Unsteady aerodynamic loads on aircraft landing gear

Abstract

The aim of the current work is to improve the accuracy and efficiency of aerodynamic load predictions on landing gear in flight conditions, as part of the UK TSB ALGAAP(Advanced Landing Gear Aero-loads and Aero-noise Prediction) project. To this purpose,both experiments and simulations are performed on simplified landing-gear components.The new geometry presented in this work is a configuration composed of two simplified wheels in tandem. Experimental and numerical results from a single-wheel geometry are used as a baseline for comparison. The models are tested in the University of Southampton wind-tunnel complex, where forces, surface pressures and velocity fields are measured to gain a better understanding of both mean and unsteady flow features.Also, a vibration test is employed for the first time in a wind tunnel to validate the unsteady load measurements. The results of the experiments are presented in this thesis, showing the wake structure of the flow past the tandem wheels and the configurations that provide minimum values of mean drag and unsteady fluctuations. On the same single-wheel and tandem-wheel geometries, advanced numerical simulations such as Delayed Detached-Eddy Simulations (DDES) with the Spalart-Allmaras equation are used to predict the flow. The methodology is based on the use of techniques to improve the efficiency of the process, thus unstructured grids with a semi-structured boundarylayer mesh are employed to achieve the desired results. The results of the simulations are compared with the experiments, showing the importance of modifying the standard turbulence model in order to consider the laminar-turbulent transition for improved accuracy. Proper Orthogonal Decomposition (POD) is also employed to analyse the data of both experiments and simulation, in order to obtain a better insight of the flow features. Finally, additional simulations are performed on a simplified four-wheel landing gear to understand the effects of additional components, such as axles and bogie beam. The results show the high importance of the axles on the flow past the wheels and the effect of the modifications of the turbulence model on the full landing gear.

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