Qualification: 
Ph.D, M.Tech, B-Tech
ajithkumars@am.amrita.edu

Dr. Ajith Kumar S. currently serves as Assistant Professor (Sl. Gr.) in the Department of Mechanical Engineering, School of Engineering, Amrita Vishwa Vidyapeetham, Amritapuri Campus. He obtained his Ph.D. from the Department of Aerospace Engineering, Indian Institute of Technology Chennai. He has two Postdoc fellowships from Nanyang Technological University (NTU), Singapore and Indian Institute of Technology Chennai. He is presently involved in guiding three doctoral students and has guided more than ten M.Tech and fourteen B.Tech. projects.

Dr. Ajith’s research interests spread in vast areas; aerodynamics, Computational Fluid Dynamics (CFD), turbulence, data-driven methods in fluid dynamics, bluff body flows at low Reynolds numbers, magneto-hydrodynamics, non-Newtonian fluid dynamics, thermal convection problems, etc. are few to name.

Publications

Publication Type: Conference Proceedings

Year of Publication Title

2019

M. Sivan and Dr. Ajith Kumar S., “Numerical study on flow over two inline triangular cylinders Influence of gap ratio on vortex shedding (Accepted)”, International Conference on Thermofluids – 2020 , Kalinga Institute of Industrial technology. 2019.

2019

A. S. Nair, K., A., R., A., and Dr. Ajith Kumar S., “Aerodynamic characteristics of a square cylinder: Effect of dissimilar leading edges (Accepted)”, KIIT THERMO-2020, an International Conference on Thermofluids-2020 , Kalinga Institute of Industrial technology. 2019.

2019

H. V. and Dr. Ajith Kumar S., “Numerical analysis on influence of propeller geometry in cavitation”, International Mechanical Engineering Congress (IMEC 2019) , National Institute of Technology Trichy (2019). 2019.

2019

A. Vijay, ,, Raj, S., and Dr. Ajith Kumar S., “Numerical Simulation on Flow through a Double Forward Facing Step”, International Conference on Applied Mechanics and Optimisation (ICAMeO 2019) , Mar Baselios College of Engineering And Technology Thiruvananthapuram (2019). 2019.

2019

Sourav N. Kumar, H., A. Vishnu, and Dr. Ajith Kumar S., “Numerical studies to improve the aerodynamic efficiency of an airfoil using delta-shaped surface protrusions”, International Conference on Applied Mechanics and Optimisation (ICAMeO 2019) , Mar Baselios College of Engineering And Technology Thiruvananthapuram . 2019.

2019

Akhil, Mohan, B., and Dr. Ajith Kumar S., “Study of Non – premixed combustion of Propane and Methane using CFD”, International Conference on Advances in Materials and Manufacturing Applications (IConAMMA 2019) , Amrita Vishwa Vidyapeetham, Bangalore. 2019.

2019

Sujith Stephen, Sidharth, and Dr. Ajith Kumar S., “Numerical Studies on Flow Past Top Surface Cooled Circular Cylinder at Low Reynolds Number”, International Conference on Advances in Materials and Manufacturing Applications (IConAMMA 2019) , Amrita Vishwa Vidyapeetham, Bangalore . 2019.

2019

R. Prasad Govindu and Dr. Ajith Kumar S., “Numerical Study on Mixed Convective Laminar Flow over Backward Facing Inclined Step”, 12st International Conference on Thermal Engineering: Theory and Applications (ICTEA 2019), (2018). 2019.[Abstract]


The incompressible laminar flow over backward facing inclined step with downstream wall heating is analyzed numerically. The 2D governing equations with Boussinesq assumption are solved using OpenFOAM. The effects of downstream wall heating and step inclination on the heat transfer behavior and reattachment length are investigated for mixed convection flow.

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2019

A. Vijay and Dr. Ajith Kumar S., “Numerical Simulation On Flow Over Circular Cylinder with Heated Splitter Plate”, 12st International Conference on Thermal Engineering: Theory and Applications (ICTEA 2019) . 2019.

