34. TURBULENCE Namelist

34.1. Overview

The presence of the TURBULENCE namelist enables a simple algebraic turbulence model for viscous flow problems. The turbulent kinetic viscosity \(\nu_t = (\mu_t/\rho)\) is taken to be

(34.1.1)\[\nu_t = c_{\mu}k^{\frac{1}{2}}l\]

where \(c_{\mu}\) is the proportionality constant, \(l\) is a length scale corresponding to the eddy size, and

(34.1.2)\[k = f.\frac{1}{2}.u^2\]

is the local turbulent kinetic energy per unit mass, modeled as a fraction \(f\) of the mean kinetic energy. The namelist variables give values for the model parameters. See Truchas Physics and Algorithms for more details.

34.2. TURBULENCE Namelist Features

Required/Optional : Optional

Single/Multiple Instances: Single

CMU

Description : Value of the parameter \(c_{\mu}\) in Eq.34.1.1.
Type        : real
Default     : 0.05
Valid Values: \(\gt 0\)
Notes       : The default value is appropriate in most situations.

KE_fraction

Description : Value of the parameter \(f\) in Eq.34.1.2.
Type        : real
Default     : 0.1
Valid Values: (0,1)
Notes       : The default value is appropriate in most situations.

Length

Description : Value of the parameter \(l\) in Eq.34.1.1.
Physical dimension: L
Type        : real
Default     : none
Valid Values: \(\gt 0\)
Notes       : The value should correspond to the size of the turbulent eddies. In turbulent pipe flow, for example, this would be one third the pipe radius.