Imperial College London

ProfessorSpencerSherwin

Faculty of EngineeringDepartment of Aeronautics

Professor of Computational Fluid Mechanics
 
 
 
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Contact

 

+44 (0)20 7594 5052s.sherwin Website

 
 
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Location

 

359Roderic Hill BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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267 results found

Xu H, Hall P, sherwin S, Effect of curvature modulation on Gortler vortices in boundary layers, 67th Annual Meeting of the APS Division of Fluid Dynamics

CONFERENCE PAPER

Xu H, Mughal MS, Gowree ER, Sherwin Set al., Effect of a 3d indentation on boundary layer instability, ICAS 2016, 30th Congress of the International Council of the Aeronautical Sciences, Publisher: ICAS

CONFERENCE PAPER

Xu H, Mughal MS, Sherwin S, Effect of a 3D surface depression on boundary layer transition, 68th Annual Meeting of the APS Division of Fluid Dynamics

The influence of a three-dimensional surface depression on the transitional boundary layer is investigated numerically. In the boundary layer transition, the primary mode is a Tollmien-Schlichting (TS) wave which is a viscous instability. These modes are receptive to surface roughness interacting with free stream disturbances and/or surface vibrations. In this paper, numerical calculations are carried out to investigate the effect of the depression on instability of the boundary layer. In order to implement linear analysis, two/three (2D/3D)-dimensional nonlinear Navier-Stokes equations are solved by spectral element method to generate base flows in a sufficient large domain. The linear analyses are done by the parabolic stability equations (PSE). Finally, a DNS calculation is done to simulate the boundary layer transition.

CONFERENCE PAPER

Xu H, Sherwin S, Hall P, Transmission coefficient of Tollmien-Schlichting waves undergoing small indentation/hump distortion, The 29th Congress of the International Council of the Aeronautical Sciences

CONFERENCE PAPER

Xu H, lombard J, sherwin S, Delaying natural transition of a boundary layer using smooth steps, Sixth International Symposium on Bifurcations and Instabilities in Fluid Dynamics

CONFERENCE PAPER

Chooi KY, Comerford A, Sherwin SJ, Weinberg PDet al., 2017, Noradrenaline has opposing effects on the hydraulic conductance of arterial intima and media., J Biomech, Vol: 54, Pages: 4-10

The uptake of circulating macromolecules by the arterial intima is thought to be a key step in atherogenesis. Such transport is dominantly advective, so elucidating the mechanisms of water transport is important. The relation between vasoactive agents and water transport in the arterial wall is incompletely understood. Here we applied our recently-developed combination of computational and experimental methods to investigate the effects of noradrenaline (NA) on hydraulic conductance of the wall (Lp), medial extracellular matrix volume fraction (ϕ(ECM)) and medial permeability (K1(1)) in the rat abdominal aorta. Experimentally, we found that physiological NA concentrations were sufficient to induce SMC contraction and produced significant decreases in Lp and increases in ϕ(ECM). Simulation results based on 3D confocal images of the extracellular volume showed a corresponding increase in K1(1), attributed to the opening of the ECM. Conversion of permeabilities to layer-specific resistances revealed that although the total wall resistance increased, medial resistance decreased, suggesting an increase in intimal resistance upon application of NA.

JOURNAL ARTICLE

Ekelschot D, Moxey D, Sherwin SJ, Peiro Jet al., 2017, A p-adaptation method for compressible flow problems using a goal-based error indicator, COMPUTERS & STRUCTURES, Vol: 181, Pages: 55-69, ISSN: 0045-7949

JOURNAL ARTICLE

Mohamied Y, Sherwin SJ, Weinberg PD, 2017, Understanding the fluid mechanics behind transverse wall shear stress, JOURNAL OF BIOMECHANICS, Vol: 50, Pages: 102-109, ISSN: 0021-9290

JOURNAL ARTICLE

Moura RC, Mengaldo G, Peiro J, Sherwin SJet al., 2017, On the eddy-resolving capability of high-order discontinuous Galerkin approaches to implicit LES / under-resolved DNS of Euler turbulence, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 330, Pages: 615-623, ISSN: 0021-9991

JOURNAL ARTICLE

Serson D, Meneghini JR, Sherwin SJ, 2017, Direct numerical simulations of the flow around wings with spanwise waviness at a very low Reynolds number, COMPUTERS & FLUIDS, Vol: 146, Pages: 117-124, ISSN: 0045-7930

JOURNAL ARTICLE

Xu H, Lombard JEW, Sherwin SJ, 2017, Influence of localised smooth steps on the instability of a boundary layer, Journal of Fluid Mechanics, Vol: 817, Pages: 138-170, ISSN: 0022-1120

© 2017 Cambridge University Press.We consider a smooth, spanwise-uniform forward-facing step defined by a Gauss error function of height 4 %-30 % and four times the width of the local boundary layer thickness δ99. The boundary layer flow over a smooth forward-facing stepped plate is studied with particular emphasis on stabilisation and destabilisation of the two-dimensional Tollmien-Schlichting (TS) waves and subsequently on three-dimensional disturbances at transition. The interaction between TS waves at a range of frequencies and a base flow over a single or two forward-facing smooth steps is conducted by linear analysis. The results indicate that for a TS wave with a frequency F ∈ [140, 160] (F = ων/U∝2 × 106 where ω and U∝ denote the perturbation angle frequency and free-stream velocity magnitude, respectively, and denotes kinematic viscosity), the amplitude of the TS wave is attenuated in the unstable regime of the neutral stability curve corresponding to a flat plate boundary layer. Furthermore, it is observed that two smooth forward-facing steps lead to a more acute reduction of the amplitude of the TS wave. When the height of a step is increased to more than 20 % of the local boundary layer thickness for a fixed width parameter, the TS wave is amplified, and thereby a destabilisation effect is introduced. Therefore, the stabilisation or destabilisation effect of a smooth step is typically dependent on its shape parameters. To validate the results of the linear stability analysis, where a TS wave is damped by the forward-facing smooth steps direct numerical simulation (DNS) is performed. The results of the DNS correlate favourably with the linear analysis and show that for the investigated frequency of the TS wave, the K-type transition process is altered whereas the onset of the H-type transition is delayed. The results of the DNS suggest that for the perturbation with the non-dimensional frequency parameter F =

JOURNAL ARTICLE

Bao Y, Palacios R, Graham M, Sherwin Set al., 2016, Generalized thick strip modelling for vortex-induced vibration of long flexible cylinders, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 321, Pages: 1079-1097, ISSN: 0021-9991

JOURNAL ARTICLE

Bolls A, Cantwell CD, Moxey D, Serson D, Sherwin SJet al., 2016, An adaptable parallel algorithm for the direct numerical simulation of incompressible turbulent flows using a Fourier spectral/hp element method and MPI virtual topologies, COMPUTER PHYSICS COMMUNICATIONS, Vol: 206, Pages: 17-25, ISSN: 0010-4655

JOURNAL ARTICLE

Chooi KY, Comerford A, Sherwin SJ, Weinberg PDet al., 2016, Intimal and medial contributions to the hydraulic resistance of the arterial wall at different pressures: a combined computational and experimental study, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 13, ISSN: 1742-5689

JOURNAL ARTICLE

Lombard J-EW, Moxey D, Sherwin SJ, Hoessler JFA, Dhandapani S, Taylor MJet al., 2016, Implicit Large-Eddy Simulation of a Wingtip Vortex, AIAA JOURNAL, Vol: 54, Pages: 506-518, ISSN: 0001-1452

JOURNAL ARTICLE

Mengaldo G, De Grazia D, Vincent PE, Sherwin SJet al., 2016, On the Connections Between Discontinuous Galerkin and Flux Reconstruction Schemes: Extension to Curvilinear Meshes, JOURNAL OF SCIENTIFIC COMPUTING, Vol: 67, Pages: 1272-1292, ISSN: 0885-7474

JOURNAL ARTICLE

Moura RC, Sherwin SJ, Peiro J, 2016, Eigensolution analysis of spectral/hp continuous Galerkin approximations to advection-diffusion problems: Insights into spectral vanishing viscosity, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 307, Pages: 401-422, ISSN: 0021-9991

JOURNAL ARTICLE

Moxey D, Cantwell CD, Kirby RM, Sherwin SJet al., 2016, Optimising the performance of the spectral/hp element method with collective linear algebra operations, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, Vol: 310, Pages: 628-645, ISSN: 0045-7825

JOURNAL ARTICLE

Moxey D, Ekelschot D, Keskin U, Sherwin SJ, Peiro Jet al., 2016, High-order curvilinear meshing using a thermo-elastic analogy, COMPUTER-AIDED DESIGN, Vol: 72, Pages: 130-139, ISSN: 0010-4485

JOURNAL ARTICLE

Serson D, Meneghini JR, Sherwin SJ, 2016, Velocity-correction schemes for the incompressible Navier-Stokes equations in general coordinate systems, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 316, Pages: 243-254, ISSN: 0021-9991

JOURNAL ARTICLE

Turner M, Moxey D, Sherwin SJ, Peiró Jet al., 2016, Automatic generation of 3D unstructured high-order curvilinear meshes, Pages: 428-443

The generation of suitable, good quality high-order meshes is a significant obstacle in the academic and industrial uptake of high-order CFD methods. These methods have a number of favourable characteristics such as low dispersion and dissipation and higher levels of numerical accuracy than their low-order counterparts, however the methods are highly susceptible to inaccuracies caused by low quality meshes. These meshes require significant curvature to accuratly describe the geometric surfaces, which presents a number of difficult challenges in their generation. As yet, research into the field has produced a number of interesting technologies that go some way towards achieving this goal, but are yet to provide a complete system that can systematically produce curved high-order meshes for arbitrary geometries for CFD analysis. This paper presents our efforts in that direction and introduces an open-source high-order mesh generator, NekMesh, which has been created to bring high-order meshing technologies into one coherent pipeline which aims to produce 3D high-order curvilinear meshes from CAD geometries in a robust and systematic way.

CONFERENCE PAPER

Xu H, Mughal S, Gowree ER, Sherwin SJet al., 2016, Effect of a 3D indentation on boundary layer instability

We are concerned about effect of a 3D surface indentation on instability and laminar-turbulent transition in a boundary layer. For natural transition in a boundary layer, the transition onset is dominated by growth of the Tollmien-Schlichting (TS) wave and its subsequent secondary instability. In the paper, both linear analysis and nonlinear calculations are carried out to address the 3D surface indentation effect on amplifying TS waves' amplitudes and prompting transition onset. By the linear analysis, we address sudden amplification of the TS modes by a separation bubble in a surface indentation region. The nonlinear calculations are implemented to validate the traditional transition criteria predicted by the linear theory when a 3D indentation is present. Finally, applicability of the traditional transition criteria is assessed.

CONFERENCE PAPER

Xu H, Sherwin SJ, Halle P, Wu Xet al., 2016, The behaviour of Tollmien-Schlichting waves undergoing small-scale localised distortions, JOURNAL OF FLUID MECHANICS, Vol: 792, Pages: 499-525, ISSN: 0022-1120

JOURNAL ARTICLE

Yakovlev S, Moxey D, Kirby RM, Sherwin SJet al., 2016, To CG or to HDG: A Comparative Study in 3D, JOURNAL OF SCIENTIFIC COMPUTING, Vol: 67, Pages: 192-220, ISSN: 0885-7474

JOURNAL ARTICLE

Ali RL, Cantwell CD, Qureshi NA, Roney CH, Lim PB, Sherwin SJ, Siggers JH, Peters NSet al., 2015, Automated fiducial point selection for reducing registration error in the co-localisation of left atrium electroanatomic and imaging data, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 1989-1992, ISSN: 1557-170X

CONFERENCE PAPER

Cantwell C, Sherwin SJ, Moxey D, 2015, Nektar++

Nektar++ is a tensor product based finite element package designed to allow one to construct efficient classical low polynomial order h-type solvers (where h is the size of the finite element) as well as higher p-order piecewise polynomial order solvers.

SOFTWARE

Cantwell C, sherwin SJ, moxey DM, 2015, Nektar++

Nektar++ is a tensor product based finite element package designed to allow one to construct efficient classical low polynomial order h-type solvers (where h is the size of the finite element) as well as higher p-order piecewise polynomial order solvers.

SOFTWARE

Cantwell CD, Moxey D, Comerford A, Bolis A, Rocco G, Mengaldo G, de Grazia D, Yakovlev S, Lombard J-E, Ekelschot D, Jordi B, Xu H, Mohamied Y, Eskilsson C, Nelson B, Vos P, Biotto C, Kirby RM, Sherwin SJet al., 2015, Nektar++: An open-source spectral/hp element framework, Computer Physics Communications, Vol: 192, Pages: 205-219, ISSN: 1879-2944

Nektar++ is an open-source software framework designed to support the development of high-performance scalable solvers for partial differential equations using the spectral/hphp element method. High-order methods are gaining prominence in several engineering and biomedical applications due to their improved accuracy over low-order techniques at reduced computational cost for a given number of degrees of freedom. However, their proliferation is often limited by their complexity, which makes these methods challenging to implement and use. Nektar++ is an initiative to overcome this limitation by encapsulating the mathematical complexities of the underlying method within an efficient C++ framework, making the techniques more accessible to the broader scientific and industrial communities. The software supports a variety of discretisation techniques and implementation strategies, supporting methods research as well as application-focused computation, and the multi-layered structure of the framework allows the user to embrace as much or as little of the complexity as they need. The libraries capture the mathematical constructs of spectral/hphp element methods, while the associated collection of pre-written PDE solvers provides out-of-the-box application-level functionality and a template for users who wish to develop solutions for addressing questions in their own scientific domains.

JOURNAL ARTICLE

Cantwell CD, Roney CH, Ng FS, Siggers JH, Sherwin SJ, Peters NSet al., 2015, Techniques for automated local activation time annotation and conduction velocity estimation in cardiac mapping, COMPUTERS IN BIOLOGY AND MEDICINE, Vol: 65, Pages: 229-242, ISSN: 0010-4825

JOURNAL ARTICLE

Comerford A, Chooi KY, Nowak M, Weinberg PD, Sherwin SJet al., 2015, A combined numerical and experimental framework for determining permeability properties of the arterial media, BIOMECHANICS AND MODELING IN MECHANOBIOLOGY, Vol: 14, Pages: 297-313, ISSN: 1617-7959

JOURNAL ARTICLE

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