Qualification: 
Ph.D
r_balajee@cb.amrita.edu

Dr. Balajee Ramakrishnananda got his Doctoral Degree from Nanyang Technological University, Singapore, in 1997. His doctoral thesis work centered around the computational study of flow through a centrifugal vaned diffuser used in transonic flow regimes.

He obtained his Masters degree from IISc, Bangalore and B. Tech. from IIT, Madras. Prior to joining Amrita, he was working as a Software Engineering Manager at AMD, Hyderabad in the area of GPGPU Computing.

Dr. Balajee had also worked as a Scientist-B at National Aerospace Laboratories, Bangalore in the area of Transonic Wind Tunnel Testing. He has worked for several years in the Military & Flight Simulation fields in product development and managerial roles. He had also worked on physics based animation where he placed aerodynamics and flight mechanics of birds in a perspective suited for computer animation. 

Areas of Research

  • Micro Aerial Vehicles
  • Wind Turbines
  • Applied Computational Fluid Dynamics
  • Hypersonic Flow
  • Propulsion
  • Compressible Fluid Flow
     

Research Activities

  • Co-guide for PhD student
     

Funded Projects

  • Coking in Semi-cryogenic Engines: Studies on Predicting the Onset of Coking in a Heated Tube      with Isrosene / Kerosene, ISRO funded project (Co-PI)
  • Effusion Cooling for Gas Turbine Combustors: Studies on Enhancement of Cooling Effectiveness by Design Improvisation, GTRE funded project (Co-PI)
     

Publications

Publication Type: Conference Proceedings

Year of Publication Title

2019

Divyendu Kishore Valappil, Zakir, F., Ravindran, J., Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “Reynolds Number Effects on Wings Inspired by Flying Snakes”, International Conference on Applied Mechanics and Optimisation (Presented as Poster Presentation). MBCET, Thiruvananthapuram, 2019.

2019

N. Bharath Ra T., G. Kumar, N., Suresh, J., Dr. Balajee Ramakrishnananda, Rajesh Senthil Kumar T., Srinivas, N., and Sowmya, R., “Effects of cross-sectional shapes on the aerodynamic characteristics of bio-inspired airfoils”, International Conference on Applied Mechanics and Optimisation Published as AIP Conference Proceedings, vol. 2134. MBCET, Thiruvananthapuram, 2019.[Abstract]


The gliding abilities of Chrysopelea paradisi is considered the best among flying snakes. During flight, Chrysopelea paradisi assume a cross-section that is favorable for gliding. Unconventional Micro-Air-Vehicle research may benefit from a study of related cross-sections at these low Reynolds numbers (3000-15000). A total of thirty-one cross- sections created by modifying the biological cross section taken at the mid body of Chrysopelea paradisi during glide are evaluated for their aerodynamic characteristics for Reynolds number 3000 and 15000 at angles of attack ranging from −10+ to 60+ in steps of 5+. These observations would hopefully spur further research and interest in airfoils suitable for unconventional Micro Aerial Vehicles.

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2019

S. P., R, K. Ramana, Saroj Harikrishn Gopi, Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “Turn Control in Wings Inspired by Flying Snakes”, International Conference on Applied Mechanics and Optimisation Published as AIP Conference Proceedings, vol. 2134. American Institute of Physics Inc., MBCET, Thiruvananthapuram, 2019.[Abstract]


Flying snakes exhibit efficient gliding performance even though they lack any sophisticated flight morphologies like wings. In an earlier work, a gliding algorithm for non-equilibrium glides of such snakes was modeled. In the current work, this is extended to initiate and control turns. The curvature of the centerline of the snake-like body is varied using an n-chain model of the snake and p-d controllers during flight. Trajectory control through way point guidance is shown to be possible in a limited sense. Two aerodynamic models are compared for their ability to induce steeper turns.

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2019

Rajesh Senthil Kumar T., Shriram, S. V., G. Pranay chowdary, Sagar, J. T. S. V., and Dr. Balajee Ramakrishnananda, “Aerodynamic Characteristics of Avian Airfoils”, International Conference on Applied Mechanics and Optimisation Published as AIP Conference Proceedings, vol. 2134, 1 vol. American Institute of Physics Inc., MBCET, Thiruvananthapuram, 2019.[Abstract]


This paper is focused on four bird's airfoils namely Seagull, Merganser, Teal and Owl which are extracted from their respective wing cross-sections. In addition to this, the corrugation due to feather roughness of Swift bird is imposed on Seagull. The aerodynamic performance of these 4 avian airfoils and corrugated Seagull airfoil is tested in Reynolds number in the range of 104-105. Seagull and owl indicates better aerodynamic performance in 4 airfoils and analysed how the flow behaviour by tracking the laminar separation bubble. Seagull Corrugated illustrates better performance than seagull in small Reynolds number.

