摘要:

AbstractFinite element schemes for hyperbolic systems are applied to the St. Venant equations for one‐dimensional, unsteady, open channel flow. The comparative performances of the characteristic‐dissipative‐Galerkin, Taylor‐Galerkin and least squares finite element schemes are assessed by means of linear Fourier analysis and solution of idealized non‐linear wave propagation problems. Of particular interest is the behaviour of these schemes for the regressive wave component in both subcritical and supercritical flows. To assess the quality of the basic solution, the methods are compared without any additional artificial diffusion or shock‐capturing formulations. The balanced treatment of both wave components in the characteristic‐dissipative‐Galerkin method is illustrated. Also, the method displays little sensitivity to parameters variations. The Taylor‐Galerkin scheme provides good solutions, although oscillations due to wave dispersion and minimal diffusion of the regressive wave are displayed. Also, this method is somewhat sensitive to the time step increment. The least squares method is considered unsuitable for unsteady, open channel flow problems owing to its inability to propagate a regressive wave in a s

ISSN:0271-2091    

DOI:10.1002/fld.1650200202

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA semi‐implicit Lagrangian finite difference scheme for 3D shallow water flow has been developed to include an eddy viscosity model for turbulent mixing in the vertical direction. The α‐co‐ordinate system for the vertical direction has been introduced to give accurate definition of bed and surface boundary conditions. The simple two‐layer mixing length model for rough surfaces is used with the standard assumption that the shear stress across the wall region at a given horizontal location is constant. The bed condition is thus defined only by its roughness height (avoiding the need for a friction formula relating to depth‐averaged flow, e.g. Chezy, used previously). The method is shown to be efficient and stable with an explicit Lagrangian formulation for convective terms and terms for surface elevation and vertical mixing handled implicitly. The method is applied to current flow around a circular island with gently sloping sides which produce periodic recirculation zones (vortex shedding). Comparisons are made with experimental measurements of velocity using laser Doppler anemometry (time histories at specific points) and surface particle‐tracking

ISSN:0271-2091    

DOI:10.1002/fld.1650200203

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWe introduce a Eulerian/Lagrangian model to compute the evolution of a spray of water droplets inside a complex geometry. To take into account the complex geometry we define a rectangular mesh and we relate each mesh node to a node function which depends on the location of the node. The time‐dependent incompressible and turbulent Navier‐Stokes equations are solved using a projection method. The droplets are regarded as individual entities and we use a Lagrangian approach to compute the evolution of the spray. We establish the exchange laws related to mass and heat transfer for a droplet by introducing a mass transfer coefficient and a heat transfer coefficient. The numerical results from our model are compared with those from the literature in the case of a falling droplet in the atmosphere and from experimental investigation in a wind tunnel in the case of a polydisperse spray. The comparison is fairly good. We present the computation of a water droplet spray inside a complex and realistic geometry and determine the characteristics of the spray in the vicinity of obstac

ISSN:0271-2091    

DOI:10.1002/fld.1650200204

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe inviscid shallow water equations provide a genuinely hyperbolic system and all the numerical tools that have been developed for a system of conservation laws can be applied to them. However, this system of equations presents some peculiarities that can be exploited when developing a numerical method based on Roe's Riemann solver and enhanced by a slope limiting of MUSCL type. In the present paper a TVD version of the Lax‐Wendroff scheme is used and its performance is shown in 1D and 2D computations. Then two specific difficulties that arise in this context are investigated. The former is the capability of this class of schemes to handle geometric source terms that arise to model the bottom variation. The latter analysis pertains to situations in which strict hyperbolicity is lost, i.e. when two eigenvalues collapse into on

ISSN:0271-2091    

DOI:10.1002/fld.1650200205

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA new multiblock pressure‐based finite element algorithm has been developed. This methodology implements quadratic interpolation for both the elemental velocity and pressure fields. A direct streamline upwinding scheme previously developedby the authors is used to model the non‐linear inertia effects. Details of the algorithm and its multiblock foundation are provided along with validating test cases. The results presented clearly demonstrate the accuracy of this new approach and the differences in the pressure field for an element using quadratic versus the traditional bi linear approximation of the pressure fi

ISSN:0271-2091    

DOI:10.1002/fld.1650200206

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650200207

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650200208

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650200201

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY