Separation control by electromagnetic forces - applications at ships

The flow of electrically conducting fluids can be controlled by electromagnetic forces. Whereas this concept is already in industrial use in metallurgical or crystal growth technologies, its application to flows of electrolytes is less developed yet. For seawater flows around ship components, flow separation is an important phenomenon limiting the operation of, e.g., rudders or stabilizing foils. We present experimental and numerical results on the prevention of flow separation by means of a stream-wise, wall parallel Lorentz force acting on the suction side of inclined flat plates and hydrofoils. The use of steady as well as oscillatory Lorentz forces is considered. The results for oscillating Lorentz forces will be compared to recent literature results for periodic suction/blowing. Scaling relations for an extrapolation to application relevant Reynolds numbers will be given, and the related energy consumption will be analysed.