Wall-Layer Scale Electromagnetic Turbulence Control in an Axisymmetric Body

The progress made with the control of turbulence in a boundary layer developing over a small axisymmetric body in saltwater at moderate Reynolds numbers is briefly described. A resonance-interference mechanism of control by means of a small periodic Lorenz force confined to the near-wall region, designed to overcome the issue of low efficiency of electromagnetic turbulence control in general, is attempted to alter surface normal turbulence near-wall. At a low momentum thickness Reynolds number of 2300, drag is reduced by 15–25% at a freestream speed of 5.12 m/s with an efficiency of 2–3.4%. Bi-polar pulsing succeeds in lowering surface-normal turbulence intensity near wall. It also makes wall pressure fluctuations less spiky. Positive uni-polar pulsing is found to weaken the sources of wall-pressure fluctuations residing in the logarithmic region of the boundary layer. Further confirmatory work is needed with robust electrodes and drag measurements on a large diameter axisymmetric body.