DDES simulation of a complex main landing gear with a six-wheel bogie

Abstract

This paper investigates numerically the flow and unsteady aerodynamics of a complex landing gear using Delayed Detached Eddy Simulation (DDES). The case studied is a six-wheel main landing gear with some medium and small components included, which has been measured previously in wind tunnel. The aim of this study is to extend landing gear modelling to more complicated geometry and to understand the unsteady aerodynamic loads and flow features around landing gears with complex configuration. A meshing strategy based on unstructured mesh is used to cope with the geometrical complexity. Carefully chosen refinement zones and structured boundary layer meshes are employed to improve the mesh quality, which helped to ensure the accuracy for the DDES simulation. A hex-dominated mesh with 37 million cells was generated with resolved boundary mesh using 10-21 layers on all landing gear components. It is found that flow around the bogie is more complex due to stronger interactions between wheels in close proximity for the six-wheel bogie. Other components, such as wheel axles, bogie pitch trimmer, forward dressing link and after torque link introduces flow unsteadiness in the bogie region. Statistics of mean and RMS forces for all components of the main landing gear are obtained. The drag on the front pair of wheels was found to be lower than the middle and the back wheels. The presence of forward and after side stays (or diagonal struts) on the landing gear possibly creates asymmetry in the flow field. This asymmetric flow features further changes the separation on and around the wheels and influence its wake region. The presence of the components like side stays, forward dressing link and the after torque link changes the wake pattern behind the cylindrical strut. This increases the mean drag coefficient of the main strut compared to that of a simple cylinder with similar geometrical dimensions. This suggests that smaller components may play a significant role in changing flow features around a bigger component. The RMS side force coefficient of the main strut is higher than the RMS lift and drag coefficients, indicating a possibility of strong interaction between the main strut and wheels. Also, efforts are made to understand the unsteadiness in the landing gear wake. This study contributes to the limited literature available for aircraft main landing gear configurations with more geometrical details.

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