Ramakanth Munipalli


This page has some information pertaining to my current and past research work.

The CFD taskforce at UT-Arlington, in their home base ..... !


Magnetohydrodynamics

I am interested in the proper CFD treatment of flow physics in MHD. Physical issues in the implementation of MHD-based flow control are numerous, fascinating and very hard to accurately model. Some of the things I am interested in developing CFD models of, include:
Adaptive Grid Generation in CFD

M.S. Thesis, Spring 1992, MAE Department : "Linearized Adaption in Structured Grids"

"Linearized adaption in structured grids," by R. Munipalli and D.A. Anderson, AIAA 95-08562, presented at the AIAA 33rd Aerospace Sciences Meeting, Reno NV, Jan 9-12 1995

Conventional methods of generating adaptive structured grids use the Poisson equations in a transformed non-linear form. This raises issues such as existence and uniqueness of the numerical solution to these equations. Further, non-linear equations necessarily involve an iterative solution process. A completely linear formulation is presented in this paper. CPU time comparisons show a savings of about 3 times over Thompson's scheme. The use of Green's functions as an alternative to Poisson computation is presented.

"An Adaptive Grid Scheme Using the Boundary Element Method," Vol. 127, No. 2, pp. 464-472, Journal of Computational Physics, September 1996

This paper deals with the Boundary Element Method (BEM) as a natural extension to Green's function solution to adaptive grid generation problems that was presented in the AIAA conference paper. Discrete vortex doublets are placed in the region of interest in order to attract grid lines. The orientation of these doublets can be used to obtain orthogonality. A proof is presented to show that a linear harmonic source function remains harmonic under a transformation of coordinate systems if the function is also harmonic in a conformal coordinate system. This is of immense use in the BEM, since the volume integrals vanish trivially on the application of Green's identity.

"A Singularity Based Scheme to Adapt Structured Grids," presented at The 5th International Conference on Numerical Grid Generation in CFD and related fields , Mississippi State University, MS, April 1-5, 1996.


Optimization and Design Techniques

"Application of Optimization Techniques To Inlet Design," by Ramakanth Munipalli, Ganesh Wadawadigi, Dale A. Anderson and Donald R. Wilson, AIAA 95-1824, presented at the AIAA 13th Applied Aerodynamics conference, San Diego CA, June 19-22, 1995

This paper examines the design optimization process for high speed air intakes. Air intakes of various types (internal compression, isentropic external compression and mixed compression) are analyzed from the point of view of obtaining an optimally low total pressure loss. Alternately, the criterion of optimal combustion chamber Mach number is studied for these intakes. The study shows these two as contradictory requirements at high speeds. An approximate optimization method for these problems involving boundary layer and equilibrium air chemistry is also presented. Though all computations have been performed on the Cray C-90, leads to a better CPU time expending strategy are given.


High Speed Flows under Chemical and Thermal non-equilibrium

My current research is in the area of non-equilibrium flows in the Hypersonic context. Besides being the most realistic phenomena that are encountered at such speeds, non-equilibrium processes are also the least understood. The CFD effort in this area involves coming up with appropriate models to simulate the relaxation processes in gas flows. We are using the two-temperature model to predict gas properties. Current model also has 11 chemical species, 26 possible chemical reactions, and applied electric, magnetic fields coupled with microwave radiation that add energy to the flow and cause charge separation. It is proposed to use this simulation in the design of a realistic magnetohydrodynamic wind tunnel that can reach Mach 20.

"Numerical Simulation of a Nonequilibrium Ionization MHD Accelerator," by Ramakanth Munipalli and Dale Anderson, Invited paper at the Fall Meeting of the Texas section of American Physical Society (APS), University of Texas at Arlington, October 10-12, 1996.

Abstract:A realistic simulation of hypersonic flight conditions in a ground based test has been a challenging issue in experimental fluid mechanics. Work is underway in the Aerodynamics Research Center (ARC) at the University of Texas at Arlington (UTA) to construct a hypersonic test facility in which high temperature air is accelerated through a Magneto Hydrodynamic (MHD) channel. The flow is known to be influenced substantially by chemical and thermal nonequilibrim effects. Computer simulation of such a flow involves the proper physical and numerical modelling of complex flow phenomena. An appropriate set of equations chosen to model such a flow will be presented in this paper. The governing equations will be essentially in the format of the Parabolized Navier Stokes (PNS) equations, where the dissipative terms in the stream-wise direction are dropped in order to make the system of equations parabolic. A recent existing code called the Upwind PNS (UPS) will be used to model chemical and thermal nonequilibrium. Source terms will be added to this code in order to simulate the MHD aspects of the flow. Preliminary results will be shown for supersonic ionized air flow in a 2-dimensional duct. The air model used will comprise of 7 chemical species with 26 possible chemical reactions among them. A multi-temperature model will be used to model thermal nonequilibrium.

Of Related Interest:

Fusion Engineering Group at UCLA, The Computational MHD group at Michigan