共查询到20条相似文献,搜索用时 15 毫秒
1.
A finite volume element method is developed for analyzing unsteady scalar reaction-diffusion problems in two dimensions. The method combines the concepts that are employed in the finite volume and the finite element method together. The finite volume method is used to discretize the unsteady reaction-diffusion equation, while the finite element method is applied to estimate the gradient quantities at cell faces. Robustness and efficiency of the combined method have been evaluated on uniform rectangular grids by using available numerical solutions of the two-dimensional reaction-diffusion problems. The numerical solutions demonstrate that the combined method is stable and can provide accurate solution without spurious oscillation along the high-gradient boundary layers. 相似文献
2.
This paper presents results of the numerical simulation of periodically unsteady flows with focus on turbomachinery applications.
The unsteady CFD solver used for the simulations is based on the Reynolds averaged Navier–Stokes equations. The numerical
scheme applies an extended version of the Spalart–Allmaras one-equation turbulence model coupled with a transition correlation.
The first example of validation consists of boundary layer flow with separation bubble on a flat plate, both under steady
and periodically unsteady main flow conditions. The investigation includes a variation of the major parameters Strouhal number,
amplitude, and Reynolds number. The second, more complex test case consists of the flow through a cascade of turbine blades
which is influenced by wakes periodically passing over the cascade. The computations were carried out for two different blade
loadings. The results of the numerical simulations are discussed and compared with experimental data in detail. Special emphasis
is given to the investigation of boundary layers with regard to transition, separation and reattachment under the influence
of main flow unsteadiness.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Marc Terracol 《Flow, Turbulence and Combustion》2006,77(1-4):161-184
Hybrid CFD/CAA methods have generally to be used for the numerical simulation of trailing-edge noise (see [9, 20] for instance). This study focuses on the first step of such hybrid methods, which is to predict the unsteady aerodynamic sources by the mean of a 3D unsteady simulation of the flow. Such a simulation is however generally still away from the numerical capabilities of ‘usual’ supercomputers. This paper investigates the use of a zonal LES method (based on the NLDE – Non-Linear Disturbance Equations – technique) for the numerical prediction of the aerodynamic noise sources. This method makes it possible to perform only zonal LES close to the main elements responsible of sound generation, while the overall configuration is only treated by a RANS approach. Attention will be paid to the specific boundary treatment at the interface between the RANS and LES regions. More precisely, the problem of the generation of turbulent inflow conditions for the LES region will be carefully addressed. The method is first assessed in the simulation of a flat plate ended by a blunted trailing-edge, and then applied to the simulation of the flow over a NACA0012 airfoil with blunted trailing-edge. 相似文献
4.
Javad Rostami 《Heat and Mass Transfer》2008,44(9):1079-1087
In this paper, unsteady heat transfer and fluid flow characteristics in an enclosure are investigated. The enclosure consists
of two vertical wavy and two horizontal straight walls. The top and the bottom walls are considered adiabatic. Two wavy walls
are kept isothermal and their boundaries are approximated by a cosine function. Governing equations including continuity,
momentum and energy were discretized using the finite-volume method and solved by SIMPLE method in curvilinear coordinate.
Simulation was carried out for a range of Grashof number Gr = 103–106, Prandtl number Pr = 0.5–4.0, wave ratio A (defined by amplitude/wavelength) 0.0–0.35 and aspect ratio W (defined by average width/wavelength) 0.5–1.0. Streamlines and isothermal lines are presented to corresponding flow and thermal
fields. Local and average Nusselt number distributions are presented. The obtained results are in good agreement with available
numerical and experimental data. 相似文献
5.
M. F. Ionina 《Journal of Applied Mechanics and Technical Physics》1999,40(6):1163-1172
The plane unsteady problem of impact of a thin elastic cylindrical shell on the surface of an ideal incompressible liquid
is considered. The initial stage of interaction between the body and the liquid when the stresses in the shell attain peak
values is studied. The problem is treated in a linearized formulation and is solved numerically by the normal modes method
within the framework of the Wagner approach. The numerical results agree with experimental data for various types of circular
cylindrical shells made from mild steel.
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. 186–197, November–December, 1999. 相似文献
6.
The fractional calculus approach is introduced into the seepage mechanics. A three-dimensional relaxation model of viscoelastic
fluid is built. The models based on four boundary conditions of exact solution in Laplace space for some unsteady flows in
an infinite reservoir is obtained by using the Laplace transform and Fourier sine and cosine integral transform. The pressure
transient behavior of non-Newtonian viscoelastic fluid is studied by using Stehfest method of the numerical Laplace transform
inversion and Gauss–Laguerre numerical integral formulae. The viscoelastic fluid is very sensitive to the order of the fractional
derivative. The change rules of pressure are discussed when the parameters of the models change. The plots of type pressure
curves are given, and the results can be provided to theoretical basis and well-test method for oil field. 相似文献
7.
The boundary-value problem of unsteady vortex flow of a viscous incompressible fluid in a cylindrical vessel with radial ribs
rotating at a variable angular velocity is solved using a finite-difference method. The results of the solution are used to
calculate the motion of a system of a solid body and a cavity filled with a liquid. The results are compared with available
experimental data.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 135–139, March–April, 2007. 相似文献
8.
