A method for producing an object with riblets on and/or in the surface, around which object a fluid flows during use. A frictional resistance acting on a surface region along a flow direction during a flow around the object in the fluid is calculated and added up to a cumulative frictional resistance over a length of the surface region in the flow direction, after which the riblets are provided on and/or in a partial region of the surface in which an increase in the cumulative frictional resistance is at least 0.9, in particular greater than 1.0 to 0.9. Moreover, a method is provided for modifying a surface of an object around which a fluid flows during use, such as a foil. A structure having riblets is created on and/or in the surface, which structure reduces flow resistance of the object. Furthermore, a fluid flows around an object during use.

In one aspect of the present disclosure, a streamlined body for passing through a fluid is provided. The streamlined body includes an outer surface defining a leading edge and a trailing edge. The leading edge is oriented to pass through the fluid before the trailing edge during movement of the body through the fluid. The streamlined body further includes a plurality of fibers coupled to the outer surface. Each fiber of the plurality of fibers projects away from the outer surface.

The present invention relates to a surface cover for a body which can be brought into contact with a liquid, comprising: a layer which at least partly contains gas and which is designed and arranged such that at least some sections of a layer face facing the liquid contacts the liquid; a gas-permeable layer which is arranged on the gas-containing layer on a face that faces the body and is opposite the face facing the liquid or which is integrally formed with the gas-containing layer; and a gas-supplying device which is connected to the gas-permeable layer such that gas can flow from the gas-supplying device to the gas-containing layer through the gas-permeable layer. The invention also relates to an arrangement and a use.

The invention provides a method for computational fluid dynamics and apparatuses making enable an efficient implementation and use of an enhanced jet-effect, either the Coanda-jet-effect, the hydrophobic jet-effect, or the waving-jet-effect, triggered by specifically shaped corpuses and tunnels. The method is based on the approaches of the kinetic theory of matter providing generalized equations of fluid motion and is generalized and translated into terms of electromagnetism. The method is applicable for slow-flowing as well as fast-flowing real compressible-extendable generalized fluids and enables optimal design of convergent-divergent nozzles, providing for the most efficient jet-thrust. The method can be applied to airfoil shape optimization for bodies flying separately and in a multi-stage cascaded sequence. The method enables apparatuses for electricity harvesting from the fluid heat-energy, providing a positive net-efficiency. The method enables generators for practical-expedient power harvesting using constructive interference of waves due to the waving jet-effect.

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 of the fluid flow on the surface. In various embodiments, the transverse momentum injection actuators may be operated at frequencies less than 10,000 Hertz.

An airflow separation detecting method includes: applying an alternating-current voltage having a predetermined voltage value to a plasma actuator, the plasma actuator being disposed on a part of a surface of an object; and detecting that separation, from the surface of the object, of an airflow flowing on the surface of the object is occurring, in a case where an absolute value of a temporal variation rate of an electric power consumption value of the plasma actuator or an absolute value of a temporal variation rate of a current value of the plasma actuator is equal to or greater than a predetermined value, the temporal variation rate being a rate of variation relative to time, the electric power consumption value or the current value of the plasma actuator being measured under application of the alternating-current voltage having the predetermined voltage value to the plasma actuator.

A method is provided for producing a vortex ring in a liquid medium. The method includes concatenating pairs of insulated anode and cathode rings into a stack; inserting the stack into a vertically oriented chamber; disposing a cylindrical cavity below the chamber; inserting a piston into the cavity; connecting the chamber to the medium; and raising the piston to displace the medium while the stack produces an annular bubble that induces the vortex ring. In particular, the medium is water and the stack separates the medium into hydrogen and oxygen gas.

A system includes production tubing, a telescoping joint, a pump sub, a lock ring, and a crossover. The production tubing provides a hydraulic connection from a surface location to a well. The telescoping joint has a housing and a by-pass hanger having a head. An opening of the housing is larger than the by-pass hanger and smaller than the head and the head is moveably located within the housing. The lock ring is disposed around the by-pass hanger directly beneath the opening of the housing. The lock ring absorbs a compressive force and prevents the by-pass hanger from moving in an upwards direction. The crossover component is hydraulically connected to the production tubing and provides the hydraulic connection to the telescoping joint and the pump sub. The pump sub is located parallel to the telescoping joint, and the pump sub is connected to an electric submersible pump string.

In one embodiment, a method for reducing drag includes forming a smooth surface on a first portion of a physical object. The method also includes forming periodic riblets on a second portion of the physical object. The method further includes generating a flow over the periodic riblets of the second portion of the physical object and over the smooth surface of the first portion of the physical object. The second portion of the physical object is adjacent to the first portion of the physical object. Each peak of each riblet of the periodic riblets of the second portion of the physical object is located above a plane of the smooth surface of the first portion of the physical object. Each valley between adjacent riblets of the periodic riblets of the second portion of the physical object is located below the plane of the smooth surface of the first portion of the physical object. A length of each riblet of the periodic riblets runs parallel to a direction of the flow.

Fluid systems are described herein. An example embodiment of a fluid system has a first body portion, a second body portion, a plurality of supports, a plurality of fluid pressurizers, and a plurality of ducts. The first body portion and the second body portion cooperatively define an injection opening, a suction opening, and a channel that extends from the injection opening to the suction opening. The fluid pressurizer is disposed within the channel cooperatively defined by the first body portion and the second body portion. Each duct of the plurality of ducts is disposed within the channel cooperatively defined by the first body portion and the second body portion.