Walpot, Louis

A General Grid Generation Strategy for Complex Aerospace Geometries

Hauser J., Muylaert J., Spel M., Walpot L., Xia Y.

Published in 1999

In this paper we present a strategy for grid generation for complex geomentries based on the multiblock approach. On the block level the grid is completely unstructured and may be represented by a graph. Within a block a structured grid is generated to retain both the computantional efficiency and accuracy of the finite volume approach. In order to handle extreme degrees of geometrical complexity, an object-oriented topology generation approach has been devised implemented by the Topology Input Language (TIL) to manage these objects. To this end, the configuration to be gridded is subdivided into objects (like wing, fuselage, nacelle, pylon, engine etc. for an aircraft configuration) for which individual topologies are designed. These topologies are considered to be local topologies, since they represent only a part of the solution domain. The important feature is that objects can have internal topologies that have a rich structure that is not visible from the outside. The final grid topology is constructed by combining the topologies of all objects, using their visible topology only. Thus the level of complexity can be substantially reduced. Since there is a strict separation between topology and geomentry, a topology database can be built that is fully reusable. The strategy is demonstrated for a generic X-33 configuration with the linear aerospike engine and an annular aerospike propulsion system, modeling numerious design details to demonstrate the capability of the software to model most complex geometries with relative small input from the user.

Keywords: mesh strategy, structured multiblock grid, complex geometry

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Non Equilibrium Computational Analysis of Blunt-Cone Experiments Performed in the LENS and HEG Facilities

Muylaert J., Walpot L., Spel M., Tumino G., Steijl R.

Published in 1996

The paper focuses on the numerical rebuilding of high enthalpy flow characteristics on a 70 degree blunt cone with emphasis on the non-equilibrium expansion around the shoulder and shear layer re-attachment heating on the sting. The experiments were performed in the Large Energy National Shock Tube (LENS) at Calspan and in the piston driven shock tunnel at DLR Goettingen (HEG). The blunt cone model was instrumented with 40 coaxial thermocouples on the forebody and 65 thin film resistance gauges. A nozzel sensitivity study was performed for the HEG by varing chemical vibrational models as well as their couplings. Axisymmetric non-equilibrium Navier-Stokes computations have been performed with different chemical models such as Park and Dunn & Kang and a 1 degree of incidence 3D computation was performed comfirming that the flow at re-attachment is steady and transitions most likely to turbulence for the HEG case.

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