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1.
The flow in a planar-radial vortex chamber. 1. An experimental study of the velocity field in transient and steady flows 总被引:1,自引:0,他引:1
F. A. Bykovskii E. F. Vedernikov 《Journal of Applied Mechanics and Technical Physics》1999,40(6):1097-1105
Two methods for determining the flow velocity in a vortex chamber of planar-radial geometry under transient and steady-state
conditions are proposed. Local flow velocities throughout the entire volume of the chamber are measured, and the flow is found
to be rotational. The effect of accumulation of particles heavier than air in the butt-end boundary layer is revealed.
Lavrent'ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from
Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 112–121, November–December, 1999. 相似文献
2.
A. V. Kazakov 《Fluid Dynamics》1998,33(3):338-345
The results of calculating the stability of a three-dimensional swirl flow of a viscous heat-conducting gas are presented.
The stability characteristics are determined using the linear time-dependent theory of plane-parallel flow stability. The
main undisturbed axisymmetric vortex flow was determined numerically using a quasi-cylindrical approximation for the complete
set of Navier-Stokes equations. The circulation of the peripheral velocity in the cocurrent flow surrounding the viscous vortex
core was assumed to be constant. In analyzing the stability, nonaxisymmetric perturbations in the shape of waves traveling
along the vortex axis with both positive and negative wavenumbers were considered; in these two cases the perturbation rotation
is either the same or opposite in sense to the rotation in the vortex core. Neutral stability curves are determined for various
values of the swirling parameter and the cocurrent flow Mach number.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 50–59, May–June, 1998. 相似文献
3.
J. Wilkinson A. Motamed-Amini I. Owen 《International Journal of Heat and Fluid Flow》1988,9(4):373-380
The internal compressible flow of a thin vortex chamber was investigated experimentally by measuring the radial distribution of temperature and pressure, from which the velocity field was calculated. The bulk of the internal vortex was found to be described by uθr0.69 = constant. The total resistance of the vortex chamber to the flow was also investigated in the context of fluidic vortex diode behavior under conditions of compressible and choked flow. It was found that the vortex chamber choked at an upstream-to-downstream pressure ratio of about 6 and in doing so passed a mass flow rate of 28% of the equivalent one-dimensional ideal nozzle. The resistance of vortex chambers is known to be strongly influenced by the presence of reversed flow in the exit due to vortex breakdown. Schlieren photography of the swirling exhaust flow was used to show that, while vortex breakdown does occur, it can only do so after the flow has become subsonic downstream of the exit and cannot therefore influence the vortex chamber resistance. 相似文献
4.
This study investigates the flow past a confined circular cylinder built into a narrow rectangular duct with a Reynolds number
range of 1,500 ≤ Re
d
≤ 6,150, by employing the particle image velocimetry technique. In order to better explain the 3-D flow behaviour in the
juncture regions of the lower and upper plates and the cylinder, respectively, as well as the dynamics of the horseshoe vortex
system, both time-averaged and instantaneous flow data are presented for regions upstream and downstream of the cylinder.
The size, intensity and interaction of the vortex systems vary substantially with the Reynolds number. Although the narrow
rectangular duct with a single built-in cylinder is a geometrically symmetrical arrrangement, instantaneous flow data have
revealed that the flow structures in both the lower and upper plate–cylinder junction regions are not symmetrical with respect
to the centreline of the flow passage. The vortical flow structures obtained in side-view planes become dominant sometimes
in the lower juncture region and sometimes in the upper juncture region in unsteady mode. 相似文献
5.
V. B. Kurzin 《Journal of Applied Mechanics and Technical Physics》2006,47(3):346-358
A model for separated incompressible flow past thin airfoils in the neighborhood of the “shockless entrance” condition is
constructed based on the averaging of the vortex shedding flow past the airfoil edges. By approximation of the vortex shedding
by two vortex curves, determination of the average hydrodynamic parameters is reduced to a twofold solution of an integral
singular equation equivalent to the equation describing steady-state nonseparated airfoil flow. In this case, the calculation
time is two orders of magnitude smaller than the time required for the solution of the corresponding evolution problem. The
results of a test calculation using the proposed method are in fair agreement with available results of calculations and experiments.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 3, pp. 49–63, May–June, 2006. 相似文献
6.
