Flow evolution of an internal solitary wave generated by gravity collapse

•This paper reports the detailed process on the evolution of the flow field for generating a depression ISW by gravity collapse in a flume having a pycnocline.•A finite volume based Cartesian grid method is adopted to directly resolve the Navier–Stokes equations and the general mass continuity equation.•The initial vortex remains identical for the same step depth but the decrease in its strength is significant as the depth of upper layer increases.•The step depth influences the vertical structure of the initial vortex more than the upper/lower layer depth ratio does on wave generation.

Numerical simulations are performed to investigate the flow evolution of a depression ISW generated by gravity collapse in a fluid system with a density pycnocline. A finite volume based Cartesian grid method is adopted to directly resolve the Navier–Stokes equations and the general mass continuity equation. Results of the numerical computation are validated by comparing with that of laboratory experiment. Numerical results reveal the initial vortex remains identical for the same step depth but the decrease in its strength is significant as the depth of upper layer increases. However, step depth influences the vertical structure of the initial vortex more than the upper/lower layer depth ratio does on wave generation.