Concerns have been raised as to the dependency of the solutions of turbulent flows in FLOW-3D® 1on the maximum ”turbulent mixing length,” 𝑇𝐿𝐸𝑁, which is set by the user when a two-equation turbulence model is used. This parameter acts as a limiter on the turbulent length scale which in turn limits the minimum turbulent dissipation. It has been observed that if the value is not chosen appropriately the results could become physically unrealistic. In order to resolve this issue, modifications have been made to the two-equation turbulence models to construct local bounds on turbulent length and time scales. This technical note shows that these changes effectively eliminate the sensitivity of the solution to the value of 𝑇𝐿𝐸𝑁.
Some valuable discoveries were made along the way which led to more modifications of the turbulence models in FLOW-3D that further improved the results. The test cases discussed here include both simple as well as complex flows. Starting with the simplest flow configurations and obtaining reasonably accurate results permits the consideration of more complex cases. The data and conclusions documented here should be used as a starting point for any other changes to the turbulence models in FLOW-3D.