Spencer J. Sherwin

Spencer J. Sherwin
Imperial College London | Imperial · Department of Aeronautics

M.S.E, PhD

About

411
Publications
106,833
Reads
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14,342
Citations
Citations since 2016
117 Research Items
8173 Citations
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201620172018201920202021202202004006008001,0001,200
201620172018201920202021202202004006008001,0001,200
201620172018201920202021202202004006008001,0001,200
Introduction

Publications

Publications (411)
Conference Paper
In this work, a DNS – Machine Learning (ML) framework is developed for low-pressure turbine (LPT) profiles to inform turbulence closures in Reynolds-Averaged Navier-Stokes (RANS) calculations. This is done by training the coeffcients of Explicit Algebraic Reynolds Stress Models (EARSM) with shallow artificial neural networks (ANN) as a function of...
Preprint
Full-text available
Due to the proprietary nature of modern motorsport and Formula 1, current scientific literature lacks relevant studies and benchmarks that can be used to test and validate new methods. Due to the release of a free geometry - the Imperial Front Wing - we present a computational study of a multi-element aerofoil at a ride height of 0.36 h/c and a Rey...
Article
Nektar++ is a spectral/hp element open-source framework written in C++ for the construction of classical low-order h-type as well as higher-order p-type finite element solvers. It seeks to overcome the implementation challenges of the complex data structures associated with high-order finite element methods; hence, providing an efficient, flexible...
Article
Full-text available
In recent years, different dispersion-diffusion (eigen)analyses have been developed and used to assess various spectral element methods (SEMs) with regards to accuracy and stability, both of which are very important aspects for under-resolved computations of transitional and turbulent flows. Not surprisingly, eigenanalysis has been used recurrently...
Article
In the numerical discretization of partial differential equations (PDEs) with moving frames on curved surfaces, the discretization error does not converge for a high p≥5. Moreover, the conservation error remains significant even in a refined mesh and does not converge as the polynomial order p increases. We postulate that the inaccurate location of...
Article
Full-text available
The patchy distribution of atherosclerosis within the arterial system is consistent with a controlling influence of hemodynamic wall shear stress (WSS). Patterns of low, oscillatory and transverse WSS have been invoked to explain the distribution of disease in the aorta. Disease of coronary arteries has greater clinical importance but blood flow in...
Conference Paper
Full-text available
The two-dimensional to three-dimensional transition of a flow past a plunging NACA 0012 airfoil at a Reynolds number of Re = 400, based on the chord length c, and an angle of attack of 15 degrees was investigated using global linear stability analysis and spanwise-homogeneous direct numerical simulation (DNS). The peak-to-peak plunging amplitude wa...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-4032.vid We introduce an open-source and unified framework for transition analysis for laminar boundary layer natural transition at transonic conditions and over complex geometries, where surface irregularities may be present. Different computational tools are integrated in the framework, and...
Conference Paper
Within the literature, there are limited high-order results concerning large Reynolds number flows under the influence of strong adverse pressure gradients, mainly due to the computational expense involved. The main advantage in employing high-order methodologies over standard second-order finite-volume solvers, relates to their ability to increase...
Article
The vortex dynamics of leading-edge vortices on plunging high-aspect-ratio ( AR = 10) wings and airfoils were investigated by means of volumetric velocity measurements, numerical simulations and stability analysis to understand the deformation of the leading-edge vortex filament and spanwise instabilities. The vortex filaments on both the wing and...
Conference Paper
In this work a high-order spectral-h/p element solver is employed to efficiently but accurately resolve the flow field around the NACA0012 aerofoil. In particular, the conditions considered are a Reynolds number of 150000 and three angles of attack, namely 9◦, 10◦ and 12◦. This particular study aims at providing the necessary preliminary insight in...
Preprint
We introduce an open-source and unified framework for transition analysis for laminar boundary layer natural transition at transonic conditions and over complex geometries, where surface irregularities may be present. Different computational tools are integrated in the framework, and therefore overcomes the difficulties of two separate and usually...
Preprint
One approach to reduce the cost to simulate transitional compressible boundary layer flow is to adopt a near body reduced domain with boundary conditions enforced to be compatible with a computationally cheaper 3D RANS simulation. In such an approach it is desirable to enforce a consistent pressure distribution which is not typically the case when...
Article
Full-text available
A spectral/hp element methodology is utilised to investigate the SAE Notchback geometry with 20∘ backlight and 3∘ diffuser at Re=2.3×106. The study presented here considered two different mesh approaches: one focusing on classical h-type refinement with standard solution polynomial order (HFP3) and a second case considering relatively coarse mesh c...
Article
Full-text available
Reynolds-Averaged Navier–Stokes (RANS) methods continue to be the backbone of CFD-based design; however, the recent development of high-order unstructured solvers and meshing algorithms, combined with the lowering cost of HPC infrastructures, has the potential to allow for the introduction of high-fidelity simulations in the design loop, taking the...
Article
Emerging commercial and academic tools are regularly being applied to the design of road and race cars, but there currently are no well-established benchmark cases to study the aerodynamics of race car wings in ground effect. In this paper we propose a new test case, with a relatively complex geometry, supported by the availability of CAD model and...
Chapter
Full-text available
The destabilisation effects of forward and backward facing steps on cross-flow (CF) disturbances on an infinite swept wing is investigated. Stationary and travelling CF-wave instability modulations, as they convect over the abrupt surface features, are investigated computationally with step heights ranging from 18% to 53% of the boundary layer thic...
Article
One of the strengths of the discontinuous Galerkin (DG) method has been its balance between accuracy and robustness, which stems from DG’s intrinsic (upwind) dissipation being biased towards high frequencies/wavenumbers. This is particularly useful in high Reynolds-number flow simulations where limitations on mesh resolution typically lead to poten...
Article
Full-text available
Heart failure is treatable, but in the United Kingdom, the 1-, 5- and 10-year mortality rates are 24.1, 54.5 and 75.5%, respectively. The poor prognosis reflects, in part, the lack of specific, simple and affordable diagnostic techniques; the disease is often advanced by the time a diagnosis is made. Previous studies have demonstrated that certain...
Article
Effects of fluid dynamics on cells are often studied by growing the cells on the base of cylindrical wells or dishes that are swirled on the horizontal platform of an orbital shaker. The swirling culture medium applies a shear stress to the cells that varies in magnitude and directionality from the centre to the edge of the vessel. Computational fl...
Technical Report
Full-text available
In recent years, different dispersion-diffusion (eigen)analyses have been developed and used to assess various spectral element methods (SEMs) with regards to accuracy and stability, both of which are very important aspects for under-resolved computations of transitional and turbulent flows. Not surprisingly, eigenanalysis has been used recurrently...
Article
Full-text available
A balanced adaptive time-stepping strategy is implemented in an implicit discontinuous Galerkin solver to guarantee the temporal accuracy of unsteady simulations. A proper relation between the spatial, temporal and iterative errors generated within one time step is constructed. With an estimate of temporal and spatial error using an embedded Runge-...
Article
Full-text available
The spectral/hp element method [which is the hp-version finite element method, where h denotes the h-version finite element method and p denotes the p-version finite element method (or the spectral element method) with elementwise expansion based on (modified) orthogonal polynomials up to pth-order in each element] together with the regularized spe...
Article
Full-text available
We report on a high‐fidelity, spectral/hp element algorithm developed for the direct numerical simulation of thermal convection problems. We consider the incompressible Navier‐Stokes and advection‐diffusion equations coupled through a thermal body‐forcing term. The flow is driven by a prescribed flowrate forcing with explicit treatment of the nonli...
