Nigel J. Taylor

A geometric comparison of aerofoil shape parameterisation methods

A comprehensive review of aerofoil shape parameterization methods that can be used for aerodynamic shape optimization is presented. Seven parameterization methods are considered for a range of desi...

Impact of Shape Parameterisation on Aerodynamic Optimisation of Benchmark Problem

This paper presents an investigation into the influence of shape parameterisation and dimensionality on the optimisation of a benchmark case described by the AIAA Aerodynamic Design Optimisation Discussion Group. This problem specifies the drag minimisation of a NACA0012 under inviscid flow conditions at M = 0.85 and α = 0 subject to the constraint that local thickness must only increase. The work presented here applies six different shape parameterisation schemes to this optimisation problem with between 4 and 40 design variables. The parameterisation methods used are: Bezier Surface FFD; B-Splines; CSTs; Hicks-Henne bump functions; a Radial Basis Function domain element method (RBF-DE) and a Singular Value Decomposition (SVD) method. The optimisation framework used consists of a gradient based SQP optimiser coupled with the SU2 adjoint Euler solver which enables the efficient calculation of the design variable gradients. Results for the all the parameterisation methods are presented with the best results for each method ranging between 25 and 56 drag counts from an initial value of 469. The optimal result was achieved with the B-Spline method with 16 design variables. A further validation of the results is then presented and the presence of hysteresis is explored.

A Multi-Level Subdivision Parameterisation Scheme for Aerodynamic Shape Optimisation

Subdivision curves are defined as the limit of a recursive application of a subdivision rule to an initial set of control points. This intrinsically provides a hierarchical set of control polygons ...

Progressive Subdivision Curves for Aerodynamic Shape Optimisation

This work presents a shape parameterisation method based on multi-resolutional subdivision curves and investigates its application to aerodynamic optimisation. Subdivision curves are defined as the limit curve of a recursive application of a subdivision rule, which provides an intrinsically hierarchical set of control polygons that can be used to provide surface control at varying levels of fidelity. This is used to construct a progressive aerofoil parameterisation that allows an optimisation to be initialised with a small number of design variables, and then periodically increased in resolution through the optimisation. This brings the benefits of a low dimensional design space (high convergence rate, increased robustness, low cost finite-difference gradients) while still allowing the final results to be from a high-dimensional design space. In this work the progressive refinement technique is tested on a variety of optimisation problems. For each problem a range of ‘static’ (non-progressive) subdivision schemes (equivalent to cubic B-splines) are also used as a control group. For all the optimisation cases the progressive schemes perform comparably or better than the static methods, often providing a significant computational advantage, and in many cases allowing a solution to be found when the static method would otherwise finish prematurely in a local optimum.

Efficient parameterization of waverider geometries

This paper summarizes the results of investigations into the development of parametric waverider geometry models, with emphasis on their efficiency, in terms of their ability to cover a large feasi...

Influence of Shape Parameterization on a Benchmark Aerodynamic Optimization Problem

This paper presents an investigation into the influence of shape parameterization and dimensionality on the optimization of a benchmark case described by the American Institute of Aeronautics and A...

The path to and state of geometry and meshing in 2030: Panel summary

Current and emerging trends in High Performance Computing (HPC) are providing transformational capabilities for simulation-based research and development and simulation-based design. Numerous efforts are underway to provide exascale systems in the next decades. HPC architectures are rapidly evolving and the tools and methods need to keep pace with both the scale and the evolving hardware architecture. Emerging HPC capabilities provide potential for simulation of increasingly complex, multi-scale and multidisciplinary applications for discovery, design and evaluation of aerospace systems. The computational mesh, along with the geometry that it represents, has a considerable impact on the quality, stability, and amount of resources required to complete numerical simulations. Extreme-scale environments require increased levels of process automation and reliability not currently available in state-of-the-art mesh generation tools. These shortcomings make geometry modeling and mesh generation a pacing bottleneck for the future. The paper will summarize the panel discussion that was held at AIAA’s 2015 SciTech Conference in which the path for geometry and mesh generation as a supporting element of the NASA CFD 2030 Vision was discussed.

On the conceptual design of waverider forebody geometries

This paper summarizes the results of investigations into the parametric geometry modeling of waverider forebodies, mostly centered on the osculating cones design method. Initially, three different approaches to controlling the leading edge shape are discussed. The first and most common method is driven by prescribing the upper surface trace on the base plane. The second incorporates a planform definition of the leading edge shape that gives more direct control of the sweep angle of the forebody. The third method directly controls the lower surface’s trace on the base plane. The shockwave profile curve that defines the shape of the shock is defined by its trace on the base plane for all three cases. Each method provides direct control over different aspects of the geometry for which a desired shape would be more complex to obtain indirectly. We then estimate the level of flexibility required by the design-driving curves in the context of a design optimization study, in order to enable a variety of meaningful designs without needlessly complicating the geometry model. Additionally, we show an efficient and robust method to introduce bluntness to the leading edge of waverider forebodies utilizing rational Bezier curves.

Parametric geometry models for hypersonic aircraft components: blunt leading edges

In this paper we report the results of investigations into the efficient parameterization of blunt leading edge shapes for hypersonic aircraft geometries. The investigations mostly revolve around waverider geometries generated with inverse design techniques, such as the osculating cones waverider forebody design method. The shapes presented however, can be utilized to introduce bluntness to any wedge-like geometry with sharp leading edges. Initially, we present detailed descriptions of three different variations of the rational Bezier curve based parameterization that was developed, and the variety of shapes that can be obtained is demonstrated. Afterwards their performance is evaluated utilizing 2D CFD analysis. In our simulations, the rational Bezier curve leading edges outperform circular ones when it comes to minimizing both drag and peak heating rates or peak temperatures. Additionally, with higher order rational Bezier leading edge shapes, higher levels of geometric continuity can be achieved at the interface between the blunt part and the original wedge-like geometry, resulting in a smoother transition. Preliminary results indicate that this can potentially affect the receptivity and hence transition mechanisms. Finally, the 2D geometry formulations are extended to full 3D waverider forebody geometries.

Cavity Flow over a Transonic Weapons Bay During Door Operation

This paper considers a transonic, idealized, weapons bay. The doors are either fixed or opened in a dynamic way. The flow evolves in three stages during door opening, corresponding to closed-cavity...