Unsteady force and flow features of single and tandem wheels

Abstract

Wind-tunnel experiments are presented in this paper for two different models, single wheel and tandem wheels. The tests are performed in the 2.1 m × 1.5 m wind tunnel at the University of Southampton. The aims of the experiment are to gain a better understanding of the flow past simple landing-gear components and to generate a CFD validation database. Since the model is designed to study basic landing-gear components, the wheel geometry is simplified, with no detailed elements in the assembly. The tandem-wheel configuration is formed of two in-line wheels that can be tested at different inter-axis distances and various angles of attack. Mean and unsteady data of aerodynamic loads and on-surface pressures are measured. A vibration test is performed in situ on the model assembly to validate the unsteady-load measurements. Particle Image Velocimetry (PIV) is used to acquire the velocity fields in the wake downstream of the model. The results highlight the low sensitivity of the measured quantities to the three versions of the wheel hub on the single wheel. The mean drag coefficients of the tandem wheels show a low sensitivity to the inter-axis distance, which has stronger effects on the mean lift coefficients and the unsteady aerodynamic loads. The angle of attack determines relevant changes in both mean and unsteady quantities. The pressures on the wheel surface are used for gaining a better understanding of the flow regimes and the effect of tripping the flow. Additionally, the PIV data are used to compare the velocity profiles in the wake and identify the wake vortical structures.

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