The stability of an axisymmetric flow of viscous gas in a circular pipe, which models the Burgers vortex in the pipe axis
neighborhood, is studied within the linear theory framework. Neutral curves for the most unstable disturbances are calculated.
The influence of the characteristic Mach number on the flow stability is investigated. It is shown that for a given model
velocity distribution the Mach number affects only the temperature and pressure profiles of the main undisturbed flow. In
this case, for the disturbance types considered, as the Mach number increases, the critical Reynolds number corresponding
to loss of stability decreases.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 35–41, January–February,
1999.
The work received financial support from the Russian Foundation for Basic Research (project No. 96-01-00586). 相似文献
7.
The research carried out in [1–8] is developed by considering the self-similar problem of the unsteady separated flow over
a plate expanding from a point with the constant velocity D of a plane-parallel stream of ideal fluid with velocity V∞. At infinity the flow is uniform, steady and normal to the surface of the plate. A wide range of values of the parameter
α=V∞/D is investigated. On the value of α there depends, in particular, the direction of shedding of the vortex sheets (VS) which,
in accordance with the Joukowsky-Chaplygin condition, occur in separated flow over a plate. A comparison is made with the
results obtained when the sheets are replaced by vortex filaments (VF). In accordance with [9] the choice of the intensity
of the VF ensures, like the introduction of VS, the finiteness of the flow velocity at the edges of the plate. Within the
framework of the unsteady analogy and the law of plane sections the problem of the flow over a delta wing at an angle of attack
reduces to the unsteady flow over an expanding plate investigated. In addition to [3, 9], this question was also examined
in [10–15]. In [11–15] and in [3] the analysis is based on VS and in [9, 10] on VF. Special attention is paid to the topology
of the flow, in particular, to the structure of the so-called conical streamlines and their points of convergence and divergence
(this was done in [3] for a special, nonlinear law of expansion of the plate and a variable free-stream velocity). The results
obtained for the models with VS and VF are compared over a broad range of values of α, not only with respect to the integral
characteristics, as in [12], but also with respect to the flow patterns.
Moscow. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 62–69, September–October, 1988. 相似文献
8.
M. V. Ustinov 《Journal of Applied Mechanics and Technical Physics》2000,41(4):658-665
The flow past a flat plate with a blunted leading edge by a flow of a viscous incompressible fluid with a small spanwise-periodic,
steady nonuniformity of the velocity profile is considered. Such a flow simulates the interaction of one type of vortex disturbances
of a turbulent external flow with the boundary layer. The solution obtained predicts generation of strong disturbances in
the boundary layer, which are similar to the streaky structure observed in the case of high free-stream turbulence. It is
shown that the boundary-layer flow on blunted bodies is more sensitive to vortex disturbances than on a plate with a sharp
leading edge.
Central Aerohydrodynamic Institute, Zhukovskii, 140160. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol.
41, No. 4, pp. 93–100, July–August, 2000. 相似文献
9.
X. Zhang 《Experiments in fluids》2000,28(4):344-354
A model test study was performed on streamwise vortices generated by a rectangular jet in an otherwise flat-plate turbulent
boundary layer. The study was conducted in a low speed wind tunnel. The rectangular jet had a cross-section size of 28 mm
by 5.5 mm. The oncoming boundary layer had a 99.5 percent thickness of 25 mm. The freestream speed of the oncoming flow was
20 m/s. Measurements were performed with a three-element LDA system. The effects of skew angle and streamwise development
of vortex were investigated and the mean flow properties are presented. The study showed that the rectangular jet was able
to produce a streamwise vortex of higher strength than that of a round jet, while at the same time keeping the same size and
shape as that of a round jet. A 63% increase in the maximum vorticity was found. The 45∘ skew angle was identified as the optimal skew angle for vortex production.
Received: 24 June 1998/ Accepted: 21 May 1999 相似文献
10.
We consider a combined experimental (based on flow visualization, direct force measurement and phase-averaged 2D particle
image velocimetry in a water tunnel), computational (2D Reynolds-averaged Navier–Stokes) and theoretical (Theodorsen’s formula)
approach to study the fluid physics of rigid-airfoil pitch–plunge in nominally two-dimensional conditions. Shallow-stall (combined
pitch–plunge) and deep-stall (pure-plunge) are compared at a reduced frequency commensurate with flapping-flight in cruise
in nature. Objectives include assessment of how well attached-flow theory can predict lift coefficient even in the presence
of significant separation, and how well 2D velocimetry and 2D computation can mutually validate one another. The shallow-stall
case shows promising agreement between computation and experiment, while in the deep-stall case, the computation’s prediction
of flow separation lags that of the experiment, but eventually evinces qualitatively similar leading edge vortex size. Dye
injection was found to give good qualitative match with particle image velocimetry in describing leading edge vortex formation
and return to flow reattachment, and also gave evidence of strong spanwise growth of flow separation after leading-edge vortex
formation. Reynolds number effects, in the range of 10,000–60,000, were found to influence the size of laminar separation
in those phases of motion where instantaneous angle of attack was well below stall, but have limited effect on post-stall
flowfield behavior. Discrepancy in lift coefficient time history between experiment, theory and computation was mutually comparable,
with no clear failure of Theodorsen’s formula. This is surprising and encouraging, especially for the deep-stall case, because
the theory’s assumptions are clearly violated, while its prediction of lift coefficient remains useful for capturing general
trends. 相似文献
11.
Scanning PIV is applied to a laminar separation bubble to investigate the spanwise structure and dynamics of the roll-up of vortices within the bubble. The laminar flow separation with turbulent reattachment is studied on the suction side of an airfoil SD7003 at Reynolds numbers of 20,000–60,000. The flow is recorded with a CMOS high-speed camera in successive light-sheet planes over a time span of 1–2 s to resolve the temporal evolution of the flow in the different planes. The results show the quasi-periodic development of large vortex-rolls at the downstream end of the separation bubble, which have a convex structure and an extension of 10–20% chord length in the spanwise direction. These vortices possess an irregular spanwise pattern. The evolution process of an exemplary vortex structure is shown in detail starting from small disturbances within the separation bubble transforming into a compact vortex at the downstream end of the separation bubble. As the vortex grows in size and strength it reaches a critical state that leads to an abrupt burst of the vortex with a large ejection of fluid into the mean flow. 相似文献
12.
Guang-Kun Tan Gong-Xin Shen Shuo-Qiao Huang Wen-Han Su Yu Ke 《Experiments in fluids》2007,43(5):811-821
When swimming in water by flapping its tail, a fish can overcome the drag from uniform flow and propel its body. The involved
flow mechanism concerns 3-D and unsteady effects. This paper presents the investigation of the flow mechanism on the basis
of a 3-D robotic fish model which has the typical geometry of body and tail with periodic flapping 2-freedom kinematical motion
testing in the case of St = 0.78, Re = 6,600 and phase delay mode (φ = −75°), in which may have a greater or maximum propulsion (without consideration of the optimal efficiency). Using a special
technique of dye visualization which can clearly show vortex sheet and vortices in detail and using the inner 3-component
force balance and cable supporting system with the phase-lock technique, the 3-D flow structure visualized in the wake of
fish and the hydrodynamic force measurement were synchronized and obtained. Under the mentioned flapping parameters, we found
the key flow structure and its evolution, a pair of complex 3-D chain-shape vortex (S–H vortex-rings, S1–H1 and S2–H2, and their legs L1 and L2) flow structures, which attach the leading edge and the trailing edge, then shed, move downstream and outwards and distribute
two anti-symmetric staggering arrays along with the wake of the fish model in different phase stages during the flapping period.
