共查询到20条相似文献,搜索用时 31 毫秒
1.
A three-dimensional numerical model is developed and the aerodynamic loads are determined for the three-dimensional flow acting
on a blunt cone flying in the atmosphere along the boundary of a rarefied region, as functions of the degree of immersion
of the surface of the body in low-density air. The nonstationary gas-and aerodynamic processes accompanying the entry and
exit of the body from the rarefied region are studied. The aerodynamic coefficients obtained with an approximate model are
compared with the three-dimensional calculations and found to be in satisfactory agreement with them.
Zh. Tekh. Fiz. 68, 32–37 (November 1998) 相似文献
2.
As the speed of high-speed train (HST) increases continuously, aerodynamic noise has become more remarkable compared with the wheel/rail noise, which affects the inhabited environment along the railway and the riding comfort. This paper preliminarily investigates the feasibility of using open-cell metal foam covering layer to reduce the low Mach number aerodynamic noise generated by the flow around a circular cylinder which is the typical section of pantographs. The aerodynamic noises radiated from the circular cylinder with and without metal foam are calculated. The hybrid method combining two-dimensional large eddy simulation (LES) with Ffowcs Williams–Hawkings (FW–H) equation is employed. The calculated Strouhal number, time-averaged drag coefficient, base pressure and overall sound pressure level agree well with some available experimental data. Then, the influences of metal foam porosity, pore density, thickness of covering layer and the speed of train on the aerodynamic noise and the aerodynamic forces are investigated, and some detailed comparisons of flow field are made. The numerical results indicate that as a passive scheme, the open-cell metal foam with high porosity can modify the flow, adjust the vortex shedding frequency and regularize the wake, leading to a significant reduction of aerodynamic noise. The results are expected to provide useful information for the control of aerodynamic noise using this new material. 相似文献
3.
Determination of the temperature distribution in liquids and solids using holographic interferometry 总被引:1,自引:0,他引:1
V. V. Bat’kovich O. N. Budenkova V. B. Konstantinov O. L. Sadov E. A. Smirnova 《Technical Physics》1999,44(6):704-708
It is shown that holographic interferometry can be applied to solve two problems: heating of a glass plate by a complex heat
source and nonisothermal flow of a submerged jet around a wedge. The process of isolating and numbering the skeletal lines
on the interferograms is automated and direct calculations are made of the temperature fields.
Zh. Tekh. Fiz. 69, 106–111 (June 1999) 相似文献
4.
In this paper we report on an experimental study of the characteristics of nanosecond pulsed discharge plasma aerodynamic actuation. The N 2 (C 3 Π u ) rotational and vibrational temperatures are around 430 K and 0.24 eV, respectively. The emission intensity ratio between the first negative system and the second positive system of N 2 , as a rough indicator of the temporally and spatially averaged electron energy, has a minor dependence on applied voltage amplitude. The induced flow direction is not parallel, but vertical to the dielectric layer surface, as shown by measurements of body force, velocity, and vorticity. Nanosecond discharge plasma aerodynamic actuation is effective in airfoil flow separation control at freestream speeds up to 100 m/s. 相似文献
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A. N. Kravtsov T. Yu. Mel’nichuk 《Russian Journal of Physical Chemistry B, Focus on Physics》2011,5(4):582-588
The parameters of a conical stabilizer and its effect on the aerodynamic characteristics of the high-speed air vehicle, in
general, are examined. The flow characteristics of an high-speed air vehicle with a conical stabilizing device are analyzed.
Simulation results are compared with experimental data. Qualitative features of the supersonic flow associated with the characteristics
of the drag of an aerodynamic configuration with a stabilizing device in the form of a truncated cone are considered. Particular
attention is paid to the physical aspects of the flow around the considered configurations and to elucidating the mechanisms
responsible for a minimum in the drag coefficient of a wingless high-speed air vehicle. A general mechanism of occurrence
of the minimum in the drag coefficient for aerodynamic configurations with a conical tail stabilizer is studied. 相似文献
7.
Y. Nakamura 《Journal of sound and vibration》1979,67(2):163-177
This paper is concerned with theoretical and experimental investigations on the aerodynamic mechanism of torsional flutter of bluff structures. In the experiment, measurements were made of the unsteady aerodynamic lifts and moments acting on two rectangular bar models which were forced to oscillate either in a torsional or in a heaving mode in a uniform wind tunnel flow. It is found that the fluid memory effect is, in marked contrast to the situation for transverse galloping, responsible for the onset of torsional flutter of bluff structures. The effect of the pivotal position on torsional flutter of bluff structures is also investigated. 相似文献
8.
Measurements of spoiler aerodynamic noise, generated in a low velocity flow duct and radiated from an open exhaust termination, have been made in the form of sound power spectra. The individual octave power measurements are satisfactorily collapsed (within ± 3 dB) with the aid of derived theoretical scaling laws. Non-dimensional spectra are presented which permit generalized predictions of flow noise for bluff bodies, including splitter attenuators, mounted in low speed flow ducts. 相似文献
9.
In this article we present the extension of the a posteriori error estimation and goal-oriented mesh refinement approach from laminar to turbulent flows, which are governed by the Reynolds-averaged Navier–Stokes and k–ω turbulence model (RANS-kω) equations. In particular, we consider a discontinuous Galerkin discretization of the RANS-kω equations and use it within an adjoint-based error estimation and adaptive mesh refinement algorithm that targets the reduction of the discretization error in single as well as in multiple aerodynamic force coefficients. The accuracy of the error estimation and the performance of the goal-oriented mesh refinement algorithm is demonstrated for various test cases, including a two-dimensional turbulent flow around a three-element high lift configuration and a three-dimensional turbulent flow around a wing-body configuration. 相似文献
10.
Accurate aerodynamic measurements in the hypersonic flow of large aircraft models in tunnels have practical significance, but pose a significant challenge. Novel aerodynamic force measurement methods have been proposed,but lack theoretical support. The forms of the force signals techniques for signal processing and calculation of aerodynamics are especially problematic. A theoretical study is conducted to investigate the dynamic properties based on models of the draw-rod system and slender rods. The results indicate that the inertia item can be neglected in the rod governing equation;further, the solutions show that the signals of each rod are a combination of aerodynamic signals(with a constant value) and sine signals, which can be verified by experimental shock tunnel results. Signal processing and aerodynamics calculation techniques are also found to be achievable via the flat part of the signals. 相似文献
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The paper presents the results of theoretical and experimental studies of the occurrence and locations of aerodynamic noise sources in air blowers related to air flow around stationary and moving elements inside a machine body. These studies were based on basic research by Lighthill and Curle and used a developed method for measuring pressure pulsations on rotating blades and stationary elements of a machine body. The most significant sources of discrete and broadband components of aerodynamic noise were revealed. The role of blades in an impeller in the emission of discrete noise components was studied. It was established that broadband peaks in the emitted noise are associated with acoustic resonances of the internal volume of the air blower. It was shown that the turbulence and velocity of the incoming flow influence the intensity of aerodynamic sources inside the body. Our studies spurred both deeper research into the nature of aerodynamic noise sources that form in air blowers and recommendations for reducing the noise produced by these sources. 相似文献
13.
An experimental study has been conducted to examine the low-speed aerodynamic characteristics of a pair of circular jets behaviour
in the vortex-wake of a blunted cone cylinderbody combination with and without a 70° leading edge sweep delta wing. The induced
flow-field was examined via two-dimensional hot-wire anemometry surveys. Comparisons were made between the induced wake with
and without the circular jets. The flow field over the models was visualized using smoke and oil flow visualization. The jet-pair
was found to undergo severe distortion within a very short distance from the nozzle exits. The shape of the jets was shown
to change considerably when placed in the vortex wake flow field of the models, which caused the jet-pair to spread and become
entrained within the vortices and wake created by the models. 相似文献
14.
We propose a method for deriving duality relations for two-dimensional inhomogeneous Z(N)-symmetric models on a finite square lattice wound around a torus. The method is used to obtain duality relations for the
vector Potts model, the Berezinskii-Villain Z(N)-model, the Ashkin-Teller model, and the 8-vertex model on a lattice obliquely wound around a torus, as well as an exact
relation linking the partition functions of the latter two models.
Zh. éksp. Teor. Fiz. 113, 240–260 (January 1998) 相似文献
15.
S. T. Surzhikov 《Doklady Physics》2018,63(2):76-81
The problem of the radiation gas dynamics of super-orbital entry into dense layers of the Earth’s atmosphere of the command module of Apollo 4 is solved numerically in the two-dimensional formulation of the flow around an aerodynamic frontal shield at the velocity V∞= 10.7 km/s in the altitude range H = 91.5?76.2 km. The density distributions of the spectral and integral radiation heat fluxes on the surface flowed around are obtained. The considerable role of atomic spectral lines in the radiation heating of the surface is shown. The results of calculations are compared with the flight experimental data and the calculated data of other authors. 相似文献
16.
《Journal of Nonlinear Mathematical Physics》2013,20(2):198-221
Abstract A new class of integro-partial differential equation models is derived for the prediction of granular flow dynamics. These models are obtained using a novel limiting averaging method (inspired by techniques employed in the derivation of infinite-dimensional dynamical systems models) on the Newtonian equations of motion of a many-particle system incorporating widely used inelastic particle-particle force formulas. By using Taylor series expansions, these models can be approximated by a system of partial differential equations of the Navier-Stokes type. The exact or approximate governing equations obtained are far from simple, but they are less complicated than most of the continuum models now being used to predict particle flow behavior. Solutions of the new models for granular flows down inclined planes and in vibrating beds are compared with known experimental and analytical results and good agreement is obtained. 相似文献
17.
It is known that the flying characteristics of the golf ball is influenced by flying speed, rotational frequencies and the dimples, etc. In this study, the drag and lift acting on the test balls are measured using a three components loadcell by changing Reynolds number and the spin rate ratio, the number and the depth of dimples. And the flow around the balls is visualized by applying the oil film method and PIV in the stationary state. From these results, the aerodynamic drag and lift coefficients of the balls in the stationary and the rotational state are made clear. 相似文献
18.
The results of investigations on the possibility of an electrohydrodynamic force effect on a gas flow implemented with the help of a barrier discharge are presented. A new method of controlling the laminar flow around a base with suppression of instabilities of the incoming flow due to electrohydrodynamic force action on the boundary layer near the forward edge of a swept wing is proposed. An efficient multidischarge actuator system is developed and created for active control of aerodynamic flows with induced-air-flow characteristics exceeding the world analogues. 相似文献
19.
The design of supersonic three-dimensional inlets using the V-shaped body forming a two-dimensional flow including an initial
oblique shock wave and a subsequent isentropic compression wave is considered. Such a flow appears attractive for inlets design
due to a possibility of obtaining high compression levels of external flow over the inlet ramp with small losses of the total
pressure. Numerical computations of the flows around the designed configurations were carried out in design and off-design
regimes using Euler code. The flow structure was identified, the aerodynamic characteristics of the inlets were determined.
The investigation covers the range of supersonic speeds corresponding to the freestream Mach numbers M∞= 1.8−2.5. 相似文献