[yujin_cfd]

Hi everyone,

I am trying to simulate airflow over an airfoil using unsteady RANS, I am employing a realizable k epsilon model with Menter-Lechner wall treatment. The Reynolds number is 100000. This model gave me better results of lift and drag ratio for validation compared with k-w SST model and I am relying on this particular model.
my simulation has 150 timesteps with 0.1s step size, thus simulating the flow over 15s. I implemented a UDF to vary the k and epsilon parameters over each time step to note the effect of varying turbulence intensity.
I did specify a fixed turbulence intensity for each interval of time. That is 0 to 1s, 1 to 2s, and so on. It recalculates the k and epsilon and varies it during the simulation. My input intensity values followed an upward trend, but after running the simulation it is showing a downward trend. But both follow the same distribution or curve pattern, only the slope is opposite for the trend. I expected or inputted a positive slope but got a negative one.
Does it mean that with each time step, the flow determines the next k and epsilon values to be ste? Can anyone help me with this?

Thanks in advance.