Various implementations include a fluidic oscillator array including at least two fluidic oscillators, each including an interaction chamber, fluid supply inlet, outlet nozzle, and feedback channels. The interaction chambers have a first and second attachment wall. Fluid streams flow from the fluid supply inlets, into the interaction chambers, and exit through the outlet nozzles. A feedback channel is coupled to each of the first and second attachment walls. Each feedback channel is in fluid communication with the interaction chamber and has an intermediate portion disposed between a first and second end of the feedback channels. Fluid from the fluid stream flows into the first ends of the respective feedback channels, causing the fluid stream to oscillate between the first and second attachment walls. Adjacent feedback channels of adjacent fluidic oscillators share a common intermediate portion, causing the exiting fluid streams of each fluidic oscillator to oscillate at the same frequency.

A vortex-controlled variable flow resistance device ideal for use in a backpressure tool for advancing drill string in extended reach downhole operations. The characteristics of the pressure waves generated by the device are controlled by the growth and decay of vortices in the vortex chamber(s) of a flow path. The flow path is designed to produce alternating primary and secondary vorticesone clockwise and one counter-clockwisewhere the primary vortex is stronger and produces higher backpressure than the secondary vortex. This in turn generates alternating weak and strong pressure pulses in the drill string. The weak pulses may be barely perceptible so that the effective frequency of the pulses is determined by the stronger primary vortices.

A vortex-controlled variable flow resistance device ideal for use in a backpressure tool for advancing drill string in extended reach downhole operations. The characteristics of the pressure waves generated by the device are controlled by the growth and decay of vortices in the vortex chamber(s) of a flow path. The flow path is designed to produce alternating primary and secondary vorticesone clockwise and one counter-clockwisewhere the primary vortex is stronger and produces higher backpressure than the secondary vortex. This in turn generates alternating weak and strong pressure pulses in the drill string. The weak pulses may be barely perceptible so that the effective frequency of the pulses is determined by the stronger primary vortices.

Various implementations include a fluidic oscillator array including at least two fluidic oscillators, each including an interaction chamber, fluid supply inlet, outlet nozzle, and feedback channels. The interaction chambers have a first and second attachment wall. Fluid streams flow from the fluid supply inlets, into the interaction chambers, and exit through the outlet nozzles. A feedback channel is coupled to each of the first and second attachment walls. Each feedback channel is in fluid communication with the interaction chamber and has an intermediate portion disposed between a first and second end of the feedback channels. Fluid from the fluid stream flows into the first ends of the respective feedback channels, causing the fluid stream to oscillate between the first and second attachment walls. Adjacent feedback channels of adjacent fluidic oscillators share a common intermediate portion, causing the exiting fluid streams of each fluidic oscillator to oscillate at the same frequency.

A vortex-controlled variable flow resistance device ideal for use in a backpressure tool for advancing drill string in extended reach downhole operations. The characteristics of the pressure waves generated by the device are controlled by the growth and decay of vortices in the vortex chamber(s) of a flow path. The flow path is designed to produce alternating primary and secondary vorticesone clockwise and one counter-clockwisewhere the primary vortex is stronger and produces higher backpressure than the secondary vortex. This in turn generates alternating weak and strong pressure pulses in the drill string. The weak pulses may be barely perceptible so that the effective frequency of the pulses is determined by the stronger primary vortices.

The invention relates to fluid actuator for influencing the flow along a flow surface through ejection of a fluid. By means of a like fluid actuator, a continuous flow is distributed to at least two outlet openings in order to generate fluid pulses out of these outlet openings. Control of this distribution takes place inside an interaction chamber which is supplied with fluid flow via a feed line. Into this interaction chamber there merge at least two control lines via control openings to which a respective different pressure may be applied. Depending on the pressure difference at the control openings, the flow in the interaction chamber is distributed to the individual outlet openings.