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

Dr. Srikrishnan A. R. completed his Ph. D. from IIT Madras in 1996, in the field of fuel-air mixing and combustion in supersonic flows as applied to advanced aerospace propulsion systems.

Industrial Experience: 1996-2012: Worked for 16 years with the global leaders in CAE Fluent Inc and ANSYS holding leadrship positions. Headed one of the technical divisions of ANSYS, India, Pune as the Director of Development from 2008 to 2012.

Joined the department of Aerospace Engineering, Amrita Vishwa Vidyapeetham in June 2012.

Fields of Expertise: Heat Transfer, Combustion, Gas Dynamics, Air-breathing Propulsion Systems, Computational Fluid Dynamics (CFD).

Publications: Publications include papers in the AIAA Journal of Propulsion and Power, Combustion and Flame Journal, Journal of Aerospace Technology and the ASCE Journal of Aerospace Engineering (Details below).

Dr. Srikrishnan has been serving as reviewers for International journals including the Journal of Aerospace Engineering, Institution of Mechanical Engineers, UK.

Research Collaboration

International: Royal Academy of Engineering, London and Imperial College, London

National:

  • LPSC, ISRO
  • GTRE, DRDO
  • IGCAR, DAE
  • ACRD, IIT Madaras

Funded Projects

Domain of Study Funding Agency
Studies on the Onset of Coking in Sem-cryogenic Rocket Engines ISRO
Studies on Effusion Cooling of Gas Turbine Combustors GTRE - DRDO
Studies on modeling of Thermal Striping and Gas Entrainment in PFBR IGCAR
Modeling of Combustion in Biomass-fueled Cook stoves RAE, London, Uk

Invited Talks/Lectures:

  1. Computations Methods in Engineering Design at IIT, Palakkad – 2015.
  2. Application of CFD in Engineering, at IIT RAE, London, Uk, Palakkad – 2016.
  3. CFD in Mechanical Engineering (Introductory lecture for UG Students) at IIT Palakkad, 2017.
  4. Invited talk at AICTE Funded work shop in Heat Transfer at Coimbatore Institute of Technology, 2016.
  5. Session talk at 44th National Conference on Fluid Mechanics and Fluid Power (FMFP) at Amrita Campus, Amritapuri, December 2017.

Research Guidance

Ph. D. (On-going)

1. Shock-Induced Separation in Rocket Nozzles

  1. A study with immense application potential in rocket technology. The fundamental issue of shock induced boundary layer separation is being investigated with emphasis on a novel approach to control it.
  2. The initial results, based on numerical simulations are encouraging and are being explored further.

2. Flame Stabilization in Afterburners using Metallic Foams

  1. The study aims at an innovative approach to flame stabilization in high-speed flows. An important field of application is turbojet engines with after burners. The use of metal foams, which have several advantages over conventional methods, is being studied from the perspective of energy efficiency and effectiveness. The study involves both experimental and numerical investigations.

3. Optimization studies on material management for aircraft maintenance

Recent Manuscript Review Activities (for International Journals and Conferences)

  1. June 2017: Journal - PART G: Journal of Aerospace Engineering, Institution of Mechanical Engineers, UK
  2. July 2017: PART G: Journal of Aerospace Engineering, Institution of Mechanical Engineers, UK
  3. Dec. 2017: International Conference on Computational Methods in Engineering and Health Sciences, Manipal University
  4. March 2017: Journal of the National Academy of Sciences
  5. April 2018: Journal of Aerospace Engineering (Part G), Institution of Mechanical Engineers, UK

Subjects Taught

UG Courses

Theory Courses handled from 2012:

  1. Introduction to Aerospace Propulsion
  2. Air Breathing Engines
  3. Heat Transfer
  4. Rocket and Spacecraft Propulsion
  5. Compressible Fluid Flows

PG/PhD Courses:

  1. Advanced Gas Dynamics
  2. Aircraft Propulsion

Publications

Publication Type: Journal Article

Year of Conference Publication Type Title

2018

Journal Article

H. G Subramanian, Nagarjun, C. H. V. S., Kumar, K. V. Satish, B Kumar, A., Srikanth, V., and Dr. Srikrishnan A. R., “Mixing enhancement using chevron nozzle: studies on free jets and confined jets”, Sādhanā, vol. 43, p. 109, 2018.[Abstract]


