When making the time step small, how should other parameters be changed

Hello guys, I recently want to modify this model in order to do some research.
In the case of studying 2D Rayleigh-Taylor instability, if I want the time step to be a small amount (say 0.01) instead of unit length, how should I adjust some parameters of this case like D and sigma accordingly to ensure the numerical results stable.
And here are the original parameter: interface width D=4, surface tension coefficient sigma=5e-5
thank you u guys!