초록 ▼

A method of disrupting a turbulent region of a boundary layer within a fluid flow passing over a surface to decrease momentum transfer, and thus friction drag, between the turbulent flow and the surface. Bending waves are generated on the surface to impose velocity and/or pressure oscillations withi

A method of disrupting a turbulent region of a boundary layer within a fluid flow passing over a surface to decrease momentum transfer, and thus friction drag, between the turbulent flow and the surface. Bending waves are generated on the surface to impose velocity and/or pressure oscillations within the turbulent region and disrupt the normal turbulent process within the boundary layer, thereby decreasing the transfer of momentum from the turbulent flow to the surface. The bending waves are preferably generated in a predominantly spanwise or normal direction relative to the streamwise fluid flow. In another embodiment, the bending waves enhance the turbulent process and increase the transfer of momentum between the turbulent flow and the surface. Bending wave actuators may bend the surface to generate bending waves within the surface itself. In another embodiment, actuators may generate bending waves within a separate material attached to the surface. Bending waves may also be generated within a laminar region of the boundary layer to trip the laminar region to turbulent flow and thereby energize the boundary layer.

대표청구항 ▼

[ The invention claimed is:] [1.] A method of modifying momentum transfer between a fluid flow and a surface over which the fluid flow passes in a streamwise direction by steps comprising disrupting a turbulent region of a boundary layer of the fluid flow passing over the surface, and maintaining th

[ The invention claimed is:] [1.] A method of modifying momentum transfer between a fluid flow and a surface over which the fluid flow passes in a streamwise direction by steps comprising disrupting a turbulent region of a boundary layer of the fluid flow passing over the surface, and maintaining the disruption of the turbulent region in a spacially-continuous pattern over an entire substantial spanwise dimension of the surface, the substantial spanwise dimension extending at an angle of greater than 45 degrees with respect to the streamwise direction, said method further comprising:positioning a bending wave actuator relative to the surface to interact with the boundary layer of the streamwise passing fluid over substantially the entire spanwise dimension of the surface;energizing the actuator in a predetermined controlled manner to generate and maintain a predetermined spacially-continuous waveform of bending wave oscillations of predetermined wavelengths and amplitudes in the boundary layer over substantially the entire substantial spanwise dimension; andimposing and maintaining oscillations in the streamwise passing boundary layer over substantially the entire substantial spanwise dimension of the surface in the spacially-continuous pattern by transferring energy from the spacially-continuous waveform of bending wave oscillations generated by energizing the actuator, the imposed oscillations in the boundary layer being sufficient to modify the momentum transfer from the turbulent region to the surface.