Effect of through-hole angle on particle wake

The wake characteristics of a solid particle featuring a through-hole were investigated using particle image velocimetry. The particle had a diameter of $$d = 25.4$$ mm, with a through-hole diameter ratio of γ = dₕ/d = 0.24 , where dₕ represents the diameter of the through-hole. The particle was placed in a uniform flow with a velocity U₀ = 3.6 m/s, yielding a Reynolds number of approximately 6000. The orientation of the through-hole relative to the uniform flow α was varied from 0 deg to 90 deg. For the solid particle without a hole, the wake demonstrated a pronounced velocity deficit and a pair of symmetric vortices behind the particle. Introducing a through-hole resulted in the formation of a jet emerging from the hole into the wake at 10 ≤ α ≤ 60 deg. The jet velocity decreased as α increased, and the jet disappeared for α ≥ 70 deg. Downstream of x/d ≥ 2 , the velocity field became independent of α . At α =0 deg, two pairs of vortices were generated by the interaction of the shear layers and hole jet. For α ≥ 10 deg, one vortex of each pair disappeared. For 20 ≤ α ≤ 40 deg, the vortex size associated with the hole jet increased with increasing α . For α ≥ 70 deg, the wake structure closely resembled that of a solid particle. These findings demonstrate that the through-hole angle exerts a significant influence on the near-wake structure, and they provide further support for the interference model between the hole jet and shear layer proposed in previous studies.