Low-altitude atmospheric turbulence generator device and associated wind tunnel

Abstract

Turbulence-generating device for a wind tunnel, the device comprising at least a first bar (11) and a second bar (12), both intended to be arranged in a convergent section of a wind tunnel, the two bars forming two independent elements intended to be arranged spaced apart from each other in the convergent section, the two bars extending in operation through the convergent section at an angle to each other. Associated wind tunnel. FIGURE IN ABRIDGED DIAGRAM: Fig. 1

Description

Title of the invention: Low-altitude atmospheric turbulence generating device and associated wind tunnel

[0001] The invention relates to a device for generating low altitude atmospheric turbulence in a wind tunnel.

[0002] The invention also relates to a blower equipped with such a device.

[0003] BACKGROUND OF THE INVENTION

[0004] To accurately study the effects of wind on a structure, in particular atmospheric wind at low altitude, it is necessary to be able to reproduce such effects in wind tunnels.

[0005] Currently, the techniques developed from Counihan's work and methods are only applicable to very specific wind tunnels, such as long-flow wind tunnels. However, such installations are few in number because they are expensive to build and operate.

[0006] Generally, it is preferable to use more standard wind tunnels, called short-vein wind tunnels, in which one or more grids are arranged in order to generate turbulence in the airflow.

[0007] However, such grids do not allow the airflow to be modified sufficiently to faithfully reproduce the effects of wind at low altitude.

[0008] SUBJECT OF THE INVENTION

[0009] The invention aims in particular to provide a solution enabling the effects of wind at low altitude in a wind tunnel to be simulated more faithfully. Summary of the invention

[0010] For this purpose, according to the invention, a turbulence generating device for a wind tunnel is provided, the device comprising at least two bars intended to be arranged in a convergent section of a wind tunnel, the two bars forming two independent elements intended to be arranged spaced apart from each other in the convergent section, the two bars extending in service through the convergent section at an angle to each other.

[0011] The use of these two bars makes it possible to introduce turbulence (i.e. disturbances) into an airflow circulating in the convergent: the airflow thus disturbed faithfully reproduces the behavior of the atmospheric wind at low altitude.

[0012] By “low altitude atmospheric wind”, we mean a wind present at an altitude less than 200 meters above the area considered (therefore not necessarily above sea level).

[0013] The inventor was able to observe in particular that the arrangement of the bars transverse to the direction of the flow made it possible to create a detachment of alternating vortices formed behind the bars, vortices which are then diffused and accelerated by the downstream section of the convergent before reaching a test vein.

[0014] Advantageously, the invention is a passive device. It makes it possible to generate turbulence without needing to move relative to the wind tunnel and in particular to the convergent.

[0015] Moreover, the invention proves to be simple in structure.

[0016] The invention also works without energy.

[0017] The invention also proves to be inexpensive to manufacture.

[0018] The invention also allows for easy implementation in existing wind tunnels.

[0019] Subsequently, the terms "upstream" and "downstream" should be understood according to the direction of the airflow in the wind tunnel, from the inlet chamber of the latter, to at least its divergent point.

[0020] Hereafter, the terms "upper", "high", "lower", ... shall be understood according to the operating position of the wind tunnel and the turbulence generating device, when the wind tunnel rests on a base or on the ground and the device is arranged in the wind tunnel and ready for testing.

[0021] Optionally, at least one of the bars has a polygonal cross-section.

[0022] Optionally, the first bar and the second bar have, for at least one section of the first bar and at least one section of the second bar, the same cross-section.

[0023] The invention also relates to a wind tunnel comprising at least successively an air inlet chamber, a convergent, a test section and a divergent, the wind tunnel comprising at least one device according to one of the preceding claims arranged in the convergent.

[0024] Optionally the first bar is arranged in the second half of the convergent.

[0025] Optionally, the second bar is arranged in the third third of the convergent.

[0026] Optionally, the first bar is arranged upstream of the second bar, the first bar being arranged so that one of its edges forms its end closest to the entrance of the convergent.

[0027] Optionally, the second bar is arranged so that one of the flat faces forms its end closest to the entrance of the convergent.

[0028] Optionally, the device includes an additional bar arranged between the first bar and the second bar.

[0029] Optionally, the additional bar extends vertically in the convergent.

[0030] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings

[0031] Reference will be made to the attached drawings, among which:

[0032] [Fig-1] [Fig.1] is a schematic cross-sectional view of part of a wind tunnel according to a first embodiment of the invention;

[0033] [Fig.2] [Fig.2] is a cross-sectional view of a wind tunnel convergent represented in [Fig.1];

[0034] [Fig. 3] [Fig. 3] is a schematic cross-sectional view of part of a wind tunnel according to a second embodiment of the invention;

[0035] [Fig.4] [Fig.4] is a cross-sectional view of a wind tunnel convergent represented in [Fig.3]. DETAILED DESCRIPTION OF THE INVENTION

[0036] With reference to figures 1 to 2, a wind tunnel 1 according to a first embodiment will now be described.

