摘要:

AbstractSudden total collapse of a dam holding back a reservoir of water, whenever it occurs, becomes formidably impressive in the extent of destruction with which it is associated. The movement on a dry bed of a two‐dimensional flood wave resulting from the break of a dam has been one of the most important and challenging subjects in rapidly varied unsteady flows from the computational point of view. An implicit time‐marching finite volume numerical scheme was developed and subsequently applied for the solution of the two‐dimensional unsteady open channel flow equations written in conservation form. In order to avoid the problems associated with a conventional grid system, a body‐fitted non‐orthogonal local co‐ordinate system was utilized. The proposed numerical technique was applied to determine the stage hydrographs, water surface profiles and velocities of flood flows resulting from suddenly breached storage dams. Predictions were compared with an analytical solution, with available numerical solutions using MacCormack's two‐step explicit scheme and with experimental measurements. Agreement between predictions and measurements regarding the wave front advancement and stage hydrographs is considered to be

ISSN:0271-2091    

DOI:10.1002/fld.1650140602

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe primary aim of this paper is to demonstrate how the ‘design‐of‐experiments’ techniques which are successful in physical experiments could also be adapted to a numerical simulation code.As an example this technique is applied to a general finite difference code used for predicting three‐dimensional turbulent recirculating flows. Here the equations for velocities and continuity are solved using the algorithm called SIMPLE, which stands for semi‐implicit method for pressure‐linked equations. Physical modelling of turbulence is taken care of by means of kinetic energy and turbulence dissipation rate equations.The objective is to optimize the underrelaxation factors of primary and secondary flow variables so that the number of iterations required for convergence is minimum. This is done by the orthogonal array technique (a particular type of design‐of‐experiment technique).The geometry considered for this purpose is that of a simple gas turbine can combustor and the study is restricted to the isothermal non‐reacting condition.Tests are carried out on three different grid configurations. In each case the underrelaxation factor for velocities contributed most to speed up the rate of convergence. Also, for each grid configuration the underrelaxation factor settings for minimum iterations for convergence was found to be same. Hence it is proposed that when doing grid independence tests for any similar flow situation, all the underrelaxation factors could be optimi

ISSN:0271-2091    

DOI:10.1002/fld.1650140603

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA finite element method for the transient incompressible Navier–Stokes equations with the ability to handle multiple free boundaries is presented. Problems of liquid–liquid type are treated by solving two coupled Navier–Stokes problems for two separate phases. The possibility to solve problems of liquid–gas, liquid–liquid–gas or liquid–liquid–liquid type is demonstrated too. Surface tension effects are included at deformable interfaces.The method is of Lagrangian type with mesh redefinition. A predictor‐corrector scheme is used to compute the position of the deformable interface with automatic control of its accuracy and smoothness. The method is provided with an automatic choice of the time integration step and an optional spline filtration of the truncation error at the free surface. In order to show the accuracy of the method, tests and comparisons are presented. Numerical examples include motion of bubbles a

ISSN:0271-2091    

DOI:10.1002/fld.1650140604

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA new algorithm based on spectral element discretizations and flux‐corrected transport (FCT) ideas is developed for the solution of discontinuous hyperbolic problems. A conservative formulation is proposed, based on cell averaging and reconstruction procedures, that employs a staggered grid of Gauss–Chebyshev and Gauss–Lobatto–Chebyshev discretizations. In addition, high‐order time‐differencing schemes, a flux limiter and a general spectral filter are employed to improve the quality of the solution. It is demonstrated through model problems of linear advection and examples of one‐dimensional shock formation that the proposed algorithm leads to stable, non‐oscillatory solutions of high accuracy away from discontinuities. Typically, spectral or spectral element methods perform very poorly in the presence of even weak discontinuities, although they produce only exponentialy small errors for smooth solutions. Spectral element–FCT methods can provide spectral properties (i.e. minimum dispersion and diffusion errors) as well as great flexibility in the discretization, since a variable number of macroelements or collocation points per element can be employed to accommodate both accuracy and geome

ISSN:0271-2091    

DOI:10.1002/fld.1650140605

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe mixed form of the areal groundwater flow equations is solved with a least‐squares finite element procedure (LESFEM). Hydraulic head andx‐ andy‐directed fluxes are state variables. Physical parameters and state variables are approximated using a bilinear basis. Grid refinements and irregular domain boundaries are implemented on rectangular meshes.Residuals are constructed at collocation points for conservation of mass and Darcy's law. Boundary condition residuals are constructed at discrete points along the boundary. The residuals are weighted, squared and summed. A set of algebraic equations is formed by taking the derivatives of the weighted sum of the squares of the residuals with respect to each unknown parameter in the approximation for the state variable and setting them to zero.Proper choice of a potential scaling parameter and residual weights is essential for the effective application of the algorithm. Test problem results demonstrate that the method is effective for both transient and steady state cases.The LESFEM algorithm generates aC°‐continuous velocity field. The continuous velocity field and the rectangular mesh simplify the implementation of algorithms that require tracking. In addition, rectangular meshes simplify mesh and boundary ge

ISSN:0271-2091    

DOI:10.1002/fld.1650140606

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650140607

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650140608

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650140601

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY