METHOD OF REDUCING DRAG AND INCREASING LIFT DUE TO FLOW OF A FLUID OVER SOLID OBJECTS

摘要

A method for reducing drag, increasing lift and heat transfer using a de-turbulating device is disclosed, with the preferred form of the deturbulator being a flexible composite sheet. The flexible composite sheet comprising a membrane, a substrate coupled to the membrane, and a plurality of ridges coupled between the membrane and the substrate, wherein a vibratory motion is induced from the flow to at least one segment of a membrane spanning a distances, wherein the vibratory motion is reflected from at least one segment of the membrane to the flow, and; wherein a reduction in fluctuations is caused in the flow pressure gradient and freestream velocity U at all frequencies except around f, where f » U/s. hi one embodiment, the flexible composite sheet can be wrapped around a blunt leading edge of a plate facing an incoming flow of fluid, hi another embodiment, the flexible composite sheet can also be wrapped around one or more regions of an aerodynamic surface where a flow pressure gradient changes from favorable to adverse, hi another embodiment, the flexible composite sheet is replaced with a plurality of plates coupled to a substrate, wherein the plurality of plates has edges that interact with a fluid flow similar to a compliant surface. A method of adding a system of small viscous sublayer scale (around 30-80 micron height) backward and /or forward facing steps on the surface of an airfoil or other 2-D or 3-D streamlined aerodynamic body is disclosed, where the backward facing step is in a favorable pressure gradient and forward facing step is in an adverse pressure gradient, so as to speed up the freestream flow over the front portion of the airfoil or body and reduce skin friction drag by creating a marginally separated thin (0.1 to 10 microns) slip layer next to the wall behind the backward facing step and extending a significant distance behind said step. This method reduces the drag and increases lift if the body is a wing. Also the same method can be applied to a bluff body, such as an automobile to reduce flow separation induced drag by stabilizing the wake flow and making it appear to the flow as a solid streamiling extension of the original body. The gas mileage of a vehicle improves when treated in this manner.