Flow characteristics of three-dimensional offset jet over surface-mounted ribs using large-eddy simulation

This study employs large-eddy simulations to investigate the turbulent structure and wake dynamics of a three-dimensional offset jet interacting with surface-mounted ribs at width-to-height ratios W/H = 1, 2, and 3. First, the simulated results for W/H = 1 are benchmarked against a prior experimental study, demonstrating strong agreement in predicting the maximum local velocity profile and Reynolds normal stress within the recirculation region. Building on this validation, a comprehensive analysis is performed to describe the influence of rib geometry on flow characteristics, specifically within recirculation, reattachment, redevelopment, and downstream regions. Qualitative assessments, including mean velocity and turbulent kinetic energy contours, pressure coefficient fields, and streamline visualizations, are combined with quantitative evaluations of first- and second-order turbulence statistics (e.g., mean flow, root mean square velocities, and Reynolds shear stresses) to provide insights of the flow. The results reveal that flow separation begins at the leading edge of the ribs, and the region of elevated turbulence expands as the W/H ratio increases. The reattachment process and the evolution of the shear layer are strongly influenced by rib geometry, creating pronounced differences in turbulence production and transport. Furthermore, insight is obtained through single and joint probability density functions, two-point correlation analyses, and spectral density at three downstream locations. These techniques highlight how the largest rib induces an extended recirculation region and sustains turbulence energy farther into the wake. Taken together, these results demonstrate the significant influence of the width-to-height ratio on offset jet flow and wake dynamics, offering valuable insights into the complex interplay between turbulent flows and surface-mounted ribs.