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

 

313BCity and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

314 results found

Yakhot A, Feldman Y, Moxey D, Sherwin S, Karniadakis GEet al., 2019, Turbulence in a Localized Puff in a Pipe, Flow, Turbulence and Combustion, ISSN: 1386-6184

© 2019, Springer Nature B.V. We have performed direct numerical simulations of a spatio-temporally intermittent flow in a pipe for Rem = 2250. From previous experiments and simulations of pipe flow, this value has been estimated as a threshold when the average speeds of upstream and downstream fronts of a puff are identical (Barkley et al., Nature 526, 550–553, 2015; Barkley et al., 2015). We investigated the structure of an individual puff by considering three-dimensional snapshots over a long time period. To assimilate the velocity data, we applied a conditional sampling based on the location of the maximum energy of the transverse (turbulent) motion. Specifically, at each time instance, we followed a turbulent puff by a three-dimensional moving window centered at that location. We collected a snapshot-ensemble (10000 time instances, snapshots) of the velocity fields acquired over T = 2000D/U time interval inside the moving window. The cross-plane velocity field inside the puff showed the dynamics of a developing turbulence. In particular, the analysis of the cross-plane radial motion yielded the illustration of the production of turbulent kinetic energy directly from the mean flow. A snapshot-ensemble averaging over 10000 snapshots revealed azimuthally arranged large-scale (coherent) structures indicating near-wall sweep and ejection activity. The localized puff is about 15-17 pipe diameters long and the flow regime upstream of its upstream edge and downstream of its leading edge is almost laminar. In the near-wall region, despite the low Reynolds number, the turbulence statistics, in particular, the distribution of turbulence intensities, Reynolds shear stress, skewness and flatness factors, become similar to a fully-developed turbulent pipe flow in the vicinity of the puff upstream edge. In the puff core, the velocity profile becomes flat and logarithmic. It is shown that this “fully-developed turbulent flash” is very narrow being about t

JOURNAL ARTICLE

Bao Y, Zhu HB, Huan P, Wang R, Zhou D, Han ZL, Palacios R, Graham M, Sherwin Set al., 2019, Numerical prediction of vortex-induced vibration of flexible riser with thick strip method, Journal of Fluids and Structures, ISSN: 0889-9746

© 2019 We present numerical prediction results of vortex-induced vibration (VIV) of a long flexible tensioned riser subject to uniform currents. The VIV model of long length-to-diameter ratio is considered and ‘thick’ strip technique based on high-order spectral/hp element method is employed for computational simulation. The model parameter of the riser for the simulation is chosen according to the dimensional counterparts used in the experimental tests in Lehn (2003). The numerical results are displayed in terms of motion responses, hydrodynamic forces and wake patterns as well and compared and discussed with the available data in the literature.

JOURNAL ARTICLE

Moura RC, Peiró J, Sherwin SJ, 2019, Implicit LES approaches via discontinuous galerkin methods at very large reynolds, ERCOFTAC Series, Pages: 53-59

© Springer Nature Switzerland AG 2019. We consider the suitability of implicit large-eddy simulation (iLES) approaches via discontinuous Galerkin (DG) schemes. These are model-free eddy-resolving approaches which solve the governing equations in unfiltered form and rely on numerical stabilization techniques to account for the missing scales. In DG, upwind dissipation from the Riemann solver provides the baseline mechanism for regularization. DG-based iLES approaches are currently under rapid dissemination due to their success in predicting complex transitional and turbulent flows at moderate Reynolds numbers (Uranga et al, Int J Numer Meth Eng 87(1–5):232–261, 2011, [1], Gassner and Beck, Theor Comput Fluid Dyn 27(3–4):221–237, 2013, [2], Beck et al, Int J Numer Methods Fluids 76(8):522–548, 2014, [3], Wiart et al Int J Numer Methods Fluids 78:335–354, 2015, [4]). However, at higher Reynolds number, accuracy and stability issues can arise due the highly under-resolved character of the computations and the suppression of stabilizing viscous effects.

BOOK CHAPTER

Winters AR, Moura RC, Mengaldo G, Gassner GJ, Walch S, Peiro J, Sherwin SJet al., 2018, A comparative study on polynomial dealiasing and split form discontinuous Galerkin schemes for under-resolved turbulence computations, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 372, Pages: 1-21, ISSN: 0021-9991

JOURNAL ARTICLE

Mengaldo G, Moura RC, Giralda B, Peiro J, Sherwin SJet al., 2018, Spatial eigensolution analysis of discontinuous Galerkin schemes with practical insights for under-resolved computations and implicit LES, COMPUTERS & FLUIDS, Vol: 169, Pages: 349-364, ISSN: 0045-7930

JOURNAL ARTICLE

Calder M, Craig C, Culley D, de Cani R, Donnelly CA, Douglas R, Edmonds B, Gascoigne J, Gilbert N, Hargrove C, Hinds D, Lane DC, Mitchell D, Pavey G, Robertson D, Rosewell B, Sherwin S, Walport M, Wilson Aet al., 2018, Computational modelling for decision-making: where, why, what, who and how, ROYAL SOCIETY OPEN SCIENCE, Vol: 5, ISSN: 2054-5703

