精通ANSYS FLUENT 13各种计算格式、加速算法以及VOF模型

精通ANSYS FLUENT 13各种计算格式、加速算法以及VOF模型

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For Scale-Resolving Simulations (SRS), specific discretization and solver settings are required to achieve optimal accuracy with minimal numerical effort.

The recommendations are based on incompressible, single phase flow without chemical reactions or other complex additional physics.

In most cases, this will mean that a higher effort needs to be invested into the coupling of the equations (e.g. lower time step, reduced under-relaxation, higher iteration count, smaller residuals), in order to avoid a de-coupling of different physical phenomena.

It is generally recommended to use the pressure-based solver, as it offers optimized schemes for resolving turbulence relative to the density based solver.

For Scale-Resolving Simulations, optimal numerics settings are essential for achieving accurate results in an acceptable time frame. Numerics settings therefore have to be chosen to provide an optimal balance between accuracy and robustness.

It is generally recommended to initialize the solution from a (reasonably) converged RANS simulation.

For Scale-Resolving Simulations, the resolution of the turbulent structures in time is essential for the success of the simulation. This is, to the largest extent, defined by the selected time step. As the SRS model is operating at the grid limit, you should select a time step that ensures a Courant-Friedrichs-Levy (CFL) number of

The recommendation of CFL =1 should be applied in the main SRS region in combination with a uniform isotropic grid. It is recommended to vary the time step for each type of application and explore its optimal value. This can substantially save on computing costs.In most transient cases, the CFL number should be set to 1e7with an explicit relaxation of 1.0.

The time derivative should be computed by the Second Order Implicit option

(压力速度分离算法4种，压力速度耦合算法1种，即coupled，其只能在pressure-based solver（压力基）求解器适用)。下面介绍五种算法的异同。

1.压力基压力速度分离算法 : SIMPLE, SIMPLEC, PISO, Fractional Step (NIAT,FSM) ANSYS FLUENT provides four segregated types of algorithms: SIMPLE, SIMPLEC, PISO, and (for time-dependant flows using the Non-Iterative Time Advancement option (NITA)) Fractional Step (FSM). These schemes are referred to as the pressure-based segregated algorithm. Steady-state calculations will generally use SIMPLE or SIMPLEC, while PISO is recommended for transient calculations. PISO may also be useful for steady-state and transient calculations on highly skewed meshes. Pressure-velocity coupling is relevant only for the pressure-based solver.

SIMPLE and SIMPLEC

SIMPLE is the default, but many problems will benefit from using SIMPLEC, particularly because of the increased under-relaxation that can be applied, as described below.

For relatively uncomplicated problems (laminar flows with no additional models activated) in

which convergence is limited by the pressure-velocity coupling, you can often obtain a converged