Article
The Ahmed body is one of the most studied 3D automotive bluff bodies and the variation of its slant angle of the rear upper surface generates different flow behaviours, similar to a standard road vehicles. In this study we extend the geometrical variation to evaluate the influence of a rear underbody diffuser which are commonly applied in high perf...
Conference Paper
An efficient computational method is presented based on the thick strip method for Large-Eddy simulation of flexible wings in stall. Fluid domain is break down into series of smaller 3D strips which one independently solved using implicit LES method. Force and moments are obtained from each strips and used to evolved the nonlinear dynamics of the s...
Article
The alignment of arterial endothelial cells (ECs) with the mean wall shear stress (WSS) vector is the prototypical example of their responsiveness to flow. However, evidence for this behaviour rests on experiments where many WSS metrics had the same orientation or where they were incompletely characterized. In the present study, we tested the pheno...
Article
Full-text available
We present an rp‐adaptation strategy for high‐fidelity simulation of compressible inviscid flows with shocks. The mesh resolution in regions of flow discontinuities is increased by using a variational optimiser to r‐adapt the mesh and cluster degrees of freedom there. In regions of smooth flow, we locally increase or decrease the local resolution t...
Article
Full-text available
Central blood pressure (cBP) is a highly prognostic cardiovascular (CV) risk factor whose accurate, invasive assessment is costly and carries risks to patients. We developed and assessed novel algorithms for estimating cBP from non-invasive aortic haemodynamic data and a peripheral BP measurement. These algorithms were created using three blood flo...
Preprint
Full-text available
We present a successful deployment of high-fidelity Large-Eddy Simulation (LES) technologies based on spectral/hp element methods to industrial flow problems, which are characterized by high Reynolds numbers and complex geometries. In particular, we describe the numerical methods, software development and steps that were required to perform the imp...
Article
Full-text available
Pressure–velocity-based analysis of arterial wave intensity gives clinically relevant information about the performance of the heart and vessels, but its utility is limited because accurate pressure measurements can only be obtained invasively. Diameter–velocity-based wave intensity can be obtained noninvasively using ultrasound; however, due to th...
Chapter
This study assesses the suitability of spectral/hp continuous Galerkin (CG) schemes [1] for model-free under-resolved simulations of a non-trivial turbulent boundary layer flow. We consider a model problem proposed by Spalart in [2] that features a rotating free-stream velocity and admits an asymptotic solution with significant crossflow effects. N...
Article
Full-text available
Nektar++ is an open-source framework that provides a flexible, high-performance and scalable platform for the development of solvers for partial differential equations using the high-order spectral/ element method. In particular, Nektar++ aims to overcome the complex implementation challenges that are often associated with high-order methods, there...
Article
Full-text available
At high Reynolds numbers the use of explicit in time compressible flow simulations with spectral/hp element discretization can become significantly limited by time step. To alleviate this limitation we extend the capability of the spectral/hp element open-source software framework, Nektar++, to include an implicit discontinuous Galerkin compressibl...
Technical Report
Full-text available
This research report contains the dispersion-diffusion analysis of the gradient-jump penalty (GJP) stabilisation strategy for CG, having in mind under-resolved simulations.
Preprint
Full-text available
At high Reynolds numbers, the use of explicit in time compressible flow simulations with spectral/$hp$ element discretization can become significantly limited by time step. To alleviate this limitation we extend the capability of the spectral/$hp$ element open-source software framework, Nektar++, to include an implicit discontinuous Galerkin compre...
Conference Paper
Full-text available
We describe an adaptive version of a method for generating valid naturally curved quadrilateral meshes. The method uses a guiding field, derived from the concept of a cross field, to create block decompositions of multiply connected two dimensional domains. The a priori curved quadrilateral blocks can be further split into a finer high-order mesh a...
