Research Interests

EMHD

The idea is to put cleverly designed small electro-magnetic tiles on surfaces in the hope that, by controling the pulsing pattern and pulsing magnitude of electrodes, one can influence flow in a way so that to achieve drag reduction in a turbulent boundary layer composed of slightly conductive fluid such as sea water. This can be of great use for ships, submarines and torpedos. Two examples are

4-Phase Pulsing

In this case, 4 X 8 electro-magnetic tiles are mounted on the lower wall of a channel with turbulent flow of Reynolds number 3280 running through it. The tiles are pulsed so that at each phase (for a certain peoriod of time) one of 4 tiles in each row, alltogether 8 tiles, are activated, and one cycle contains 4 phases. These computations were done using a spectral-element/Fourier method on 64 nodes of the IBM SP2 at the Cornell Theory Center. Some of our results are shown below:

NUWC Project

This project consists of two parts. The first part is to model a single Lorentz force actuator (which is another way of saying electro-magnetic tile, difference being maybe, that it's bigger) and turn it on in first a initially quiescent flow and later a laminar channel flow. After achieving fairly well comparison with the experiments carried out at NUWC (Naval Underwater Warfare Center), we come to the second part, which is to let a turbulent flow run over a surface mounted with a specially designed board of electro-magnetic tiles. In our simulation, we use 8 X 16 tiles and we pulse the electrodes following a 16-phase pattern. After analyzing the data at the end of each phase, we find a very interesting phenomenon: the turbulent structure of the whole flow field is being pushed consistently in one direction! It seems that a certain kind of structure wave has been generated. A movie to show this phenomenon is now ready. Also, each frame can be checked out separately. What's plotted here is the shear stress contour (scaled to the same range) at the end of each phase. Active positive electrodes are white, while active negative electrodes are black.

NOTE These computations were done using a spectral-element/Fourier method on 16 nodes of the IBM SP2 at the Center for Fluid Mechanics at Brown University.

MHD: Preliminary Results

Here we first calculate the solution for the Orszag-Tang vortex problem and then simulate a viscous MHD flow passing a cylinder. In both cases we use a 2D compressible viscous MHD code written by T. Warburton. Discontinuous Galerkin Methods are combined with Nektar in this code. Some results are shown below: