Publications
138 results found
Tarnawski M, McLean M, Caro CG, et al., 1998, Effect of nicotine transdermal patch on femoral artery wavespeed in healthy human subjects measured by MRI, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 506P, Pages: 16P-16P, ISSN: 0022-3751
- Author Web Link
- Cite
- Citations: 2
Doorly DJ, Peiro J, 1998, Distributed evolutionary computational methods forb multiobjective and multidisciplinary optimization, Pages: 544-552
This paper1 describes evolutionary search procedures and their application to multiobjective and multidisciplinary optimization problems in aeronautical design. Genetic algorithms (GAs) have now been applied to many different fields, and have proven to be relatively robust means to search for optimal solutions. The search procedure adopted here is based on the distributed genetic algorithm (DGA), which has previously been found to perform substantially better than the conventional single population GA in many problems. As well as offering higher search efficiency, the DGA also offers further computational efficiency through parallel implementation. In the DGA, the population of trial solutions is split into semi-isolated sub-populations or 'demes'. The use of an agent to supervise the operation of the DGA, and some forms in which it may be implemented are outlined. Evolutionary learning techniques and competitive agent strategies are also discussed. Applications to multipoint and multiobjective problems such as airfoil shape optimization, and the design of adaptive surface airfoils are considered.
Sherwin SJ, Caro CG, Shah O, et al., 1998, 3-D Curvature of arterial bends and branches: Implications for arterial bypass grafting, Third World Congress of Biomechanics, Sapporo, Japan
Sherwin SJ, Caro CG, Watkins N, et al., 1998, Influence of non-planar geometry on flow separation, Physiological Society Meeting, Southampton
Doorly DJ, Peiró J, 1998, Supervised Parallel Genetic Algorithms in Aerodynamic Optimisation, Artificial Neural Nets and Genetic Algorithms, Publisher: Springer Vienna, Pages: 229-233, ISBN: 9783211830871
Peiro J, Shah O, Doorly DJ, et al., 1998, Unstructured viscous mesh generation for haemodynamic flow simulation using high-order spectral elements, London, Proc. 6th International Conf. on Numerical Grid Generation in Computational Fluid Simulation, London, 6-9 July 1998, Publisher: University of Greenwich, Pages: 475-466
Sherwin SJ, Shah O, Doorly DJ, et al., 1997, Visualization and computational study of flow at model planar and non-planar end-to-side arterial bypass grafts., JOURNAL OF PHYSIOLOGY-LONDON, Vol: 504P, Pages: P44-P44, ISSN: 0022-3751
- Author Web Link
- Cite
- Citations: 5
Doorly DJ, Peiró J, 1997, Supervised parallel genetic algorithms in aerodynamic optimisation, Pages: 210-216
The use of an agent, or multiple agents to supervise the operation of a parallel distributed genetic algorithm (GA) is outlined in this paper. The distributed genetic algorithm (DGA) is first described, and the advantages of this approach over the sequential genetic algorithm are briefly considered. A commonly experienced difficulty in the application of genetic algorithms is the maintenance of genetic diversity in the gene pool and the avoidance of premature convergence. The DGA, by subdividing the population into semi-isolated subpopulations or ‘demes’ is found to offer substantially improved performance over that obtained with the single population GA for the optimisation problems considered, in agreement with experience from other problem areas. Further advantage may however be gained by using an agent to direct the operation of the DGA, either globally on the set of sub-populations, or locally, on individuals. Results are given for aerodynamic optimisation problems, with and without agent supervision of the DGA. Finally some different forms of agent and their implementation are briefly outlined, illustrating the potential for the use of agent supervision.
Dodia BT, Doorly DJ, Smith FT, 1997, Computational modelling of unsteady boundary layer processes
The interaction of a vortex with a surface boundary layer is a problem with widespread application in aerodynamics. The unsteady boundary layer flow induced by a vortex above a plane surface eventually breaks down and a strong outward eruption of the boundary layer occurs. The current state of theoretical modelling of the flow is briefly reviewed in this paper, along with the role of computational studies. A vortex computational procedure is described, and results from Navier Stokes computations for a model problem are discussed in the context of the theoretical work.
