Initial Values
The initial values serve as initial conditions for a transient simulation or as an initial guess for a nonlinear solver in a stationary simulation. Note that for a transient compressible-flow simulation employing a material for which the density depends on the pressure (such as air), discontinuities in the initial values trigger pressure waves even when the Mach number is small. The pressure waves must be resolved and this puts a restriction on the time step.
Initial Values
Initial values or expressions should be specified for the Velocity field u and the Pressure p.
When Include gravity is selected and Use reduced pressure not selected in the interface Physical model section, the Compensate for hydrostatic pressure approximation (named Compensate for hydrostatic pressure for compressible flows) checkbox is available and selected by default. When it is selected, the hydrostatic pressure is automatically added to the pressure entered in p user input.
In the Turbulent Flow interfaces, initial values for the turbulence variables should also specified. Depending on the turbulent flow interface being used, additional initial values may be required for:
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Turbulent kinetic energy k
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Turbulent dissipation rate ep
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Reciprocal wall distance G
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Specific dissipation rate om
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Kinematic Reynolds stresses uu, vv, ww, uv, uw, vw
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Undamped turbulent kinematic viscosity υ0
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Wall distance in viscous units yPlus (dimensionless). Under normal circumstances the default value need not be changed.
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Tangential velocity in viscous units uPlus (dimensionless). Under normal circumstances the default value need not be changed.
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Turbulent relative fluctuations zeta
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Elliptic blending function alpha