GB2588131A

GB2588131A - Wind Tunnel model with movable component

Info

Publication number: GB2588131A
Application number: GB1914544.0A
Authority: GB
Inventors: Carnegie John
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2019-10-08
Filing date: 2019-10-08
Publication date: 2021-04-21
Anticipated expiration: 2039-10-08
Also published as: GB2588131B; GB201914544D0

Abstract

The present invention relates to a wind tunnel model, in particular a cryogenic wind tunnel model (100, fig 2). The model may be a model of an aircraft. The model (100) has a movable component 112 that is rotatably mounted to a fixed part 113 of the model (100). A plurality of movable pins 118A-D are housed in the fixed part 113. The movable component 112 has a corresponding plurality of pin receiving holes 116A-D. When one of the pins 118A-D is engaged with the corresponding pin receiving hole 116A-D, the movable component 112 is held in a fixed angular potion relative to the fixed part 113. Each pin receiving hole 116A-D extends, relative to the corresponding pin 118A-D, at a different angle. The angular position of the movable component 112 can be altered by changing the pin that is engaged with the movable component 112

Description

WIND TUNNEL MODEL WITH MOVABLE COMPONENT

1FCHNICAL FIELD

100011 The present invention concerns a model for use in a wind tunnel. More particularly, but not exclusively, this invention concerns a model of an aircraft for use in a cryogenic wind tunnel. The invention also concerns a method of moving a component part of such a model whilst the model remains in the wind tunnel.

BACKGROUND OF THE INVENTION

[0002] It is well known that a wind tunnel may be used to test the aerodynamic properties of an object. For large objects, such as aircraft, scale models may instead be tested. Conventional wind tunnels generate a flow of air that is passed over the object under test. In a conventional wind tunnel, it can be difficult to reach the Reynolds numbers experienced by aircraft during high-lift and high-speed flight. Thus it can be difficult to accurately simulate such flight conditions in conventional wind tunnels.

100031 Cryogenic wind tunnels are configured to test objects in a flow of gas cooled to cryogenic temperatures which allows high Reynolds numbers to be achieved. Hence, high-lift and high-speed flight may be simulated more accurately. Typically, nitrogen is used as the gas. Cryogenic temperatures may be defined as those below minus 150°C (123 Kelvin). In practice, some cryogenic wind tunnels may be operated at slightly warmer temperatures, such at 140 Kelvin. Thus, for the purpose of the present patent application, a cryogenic wind tunnel may be considered as a wind tunnel arranged to operate with a test gas (i.e. the gas flow in the tunnel) having a temperature at or below minus 100°C (173 Kelvin) [0004] An example cryogenic wind tunnel is the European Transonic Windtunnel in Cologne, Germany. The European Transonic Windtunnel can perform tests in a pure nitrogen flow at a temperature of 110 Kelvin, the nitrogen being driven through a closed aerodynamic circuit -2 - [0005] It may be desirable to test the aerodynamic properties of an object in a number of different configurations. For example, aircraft comprise movable control surfaces, such as ailerons, elevators and rudders. It may be desirable to test models of aircraft with the control surfaces in various different positions. However, it can be time consuming and expensive to warm up a wind tunnel and model, change the configuration of the model, and then cool the wind tunnel and model down again. Such a procedure may, for example, take three to four hours, possibly up to a day, and use large amounts of nitrogen gas and energy. The process also risks introducing contaminates into the wind tunnel fluid flow.

[0006] In the case of models of aircraft, it has been proposed to provide the models with control surfaces that can be remotely actuated while the model is in the wind tunnel. This may avoid having to warm up and cool down the wind tunnel and model in order to change the configuration of the model.

[0007] It has been proposed to actuate the control surfaces using electric motors.

However, electric motors typically need to be heated in order to operate in the low temperature environment of a cryogenic wind tunnel. Additionally, motors may not be able, by themselves, to hold the control surfaces in position under the loads applied during testing in the wind tunnel. Hence, an additional locking means may be required to hold the control surfaces in place.

[0008] It has also been proposed to actuate control surfaces of aircraft cryogenic wind tunnel models using Shape Memory Alloy (SMA) actuators. For example, see "Low and High Speed Cryogenic Testing of a Wind Tunnel Model with Remote Control Actuation (RCA)" Frederick T. Calkins et al. However, such solutions are not yet well developed.

[0009] The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved model for a cryogenic wind tunnel.