[0037] The wind tunnel 1 comprises at least one section extending longitudinally along a first longitudinal axis X. Said axis X is horizontal when the wind tunnel 1 rests on the horizontal ground or a horizontal base.

[0038] A cross-section of said segment can thus be defined by a second axis Y which is orthogonal to the first axis X, and a third axis Z which is orthogonal to the first axis X and to the second axis Y. When the first axis X is horizontal, the second axis Y is vertical and the third axis Z is horizontal.

[0039] In this section are arranged successively (along the first axis X): an inlet chamber 2 (sometimes also called a settling chamber), a convergent 3 following the inlet chamber 2, a test vein 4 following the convergent 3, a divergent 5 following the vein 4 and an outlet chamber following the divergent 5.

[0040] The wind tunnel 1 can be an open-circuit wind tunnel (the inlet chamber 2 and the outlet chamber are thus open to the outside) or a closed-circuit wind tunnel (the wind tunnel 1 then includes an additional section connecting the outlet chamber to the inlet chamber 2). Preferably, the wind tunnel is a closed-circuit wind tunnel. The air stream 4 is therefore not open to the outside.

[0041] Preferably, the wind tunnel 1 is a short-vein wind tunnel 4 (as opposed to a long-vein wind tunnel). A "long" vein is a vein whose length (along the first X-axis) is at least twenty times greater than the height (considered along the second Y-axis) of the vein. A "short" vein is a vein whose length is X times the height of the cross-section of the vein, X being less than 10 and preferably less than 5 and preferably less than 4 and preferably between 3 and 4 times.

[0042] In this application, the term "diameter" should be understood in its geometric sense, namely, as the upper bound of the set of distances between any two points in a subset A of a metric space. The cross-section of vein 4, whose cross-section plane has its normal to the first axis X, is therefore not necessarily circular in its external contour.

[0043] Optionally, the vein 4 here has a cross-section with rectangular or square internal and external contours. The diameter of said cross-section is therefore the diagonal connecting opposite corners of the external contour of the vein 4.

[0044] Preferably, the duct 4 has the same cross-section along its entire length.

[0045] With such a wind tunnel 1, the airflow 6 originates from the inlet chamber 2 and arrives at the inlet of the convergent nozzle 3. The airflow 6 is usually hypoturbulent (with an intensity of less than 1-2%). Said airflow 6 thus propagates in the inlet chamber 2 and at the inlet of the convergent nozzle 3 along a general propagation direction G. The general direction G is parallel here (and preferably coincident) with the first axis X. According to the invention, a turbulence-generating device 10 is arranged in the wind tunnel 1.

[0046] The device 10 comprises at least two bars 11, 12. In the first embodiment, the device 10 strictly comprises two bars 11, 12. Preferably, the device 10 consists solely of these two bars 11, 12 (with optional attachment means for the bars 11, 12 up to convergent 3).

[0047] We will now describe the first bar 11.

[0048] The first bar 11 is full.

[0049] The first bar 11 extends longitudinally along a longitudinal direction Bi

[0050] The first bar 11 here presents a cross-section (according to a plane of section having normal to the longitudinal direction Bi) polygonal. Preferably, said cross-section is in the shape of a quadrilateral. Preferably said cross-section is in the shape of a square.

[0051] The first bar 11 is identical along its entire length (considered along the longitudinal direction Bi). The first bar 11 thus has the same cross-section along its entire length.

[0052] At least the height and / or width (i.e., one side) of the cross-section of the first bar 11 is equal to between 5 and 20% of the height (considered along the second Y axis) of the vein 4 and is for example between 8 and 18% and is for example 10%.

[0053] The first bar 11 is, for example, made of or based on wood, plastic, etc.

[0054] We will now describe the positioning of the first bar 11 in the wind tunnel 1.

[0055] The first bar 11 is arranged in the convergent 3.

[0056] Preferably, the first bar 11 is arranged in the second half of the convergent 3, i.e. in the most downstream half of the convergent 3.

[0057] Preferably, for a convergent length L (length considered along the first axis X), the center of a first end 3a of the first bar 11 (i.e. the lowest end of the first bar 11 when the first bar 3 is in place in the convergent) is arranged at a distance di from the exit of the convergent 3 (corresponding to the inlet of the vein 4) less than 0.5L and preferably less than 0.4L.

[0058] Preferably, the distance di is also greater than 0.2L.

[0059] Optionally, the first bar 11 is fixed to the converging element 3. This fixing may be permanent or temporary. This fixing may be achieved by any known means of attachment (removable or not): adhesive, screw and nut, welding, etc. At least one, and optionally both ends of the first bar 11 are fixed to the converging element 3.

[0060] The first bar 11 is arranged so as to extend through the convergent 3.