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2019

Saran Kumar Komari, Annapoorna Sreekumar, Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “A Genetic Algorithm Approach to Design Aerofoils for Small Wind Turbines”, International Conference on Applied Mechanics and Optimisation Published as AIP Conference Proceedings, vol. 2134. American Institute of Physics Inc., MBCET, Thiruvananthapuram, 2019.[Abstract]


A genetic algorithm (GA) methodology to design better site specific or wind profile specific aerofoils for small wind turbines starting from an initial pool of aerofoils is described. The GA methodology generates new aerofoils and quickly evaluates the fitness function of every aerofoil using XFOIL software. While XFOIL has a quick turnaround time, Computational Fluid Dynamics (CFD) methods are more expensive but have less assumptions. Hence, the suggested GA methodology can be used to quickly produce reasonably good test candidates for shortlisting the aerofoils for computational study. The best four aerofoils before GA and the best four after GA are taken and the top four performers from this pool are identified using CFD results. The results of the CFD study show that while three of the aerofoils after GA have better fitness values than the original pool, one from the original pool is still a comparatively good performer.

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2018

R. Senthil Kumar.T, Nikitha Narayanaprasad, Yashmitha Kumaran, .V, S., and Dr. Balajee Ramakrishnananda, “Numerical Analysis of Discrete Element Camber Morphing Airfoil in the Reynolds number of Conventional Flyers”, 3rd International Conference on Innovative Design, Analysis and Development Practices in Aerospace and Automotive Engineering. Vel Tech Rangarajan Dr Sagunthala R&D Institute of Science and Technology, Chennai, 2018.

2018

Annapoorna Sreekumar and Dr. Balajee Ramakrishnananda, “Objective Function Formulation for Small Wind Turbine Aerofoil Design”, 3rd IEEE Biennial international conference on Power & Energy Systems: Towards sustainable energy - 2018 (PESTSE - 2018) *Recipient of "Prof. Muhammad Harunur Rashid” best paper award along with a cash prize of Rs. 5000. 2018.

2017

Saroj Harikrishn Gopi, Divyendu Kishore Valappil, Dr. Balajee Ramakrishnananda, Rajesh Senthil Kumar T., and Viswesh Sujjur Balaramraja, “Modeling Non-Equilibrium Glides in Flying Snakes”, 2017 International Conference on Advances in Computing, Communications and Informatics (ICACCI). Manipal, 2017.[Abstract]


Flying snakes of the species Chrysopelea paradisi glide without the use of limbs. These gliders use the speed of free fall and the change in their body shape to generate lift. Despite their lack of appendages, their ability to glide has piqued the interest of many. Hence, modeling the flight of these snakes has received considerable attention in the recent past. Experimental studies have been done in the past on live flying snakes to understand their unusual glide mechanism. Equilibrium glide-in which the speed of the center of gravity of the snake is more or less constant - is relatively easier to model than nonequilibrium glide where this speed changes with time. Flying snakes spend most of their flight in non-equilibrium glide than on equilibrium glide. An earlier model for generating the undulating shape generated realistic shapes at a specified time. However, many parameters needed to be fine-tuned along with unforeseen singularities. Further, it generated the centerline shape of the snake in a plane, but could not consider out of plane undulation of the snake. In the current work, a better model for the undulating motion of the snake is proposed which is extended to include out of plane motion of the snake's centerline. The aerodynamic forces acting on the snake at an instant of time are computed using thin airfoil theory and blade element theory. With the help of these, the velocities and trajectory of the snake's flight path are computed and compared with data available in literature. This model has potential for application in biological and biomechanical study of the flight of flying snakes, study of unconventional Micro-aerial vehicle and physics based computer animation

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2017

Prasanth Kowsik K, Thamizharasan K, Anjana L, Gokul Krishnan R, Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “Computational Study of Effects of Icing on Wind Turbine Airfoil Performance”, 44th National Conference on Fluid Mechanics and Fluid Power (FMFP-201). Amritapuri, Kollam, India, 2017.