SUMMARY OF THE INVENTION

[0010] The present invention provides, according to a first aspect, a wind tunnel model comprising: a fixed body, a movable component rotatably-mounted to the fixed body, and -3 -a plurality of movable pins housed by the fixed body, each pin being movable along a pin axis; wherein the movable component comprises a plurality of pin receiving holes, wherein each of the pins has a corresponding pin receiving hole; wherein the wind tunnel model is arranged such that engagement of one of the pins with the corresponding pin receiving hole holds the movable component in one of a plurality of a discrete angular positions relative to the fixed body; wherein each of the pin receiving holes extends at a different angle to the pin axis of the corresponding pin such that each of the plurality of discrete angular positions is different; and wherein the model further comprises a pin actuation system operable to selectively move each of the pins: (i) into engagement with the corresponding pin receiving hole, and (ii) out of engagement with the corresponding pin receiving hole, such that the movable component may be caused to adopt any one of the plurality of discrete angular positions relative to the fixed body.

[0011] The present invention uses the engagement of a pin with a corresponding hole in the movable component to both cause a rotation of that component, and to hold the component in position relative to the fixed body. 'Ibis arrangement may be beneficial as the pins act as both an actuation means and a means to lock the component in position. This may mitigate the need for separate actuation and locking means, as may be the case, for example, when using an electric motor as the actuation means. Additionally, the component may only be held in a number of discrete angular position; therefore the arrangement may allow the position of the movable component to be accurately known, which can help provide meaningful wind tunnel test results.

[0012] Further, the arrangement of the present invention may, at least in the vicinity of the movable component, be relatively compact. This may be beneficial for use in parts of models which have limited space, in particular limited thickness, to accommodate an actuation mechanism. This may, for example, be the case in the wings of models of aircraft, where, at the outboard ends, near the aileron, the thickness can be around 1 Omm.

100131 The pin actuation system may be arranged to move the pins under the action of fluid pressure. The pin actuation system may be arranged to move the pins under the action of gas pressure. In other words, the pin actuation system may be a pneumatic pin actuation system. The gas may be nitrogen. The gas may be neon. The pin actuation system may be -4 -arranged to move the pins under the action of liquid pressure. In other words, the pin actuation system may be a hydraulic pin actuation system.

[0014] The use of fluid pressure may provide a convenient way to move the pins. In particular, it may minimise the componentry required in the vicinity of the movable component, where space may be limited. It may be possible for the larger/bulkier components associated with regulating the flow of fluid, for example including a valve arrangement (e.g. comprising solenoid valves) and/or control circuitry, to be positioned remotely from the movable surface. The pressurised fluid may be transported to the pins, for actuation of the pins, via conduits. For example, if the model is a model of an aircraft, the components associated with regulating the flow of fluid may be positioned within the fuselage of the model. This may be beneficial as there may be more available space in the fuselage, and it may be easier to keep the components warm (e.g. by using electrical heaters). The pressurised fluid may be transported from the fuselage to the pins by a series of conduits.

[0015] the pin actuation system may further comprise an apparatus, such as a pump, a compressor, and/or an accumulator, for pressurising the fluid The pressurisation apparatus may also be provided in the fuselage of the aircraft [0016] Each pin may comprise a piston portion against which the fluid pressure acts to cause movement of the pin. The pin actuation system may comprise a first conduit arranged to supply fluid to a first side of the piston so as to extend (or retract) the pin. The pin actuation system may comprise a second conduit arranged to supply fluid to a second side of the piston, opposite the first side, to retract (or extend) the piston. In alternative embodiments, a separate hydraulic or pneumatic actuator may be provided in order to move the pins.

100171 In alternative embodiments, the pins may be actuated by other means, such as by electric motors (e.g. linear motors and/or rotary motors), shape changing alloys, etc. A mechanical connection between the actuator and each pin may be provided. For example, the connection may comprise a screw drive, worm gear, linkages, and/or the like.

100181 Each pin may comprise a distal end for insertion into the corresponding pin receiving hole. The distal end of each pin may be tapered. The end may be tapered at an -5 -angle of 10 degrees or more, for example 25 degrees, from the longitudinal axis of the pin. The tapered end may help the pin insert into the corresponding pin receiving hole when, due to the rotational position of the movable component, the pin axis is misaligned with the pin receiving hole.

[0019] Each of the pin receiving holes may extend into the movable component at a different angle. Each pin receiving hole may comprise a cylindrical bore. Each pin receiving hole may comprise a longitudinal axis, which may be referred to as the hole axis. Each hole axis may extend at a different angle into the movable component. The angles may differ by 5 degrees. Each discrete angular position of the movable component may differ by 5 degrees of rotation.

