Device and method for determining at least one parameter of a flow of a fluid

A device (10) for determining a parameter of a fluid flow includes an elastically deformable boom (23, 28, 33, 42, 47), with an inflow area (29, 31, 32, 37, 38, 39, 40, 44, 45, 46, 49, 50) for fluid and a measurement apparatus (16) measuring deformation of the boom. A section of the inflow area is aligned askew and/or curved to a main fluid inflow direction (25). The boom has an inflow structure (24, 30, 34, 43, 48) on one free end. The inflow structure has the fluid inflow area. To determine the parameter of the fluid flow at high resolution, in particular a high angle resolution, the boom has a reflection surface (27) on a side facing away from the inflow structure and the measurement apparatus (16) has a laser (17). A beam axis (26) of the laser (17) is directed to the reflection surface (27) of the boom.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a United States National Phase Application of International Application PCT/EP2016/050457, filed Jan. 12, 2016, and claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2015 000 064.0, filed Jan. 12, 2015, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a device for determining at least one parameter of a flow of a fluid comprising an elastically deformable cantilever, which has at least one incoming flow surface for the fluid, and comprising a measuring device for measuring the deformation of the cantilever, wherein at least one section of the incoming flow surface is aligned obliquely and/or curved to a main incoming flow direction of the fluid, the cantilever has an incoming flow structure at one free end, and the incoming flow structure has the at least one incoming flow surface for the fluid. Furthermore, the present invention pertains to a method for determining at least one parameter of a flow of a fluid, especially with a device according to the present invention, in which an elastically deformable cantilever with at least one incoming flow surface for the fluid is inserted into a flow, and in which the deformation of the cantilever is measured with a measuring device based on the forces of the flow acting on the incoming flow surface, wherein at least one section of the incoming flow surface is aligned obliquely and/or curved to a main incoming flow direction of the fluid, the cantilever has an incoming flow structure at one free end, and the incoming flow structure has the at least one incoming flow surface for the fluid.

BACKGROUND OF THE INVENTION

Such a device and such a method are known from FR 2 764 066 A1.

Furthermore, a device and a method without an oblique and/or curved alignment of a section of the incoming flow surface to the main incoming flow direction of the fluid are known from the scientific article “New anemometer for offshore use,” J. Puczylowski, J. Peinke and M. Hölling, Journal of Physics: Conference Series 318 (2011) 072015.

Parameters of a fluid flow, especially a velocity and/or flow direction of a fluid, can be determined by means of a corresponding device. For this, the cantilever can be exposed to a flow, wherein, due to the moving fluid, a force acts on the cantilever. This force leads to a deformation, especially to a bending and/or torsion, of the cantilever. The desired information, especially about the velocity and/or a contact angle, of the fluid are contained in the deformation. This information can be determined by means of various, already available methods. The so-called laser pointer principle, especially known from atomic force microscopy, is preferably used.

One drawback of the prior-art device is that the angular resolution is limited. Therefore, the basic object of the present invention is to further develop a device and a method of the type mentioned in the introduction such that the at least one parameter of the fluid flow to be determined can be determined at a higher resolution, especially at a higher angular resolution.

SUMMARY OF THE INVENTION

A basic object of the present invention is accomplished by means of a device and a method of the type mentioned in the introduction, in which the cantilever has a reflecting surface on a side facing away from the incoming flow structure and the measuring device has a laser, wherein a beam axis of the laser is or becomes directed at the reflecting surface of the cantilever.

In this case, it is advantageous that because of the oblique and/or curved arrangement of at least one section of the incoming flow surface to a main incoming flow direction of the fluid, a higher angular resolution can be obtained in relation to the at least one parameter of the fluid flow to be determined. In particular, a velocity and/or a flow direction of a fluid can be determined at a higher angular resolution. Thus, a present oblique component or transverse component of the flow to the main incoming flow direction of the fluid can be detected and resolved better.