This paper reports an experimental study focused on the impact of chevrons (serrations on the trailing edge of the nozzle) on the mixing process of an incompressible jet issuing from a convergent nozzle. The study also explores enhancement of the mixing performance by a novel approach to geometry modification. Profiles of mean velocity were used to characterize the extent of mixing. For a comparative assessment, studies were carried out with a base line circular nozzle, a conventional chevron nozzle and an improvised tabbed chevron nozzle. Flow visualization studies were carried out for jets issuing from chevron nozzles and the results corroborate well with quantitative measurements. The impact of confinement on mixing of jets issuing from chevron nozzles is also studied. The results show that the proposed geometry modification can significantly improve the rate of mixing in the range of Reynolds numbers considered in the study. In confined jets, presence of chevrons was found to accelerate the process of jet break-down.

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2018

Journal Article

V. Venkatesh, J., S., D., B. Vignesh, K., S., Velamati, R. Kishore, Dr. Srikrishnan A. R., Ramakrishnananda, B., and Batchu, S., “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

Journal Article

S. Iyer, K, A., R, A., and Dr. Srikrishnan A. R., “Combined Effect of Surface Roughness and Wake Splitter Plate on the Aerodynamic Characteristics of a Circular Cylinder”, IOP Conference Series: Materials Science and Engineering, vol. 234, p. 012007, 2017.[Abstract]


This paper is focussed on numerical investigation of flow around a stationary circular cylinder (diameter, D) with selectively applied surface roughness (roughness strips with thickness 'k') in the presence of a wake splitter plate (length, L). The plate leading edge is at a distance of 'G' from the cylinder base. For this study, the commercial software ANSYS Fluent is used. Fluid considered is water. Study was conducted the following cases (a) plain cylinder (b) cylinder with surface roughness (without splitter plate) (c) Cylinder with splitter plate (without surface roughness) and (d) cylinder with both roughness and splitter plate employed. The study Reynolds number (based on D) is 17,000 and k/δ = 1.25 (in all cases). Results indicate that, for cylinder with splitter plate (no roughness), lift coefficient gradually drops till G/D=1.5 further to which it sharply increases. Whereas, drag coefficient and Strouhal number undergoes slight reduction till G/D=1.0 and thereafter, gradually increase. Circumferential location of strip (α) does not influence the aerodynamic parameters significantly. With roughness alone, drag is magnified by about 1.5 times and lift, by about 2.7 times that of the respective values of the smooth cylinder. With splitter plate, for roughness applied at all 'α' values, drag and lift undergoes substantial reduction with the lowest value attained at G/D=1.0.

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2017

Journal Article

M. Prabhu, R. Kumar, A., Nair, R. R., and Dr. Srikrishnan A. R., “Air-Core Vortex in Cylindrical Tanks: Effect of Curvature of the Base Plate”, ASCE Journal of Aerospace Engineering, vol. 30, no. 5, 2017.

2017

Journal Article

A. R. Kumar, Nair, R. R., Prabhu, M., and Dr. Srikrishnan A. R., “Vortex Formation during Draining from Cylindrical Tanks: Effect of Drain Port Eccentricity”, Journal of Aerospace Engineering, vol. 30, 2017.[Abstract]


This paper reports an experimental study on the combined effect of drain port eccentricity and port diameter on air core vortex formation in a cylindrical tank with a rotating liquid column. The study is motivated by the need to control air core vortex formation in applications like propellant feed systems of rocket engines. Based on a series of experiments in a water tank with varying discharge port diameter and port eccentricity values, the study shows how the vortex formation can be suppressed using an appropriate combination of diameter and eccentricity of the discharge port. Experiments are carried out over a range of values of initial speed of rotation (60-200 rpm) of the water column. The height of the water column at which the air core vortex extends to the discharge port, is used as a measure of the vortex growth rate. The study proposes a correlation between the critical port diameter (which suppresses vortex formation) and port eccentricity. The intermittency of vortex formation in the eccentric port configuration is also studied using flow visualization. © 2017 American Society of Civil Engineers.