100201 In embodiments, each of the pin receiving holes may have a tapered shape in the region, optionally the entire region, in which the pin engages. Accordingly, each of the pins, or at least the end regions thereof that engage with the corresponding pin receiving hole, may have an entirely tapered shape. The engaging surfaces of both the pin and the pin receiving hole may be tapered. In such embodiments, each pin may require a constant force to hold the pins in the engaged position against rotational loading on the aileron. Nevertheless, the pins may be more easily retracted as it may be less likely for the pins to become jammed in an extended position.

[0021] In alternative embodiments, the pin axis of each pin may be at a different angle and the hole axes may all be aligned. Regardless of precisely how the pins and pin receiving holes are arranged, importantly, the arrangement is such that the angular position of the movable component can be altered by changing the pin that is engaged with the movable component. In other words, the angular position of the movable component depends on which of the pins is engaged with its corresponding pin receiving hole. Fora given position of the movable component, the angle between the pin axis and the hole axis may be different for each pin and the corresponding pin receiving hole. For at least one pin and the corresponding hole, the angle between the pin axis and the hole axis can be zero.

[0022] Each hole axis may be orthogonal to the axis of rotation of the movable component. The axis of rotation of the movable component and each hole axis may intersect. -6 -

[0023] Each pin may be elongate. Each pin may be cylindrical. Each pin may be linearly movable along the pin axis. Each pin axis may be coaxial with a longitudinal axis of the pin. Each pin may have a shape, and the corresponding pin receiving hole may have a corresponding shape. The shapes may be such that each pin fits snugly within the corresponding pin receiving hole. Each pin may have the same form (e.g. be of the same shape and dimensions).

[0024] Each pin may have an extended position, in which the pin is engaged with the corresponding pin receiving hole. In the extended position, the pin may be extended at least far enough that the movable component is held in the corresponding discrete angular position relative to the fixed body. Each pin may have a retracted position, in which the pin is withdrawn from the corresponding pin receiving hole. In the retracted position, the pin may be withdrawn far enough that the position of the pin does not affect the ability of the movable component to adopt another of the discrete angular positions under the influence of another of the pins.

100251 the pin actuation system may comprise a resilient bias arranged to bias each pin towards the engaged position. The resilient bias may be a spring, for example a compression spring. The resilient bias may bear against the piston portion. In embodiments, pressure of fluid in the pin actuation system may act against the resilient bias to keep the pin disengaged from the corresponding pin receiving hole (i.e. to keep the pin in the retracted position).

[0026] The resilient bias may bias each pin into engagement with the corresponding pin receiving hole such that, in the retracted position of the pin, the tapered end portion at least partially protrudes into the pin receiving hole.

[0027] At certain angular positions of the movable component, not all of the pins may be able to successfully engage with their corresponding pin receiving hole. For example, a first pin may be engaged with the movable component so as to hold the movable component in a first angular position. In the first angular position, a second pin and the corresponding pin receiving hole may be too far misaligned for the second pin to successfully engage with the corresponding pin receiving hole. In such a situation, it may be necessary to first rotate the rotatable component to an intermediate angular position, by retracting the first pin and engaging an intermediate pin, in order for the second pin to be sufficiently well aligned with the corresponding pin receiving hole for successful engagement therewith.

[0028] Hence, the pin actuation system may be configured to move the movable component from a first of the plurality of discrete angular positions to a second of the plurality of discrete angular positions by moving the pins such that the movable component is held in at least one intermediate discrete angular position during movement from the first discrete angular position to the second discrete angular position.

100291 The pin actuation system may comprise a control system arranged to control actuation of the pins in response to an input from an operator that the movable component adopt a given discrete angular position. The control system may comprise a wireless communication system for wirelessly-receiving the input from the operator. In embodiments, the control system may control a valve arrangement that in turn controls a flow of fluid that actuates the pins.

[0030] The model may be a model of an aircraft. The movable component may be a control surface of the aircraft. The control surface may, for example, be an aileron, an elevator or a rudder. The fixed body may comprise a fuselage of the aircraft. The fixed body may comprise (a fixed part of) a wing of the aircraft. The movable component may comprise a landing gear of the aircraft. In such an embodiment, the landing gear may comprise an arm, for example an upwardly extending arm, with which the pins engage so as to cause movement of the landing gear.