Within the scope of the present invention, the main incoming flow direction of the fluid may be preset as a mean and/or average flow direction of the fluid. In particular, an incoming flow angle of 0° is associated with the main incoming flow direction of the fluid. The flow directions and/or incoming flow angle of the fluid to be determined can be distributed in an angle range of −45° to +45°, especially preferably from −90° to +90°, in relation to the incoming flow angle, especially by the incoming flow angle of 0° and/or the main incoming flow direction of the fluid. The flow directions and/or incoming flow angle of the fluid to be determined are preferably distributed uniformly, mirror-symmetrically and/or equally about the main incoming flow direction of the fluid.

According to another embodiment, a plane and/or a tangent of a curvature of the incoming flow surface is aligned obliquely to the main incoming flow direction of the fluid. In particular, a plurality of tangents of a curvature of the incoming flow surface are aligned obliquely to the main incoming flow direction of the fluid. Because of the oblique arrangement of a plane of the incoming flow surface and/or of at least one tangent of a curvature of the incoming flow surface to the main incoming flow direction, improved response characteristics of the cantilever can be obtained. Improved response characteristics with regard to an oblique component and/or a transverse component of the flow of the fluid obliquely, especially at right angles, to the main incoming flow direction of the fluid are preferably obtained. A stronger torsion of the cantilever can preferably be achieved by means of the oblique and/or curved alignment of the incoming flow surface to the main incoming flow direction. The plane and/or the tangent of the curvature of the incoming flow surface can be aligned obliquely to a longitudinal axis of the device. An oblique alignment of at least one section of the incoming flow surface is preferably defined within the framework of the present invention as an alignment of a plane and/or of a tangent of a curvature of the incoming flow surface in relation to the main incoming flow direction at an angle of less than 90°, especially in the range of 40° to 50°, and especially preferably 45°.

According to a variant, the measuring device has a laser. A plane and/or a tangent of a curvature of the incoming flow surface can be aligned obliquely to a beam or to a beam axis of the laser. The measuring device may have a reflecting surface for the laser. In particular, a plane of the reflecting surface for reflecting the laser beam is aligned obliquely to the beam axis of the laser. The beam axis of the laser is preferably directed at the reflecting surface of the cantilever. The beam axis of the laser may impact obliquely and/or at a right angle to the plane of the reflecting surface, especially in an unloaded state of the cantilever. In an unloaded state of the cantilever, no force of a flow of the fluid is preferably acting on the cantilever. In particular, the reflecting surface is arranged on a side of the cantilever facing away from the incoming flow surface. The reflecting surface is preferably arranged in an area of one free end of the cantilever. In particular, the reflecting surface has a material reflecting the beam of the laser. For example, the reflecting surface may be made of aluminum.

The at least one section of the incoming flow surface, a plane of the at least one incoming flow surface and/or a tangent of a curvature of the at least one incoming flow surface may be aligned obliquely to the main incoming flow direction of the fluid at an angle in the range of 35° to 55°, especially in a range of 40° to 50°, and preferably at an angle of 45°. As an alternative or in addition, a corresponding alignment can be aligned obliquely to a longitudinal axis of the device and/or obliquely to a beam axis of a laser of the measuring device.

According to another embodiment, the cantilever is associated with a carrier structure. The cantilever may be fastened to the carrier structure and/or to a sensor element arranged on the carrier structure. The cantilever and the carrier structure preferably form a sensor element. The sensor element, the cantilever and/or the carrier structure may be made of silicon or stainless steel. The cantilever preferably has a rod-like and/or plate-like configuration. In particular, the incoming flow surface of the cantilever has a rectangular configuration. The cantilever may be fastened with a first end to the carrier structure. Starting from the carrier structure, the cantilever can extend away from the carrier structure. In particular, the cantilever has one free end facing away from the carrier structure. The cantilever may have a length of up to 2 mm, especially a length in the range of 100 μm to 250 μm. The cantilever preferably has a width of up to 0.5 mm, especially a width in the range of 20 μm to 60 μm. The cantilever especially preferably has a thickness of up to 30 μm, especially a thickness in the range of 1 μm to 3 μm. A horizontal and/or transverse velocity and/or an incoming flow angle component can be determined by means of the cantilever. In particular, a spatial resolution in the range of 1 mm and/or a temporal resolution in the range of 1 kHz and/or higher can be obtained. In particular, velocity components and/or angle components can be determined on size scales below 1 mm and/or in the frequency range above 50 kHz.

