In an embodiment, an article comprises a plurality of structural units, wherein each structural unit comprises a first portion; a second portion; wherein the second portion contacts the first portion; and a third portion; wherein the third portion is in communication with the first portion and the second portion and is more compressible than the first portion and the second portion; where the first portion has a first value of a property and where the second portion has a second value of the same property, such that the first value acts as a restraining or enhancing force on the second value; wherein the first portion comprises a first metal and wherein the second portion comprises a second metal that is different from the first metal.

A system for slowing down the speed of flying objects by applying electrodynamic and aerodynamic braking forces. The system is comprised of plurality of stubs, where each stub is made of dielectric material surrounded by metal foil and another metal foil is inserted in the middle of the stub, where the outer metal foil and the inner metal foil are isolated from each other, so that they form a capacitor. Each stub is stored in a barrel before being used. When activated, the stubs are stretched from the barrel as a tail behind the flying object. The area of the stub generates aerodynamic drag. The stub capacitor is charged by a generator so that free electrons are present in the outer metal layer of the stub. The electric field produced by these charges interacts with ions in the atmosphere.

A system includes a surface, an actuator, and processing circuitry. The surface includes one or more non-actuating zones and one or more actuatable zones. The actuator is configured to a flow property of a fluid that flows over the one or more actuatable zones of the surface. The processing circuitry is configured to obtain a value of a parameter of the fluid that flows over the surface, and operate the actuator to adjust the flow property of the fluid that flows over the one or more actuatable zones based on the value of the parameter of the fluid.

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.

A flow body for a vehicle having a flow surface, as well as a skin system attached to the flow surface is proposed. The skin system has a top layer and a foam arrangement positioned between the flow surface and the top layer, wherein the top layer includes an elastic, surface-like material, wherein the foam arrangement includes a first layer of an elastic, compressible open cell foam, wherein the foam arrangement is bonded to the top layer. The skin system has a static shape in an unloaded state, in which the shape defines an outer surface geometry that directly follows the geometry of the respective flow surface, and the skin system has a deflected shape when the flow body is subjected to turbulent air flow. The deflected shape at least temporarily compresses the foam arrangement.

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.

Variable-porosity panel systems and associated methods. A variable-porosity panel system includes a panel assembly with an exterior layer defining a plurality of exterior layer pores and a sliding layer adjacent to the exterior layer and defining a plurality of sliding layer pores. The variable-porosity panel system additionally includes a shape memory alloy (SMA) actuator configured to translate the sliding layer relative to the exterior layer to modulate a porosity of the panel assembly. The SMA actuator includes an SMA element configured to exert an actuation force on the sliding layer and at least partially received within an SMA element receiver of the sliding layer. The SMA element extends out of the sliding layer only at a sliding layer first end. A method of operating the variable-porosity panel system includes assembling the variable-porosity panel system and/or transitioning the panel assembly of the variable-porosity panel system among the plurality of panel configurations.

Method of adjusting the pressure balance or a control device, in particular of a servo valve, the requisite adjusting movement being applied by a disc translator.

An element comprising a non-stick surface for substantially cleanly removing a product which is arranged against said non-stick surface. The element comprises a first layer of an pervious material, which is configured to allow a fluid to flow there through. An outer surface of said first layer provides the non-stick surface. The element comprises a second layer of an impervious material, which is configured to substantially block a flow of fluid there through. The second layer is arranged at a side of said first layer opposite to the outer surface. The element comprises ducts or chambers which are arranged in said first layer or in between said first and second layer. Said ducts or chambers are arranged in fluid connection with said pervious material and are configured for feeding a pressurized fluid to the pervious material. At least the first layer is formed using a three-dimensional printing tool.