2018

Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Effects of Prandtl number on three dimensional “mushroom structures” in the wake behind a heated cylinder”, 7th International & 44th National Conference on fluid flow and fluid power(FMFP-2018) , IIT Bombay (2018). 2018.

2018

D. J. Ranjith, Sreenath, K., and Dr. Ajith Kumar S., “Studies of vortex structure formed inside a lid driven Cavity-Influence of extending length of cavity”, International Conference on Advances in Materials and Manufacturing Applications (IConAMMA 2018), Amrita Vishwa Vidyapeetham, Bangalore . 2018.

2018

J. A. Sai, R., B., Servant, C., Ravet, F., and Dr. Ajith Kumar S., “Applying ECFM combustion model to spark ignition engine, comparison with experimental data”, 1st International Conference on Future Learning Aspects of Mechanical Engineering (FLAME - 2018) , Amity University, Noida . 2018.

2018

M. Sivan and Dr. Ajith Kumar S., “Effects of orientation on the aerodynamic characteristics of flow over an equilateral triangular cylinder”, 44th National Conference on fluid flow and fluid power (FMFP-2017) , Amrita Vishwa Vidyapeetham, Amritapuri, Kollam . 2018.

2018

Sanju Santhosh and Dr. Ajith Kumar S., “Effects of Buoyancy on the Reattachment Length in Flow over Heated Vertical Backward Facing Step”, The Eleventh International Conference on Thermal Engineering-Theory and Applications - ICTEA 2018, Doha - Qatar. 2018.[Abstract]


Two-dimensional Incompressible flow over vertical backward facing step with a hot downstream wall is analyzed numerically for the laminar mixed convection regime. A modified SIMPLE algorithm is used for solving the governing partial differential equations of the flow. The entire analysis is performed for a single expansion ratio of 2. The effect of aiding/opposing buoyancy on the reattachment length is investigated for wide range of Richardson numbers and at three different Reynold numbers, holding the boussinesq assumption intact. We found the buoyancy critically influences the reattachment length.

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2016

Dr. Ajith Kumar S., Mekha M. Menon, A. P. Sayooj, A. Sameen, and S. Anil Lal, “The effect of surface temperature on the vortex shedding in flow past circular cylinder”. pp. 565-568, 2016.[Abstract]


Flow past a heated/cooled circular cylinder is computationally investigated in this paper. The presence of a buoyancy force arising due to a change in density alter the vortex shedding dynamics. The governing equations, Navier-Stokes and energy equation within the Boussinesq approximation along with continuity equation are solved using a hybrid FEM-FVM technique. In this work we focus on the minimum Reynolds number at which vortex shedding occur. In hydrodynamic stability literature, this value is most often termed as the critical Reynolds number, which is approximately 47 for flow past an unheated cylinder. This demarcation between steady and unsteady regimes of the flow changes due to surface temperature. Due to an increase in surface temperature the frequency of vortex shedding is known to enhance. We show that the nondimensional shedding frequency, the Strouhal number increases with heating and has a strong dependence on Prandtl number and Richardson number of the flow, which are a measure of fluid diffusivities and buoyancy force respectively. We also discuss the regime of complete suppression of vortex shedding due to cylinder surface temperature.

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2014

Aswathy Nair K., Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Self-similar profiles of boundary layer flows over porous laminated flat plate”, 67th Annual Meeting of the American Physical Society Division of Fluid Dynamics , San Francisco, CA, USA . 2014.

2014

R. R. and Dr. Ajith Kumar S., “Numerical Study on Dynamics of Heat transfer in Electronic Cooling”, International Conference on Materials Mechanics and Management (IMMM) , Trivandrum, India. 2014.

2014

Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Transition of three dimensional wake of a flow past a heated cylinder”, IUTAM symposium on ”multiphase flows with phase change, challenges and oppurtunities” , Hyderabad, India. 2014.

2014

Aparna Prabhakaran, Parvathavardhini, , and Dr. Ajith Kumar S., “Influence of hydrophobic surface on flow past circular cylinder”, International Conference on Materials Mechanics and Management . Trivandrum, 2014.

