constant impingement distance, despite the wide variations in associated impingement ratio.
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James, Jintu K., and Heuy Dong Kim. "Multiple Shock Waves and its Unsteady Characteristics in Internal Flows." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5087.
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Abstract Shock wave turbulent boundary layer interaction is a fundamental phenomenon observed in most of the gas dynamics applications such as wind tunnels, supersonic air intakes, transonic airfoil, nozzle flows, etc. The flow field and shock wave pattern in a constant area duct are analyzed experimentally. The focus of the present study is to present the time-resolved flow characteristics of the multiple shock waves and its oscillations. High-speed Schlieren flow visualization is used to capture the transient shock structure in the wind tunnel constant area test section. A gradient-based image processing was incorporated to capture the shock excursion details. Results indicate that the shock pattern is unsymmetrical in the flow field. The foot of the lambda shock wave in the upper and lower exhibit a difference in axial location and there is a large difference in this value at the mean position when the shock moves in the upstream direction compared to the downstream movement.
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Sheng, Chunhua, and Xiao Wang. "A Global Preconditioning Method for Low Mach Number Viscous Flows in Rotating Machinery." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-91189.
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A preconditioning scheme is applied to a compressible turbomachinery flow solver MSU-TURBO for simulating viscous flows at low Mach number and incompressible region. The Navier-Stokes equations are cast in a non-inertial rotating frame. A constant diagonal preconditioning matrix is applied to the conservative form of the governing equations, which contains a single parameter depending on the reference Mach number and rotational speed of the relative frame. The effect of the rotational speed on preconditioned scheme is numerically investigated for two low speed viscous flows in rotating machinery, a NASA low speed centrifugal compressor (LSCC) and a marine propeller (P5168). Computations are compared against the original MSU-TURBO solutions, and suggestions are provided for computing the low Mach number flows in rotating turbomachinery using the preconditioned TURBO solver.
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Kaifuku, Kazuhide, Soe Minn Khine, Tomoya Houra, and Masato Tagawa. "Response Compensation Scheme for Constant-Current Hot-Wire Anemometry Based on Frequency Response Analysis." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44437.
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Hot-wire anemometry (HWA) is used for measuring velocity fluctuations such as turbulent flows. It is generally operated in three modes; constant-temperature (CT), constant-current (CC) and constant-voltage (CV) types. The constant-temperature anemometer (CTA) is the mainstream anemometer, while others are rarely used in measuring normal turbulent flows because of their insufficient response speed. However, since the constant-current anemometer (CCA) can be composed of simple circuits, the HWA can be realized at quite a low cost. In this study, the response characteristics of the CCA are theoretically analyzed, and a compensation scheme is proposed. The scheme is experimentally tested in a turbulent wake flow formed behind a cylinder. As a result, it has been confirmed that the root-mean-square (rms) velocities and the power-spectrum distributions compensated by the present scheme agree well with those measured with CTA. Hence, the CCA provides reliable measurement of turbulent velocity fluctuations.
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Subotic, M., and F. C. Lai. "Flows in Rotating Cylinders With a Porous Lining." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41399.
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Flow and temperature fields in an annulus between two rotating cylinders have been examined in this study. While the outer cylinder is stationary, the inner cylinder is rotating with a constant angular speed. A homogeneous and isotropic porous layer is press-fit to the inner surface of the outer cylinder. The porous sleeve is saturated with the fluid that fills the annulus. The Brinkman-extended Darcy equations are used to model the flow in the porous layer while Navier-Stokes equations are used for the fluid layer. The conditions applied at the interface between the porous and fluid layers are the continuity of temperature, heat flux, tangential velocity and shear stress. Analytical solutions have been attempted. Through these solutions, the effects of Darcy number, Brinkman number, and porous sleeve thickness on the velocity profile and temperature distribution are studied.
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Chen, Limin, Guanghua He, Dazheng Wang, and Zihao Zhang. "Three-Dimensional Forward-Speed Seakeeping Calculation Using FINE/Marine." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54780.
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A time-domain seakeeping numerical model based on a computational fluid dynamics (CFD) software FINE/Marine has been developed for nonlinear steady and unsteady viscous flows. Simulation of multi-phase flows around a Wigley hull with forward speed is performed by solving the Reynolds-average Navier-Stokes (RANS) and continuity equations with k-ω (SST-Menter) turbulence model. The water free surface is captured by Blend Reconstruction Interface Capturing Scheme (BRICS). Both steady and unsteady problems including wave-making, radiation and diffraction problems are simulated. Ship waves generated by the Wigley model advancing at a constant forward speed in calm water or incident waves are computed. The numerical results including the wave-making resistance and wave patterns for steady problem, hydrodynamic coefficients and forces for unsteady problems are illustrated and compared with experimental measurements in good agreement. It is confirmed that the present numerical model has the capability of evaluating the seakeeping performance of ships.
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Garbaly, Aleksey, and Thomas Shepard. "Impact of Bubble Size on Flow Response to Transient Pressure Drop Through Converging Nozzle." In ASME 2020 Fluids Engineering Division Summer Meeting collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/fedsm2020-20278.
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Abstract For homogenous two-phase bubbly flows, the theoretical speed of sound is dramatically reduced at moderate void fractions to speeds much lower than the speed of sound for either single phase. This theoretical speed of sound would suggest a propensity for bubbly flows to reach choked conditions when traveling through a convergent nozzle. However, for a bubbly flow to be considered homogenous requires assumptions that may not be realized in practical applications. In this experimental study, a bubbly flow was sent through a convergent nozzle before entering a large chamber. By setting steady flow conditions upstream and then reducing the chamber pressure via a vacuum pump, the transient response in terms of gas and liquid flow rates and upstream channel pressure was determined. The bubble size was carefully varied from ∼0.3–1 mm while holding gas and liquid flow rates constant in order to study how bubble size affects the transient flow characteristics. High-speed imaging was used for measuring the bubbles. Experiments were also conducted at two gas-liquid mass flow ratios. Results are presented to demonstrate the impact of bubble size and gas-liquid ratio on the transient response of upstream gas and liquid flow rates, upstream pressure and exit Mach number to the lowering of pressure downstream of the convergent nozzle. Results are presented both for flows that remained in the bubbly regime and for flows that transitioned to an annular flow regime during a trial.