共查询到20条相似文献,搜索用时 15 毫秒
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A theoretical, experimental and numerical study is presented of the interaction of a vortex–wake created by an upstream blade with a downstream prismatic block. The aim of the study is to investigate the fundamentals of force and noise generation for this type of flow and explain how inter-object spacing affects the far-field noise level. A theoretical model, based on a compact form of Curle's formulation, is developed and shows that acoustically constructive or destructive interference is determined by the amplitude and phase of the forces on each object. Experimental and two-dimensional, unsteady numerical results of the vortex–wake interaction case are presented for several blade–block separation distances. Using a combination of experimental and numerical data, the theoretical model is able to explain observed variations in far-field noise level with blade–block separation distance. The numerical model accurately predicts the phase relationship between the unsteady forces on each object. 相似文献
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A. V. Voevodin 《Fluid Dynamics》2008,43(5):725-730
The effect of winglets on the aerodynamic characteristics of a heavy aircraft and the parameters of the vortex wake behind it is investigated for the landing regime. The solution of the complete problem is obtained by breaking up the wake into three regions, namely, the near, intermediate, and far flowfields, in which the corresponding subproblems are successively solved. The wake flowfields are obtained at different distances from the aircraft, together with the distributions of the mean azimuthal velocity over the vortex radius, and the lifetime of the vortex system is estimated for several one-and two-element wingtip versions. All the results are compared with those for the baseline layout with no winglets. 相似文献
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V. A. Yudin 《Journal of Applied Mechanics and Technical Physics》2001,42(5):786-793
A semianalytical method was developed to calculate the hydrodynamic interaction of two blade cascades moving relative to one another. The potential perturbation of the flow by the cascades and the vortex perturbation due to blade edge wakes are taken into account. Along with the steady wakes caused by boundary layer separation from the blade cascades, allowance is made of the unsteady wakes separating from the blade trailing edges because of change in velocity circulation on them. The unsteady wakes are calculated with allowance for their diffusion in the presence of flow viscosity using approximate boundarylayer theory. The method is implemented as a program for calculating the unsteady hydrodynamic characteristics of blade cascades on a personal computer. Examples of calculation and a comparison with experiment are given. 相似文献
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Two mechanical models have been presented in this paper for structural failure prediction of piping systems conveying liquids subjected to pressure transients. One model takes into account the axial fluid–structure interaction (FSI) phenomenon between fluid and pipe motion, whereas the other refers to an extension of the well-known waterhammer formulation. Both models are described by a system of non-linear hyperbolic equations which are solved by using a numerical procedure based upon the operator splitting technique and Glimm's scheme. To implement Glimm's method, it is presented the solution of a 4×4 Riemann problem with discontinuous coefficients. Numerical predictions of both models are presented and compared, so that the influence of the FSI term on the failure analysis is focused on. © 1998 John Wiley & Sons, Ltd. 相似文献
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J. Świrydczuk 《Experiments in fluids》1990,9(4):181-190
The two-dimensional interaction of a single vortex with a thin symmetrical airfoil and its vortex wake has been investigated in a low turbulence wind tunnel having velocity of about 2 m/s in the measuring section. The flow Reynolds number based on the airfoil chord length was 4.5 × 103. The investigation was carried out using a smoke-wire visualization technique with some support of standard hot-wire measurements. The experiment has proved that under certain conditions the vortex-airfoil-wake interaction leads to the formation of new vortices from the part of the wake positioned closely to the vortex. After the formation, the vortices rotate in the direction opposite to that of the incident vortex.List of symbols
c
test airfoil chord
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C
vortex generator airfoil chord
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TA
test airfoil
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TE
test airfoil trailing edge
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TE
G
vortex generator airfoil trailing edge
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t
dimensionless time-interval measured from the vortex passage by the test airfoil trailing edge: gDt=(T-T-
TE)·U/c
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T
time-interval measured from the start of VGA rotation
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U
free stream velocity
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U
vortex induced velocity fluctuation
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VGA
vortex generator airfoil
