Feasibility of Boundary-Layer Control by Tangential Blowing for Suppression of Side Ventilation on Base-Vented Hydrofoil Struts.

摘要

Available literature and experimental evidence are evaluated to determine the feasibility of active flow control by tangential blowing (circulation control) to suppress sudden side ventilation on base-vented struts on an 80-knot, 200-ton hydrofoil. The conclusion is that there is no evidence that the method will not work and there is some promising but not fully-relevant evidence in favor. Based on a very crude estimate of the possible effectiveness of such a method, the power requirements were estimated for a four-degree improvement in ventilation angle for a single strut of 5 x 10 square feet submerged planform area at 80 knots. Power consumption is about 900 HP, with a flow rate of 7 cubic ft/sec and a pressure differential of about 500 psi. A large fraction, if not all of the power requirement is likely to be recovered in reduced drag. A five-inch diameter circular duct is adequate to carry the flow with minimal losses and smaller sizes may be acceptable. It is recommended that a simple flow visualization experiment be performed using blowing in a reduced-pressure water channel. This would establish or overcome the objection of possible adverse effects of cavitation on the technique.