Turbulent Quantities for Initial Values and Boundary Conditions

The turbulent quantities in the properties file (id/project.prop) are labeled tu and diss. Here, tu is the turbulent intensity specified as a percentage with allowed values between 0 and 1. diss is a reference length which is used to calculate the initial dissipation, using the formula $\frac{\sqrt{en_{\mathit turb}^3}}{l_r}$, where $en_{\mathit turb}$ is the turbulent kinetic energy derived from the turbulent intensity and the velocities.

In the file funcbcs.F the turbulent kinetic energy fte is specified in $\frac{\mbox{m}^2}{\mbox{s}^2}$. The tunable parameter for the dissipation is the reference length rlength, which is used to calculate the dissipation employing the above-mentioned formula. To find meaningful values for the turbulent kinetic energy, start with $\texttt{fte}=1.5I_t^2u_{in}^2$, where $I_t$ is the turbulent intensity and $u_{in}$ is the maximum inflow velocity. Then stop the calculation after a some iterations and replace the previous value with the turbulent kinetic energy at a location two to five control volumes inward from the inlet boundary. Repeat, until a sensible value has been found.