The need of accurate and efficient numerical schemes to solve Richards’ equation is well recognized. This study is carried
out to examine the numerical performances of the nonlinear multigrid method for numerical solving of the two-dimensional Richards’
equation modeling water flow in variably saturated porous media. The numerical approach is based on an implicit, second-order
accurate time discretization combined with a vertex centered finite volume method for spatial discretization. The test problems
simulate infiltration of water in 2D saturated–unsaturated soils with hydraulic properties described by van Genuchten–Mualem
models. The numerical results obtained are compared with those provided by the modified Picard–preconditioned conjugated gradient
(Krylov subspace) approach. 相似文献
9.
The length scale criteria is widely accepted as an explanation for transition and hence existence of different shock wave
reflection configurations in pseudo-steady flows. However, there has not been any attempt to validate this criteria using
information obtained from a time-dependent numerical simulation. A high resolution time-dependent numerical simulation in
pseudo-steady flow is carried out in the present work. Time-dependent numerical data is used to calculate flow features in
a laboratory frame of reference to verify validity of the length scale criteria for existence of different shock wave reflection
configurations in pseudo-steady flow. This analysis is then extended to the study of unsteady shock wave reflection configurations
in shock–vortex interactions. It is shown that the existence of regular reflection (RR) and Mach reflection (MR) configurations
in an unsteady flowfield resulting from shock–vortex interactions can also be explained locally based on limiting conditions
similar to that prescribed by the length scale criteria for pseudo-steady flow.
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10.
The processes of interaction between concentrated energy fluxes and solid targets have been investigated in a number of studies.
The generation of magnetic fields in erosional plasma formations has been experimentally observed [1–4]. However, the evolution
of magnetic fields in plasma jets has not yet been studied in sufficient detail. This paper is devoted to a numerical investigation
of unsteady three-dimensional erosion plasma flows and the generation in those flows of magnetic fields resulting from the
action of laser radiation on solid targets.
Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 135–140, November–December, 1986.
The authors are grateful to I. V. Nemchinov and B. T. Fedyushin for useful discussion of their results. 相似文献
11.
A. S. Vereshchagin S. N. Vereshchagin V. M. Fomin 《Journal of Applied Mechanics and Technical Physics》2007,48(3):375-384
A mathematical model is constructed and an analytical solution is obtained for the problem of a one-dimensional steady flow
of a mixture of different gases with hollow permeable particles. The case of a one-dimensional unsteady flow of such a mixture
is analyzed numerically. The numerical solutions are compared with experimental data on the motion of the peak concentration
of helium in a fixed bed filled with cenospheres (solid hollow permeable spherical particles). The permeability of cenosphere
walls and the drag coeficient of cenospheres in the gas flow are determined.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 92–102, May–June, 2007. 相似文献
12.
This paper aims the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with the linear
unsteady aerodynamic model. High aspect ratio and flexibility are the specific characteristic of this type of wings. Wing
flexibility, coupled with long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore,
a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear general flexible Euler–Bernoulli
beam equations is used for structural modeling. Unsteady linear aerodynamic strip theory based on the Wagner function is used
for determination of aerodynamic loading on the wing. Combining these two types of formulation yields nonlinear integro-differentials
aeroelastic equations. Using the Galerkin’s method and a mode summation technique, the governing equations will be solved
by introducing a numerical method without the need to adding any aerodynamic state space variables and the corresponding equations
related to these variables of the problem. The obtained equations are solved to predict the aeroelastic response of the problem.
The obtained results for a test case are compared with those of some other works and show a good agreement between results. 相似文献
13.
Shock wave structure in a bubbly mixture composed of a cluster of gas bubbles in a quiescent liquid with initial void fractions
around 10% inside a 3D rectangular domain excited by a sudden increase in the pressure at one boundary is investigated using
the front tracking/finite volume method. The effects of bubble/bubble interactions and bubble deformations are, therefore,
investigated for further modeling. The liquid is taken to be incompressible while the bubbles are assumed to be compressible.
The gas pressure inside the bubbles is taken uniform and is assumed to vary isothermally. Results obtained for the pressure
distribution at different locations along the direction of propagation show the characteristics of one-dimensional unsteady
shock propagation evolving towards steady-state. The steady-state shock structures obtained by the present direct numerical
simulations, which show a transition from A-type to C-type steady-state shock structures, are compared with those obtained
by the classical Rayleigh–Plesset equation and by a modified Rayleigh–Plesset equation accounting for bubble/bubble interactions
in the mean-field theory.
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14.