Doorly DJ, Ljungdahl M, 1997, Computational simulation of magnetic resonance imaging techniques for velocity field measurements
A procedure to simulate the measurement of flow velocity components using magnetic resonance imaging (MRI) techniques is described. This procedure combines a numerical solution of the (Bloch) equations for flowing spins, with a CFD solution for the velocity field. The solution of the Block equations, (based on a hybrid Eulerian-Lagrangian particle-in-cell approach), is applied to test problems in 1,2 and 3D, and is shown to be stable and accurate. The simulation is used to investigate some effects of flowing spins on slice selection and image distortion which can affect flow measurements made by MRI. The algorithm is also well suited to parallel implementation on a workstation network.
Thiriet M, Cybulski G, Darrow RD, et al., 1997, Contribution and limitations of the magnetic resonance velocimetry in biomechanics. Measurements in a plane symmetrical bifurcation, Journal de Physique Iii, Vol: 7, Pages: 771-787
Sherwin SJ, Doorly DJ, Piero J, et al., 1997, Helix and model graft flows: MRI measurement and CFD simulations, ASME Paper FEDSM97-3423 ASME FED Meeting, June 22-26, Vancouver Canada
Sherwin SJ, Doorly DJ, Shah O, et al., 1997, Helical flow patterns in vessels, IX International Workshop on Magnetic Resonance Angiography, Valencia, Spain, 8-11, October 1997
Sherwin SJ, Shah O, Doorly DJ, et al., 1997, Visualisation and computational study of flow at model planar and non-planar end-to-side arterial bypass grafts, Physiological Abstract presented at Marine Biological Association meeting, Plymouth
Caro CG, Doorly DJ, Tarnawski M, et al., 1996, Effect of spatial variation of early systolic acceleration and accuracy of determination of late diastolic velocity on local arterial wavespeed measured by MRI in smokers and non-smokers, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 497P, Pages: P69-P70, ISSN: 0022-3751
Doorly DJ, Peiró J, Oesterle JP, 1996, Optimisation of aerodynamic and coupled aerodynamic-structural design using parallel genetic algorithms, Pages: 401-409
This paper describes a parallel genetic algorithm (GA) which is linked to aerodynamic and structural analysis for multidisciplinary optimisation of wings. The method has been applied to 2D aerodynamic section design, to the aerodynamic optimisation of wings and to combined aerodynamic and structural optimisation. The parallel genetic algorithm commences with the subdivision of the entire population of trial solutions into semi-isolated sub-populations, (so-called ‘demes’). The paper describes a model in which one or more demes may be mapped to a given processor; each processor concurrently executes the CFD and structural analysis for its deme(s). The algorithm is applied to various test problems; it is shown that this form of GA implementation provides advantages both in terms of search efficiency, and for parallel implementation.
Caro CG, Doorly DJ, Tarnawski M, et al., 1996, Non-planar curvature and branching of arteries and non-planar- type flow, Proceedings of the Royal Society of London Series A- Mathematical Physical and Engineering Sciences, Vol: 452, Pages: 185-197
LONG Q, DOORLY DJ, TARNAWSKI M, et al., 1995, VELOCITY DISTRIBUTION IN NONPLANAR CURVED PHANTOM MEASURED BY MRI, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 485P, Pages: P6-P6, ISSN: 0022-3751
Caro CG, Parker KH, Doorly DJ, 1995, Essentials of blood flow, Perfusion, Vol: 10, Pages: 131-134
Caro CG, Doorly DJ, Tarnawski M, et al., 1995, Non-planar geometry and non-planar-type flow at sites of arterial curvature and branching: Implications for arterial biology and disease, 2nd World Congress of Biomechanics, Publisher: PLENUM PRESS DIV PLENUM PUBLISHING CORP, Pages: 69-81
- Author Web Link
- Cite
- Citations: 2
Caro CG, Parker KH, Doorly DJ, 1995, Essentials of blood flow, Perfusion, Vol: 10, Pages: 131-134
Sun XD, Allwright JC, Graham JMR, et al., 1994, A nonlinear inverse-dynamics flight control system, IMA Journal of Mathematical Control and Information, Vol: 11, Pages: 155-167, ISSN: 0265-0754
The theme of this paper is the use of differential-geometrical control and its application, through the nonlinear inverse-dynamics (NID) methodology, to a nonlinear flight control system. We present a way for generating a generic control model for a promising control device-the spoiler-from experimental data, and for combining the nonlinear spoiler model with nonlinear aircraft dynamics. A new design procedure concerning the use of the NID control techniques is developed and utilized for the design of a nonlinear inverse-dynamics flight control system with various functional control modes. Simulation results for aircraft manoeuvres are presented, demonstrating the success of the design procedure and of the control effectiveness of spoilers for the enhancement of aircraft manoeuvring and, in particular, for alleviation of the effects of microbursts. © 1994 Oxford University Press.
