ANSYSCFX础训练课程9.pptVIP

--For subdomain models (heat source, sink) --For rotating/stationary regions --To take advantages of other meshing approaches, eg. Hex or swept mesh in long/thin regions When a direct computation of the dependent variables can be made in terms of known quantities, the computation is said to be explicit. In contrast, when the dependent variables are defined by coupled sets of equations, and either a matrix or iterative technique is needed to obtain the solution, the numerical method is said to be implicit. the iteration steps usually do not correspond to a realistic time-dependent behavior. In fact, it is this aspect of an implicit method that makes it attractive for steady-state computations, because the number of iterations required for a solution is often much smaller than the number of time steps needed for an accurate transient that asymptotically approaches steady conditions. The principal reason for using implicit solution methods, which are more complex to program and require more computational effort in each solution step, is to allow for large time-step sizes. In an explicit numerical method S would be evaluated in terms of known quantities at the previous time step n. An implicit method, in contrast, would evaluate some or all of the terms in S in terms of unknown quantities at the new time step n+1. Since new quantities then appear on both the left and right side of the Q-equation, it is said to be an implicit definition of the new n+1 values. Usually a matrix or iterative solution must be used to compute the new quantities. unconditionally stable? This situation never occurs with explicit methods, which are always conditionally stable. * * * Additional Variables 7* ANSYS, Inc. Proprietary ? 2009 ANSYS, Inc. All rights reserved. April 28, 2009 Inventory #002598 Training Manual Sources 7-* ANSYS, Inc. Proprietary ? 2009 ANSYS, Inc. All rights reserved. April 28 2009 Inventory #002598 Training Manual Domain Interfaces 7-* ANSYS, Inc. Proprieta