Turbulent entrainment in stably stratified systems
Stratified (layered by density) turbulence is a special case of turbulent flows. The main difference is due to the additional effect through the body force (density times gravity) that enters the equations of motion and modifies the balances in the Navier-Stokes equations. The differences are very peculiar and stratified turbulent flows are many times counter intuitive to our perception and analysis.
We study various aspects of stratified flows. Some time ago we tried to measure the force on a lifting airfoil that accelerates from rest. Another project was a turbulent patch that grows in a stably stratified environment and we study the way its very early, initial growth is modified due to buoyancy. Very detailed local information around the propagating turbulent interface has been obtained using PIV. The third project is an attempt to study the motion of particles in Lagrangian framework across the turbulent/non-turbulent interface. For this project we had to design a steady-state experiment and we therefore work with a two-layer system. And now we move to the turbulent/non-turbulent interfaces with particles. Many years of research and a long way is still ahead.