JOHNSON MJ, CARO CG, SCOTT KT, et al., 1994, INDICATOR DISPERSION IN PLANAR AND NONPLANAR ARTERY MODELS, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 475P, Pages: P11-P12, ISSN: 0022-3751
- Author Web Link
- Cite
- Citations: 1
CARE CG, DOORLY DJ, TARNAWSKI M, et al., 1994, NONPLANAR CURVATURE AND BRANCHING OF ARTERIES, JOURNAL OF PHYSIOLOGY-LONDON, Vol: 475P, Pages: P60-P60, ISSN: 0022-3751
Doorly DJ, Liu CH, 1994, Application of a 3-D vortex particle in cell computational method to free and wall bounded shear flows, Pages: 163-172
A vortex particle-in-cell computational method for computing three dimensional viscous flows is presented. The method is applied to problems where an unsteady boundary layer develops under the impact of an external disturbance, such as a vortex dipole, or vortex ring, and comparison is made with the experimental literature. The results show the induced boundary layer greatly alters the interaction from the inviscid case, with vorticity from partial ejection of the induced boundary layer interacting with the primary, impinging vorticity. For an oblique ring impact, the interaction is shown to be highly asymmetric. The relation of these cases to vortex-wall interactions, with a pre-existing wall shear flow is discussed, and the method applied to the development of a vortical disturbance within a boundary layer.
Doorly DJ, Pesmajoglou S, 1994, Computations of cylinder wake flows using a vorticity-velocity particle-in-cell approach
This paper describes the application of a hybrid Lagrangian/Eulerian vortex particle-in-cell method for computing viscous flows, to the problem of unsteady flow past a circular cylinder. Particularly in oscillatory flows, an accurate representation of the cylinder wake is required, which poses difficulties for standard finite difference and finite element techniques. Previous vortex particle-in-cell formulations have usually employed a streamfunction-vorticity approach, which restricts application to two dimensional flows. In this paper we describe a velocity-vorticity formulation, suitable for application to 3D problems. Details of the solution procedure for the mesh computation are given, and results presented which verify that the formulation produces results for 2D flows which are in accord with those of the streamfunction-vorticity form.
TARNAWSKI M, CYBULSKI G, DOORLY D, et al., 1994, NONINVASIVE DETERMINATION OF LOCAL WAVESPEED AND DISTENSIBILITY OF THE FEMORAL-ARTERY BY COMB-EXCITED FOURIER VELOCITY-ENCODED MAGNETIC-RESONANCE-IMAGING - MEASUREMENTS ON ATHLETIC AND NONATHLETIC HUMAN-SUBJECTS, HEART AND VESSELS, Vol: 9, Pages: 194-201, ISSN: 0910-8327
- Author Web Link
- Cite
- Citations: 15
DOORLY DJ, HILKA M, 1993, 3D POINT VORTEX METHODS FOR PARALLEL FLOW COMPUTATIONS, 6TH CONF ON PARALLEL PROCESSING FOR SCIENTIFIC COMPUTING, Publisher: SIAM, Pages: 35-39
- Author Web Link
- Cite
- Citations: 1
DUMOULIN CL, TARNAWSKI M, DOORLY DJ, et al., 1993, MEASUREMENT OF PHYSIOLOGICAL FLOW PARAMETERS WITH MAGNETIC-RESONANCE, CONF ON PHYSIOLOGICAL IMAGING, SPECTROSCOPY, AND EARLY-DETECTION DIAGNOSTIC METHODS, Publisher: SPIE - INT SOC OPTICAL ENGINEERING, Pages: 50-68
Dumoulin CL, Doorly DJ, Caro CG, 1993, Quantitative Measurement of Velocity at Multiple Positions Using Comb Excitation and Fourier Velocity Encoding, Magnetic Resonance in Medicine, Vol: 29, Pages: 44-52
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.