Dr Ati Sharma
Lecturer

Address:
Dr A S Sharma
Department of Automatic Control and Systems Engineering
University of Sheffield
Mappin Street, Sheffield
S1 3JD
Tel: +44 114 222 5669
Email: a.s.sharma @ sheffield.ac.uk
Room: C6, Amy Johnson Building

Biopic

After graduating as a physicist from UCL, Dr Sharma completed his doctoral thesis in control engineering at Imperial College, London on the modelling and control of tokamak nuclear fusion reactors. Following two years of research and trading in the finance industry, he returned to academia to do a postdoc in flow control, and was then awarded an Imperial College Junior Research Fellowship. Dr Sharma is now a lecturer at ACSE.

Teaching

My teaching interests include topics in control and systems engineering, in particular robust control and its applications with aerospace. Previous teaching experience includes computing for first year Aeronautics students.

I am now teaching ACS406, which is a 4th year course on Robust Control. The course has a wiki here: http://asharma.staff.shef.ac.uk/robustcontrol/index.php/Main_Page.
I'm also teaching introductory Matlab as part of ACS6101 to incoming MSc students.

Research interests

Control of turbulent fluid flows

Research interests include low-order modelling and control of turbulent fluid flows:

• to provide reduced-order models of turbulent fluid flows in order to improve our fundamental understanding of the dominant fluid mechanics;
• to devise control strategies for turbulent flows, for purposes including drag reduction (and therefore improved energy efficiency).
• Some highlights of the collaborative work might include:
• prediction of both the Reynolds number scaling and structure of wall-normal energy distribution, by a frequency-domain input-output analysis of the Navier-Stokes equations;
• the development of computational methods to study non-normal amplification mechanisms responsible for `bypass transition' of fluid flows in complex geometries;
• a model reduction technique suitable for turbulent fluid flows, preserving bounds on turbulent energy production;
• a feedback control strategy that gives a robust global stability result to relaminarise turbulent incompressible flows.

Other Research Interests

State estimation of non-linear systems with non-Gaussian uncertainty, using grid-based Bayesian filtering methods.

The RZIP tokamak model. The RZIP tokamak model is freely available at https://github.com/atisharma/rzip

PhD Projects

For a current list of PhD projects being offered by Dr Sharma, please see the PhD Research Projects web pages

Publications

Refereed journal papers

• TR Bewley, AS Sharma, On regularity requirements in the optimal boundary control of diffusive PDE systems, In preparation (2012)
• BL Jones, PH Heins, EC Kerrigan, JF Morrison, AS Sharma, Modelling for robust feedback control of fluid flows, in preparation (2012)
• R Moarref, BJ McKeon, AS Sharma, JA Tropp, Reynolds number scaling of the low rank approximation to turbulent channel flow, In preparation (2012)
• J-L Bourguignon, AS Sharma, JA Tropp, BJ McKeon, Sparse representations of turbulent pipe flow using a model-based radial basis, In preparation (2012)
• J-L Bourguignon, AS Sharma, JA Tropp, BJ McKeon, Sparse representations of turbulent pipe flow via compressive sampling, In preparation (2012)
• AS Sharma, BJ McKeon, On coherent structure in wall turbulence, Journal of Fluid Mechanics, under review (2012)
• BJ McKeon, AS Sharma, I Jacobi, Experimental manipulation of wall turbulence — a systems approach, Physics of Fluids (invited paper), under review (2012)
• AS Sharma, JF Morrison, BJ McKeon, DJN Limebeer, WH Koberg, SJ Sherwin, Relaminarisation of Reτ = 100 channel flow with globally stabilising linear feedback control, Physics of Fluids 23, 125105 (2011)
• McKeon BJ, Sharma AS, Jacobi I, Predicting structural and statistical features of wall turbulence, 2010(publication )
• TR Bewley, AS Sharma, Efficient grid-based Bayesian estimation of nonlinear low-dimensional systems with sparse non-Gaussian PDFs, Automatica 48, 1286-1290 (2012)
• Bewley TR, Sharma AS, A tractable framework for grid-based Bayesian estimation of nonlinear low-dimensional systems with sparse nongaussian PDFs, Automatica(publication )
• AS Sharma, N Abdessemed, SJ Sherwin, V Theofilis, Transient growth mechanisms of low Reynolds number flow over a low-pressure turbine blade, Theoretical and Computational Fluid Dynamics (invited paper), 2010, 25(1-4) pp.19-30 (doi)
• McKeon BJ, Sharma AS, A critical-layer model for turbulent pipe flow, Journal of Fluid Mechanics, Vol:658, Pages:336-382, ISSN:0022-1120(doi)
• Sharma AS, MODEL REDUCTION OF TURBULENT FLUID FLOWS USING THE SUPPLY RATE, INT J BIFURCAT CHAOS, 2009, Vol:19, Pages:1267-1278, ISSN:0218-1274(doi)
• Abdessemed N, Sharma AS, Sherwin SJ, et al, Transient growth analysis of the flow past a circular cylinder, PHYS FLUIDS, 2009, Vol:21, ISSN:1070-6631(doi)
• Sharma AS, Limebeer DJN, Jaimoukha IM, et al, Modeling and control of TCV, IEEE T CONTR SYST T, 2005, Vol:13, Pages:356-369, ISSN:1063-6536(publication doi)
• Lister JB, Sharma A, Limebeer DJN, et al, Plasma equilibrium response modelling and validation on JT-60U, NUCL FUSION, 2002, Vol:42, Pages:708-724, ISSN:0029-5515
• Lister JB, Khayrutdinov R, Limebeer DJN, et al, Linear and Non-Linear Plasma Equilibrium Responses on the JT60-U and TCV Tokamaks, Fusion Engineering and Design, 2001, Pages:755-759(publication)

Book chapters

• Optimal Growth Modes of Flows in Complex Geometries, IUTAM Symposium on Flow Control and MEMS (2006), IUTAM Bookseries, Volume 7, Part 5, pp.339-343, AS Sharma, N Abdessemed, SJ Sherwin

Refereed conference papers

• R Moarref, BJ McKeon, AS Sharma and JA Tropp, On the Reynolds number scaling of the low-rank approximation to turbulent channel flows, 9th European Fluid Mechanics Conference, Rome (2012)
• AS Sharma, BJ McKeon, A critical layer framework for turbulent pipe flow, Turbulence Colloquium, Marseille (2011)
• AS Sharma, BJ McKeon, Velocity statistics and structure in pipe turbulence derived from a simple critical-layer model, 7th International Symposium on Turbulence and Shear Flow Phenomena (TSFP-7), Ottawa (2011)
• AS Sharma, BJ McKeon, Very Large Scale Motions in Pipe Turbulence Derived from a Simple Critical-layer Model, 7th International Symposioum on Turbulence and Shear Flow Phenomena (TSFP-7), Ottawa, 2011
• McKeon BJ, Sharma AS, Energetic modes in turbulent pipe flow from resolvent analysis, 48th AIAA Aerospace Sciences Meeting, Orlando, Florida, 2010
• McKeon BJ, Sharma AS, A critical layer model for turbulent pipe flow, 16th US National Congress on Theoretical and Applied Mechanics (USNCTAM) 672, 2010
• Bewley T, Sharma AS, On the Convergence of Boundary Control Strategies Designed Using ODE Approximations of Diffusive PDE Systems, Keynote, 8th International Symposium on Dynamics and Control of Process Systems (DYCOPS), Cancun, Mexico, 2007 (publication)
• Sharma AS, McKeon BJ, Perturbation Energy Production in Pipe Flow over a Range of Reynolds Numbers using Resolvent Analysis, 47th AIAA Aerospace Sciences Meeting, Orlando, Florida, 2009 (publication)
• Sharma AS, Limebeer DJN, McKeon BJ, et al, Stabilising Control Laws for the Incompressible Navier-Stokes Equations using Sector Stability Theory, 3rd AIAA Flow Control Conference, AIAA, San Francisco, California, 2005 (publication)
• JB Lister, R Khayrutdinov, DJN Limebeer, V Lukash, Y Nakamura, AS Sharma, JP Wainwright, R Yoshino, Plasma equilibrium response modelling experiments on the JT-60U and TCV tokamaks, 27th EPS Conference on Controlled Fusion and Plasma Physics, Budapest (2000), ECA Vol. 24B, pp181-184, (2000)
• Lister,J.B. , Khayrutdinov,R. , Limebeer,D.J.N. , et al, Linear and non-linear plasma equilibrium responses on the jt-60u and TCV Tokamaks, 21st symposium on fusion technology; (SOFT-21), Madrid, North-Holland, 2001, Pages:755-760

Conference abstracts

• R Moarref, AS Sharma, JA Tropp, BJ McKeon, Model-based scaling and prediction of streamwise energy spectrum at high Reynolds numbers, American Physical Society, Division of Fluid Dynamics, San Diego, California (2012)
• BJ McKeon, AS Sharma, Coherent structure, amplitude modulation and higher order statistics in wall turbulence,  American Physical Society, Division of Fluid Dynamics, San Diego, California (2012)
• AS Sharma, BJ McKeon, Structure from the critical layer framework in turbulent flow, American Physical Society, Division of Fluid Dynamics, Long Beach, US (2010)
• BJ McKeon, AS Sharma, A reinterpretation of the distribution of vortical structure in wall turbulence, American Physical Society, Division of Fluid Dynamics, Long Beach, US (2010)
• JF Morrison, AS Sharma, BJ McKeon, Linear Control of Turbulent Channel Flow and the Role of Pressure, American Physical Society, Division of Fluid Dynamics, Minneapolis, US (2009)
• AS Sharma, BJ McKeon, Energetic modes in turbulent pipe flow from resolvent analysis, American Physical Society, Division of Fluid Dynamics, Minneapolis, US (2009)
• T Bewley, AS Sharma, Grid-based Bayesian Estimation Exploiting Sparsity for systems with non-Gaussian uncertainty, American Physical Society, Division of Fluid Dynamics, Minneapolis, US (2009)
• BJ McKeon, AS Sharma, A critical layer analogy for the very large scale motions in wall turbulence, American Physical Society, Division of Fluid Dynamics, Minneapolis, US (2009)
• AS Sharma, SJ Sherwin, N Abdessemed, DJN Limebeer, Global modes of flows in complex geometries, Third Symposium on Global Flow Instability and Control, Crete (2005)
• AS Sharma, BJ McKeon, JF Morrison, DJN Limebeer, Control of incompressible flows, American Physical Society, Division of Fluid Dynamics, Chicago, US (2005)