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2016

Journal Article

R. A. Kumar, .J, J., Shaji, R. Korah, and Dr. Srikrishnan A. R., “Vortex Suppression through Drain Port Sizing”, ASCE Journal of Aerospace Engineering, Journal of Aerospace Engineering, vol. 29, no. 4, 2016.[Abstract]


This paper reports on an experimental study motivated by the issue of vortex formation in fuel tanks of liquid propulsion rockets. In this study, vortex funnel (vortex-air core) formation during draining of liquids from cylindrical tanks is suppressed by means of a simple, yet effective method of controlling or adjusting the size of the base drain port. This is particularly relevant in spacecraft and rocket applications where suppression of such vortex-air core is very much warranted because of the possible drain port blockage they cause and the consequent adverse impact (of vortices) on the generation of propulsive thrust. It is found that in the range of rotational speeds provided to the liquid column (between 120 and 200 rpm) in a cylindrical tank, for d/D∼0.03 (where D is the tank diameter held constant in the study, and d is the port diameter that is varied in the experiments), vortex funnel formation is completely eliminated for concentric drain ports. For eccentric ports, this occurs at a slightly higher value of port size, viz., d/D∼0.04. The liquid used is water at room temperature with its free surface open to the atmosphere.

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2013

Journal Article

R. Korah Shaji, Gowda, B. H. L., Joshy, P. J., Dr. Srikrishnan A. R., and Kumar, R. A., “Effect Of Relative Drain Port Size On Vortex Formation In Cylindrical Tanks”, International Conference on Fluid Dynamics, 2013.

2004

Journal Article

Dr. Srikrishnan A. R., “Putting Brakes - an analysis of the fundamentals involved in aerobraking”, Article in Times Fluid Power Journal, 2004.

2002

Journal Article

B. Singh Chufal and Dr. Srikrishnan A. R., “CFD Analysis of Film Cooling of a Cylindrical Leading Edge with Compound Angle Injection”, International Conference on Scientific & Engineering Computation, 2002.

1999

Journal Article

Dr. Srikrishnan A. R., Kurian, J., and Sriramulu, V., “Comparative Experimental study of Supersonic Combustors”, Comparative Experimental study of Supersonic Combustors, 1999.

1996

Journal Article

Dr. Srikrishnan A. R., Kurian, J., and Sriramulu, V., “An experimental investigation of thermal mixing and combustion in supersonic flows”, Combustion and Flame, vol. 107, pp. 464 - 474, 1996.[Abstract]


A radially lobed nozzle (petal nozzle) is being increasingly recognised as a potential candidate for promoting mixing in compressible flows. An experimental investigation has been conducted to study its effectiveness in improving thermal mixing and combustion in supersonic flow. A hot gas jet issuing supersonically from a lobed nozzle mixes with a cold supersonic jet in a circular mixing tube. The two jets issue coaxially. A detailed survey of the flow field inside the mixing duct reveals that nearly complete thermal mixing (as exemplified by the nearly uniform temperature distribution) could be achieved in a short distance when a lobed nozzle is employed. The results also indicate the presence of large-scale vortices in the flow field downstream of the lobed nozzle. Having thus created a field in which mixing is good, supersonic combustion was then attempted. Kerosene was introduced into the hot stream issuing from the lobed nozzle and it burned mainly in the mixing tube, which served as a supersonic combustor. Resulting temperature and pressure rises were measured and the supersonic combustion efficiency was found to be of the order of 60%. The performance of a conventional conical nozzle was found to be much inferior to that of the petal nozzle under identical conditions.

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1996

Journal Article

Dr. Srikrishnan A. R., J., K., and Sriramulu, V., “An Experimental Study of Thermal Mixing and Combustion in Supersonic Flows”, Journal of Combustion and Flame, vol. 107, no. 4, pp. 464-474, 1996.

1996

Journal Article

Dr. Srikrishnan A. R., J, K., and V, S., “Enhancement of thermal mixing in coaxial supersonic jets”, Journal of Propulsion and Power - J PROPUL POWER, vol. 12, no. 4, pp. 730-735, 1996.[Abstract]


An experimental study was conducted to investigate the thermal mixing of a hot, supersonic, primary jet of combustion gases with a coflowing secondary jet of air at ambient temperature, The Mach numbers of the two Sets were 1.2 and 1.7, respectively, To enhance the mixing, the fore (primary) jet was admitted through a three-dimensional, radially lobed nozzle, referred to as the petal nozzle. The uniformity of stagnation temperature in the flowfield was used to characterize the extent of mixing between the Sets, The effect of confinement on the mixing Was also investigated, The mixing performance of the lobed nozzle and the associated loss in stagnation pressure were compared with those for a conventional conical nozzle, The study confirms the efficacy of the radially lobed nozzle in thermal and momentum mixing of supersonic jets and highlights its potential in supersonic combustion systems.