According to a variant, the cantilever has an incoming flow structure at one free end. The cantilever and/or the incoming flow structure preferably has a fluid-dynamic profile. As a result, the response characteristics of the cantilever with regard to a deformation, especially a bending and/or torsion, can be improved. In particular, the fluid-dynamic profile is configured for producing a dynamic lift when the fluid is flowing about it. As a result, a suction action can be obtained on one side of the cantilever and/or of the incoming flow structure facing away from the incoming flow surface. A pressing action can be obtained in the area of the incoming flow surface. Thus, a higher force can act on the cantilever to deform the cantilever.

The incoming flow structure preferably has the at least one incoming flow surface for the fluid. In particular, the cantilever may have a first incoming flow surface, and the incoming flow structure may have at least one additional incoming flow surface. The incoming flow structure may have a plurality of additional incoming flow surfaces, especially two, three, four or more additional incoming flow surfaces. The at least one additional incoming flow surface preferably extends starting away from the first incoming flow surface. In particular, a section and/or a plane of the first incoming flow surface of the cantilever is aligned obliquely or at right angles to a section, a plane and/or a tangent of a curvature of the at least one additional incoming flow surface of the incoming flow structure. As a result, the response characteristics of the cantilever with regard to a torsion of the cantilever can be improved based on a force of the flow of the fluid acting on the first incoming flow surface and/or the at least one additional incoming flow surface.

The incoming flow structure may be produced from a photoresist, preferably SU-8. The incoming flow structure may have a height of up to 0.5 mm, especially a height in the range of 20 μm to 60 μm. The incoming flow structure preferably has a length of up to 0.5 mm, especially a length in the range of 20 μm to 60 μm. The incoming flow structure especially preferably has a thickness of up to 50 μm, especially a thickness in the range of 6 μm to 12 μm.

According to another embodiment, the incoming flow structure has an essentially V-shaped configuration. In this case, the incoming flow structure may selectively have two legs or be configured as a wedge-like structure. The cantilever preferably has a first incoming flow surface and the V-shaped incoming flow structure extends away starting from the first incoming flow surface. In particular, the incoming flow structure is facing the main incoming flow direction of the fluid. A section of the incoming flow surface, a first incoming flow surface and/or at least one additional incoming flow surface is preferably facing the main incoming flow direction of the fluid. The V-shaped incoming flow structure may open in a funnel-like manner in a direction away from the first incoming flow direction. As an alternative, the V-shaped incoming flow structure may form a ramp, a wedge, a ramp-like and/or wedge-like tip or needle directed away from the first incoming flow surface.

According to a variant, the measuring device has a beam splitter plate and/or a beam splitter membrane. A corresponding beam splitter is preferably arranged in a beam path for a beam of a laser. In particular, such a beam splitter is used for diffracting and/or deflecting a beam reflected on the reflecting surface in the direction of a detector. The measuring device preferably has an especially two-dimensional, position-sensitive detector for detecting a position of a beam of the laser reflected by the cantilever and/or the reflecting surface. The beam splitter is preferably configured as a pellicle beam splitter. The so-called ghosting can be avoided by means of such a beam splitter. Undesired multiple reflections occur in case of ghosting. The position-sensitive detector (PSD) makes it possible to determine the point of impact of the reflected beam on a two-dimensional measuring surface of the detector. The position of the point of impact on the detector is indicative of the torsion and/or bending of the cantilever. This information is indicative of the velocity, the flow direction and/or the incoming flow angle of the fluid.

According to another embodiment of the method according to the present invention, the deformation of the cantilever occurs because of a bending and/or torsion of the cantilever because of the forces of the flow of the fluid acting on the at least one incoming flow surface. Here, the velocity can be evaluated as a function of the bending, and/or the flow direction, especially an incoming flow angle, can be evaluated as a function of the torsion of the cantilever. In this connection, an angle range of +45° to −45°, especially of +90° to −90°, in relation to the main incoming flow direction of the fluid is preferably covered.

