摘要:

AbstractThis survey paper is devoted to the description of numerical methods for modern problems of computational fluid dynamics (CFD). The problems of steady and unsteady aerodynamic flows, different transition turbulent regimes and motion around complex shape bodies (aircraft as a whole) are investigated. These approaches sharply reduce the level of demand on computer resources.

ISSN:0029-5981    

DOI:10.1002/nme.1620340202

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA generalized curvilinear co‐ordinate Taylor weak statement implicit finite element algorithm is developed for the two‐dimensional and axisymmetric compressible Navier‐Stokes equations for ideal and reacting gases. For accurate hypersonic simulation, air is modelled as a mixture of five perfect gases, i.e. molecular and atomic oxygen and nirogen as well as nitric oxide. The associated pressure is then determined via Newton solution of the classical chemical equilibrium equation system. The directional semi‐discretization is achieved using an optimal metric data Galerkin finite element weak statement, on a developed‘companion conservation law system’, permitting classical test and trial space definitions. Utilizing an implicit Runge‐Kutta scheme, the terminal algorithm is then non‐linearly stable, and second‐order accurate in space and time on arbitrary curvilinear co‐ordinates. Subsequently, a matrix tensor product factorization procedure permits an efficient numerical linear algebra handling for large Courant numbers. For ideal‐ and real‐gas hypersonic flows, the algorithm generates essentially non‐oscillatory numerical solutions in the presence of strong detached shocks and boundary layer i

ISSN:0029-5981    

DOI:10.1002/nme.1620340203

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe present a method that has been developed for the construction of grids suitable for a large class of Computational Fluid Dynamics (CFD) solvers. Three independent steps are considered: a multidomain generation, an optimization and an adaptation. The first step handles the complexity of the three‐dimensional domain to be meshed and is able to perform an algebraic construction of the grid points within a multidomain topology; any decomposition can be considered and analysed by the algorithm. The second step is able to optimize a mesh with respect to a quality measure defined in terms of cell deformation; a conjugate gradient algorithm drives the nodes up to an equilibrium position that realizes the minimum of a mesh energy quantity. The final step handles the physics of the problem and moves the nodes in order to refine the mesh where anything of interest takes place, while preserving its good metric quality. The three steps have been implemented independently and successfully, as shown by the examples presente

ISSN:0029-5981    

DOI:10.1002/nme.1620340204

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA time marching integral equation method has been proposed here which does not have the limitation of the time linearized integral equation method in that the latter method can not satisfactorily simulate the shock wave motions. Firstly, a model problem–one dimensional initial and boundary value wave problem is treated to clarify the basic idea of the new method. Then the method is implemented for two dimensional unsteady transonic flow problems. The introduction of the concept of a quasi‐velocity‐potential simplifies the time marching integral equations and the treatment of trailing vortex sheet condition. The numerical calculations show that the method is reasonable and rel

ISSN:0029-5981    

DOI:10.1002/nme.1620340205

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe variety of flow regimes (steady separated, periodically separated‐‘Karman vortex street’, unsteady turbulent) and their characteristic peculiarities (separation and reattachment points, secondary separation, boundary layer, instability of the shear mixing layer, etc.) require the construction of effective numerical methods, which will be able to simulate adequately the considered flows.MERANGE  SMIF–a splitting method for physical factors of incompressible fluids1‐is used for calculations of the steady and unsteady fluid flows past a circular cylinder in a wide range of Reynolds numbers (10°

ISSN:0029-5981    

DOI:10.1002/nme.1620340206

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe flow through a highly offset subsonic diffuser with cross‐sectional profiles that varied from rectangular at the duct entrance to circular a t the engine face was numerically simulated. A multizonal approach combined with a two‐grid topology was used to represent both the internal and external flow fields, and an implicit, approximately‐factored, partially flux‐split finite‐difference algorithm was used to solve the three‐dimensional thin‐layer Navier‐Stokes equations. The computed static pressures along the inlet wall and total pressures on the engine face were compared with experimental data. In addition, the overall flow field within the duct was examined in detail. Good agreement is shown between experiment and computations, with the limiting factor being the lack of a reliable turbulence model for interna

