Adaptive computation of aeroacoustic sources for a rudimentary landing gear
Authors: Rodrigo Vilela de Abreu, Niclas Jansson and Johan Hoffman
Article first published on
International Journal for Numerical Methods in Fluids.
Computational Technology Laboratory,
Department of High Performance Computing and Visualization,
School of Computer Science and Communication and Linné FLOW Centre,
KTH, SE-10044 Stockholm, Sweden
Computational Technology Laboratory,
Department of High Performance Computing and Visualization,
School of Computer Science and Communication,
KTH, SE-10044 Stockholm, Sweden
SUMMARY
We present our simulation results for the benchmark problem of the flow past a rudimentary landing gear using a General Galerkin FEM, also referred to as adaptive DNS/LES. In General Galerkin, no explicit sub-grid model is used; instead, the computational mesh is adaptively refined with respect to an a posteriori error estimate of a quantity of interest in the computation, in this case, the drag force on the rudimentary landing gear. Turbulent boundary layers are modeled using a simple wall-layer model with the shear stress at walls proportional to the skin friction, which here is assumed to be small and, therefore, can be approximated by zero skin friction. We compare our results with experimental data and other state of the art computations, where we find good agreement in sound pressure levels, surface velocities, and flow separation. We also compare with detailed surface pressure experimental data where we find largely good agreement, apart from some local differences for which we discuss possible explanations. Copyright © 2013 John Wiley & Sons, Ltd.
Received 31 August 2012; Revised 19 July 2013; Accepted 12 October 2013
KEY WORDS: aeroacoustics; aerodynamics; finite element; incompressible flow; LES, large Eddy simulations; turbulent flow.
- INTRODUCTION
This work may be seen as an extension of our contribution to the BANC-I NASA/AIAA workshop held in conjunction with the 16th AIAA/CEAS Aeroacoustics Conference in Stockholm, 2010. One of the principal goals of the workshop was to assess available computational methods for the computation of aeroacoustic sources by comparing simulation results with experimental work. The workshop consisted of a set of four benchmark problems, and we chose to solve the problem of the flow past a rudimentary landing gear (RLG). The RLG geometry was developed at Boeing Commercial Airplanes and is a non-proprietary, highly simplified version of a four-wheel landing gear. It consists of a square-based sustaining post, a wheel frame with square-based axles, and the four wheels (Figure 1). One of the reasons of using such a simplified geometry in a workshop is that by being non-proprietary, it allows for unrestricted sharing of data and open publication of results. Furthermore, the boundary layers are ‘tripped’ to turbulent on the surface of all four wheels, so that separation is mainly defined by the sharp edges of the geometry, simplifying the comparison between different turbulence models (for a detailed description of the boundary layer tripping method, see [1]).
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