2016

Viswesh Sujjur Balaramraja, S. Sankrityayan, E., Sivagurunathan, S. Coimbatore, Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “Modelling the Undulation Patterns of Flying Snakes”, International Conference on Advances in Computing. Communications and Informatics (ICACCI-2016), Jaipur, India, 2016.[Abstract]


Some species of snakes are good gliders and can travel as far as 330 feet from a height of 15m through air at speeds of around 9-12m/s. They possess a unique and complex aerial locomotion compared to other species of gliders. During glide, the snake morphs its transverse body section into an airfoil-like shape. In addition, it undulates its body in a characteristic fashion. Understanding the change in shape of flying snake due to this undulation is vital for gliding and maneuvering during glide. Previous studies have explained the effects of 2-D shape. Earlier computational studies on a fixed 3-D wing inspired by the snakes have revealed favorable aerodynamic characteristics. In the current work undulation patterns of a representative snake geometry is modelled mathematically and numerically. The generated shape exhibits lot of similarity to experimentally observed ones. By adding the cross-section of the snake to this shape, the 3-D snake geometry at different instances of time during undulation can be generated. Three dimensional CFD study using ANSYS is performed on these shapes assuming quasi-steady flow. The computed average glide angle agrees well with experimental data. This shows promise for the undulatory model proposed. The current work throws a better understanding of the undulatory motion and may lead to advances in the development of unconventional Micro-Air Vehicles and Snake-Bots apart from biomimetics. More »»

2015

Dr. Balajee Ramakrishnananda, Purushothaman, P. Pulikkul, Shankar, R. Ravi, ,, and G. S.K., M. Siddhardha, “Design of a New Aerofoil for Low Starting Wind Speeds for a Small VAWT”, 1st International Conference on Advanced Engineering and Technology for Sustainable development (ICAETSD - 2015), vol. 5. Karpagam College of Engineering, Coimbatore, 2015.

2015

Dr. Balajee Ramakrishnananda, Vigneshwaran Krishnamurthy, Nithyalakshmi Venkatraman, Nandita Nurani Hari, Akshay Varaparla, and Rajesh Senthil Kumar T., “Computational Study of the Aerodynamics of the Gliding Snake Chrysopelea Paradisi”, 1st International Conference on Advanced Engineering and Technology for Sustainable development (ICAETSD - 2015), vol. 5. Karpagam College of Engineering, Coimbatore, 2015.

2015

Vertika Saxena, Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “Simulation of Flow Past a Wing Inspired by Flying Snakes”, Fourth International Conference on Advances in Computing, Communications and Informatics (ICACCI-2015). Institute of Electrical and Electronics Engineers Inc., Kochi, pp. 720-725, 2015.[Abstract]


Wings of airplanes, ornithopters and micro-aerial vehicles were inspired by the wings of birds and insects. A flying snake found in South and South-East Asia converts its entire body into a morphing wing which AIDS it to glide very efficiently. The aerodynamics of this species of snake is not well understood. Two dimensional computational and experimental studies of the snake's rather unusual cross-section have been done in earlier works. A three dimensional simulation of the flow over a wing inspired by the snake's body geometry is solved in the current work using steady laminar assumptions. Solutions were obtained from an angle of attack of 0 to 55 degrees in steps of 5 degrees. Interesting features like wake interaction with downstream sections and complex vortex shapes come to light. At low angles of attack, transverse flows reduce the strength of the wake leaving the wing. Gentle stall characteristics with a high stall angle and almost linear increase in drag with angle of attack are noticed. Bending of streamlines indicative of high lift production are clearly visualized at the maximum lift condition. © 2015 IEEE.

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1999

Dr. Balajee Ramakrishnananda and Wong, K. C., “Animating Bird Flight Using Aerodynamics”, Technical Sketch, SIGGRAPH 99 Conference Abstracts and Application and ACM SIGGRAPH, Computer Graphics Annual Conference. Los Angeles, California, p. 230, 1999.

Publication Type: Journal Article

Year of Publication Title

2019

R. Senthil Kumar.T, .Sivakumar, V., Dr. Balajee Ramakrishnananda, and Soorya.S, V., “Aerodynamic Performance Estimation of Camber Morphing airfoils for Small Unmanned Aerial Vehicle”, Journal of Aerospace Technology and Management (Accepted), 2019.

