Flow structures on rolling wheels in various thicknesses and Reynolds numbers.

Direct numerical simulations of rolling wheels at Reynolds numbers, Re D , based on wheel diameter, D , in the range of Re D ∈ 3.0 × 10 3 − 3.0 × 10 5 corresponding with translation speed of U ∞ ∈ 0.1 − 10 m/s, and varying thickness-to-diameter ratios, R = W / D ∈ 0.040,0.127,0.400 , are conducted with the objective of characterizing the coherent flow structures and their effect on forces. Previous work by A. Javadi (2022)1 for Re D = 3.0 × 10 4 shows non-monotonic variation of drag coefficients with thickness change. Under the flow conditions essayed here, C D steadily decreases as Re D increases. If R = 0.04 the drag coefficient is C D ∈ 0.4 − 1.4 , while it decreases from unity to 0.5 if R = 0.400. The lift force is downward for the wheel with R = 0.040, while it changes its direction if the thickness and/or Re D number increases. The downward lift force for rolling wheel is associated with the Magnus effect. The positive lift force, provided on the rolling wheel with R = 0.127 and 0.400, is associated with strong (positive) peak of the static pressure in the upstream vicinity of the contact point with the ground. The positive lift force also significantly decreases from unity to 0.3 as Reynolds number increases. The effects of the thickness on the flow structures in the wake are revealed, especially in high Re D numbers. On the top of the wheel, there is hairpin vortex at Re D = 3.0 × 10 3 , while the structure becomes unsteady and loses its coherence in higher Reynolds numbers. There is no coherent structures on the top of the thickest wheel because the wheel rotation avoids forming any structure. The large dipole vortex pinch off from the sides of the wheel with R = 0.400 causes large force fluctuations. [ABSTRACT FROM AUTHOR]