Direct numerical simulation of disturbances generated by periodic suction-blowing in a hypersonic boundary layer 总被引:1,自引:0,他引:1
I. V. Egorov A. V. Fedorov V. G. Soudakov 《Theoretical and Computational Fluid Dynamics》2006,20(1):41-54
A numerical algorithm and code are developed and applied to direct numerical simulation (DNS) of unsteady two-dimensional
flow fields relevant to stability of the hypersonic boundary layer. An implicit second-order finite-volume technique is used
for solving the compressible Navier–Stokes equations. Numerical simulation of disturbances generated by a periodic suction-blowing
on a flat plate is performed at free-stream Mach number 6. For small forcing amplitudes, the second-mode growth rates predicted
by DNS agree well with the growth rates resulted from the linear stability theory (LST) including nonparallel effects. This
shows that numerical method allows for simulation of unstable processes despite its dissipative features. Calculations at
large forcing amplitudes illustrate nonlinear dynamics of the disturbance flow field. DNS predicts a nonlinear saturation
of fundamental harmonic and rapid growth of higher harmonics. These results are consistent with the experimental data of Stetson
and Kimmel obtained on a sharp cone at the free-stream Mach number 8. 相似文献
15.
N. A. Rubtsov V. A. Sinitsyn A. M. Timofeev 《Journal of Applied Mechanics and Technical Physics》1998,39(5):762-769
Results of a numerical study of unsteady radiative-convective heat transfer in a boundary layer on a thermally thin permeable
plate in the presence of intense radiation heating from outside are reported. The conjugate formulation of the problem takes
into account the thermal interaction between the plate and an external gas flow. We consider a turbulent flow of an emitting-absorbing
medium with the selective character of absorption. Calculation results are analyzed with a view for clarifying the influence
of the governing parameters, namely, the relative temperature of an external radiation source, the Stark number, and the injection
parameter. The possibility of inversion of a convective heat flux on the plate under the conditions of high-level external
radiation is found.
Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirisk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 5, pp. 126–133, September–October, 1998. 相似文献
16.
G. A. Perdikaris 《Heat and Mass Transfer》2001,37(6):583-591
A computational method for predicting the dispersion of gaseous emissions in regions with complex topography is presented.
Different meteorological conditions, source data, and gas compositions and specific weights are taken into consideration.
The three-dimensional governing equations of fluid- and thermodynamics are numerically solved by means of the finite volume
method. The kɛ turbulence model is utilized to account for the turbulent nature of the flow. The numerical results obtained by the proposed
method show satisfactory agreement with both results obtained by other numerical methods and experimental and/or measured
data. The presented method is applied to four test cases, including steady and unsteady problems, in order to illustrate its
usefulness.
Received on 1 March 2001 相似文献
17.
V. M. Bazovkin A. P. Kovchavtsev G. L. Kuryshev A. A. Maslov S. G. Mironov D. V. Khotyanovsky A. V. Tsarenko I. S. Tsyryulnikov 《Journal of Applied Mechanics and Technical Physics》2009,50(4):638-645
Coefficients of heat transfer to the surface in a laminar hypersonic flow (M
∞
= 21) over plane and axisymmetric models with a compression corner are presented. These coefficients are measured by an infrared
camera. The parameters varied in the experiments are the angle of the compression corner and the distance to the corner point.
Characteristics of the flow with and without separation in the corner configuration are obtained. The measured results are
compared with direct numerical simulations performed by solving the full unsteady Navier-Stokes equations. Experiments with
controlled streamwise structures inserted into the flow are described. A substantial increase in the maximum values of the
heat-transfer coefficient in the region of flow reattachment after developed laminar separation is demonstrated.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 112–120, July–August, 2009. 相似文献
18.
V. V. Mel’nikov 《Journal of Applied Mechanics and Technical Physics》2009,50(1):66-71
This paper presents a solution of the problem of unsteady heat transfer in a three-layer hollow sphere in a central-symmetric
formulation with various time-dependent boundary conditions on the inner and outer surfaces. In each layer of the sphere there
is heat release of known intensity which depends on the radial coordinate and time. The solution is obtained by a finite integral
transform on the radial coordinate. A numerical solution is presented for one version of the boundary conditions.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 1, pp. 78–84, January–February, 2009. 相似文献
19.
S. M. Aulchenko V. P. Zamuraev A. P. Kalinina 《Journal of Applied Mechanics and Technical Physics》2007,48(6):834-839
The possibility of controlling the aerodynamic characteristics of airfoils in transonic flight regimes by means of local pulsed
periodic energy supply is considered. The numerical solution of two-dimensional unsteady equations of gas dynamics allowed
determining the changes in the flow structure near a symmetric airfoil and its aerodynamic characteristics depending on the
magnitude of energy in the case of its asymmetric (with respect to the airfoil) supply. The results obtained are compared
with the calculated data for the flow around the airfoil at different angles of attack without energy supply. With the use
of energy supply, a prescribed lift force can be obtained with a substantially lower wave drag of the airfoil, as compared
with the flow around the airfoil at an angle of attack.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 70–76, November–December, 2007. 相似文献
20.
Results of numerical simulations of a quasi-one-dimensional unsteady flow in a channel considered as an element of an air-breathing
engine are presented. The influence of parameters of energy supplied in the pulsed-periodic mode (power, pulse frequency,
and distribution of energy sources along the channel) on the characteristics of the flow with Mach numbers M
0 = 2.4–4.0 at the channel entrance is determined. A channel configuration that allows the energy supply distribution to be found from
the condition of restriction of the maximum value of the gas temperature is proposed.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 1, pp. 3–11, January–February, 2009. 相似文献