摘要:

AbstractA new boundary element method is described for calculation of the steady incompressible laminar flows. The method is based on the well‐known SIMPLE algorithm. The new boundary element method allows one to find the fields of the pressure and velocity corrections without inner iterations, thus reducing the computational time drastically. This makes it different from the method developed by Patankar and Spalding.32However, the new method demands a much larger computer strorage. The boundary integral equations are discretized with the help of constant boundary elements and constant cells. The values of the integrals along the boundary elements and the cells for the two‐dimensional domain are found analytically. To preserve the stability in the iteration process, under‐relaxation for the convection terms is used. This paper gives the results of calculations of the flows between two plane parallel plates atRe= 20 andRe= 200, the flows in a square cavity with a moving upper lid atRe= 1 andRe= 100 and the flow in a plane channel with sudden symmetric expansion atRe

ISSN:0271-2091    

DOI:10.1002/fld.1650160702

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractStandard preconditioners such as incomplete LU decomposition perform well when used with conjugate gradient‐like iterative solvers such as GMRES for the solution of elliptic problems. However, efficient computation of convection‐dominated problems requires, in general, the use of preconditioners tuned to the particular class of fluid‐flow problems at hand. This paper presents three such preconditioners. The first is applied to the finite element computation of inviscid (Euler equations) transonic and supersonic flows with shocks and uses incomplete LU decomposition applied to a matrix with extra artificial dissipation. The second preconditioner is applied to the finite difference computation of unsteady incompressible viscous flow; it uses incomplete LU decomposition applied to a matrix to which a pseudo‐compressible term has been added. The third method and application are similar to the second, only the LU decomposition is replaced by Beam‐warming approximate factorization. In all cases, the results are in very good agreement with other published results and the new algorithms are found to be competitive with others; it is anticipated that the efficiency and robustness of conjugate‐gradient‐like methods will render them the method of choice as the difficulty of the problems that they are applied to

ISSN:0271-2091    

DOI:10.1002/fld.1650160703

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe fluid flow in distensible tubes is analysed by a finite element method based on an uncoupled solution of the equations of wall motion and fluid flow. Special attention is paid to the choice of proper boundary conditions. Computations were made for sinusoidal flow in a distensible uniform tube with the Womersley parameter α = 5, and a ratio between tube radius and wavelenth from 0·0001 to 0·5. The agreement between the numerical results and Womersley's analytic solution depends on the speed ratio between fluid and wave velocity, and is fair for speed ratios up to 0·05. The analysis of the flow field in a distensible tube with a local inhomogeneity revealed a marked influence of wave phenomena and wall motion on the velocity profi

ISSN:0271-2091    

DOI:10.1002/fld.1650160704

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe recent interest in propeller noise generation, stimulated by development of new propeller types for commerical propjets, has generated a need for the ability of measure the noise characteristics of propellers. However, wind tunnel noise measurements are affected by reflections from the wind tunnel walls. Computer codes predicting the free‐field noise of a propeller and its noise field in a circular wind tunnel allow validating the use of wind tunnel measurements to predict free‐field noise characteristics. A wind tunnel contains flow which is uniform in the duct axial direction, but can vary in the radial direction. It can be shown that a third‐order differential equation governs the acoustic pressure field for such a duct containing radially sheared subsonic flow. This third‐order problem is then posed as a coupled pair of equations which are second‐order in terms of acoustic density and first‐order in terms of an artificial variable which represents the effects of the flow being sheared. It is shown that this form of the problem allows a natural extension of the existing numerical solution techniques for non‐sheared flow. The sheared flow problem is presented, and a finite element method is developed to yield a solution for propeller‐type acoustic forces. The finite element code and method are refined with numerical experiments, and results are presented for a specific propeller and duct geometry. Good agreement is shown between this method and an alternate approach to the sheared flow problem using a piecewise constant representation of the velocity in the boundary layer. This validates both the nu

ISSN:0271-2091    

DOI:10.1002/fld.1650160705

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA finite difference scheme based on flux difference splitting is presented for the solution of the one‐dimensional shallow‐water equations in open channels, together with an extension to two‐dimensional flows. A linearized problem, analogous to that of Riemann for gas dynamics, is defined and a scheme, based on numerical characteristic decomposition, is presented for obtaining approximate solutions to the linearized problem. The method of upwind differencing is used for the resulting scalar problems, together with a flux limiter for obtaining a second‐order scheme which avoids non‐physical, spurious oscillations. The scheme is applied to a one‐dimensional dam‐break problem, and to a problem of flow in a river whose geometry induces a region of supercritical flow. The scheme is also applied to a two‐dimensional dam‐break problem. The numerical results are compared with the exact solution, or other numerical results

ISSN:0271-2091    

DOI:10.1002/fld.1650160706

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650160707

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650160701

出版商:John Wiley&Sons, Ltd    

年代:1993

数据来源: WILEY