prevent negative values for passive tracer concentration
Hi, I am running a simulation where I have a passive tracer with a non-zero concentration in a small portion of the domain and a zero concentration everywhere else. I would like to prevent negative values for the passive tracer concentration. I have tested different advection scheme (UP, WENO) and different mixing scheme (LMD, GLS) but they all yield pretty strong negative values. Is there a way to prevent those? Thank you, Bertrand