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First we present high resolution large eddy simulations (LES) for the flow past a circular cylinder at Reynolds number 3900 to prove the quality of the simulations. A thorough grid convergence study is presented, and the agreement in the mean flow statistics between our simulations and the references is excellent. Then we apply a no-slip boundary condition at the spanwise boundaries of the cylinder, with aspect ratios of 6, 12 and 24. This results in large changes in the shear layers and wake topology, even for an aspect ratio of 24. Even though the boundary layers along the side walls are only about 0.4 diameters thick, they nevertheless manage to stabilize the shear layers all the way through the channel, thus effectively delaying the roll-up and transition to a turbulent wake.

We describe the flow around a 6:1 prolate spheroid at 45 • inclination angle and Reynolds number 4000 based on the minor axis. Despite that the inflow is uniform and steady, the resulting wake is highly asymmetric and unsteady. Two main vortical structures develop from the shear layers of the spheroid, one being significantly stronger than the other. This asymmetry results in a non-zero sideforce. The forces acting on the spheroid change dramatically from earlier works at Reynolds number 3000. The pressure inside the vortex cores also changed with this moderate increase in Reynolds number. This indicates that the flow is highly transitional.We also document that close to the body, on the side of the weaker vortex, there is a region of negative axial velocity. In this backflow region, the fluid enters from behind the spheroid and travels forward against the inflow and then exits the backflow region through one of the main vortical structures. This backflow has not been described before. We also observe and describe a distinct Kelvin-Helmholtz shear layer instability close to this region.x ax Spheroid major axisx, y, z Cartesian coordinatesThis is a post-print. The Online version is found via. AIAA J. website: https://arc.aiaa.org/doi/full/10.2514/1.J057615 where supplementary animation can also be downloaded.

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This paper present results from numerical simulations and laboratory experiments investigating the flow around a riser with fairings at Reynolds number of 5000. We present fully resolved direct numerical simulations (DNS), large eddy simulations (LES) and compare the results with flowfields obtained from particle image velocimetry (PIV) experiments in a circulating water tunnel. The DNS and LES results do agree very well on surface integral quantities such as drag and lift force, but there are discrepancies in first order statistical flow parameters such as recirculation length. This indicate that a comparison of force coefficients is not sufficient to validate this type of bluff body wake flows. Comparing the simulation data with the experimental PIV data, also reveals significant discrepancies in the mean flow field, although the Strouhal number agrees between DNS and PIV results.

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