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1996

Journal Article

Dr. Srikrishnan A. R., Kurain, J., and Sriramulu, V., “Experimental study on mixing enhancement by petal nozzle in supersonic flow”, Journal of Propulsion and PowerJournal of Propulsion and Power, vol. 12, no. 1, pp. 165 - 169, 1996.[Abstract]


An experimental study on mixing enhancement in supersonic flow by a radially lobed nozzle, called petal nozzle, has been conducted. The study entails the mixing of a supersonic primary stream and a coflowing sonic secondary stream in cold flow. The radial distribution of momentum flux is characterized by a mixing parameter called the degree of mixing. The loss in stagnation pressure associated with the mixing is also determined. With emphasis on momentum mixing and pressure drop, the petal nozzle and the conventional conical nozzle have been compared so as to assess the suitability of the former. The results show that using an optimum length of the mixing chamber, a compromise can be struck between the mixing enhancement and the associated increase in pressure loss. The contribution of shear area at the nozzle exit to mixing enhancement was found to be marginal.

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Publication Type: Conference Proceedings

Year of Conference Publication Type Title

2017

Conference Proceedings

R. S. Sarath, R. Kumar, A., Prasad, B. V. S. S. S., and Dr. Srikrishnan A. R., “Numerical Analysis of Effects of Turbine Blade Tip Shape on Secondary Losses”, Fluid Mechanics and Fluid Power – Contemporary Research, Part of the Lecture Notes in Mechanical Engineering book series (LNME), vol. Part F8. Springer India, New Delhi, pp. 871-879, 2017.[Abstract]


This paper deals with a study of the effect of some turbine blade tip shapes on the secondary flows and the associated aerodynamics. A conventional plain tip shape and a novel squealer tip shape are compared aerodynamically using numerical analysis. The simulations are done using a finite volume-based, general purpose CFD solver, ANSYS FLUENT. The investigation was carried out on a turbine blade cascade consisting of three blades, test blade being the central blade which was modelled. The cascade analysis was done to capture the secondary flows and associated losses. Two cases of tip clearance viz., 0 and 1.5 {%} of the blade span were considered in this study contributing to the effect of blade tip geometry. The vorticity magnitude at a selected downstream vertical plane was estimated to aerodynamically compare the tip shapes employed in this study. Due to tip clearance, local secondary flows are found to be generated at the blade tip region. Results obtained in this study further indicate that squealer blade tip reduces the secondary flow losses when compared to the conventional plain turbine blade tips. Reduction in secondary flow losses is expected to subdue the effect of heat loads on blade tips. This is perhaps the most prominent practical implication of this key result. The magnitude of vorticity at the blade tip region for squealer tip with 1.5 {%} tip clearance is 21.25 {%} less than that for plain tip at the blade tip region for the same tip clearance. This is possibly because of separation of flow and recirculation at the squealer rim which induces weak leakage flows.

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2017

Conference Proceedings

G. T. H, Dr. Srikrishnan A. R., and Raghavan, A., “Numerical Study of Effect of Base Dome Radius on Vortex Formation During Tank Draining”, Proceedings of the 44th National Conference on Fluid Mechanics and Fluid Power, Amrita Vishwa Vidyapeetham, Amritapuri Campus, Kollam, Kerala, India. 2017.

2017

Conference Proceedings

A. K. Damu Murali, R Kumar, A., and Dr. Srikrishnan A. R., “A Numerical Investigation on Flow Over Curved Plates”, Proceedings of the 44th National Conference on Fluid Mechanics and Fluid Power, Amrita Vishwa Vidyapeetham, Amritapuri Campus, Kollam, Kerala, India. 2017.