[0031] The model may comprise a removable actuation module. The actuation module may be mountable, in a fixed positional relationship, to other fixed parts of the model. The movable component may be mounted to the actuation module. The actuation module may house the pins. The actuation module may contain fluid flow channels for actuation of the pins. It may be beneficial to mount the movable component to, and/or the pins in, a part which is removable from the remainder of the model so that the actuation system can be more easily serviced, repaired and/or replaced if required. For example, in embodiments where the wind tunnel model is a model of an aircraft, and the movable component was an aileron, the actuation module may be removably mountable within the wing of the aircraft model. -8 -

[0032] The wind tunnel model may be suitable for use in a cryogenic wind tunnel. The wind tunnel model may be a cryogenic wind tunnel model. It will be appreciated that for a wind tunnel model to be considered a cryogenic wind tunnel model the model must be capable of being tested, and providing meaningful test results, at cryogenic temperatures. For example, the materials used in the model must have sufficient strength and fracture toughness at cryogenic temperatures, machinability, and thermal expansion/contraction properties which allow the size and shape of the model to be predictably known once cooled to cryogenic temperatures. For example, the structures of the model which provide the aerodynamic surfaces that are exposed to the wind tunnel flow during testing may be made of maraging steel, preferably grade 200 and/or 250 maraging steel.

100331 The present invention provides, according to a second aspect, a wind tunnel comprising a wind tunnel model according any aspect of the present invention. The wind tunnel may be a cryogenic wind tunnel. The cryogenic wind tunnel may be a wind tunnel capable of testing the aerodynamic properties of the model at or below minus 100 Celsius (173 Kelvin). The cryogenic wind tunnel may be a wind tunnel capable of testing the aerodynamic properties of the model at or below minus 150 Celsius (123 Kelvin).

100341 The present invention provides, according to a third aspect, a method of reconfiguring a wind tunnel model. The wind tunnel model may be a wind tunnel model according to any aspect of the present invention.

[0035] The method comprises the steps of: providing the wind tunnel model in a first configuration in which a first of the pins is engaged with its corresponding pin receiving hole such that the movable component is held in a first of the discrete angular positions relative to the fixed body; using the pin actuation system to move the first pin out of engagement with its corresponding pin receiving hole; moving the movable component to a second of the discrete angular positions relative to the fixed body: using the pin actuation system to move a second of the pins into engagement with its corresponding pin receiving hole; and holding the movable component in the second discrete angular positon by the engagement of the second pin with its corresponding pin receiving hole, the wind tunnel model thereby assuming a second configuration. -9 -

[0036] Moving the movable component to the second of the discrete angular positions may comprise using the pin actuation system to move the second of the pins into engagement with its corresponding pin receiving hole so as to urge the movable component towards the second of the discrete angular positions relative to the fixed body. Thus, the interaction of the second of the pins and the corresponding pin may cause the movable component to move.

[0037] Moving the movable component to the second of the discrete angular positions may comprise moving the fixed body of the model with respect to the wind tunnel such that aerodynamic forces acting on the movable component cause the movable component to move to the second of the discrete angular positions. Moving the fixed body of the model with respect to the wind tunnel may comprise moving the fixed body so as to change the angle of attack of the model. In such methods, the aerodynamic forces may move the movable component to approximately the second of the discrete angular positions, and the engagement of the second of the pins with its corresponding pin receiving hole may provide a final positioning of the movable component with respect to the fixed body.

[0038] The method may be performed whilst the model is positioned in the wind tunnel. When the wind tunnel is a cryogenic wind tunnel, the method may be performed without warming the fluid in the cryogenic wind tunnel. The method may be performed whilst the model is exposed to low temperatures, e.g. temperatures at or below minus 100 degrees Celsius (173 Kelvin), or at or below minus 150 degrees Celsius (123 Kelvin). The method may be performed between tests of' the aerodynamic properties of the model, without entering the wind tunnel and/or without pumping gas, for example nitrogen, out of the wind tunnel.

[0039] The method may further comprise a step of slowing or stopping the flow of fluid in the wind tunnel. Preferably the flow is slowed or stopped prior to disengaging the first pin. The method may further comprise a step of accelerating the flow of fluid in the wind tunnel. Preferably the flow is accelerated after the movable component is securely held in the second angular position by the second pin.

100401 The present invention provides, according to a further aspect of the invention, a model of an aircraft for use in a cryogenic wind tunnel, the model comprising: a fixed -10 -body, and a control surface arranged to move relative to the fixed body; a fixed body, and a control surface arranged to move relative to the fixed body; wherein the control surface has a first position relative to the fixed body, the control surface being caused to adopt the first position by engaging a first pin housed by the fixed body with a first pin receiving hole in the control surface, the engagement causing the first pin and the first pin receiving hole to align; wherein the control surface has a second position relative to the fixed body, the control surface being caused to adopt the second position by engaging a second pin housed by the fixed body with a second pin receiving hole in the control surface, the engagement causing the second pin and the second pin receiving hole to align; and wherein the arrangement of the first pin and pin receiving hole and the second pin and pin receiving hole is such that the first position of the control surface is different to the second position of the control surface.

[0041] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

100421 The term 'of shall be interpreted as 'and/or' unless the context requires otherwise.

DESCRIPTION OF THE DRAWINGS

100431 Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: [0044] Figure 1 shows a side view of a wind tunnel model according to a first embodiment of the invention; [0045] Figure 2 shows a plan view of the wind tunnel model according to the first embodiment of the invention; 100461 Figure 3 shows a plan cross-sectional view of an actuation module and an aileron of the wind tunnel model according to the first embodiment of the invention, along with a side cross-sectional view along the line X-X; [0047] Figure 4 shows an exploded perspective view of the actuation module and the aileron of the wind tunnel model according to the first embodiment of the invention; [0048] Figure 5 shows an exploded perspective view, showing hidden lines, of the actuation module and the aileron of the wind tunnel model according to the first embodiment of the invention; [0049] Figure 6 shows a side view of the leading edge, a plan view, and four cross-sectional views of the aileron of the wind tunnel model according to the first embodiment of the invention; [0050] Figure 7 shows an enlarged cross-sectional view along the line D-D of the aileron of the wind tunnel model according to the first embodiment of the invention; 100511 Figure 8 shows a side view of a pin of the wind tunnel model according to the first embodiment of the invention; [0052] Figure 9 shows a plan cross-sectional view of the actuation module of the wind tunnel model according to the first embodiment of the invention, without any pins, springs or connectors; [0053] Figure 10 shows a perspective view of an actuation module and an aileron of a wind tunnel model according to a second embodiment of the invention; and [0054] Figure 11 shows a perspective cross-sectional view along the line Y-Y of the actuation module and the aileron of the wind tunnel model according to the second embodiment of the invention.

DETAILED DESCRIPTION

[0055] Figures 1 and 2 show a wind tunnel model 100 according to a first embodiment of the invention. The model 100 is a scale model of an aircraft and is suitable for use in a cryogenic wind tunnel. The model 100 comprises a fixed body comprising a fuselage 106. The fixed body is mounted to a generally conical sting 102 which projects, via the tail of the aircraft, into the fuselage 106. The sting 102 supports the model 100 in the wind tunnel. The model 100 is mounted to the sting 102 via a balance 104 provided inside the fuselage 106. The balance 104 measures the forces acting on the model 100 in the wind tunnel. In -12 -alternative embodiments, the model may be supported in different ways, for example via supports connected to the wings. It will, however, be understood that the fixed body is substantially fixed in place relative to the reference frame of the wind tunnel.

[0056] The model 100 further comprises a pair of wings 108. Each wing 108 comprises a fixed part 110 which is fixedly mounted to the fuselage 106. The fixed part 110 of the wing 108 therefore also forms a part of the fixed body of the model IOU. The wing 108 further comprises a movable component in the form of an aileron 112. The fixed part of the wing 110 comprises an actuation module 113 which is responsible for moving the aileron 112.

[0057] Figures 3 to 5 shows the aileron 112 and the actuation module 113 in further detail. The aileron 112 is rotatably mounted to the actuation module 113 via pivot pins 114 provided at the inboard and outboard ends of the aileron 112. The leading edge of the aileron 112 comprises four pin receiving holes I I 6A-D machined therein.

[0058] Figure 6 shows a series of cross sections though the aileron 112. Each pin receiving hole 116A-D extends into the aileron 112 at a different angle. Pin receiving hole 116A extends into the aileron 112 such that the longitudinal axis of the pin receiving hole 116A is substantially aligned with a line extending from the leading edge to the trailing edge of the aileron 112. The pin receiving holes 116B, 116C, and 116D extend into the aileron 112 at an angle of 5 degrees, 10 degrees and 15 degrees, respectively, from said line extending from the leading edge to the trailing edge of the aileron 112.

[0059] Figure 7 is an enlarged view of the pin receiving hole 116D showing the angle between the longitudinal axis 117 (hole axis) of the pin receiving hole 1 I 6D and the notional line 119 extending from the leading edge to the trailing edge of the aileron 112.

