A Numerical Study on the Influences of Non-Pneumatic Tyre Shape on the Wheel Aerodynamics

Abstract

Abstract: In the present work, the aerodynamic characteristics of two different tyre shapes, Slick Tyre (ST) and Non-Pneumatic Tyre (NPT), fitted to a rotating wheel, has been investigated using a CFD approach. The ST wheel has been primarily utilized to examine the adopted numerical model's validity. The ST wheel pressure coefficient (Cp) profile at its central plane (XY) has directly compared with the robust experimental data experienced from the literature. Further assessments on the computationally obtained outcomes such as drag coefficient, separation and stagnation angular locations are performed. Both wheel cases are compared concerning their aerodynamic coefficients and the flow characteristics around the wheel. Besides, for the NPT wheel case, a shape-optimization study changes the wheel side profile's spokes angle (α) is conducted. The dynamic action of wheel rotation is modelled using the Moving Reference Frame (MRF) technique, and the RNG k- ࢿ is utilized as the adopted turbulence model for Averaged Reynolds Navier Stokes equations (RANS). All cases run at 30 m/s upstream velocity to be within the fully developed flow regime (supercritical regime). That is equivalent to 6.8 ×105 Reynolds number based on the wheel diameter as the characteristic length. In general, the overall obtained results give a satisfactory agreement to those measured experimentally. In conclusion, The NPT wheel, compared to the ST wheel, has a dramatic increase in drag force by approximately 31%, while a slightly raised lift force is obtained. The minimized spoke angle came with a beneficial drag reduction, while the applied resistive moment remained relatively high. Keywords: automotive aerodynamics; wheel aerodynamics, tyre CFD; rotating wheel dynamics; MRF wheel simulation; airless tyre aerodynamics, non-pneumatic tyre aerodynamics.