Effect of aspect ratio of a spanwise sinusoidal profile on the control of turbulent flows around bluff bodies

• Spanwise Sinusoidal Profiles (SSPs) reduce drag and lift fluctuations by 30% and 95%.
• An SSP reduces the drag and the lift fluctuations on elongated bodies by 10% and 83%.
• The turbulent flow field resulting from an SSP is highly three-dimensional.
• Aspect ratio does not influence the effectiveness of an SSP on elongated bluff bodies.
• The flow field of elongated bluff bodies can resemble that of streamlined geometries.

The deleterious effects of the steady and transient forces on bluff bodies, resulting from turbulent flows, are ameliorated by imposing a spanwise sinusoidal profile (SSP) on their leading edges. Large eddy simulation (LES) is used to elucidate the spatial and temporal details of the flow fields resulting from both square and elongated SSP bluff bodies. Two dimensionless parameters define the geometry of an SSP, namely the wave steepness and normalised wavelength.In a turbulent flow field, it is observed that an SSP with a wave steepness of 0.2 and a normalised wavelength of 2.4 can result in reductions in the rms drag and lift forces by up to 30% and 95%, respectively. The wakes shed by plain cylinders contain Kármán vortices, however, Kelvin–Helmholtz type vortices form in the upper and lower shear layers of an SSP cylinder.An SSP imposed on the leading edge of a bluff body elongated in the direction of the flow is found not to be profoundly affected by the aspect ratio. A bluff body with a length-to-height aspect ratio of 5 maintains a highly three-dimensional flow field, and a narrow wake that resembles the characteristics of a streamlined body; this research offers a myriad of industrial applications.