2014

Conference Proceedings

V. U, Raja, D., R, R., Chaturvedi, S., and Dr. Srikrishnan A. R., “Studies on Mass-spillage and Stagnation Pressure Loss in Intakes of SCRAMJET Propulsion Systems”, 6th International Conference ICTACEM, IIT Kharagpur, December, 2014. 2014.

2014

Conference Proceedings

U. Viverjita, Dr. Srikrishnan A. R., and , “Laminar and Transitional Shock-Boundary Layer Interaction in Hypersonic Flows: A Study from Energy Perspective”, 5th International Conference on Fluid Mechanics and Fluid Power. IIT Kanpur, 2014.

2013

Conference Proceedings

Dr. Srikrishnan A. R., “Validation of CFD Software: A Study of Issues Specific to Simulation of High Mach number Flows”, International Conference on CAE. IIT Madras, India, 2013.

2003

Conference Proceedings

S. Dhar and Dr. Srikrishnan A. R., “Numerical Study of Thrust Performance of Supersonic Nozzles with Separated Flow”, 6th Annual CFD Symposium, CFD Division of AeSI. 2003.

1994

Conference Proceedings

Dr. Srikrishnan A. R., J., K., and , “Stagnation Pressure loss associated with Mixing Enhancement in Supersonic Flow”, Proceedings of the 2nd National Conference on Air Breathing Engines and Aerospace Propulsion. VSSC, Thiruvananthapuram, 1994.

1992

Conference Proceedings

Dr. Srikrishnan A. R., K.A., D., and V, S., “Theoretical Investigation of Base Flows and Supersonic External Combustion”, Proceedings of XII National Conference on I.C.Engines and Combustion. pp. 591-596, 1992.

Publication Type: Conference Paper

Year of Conference Publication Type Title

2014

Conference Paper

J. Josy, R. Kumar, A., Dr. Srikrishnan A. R., Shaji, R. K., and .H.L.Gowda, B., “Effect of eccentric drain port size on vortex formation during draining from cylindrical tanks”, in 5th International and 41st National Conference on Fluid Mechanics and Fluid Power (FMFP) 2014, Indian Institute of Technology Kanpur, 2014.

2014

Conference Paper

S. R. S, R, A. Kumar, BVSSS, P., and Dr. Srikrishnan A. R., “Numerical Analysis of Effects of Turbine Blade Tip Shape on Secondary Losses”, in 5th International and 41st National Conference on Fluid Mechanics and Fluid Power (FMFP) 2014, Indian Institute of Technology, Kanpur, 2014.[Abstract]


This paper deals with a study of the effect of some turbine blade tip shapes on the secondary flows and the associated aerodynamics. A conventional plain tip shape and a novel squealer tip shape are compared aerodynamically using numerical analysis. The simulations are done using a finite volume-based, general purpose CFD solver, ANSYS FLUENT. The investigation was carried out on a turbine blade cascade consisting of three blades, test blade being the central blade which was modelled. The cascade analysis was done to capture the secondary flows and associated losses. Two cases of tip clearance viz., 0 and 1.5 % of the blade span were considered in this study contributing to the effect of blade tip geometry. The vorticity magnitude at a selected downstream vertical plane was estimated to aerodynamically compare the tip shapes employed in this study. Due to tip clearance, local secondary flows are found to be generated at the blade tip region. Results obtained in this study further indicate that squealer blade tip reduces the secondary flow losses when compared to the conventional plain turbine blade tips. Reduction in secondary flow losses is expected to subdue the effect of heat loads on blade tips. This is perhaps the most prominent practical implication of this key result. The magnitude of vorticity at the blade tip region for squealer tip with 1.5 % tip clearance is 21.25 % less than that for plain tip at the blade tip region for the same tip clearance. This is possibly because of separation of flow and recirculation at the squealer rim which induces weak leakage flows.

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2014

Conference Paper

U. Viverjita and Dr. Srikrishnan A. R., “Aerothermodynamics of Shock-Boundary Layer Interaction in Hypersonic Flow: A Study on Stagnation Pressure Loss and the Extend of Separation Zone”, in 3rd National Symposium on Shock Waves, IIT Bombay, 2014.

2000

Conference Paper

R. Ch. and Dr. Srikrishnan A. R., “A Numerical Study of Species Mixing in Co-axial Supersonic Jets”, in Annual CFD Symposium, CFD Division of AeSI, 2000.