Publications
401 results found
KELee, KH Parker, CG Caro, et al., 2007, The spectral/hp element modelling of steady flow in non-planar double bends, Int. J. Num. Meth. Fluids, Vol: in press
Alastruey J, Parker KH, Peiró J, et al., 2006, Can the modified Allen's test always detect sufficient collateral flow in the hand? A computational study., Comput Methods Biomech Biomed Engin, Vol: 9, Pages: 353-361, ISSN: 1025-5842
Blood flow in the largest arteries of the arm up to the digital arteries is numerically modelled using the one-dimensional equations of pressure and flow wave propagation in compliant vessels. The model can be applied to different anatomies of arterial networks and can simulate compression of arteries, these allowing us to simulate the modified Allen's test (MAT) and to assess its suitability for the detection of sufficient collateral flow in the hand if radial blood supply is interrupted. The test measures blood flow in the superficial palmar arch before and during compression of the radial artery. The absence of reversal flow in the palmar arch with the compression indicates insufficient collateral flow and is referred to as a positive MAT. This study shows that small calibres of the superficial palmar arch and insufficient compression of the radial artery can lead to false-positive results. Measurement of the drop in digital systolic pressures with compression of the radial artery has proved to be a more sensitive test to predict the presence of sufficient ulnar collateral flow in networks with small calibres of the superficial palmar arch. However, this study also shows that digital pressure measurements can fail in detecting enough collateral flow if the radial artery is insufficiently compressed.
Eskilsson C, Sherwin SJ, Bergdahl L, 2006, An unstructured spectral/<i>hp</i> element model for enhanced Boussinesq-type equations, COASTAL ENGINEERING, Vol: 53, Pages: 947-963, ISSN: 0378-3839
- Author Web Link
- Cite
- Citations: 18
Kirby RM, Sherwin SJ, 2006, Aliasing errors due to quadratic nonlinearities on triangular spectral <i>/hp</i> element discretisations, JOURNAL OF ENGINEERING MATHEMATICS, Vol: 56, Pages: 273-288, ISSN: 0022-0833
- Author Web Link
- Open Access Link
- Cite
- Citations: 17
Sherwin SJ, Kirby RM, Peiró J, et al., 2006, On 2D elliptic discontinuous Galerkin methods, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Vol: 65, Pages: 752-784, ISSN: 0029-5981
- Author Web Link
- Open Access Link
- Cite
- Citations: 31
Abdessemed N, Sherwin SJ, Theofilis V, 2006, Linear stability of the flow past a low pressure turbine blade, Pages: 1496-1510
The present work is concerned with linear BiGlobal instabilities of flow in a cascade of Low-pressure turbine (LPT) blades. In particular the three-dimensional instability of two-dimensional time-periodic basic states past a T106/3 blade is investigated using Floquet theory and a high-order spectral/hp-element scheme, used for both the basic flow and the instability calculations. The two-dimensional bifurcation of steady to time-periodic flow has been identified in the framework of earlier work on the present project.1 The present Floquet analysis shows that the time-periodic flow becomes three-dlmensionally unstable soon after the two dimensional transition. Two modes of significance have been identified, associated to the separation bubble and the wake of the basic state. Three-dimensional DNS initialized on the identified Floquet eigenmodes at low amplitudes confirms the results of linear stability analysis. Besides the completion of the eigenvalue-based analyses, first-ever transient-growth results of an essentially nonparallel flow have been obtained. In particular, the pseudospectrum of the flow under consideration has been identified and new mechanisms have been revealed, demonstrating the potential for three-dimensional transition as consequence of transient growth.
Broadhurst M, 2006, Vortex Stability and Breakdown: Direct Numerical Simulation and Stability Analysis using BiGlobal and Parabolised Formulations
This thesis concerns the application and implementation of recently developed stability techniques to the understanding of vortex stability and breakdown. The instability anal- ysis of vortical flows was originally motivated by a need to understand the breakdown of aircraft wake vortices and the physics of the vortex breakdown phenomenon. A more recent application is the stability analysis of the vortex wake developed from a Formula 1 front wing. Typically, the model problem when considering vortex dominated flows is the Batch- elor trailing vortex. The results of a BiGlobal linear stability analysis of a Batchelor vortex show that there are many unstable helical perturbation modes covering a wide range of axial wavenumbers. Direct numerical simulation of a corresponding unstable helical distur- bance developing on an axially periodic vortex demonstrates a non-linear energy transfer mechanism responsible for a loss of energy in the mean flow. Relaxing the assumption of periodicity allows axial gradients to develop, and leads to an abrupt drop in axial velocity indicative of vortex breakdown. Direct numerical simulations of a vortex in external pres- sure gradients also suggests that axial pressure gradients significantly influence the onset of vortex breakdown. With a BiGlobal stability analysis assuming axial homogeneity and neglecting streamwise gradients, this motivates the need for an analysis technique that can account for both velocity and pressure gradients. One such technique is the parabolised stability equations, and the current research has successfully implemented this technique and demonstrated its validity by comparing the results with direct numerical simulation.
Kirby RM, Sherwin SJ, 2006, Stabilisation of spectral/<i>hp</i> element methods through spectral vanishing viscosity:: Application to fluid mechanics modelling, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, Vol: 195, Pages: 3128-3144, ISSN: 0045-7825
- Author Web Link
- Open Access Link
- Cite
- Citations: 65
Broadhurst MS, Theofilis V, Sherwin SJ, 2006, Spectral element stability analysis of vortical flows, 6th IUTAM Symposium on Laminar-Turbulent Transition, 13 - 17 December 2004, Bangalore, INDIA, Publisher: Springer, Pages: 153-158
Sherwin SJ, Eskilsson C, 2006, Spectral/hp discontinuous Galerkin methods for modelling 2D Boussinesq equations, Journal of Computational Physics, Vol: 212, Pages: 566-589, ISSN: 0021-9991
Gambaruto AM, Radaelli A, Doorly DJ, et al., 2005, Sensitivity study on by-pass graft reconstruction with emphasis on flow solutions, Pages: 832-833
Giordana S, Sherwin SJ, Peiró J, et al., 2005, Local and global geometric influence on steady flow in distal anastomoses of peripheral bypass grafts, JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME, Vol: 127, Pages: 1087-1098, ISSN: 0148-0731
- Author Web Link
- Cite
- Citations: 39
Xiu D, Sherwin SJ, Dong S, et al., 2005, Strong and auxiliary forms of the semi-Lagrangian method for incompressible flows, Journal of Scientific Computing, Vol: 25, Pages: 323-346, ISSN: 0885-7474
We present a review of the semi-Lagrangian method for advection-diffusion and incompressible Navier-Stokes equations discretized with high-order methods. In particular, we compare the strong form where the departure points are computed directly via backwards integration with the auxiliary form where an auxiliary advection equation is solved instead; the latter is also referred to as Operator Integration Factor Splitting (OIFS) scheme. For intermediate size of time steps the auxiliary form is preferrable but for large time steps only the strong form is stable.
Xiu D, Sherwin SJ, Dong S, et al., 2005, Strong and auxiliary forms of the semi-Lagrangian method for incompressible flows, Journal of Scientific Computing, Vol: 25, Pages: 323-346, ISSN: 0885-7474
Sherwin SJ, Blackburn HM, 2005, Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows, JOURNAL OF FLUID MECHANICS, Vol: 533, Pages: 297-327, ISSN: 0022-1120
- Author Web Link
- Open Access Link
- Cite
- Citations: 162
Pitt RE, Sherwin SJ, Theofilis V, 2005, BiGlobal stability analysis of steady flow in constricted channel geometries, 8th ICFD Conference on Numerical Methods for Fluid Dynamics, Publisher: WILEY, Pages: 1229-1235, ISSN: 0271-2091
- Author Web Link
- Open Access Link
- Cite
- Citations: 8
Miliou A, Mortazavi I, Sherwin S, 2005, Cut-off analysis of coherent vortical structure identification in a three-dimensional external flow, COMPTES RENDUS MECANIQUE, Vol: 333, Pages: 211-217, ISSN: 1631-0721
- Author Web Link
- Open Access Link
- Cite
- Citations: 3
Giordana S, Sherwin SJ, Peiró J, et al., 2005, Automated classification of peripheral distal by-pass geometries reconstructed from medical data, JOURNAL OF BIOMECHANICS, Vol: 38, Pages: 47-62, ISSN: 0021-9290
- Author Web Link
- Open Access Link
- Cite
- Citations: 24
Eskilsson C, Sherwin SJ, 2005, Discontinuous galerkin spectral/<i>hp</i> element modelling of dispersive shallow water systems, JOURNAL OF SCIENTIFIC COMPUTING, Vol: 22-3, Pages: 269-288, ISSN: 0885-7474
- Author Web Link
- Open Access Link
- Cite
- Citations: 29
Sherwin SJ, Peiro J, 2005, Finite difference, finite element and finite volume methods for partial differential equations, Handbook of materials modeling, Editors: Yip, Yip, Berlin, Publisher: Springer, Pages: 1-30, ISBN: 9781402032875
Alastruey J, Parker KH, Peiro J, et al., 2005, A one-dimensional simulation of the human conduit arteries compared to experimental data, ASME Summer Biongineering Conference, abstract 0328683, Vail, CO, USA
Karniadakis G, Sherwin S, 2005, Spectral/hp element methods for computational fluid dynamics, Oxford, Publisher: Oxford University Press, ISBN: 9780198528692
