Hidrológiai Közlöny 1995 (75. évfolyam)

1. szám - Gáspár Csaba–Józsa János–Simbierowicz, Pawel: Új szemléletmód a numerikus hidraulikában. III. Sekély tavakban fellépő szélkeltette áramlások modellezése egyenlőtlen hálók használatával

26 HIDROLÓGIAI KÖZLÖNY 1995. 75. ÉVF. 1. SZÁM New Approach iu Nuinerical Hydraulics III.Modeling Wind Induced Currents in Shallow Lakes with the Help of Irregular Grids Gáspár, Cs.-Józsa, J. —Simbierowicz, P. Abstract: A növel approach lo numerícal hydraulics is prcsented in four successive. These are entitled: I.Irregular grids, their generation and first applications. II.Difference schemes and multigrid methods on irregular grids. III.Modeling wind induced currents in shallow lakes with the help of irregular grids. IV.Lagrangian modeling of flow and Iransport processes with the help of irregular grids. The "növel approach" consists essentially of abandoning the equidistant finite-difference philosophy and replacing it with the more generál QT grid which provides irregular subdivision in space, is orthogonal, can be generated in a flexible way and is based on the recursively defined, systematic subdivision of and initial square. The analysis can thus be focused on the subtantially important subregions. When using the QT-grids, the grid and mátrix philosophy is replaced by graphs. An additional important feature of the new approach is the multigrid technique. Thanks lo the attractive properties of the QT-grids coupled with multigrid techniques i.e. the high speed of computation and the high degree of flexibility, the proposed new method is a competitive alternative to the earlier computational methods. In this paper, the method is applied to laké modeling. The steady and the unsteady shallow water equations are discretised and solved by using quadtree grids which are generated essentially by the shoreline. The method results in the same approximate solution as the traditional methods but introduces much less gridpoints: This fact and the use of the multigrid technique make the presented method much efficient than the traditional approachcs. Keywords: numerical hydraulics, flow modeling, grid, graph, multigrid, computational methods, shallow water equations.