A system includes a surface, an actuator, and a controller. The surface has a fluid flowing over the surface. The actuator is coupled to the surface to move the surface relative to the fluid. The controller causes the actuator to cause the surface to generate a surface wave that modifies drag in the fluid. The actuator can cause the surface to generate a Love wave.

According to the present disclosure there is provided an arrangement for influencing fluid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface, the vortex generator surface comprising a series of laterally aligned projections, to induce vortices in the liquid flow.

Provided is an actuator apparatus including a positioning actuator device configured to position a first carrier member of the actuator apparatus. The positioning actuator device includes a first hydraulic fluid actuator having a first clamping means and a second hydraulic fluid actuator having a second clamping means, wherein the first and second hydraulic fluid actuator are configured to alternately clamp around a guide arrangement for moving the positioning actuator device along the guide arrangement. The first carrier member is provided with a first coupling member configured to be releasable coupled to the positioning actuator device. A method of positioning a first carrier member by means of the positioning actuator device is provided.

A fairing, in the form of a contoured restriction, submerged on a fluid channel surface of a fluid channel through which liquid flows, re-distributes velocity fields and flow geometries upstream and in some embodiments downstream of a discontinuity, thereby preventing flow separation, reducing cavitation potential and increasing flow capacity. Such discontinuities include, but are not limited to: joints, for example elbow joints, T-joints and Y-joints; valve-trims ; entrance regions to centrifugal pumps; and entrance regions to rotary valves, steps, reductions, expansions and ledges. The fairing may be fitted into the channel or integrally fabricated with the channel.

Provided is an apparatus for removing thermal stratification generated by turbulent penetration by using a rotation ring. The apparatus removes thermal stratification formed in a branch pipe branching from a main pipe through which a high-temperature fluid flows, the apparatus including: a hollow body portion coupled to the branch pipe; a plurality of first electromagnets provided to be spaced apart from each other in a circumferential direction of the body portion; a controller configured to sequentially change polarities of the plurality of first electromagnets; and a rotation ring including a plurality of second electromagnets having either an N polarity or an S polarity, the rotation ring being rotatably coupled to the body portion, wherein, when the polarities of the plurality of first electromagnets are sequentially changed, the rotation ring rotates according to a magnetic force of the plurality of first electromagnets and the plurality of second electromagnets.

Systems and methods are described herein to implement transverse momentum injection at low frequencies to directly modify large-scale eddies in a turbulent boundary layer on a surface of an object. A set of transverse momentum injection actuators may be positioned on the surface of the object to affect large-scale eddies in the turbulent boundary layer. The system may include a controller to selectively actuate the transverse momentum injection actuators with an actuation pattern to affect the large-scale eddies to modify the drag, fluid mixing, heat transfer, and/or other interactions of the fluid flow with the surface. In various embodiments, the transverse momentum injection actuators may be operated at frequencies less than 10,000 Hertz.

A lift control device actively controls the lift force on a lifting surface. The device has a protuberance near a trailing edge of its lifting surface, which causes flow to separate from the lifting surface, generating regions of low pressure and high pressure which combine to increase the lift force on the lifting surface. The device further includes a means to keep the flow attached around the protuberance or to modify the position of the protuberance in response to a command from a central controller, so as to provide an active control of the lift between a maximum value and a minimum value.

A fluid control system includes a dielectric-barrier discharge (DBD) device, and processing circuitry. The processing circuitry is configured to obtain a streamwise length scale of a fluid flowing over a surface. The processing circuitry is also configured to obtain a convective time scale of the fluid flowing over the surface. The processing circuitry is also configured to operate the DBD device, based on the streamwise length scale and the convective time scale, to adjust a flow property of the fluid.

An aircraft control system includes a flow control device and a control circuit. The flow control device is configured to control a flow of air around an aircraft. The control circuit is configured to control the flow control device so that a pressure distribution loaded on a surface of a structure that constitutes the aircraft is equal to a control value of a pressure distribution calculated based on a physical quantity detected by a sensor provided in the aircraft. The physical quantity relates to the air.

A flow control system includes a movable wing attachable to a wing of an aircraft, and a plasma actuator mountable on a surface of the movable wing. The flow control system is configured to control air flow around the wing by having the changing of the steering angle of the movable wing work in conjunction with the operation of the plasma actuator.