It is different with in the case of St = 0.25–0.35. Its typical flow structure and evolution are described and the results prove that they are different from the
viewpoints based on the investigation of 2-D cases. For precision of the dynamic force measurement, in this paper it was provided
with the method and techniques by subtracting the inertial forces and the forces induced by buoyancy and gravity effect in
water, etc. from original data measured. The evolution of the synchronized measuring forces directly matching with the flow
structure was also described in this paper. 相似文献
13.
V. P. Zhitnikov N. M. Sherykhalina O. I. Sherykhalin 《Journal of Applied Mechanics and Technical Physics》2000,41(1):62-68
An improved Levi-Civita method in which the singularities of the desired function are taken into account by introducing terms
containing power singularities is proposed. Results of numerical analysis of the nonlinear problem of a vortex in a bounded
flow of an ideal weighable fluid (Fr>1) are given. The following limiting flow regimes are studied: the Stokes waves with one and two crests, emergence of a critical
point on the surface, and the detachment of a vortex from a soliton and a uniform flow. It is shown that nonperiodic waves
can form in a local zone in the vicinity of the critical point.
Ufa State Technical Aviation University, Ufa 450000. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41,
No. 1, pp. 70–76, January–February, 2000. 相似文献
14.
We have used a third-order essentially non-oscillatory method to obtain numerical shadowgraphs for investigation of shock–vortex
interaction patterns. To search different interaction patterns, we have tested two vortex models (the composite vortex model
and the Taylor vortex model) and as many as 47 parametric data sets. By shock–vortex interaction, the impinging shock is deformed
to a S-shape with leading and lagging parts of the shock. The vortex flow is locally accelerated by the leading shock and
locally decelerated by the lagging shock, having a severely elongated vortex core with two vertices. When the leading shock
escapes the vortex, implosion effect creates a high pressure in the vertex area where the flow had been most expanded. This
compressed region spreads in time with two frontal waves, an induced expansion wave and an induced compression wave. They
are subsonic waves when the shock–vortex interaction is weak but become supersonic waves for strong interactions. Under a
intermediate interaction, however, an induced shock wave is first developed where flow speed is supersonic but is dissipated
where the incoming flow is subsonic. We have identified three different interaction patterns that depend on the vortex flow
regime characterized by the shock–vortex interaction.
相似文献
15.
Zhuo Li Xue-Feng Yuan Simon J. Haward Jeffrey A. Odell Stephen Yeates 《Rheologica Acta》2011,50(3):277-290
The non-linear dynamics of a semi-dilute (c/c* = 15) polydisperse polyethylene oxide (PEO) solution in microfluidics are studied experimentally using benchmark contraction–expansion
flow geometries with three contraction–expansion ratios (4:1:4, 8:1:8 and 16:1:16) and two narrow channel lengths (L
c/D
h = 53 and 5.3, where L
c is the length of the narrow channel and D
h is its hydraulic diameter). Complex flows over a range of elasticity numbers (El), Weissenberg numbers (Wi) and Reynolds numbers (Re) are characterized using micro-particle image velocimetry (
\upmu\upmu-PIV) and pressure drop measurements. The evolution of vortex formation and dynamics has been visualized through a step-flow-rate
experiment. Various flow dynamics regimes have been quantified and are presented in a Wi–Re diagram. The experimental results reveal that the contraction ratio can result in qualitatively different vortex dynamics
of semi-dilute polymer solutions in microfluidics, whereas the length of the narrow channel merely affects the dynamics at
a quantitative level. A single elasticity number, if defined by the size of the narrow channel, is not sufficient to account
for the effects of contraction ratio on the non-linear vortex dynamics. 相似文献
16.
V. A. Vishnyakov V. G. Zasetskii R. K. Karavosov A. G. Prozorov L. I. Sokolinskii 《Fluid Dynamics》1998,33(2):238-244
The initiation of narrow-band pressure fluctuations in the duct of a pipeline gas-compression station when the flow is turned
near a blind-ended cavity was studied in a wind tunnel. The flow pattern under consideration was estimated from visualization
of the flow in a water channel using the hydraulic analogy technique. It is believed that the high-intensity narrow-band pressure
fluctuations observed in the flow result from the instability and regular rearrangement of large-scale vortex structures in
the blind-ended cavity.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 104–111, March–April, 1998. 相似文献
17.