A device according to the present invention and/or a method according to the present invention for determining at least one parameter of a flow of a fluid, especially of a velocity, and/or of a flow direction of the fluid is especially advantageous. A longitudinal and/or a transverse velocity component can preferably be determined. In this case, the longitudinal velocity component may be aligned parallel to the main incoming flow direction of the fluid and/or may correspond to a velocity component in the main incoming flow direction. The transverse velocity component may be aligned obliquely, especially at right angles, to the longitudinal velocity component and/or to the main incoming flow direction. In particular, a two-dimensional measurement of the at least one parameter to be determined is made possible. The fluid may be a gas or a liquid. In particular, the device is configured as a cantilever anemometer, preferably as a two-dimensional laser cantilever anemometer (2d-LCA). The device according to the present invention and/or the method according to the present invention may be used in research, air and/or space travel, wind energy, medicine and/or in connection with mixing and/or combustion processes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings,FIG. 1shows a schematic perspective partial view of a device10according to the present invention. According to this partial view, a housing55of the device10is partly open or removed, so that an internal construction of the device10, which is usually enclosed by the housing55shown as not closed here, can be seen.

In this exemplary embodiment, the device10has an essentially oblong or elongated, especially pin-like, shape. The device10has a back end11and a front end12. The front end12has a conical housing tip13. The conical housing tip13has an angle, which is about 24° in this exemplary embodiment, opening in the direction of the back end11. The housing tip13has a rod-like carrier structure fastened on the outer circumference, which carrier structure projects over the end of the housing tip13running in the direction of the front end12. A sensor element15, which protrudes beyond the housing tip13in a direction facing away from the back end11, is arranged at one free end of the carrier structure14. The sensor element15has an elastically deformable cantilever that cannot be seen in more detail here, which will be shown and explained in detail in connection with the following figures.

A measuring device16for measuring the deformation of the cantilever of the sensor element15is arranged between one end of the housing tip13facing away from the carrier structure14or from the sensor element15and the back end11. The measuring device16has a laser17, which is arranged in a central area of the device10in this exemplary embodiment. Here, the laser17is configured, for example, as a laser diode of the type ADL-63054TA2 having a wavelength of 630 nm and a power of 5 mW.

A positioning device18for positioning or adjusting the laser17is arranged between the back end11of the device10and the laser17. In this exemplary embodiment, the laser17can be adjusted by means of the positioning device18and a remote control, not shown in more detail here, as a result of which an opening of the housing55of the device can be avoided. According to this exemplary embodiment, the positioning device18for positioning or adjusting the laser17has two DC motors.

A beam splitter19and a position-sensitive detector20are arranged between the laser17, which is aligned with regard to its laser beam, which is not shown in more detail here, such that the laser beam impacts the cantilever of the sensor element15, and the housing tip13. The position-sensitive detector20is configured here as a two-dimensional component, namely as a so-called two-dimensional position-sensitive detector (PSD). A detector20of the type Hamamatsu S5990 is installed here, for example.

FIG. 2shows a schematic lateral view of the sensor element15for the device10according to the present invention according toFIG. 1. The sensor element15has a basic component21, a carrier component22and an elastically deformable cantilever23.

The sensor element15is configured as a cantilever chip in this exemplary embodiment. The sensor element15is made of silicon, for example, by means of a photolithography method here. The basic component21is used for fastening the sensor element15at the free end of the carrier structure14according toFIG. 1. The basic component21and the carrier component22are separated from one another by means of a separating layer41. In this exemplary embodiment, the separating layer14is made of silicon oxide and has a thickness of 1 μm.

The carrier component22extends beyond the basic component21on one side of the basic component21. The cantilever23is fastened to the carrier component22at one end of the carrier component22facing away from the basic component21. The cantilever23in this exemplary embodiment has an essentially rod-like configuration and extends, starting from the carrier component22, away from same and the basic component21. The cantilever23is configured as a so-called cantilever. In this exemplary embodiment, the cantilever23has a length of 160 μm. The width of the cantilever23here is, for example, 40 μm and the thickness is 1.6 μm.

The cantilever23has an incoming flow structure24at one free end. A fluid, not shown in more detail here, flows against the cantilever23and the incoming flow structure24according to arrow25. In this case, the arrow25represents a main incoming flow direction of the fluid. In this exemplary embodiment, the main incoming flow direction according to arrow25is aligned at right angles to the longitudinal alignment of the cantilever23. A beam26of the laser17according toFIG. 1is directed at a side of the cantilever23facing away from the incoming flow structure24. Furthermore, the main incoming flow direction according to arrow25is arranged in the same plane as the beam26according to this example. In this exemplary embodiment, the beam26and the main incoming flow direction according to arrow25are located on the same axis and are directed towards one another.

The cantilever23has a reflecting surface27for reflecting the beam26on a side facing away from the incoming flow structure24. The reflecting surface27is made of a layer of aluminum in this exemplary embodiment.

FIG. 3shows a schematic perspective lateral view of a first embodiment of a cantilever28for a device10according to the present invention. For example, the cantilever28can be used instead of the cantilever23according toFIG. 2. The elastically deformable cantilever28has an essentially plate-like configuration, the dimensions of which in this exemplary embodiment correspond to those of the cantilever23according toFIG. 2. The cantilever28has a first incoming flow surface29, which is facing a flow of a fluid according to arrow25when the cantilever28is being used.

Furthermore, the cantilever28has an incoming flow structure30, which is fastened to same in the area of the free end of the cantilever28. The incoming flow structure30extends starting away from the first incoming flow surface29. The first incoming flow surface29and the incoming flow structure30are arranged on a side of the cantilever28facing away from the reflecting surface27. In this exemplary embodiment, the incoming flow structure30is configured as a plate-like component with a height of 30 μm, a length of 40 μm and a thickness of 9 μm. Here, the incoming flow structure30is made of the photoresist SU-8, for example. The incoming flow structure30extends at a right angle to the first incoming flow surface29. The incoming flow structure30is arranged on the first incoming flow surface29approximately centrally to the width of same.

The first incoming flow structure30provides a plurality of additional incoming flow surfaces31,32. Here, the two additional incoming flow surfaces31,32are arranged on two sides of the incoming flow structure30facing away from one another. The planes of the two additional incoming flow surfaces31,32are aligned parallel to one another. Furthermore, the planes of the two additional incoming flow surfaces31,32are aligned at right angles to the plane of the first incoming flow surface29.

Furthermore, the cantilever28or the first incoming flow surface29is aligned such that the additional incoming flow surface31is used here as a second incoming flow surface for the fluid. In this case, the second incoming flow surface31is aligned obliquely, and in this exemplary embodiment at an angle of about 45°, to the main incoming flow direction of the fluid according to arrow25. In this exemplary embodiment, the flow of the fluid according to arrow25corresponds to the main incoming flow direction, wherein the main incoming flow direction according to arrow25in this exemplary embodiment lies in a plane that is aligned at right angles to the planes of the first incoming flow surface29and of the additional incoming flow surfaces31,32.

As an alternative to the view inFIG. 3, the cantilever28may be arranged rotated clockwise by 90° about its longitudinal axis. In this case, the additional incoming flow surface32is used as the second incoming flow surface for the fluid.

In this exemplary embodiment, the plane of the first incoming flow surface29is aligned obliquely to the main incoming flow direction according to arrow25of the fluid, which is not shown in more detail here. For this, the device10according toFIG. 1or the beam26of the laser17is aligned obliquely to the main incoming flow direction according to arrow25. In this exemplary embodiment, the plane of the first incoming flow surface29or the beam axis of the laser17according to arrow25is aligned at an angle of about 45° to the main incoming flow direction of the fluid. Furthermore, the planes of the additional incoming flow surfaces31,32extend parallel to the longitudinal axis of the cantilever28.

FIG. 4shows a schematic perspective lateral view of a second embodiment of a cantilever33for a device10according to the present invention. In terms of its configuration and its dimensions, the cantilever33corresponds largely to the cantilever28or to the cantilever23. Thus, the cantilever33likewise has a first incoming flow surface29and the reflecting surface27on a side facing away from the first incoming flow surface29.

Unlike the cantilever28according toFIG. 3, the cantilever33has an incoming flow structure34in the area of its free end. The incoming flow structure34has an essentially V-shaped configuration. The incoming flow structure34is fastened approximately centrally to the first incoming flow surface29and extends away from the first incoming flow surface29. The incoming flow structure34has a first leg35and a second leg36. Starting from the first incoming flow surface29, the two legs35,36extend away from one another. The first leg35has two additional incoming flow surfaces37,38on two sides of the first leg35facing away from one another. The second leg36has two additional incoming flow surfaces39,40, which are arranged on two sides of the second leg36facing away from one another. The two additional incoming flow surfaces37and38as well as the two additional incoming flow surfaces39and40are each aligned parallel to one another. Furthermore, the additional incoming flow surfaces38and39are facing one another. The additional incoming flow surfaces37and40are facing away from one another. In this exemplary embodiment, the legs35,36are aligned at an angle of about 45° to one another. As an alternative, a different angle, in the range of 30° to 90° or 120°, is conceivable. Starting from the first incoming flow surface29and extending away from same, the legs35,36open in a funnel-like manner. Furthermore, the legs35,36are aligned at an angle of about 45° to the plane of the first incoming flow surface29in this example.

The plane of the first incoming flow surface29is aligned at right angles to the main incoming flow direction of the fluid according to arrow25. Furthermore, the beam26of the laser17is likewise aligned at right angles to the plane of the first incoming flow surface29of the cantilever33. By contrast, the additional incoming flow surfaces37,38,39,40of the incoming flow structure34are aligned obliquely to the plane of the first incoming flow surface29and thus obliquely to the main incoming flow direction of the flow according to arrow25as well as obliquely to the beam26of the laser17. In this exemplary embodiment, the planes of the additional incoming flow surfaces37,38,39,40are aligned at an angle of about 45° to the main incoming flow direction of the fluid according to arrow25or to the beam26of the laser17. Furthermore, the planes of the additional incoming flow surfaces37,38,39,40extend parallel to the longitudinal axis of the cantilever33. In this exemplary embodiment, the main incoming flow direction according to arrow25lies in a plane, which is aligned at right angles to the planes of the first incoming flow surface29and of the additional incoming flow surfaces37,38,39,40.

FIG. 5shows a schematic perspective lateral view of a third embodiment of a cantilever42for a device10according to the present invention. In terms of its configuration and its dimensions, the cantilever42corresponds largely to the cantilevers23,28,33. Thus, the cantilever42likewise has a first incoming flow surface29and the reflecting surface27on a side facing away from the incoming flow surface29.

Unlike the cantilevers23,28,33, the cantilever42has an incoming flow structure42in the area of its free end. In terms of its outer contour, the incoming flow structure43has an essentially V-shaped or funnel-like configuration. However, the incoming flow structure43has no legs, but rather is made of a solid material in this exemplary embodiment. The incoming flow structure43is fastened approximately centrally to the first incoming flow surface29and extends away from the first incoming flow surface29.

The incoming flow structure43has two additional incoming flow surfaces44,45on two sides of the incoming flow structure43facing away from one another. The additional incoming flow surfaces44and45are facing away from one another. In this exemplary embodiment, the two incoming flow surfaces44,45are aligned at an angle of about 105° to the plane of the first incoming flow surface29. Starting from the first incoming flow surface29and extending away from same, the additional incoming flow surfaces44,45run towards one another in a funnel-like or ramp-like manner. In this exemplary embodiment, the additional incoming flow surfaces44,45do not run together into a common edge, but rather the additional incoming flow surfaces44,45run towards one another starting from the first incoming flow surface29and end in a third additional incoming flow surface46. The third additional incoming flow surface46is facing away from the first incoming flow surface29. The plane of the third additional incoming flow surface46is aligned parallel to the plane of the first incoming flow surface29. As an alternative, the additional incoming flow surfaces44,45may run together into a common edge instead of the third additional incoming flow surface46.

The plane of the first incoming flow surface29is aligned at right angles to the main incoming flow direction of the fluid according to arrow25. Furthermore, the beam26of the laser17is likewise aligned at right angles to the plane of the first incoming flow surface29of the cantilever42. By contrast, the additional incoming flow surfaces44,45of the incoming flow structure43are aligned obliquely to the plane of the first incoming flow surface29and thus obliquely to the main incoming flow direction of the flow according to arrow25as well as obliquely to the beam26of the laser17. In this exemplary embodiment, the planes of the additional incoming flow surfaces44,45are aligned at an angle of about 15° to the main incoming flow direction of the fluid according to arrow25or to the beam26of the laser17. Furthermore, the planes of the additional incoming flow surfaces44,45extend parallel to the longitudinal axis of the cantilever42. In this exemplary embodiment, the main incoming flow direction according to arrow25lies in a plane, which is aligned at right angles to the planes of the first incoming flow surface29and of the additional incoming flow surfaces44,45.

FIG. 6shows a schematic perspective lateral view of another embodiment of a cantilever47for a device10according to the present invention. In terms of its configuration and its dimensions, the cantilever47corresponds largely to the cantilevers23,28,33,42. Thus, the cantilever47likewise has a first incoming flow surface29and the reflecting surface27on a side facing away from the incoming flow surface29.

Unlike the cantilevers23,28,33,42, the cantilever47has an incoming flow structure48in the area of its free end. In terms of its outer contour, the incoming flow structure48has an essentially V-shaped or funnel-like configuration. However, the incoming flow structure48has no legs, but rather is made of a solid material in this exemplary embodiment. The incoming flow structure48is fastened approximately centrally to the first incoming flow surface29and extends away from the first incoming flow surface29.

The incoming flow structure48has two additional incoming flow surfaces49,50on two sides of the incoming flow structure48facing away from one another. The additional incoming flow surfaces49and50are facing away from one another. In this exemplary embodiment, the two incoming flow surfaces49,50are aligned in a curved manner. Starting from the first incoming flow surface29and extending away from same, the additional, curved incoming flow surfaces49,50run towards one another in a funnel-like or ramp-like manner. In this exemplary embodiment, the additional incoming flow surfaces49,50run together into a common incoming flow edge51. The incoming flow edge51extends in the longitudinal direction of the cantilever48. Furthermore, the curved, additional incoming flow surfaces49,50extend starting from the incoming flow edge51up to outer end edges of the first incoming flow surface29. Thus, the first incoming flow surface29is covered entirely by the incoming flow structure48in the area of same. As an alternative, the incoming flow structure48may also have a smaller or larger width than the first incoming flow surface29.

The plane of the first incoming flow surface29is aligned at right angles to the main incoming flow direction of the fluid according to arrow25. Furthermore, the beam26of the laser17is likewise aligned at right angles to the plane of the first incoming flow surface29of the cantilever47. By contrast, tangents of the curved, additional incoming flow surfaces49,50of the incoming flow structure48are aligned, in at least some areas, obliquely to the plane of the first incoming flow surface29and thus obliquely to the main incoming flow direction of the fluid according to arrow25as well as obliquely to the beam26of the laser17. The curved, additional incoming flow surfaces49,50extend parallel to the longitudinal axis of the cantilever47. In this exemplary embodiment, the main incoming flow direction according to arrow25lies in a plane, which is aligned at right angles to the planes of the first incoming flow surface29and to the curved surfaces of the additional incoming flow surfaces49,50.

FIG. 7shows a schematic top view of a beam path52of a device10according to the present invention. The beam of the laser17extends in the longitudinal direction of the device10according toFIG. 1. In this case, at least a part of the beam26passes through the beam splitter19. In this exemplary embodiment, the beam splitter19is configured as a beam splitter membrane, namely as a so-called pellicle beam splitter. By contrast to a beam splitter cube, which is also conceivable, a smaller installation space is needed due to the use of a beam splitter membrane.

