An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation. The aircraft has a blended wing body and includes first and second engines, a binary lift fan system, first and second forced air bypass systems and first and second exhaust systems. The engines have turboshaft and turbofan modes. The lift fan system includes ducted fans in a tandem longitudinal orientation. In the VTOL orientation of the aircraft, the engines are in the turboshaft mode coupled to the lift fan system such that the engines provide rotational energy to the ducted fans generating the thrust-borne lift. In the forward flight orientation of the aircraft, the engines are in the turbofan mode coupled to the forced air bypass systems such that the bypass air combines with the engine exhaust in the exhaust systems to provide forward thrust generating the wing-borne lift.

An aircraft operable to transition between thrust-borne lift in a VTOL orientation and wing-borne lift in a forward flight orientation. The aircraft has a blended wing body and includes first and second engines, a binary lift fan system, first and second forced air bypass systems and first and second exhaust systems. The engines have turboshaft and turbofan modes. The lift fan system includes ducted fans in a tandem longitudinal orientation. In the VTOL orientation of the aircraft, the engines are in the turboshaft mode coupled to the lift fan system such that the engines provide rotational energy to the ducted fans generating the thrust-borne lift. In the forward flight orientation of the aircraft, the engines are in the turbofan mode coupled to the forced air bypass systems such that the bypass air combines with the engine exhaust in the exhaust systems to provide forward thrust generating the wing-borne lift.

The embodiments herein disclose a retrofitted or in built or add-on kit/device for airborne vehicles to reduce the aerodynamic drag thereby increasing performance parameters/metrics of the vehicles. Drag reduction is achieved through shape/contour optimization, and/or heat/energy/fluid addition to the flow in neighbourhood of the vehicle. The device is designed with an external surface to offers the minimum drag. The device is configured to deposit heat/energy/fluid in neighbourhood of flying vehicle in several ways by generating/injecting hot gases in neighbourhood of vehicle for energy/heat addition, thereby causing maximum drag reduction. Heat/energy/fluid is added through the nozzles in the add-on kit/device.

A drag reduction device includes a first part and a second part. The first part is attached to the second part, and the second part is detachably attached to a body. The first part is made of a flexible material and configured to be able to change its shape under the action of a flow field. According to this application, through providing the drag reduction device on the body in need of drag reduction by detachably attaching the drag reduction device to the body, the need to modify the shape of the body itself is dispensed with. According to this application, the drag reduction device is very simple in structure and easy to assemble and disassemble, almost does not add weight to the body and has very low cost. According to this application, the drag reduction device is able to change its shape without consuming energy at all. Moreover, under different flow field conditions, it can assume different shapes that adapt it to the flow field conditions.

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.

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 aircraft is provided including a fuselage that extends along a longitudinal direction between a forward end and an aft end. A boundary layer ingestion fan is mounted to the fuselage at the aft end and is configured for ingesting boundary layer airflow off the surface of the fuselage. The fuselage defines a profile proximate the boundary layer ingestion fan that is optimized for ingesting a maximum amount of boundary layer air and improving propulsive efficiency of the aircraft. More specifically, the fuselage defines a cross sectional profile upstream of the boundary layer ingestion fan that has more cross sectional area in a top half relative to a bottom half as defined relative to a centerline of the boundary layer ingestion fan.

An aircraft is provided including a fuselage that extends along a longitudinal direction between a forward end and an aft end. A boundary layer ingestion fan is mounted to the fuselage at the aft end and is configured for ingesting boundary layer airflow off the surface of the fuselage. The fuselage defines a profile proximate the boundary layer ingestion fan that is optimized for ingesting a maximum amount of boundary layer air and improving propulsive efficiency of the aircraft. More specifically, the fuselage defines a cross sectional profile upstream of the boundary layer ingestion fan that has more cross sectional area in a top half relative to a bottom half as defined relative to a centerline of the boundary layer ingestion fan.

A fluid control system includes a deformable surface that covers a body in at least a first and second direction. The first direction is orthogonal to the second direction. The deformable surface includes a bottom side that faces the body and a top side that is opposite the bottom side. The fluid control system also includes at least one deformer between the deformable surface and the body. The at least one deformer is configured to modify a boundary layer of a fluid that is flowing over the deformable surface by selectively deforming the top side of the surface.

An aircraft surface cover is provided. The aircraft surface cover includes a cover member that is configured to be removably secured to an aircraft structure. The cover member includes an exterior surface that has a microtextured surface including microtexture ribs that are configured to improve aerodynamic performance of the aircraft structure.