A. Yu. D’yachenko V. I. Terekhov N. I. Yarygina 《Journal of Applied Mechanics and Technical Physics》2006,47(5):671-678
The process of vortex formation in a cavity with inclined walls, which has a moderate aspect ratio, is experimentally studied,
and the distribution of pressure coefficients is measured. The angle of inclination of the side walls ϕ is varied from 30
to 90°. It is found that the flow in the cavity becomes unstable in the range of inclination angles ϕ = 60–70°. Flow reconstruction
occurs, which substantially alters the surface-temperature and static-pressure distributions. Large changes in these characteristics
and their nonuniform distributions for these angles are observed across the cavity on its frontal wall and on the bottom.
For small angles (ϕ = 30 and 45°), the pressure on the rear wall drastically increases, which leads to a small increase in
pressure averaged over the entire cavity surface.
__________
Translated from PrikladnayaMekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 68–76, September–October, 2006. 相似文献
18.
A numerical scheme based on the application of the vortex method to update the vorticity field and the implementation of the finite element method to satisfy the normal velocity boundary condition inside a complex time-dependent geometry is applied to simulate the flow produced by a piston sliding out of a chamber equipped with single or multiple intakes. This unsteady confined vortex flow is of interest in many applications. We use the idealization that the flow is incompressible, two-dimensional and planar and we analyse the results to study the flow during the intake process inside a model of an engine cylinder. The chamber top is fitted with an inlet channel, an inlet port or an inlet valve. In all cases when the intake channel axis coincides with that of the chamber, the flow in each side of the chamber consists essentially of two large counter-rotating eddies of almost the same size. The computed structures of these flows resemble qualitatively those which have been observed experimentally. The fluid motion is also computed for the case of a chamber equipped with an intake whose axis is not aligned with the chamber axis. In this case the flow at the end of the stroke is dominated by a single large eddy produced by the merging of the two eddies forming on the sides of the port. 相似文献
19.
PIV measurements for gas flow under gradient magnetic fields 总被引:1,自引:0,他引:1
Particle Image Velocimetry (PIV) techniques were developed to measure the convective N2-air flow under gradient magnetic fields. The velocity fields were calculated by the Minimum Quadratic Difference (MQD) algorithm and spurious vectors were eliminated by Delaunay Tessellation.The N2-air flow was measured as the magnetic flux density varying from 0~1.5T. A strengthened vortex flow of air was observed under the condition that the magnetic field was applied, and the velocity of N2 jet rose with the increase of the magnetic density. The experimental results show that the magnetic force will induce a vortex flow and cause a convection flow of the air mixture when both gradients of the O2 concentration and the magnetic field intensity exist. 相似文献
20.
This study utilizes a U-shape platform device to generate a single cavitation bubble for a detailed analysis of the flow field
characteristics and the cause of the counter jet during the process of bubble collapse caused by sending a pressure wave.
A high speed camera is used to record the flow field of the bubble collapse at different distances from a solid boundary.
It is found that a Kelvin–Helmholtz vortex is formed when a liquid jet penetrates the bubble surface after the bubble is compressed
and deformed. If the bubble center to the solid boundary is within one to three times the bubble’s radius, a stagnation ring
will form on the boundary when impinged by the liquid jet. The fluid inside the stagnation ring will be squeezed toward the
center of the ring to form a counter jet after the bubble collapses. At the critical position, where the bubble center from
the solid boundary is about three times the bubble’s radius, the bubble collapse flow will vary. Depending on the strengths
of the pressure waves applied, the collapse can produce a Kelvin–Helmholtz vortex, the Richtmyer–Meshkov instability, or the
generation of a counter jet flow. If the bubble surface is in contact with the solid boundary, the liquid jet can only move
inside-out without producing the stagnation ring and the counter jet; thus, the bubble collapses along the radial direction.
The complex phenomenon of cavitation bubble collapse flows is clearly manifested in this study. 相似文献