SPECIALIZATION : Computational Fluid Dynamics

AWARDS : Alexander von Humboldt Fellow, JRD Tata Fellow(IISc), Aerospace Engineering Division Medal(I.E.)

PROFESSIONAL EXPERIENCE:
1991 - till date: Faculty Member, Aerospace Engg Dept, IIT Bombay, India
2000 & 2001: Visiting Faculty/Scientist, Mechanics Dept, RWTH Aachen, Germany
2002-2003: Alexander von Humboldt Fellow, Germany

PROFESSIONAL ACTIVITIES:
*External Expert Member of the Divisional Scientific Committee of CTFD Division,
 National Aerospace Laboratories, Bangalore, India (2005-07).
*Expert Member of University Grant Commission, Government of India (2007-09).
*Expert Member of National Board of Accreditation, AICTE, India (2007-09).
*Expert Member of Homi Bhabha National Institute (HBNI), Mumbai.
*Reviewer for International Journal for Heat and Fluid Flow, International Journal
 of Numerical Methods in Fluids, Computers & Fluids, Differential Equations and Dynamical
 Systems: An International Journal for Theory and Application, Journal Aeronautical Society of India
*Reviewer for International conference on Numerical Methods in Fluid Dynamics,
 Asian Congress of Fluid Mechanics conferences
*Member of International Advisory Committee for First International Conference on
 Computational Methods for Thermal Problems, Naples, Italy, September 8-10, 2009.
*Organizing Committee Members for International Conference for Computational Partial
 Differential Equations, IIT Bombay, India, 10-13 December, 2008.

COURSES TAUGHT:
Computational Mechanics, Fluid Mechanics, Aerodynamics, Continuum
Mechanics, Flight Mechanics, Gas Dynamics, Basic Computational Fluid
Dynamics, Advanced Computational Fluid Dynamics, Numerical Methods for
Conservation Laws, Aircraft Stability and Control, Numerical Methods for
Engineers, Matrix Computation.

SPONSORED RESEARCH PROJECTS UNDERTAKEN AS PRINCIPAL INVESTIGATOR:
* Computations of Flows Through . . Compressor Cascades (AR&DB)(1995- 1999)
* Computation of viscous incompressible flows inside calandria of a Pressurized Heavy Water Reactor (PHWR)(1996-2000)
* Upgradation of Associate CFD Center of Excellence(2004-2009)
* Flow Computations on Unstructured Grids with Improved Accuracy: An Investigation (AR&DB) (2006-2008)
* Upgradation of Associate CFD Center of Excellence(Ongoing 2009-2010)
* Steady/Unsteady Low Speed Viscous Flow Computations on Static/Moving Grids (AR&DB) (Ongoing 2009-2011)
* Development of High Resolution Schemes for Flow Computations on Space Vehicle
Configurations using Unstructured Grids (ISRO) (Ongoing 2009-2012)

RESEARCH INTERESTS:
New CFD Algorithms for steady and unsteady compressible and incompressible flow computations
and their applications to practical problems. Fluid-Structure interactions.

RESEARCH CONTRIBUTIONS:

Contribution-1: New Implicit Formulation for Convergence Acceleration of
Euler Solvers. (AIAA Paper No. AIAA-2006-3709, 2006):
Relevence of the work: A novel implicit formulation of Kinetic Flux Vector
Splitting method has been developed for solving Euler equations. In the
present formulation, the split flux Jacobian matrices are derived with the
use of a set of tranformed (entropy) variables, which arise naturally when
the Euler equations are transformed to symmetric hyperbolic form. The
Jacobian matrices derived in this way possess very nice structures with
interesting properties. Numerical test problems in one- and two-dimensions are solved
in order to demonstrate the efficacy of the present method and the results
are compare with another implicit formulation. The present implicit
formulation is found to show superior performance over other implicit methods.

Contribution-2: New Formulation on Higher Order Reconstruction in
Unstructured Grid Computations using Solution Dependent Weighted Least
Squares (SDWLS) (Applied Numerical Mathematics journal 2007, International
Journal of Numerical Methods in Fluids 2007, ICFD07 Conference, UK).
Relevence of the work: The use of unstructured grids for computational
fluid dynamics problems has attracted a lot of attention due to thier
abiltiy to discretize arbitrary complex geometries in a relatively very
short turn-around time compared to that of structured grids. The random
data structure associated with unstructured grid allows adaptive refinement
which further helps in enhancing efficiency and solution accuracy. However,
poor accuracy is the major deficiency that has prevented unstructured grid
computations to completely replace structured grid applications.
In the present work, a novel high resolution, second-order,
oscillation-free, weighted least squares reconstruction technique for
finite volume computations of Euler equations is developed. The present
higher order reconstruction approach does not need explicit application
of limiter functions for non-oscillatory solutions. It is for the first
time, weights are chosen to be dependent on the solution in weighted least
squares reconstruction technique. The present least squares approach,
called solution dependent weighted least squares (SDWLS) technique, is
applied to solve 2D numerical test problems involving Euler equations
and its solutions are compared with that of conventional least squares
scheme with van Albada limiter. The comparisons demonstrate the ability
of the SDWLS formulation to produce more accurate solutions on unstructured
grids.

Contribution-3: New formulations of Energy Relaxation Method for
Hypersonic Flow Computations with Real Gas Effect. (1. AIAA
Journal of Spacecraft and Rockets, v.41, n.4, pp.695-698, 2004; 2. AIAA
Paper AIAA-2006-0583, 2006; 3. International Journal of Numerical
Methods in Fluid, v.54, n.12, pp.1473-1494, 2007):
Relevence of the work: Computations of flows around space vehicle/capsule
during re-entry flight requires real-gas effect to be considered. Such
flows are governed by general pressure law, analysis of which is very
difficult. The direct modelling of the pressure law leads to nonlinear
equations involving large number of derivatives. As a result, numerical
solution of these equations are very expensive. Numerical computations of
the flow is generally carried out with approximation to the pressure law.
An efficient and economic CFD solver has been developed using energy
relaxation approach in which internal energy is split into linear and
non-linear part. The energy relaxation method has been successfully
applied to Harten Lax and van Leer with Contact discontinuity (HLLC) scheme
to solve real gas flows over hypersonic re-entry capsule. This approach is
being extended to non-equilibrium flow with and without viscous effects.

Contribution-4: Development of a state of the art CFD
algorithm for unsteady flow computation on dynamic grids involving
fluid-structure-interaction. (International Journal of
Computational Methods, v.1, n.3, pp.1-12, 2004):
Relevence of the work: One of the main aim in Aeronautics is to design
lighter airplanes. As a result, they are more susceptible to strong
fluid-structure interaction due to increased flexibility of the structure.
Similarly, structures in parachute and baloon being flexible,
fluid-structure interaction are very important. Fluid-structure
interactions also need to be considered whenever moving bodies are
involved; e.g. starp-on motors seperations in rockets, missiles \& fuel
tanks seperation from aircraft, rotor-stator interaction in turbomachinary
etc just to name a few examples.
Computations of unsteady flows involving moving bodies, requiring
dynamic grid, is the most challenging and upcoming area in CFD. Ultimate
knowledge in Fluid & Solid mechanics and CFD are needed in order to
successfully solve such a problem. It requires special formulations of
Fluid Mechanics (e.g. Arbitrary Lagrangian Eulerian formulation) and CFD
(e.g. grid movement & deformation stategies using various analogies;
application of Geometric Conservation Laws to aviod error related to
discretizations, maintaining time accuracy to capture the true unsteady
phenomena etc.) and coupling of fluid and structure solvers in order to
have proper transfer of energy between the two systems. The coupling of
fluid with (flexible) structure solvers is yet to be done.

Contribution-5: Development of a New Multigrid Method for Convergence
Acceleration of the Solution of Hyperbolic Conservation Laws.
(Computational Mechanics, International Journal, v.23,
n.5/6, pp.397-403, 1999):
Relevence of the work: As the field of CFD is getting matured, the
algorithms are becoming more sofisticated to achieve high computational
reliability. Upwind approach of Euler/ N-S equations is one such example.
Most often, the advantages of such algorithms are obtained at the cost of
increased computational work in comparison to ordinary methods. In order
to offset the additional expenses, it is highly desirable to accelerate
convergence so that their applications in solving large practical problems
become feasible. Multigrid method, originally developed for elliptic
partial differential equations, is one of the most effective ways to
accelerate convergence.
A new multigrid method has been developed that yields many times more
convergence acceleration as compared to the existing mutigrid method for
Hyperbolic Problems. This is the only method of its kind that is
specifically developed for hyperbolic problems. Here the hyperbolic (wave)
nature of the system is exploited to devise this multigrid method.
It is a common practice in CFD to convert most of the Fluid Mechanics
problems into Hyperbolic Conservation Laws, as its mathematical properties
are well understood. Thus the present theory is of significant interest to
CFD community.

