Turbulence and Recirculation Modulation in a Wall-mounted Cruciform

The investigation presented aims to compare the turbulence and recirculation characteristics of cross-cylinder arrangements. Cross-cylinder structures alter the effect of local ocean currents, fish populations and scouring of the surrounding sediment. Several hydrodynamic environments are home to this type of flow such as in the areas of off-shore oil rigs, reef restoration stations and in the foundations of pier piles. The flow over the body of a cruciform with modified branch angle is used to demonstrate the changes in the flow field impacting the turbulence statistics and the resulting recirculation zone aft of the geometry. During local optimization of the branch angle of the cruciform, the reduction in drag coefficient was associated with changes in the size of the recirculation zone, the coherence of the cross-cylinder's vortex shedding and the wake. The cross-cylinder arrangements with modified branch angle demonstrate lower coefficient of drag at lower branch angle is attributed to a shift in wake size and breakdown in the shedding structure coherency. The turbulence characteristics of the interaction between the recirculation zone and branch shedding vortices is captured through hybrid RANS/LES formulation (IDDES) for a neutral, high and low branch angled cruciform. The work will focus on the cross-cylinder arrangements at a Reynolds number of ~7500 using 0.3 m/s inlet flow. Analysis of the turbulent kinetic energy budget transport, time averaged fluctuations, probability distribution functions and two-point correlations will be utilized to complement the qualitative turbulence structures identified within the flow field of the cruciform.