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y
distance in which the vortex passes the test airfoil
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Z
vortex circulation coefficient: Z=/(U · c/2)
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vortex generator airfoil inclination angle
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vortex circulation
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vortex strength: =/2 相似文献
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We analyze the topology of the two-dimensional flow around a circular cylinder at moderate Reynolds numbers in the regime where the vortex wake is created. A normal form for the stream function close to the cylinder is presented and used to predict the streamline pattern both in the steady and the periodic regime, where two different vortex shedding scenarios are identified. The theoretical predictions are verified numerically. For the vorticity, a very different topology occurs with infinite nested sequences of iso-curves moving downstream. General equations of motion for critical points are derived. 相似文献
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International Applied Mechanics - 相似文献
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The decay of a Kármán vortex street and the formation of a secondary vortex structure in the far wake of a streamlined cylinder are studied. The dynamics of spatially evolving vortex structures is examined in the free flow and in the following ways of external influence on this flow: rotation with a constant velocity and translational and rotational oscillations of the cylinder. The results are obtained by numerically solving the Navier-Stokes equations with two different methods. The corresponding boundary value problems are formulated in the domains extended up to 500 radii of the cylinder. 相似文献
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The influence of inertial interaction on the coefficient describing the redistribution of the amplitude of a plane wave is
analyzed. Two new wave effects in fibrous microcomposites are revealed: abrupt change in the amplitude of the first mode in
the matrix and the absence of the second mode in fibers in some frequency range
Translated from Prikladnaya Mekhanika, Vol. 44, No. 11, pp. 94–98, November 2008. 相似文献
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A new type of vibrational lift force [1] acting on a spherical body oscillating in a viscous fluid near a rigid boundary is experimentally investigated. The interaction between the body and the cavity boundary creates a repulsion force which is capable of holding a heavy body in the gravity field at a certain distance from the floor and a light body at a certain distance from the ceiling. The repulsion force appears at a distance comparable with the Stokesian boundary layer thickness and increases as the surface is approached. Outside the viscous interaction range, the repulsion force is replaced by an attraction force which decays with distance. Dimensionless parameters governing the vibrational interaction are found and threshold curves, corresponding to the transition of bodies of different densities to the “suspended” state, are plotted as functions of a dimensionless frequency. The dependence of the repulsion and attraction forces on the distance between the body and the wall is studied. 相似文献
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B. V. Zheleznyi 《Journal of Applied Mechanics and Technical Physics》1976,17(3):355-362
The theory of the diverging meniscus of a Newtonian liquid for capillary flow conditions at low meniscus velocities, in which the thermodynamic and Theological features of thin wetting films appear, is set forth. Two cases are considered: thermodynamically stable wetting film with high viscosity in the boundary layer on a completely wetted solid surface and a thermodynamically unstable film on a conditionally wetted solid surface exhibiting a liquid slip effect.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 72–82, May–June, 1976.The author wishes to express his appreciation to A. G. Grivtsov and V. S. Yushchenko for valuable assistance in the computer calculations. 相似文献
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The losses in hydrodynamic cascades caused by periodic flow unsteadiness are theoretically estimated on the assumption that the losses are due to energy expenditure to the formation of unsteady trailing vortices shed from the profiles of the cascades. The trailing vortex intensity is determined within the framework of the inviscid fluid model, by solving the corresponding problems in the linear formulation. The work done on the trailing vortex formation is determined by the increment of the kinetic energy of the flow induced by the corresponding vortices. Examples of calculations are presented for the case of periodic unsteadiness of the flow due to the hydrodynamic interaction of the cascades. The calculated results are compared with the experimental data. 相似文献
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Anthony Leonard 《Theoretical and Computational Fluid Dynamics》2010,24(1-4):369-375
The motion of a tube of vorticity with a cross sectional radius that is everywhere small compared to local radius of curvature of the tube is considered. In particular, we determine the inviscid motion of the 3D space curve that traces the centerline of the tube for an arbitrary distribution of axial vorticity within the core. 相似文献