2019

Rajesh Senthil Kumar T., Nikitha Narayanaprasad, Yashmitha Kumaran, Sivakumar, V., and Dr. Balajee Ramakrishnananda, “Numerical Analysis of Discrete Element Camber Morphing Airfoil in the Reynolds Number of Conventional Flyers”, In: Chandrasekhar U., Yang LJ., Gowthaman S. (eds) Innovative Design, Analysis and Development Practices in Aerospace and Automotive Engineering (I-DAD 2018), Lecture Notes in Mechanical Engineering, pp. 187-193, 2019.[Abstract]


This paper investigates the aerodynamic performances of an airfoil morphed into another airfoil configuration at a Reynolds number of 3 × 106 using discrete element method. Morphing airfoil configurations were achieved by adjusting three locations along with the chord of NACA 0012. Out of the three, two were chosen at the maximum camber and maximum thickness positions corresponding to that of the target airfoil (NACA 23012). The third position was fixed at 80% of the chord. Six morphed airfoil configurations were generated, and their performances were numerically computed between 0° and 16° angle of attack using ANSYS Fluent v15.0. Spalart–Allmaras and transitional shear stress transport models were used to evaluate the aerodynamic performance of the morphed airfoil configurations. Over this range of angles of attack, morphed configurations were ordered according to three factors—high lift, low drag and high cl/cd. The airfoil can morph from one to another during different phases of flight to give an overall optimum aerodynamic performance. Additionally, the effect of smoothening the sharp corners at the morphing locations is also investigated.

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2018

V. Venkatesh, Sriraam J., Bala Vignesh D., K., S., Velamati, R. Kishore, Dr. Srikrishnan A. R., Dr. Balajee Ramakrishnananda, and Suresh Batchu, “Studies on Effusion Cooling: Impact of Geometric Parameters on Cooling Effectiveness and Coolant Consumption”, Aerospace Science and Technology, vol. 77, pp. 58 - 66, 2018.[Abstract]


This study is focused on the impact of certain important geometric parameters on cooling effectiveness and coolant consumption for effusion cooling of aircraft combustor liner. The three dimensional turbulent flow field in a domain representing the combustor with several rows of effusion coolant injection is considered for the analysis. The geometric parameters considered are: angle of injection of the coolant, axial and transverse pitch of the injection holes, hole spacing and hole diameter. Also, based on the analysis of the temperature field within the chamber, a novel concept of ‘variable hole diameter’ has been introduced to reduce coolant consumption. A symmetric 3D computational model including the combustion chamber, coolant chamber and the effusion plate was used for the study. Conjugate heat transfer was modeled between the effusion-cooled wall and the two chambers. A detailed mass flow rate analysis has been performed for the various cases in order to study the impact of parameters on coolant consumption. The proposed approach of using an effusion plate with variable hole diameters is found to be effective in reducing the net coolant consumption significantly while maintaining a given level of cooling effectiveness.

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2017

Rajesh Senthil Kumar T., Dr. Sivakumar V., Dr. Balajee Ramakrishnananda, Arjhun, A. K., and , “Numerical Investigation of Two Element Camber Morphing Airfoil in Low Reynolds Number Flows”, Journal of Engineering Science and Technology, vol. 12, pp. 1939-1955, 2017.[Abstract]


Aerodynamic performance of a two-element camber morphing airfoil was investigated at low Reynolds number using the transient SST model in ANSYS FLUENT 14.0 and eN method in XFLR5. The two-element camber morphing concept was employed to morph the baseline airfoil into another airfoil by altering the orientation of mean-line at 35% of the chord to achieve better aerodynamic efficiency. NACA 0012 was selected as baseline airfoil. NACA 23012 was chosen as the test case as it has the camber-line similar to that of the morphed airfoil and as it has the same thickness as that of the baseline airfoil. The simulations were carried out at chord based Reynolds numbers of 2.5×105 and 3.9×105. The aerodynamic force coefficients, aerodynamic efficiency and the location of the transition point of laminar separation bubble over these airfoils were studied for various angles of attack. It was found that the aerodynamic efficiency of the morphed airfoil was 12% higher than that of the target airfoil at 4° angle of attack for Reynolds number of 3.9×105 and 54% rise in aerodynamic performance was noted as Reynolds number was varied from 2.5×105 to 3.9×105. The morphed airfoil exhibited the nature of low Reynolds number airfoil. © School of Engineering, Taylor’s University.

