Turbulent Lubrication Mode

Turbulent Lubrication Model = {model_name}

Description / Usage

This card activates a turbulent model for viscosity in the lub_p equation. Currently one model {model_name} is permissible:

PRANDTL_MIXING

This model is used to determine the pre-multiplier on the molecular viscosity in the Reynolds lubrication equation. For confined, laminar flow, this multiplier is 12. For turbulent flow it is taken as K(Re), where Re is the local Reynolds number. Specifically, invoking a analytical approximation for K from Hirs (1973), we set k0 according to the: Reynolds number Re= :ρh U μ For 0 < Re < 2000 K0=12 (Laminar case), Else 2000 < Re < 100000 K0 = 0.05Re 3/4 Here the wall velocity is used to compute The Reynolds number, as this turbulence model is specific to turbulent Couette flow.

Examples

Following is a sample card:

Turbulent Lubrication Model = PRANDTL_MIXING

Technical Discussion

Several other models can be implemented in this instance. We chose this simple model which derives from Prandtl mixing length theory.

References

G.G. Hirs, “Bulk flow theory for turbulence in lubricant films”, Trans. ASME, ser. F, 95, pp 137-146, 1973.