Nays2DV is a computational model for simulating two dimensional vertical plane flow. Model was developed for calculation of vertical movement of fluid (density flow). The Nays2DV solver is developed by Professor Yasuyuki Shimizu from Hokkaido University.
When the density of a fluid changes due to temperature or turbidity, a buoyancy force occurs due to the density difference with the surrounding fluid and this buoyancy force induces a flow. This is called density flow. Density flow is important in problems in lakes, reservoirs and estuaries.

online manual is here
for iRIC v3

The source code is published here.
https://github.com/iRICsolvers/v4_nays2dv