[0060] Four movable pins 118A-D are housed within the actuation module 113 Each pin 118A-D is provided within a chamber 120 (only one of which is labelled in Figure 3 for clarity) in the fixed part 110. Each pin 118A-D is movable within its chamber 120 between a retracted position and an extended position. In their retracted position, the pins 118A-D are contained within the fixed part 110, and do not project from the trailing edge of the actuation module 113. In Figure 3, the pins 118A-C are shown in their retracted position. In their extended position, the pins 118A-D project from the trailing edge of the -13 -actuation module 113 into their corresponding pin receiving hole 116A-D. In Figure 3, the pin 118D is shown in its extended position, and engaged with the pin receiving hole 116D.

[0061] Figure 8 shows one of the pins 118A in further detail. The pin 118A comprises a cylindrical shaft 122 having a tapered distal end 124. The tapered end 124 helps the shaft to engage with the corresponding pin receiving hole I I 6A, even if the pin 1 I 8A and the pin receiving hole 1 1 6A are misaligned. In use, the pin I I 8A moves parallel to the longitudinal axis 129 of the shaft 122.

100621 The pin 118A further comprises a piston portion 126 at a proximal end of the shaft 122. The piston portion 126 has an enlarged circumference compared to the shaft I 22. The piston portion 126 and the shaft 122 each comprises a cut-out 128, 130 for accommodating an 0-ring seal 132, 134.

100631 Each pin receiving hole 116A-D has a cylindrical shape corresponding to that of the shaft 122. The pins II 8A-D and pin receiving holes I I 6A-D are dimensioned such that each pin II8A-D fits snugly within its corresponding pin receiving hole 11 6A-D.

100641 When one of the pins 118A-D is engaged with its corresponding pin receiving hole 116A-D, the aileron 112 is held in a fixed angular position relative to the fixed part 110 of the wing 108. When one of the pins 118A-D is engaged with the corresponding pin receiving hole 116A-D, it is not possible to fully engage the other pins due to the misalignment of those pins 118A-D with their corresponding pin receiving hole 116A-D.

[0065] The model 100 comprises a pneumatic pin actuation system arranged to move the pins 118A-D under the action of gas pressure. In this embodiment, the gas used is nitrogen. The actuation module 113 comprises a pair of channels associated with each pin 11 8A-D. A first channel 136 is in fluid communication with a proximal side of each chamber 120. A second channel 138 is in fluid communication with a distal side of each chamber 120, A first connector 140 is associated with the first channel 136, and a second connector 142 is associated with the second channel 142. Flexible conduits (not shown) connected to the first connector 140 and the second connector 142 to a valve arrangement in the fuselage 106. Dowels 137 prevent fluid flow between the first channels 136 in the actuation module 113.

-14 - [0066] The valve arrangement and an associated control system control the supply of gas into each of the first and second channels 136, 138 so as to control the extension and retraction of each pin 118A-D, and thereby control the movement of the aileron 112. Commands are sent to the control system from a user positioned outside of the wind tunnel. In embodiments, the commands are sent wirelessly. A pump is also provided in the fuselage 106 to pressurise the gas.

[0067] Figure 9 shows the network of chambers 120 and channels 136, 138 in the actuation module 113 without the pins 118A-D and connectors 142, 144. Each of the first channels 136 is wider than the second channels 138 to allow the associated pin 118A-D to be inserted into the chamber 120 in which it moves in use.

100681 In order to extend, for example, the pin 116A, the pressure in the first channel 136 is increased relative to the pressure in the second channel 138 such that there is a net force acting on the piston portion 126 which urges the pin 11SA towards the pin receiving hole 116A in the aileron 112. In order to retract, for example, the pin 116A the pressure in the second channel 138 is increased relative to the pressure in the first channel 136 such that there is a net force acting on the piston portion 126 which urges the pin 118A away from the pin receiving hole 116A in the aileron 112. The 0-ring seal 132 prevents the flow of gas past the piston portion 126, and the 0-ring seal 134 prevents the loss of gas via the opening in the trailing edge of the actuation module 113 through which the pin 118A extends.

[0069] Each chamber 120 and first channel 136 also accommodates a compression spring 144 that is arranged to bear against the proximal end of the piston portion 126 of the pin 118A-D. Each compression spring 144 thereby urges the corresponding pin 11SA-D towards its extended position. The compression spring 144 helps speed up engagement of each pin 118A-D with the corresponding pin receiving hole 116 when required to move the movable component.

100701 The fixed body including the actuation module 113, and the aileron 112 are made of a maraging steel, which can cope better than other materials in the low temperature environment of a cryogenic wind tunnel.

-15 - [0071] In use, the configuration of the model 100 is changed by moving aileron 112 from a first angular position to a second angular position according to the following method. Firstly, the speed of gas flow in the wind tunnel is reduced to zero to remove the aerodynamic loading on the aileron 112. The valve arrangement is then operated such that the pressure in the second channel 138 of the presently engaged pin, say pin Ii 8D, is increased relative to the pressure in the first channel 136 of that pin. The pressure difference moves the pin I 1SD against the action of the spring 144 into a retracted position in which the distal end of the pin 118D does not project beyond the trailing edge of the actuation module 113.

[0072] After the pin ii 6D is withdrawn, a short delay of approximately 0.5 seconds is allowed. The valve arrangement is then operated such that the pressure in the first channel 136 of a second pin, say pin 118B, is increased relative to the pressure in the second channel 136 of that pin. This allows the pin 118B to move towards the aileron under the action of the gas pressure and the spring 144.

100731 After an initial movement, the tapered end of the pin 118B locates in the pin receiving hole 116B, and the outer surface of the pin 118B contacts the inner surface of the pin receiving hole 116B. The contact acts to urge the aileron 112 in a direction in which the longitudinal axis of the pin receiving hole 116B aligns with the longitudinal axis of the pin 118B such that the pin 118B can continue its extension into the pin receiving hole 116B.

[0074] As the pin continues to extend, the longitudinal axis of the pin receiving hole 116B becomes fully aligned with the longitudinal axis of the pin 11 8B. Once the axes are fully aligned, the aileron 112 can be said to have adopted a second angular position relative to the fixed part 110 of the wing 108, and the model 100 can be said to have adopted a second configuration. Once the pin 11811 is fully engaged with the pin receiving hole Ii 8B, the aileron is 112 is held in the second angular position.

100751 In some embodiments, it may, due to the angle of the aileron and the angles of the pin receiving holes, not be possible to withdraw the first pin (e.g. pin 118D) and extend the second pin (e.g. pin 118B) without first moving the aileron 112 to an intermediate position by extending, and then retracting, an intermediate pin (e.g. pin 118C).

-16 - [0076] In embodiments, the control unit is configured to automatically extend and retract consecutive intermediate pins when commanded by a user to move the aileron between two discrete angular positions which are not adjacent. For example, if commanded to move the aileron from the position associated with pin 118D being extended to the position associated with pin I I 8A being extended, the control unit may automatically cycle through extension and retraction of pins I I 8C, then I I 8B before extending pin I I 8A.

[0077] In an alternative method of use, the flow of gas in the wind tunnel is maintained, although perhaps the flow speed is reduced, when the pin 118D is retracted. The fixed body of the model 100 (i.e. the model IOU as a whole) is then moved relative to the wind tunnel so as to change the angle of attack of the fuselage 106 and the wing 108 relative to the fluid flow. The model 100 is moved such that the aerodynamic forces on the aileron 112 cause the aileron 112 to move relative to the fixed body such that the pin 118B is approximately aligned with the pin receiving hole Ii 6B. The pin Ii 8B is then extended into the pin receiving hole I I 6B to hold the aileron 112 in position, the engagement of the pin 118B into the pin receiving hole 116B providing the final alignment. 'The model 100 is then optionally moved to a further position relative to the wind tunnel for testing.

100781 Figures 10 and 11 show an actuation module 213 for a cryogenic wind tunnel model according to a second embodiment of the invention. The second embodiment differs from the first embodiment only in that the trailing edge of the aileron 213 in square, rather than tapered.

[0079] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0080] In some embodiments, the pins may be retracted under the action of fluid pressure and extended solely under the action of the spring. In alternative embodiments, the pins may be extended under the action of fluid pressure and retracted solely under the action of the spring.

-17 - [0081] In alternative embodiments, the pins may be actuated (retracted and/or extended) under the action of hydraulic pressure. In alternative embodiments, the pins may be actuated (retracted and/or extended) using electric motors.

[0082] In alternative embodiments, each pin is tapered in the region in which it engages with the aileron, and each pin receiving hole is tapered inwards as from the edge of the aileron.

[0083] Whilst the present invention has been illustrated with reference to a movable component in the form of an aileron on a model of an aircraft, it will be appreciated that the present invention may also be applicable to other moving parts of an aircraft (e.g. the rudder, elevators, landing gear, etc.) and (cryogenic) wind tunnel models of other objects (i.e. non-aircraft).

100841 Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments..