JOURNAL ARTICLE

Cohen J, Marcon J, Turner M, Cantwell C, Sherwin SJ, Peiro J, Moxey Det al., Simplifying high-order mesh generation for computational scientists, 10th International Workshop on Science Gateways, Publisher: CEUR Workshop Proceedings, ISSN: 1613-0073

Computational modelling is now tightly integrated into many fields of research in science and industry. Computational fluid dynamics software, for example, gives engineers the ability to model fluid flow around complex geometries defined in Computer-Aided Design (CAD) packages, without the expense of constructing large wind tunnel experiments. However, such modelling requires translation from an initial CAD geometry to a mesh of many small elements that modelling software uses to represent the approximate solution in the numerical method. Generating sufficiently high-quality meshes for simulation is a time-consuming, iterative and error-prone process that is often complicated by the need to interact with multiple command-line tools to generate and visualise the mesh data. In this paper we describe our approach to overcoming this complexity through the addition of a meshing console to Nekkloud, a science gateway for simplifying access to the functionality of the Nektar++ spectral/hp element framework. The meshing console makes use of the NekMesh tool in Nektar++ to help reduce the complexity of the mesh generation process. It offers a web-based interface for specifying parameters, undertaking meshing and visualising results. The meshing console enables Nekkloud to offer support for a full, end-to-end simulation pipeline from initial CAD geometry to simulation results.

CONFERENCE PAPER

Mengaldo G, De Grazia D, Moura RC, Sherwin Set al., 2018, Spatial eigensolution analysis of energy-stable flux reconstruction schemes and influence of the numerical flux on accuracy and robustness, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 358, Pages: 1-20, ISSN: 0021-9991

JOURNAL ARTICLE

Alpresa P, Sherwin S, Weinberg P, van Reeuwijk Met al., 2018, Orbitally shaken shallow fluid layers. I. Regime classification, PHYSICS OF FLUIDS, Vol: 30, ISSN: 1070-6631

JOURNAL ARTICLE

Alpresa P, Sherwin S, Weinberg P, van Reeuwijk Met al., 2018, Orbitally shaken shallow fluid layers. II. An improved wall shear stress model, PHYSICS OF FLUIDS, Vol: 30, ISSN: 1070-6631

JOURNAL ARTICLE

De Grazia D, Moxey D, Sherwin SJ, Kravtsova MA, Ruban AIet al., 2018, Direct numerical simulation of a compressible boundary-layer flow past an isolated three-dimensional hump in a high-speed subsonic regime, PHYSICAL REVIEW FLUIDS, Vol: 3, ISSN: 2469-990X

JOURNAL ARTICLE

Xu H, Cantwell CD, Monteserin C, Eskilsson C, Engsig-Karup AP, Sherwin SJet al., 2018, Spectral/hp element methods: Recent developments, applications, and perspectives, JOURNAL OF HYDRODYNAMICS, Vol: 30, Pages: 1-22, ISSN: 1001-6058

JOURNAL ARTICLE

Bao Y, Palacios R, Graham M, Sherwin Set al., 2018, A Strip Modelling of Flow Past a Freely Vibrating Cable, DIRECT AND LARGE-EDDY SIMULATION X, Vol: 24, Pages: 221-227, ISSN: 1382-4309

JOURNAL ARTICLE

Cassinelli A, Montomoli F, Adami P, Sherwin SJet al., 2018, HIGH FIDELITY SPECTRAL/HP ELEMENT METHODS FOR TURBOMACHINERY, ASME Turbo Expo: Turbomachinery Technical Conference and Exposition, Publisher: AMER SOC MECHANICAL ENGINEERS

CONFERENCE PAPER

Ghim M, Alpresa P, Yang S-W, Braakman ST, Gray SG, Sherwin SJ, van Reeuwijk M, Weinberg PDet al., 2017, Visualization of three pathways for macromolecule transport across cultured endothelium and their modification by flow, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, Vol: 313, Pages: H959-H973, ISSN: 0363-6135

JOURNAL ARTICLE

Serson D, Meneghini JR, Sherwin SJ, 2017, Direct numerical simulations of the flow around wings with spanwise waviness, JOURNAL OF FLUID MECHANICS, Vol: 826, Pages: 714-731, ISSN: 0022-1120

JOURNAL ARTICLE

Marcon J, Turner M, Moxey D, Sherwin SJ, Peiró Jet al., 2017, A variational approach to high-order r-adaptation

A variational framework, initially developed for high-order meshoptimisation, is being extended for r-adaptation. The method is based on theminimisation of a functional of the mesh deformation. To achieve adaptation,elements of the initial mesh are manipulated using metric tensors to obtaintarget elements. The nonlinear optimisation in turns adapts the finalhigh-order mesh to best fit the description of the target elements byminimising the element distortion. Encouraging preliminary results prove thatthe method behaves well and can be used in the future for more extensive workwhich shall include the use of error indicators from CFD simulations.

CONFERENCE PAPER

Xu H, Mughal SM, Gowree ER, Atkin CJ, Sherwin SJet al., 2017, Destabilisation and modification of Tollmien-Schlichting disturbances by a three-dimensional surface indentation, JOURNAL OF FLUID MECHANICS, Vol: 819, Pages: 592-620, ISSN: 0022-1120

JOURNAL ARTICLE

Mao X, Zaki TA, Sherwin SJ, Blackburn HMet al., 2017, Transition induced by linear and nonlinear perturbation growth in flow past a compressor blade, Journal of Fluid Mechanics, Vol: 820, Pages: 604-632, ISSN: 0022-1120

Flow past a NACA 65 blade at chord-based Reynolds number 138 500 is studied using stability analysis, generalized (spatially weighted) transient growth analysis and direct numerical simulations (DNS). The mechanisms of transition on various sections of the blade observed in previous work by Zaki et al. (J. Fluid Mech., vol. 665, 2010, pp. 57-98) are examined, with a focus on the pressure side around the leading edge. In this region, the linearly most energetic perturbation has spanwise wavenumber 40π (five boundary-layer thicknesses) and is tilted against the mean shear to take advantage of the Orr mechanism. In a DNS, the nonlinear development of this optimal perturbation induces Λ structures, which are further stretched to hairpin vortices before breaking down to turbulence. At higher spanwise wavenumber, e.g. 120π, a free-stream optimal perturbation is obtained upstream of the leading edge, in the form of streamwise vortices. During its nonlinear evolution, this optimal perturbation tilts the mean shear and generates spanwise periodic high- and low-speed streaks. Then through a nonlinear lift-up mechanism, the low-speed streaks are lifted above the high-speed ones. This layout of streaks generates a mean shear with two inflectional points and activates secondary instabilities, namely inner and outer instabilities previously reported in the literature.

JOURNAL ARTICLE

Xu H, Lombard J-EW, 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

JOURNAL ARTICLE

Burovskiy P, Grigoras P, Sherwin S, Luk Wet al., 2017, Efficient Assembly for High-Order Unstructured FEM Meshes (FPL 2015), ACM TRANSACTIONS ON RECONFIGURABLE TECHNOLOGY AND SYSTEMS, Vol: 10, ISSN: 1936-7406

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

Chooi KY, Comerford A, Sherwin SJ, Weinberg PDet al., 2017, Noradrenaline has opposing effects on the hydraulic conductance of arterial intima and media, JOURNAL OF BIOMECHANICS, Vol: 54, Pages: 4-10, ISSN: 0021-9290

JOURNAL ARTICLE

Cantwell C, Sherwin S, 2017, 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

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

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

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

Serbanovic-Canic J, de Luca A, Warboys C, Ferreira PF, Luong LA, Hsiao S, Gauci I, Mahmoud M, Feng S, Souilhol C, Bowden N, Ashton J-P, Walczak H, Firmin D, Krams R, Mason JC, Haskard DO, Sherwin S, Ridger V, Chico TJA, Evans PCet al., 2017, Zebrafish Model for Functional Screening of Flow-Responsive Genes, ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY, Vol: 37, Pages: 130-+, ISSN: 1079-5642

JOURNAL ARTICLE

Moura RC, Peiro J, Sherwin SJ, 2017, On the accuracy and robustness of implicit LES/under-resolved DNS approaches based on spectral element methods

We present a study on the suitability of under-resolved DNS (uDNS)-also called implicit LES (iLES)-approaches based on spectral element methods (SEM), with emphasis on high-order continuous and discontinuous Galerkin (i.e. CG and DG) schemes. Broadly speaking, these are model-free eddy-resolving approaches to turbulence which solve the governing equations in unfiltered form and rely on numerical stabilization techniques for small-scale regularization. Model problems in 1D, 2D and 3D are used in the assessment of solution quality and numerical stability. A rationale for the excellent potential of these methods for transitional and turbulent flows is offered on the basis of linear dispersion-diffusion analysis.

CONFERENCE PAPER

Serson D, Meneghini JR, Sherwin SJ, 2017, Extension of the Velocity-Correction Scheme to General Coordinate Systems, Pages: 331-342, ISSN: 1439-7358

© 2017, Springer International Publishing AG. The velocity-correction scheme is a time-integration method for the incompressible Navier-Stokes equations, and is a common choice in the context of spectral/hp methods. Although the spectral/hp discretization allows the representation of complex geometries, in some cases the use of a coordinate transformation is desirable, since it may lead to symmetries which allow a more efficient solution of the equations. One example of this occurs when the transformed geometry has a homogeneous direction, in which case a Fourier expansion can be applied in this direction, reducing the computational cost. In this paper, we revisit two recently proposed forms of extending the velocity-correction scheme to general coordinate systems, the first treating the mapping terms explicitly and the second treating them semi-implicitly. We then present some numerical examples illustrating the properties and applicability of these methods, including new tests focusing on the time-accuracy of these schemes.

CONFERENCE PAPER

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