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2015

P. Pulikkul Purushothaman, Shankar, R. Ravi, Hariharan, S. K., G. Siddhardha, M., and Dr. Balajee Ramakrishnananda, “Design of a New Aerofoil for Low Starting Wind Speeds for a Small VAWT”, International Journal of Applied Engineering Research, vol. 10, no. 19, pp. 14480-14484, 2015.

2015

Vigneshwaran Krishnamurthy, Nithyalakshmi Venkatraman, Nandita Nurani Hari, Akshay Varaparla, Dr. Balajee Ramakrishnananda, and Rajesh Senthil Kumar T., “Computational Study of the Aerodynamics of the Gliding Snake Chrysopelea Paradisi”, International Journal of Applied Engineering Research, vol. 10, no. 9, pp. 14476-14479, 2015.[Abstract]


Flying snakes exhibit an exceptional gliding mechanism without any added appendages that can aid gliding. Several studies on the mechanism have shown that the snake performs a ballistic dive from a height and glides through the air at high angles of attack of 35 degrees and above. Research has shown the morphing of their body structure from a cylindrical to a flattened shape with a rounder dorsal surface makes it possible for these creatures to not only perform glide but also various turning maneuvers. In this study, the variations of the lift, drag and normal force coefficients (CL, CD and CN) with glide angle are predicted by solving the three dimensional, steady, viscous, incompressible flow over the snake during its glide using CFD study. The three dimensional CFD analysis shows that the lift and normal force coefficients keep increasing increases with the glide angle even up to a high glide angle of 35 degrees which helps the snake to counteract the gravitational force. Further, the aerodynamic efficiency of the snake is still less than its maximum value at this glide angle, which is not predicted by twodimensional analysis. This study can aid in applications for security and defense.

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1999

Dr. Balajee Ramakrishnananda and Wong, K. C., “Animating Bird Flight Using Aerodynamics”, Visual Computer, vol. 15, pp. 494-508, 1999.

1995

Dr. Balajee Ramakrishnananda and Murali Damodaran, “Numerical Study of Viscous Compressible Flow Inside Planar and Axisymmetric Nozzles”, Lecture Notes in Physics, vol. 453, pp. 508-512, 1995.

Publication Type: Conference Paper

Year of Publication Title

2014

Madhushree M., Raghunadh Malla Venkata, Mohammed Abdul Junaid, Rajasekaran Akash, and Dr. Balajee Ramakrishnananda, “Theoretical Optimization of Airfoils for Different Wind Turbine Conditions”, in International Conference on Contemporary Challenges in Management, Technology and Social Sciences(Also published as Handbook of Management, Technology and Social Sciences edited by S. Pandey and Jain Singh organized by SEMS and MGIMT, MGIMT, Lucknow, India, 2014.

2013

Dr. Balajee Ramakrishnananda, Rakesh Krishnan, R.R. RevathyPriya, Akshay Basavara, and Sivaranjani Ganapathy Santhanam, “Aerofoils for Small Vertical Axis Wind Turbines”, in National Conference on Wind Tunnel Testing (NCWT-03) [CD-ROM], Vikram Sarabhai Space Centre, Thiruvananthapuram, Kerala, India, 2013.

1998

Dr. Balajee Ramakrishnananda, Wong, K. C., Lim, S. K., Goh, L. L., and Low, B. H., “Litter Bug”, in SIBGRAPI '98 Video Festival, 1998 International Symposium of Computer Graphics, Image Processing and Vision, Rio de Janeiro, Brazil, Rio de Janeiro, Brazil, 1998.

1994

Dr. Balajee Ramakrishnananda and Damodaran, M., “Computational study of aerodynamic flows inside nozzles”, in International Pacific Air & Space Technology Conference, Singapore, 1994.[Abstract]


Compressible aerodynamic flows inside nozzles are computed by a finite volume method to numerically integrate the Euler and Navier-Stokes equations. The solution procedure is based on an explicit multi-stage time-stepping scheme wherein the spatial terms are central-differenced and a combination of second and fourth differences in the flow variables are used to construct numerical dissipation terms to enhance numerical stability. Convergence to steady state is accelerated dramatically by using local time-stepping, implicit residual smoothing and a multi-grid strategy. Computed results are presented for a wide variety of flow regimes comprising of subsonic, transonic, choked and supersonic flows for a nozzle.

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1994

Dr. Balajee Ramakrishnananda and Damodaran M., “Numerical Study of Viscous Turbulent Flow Through Planar and Axisymmetric Nozzles”, in 14th International Conference on Numerical Methods in Fluid Dynamics, Bangalore, India, 1994.