ISSN:0029-5981    

DOI:10.1002/nme.1620340207

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe present report deals with many applications of different numerical methods to calculations of three‐dimensional stationary supersonic flows around aerodynamic configurations. Both an inviscid non‐heat‐conducting perfect gas and a real high‐temperature gas with physical‐chemical processes are considered. The results of some investigations carried out during recent years in the U.S.S.R. are reviewed. A brief description of applicable numerical methods is presented. A number of results are discussed both for separate parts of a flying vehicle and for whole configurations. Some gasdynamic effects, and aerodynamic and thermal characteristics are analysed. Among the aerodynamic elements we consider pointed and blunted nose parts of configurations, air intakes, wing and stabilizers. Also more complicated cases are considered such as compound aerodynamic objects and configurations modelling different kinds of whole flying vehicles (missile, aircraft, sp

ISSN:0029-5981    

DOI:10.1002/nme.1620340208

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA simple high resolution finite difference technique is presented to approximate weak solutions to hyperbolic systems of conservation laws. The method does not rely on Riemann problem solvers and is therefore easy to extend to a wide variety of problems. The overall performance (resolution and CPU requirements) is competitive with other state‐of‐the‐art techniques offering sharp non‐oscillatory shocks and contacts. Theoretical results confirm the reliability of the approach for linear systems and non‐linear scalar

ISSN:0029-5981    

DOI:10.1002/nme.1620340209

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWhen explicit time marching algorithms are used to reach the steady state of problems governed by the Euler equations, the rate of convergence is strongly impaired both in the zones with low Mach number and in the zones with transonic flow, e.g. Mach ⩽ α and | Mach − 1| ⩽ α, with α ⩽ 0·2. The rate of convergence becomes slower as α diminishes.We show in this paper, with analytical and numerical results, how the use of a preconditioning mass matrix accelerates the convergence in the aforementioned ranges of Mach numbers.The preconditioning mass matrix (PMM) we advocate in this paper can be applied to any FEM/FVM that uses an explicit time marching scheme to find the steady state. The method's rate of convergence to the steady state is studied, and results for the one‐ and two‐dimiensional cases are presented.In Sections 1‐3, using the one‐dimensional Euler equations, we first explain why there exists a slow rate of convergence when the plain lumping of mass is used. Then the convergence rate to steady solutions is analysed from its two constituents, that is, convergence by absorption at the boundaries and by damping in the domain. Next we give the natural solution to this problem, and with several examples we show the effectiveness of the proposed mass matrix when compared with the plain scheme.In Sections 4‐8 we give the multidimensional version of the preconditioning mass matrix. We make a stability analysis and compare the group velocities and damping with and without the new mass matrix. To finish, we show the velocity of convergence for

ISSN:0029-5981    

DOI:10.1002/nme.1620340210

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper report progress on a technique to accelerate the convergence to steady solutions when the streamline‐upwind/Petrov‐Galerkin (SUPG) technique is used. Both the description of a SUPG formulation and the documentation of the development of a code for the finite element solution of transonic and supersonic flows are reported. The aim of this work is to present a formulation to be able to treat domains of any configuration and to use the appropriate physical boundary conditions, which are the major stumbling blocks of the finite difference schemes, together with an appropriate convergence rate to the steady solution.The implemented code has the following features: the Hughes' SUPG‐type formulation with an oscillation‐free shock‐capturing operator, adaptive refinement, explicit integration with local time‐step and hourglassing control. An automatic scheme for dealing with slip boundary conditions and a boundary‐augmented lumped mass matrix for speeding up convergence.It is shown that the velocities at which the error is absorbed in and ejected from the domain (that is damping and group velocities respectively) are strongly affected by the time step used, and that damping gives an O(N2) algorithm contrasting with theO(N)one given by absorption at the boundaries. Nonetheless, the absorbing effect is very low when very different eigenvalues are present, such as in the transonic case, because the stability condition imposes a too slow group velocity for the smaller eigenvalues. To overcome this drawback we present a newmass matrixthat provides us with a scheme having the highest group velocity attainable in all the components.In Section 1 we will describe briefly the theoretical background of the SUPG formulation. In Section 2 it is described how the foregoing formulation was used in the finite element code and which are the appropriate boundary conditions to be used. Finally in Section 3 we will show some results obtained w

ISSN:0029-5981    

DOI:10.1002/nme.1620340211

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY