FLUID DRAG MEASURING METHOD AND DEVICE

Abstract

Method and device for measuring fluid drag exerted by a flow-medium on a surface of an object by providing a testing device for measuring fluid drag exerted by a flow-medium on a surface, a suspension system for suspending an object having a surface, a setup for measuring fluid drag exerted by a flow-medium on a surface of an object, a computer readable medium, and a kit of parts for building a testing device.

Claims

1. A method for measuring fluid drag exerted by a flow-medium on a surface (2) of an object (20), the fluid drag being the result of movement of the flow-medium along said surface (2), the method comprising the steps of: a. suspending the object (20) within a measurement chamber, and at a distance from a base surface of the measurement chamber; b. providing a boundary layer of a flowing medium over the surface (2); and c. measuring at least one force resulting from the fluid drag.

2. The method of claim 1, wherein step c further comprises receiving data from one or more sensors (4) and processing said data.

3. The method of claim 1 or 2, wherein the method further comprises receiving data from at least one pressure sensor (41) and wherein the method preferably further comprises the step of correcting the measurement at step c. based on the data from the at least one pressure sensor (41).

4. The method of any preceding claim, wherein the object (20) is a plate; a sheet; or substantially plate or sheet shaped.

5. The method of any preceding claim, wherein the fluid drag is composed of at least 20%, preferably at least 60%, more preferably at least 80% of skin friction.

6. The method of any preceding claim, wherein step b. comprises diverting a boundary layer of the flowing medium from a base surface of the measurement chamber to the object surface (2), preferably by providing a ramp (500) upstream of the object surface (2).

7. The method of any preceding claim, wherein the base surface of the measurement chamber is absent any recesses or openings for receiving the object upon which fluid drag is measured.

8. The method of any preceding claim, wherein the object (20) is not positioned in a recess or opening in the measurement chamber base surface during steps a. through c.

9. The method of any preceding claim, wherein the measurement chamber is a wind-tunnel.

10. Testing device (1) for measuring fluid drag exerted by a flow-medium on a surface (2) of an object (20), the testing device (1) comprising: a. a body (3) for retaining the object (20); b. one or more sensors (4), arranged to measure force exerted on the surface (2); and c. a flow diverter (5).

11. The testing device (1) of claim 10, wherein the body (3) has a recess for receiving the object (20) such that the surface (2) is substantially flush with a periphery of the recess.

12. The testing device (1) of claim 10 or 11, wherein the height of the body (3) is at most about 20%, preferably at most about 10%, more preferably at most about 5%, even more preferably at most about 3% of the length of the body (3).

13. The testing device (1) of any of claims 10 to 12, wherein the body (3) further comprises a support plate (38) disposed within the body (3) arranged to support the object (20) when placed in the body (3).

14. The testing device (1) of any of claims 10 to 13, wherein the testing device (1) further comprises a flow-medium velocity sensor (42), wherein the velocity sensor (42) preferably is moveable in a direction perpendicular to the surface (2), wherein more preferably, the velocity sensor (42) is attached to a stanchion (310), said stanchion being attached to the upper side of the body (3).

15. The testing device (1) of any of claims 10 to 14, further comprising at least one interbody-surface pressure sensor disposed between the surface (2) and the body, wherein preferably the testing device (1) comprises at least 3, preferably at least 5, more preferably at least 10, even more preferably at least 20 interbody-surface pressure sensors, arranged to measure a pressure profile within the body.

16. The testing device (1) of any of claims 10 to 15, wherein the flow diverter (5) is a ramp (500).

17. The testing device (1) of any of claims 10 to 16, wherein the body (3) further comprises body sides (32, 33), wherein the testing device (1) further comprises at least one lateral flow guide (502, 503) having a side ramp top surface (510) arranged to decrease fluctuations of the boundary layer at the region of the body sides (32, 33).

18. The testing device (1) of any of claims 10 to 17, wherein the testing device (1) further comprises an anchoring unit (300), said anchoring unit (300) being connected to the underside of the body (3), said anchoring unit (300) being arranged to limit the movement of the body (3) relative to a base surface of a measuring chamber.

19. The testing device (1) of any of claims 10 to 18, wherein the ramp is at least partially a super-ellipse in cross-section.

20. The testing device (1) of any of claims 10 to 19, wherein the testing device (1) further comprises a suspension system (6), preferably comprising at least one leaf spring system (60) comprising a support body (601) and a static body (602), the support body (601) and the static body (602) being connected via at least one leaf spring (603).

21. The testing device (1) of any of claims 10-20 further comprising a test object (20) retained by the body (3).

22. A suspension system (6) for the testing device of any of claims 10-21, comprising at least one leaf spring system (60) comprising a support body (601) and a static body (602), the support body (601) and the static body (602) being connected with at least one leaf spring (603), arranged to allow movement in a first direction (604) while limiting movement in a second direction (605), the second direction being perpendicular to the first direction, preferably wherein the first direction (604) coincides with the direction of movement of a flow-medium and wherein the second direction (605) coincides with the direction of gravity.

23. The suspension system (6) of claim 22, connecting one side of the static body (602) with one side of the support body (601), wherein the suspension system (6) preferably couples an object (20) having a surface (2) and a transportation apparatus, wherein the surface (2) of the object forms at least a section of a surface area of said transportation apparatus.

24. A setup for measuring fluid drag exerted by a flow-medium on a surface (2) of an object (20), the fluid drag being the result of movement of the flow-medium along a direction of the surface (2), the setup comprising: a testing device (1) according to any of claims 10 to 21; a chamber for supplying a controlled flow of a flow-medium, preferably a wind tunnel.

25. Computer readable medium having computer readable instruction stored thereon that, when executed by a processor of an apparatus according to any of claims 10 to 21 causes the apparatus to measure forces exerted on a surface.

26. A kit of parts for building a testing device (1) according to any of claims 10 to 21, comprising: a. a body (3) as described in any of claims 10 to 21; b. one or more force sensors (4) as described in any of claims 10 to 21; c. a flow-diverter (5) as described in any of claims 10 to 21; and d. a suspension system (6) as described in any of claims 10 to 23.

27. The kit of parts according to claim 21 wherein the kit of parts further comprises: a. one or more pressure sensors (41) as described in claims 10 to 21; and/or b. a processing unit (7); and/or c. a flow-medium velocity sensor (42); and/or d. a pressure sensor, preferably a pitot tube.

28. The kit of parts according to claim 27 or 28, wherein the kit of parts has a weight of at most about 500 kg, preferably at most about 300 kg, more preferably at most about 100 kg, still more preferably at most about 50 kg.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The features and advantages of the invention will be appreciated upon reference to the following drawings, in which:

[0063] FIG. 1 is an isometric exploded view of one embodiment of the invention showing the testing device;

[0064] FIG. 2 is an isometric view of one embodiment of the invention showing the testing device;

[0065] FIG. 3 is a plan view of one embodiment of the invention showing the suspension system;

[0066] FIG. 4 is a flow chart illustrating a method for measuring fluid drag in some embodiments according to the present disclosure;

[0067] FIG. 5 is a schematic diagram illustrating the processing of measured parameters; and

[0068] FIG. 6 is a side view of one embodiment of the invention showing the testing device.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0069] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the drawings.

[0070] Referring to FIG. 1, a testing device 1 for measuring fluid drag exerted by a flow-medium on a surface 2 is shown. The testing device comprises a body 3 for retaining a surface 2 to be tested. The surface 2 is the top surface 2 of an object 20. The object 20 is a plate-shaped structure in the illustrated embodiment, the geometry of which is in accordance with the shape of the body 3 in such a way that the object 20 may closely be received in the recess defined by the body 3. The body 3 may have wider dimensions to minimize disturbances of the boundary layer. In the shown embodiment, the body 3 is substantially cuboid, having a body front 30, a body rear 31 and body sides 32, 33. The body 3 defines a recess for receiving the object 20 with the surface 2 therein. The flow-medium flows through the measuring chamber along the length of the body 3, between the body front 30 and the body rear 31. The body front 30 is positioned upstream from the body rear 31.

[0071] Force sensors 4 are disposed within the body 3 of the testing device 1 and are arranged to measure force exerted on the surface 2. The surface 2 to be tested exerts a force to the force sensors 4 in the flow-direction of the flow-medium. In the illustrated embodiment, the surface 2 exerts a force to the force sensors 4 in an indirect manner as the object 20 having the surface 2 is disposed on a support plate 38, which engages with the force sensors 4. The support plate 38 may be generally the same shape as the object 20 and with the body 3. The support plate 38 protects the internal components of the testing device 1 such as the force sensors 4, the electronics, and other delicate components of the testing device 1.

[0072] The testing device 1 in the illustration further comprises a flow diverter 5 positioned upstream of the body 3 which diverts a boundary layer from the floor 11 of the measuring chamber to the surface 2 of the object 20. The flow diverter 5 in this embodiment is a ramp 5, having a super-elliptical shape. The ramp 5 ensures that the boundary layer is diverted to the surface 2 while minimizing the effects of the diversion so that the boundary layer arriving at the surface 2 is substantially equal to the boundary layer on the floor 11 of the measurement chamber upstream from the testing device.

[0073] The ramp has a ramp rear 53 which corresponds to the body height as measured at the body front 30, so that the surface of the ramp 5 and the surface 2, when disposed in the recess of the body 3 are flush. The ramp 5 is shown separate from the body 3. The body front 30 comprises body attachment units 37, arranged to connect the body front 30 to the ramp 5. The attachment units 37 allow for easy connection between the body front 30 and the ramp 5. The attachment units 37 may also be positioned on the body sides 32, 33 for attachment of lateral flow guides and may be positioned on the body rear 31.

[0074] In this embodiment, the testing device 1 further comprises a body-extension 39, provided downstream from the body 3. The body-extension 39 is shown to be connected to the body rear 31 with body attachment units 37.

[0075] The testing device 1 is further shown to comprise an anchoring unit 300 being arranged to limit movement of the testing device 1 in the measurement chamber. The anchoring unit 300 is attached to the underside of the body 3 of the testing device 1 and may further allow for the transmittance of data through the anchoring unit 300, which may be partially hollowed in such an embodiment. The anchoring unit 300 may traverse through an opening 12 in the wall 11 or floor 11 of a measurement chamber.

[0076] Referring to FIG. 2, a testing device 1 for measuring fluid drag exerted by a flow-medium on a surface 2 is shown. The object 20 having the surface 2 is disposed inside the recess of the body 3 of the testing device 1 in this illustration. In addition to the components shown in FIG. 1, the testing device 1 is shown to further comprise a stanchion 310 extending from a rear portion of the body 3 of the testing device 1. The stanchion 310 comprises a pressure sensor 41 and a velocity sensor 42. The pressure sensor 41 is positioned at the top of the stanchion and is arranged to determine the characteristics of the flow within the measurement chamber. The velocity sensor 42, in this embodiment depicted as a hotwire, extends substantially parallel to the surface 2 of the object 20 and is arranged to measure the velocity of the boundary layer at various points across the thickness of the boundary layer. To achieve this, the velocity sensor 42 is moveable in a direction perpendicular to the surface 2, along the stanchion 310.

[0077] Referring to FIG. 3, an embodiment of the suspension system 6 for suspending the surface 2 is shown. The plan view of the suspension system 6 shows a static body 602 surrounding a support body 601, the static body 602 and the support body 601 being connected by four leaf springs 603. The leaf springs 603 are positioned in two lengths of two leaf springs 603 in series with a thickened material between the two leaf springs 603. The thickened material allows for a higher rigidity in a first direction while the thin leaf springs 603 allow for a higher flexibility in a second direction. Alternatively, the static body 602 and the support body 601 may be connected by means of a single or two leaf springs 603. In principle, any number of leaf springs 603 allows for a functioning suspension system 6.

[0078] Referring to FIG. 4, a method for measuring fluid drag exerted by a flow-medium on a surface 2 of an object 20 is shown, the fluid drag being the result of movement of the flow-medium along a direction of said surface 2. The method is shown to comprise the steps of suspending the object 20 having the surface 2 above a floor 11 of a measurement chamber; diverting a boundary layer to the level of the surface 2; and measuring the forces resulting from the fluid drag.

[0079] Referring to FIG. 5, a schematic diagram illustrating the processing of measured parameters is shown. The testing device 1 may comprise a processing unit 7 which receives data from one or more from the force sensors 4 and/or the pressure sensors 41 and/or the velocity sensors 42. The processing unit 7 uses this data to determine the fluid drag exerted on the surface 2 and collects information about the circumstances under which said fluid drag was measured such as the pressure and velocity of the flow-medium. The procession unit 7 may optionally send this data to a reading device 71 which depicts the results of the measurement. Alternatively, the processing unit 7 may store said information without transmitting the results to the reading device 71.

[0080] Referring to FIG. 6, a side view of an embodiment of the testing device 1 is shown, in relation to the floor or wall 11 of the measurement chamber, the floor or wall 11 having an opening 12. The illustrated embodiment comprises a body 3, coupled to a ramp 5 and a body extension 39. A stanchion 310 having a pressure sensor 41 and a velocity sensor 42 is attached to the body 3 of the testing device 1. The testing device 1 further comprises an anchoring unit 300 traversing through an opening 12 of the wall 11 of the measurement chamber. A gasket 13 ensures a substantially airtight fit between the body 3 of the testing device 1 and the wall 11 of the measurement chamber.

[0081] The invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

[0082] Further modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.