Contribution-6: Pseudo-Compressibility Approach to solve
Incompressible Flows with Heat Transfer
(1. AIAA Journal of Thermophysics and Heat Transfer, v.14, n.4, pp.606-609,
2000; 2. Computers and Fluids, v.30, pp.607-620,
2001; 3. Proc. ASME Fluid Engineering Division Summer Meetings, May 29 to
June 1, 2001, New Orleans, U.S.A.; 4. First Int. Conf. on Computational
Methods for Thermal Problems, Sept 8-10, 2009, Naples, Italy):
Relevence of the work: Unlike the common practice of using pressure-based
methods for incompressible fow computations in Mechanical engineering,
Pseudo-Compressibility Approach is used for solving Incompressible Flows
with Heat Transfer. In this approach the governing (EE/NS) equations are
converted to a set of hyperbolic conservation laws that is similar to the
compressible flow equations used for modelling Aerospace problems. As a
result the most sophisticated CFD algorithms used by Aerospace community
are possible to be easily extended to solve incompressible flows. They are
found to give better convergence and accuracy. Having established the
pseudo-compressibility method for solving a wide variety of incompressible
flow test problems with heat transfer, it has been finally used to developed a
general purpose 3-D incompressible Navier Stokes code for simulating
moderator flows inside calandria of a Pressurized Heavy Water Reactor(PHWR).

Contribution-7: Development of a new class of Methods
based on Kinetic Theory of Gases.
(Computers and Fluids, v.23, n.2, pp.447-478, 1994):
Relevence of the work: In the development of this method a very different
(molecular particle) approach is used to take into account of the wave
nature of the Euler equations (known as Kinetic Flux Vector Splitting,
KFVS). As a result, it has many attractive properties that is usually not
present in other methods. For example, the entropy condition is
automatically taken care of as a consequence of Boltzmann H-Theorem;
simple molecular dynamics like specular reflection priciple helps in
implimenting the same method right at the boundary (which is not possible
for any other solver). This boundary condition is popularly known as
Kinetic Characteristic Boundary Condition (KCBC). This is the only
approach that can be easily combined with Direct Simulation Monte Carlo
(DSMC) solution of Boltzmann equation using Domain Decomposition approach,
as the interface boundary conditions for each set of governing equations are
easily specified.

RECENT INVITED/ PLENARY TALKS IN CONFERENCES/ WORKSHOPS:
*"Development of Riemann Solvers for Hyperbolic Conservation Laws", Indo-German
 Workshop-cum-Lecture Series on "Computaional Models and Methods Driven by Industrial Problems
 (CMMDIP0809)", January 5-16, 2009, Department of Mathematics, IIT Madras, Chennai.
*"Numerical Computations of Hyperbolic Partial Differential Equations: Issues and Challenges",
 Plenary Talk at National Symposium on Recent Advances in Computational Techniques (RACT09),
 January 9-10, 2009, Department of Mathematics, Stella Maris College, Chennai.
*"Development of High Resolution Schemes for Hyperbolic PDEs" at the International Conference
 on Computational Partial Differential Equations, 10-13 December 2008, Mathematics Department, IIT Bombay.
*"Fundamentals of Upwind Methods for Hyperbolic Conservation Laws" at the Instructional School on
 PDEs and National Symposium on Hyperbolic PDEs, 14-17 July 2008, Mathematics Department, IIT Bombay.
*"A Novel Approach for High Resolution Finite Volume Method", Asian Computational
 Fluid Dynamics Conference, 26-30 November 2007, Bangalore, India.
*"Challenges in Developing Higher Order Accurate Schemes for Simulation of Flows with Discontinuities:
 Issues and Alternatives", Second International Conference on Computational Mechanics and
 Simulation (ICCMS), IIT Guwahati, India, 8-10 December 2006.
*“Overview of Computations of Incompressible and Low Speed Flows”, 16th February 2006,
 Aerodynamics R&D Division, Vikram Sarabhai Space Centre, Thiruvananthapuram, Kerala.