2014

Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Three dimensional wake transition of flow past a heated cylinder”, IUTAM symposium on ”Advances in computation, modeling and control of transitional and turbulent flows” , Goa, India. 2014.

2013

Dr. Ajith Kumar S., S. Anil Lal, and A. Sameen, “Spanwise plumes in wakes behind heated cylinder”, 66th Annual Meeting of the American Physical Society Division of Fluid Dynamics, Pittsburgh, Pennsylvania . 2013.[Abstract]


3D wake transition in flow past cylinder is interesting theoreticallyand industrially. A three dimensional Finite volume computation has beenperformed on an incompressible flow past heated cylinder to understandthe wake behavior behind the cylinder, under the Boussinesq assumption.We study the heat transfer characteristics and the coherent structuresbehind the cylinder at different Prandtl numbers. In forced convection,the 3D transition occurs above Reynolds number, Re = 180-190 (Re isbased on the cylinder diameter). However, the present 3D computationalanalyses show that in mixed convection, the so called ``mode-E''instability (3D transition of wake behind the cylinder caused by theheating of the cylinder) happens at a much lower Reynolds number. Theco-existence of mushroom like coherent structures called the plumesalong with the shed vortices is observed for a range of heatingconditions. These plumes originates from the core of the upper vortexrows at a definite span wise wavelengths. The dependence of Prandtlnumber on the span wise wavenumber of these plumes is also analyzed.

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2011

Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Flow past a moderately heated horizontal cylinder at low Reynolds number”, 64th Annual Meeting of the American Physical Society Division of Fluid Dynamics , Baltimore, USA . 2011.

2010

Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Studies on Flow Past A Horizontal Cylinder At Low Reynolds Number”, International Conference on Materials Mechanics and Management (IMMM), Trivandrum, India. 2010.

Publication Type: Journal Article

Year of Publication Title

2019

Sourav N. Kumar, H. Akhilesh Vishnu, and Dr. Ajith Kumar S., “Influence of Extending the Height on the Vortex Structures Generated Inside A Lid Driven Cavity”, IOP Conference Series: Materials Science and Engineering, vol. 577, p. 012151, 2019.[Abstract]


A numerical study is conducted to study the effect of aspect ratio (extending the height) on the natural convection flow inside a square cavity. 2D incompressible equations are solved using the open CFD package OpenFOAM. A domain and grid independence study is conducted for getting the optimum dimensions and the grid size used in the problem. The validation is done for benchmark problems before applying on to the problem. The vortices formed inside the enclosure is identified by the help of streamlines. This paper clearly discusses the different regimes formed by changing the aspect ratio.

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2019

J. A. Sai, Balamurugan, R., Servant, C., Ravet, F., and Dr. Ajith Kumar S., “Applying ECFM Combustion Model to Spark Ignition Engine, Comparison with Experimental Data”, Advances in Fluid and Thermal Engineering- Part of the Lecture Notes in Mechanical Engineering book series (LNME), pp. 729-741, 2019.[Abstract]


In order to increase the efficiency of the engine and reduce emissions, right sizing plays a predominant role. Validation of turbulent combustion in engine environment using numerical tools is even more challenging. For better understanding of the thermodynamic and chemical behaviour of gas, a proper CFD models set-up should be used to represent turbulence, heat model, ignition, flame propagation and knock. This paper presents an application of ECFM (Extended Coherent Flame Model) as a combustion model coupled with ISSIM (Imposed Stretch Spark Ignition Model) to create the flame kernel due to spark. Two mechanisms named stretching and wrinkling affect the development of the flame front. Stretching is a result from turbulent velocity, and wrinkling is a result from turbulent length scale. The effect of the ECFM model constant addressing stretching and wrinkling, and the process to fix those parameters are briefed in this paper. The simulation results have showed a very good agreement with the combustion test results of RENAULT Engine in terms of pressure, heat release rate and combustion duration.

