Three-dimensional wake dynamics of a normally impinging turbulent circular jet interacting with slitted circular cylinders

The three-dimensional wake dynamics generated by the interaction between a turbulent normally impinging circular jet and slitted circular cylinders are investigated experimentally using time-resolved particle image velocimetry (TR-PIV). Measurements are performed in both the transverse ( x – y ) and spanwise ( x – z ) planes for baseline, vertical-slit, and horizontal-slit cylinder configurations at impingement distances of H / D = 1.5 and 3 over Reynolds numbers ranging from R e D = 7504 to 11574. Ensemble-averaged velocity, vorticity, turbulence kinetic energy, Reynolds stresses, coherent vortical structures, and spectral characteristics are analyzed to elucidate the mechanisms governing wake development. These observations indicate that slit orientation is a dominant parameter influencing the measured wake dynamics over the investigated conditions. The vertical slit acts as a passive momentum-injection device that introduces additional streamwise momentum into the near wake, suppressing shear-layer instability, reducing turbulent transport, and promoting rapid wake recovery. In contrast, the horizontal slit generates a passive blowing–suction interaction that enhances lateral and spanwise momentum redistribution, producing stronger three-dimensional mixing and more complex coherent-structure dynamics. Spectral analysis reveals that the vertical slit preserves a predominantly single instability mode, whereas the horizontal slit promotes quasi-periodic oscillations through the coexistence of multiple energetic modes. The measured Strouhal numbers are substantially lower than those associated with canonical circular-cylinder wakes, indicating that wake instability is governed by passive momentum injection rather than classical von Kármán vortex shedding. Spanwise measurements further demonstrate that the flow is intrinsically three-dimensional, with slit orientation controlling vortex development throughout the cylinder span. These findings establish a previously unexplored passive momentum-injection mechanism in normally impinging jet–cylinder interactions, demonstrating how slit-mediated blowing and suction govern three-dimensional wake instability, coherent-structure dynamics, and turbulent momentum transport.