In-plane transverse momentum injection to disrupt large-scale eddies in a turbulent boundary layer

A power-saving method, comprising:

• selecting a timescale multiplier, T+, greater than 300 for a fluid flowing over a surface having a friction Reynolds number, Reτ, greater than 1,500;
• calculating an actuation frequency, f, based on the selected time scale multiplier, T+, and the friction Reynolds number, Reτ, of the fluid;
• and
• actuating a plurality of actuators on the surface at the actuation frequency, f, to reduce a friction characteristic of a turbulent boundary layer of the fluid flowing over the surface, wherein the timescale multiplier, T+, is selected such that power consumption to actuate the plurality of actuators at the actuation frequency, f, is less than an amount of power saved due to the reduced friction characteristics of the fluid flowing over the surface.

A method to modify drag on a surface, comprising:

• selecting a time scale multiplier, T+, greater than 300 for a viscous time scale, η′, in a turbulent boundary layer of a fluid flowing relative to a surface of an object with a friction Reynolds number, Reτ, greater than 1,500;
• calculating an actuation frequency, f, for injecting momentum along the surface of the object and perpendicular to a direction of fluid flow relative to the surface of the object to disrupt the range of large-scale eddies in the turbulent boundary layer with characteristic time scales exceeding 300η′;
• and
• actuating a plurality of actuators with the calculated actuation frequency, f, to inject momentum perpendicular to the direction of fluid flow to disrupt the range of large-scale eddies to selectively increase or decrease the drag of the fluid on the surface of the object.