Sriram Rallabhandi
Resident at: NASA Langley Research Center
Mail Stop 442, Hampton, VA 23681
Tel: (757) 864-9554; Fax: (757) 864-6306
Email: Sriram.rallabhandi@nianet.org
Research Interests
· Aircraft Design
· Sonic Boom Modeling
· Multi-Disciplinary Design Optimization
· Aerodynamic Analysis
· Computational Fluid Dynamics
· Reduced Order Modeling and Model Order Reduction
Current Research
· Development of theoretical and practical foundation for generating appropriate targets for sonic boom minimization
Previous sonic boom target generation process has relied on linearized physics and corresponding area distributions that are rigid from an aircraft design point of view. Research has been conducted to make the target distributions more amenable to aircraft design purposes by making them flexible. Using generalized extensions to classical theory, non-classical sonic boom targets were generated to produce the desired front and aft shaped ground signatures. Further research is being carried out in this area to aid the aircraft designer in achieving these targets. Collaborators: Wu Li (NASA Langley)
· Development of methods for sonic boom off-track analysis and design
Impact of sonic boom and its reduction remains the most important challenge in supersonic aircraft design studies. Many researchers are actively looking into sonic boom minimization under the flight path of the aircraft, where the impact is expected to be the highest; however the impact at off-track locations may also be significant and at times more than the under-track impact because of aircraft maneuvers or the prevailing atmospheric conditions. In addition, the frequency content at off-track locations may be very different than the under-track signature forcing the consideration of these locations in the aircraft design process. This research aims to analyze, quantify and optimize the design by including the off-track impact along with the under-track results. Collaborators: Irian Ordaz (NASA Langley), Wu Li (NASA Langley)
· Consideration of advanced propagation effects
Sonic boom propagation from the aircraft altitude to the ground has traditionally been carried out using linearized physics with cumulative non-linear corrections. However, this fails to capture the other effects, such as thermo-viscous absorption and molecular relaxation during propagation. In the absence of these effects, the predicted ground signature lacks vital information such as shock rise times, resulting in incorrect frequency content. This research aims to use advanced schemes in the propagation process to predict the sonic boom ground signatures.
· Development of theoretical, analytical and practical methods for the design of supersonic aircraft
To facilitate high-fidelity design optimization, mesh deformation tools were integrated into the supersonic aircraft design process for efficient CFD shape optimization. Other design tools have been developed to extrapolate near-field CFD cylinders to their mid-field counterparts for sonic boom propagation. Collaborators: Wu Li (NASA Langley), Bill Shields (NASA Langley), Karl Geiselhart (NASA Langley) and Irian Ordaz (NASA Langley).
Publications
· Rallabhandi, S.K., Li, W., Geiselhart, K., “Boom Constrained Drag Minimization for Design of Supersonic Concepts”, Presented at the 48th AIAA Aerospace Sciences Meeting and Exhibit, Orlando FL, Jan, 2010
· Ordaz, I., Rallabhandi, S.K., “Low Boom -Low Drag Global Shape Optimization Using CART3D”, Presented at the 48th AIAA Aerospace Sciences Meeting and Exhibit, Orlando FL, Jan 2010
· Plotkin, K.J., Rallabhandi, S.K., Li, W., “Generalized Formulation and Extension of Sonic Boom Minimization Theory for Front and Aft Shaping”, Presented at the 47th AIAA Aerospace Sciences Meeting and Exhibit, Orlando FL, Jan 2009
· Lee, K., Rallabhandi, S.K., Mavris, D.N., “Aerodynamic Model Reduction via Probabilistic Principal Component Analysis”, Presented at the 46th AIAA Aerospace Sciences Meeting and Exhibit, Reno NV, Jan 2008
· Rallabhandi, S.K., Mavris, D.N., “Simultaneous Airframe and Propulsion Cycle Optimization for Supersonic Aircraft Design”, Journal of Aircraft, Vol. 45, No. 1, pp: 38-55. Also presented at the 46th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan 2008
· Rallabhandi, S.K., Mavris, D.N., “New Computational Procedure for Incorporating CFD into Sonic Boom Prediction”, Journal of Aircraft, Vol. 44, No.6, 2007, pp: 1964-1971. Also presented at the 24th AIAA Applied Aerodynamics Conference, San Francisco, California, June 5-8, 2006
· Rallabhandi, S.K., Mavris, D.N., “Aircraft Geometry Design and Optimization for Sonic Boom Reduction”, Journal of Aircraft, Vol. 44, No.1, 2007, pp: 35-47
· Rallabhandi, S.K., Mavris, D.N., “Sonic Boom Minimization Using Inverse Design and Probabilistic Acoustic Propagation”, Journal of Aircraft, Vol. 43, No.6, 2006, pp:1815-1829
· Utturwar, A., Rallabhandi, S., Delaurentis, D., Mavris, D., “A two-step Optimization Approach for Technology Selection”, Engineering Optimization, Vol. 38, No. 8, December 2006, pp:889:908
· Rallabhandi, S.K., Mavris, D.N., “Sonic Boom Minimization Using Improved Linearized Tools and Probabilistic Propagation”, AIAA-2005-1019 Proceedings of the 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, Jan. 10-13, 2005