SELECTED PUBLICATIONS :
*"Incompressible flow computations over moving boundary using a novel upwind method",
  (with Sonawane, C R, Iyer, A and GosaviInamdar J A), Institute for Computational
 Fluid Dynamics (ICFD) Conference on Numerical Methods for Fluid Dynamics,
 12-25 April 2010, University of Reading, UK.
*"CFD analysis of single-phase flows inside helically coiled tubes", (with
 Jayakumar, J. S., Mahajani, S. M., Kannan N Iyer and Vijayan, P. K.), Computers
 and Chemical Engineering, (in press).
*"An Upwind Method for Incompressible Flows With Heat Transfer", (with Iyer, A)
 First International Conference on Computational Methods for Thermal Problems"
 (ThermaComp09), September 8-10, 2009, Naples, Italy.
*"Thermal Hydraulic Characteristics of Air-Water Two-phase flows in Helical
 Pipes", (with Jayakumar, J. S., Mahajani, S. M., Kannan N Iyer and Vijayan, P. K.),
 Chemical Engineering Research and Design, (in press).
*"An upwind method for incompressible flow computations using pseudo-compressibility
 approach" (with Anesh Iyer),AIAA Paper AIAA-2009-3541, 19th AIAA Computational
 Fluid Dynamics Conference, San Antonio, Texas, USA, 22–25 June 2009.
*"Numerical analysis of heat transfer to air-water two-phase flows in
 helical pipes" (with Jayakumar J S, Mahajani S M, Vijayan P K), ICHMT Symposium:
 CHT-08 Advances in Computational Heat Transfer Marrakech, Morocco 11-16 May 2008.
*"On the Link Between Weighted Least-Squares and Limiters Used in
 Higher-Order Reconstructions for Finite Volume Computations of
 Hyperbolic Equations", (with Subramanian J), Applied Numerical
 Mathematics, 58 (5), pp. 705-725, 2008 .
*"High Resolution Finite Volume Computations Using A Novel Weighted
 Least-Squares Formulation" (with S Rao and J Subramanian) International
 Journal of Numerical Methods in Fluids, Vol.56, n.8, pp.1425-1431, 2008.
*"Experimental and CFD Estimation of Heat Transfer in Helically Coiled Heat
  Exchangers", (with Jayakumar J S, Mahajani S M, Vijayan P K, Bhoi R), IChemE's
  journal, Chemical Engineering Research and Design, vol.86, pp.221-232, 2008.
*"Three Dimensinal Finite Volume Computation Using A Novel Reconstruction
 Formulation", (with S Rao), Asian Computational Fluid Dynamics
 Conference, 26-30 November 2007, Bangalore, India.
*"High Resolution Finite Volume Computations using A Novel Weighted Least-
 Squares Formulation", (with Subramanian J, Rao, S), ICFD07, 26-29
 March 2007, University of Reading, UK.
*"Energy Relaxation Method for Chemical Non-equilibrium Flow Computations"
 (with Patil M, Swaminathan S), International Journal of Numerical
 Methods in Fluids, Vol.54, n.12, pp.1473-1494, 2007.
*"A New Implicit Formulation of KFVS Scheme for Euler Equations"
 (with Jain K), AIAA Paper No. AIAA-2006-3709, 2006.
*"Hypersonic Viscous Flow Computations Using Energy Relaxation Method"
 (with Patil M, Swaminathan S), AIAA Paper No. AIAA-2006-0583, 2006.
*"Unsteady Flow Computations over Moving Body using Dynamic Meshes",
 (with Ballmann J), International Journal of Computational Methods,
 Vol.1, No.3, pp.507-518, 2004.
*"Three Dimensional Hypersonic Flow Computation Over Reentry Capsule
 Using Energy Relaxation Method", (with Patil M, Swaminathan S),
 Volume 41, Number 4, pp.695-698, Journal of Spacecraft and
 Rockets 2004.
*"Three dimensional hypersonic real gas flow analysis over a reentry
 capsule using energy relaxation method", (with Patil M,
 Swaminathan S), Proc. 10th Asian Congress of Fluid Mechanics, 17-21
 May 2004, Peradeniya, Sri Lanka.
*"Computations of Flows Inside Calandria of Pressurized Heavy Water
  Reactor", (with Agrawal L, Marathe A G), Paper No.FEDSM2001-18061,
 Proc. ASME Fluid Engineering Division Summer Meetings, May 29- June 1,
 2001, New Orleans, USA.
*"Computations of Laminar and Turbulent Mixed Convection in A Driven
 cavity Using Pseudo Compressibility Approach", (with Agrawal L,
 Marathe A G), Computers & Fluids, v.30(5), pp.607-620, 2001.
*"Computations of Incompressible Flows with Natural Convection
  Using Pseudo-Compressibility Approach", (with Agrawal L,
 Marathe A G), AIAA Journal of Thermophysics and Heat Transfer, vol.14,
 No.4, pp.606-609, Oct-Dec 2000.
*"An Improved Multigrid Method for Euler Equations", (with Rajput H)
 Computational Mechanics, vol.23, no.5/6, pp.397-403, 1999.