Abdessemed N, Sherwin SJ, Theofilis V, 2004, On unstable 2d basic states in low pressure turbine flows at moderate reynolds numbers
Results are presented of BiGlobal stability analysis of incompressible flow over a row of T-106/300 Low Pressure Turbine blades. In particular the two- and three-dimensional stability of a two-dimensional steady state is investigated for Reynolds numbers below 915. Both structured and unstructured meshes have been used at different degrees of refinement, while variations of the polynomial order of the numerical methods in either approach have ensured numerical convergence. The analysis shows that the transition from steady to periodic flow takes place at a Reynolds number of Rec = 905 ± 10. The flow remains linearly stable to three-dimensional disturbances below Rec. The leading eigenvalues of three-dimensional BiGlobal eigenmodes of the LPT flow have been obtained in a range of Reynolds and spanwise wavenumber parameters. The two most interesting eigenmodes have been found to be related with the wake of the blade and the separated flow in the trailing-edge region on the suction side of the blade. © 2004 by the American Institute of Aeronautics and Astronautics, Inc.
Blackburn HM, Sherwin SJ, 2004, Formulation of a Galerkin spectral element-Fourier method for three-dimensional incompressible flows in cylindrical geometries, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 197, Pages: 759-778, ISSN: 0021-9991
- Author Web Link
- Open Access Link
- Cite
- Citations: 158
Eskilsson C, Sherwin SJ, 2004, A triangular spectral/<i>hp</i> discontinuous Galerkin method for modelling 2D shallow water equations, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Vol: 45, Pages: 605-623, ISSN: 0271-2091
- Author Web Link
- Open Access Link
- Cite
- Citations: 68
Robertson I, Sherwin SJ, Graham JMR, 2004, Comparison of wall boundary conditions for numerical viscous free surface flow simulation, JOURNAL OF FLUIDS AND STRUCTURES, Vol: 19, Pages: 525-542, ISSN: 0889-9746
- Author Web Link
- Open Access Link
- Cite
- Citations: 28
Abdessemed N, Sherwin SJ, Theofilis V, 2004, On unstable 2d basic states in low pressure turbine flows at moderate reynolds numbers
Results are presented of BiGlobal stability analysis of incompressible flow over a row of T-106/300 Low Pressure Turbine blades. In particular the two- and three-dimensional stability of a two-dimensional steady state is investigated for Reynolds numbers below 915. Both structured and unstructured meshes have been used at different degrees of refinement, while variations of the polynomial order of the numerical methods in either approach have ensured numerical convergence. The analysis shows that the transition from steady to periodic flow takes place at a Reynolds number of Rec = 905 ± 10. The flow remains linearly stable to three-dimensional disturbances below Rec. The leading eigenvalues of three-dimensional BiGlobal eigenmodes of the LPT flow have been obtained in a range of Reynolds and spanwise wavenumber parameters. The two most interesting eigenmodes have been found to be related with the wake of the blade and the separated flow in the trailing-edge region on the suction side of the blade. © 2004 by the American Institute of Aeronautics and Astronautics, Inc.
McKeon BJ, Lambert S, Sherwin SJ, et al., 2004, Active dimples for flow control, Barcelona, Advances in turbulence X, Publisher: CIMNE, Pages: 581-584
Giordana S, Radaelli A, Peiro J, et al., 2004, Geometry reconstruction and CFD modeling of arterial flows, Proceedings ICFD conference on numerical methods for fluid dynamics, Oxford, England, 29 March - 1 April 2004
varghese S, Frankel S, Pitt R, et al., 2004, Numerical simulation of pulsatile flow through stenotic vessels, Turbulence and shear flow phenomena, Sendai, Japan, 25 - 27 June 2003
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.