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2016

Dr. Ajith Kumar S., S. Anil Lal, and A. Sameen, “Flow past a moderately heated horizontal cylinder at low Reynolds number”, Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, vol. 230, no. 7, pp. 1224-1239 , 2016.[Abstract]


In the present work, the influence of heat on vortex shedding and thewake structure in a flow cylinder is analyzed. Flow past a heated twodimensional cylinder in the laminar regime is investigated in the rangeof Reynolds numbers 25 to 100 under varying buoyancy conditions,0<=Ri<=1.0 (where Ri is the Richardson number, indicates therelative dominance of the inertial and buoyant effects). A hybridFEM-FVM method is used to solve Navier-Stokes and energy equations. Thevortex shedding frequency defined non-dimensionally as Strouhal numberis observed to be increasing with heating. Vortex shedding behind heatedcylinder exhibit asymmetry in wake region due to stable and unstabledensity stratification below and above the cylinder respectively. Anegative lift is generated due to heating, in an otherwise symmetriczero time-averaged lift configuration, due to skewness in vortexshedding towards the direction of buoyancy. We also note that theheating brings down the drag slightly for the cases considered here. Wealso note here that at large Ri, the drag coefficient (CD)decrease by ˜30% at Re=25, percentage of decrease being lesspronounced at higher Re (=100).

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2016

Dr. Ajith Kumar S., Manikandan Mathur, A. Sameen, and S. Anil Lal, “Effects of Prandtl number on the laminar cross flow past a heated cylinder”, Physics of Fluids, vol. 28, no. 11, p. 113603, 2016.[Abstract]


Flow past a heated cylinder at constant surface temperature is computationally simulated and analyzed in the laminar regime at moderate buoyancy. The parameters governing the flow dynamics are the Reynolds number, Re, the Richardson number, Ri, and the Prandtl number, Pr. We perform our computations in the range 10 ≤ Re ≤ 35, for which the flow past an unheated cylinder results in a steady separation bubble, and vary the other two parameters in the range 0 ≤ Ri ≤ 2, 0.25 ≤ Pr ≤ 100. The heat transfer from the entire cylinder surface, quantified by the average Nusselt number Nuavg, is shown to obey Nuavg = 0.7435Re0.44Pr0.346 in the mixed convection regime we investigate. For a fixed Re and Pr, the flow downstream of the cylinder becomes asymmetric as Ri is increased from zero, followed by a complete disappearance of the vortices in the recirculation bubble beyond a threshold value of Ri. For a fixed Re and Ri, the vortices in the recirculation bubble are again observed to disappear beyond a threshold Pr, but with the reappearance of both the vortices above a larger threshold of Pr. In the limit of large Pr, the time-averaged flow outside the thermal boundary layer but within the near-wake region regains symmetry about the centerline and ultimately converges to a flow field similar to that of Ri = 0; in the far-wake region, however, we observe asymmetric vortex shedding for moderate Pr. The thermal plume structure in the cylinder wake is then discussed, and the plume generation is identified at points on the cylinder where the Nusselt number is a local minimum. The difference between the plume generation and the flow separation locations on the cylinder is shown to converge to zero in the limit of large Pr. We conclude by plotting the lift and drag coefficients as a function of Ri and Pr, observing that CD decreases with Ri for Pr < Prt (and vice versa for Pr > Prt), where Prt ≈ 7.5.

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2013

Aswathy Nair K., Dr. Ajith Kumar S., A. Sameen, and S. Anil Lal, “Effect of Prandtl number on Heat Transfer In Flow Past A heated cylinder”, International Journal of Innovative Research in Science, Engineering and Technology, vol. 2, no. 1, pp. 416-421 , 2013.[Abstract]


The flow past a heated cylinder is studied numeri-cally in the steady separated buoyancy aided flow regime (Reynolds number < 47) by using a hybrid finite element finite volume (FEM-FVM) solver. In this study we eluci-date the physics behind the Prandtl number effects on heat transfer from the cylinder surface

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2011

Dr. Ajith Kumar S., S. Anil Lal, and A. Sameen, “Influence of slip on flow past cylinder at low Reynolds number”, Proc. IUTAM Symposium on Bluff Body Wakes, Kanpur, India, S. Mittal and G. Biswas (Ed.) , vol. 1, pp. 275-278, 2011.