Simulations Of Three-Dimensional Turbulent Flow With Complex Boundary Conditions

Computational fluid dynamics (CFD) is a combinative production of modem hydrodynamics, numerical mathematics and computer science, and is a new science - with powerful vital force. Along with the rapid development of CFD technology, it has been broadly used in increasing industry fields. In this dissertation, the simulations of the three-dimensional turbulent flows were conducted based on standard k-e turbulent model with body-fitted coordinates and staggering grid system. The SIMPLEC algoritlun was adopted in the numerical procedure.In 1999, the author has already formed a primary "wholesale computing methods", including the jointing boundary conditions into our calculating domain and letting no blind points in our simulations.The first research of this paper is keeping on study of the "wholesale computing methods", and expanding the specific jointing boundary conditions to a general circular array periodic boundary condition. The calculating results of the "wholesale computing methods" were compared with those of traditional ones. These results indicate that the "wholesale computing methods" can give much better results, and can be used in simulating flow that has circular array periodic boundary such as flow through rotational impellers.In chapter two, many complex boundaries were classified and the general "wholesale computing methods" were formed, hi "wholesale computing methods", we contain boundaries as many as possible into our calculating domain (not to be disturb by artificially setting). In case of cannot contained, we set the boundary condition according to its peculiarity (artificially setting).In this dissertation, we use both our own CFD program and commercial CFD software to simulate the 3-D flow in the river basin, and the commercial CFD software can greatly save our time and a great deal of simple but burdensome programming work.In this paper, we use AutoLISP programming language to pick up useful data from CAD drawing, then program the data, and then dump them into CFD usage. The program works from CAD to CFD can greatly increase our efficiency.After simulating of simplified sand funnel (the outer 180 ?channel) model, we can assume that there exist a secondary flow in the cross section of sand funnel, and it can give us the goal of the experiment: catching the secondary flow. Because of the disadvantage of the ADV instrument and limitation of experiment condition, the secondary flow was not approved in sand funnel.Of all boundary conditions, the free surface boundary must be the most complicated one. In this paper, we use commercial CFD software with VOF model to do our numerical simulation on sand funnel.The dams collapsing models and a testing model with many grids and cases were simulated, the results prove that VOF model can successfully used in simulation general free surface flow.The simulations of sand funnel tell us that the VOF model cannot simulate the flow in sand funnel because of its strongly vortex flow. The author gives some advices on simulating sand funnel, such as use "wholesale computing methods" to set the surface boundary and outflow boundary as they are.