Preprint
Full-text available
The Ahmed body is one of the most studied 3D bluff bodies used for automotive research and was first proposed by Ahmed in 1984. The variation of the slant angle of the rear upper surface on this body generates different flow behaviours, similar to a standard road vehicles. In this study we extend the geometrical variation to evaluate the influence...
Chapter
Full-text available
We present the first eigenanalysis of hybridisable discontinuous Galerkin (HDG) schemes for the advection-diffusion equation in one dimension. This study is also one of the first to include viscous diffusion effects in the eigenanalysis of discontinuous spectral element methods. The interplay between upwind dissipation and viscous diffusion is disc...
Book
Full-text available
This open access book features a selection of high-quality papers from the presentations at the International Conference on Spectral and High-Order Methods 2018, offering an overview of the depth and breadth of the activities within this important research area. The carefully reviewed papers provide a snapshot of the state of the art, while the ext...
Chapter
Full-text available
The Ahmed Body is one of the most widely studied bluff bodies used for automotive conceptual studies and Computational Fluid Dynamics (CFD) software validation. With the advances of the computational processing capacity and improvement in computing costs, high-fidelity turbulence models, such as Detached Eddies Simulation (DES) and Large Eddies Sim...
Article
We describe a high order technique to generate quadrilateral decompositions and meshes for complex two dimensional domains using spectral elements in a field guided procedure. Inspired by cross field methods, we never actually compute crosses. Instead, we compute a high order accurate guiding field using a continuous Galerkin (CG) or discontinuous...
Article
Full-text available
This study considers the spatial eigensolution analysis of spectral/hp continuous Galerkin (CG) schemes, complementing a recent work by Moura et al. (2016) [15] which addressed CG's temporal analysis. While the latter assumes periodic boundary conditions, the spatial approach presumes inflow/outflow type conditions and therefore provides insights f...
Preprint
Full-text available
We present an rp-adaptation strategy for the high-fidelity simulation of compressible inviscid flows with shocks. The mesh resolution in regions of flow discontinuities is increased by using a variational optimiser to r-adapt the mesh and cluster degrees of freedom there. In regions of smooth flow, we locally increase or decrease the local resoluti...
Preprint
Full-text available
Emerging commercial and academic tools are regularly being applied to the design of road and race cars, but there currently are no well-established benchmark cases to study the aerodynamics of race car wings in ground effect. In this paper we propose a new test case, with a relatively complex geometry, supported by the availability of CAD model and...
Chapter
Full-text available
We have performed direct numerical simulations of a transitional flow in a pipe for \(Re_m=2250\) when turbulence manifests in the form of fleshes (puffs). From experiments and simulations, \(Re_m \approx 2250\) has been estimated as a threshold when the average speeds of upstream and downstream fronts of a puff are identical (Song et al. in J Flui...
Preprint
Full-text available
When time-dependent partial differential equations (PDEs) are solved numerically in a domain with curved boundary or on a curved surface, mesh error and geometric approximation error caused by the inaccurate location of vertices and other interior grid points, respectively, could be the main source of the inaccuracy and instability of the numerical...
Preprint
Full-text available
We describe an adaptive version of a method for generating valid naturally curved quadrilateral meshes. The method uses a guiding field, derived from the concept of a cross field, to create block decompositions of multiply connected two dimensional domains. The a priori curved quadrilateral blocks can be further split into a finer high-order mesh a...
Conference Paper
The recent development and increasing integration of high performance computing, scale resolving CFD and high order unstructured methods offers a potential opportunity to deliver a simulation-based capability (i.e. virtual) for aerodynamic research, analysis and design of industrial relevant problems in the near future. In particular, the tendency...
Preprint
Full-text available
Nektar++ is an open-source framework that provides a flexible, performant and scalable platform for the development of solvers for partial differential equations using the high-order spectral/hp element method. In particular, Nektar++ aims to overcome the complex implementation challenges that are often associated with high-order methods, thereby a...
Article
Full-text available
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 e...
Conference Paper
Full-text available
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. Howe...