Solution of the Euler Equations in Three Dimensional Complex Geometries Using a Fully Unfactored Method. Aerospace Engineering Report 9907

An unfactored implicit time-marching method for the solution of the three dimensional Euler equations on multiblock curvilinear grids is presented. For robustness the convective terms are discretised using an upwind TVD scheme. The linear system arising from each implicit time step is solved using a Krylov subspace method with preconditioning based on an block incomplete lower-upper (BELU(O)) factorisation. Results are shown for the ONERA M6 wing, a wing/body configuration and the NLR-F5 wing with launcher and missile. It was found that the simulation cost is relatively independent of the number of blocks used and their orientation. Comparison is made with experiment where available and good agreement is obtained

Approximate Jacobians for the Solution of the Euler and Navier-Stokes Equations. G.U. Aero Report 9705

This paper describes a method for efficiently solving the steady-state Euler and Navier-Stokes equations. Robustness is achieved through the use of an upwind TVD scheme for discretising the convective terms. The approximate solution is advanced in time implicitly and the linear system arising at each implicit step is solved using a Conjugate Gradient type method. The main emphasis of this paper is on the use of Jacobian matrices associated with a simpler spatial discretisation. This leads to better conditioned linear systems. The resulting method has lower memory and CPU-time requirements when compared with the one using exact Jacobians

Affordable High Powered Clustered Computing for Aerospace Simulation. G.U. Aero Report 9911

Motivated by a lack of sufficient local and national computing facilities for computational fluid dynamics simulations, the Affordable Systems Computing Unit (ASCU) was established to investigate low cost alternatives. The options considered have all involved cluster computing, a term which refers to the grouping of a number of components into a managed system capable of running both serial and parallel applications. Past work by the Unit has demonstrated the significant improvement in the efficiency of a Network of Workstations when management software is employed to scavenge spare cycles and schedule tasks, and has also investigated the use of a managed network for parallel CFD. The present work aims to extend this effort to a higher performance cluster based on commodity processors used for dedicated batch processing. The performance of the cluster has proved to be extremely cost effective, producing a 3 Gigaflops plus peak performance for less than 25K U.K. pounds sterling at current market prices. The experience gained on this system in terms of single node performance, message passing and parallel performance will be discussed. In particular, comparisons with the performance of other systems will be made. A large scale CFD simulation achieved using the new cluster will be presented to demonstrate the potential of commodity processor based parallel computers for aerodynamic simulation

Solution of the Navier-Stokes Equations in Three Dimensions Using a Fully Unfactored Method. Aerospace Engineering Report 9908

An unfactored implicit time-marching method for the solution of the three dimensional Navier-Stokes equations on multiblock curvilinear grids is presented. For robustness the convective terms are discretised using an upwind TVD scheme. A centred approach is followed for the discretisation of the viscous terms. The linear system arising from each implicit time step is solved using a Krylov subspace method with preconditioning based on an block incomplete lower-upper (BILU(O)) factorisation. Results are shown for the ONERA B1 ogive, for the ONERA M6 wing, the NLR-F5 clean wing and the ONERA B2 ogive, demonstrating good comparison with experiment except for some discrepancies in the last case due to turbulence modelling

An Overview of Knowledge Management Techniques for e-Recruitment

The number of potential job candidates and therefore, costs associated with their hiring, has grown significantly in the recent years. This is mainly due to both the complicated situation of the labour market and the increased geographical flexibility of employees. Some initiatives for making the e-Recruitment processes more efficient have notably improved the situation by developing automatic solutions. But there are still some challenges that remain open since traditional solutions do not consider semantic relations properly. This problem can be appropriately addressed by means of a sub discipline of knowledge management called semantic processing. Therefore, we overview the major techniques from this field that can play a key role in the design of a novel business model that is more attractive for job applicants and job providers

Approximate Jacobians for the Solution of the Euler and Navier-Stokes Equations. G.U. Aero Report 9705

This paper describes a method for efficiently solving the steady-state Euler and Navier-Stokes equations. Robustness is achieved through the use of an upwind TVD scheme for discretising the convective terms. The approximate solution is advanced in time implicitly and the linear system arising at each implicit step is solved using a Conjugate Gradient type method. The main emphasis of this paper is on the use of Jacobian matrices associated with a simpler spatial discretisation. This leads to better conditioned linear systems. The resulting method has lower memory and CPU-time requirements when compared with the one using exact Jacobians

Affordable High Powered Clustered Computing for Aerospace Simulation. G.U. Aero Report 9911

Motivated by a lack of sufficient local and national computing facilities for computational fluid dynamics simulations, the Affordable Systems Computing Unit (ASCU) was established to investigate low cost alternatives. The options considered have all involved cluster computing, a term which refers to the grouping of a number of components into a managed system capable of running both serial and parallel applications. Past work by the Unit has demonstrated the significant improvement in the efficiency of a Network of Workstations when management software is employed to scavenge spare cycles and schedule tasks, and has also investigated the use of a managed network for parallel CFD. The present work aims to extend this effort to a higher performance cluster based on commodity processors used for dedicated batch processing. The performance of the cluster has proved to be extremely cost effective, producing a 3 Gigaflops plus peak performance for less than 25K U.K. pounds sterling at current market prices. The experience gained on this system in terms of single node performance, message passing and parallel performance will be discussed. In particular, comparisons with the performance of other systems will be made. A large scale CFD simulation achieved using the new cluster will be presented to demonstrate the potential of commodity processor based parallel computers for aerodynamic simulation

Computational fluid dynamics analysis of multi-element, high-lift aerofoil sections at transonic manoeuvre conditions

The application of a previously-developed computational method to the prediction of high-lift performance for multi-element aerofoil sections operating at transonic flow conditions is described. The flows are computed by solving the Reynolds-averaged Navier-Stokes equations, using a full differential Reynolds-stress turbulence model to evaluate the various Reynolds-stress components appearing in the governing mean-flow equations. Algebraic wall functions are used to bridge the molecular-viscosity dominated region immediately adjacent to the aerofoil surfaces. An unstructured-grid based Computational Fluid Dynamics methodology is used to deal with the geometric complexity of the multi-element aerofoil configurations. Initial results are presented for the viscous, transonic flow development around the SKF 1.1 supercritical aerofoil section, equipped with either a trailing-edge flap or a leading-edge slat. Predicted surface pressure distributions generally compare well with experimental data for the two high-lift aerofoil geometries considered, at a free-stream Mach number of 0.6 and over a range of incidence angles. There are some discrepancies in the regions immediately downstream of shock wave/boundary layer interactions, possibly resulting from the use of wall-function boundary conditions in the computations. Predicted Mach number contours indicate the complexity of the transonic flow fields for high-lift configurations, with the slat wake passing through an extensive supersonic-flow region, terminated by a normal shock wave, on the main aerofoil upper surface, for exampl