The beam26impacts the reflecting surface27of a cantilever23,28,33,42,47, not shown in more detail here. A point of reflection53, which is reflected according to the reflection beam53in the direction of the beam splitter19, forms on the reflecting surface27. In case of an unloaded cantilever23,28,33,42,47, the plane of the reflecting surface27is aligned at a right angle to the beam26. In case of a force acting on the cantilever23,28,33,42,47because of a fluid flow, the cantilever23,28,33,42,47is deflected and the reflecting surface27is aligned obliquely to the longitudinal axis of the beam26, as shown, for example, inFIG. 7.

The reflection beam54is directed starting from the reflecting surface27in the direction of the beam splitter19. A plane of the beam splitter19is aligned obliquely to the longitudinal axis of the beam26. In this exemplary embodiment, the plane of the beam splitter is aligned at an angle of 45° to the beam26.

The reflection beam54impacting the beam splitter19is diffracted in at least some areas in the direction towards the detector20by means of the beam splitter19. Here, the reflection beam54is deflected by means of the beam splitter19by 90° to the longitudinal axis of the reflection beam54between the reflecting surface27and the beam splitter19. The deflected reflection beam54then impacts the detector20.

In this exemplary embodiment, a plane of the two-dimensional detector20is aligned at right angles to the longitudinal axis of the reflection beam between the beam splitter19and the detector20or parallel to the longitudinal axis of the beam26.

Because of the configuration of the beam splitter19as a beam splitter membrane, here as a pellicle beam splitter, the so-called ghosting can be reduced considerably or can be entirely avoided. For example, when using a beam splitter cube, undesired multiple reflections occur in case of ghosting, which makes it difficult to make a clear determination of the point of impact of the reflection beam54on the detector20.

The mode of operation of the device according to the present invention is explained in more detail below on the basis ofFIGS. 1 through 7: The device10can be used for determining a parameter of a flow of a fluid, for example, a velocity and/or a flow direction of a gas or of a liquid. For example, the device10or the cantilever23,28,33,42,47is used as an anemometer. For this, the cantilever23,28,33,42,47is exposed to the flow of the fluid. The flow of the fluid impacts the incoming flow surfaces29,31,32,37,38,39,40,44,45,46,49,50, as a result of which a force due to the moving fluid acts on the cantilever23,28,33,42,47, which leads to a deformation of the cantilever23,28,33,42,47. The deformation is especially a bending and/or torsion of the cantilever23,28,33,42,47. The desired information about velocity and incoming flow angle is contained in such a deformation of the cantilever23,28,33,42,47. This information can be determined by means of known methods.

According to the present exemplary embodiment, a beam26of a laser17is focused in the area of a free end of the cantilever23,28,33,42,47, which has the reflecting surface27. The point of reflection53of the laser17reflected on the reflecting surface27moves as a function of the deformation of the cantilever23,28,33,42,47. This point of reflection53, which is moved and is reflected according to the reflection beam54, can be detected by means of the detector20. In this case, the detector20provides a two-dimensional measuring surface in order to be able to detect various positions of the reflected point of reflection53. The position of the point of reflection53or of the reflection beam54determined on the detector20with regard to its position contains the necessary information that will be subsequently evaluated to determine the velocity and/or the flow direction of the fluid.

In this case, at least one section of the incoming flow surface29,31,32,37,38,39,40,44,45,46,49,50is aligned obliquely or curved to a main incoming flow direction of the fluid according to arrow25. As a result, a higher angular resolution can be obtained in case of determining the flow direction of the fluid. In this case, the main incoming flow direction of the fluid is predetermined as a mean and/or average flow direction of the fluid, preferably at an incoming flow angle of 0° in relation to the beam26and in an unloaded state of the cantilever23,28,33,42,47. In particular, the flow directions and/or incoming flow angle of the fluid to be determined in relation to the incoming flow surface29,31,32,37,38,39,40,44,45,46,49,50are arranged distributed about the main incoming flow direction of the fluid.

Thus, highly resolved measurements of the velocity and/or of a flow direction of a fluid in two dimensions, for example, on size scales below one mm, especially in the range of about 140 μm to 160 μm, and in an angle range of up to 180°, are possible with the device according to the present invention.