Application of PMB2D to Axisymmetric Flows. Department of Aerospace Engineering report 9812

This report describes how the two-dimensional planar flow solver PMB2D has been modified for axisymmetric flows. The equations describing axisymmetric flows are derived. The issue of conservation is discussed. The modified linear system arising at each implicit time step is detailed. Finally, results for inviscid, laminar and turbulent flow test cases are presented

Fast and Accurate Unfactored Two-Dimensional Turbulent Flow Simulation. G.U. Aero Report 9326

The approximate factorisation-conjugate gradient squared (AF-CGS) method has been successfully demonstrated for unsteady turbulent flows. In the present paper the method is adapted to obtain rapid convergence for steady flows. Modifications to the original method are described and test results are given for a laminar subsonic flow and two turbulent supersonic flows including the well studied AGARD RAE2822 case 9

Towards Automatic Multiblock Topology Generation. G.U. Aero Report 9826

The need for automation of the multiblock grid generation process is discussed. A new approach to automatically process a multiblock topology in order to prepare it for the grid generation process is described. The method is based on a cost function which attempts to model the objectives of the skilled grid generation software user who at present performs the task of block positioning and shaping in an interactive manner. A number of test cases are examined. It is also suggested that an existing unstructured mesh generation method could be adopted as an initial topology generation tool. Further work towards creating a fully automatic grid generation tool and extension into three dimensions are discussed briefly

Numerical Simulation of Steady Supersonic and Hypersonic Flows over Simple Bodies of Revolution. Aero Report 9902

This paper reports on numerical results for supersonic and hypersonic steady flows over axisymmetric blunt bodies. Two-dimensional compressible Navier- Stokes equations are solved using a high- resolution upwind Roe’s scheme. A modification to the boundary conditions and the implementation of Harten’s entropy fix is proposed to improve the robustness of the code, which is then tested on an axisymmetric spike, cone and cylinder at freestream Mach numbers of 2.21, 6.00 and 30.00

Numerical Simulation of High-Speed Unsteady Flows over Axisymmetric Spiked Bodies. Aero Report 9903

The present paper reports some preliminary numerical results for the supersonic/hypersonic unsteady flow over a family of spiked blunt bodies. Axisymmetric compressible Navier-Stokes equations are solved using a high- resolution unfactored implicit upwind Roe’s scheme and a time-accurate pseudo-time method is employed for advancing in time. Unsteady flow arising at Mach 2.21 and Mach 6.00 around the spiked 50°, 70° cone and cylinder are simulated and the computational results are compared with measurements. The study on these simple shapes for which experimental results are available provides a demonstration that such unsteady flows can be predicted reasonably well and provides confidence that more complex flows such as intake ’’buzz” and high Reynolds’ number ablation can be tackled

Far-field Boundary Conditions for Solutions to the Navier-Stokes Equations. Aerospace Engineering Departmental report no. 9324

The effect of reducing the extent of the computational domain for transonic lifting flow over an aerofoil in an unbounded domain is examined. A correction to the far field boundary conditions is developed based on a far field expansion of the linearized small-disturbance equation. Improved accuracy is demonstrated on smaller computational domains

Unfactored Multiblock Methods: Part I - Initial Method Development. G.U. Aero Report 9511

The use of implicit multiblock methods is discussed and an unfactored method based on a conjugate gradient type solution is described. Preconditioners appropriate to multiblock are considered along with future extensions to parallel computing

Shock Reflection Hysteresis in an Underexpanded Jet: a CFD Study. Department of Aerospace Engineering Report no. 9808

Shock reflection hysteresis in a low density, axisymmetric underexpanded air jet is examined using a Navier-Stokes flow solver. Jets of this type are found in a number of applications e.g. rocket exhausts. The existence of a dual solution domain where either regular or Mach reflection may occur within the complex plume structure is predicted. This is in agreement with experiment where the same phenomenon has been observed for a nitrogen jet. The results of the computational study are used to examine the structure of the plume, and are compared with experimental data where available. The plume structure is complex, involving the interaction of several flow features, making this a demanding problem. A quasi-steady approach is employed in order to calculate the entire hysteresis loop. Included in this report is a review of the two dimensional shock reflection hysteresis problem. Some recommendations are made for further study of this type of flow

Solution of the Euler Unsteady Equations Using Deforming Grids. G.U. Aero Report 9704.

No abstract available

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