Claims

-18 -CLAIMSA wind tunnel model comprising: a fixed body, a movable component rotatably mounted to the fixed body, and a plurality of movable pins housed by the fixed body, each pin being movable along a pin axis; wherein the movable component comprises a plurality of pin receiving holes, wherein each of the pins has a corresponding pin receiving hole; wherein the wind tunnel model is arranged such that engagement of each pin with the corresponding pin receiving hole holds the movable component in one of a plurality of a discrete angular positions relative to the fixed body; wherein each of the pin receiving holes extends at a different angle to the pin axis of the corresponding pin such that each of the plurality of discrete angular positions is different; and wherein the model further comprises a pin actuation system operable to selectively move each of the pins: (i) into engagement with the corresponding pin receiving hole, and (ii) out of engagement with the corresponding pin receiving hole, such that the movable component may be caused to adopt any one of the plurality of discrete angular positions relative to the fixed body.
2 A wind tunnel model according to claim 1, wherein the pin actuation system is arranged to move the pins under the action of fluid pressure.
3. A wind tunnel model according to claim 2, wherein the pin actuation system is arranged to move the pins under the action of gas pressure.
4 A wind tunnel model according to claim 3, wherein the gas is nitrogen or neon.
-19 - 5. A wind tunnel model according to any of claims 2 to 4, wherein the pin comprises a piston portion against which the fluid pressure acts to cause movement of the pin.
6. A wind tunnel model according to any preceding claim, wherein the pin actuation system comprises a resilient bias arranged to bias each pin towards an engaged position in which the pin is in engagement with the corresponding pin receiving hole.
7. A wind tunnel model according to any preceding claim, wherein each pin comprises a distal end for insertion into the pin receiving hole, wherein the distal end of each pin is tapered.
8. A wind tunnel model according to any preceding claim, wherein the model is a model of an aircraft.
9. A wind tunnel model according to claim 8, wherein the movable component is a control surface of the aircraft, for example an aileron, an elevator or a rudder.
10. A wind tunnel model according to any preceding claim, wherein the pin actuation system is configured to move the movable component from a first of the plurality of discrete angular positions to a second of the plurality of discrete angular positions by moving the pins such that the movable component is held in at least one intermediate discrete angular position during movement from the first of the discrete angular positions to the second of the discrete angular positions.
11. A wind tunnel model according to any preceding claim, wherein the wind tunnel model is suitable for use in a cryogenic wind tunnel.
12. A wind tunnel comprising a wind tunnel model according to any preceding claim.
13. A wind tunnel according to claim 12, when dependent on claim 11 wherein the wind tunnel is a cryogenic wind tunnel.
-20 - 14. A method of reconfiguring a wind tunnel model according to any preceding claim; the method comprising the steps of: providing the wind tunnel model in a first configuration in which a first of the pins is engaged with its corresponding pin receiving hole such that the movable component is held in a first of the discrete angular positions relative to the fixed body; using the pin actuation system to move the first pin out of engagement with its corresponding pin receiving hole; moving the movable component to a second of the discrete angular positions relative to the fixed body; using the pin actuation system to move a second of the pins into engagement with its corresponding pin receiving hole; and holding the movable component in the second discrete angular positon by the engagement of the second pin with its corresponding pin receiving hole, the wind tunnel model thereby assuming a second configuration.
15. A method according to claim 14, wherein moving the movable component to the second of the discrete angular positions comprises using the pin actuation system to move the second of the pins into engagement with its corresponding pin receiving hole so as to urge the movable component towards the second of the discrete angular positions relative to the fixed body.
16. A method according to claim 14 or claim 15, wherein moving the movable component to the second of the discrete angular positions comprises moving the fixed body of the model with respect to the wind tunnel such that aerodynamic forces acting on the movable component cause the movable component to move to the second of the discrete angular positions.
-21 - 17. A method according to any of claims 14 to 16, wherein the method is performed in a cryogenic wind tunnel, the model being at a temperature below minus 100 degrees Celsius.
18. A model of an aircraft for use in a cryogenic wind tunnel, the model comprising: a fixed body, and a control surface arranged to move relative to the fixed body; wherein the control surface has a first position relative to the fixed body, the control surface being caused to adopt the first position by engaging a first pin housed by the fixed body with a first pin receiving hole in the control surface, the engagement causing the first pin and the first pin receiving hole to align, wherein the control surface has a second position relative to the fixed body, the control surface being caused to adopt the second position by engaging a second pin housed by the fixed body with a second pin receiving hole in the control surface, the engagement causing the second pin and the second pin receiving hole to align; and wherein the arrangement of the first pin and pin receiving hole and the second pin and pin receiving hole is such that the first position of the control surface is different to the second position of the control surface.