[0061] The first bar 11 is here of such a length that its two ends touch Each bar 11 touches at least one wall of the convergent section 3. The first bar 11 is of such a length that the first end 1a of the first bar 11 touches at least one wall of the convergent section 3, and that a second end 11b of the first bar 11 touches at least one wall of the convergent section 3 opposite the first wall. Hereafter, "touching" means that the contact between the first bar 11b and the wall of the convergent section 3 in question is direct (optionally apart from the means of attachment).

[0062] In the present case, the convergent 3 has four walls which are opposite each other in pairs. The first end 1a of the first bar 11 touches the first wall 21 and the second wall 22 and the second end 11b of the first bar touches the third wall 23 (opposite the first wall 21) and the fourth wall 24 (opposite the second wall 22).

[0063] More specifically here, the first bar 11 extends so that its first end 11 is arranged at the junction between the first wall 21 and the second wall 22 and so that its second end is arranged at the junction between the third wall 23 and the fourth wall 24.

[0064] The first bar 11 thus extends through the entire convergent 3. In particular, the first bar 11 crosses the entire section of the convergent 3.

[0065] It is therefore understood that the first bar 11 is arranged so that the longitudinal direction Bisoit is inclined (i.e. is neither parallel nor orthogonal) with respect to the second axis Y and the third axis Z.

[0066] Preferably, the first bar 11 is also arranged so that the longitudinal direction B is inclined with respect to the first axis X (i.e. is neither parallel nor orthogonal to the first axis X).

[0067] The first bar 11 thus does not extend straight, vertically, or horizontally in the convergent 3. For example, the second end 11b of the first bar 11 (i.e., the highest end) is closer to the exit of the convergent 3 than the first end 1la of the first bar 1 (i.e., the lowest end).

[0068] Preferably, the first bar 11 is oriented so that the airflow 6 arrives on an edge of the first bar 11. The first bar 11 is therefore oriented so that a longitudinal edge of the first bar 11 (which here has four) is the part of the first bar 11 arranged closest to the inlet of the convergent 3. The first bar 11 thus forms a point (extending through the entire convergent 3) for the arrival of the airflow 6 in the convergent 3.

[0069] We will now describe the second bar 12.

[0070] The second bar 12 is full.

[0071] The second bar 12 extends longitudinally along a longitudinal direction B2.

[0072] The second bar 12 has a polygonal cross-section (along a section plane whose normal is along the longitudinal direction B2). Preferably, said cross-section is in the shape of a quadrilateral. Preferably, said cross-section is in the shape of a square.

[0073] The second bar 12 is identical along its entire length (considered along the longitudinal direction B2). The second bar 12 thus has the same cross-section along its entire length. The second bar 12 has the same cross-section (shape and dimensions) as the first bar 11. However, the second bar 12 is shorter than the first bar 11.

[0074] At least the height and / or width (i.e., one side) of the cross-section of the second bar 12 is equal to between 5 and 20% of the height (considered according to the second axis Y) of vein 4 and is for example between 8 and 18% and is for example 10%.

[0075] The second bar 12 is, for example, made of or based on wood, plastic, etc. The second bar 12 is, for example, made of the same material as the first bar 11.

[0076] We will now describe the positioning of the second bar 12 in the wind tunnel 1.

[0077] The second bar 12 is arranged downstream of the first bar 11.

[0078] The second bar 12 is arranged in the convergent 3. Preferably, the second bar 12 is arranged in the third third of convergent 3 (i.e. the lower third of convergent 3).

[0079] Preferably, the center of a first end 12a of the second bar 12 (i.e. the lowest end of the second bar 12 when the second bar 12 is in place in the convergent 3) is arranged at a distance d2 from the outlet of the convergent 3 (corresponding to the inlet of the vein 4) less than 0.3L.

[0080] Preferably, the distance d2 is also greater than 0. IL and for example greater than 0.16L.

[0081] Optionally, the second bar 12 is fixed to the converging element 3. This fixing may be permanent or temporary. This fixing may be achieved by any known means of attachment (removable or not): adhesive, screw and nut, welding, etc. At least one, and optionally both ends of the second bar 12 are fixed to the converging element 3.

[0082] The means for attaching the second bar 12 are optionally independent of those of the first bar 11.

[0083] The second bar 12 is arranged so as to extend through the convergent 3.

[0084] The second bar 12 is here of such a length that its two ends touch Each bar 12 touches at least one wall of the converging section 3. The second bar 12 is of such a length that the first end 12a of the second bar 12 touches at least one wall of the converging section 3, and the second end 12b of the second bar 12a touches at least one wall of the converging section 3 opposite the first wall. Hereafter, "touching" means that the contact between the second bar 12 and the wall of the converging section 3 is direct (optionally, apart from the means of attachment).

[0085] In the present case, the second end 12b of the second bar 12 touches here the third wall 23 and the second wall 22 and the first end 12a of the second bar 12 touches here the first wall 21 and the fourth wall 24.

[0086] More specifically here, the second bar 12 extends so that its first end 12a is arranged at the junction between the first wall 21 and the fourth wall 24 and so that its second end 12b is arranged at the junction between the third wall 23 and the second wall 22.

[0087] The second bar 12 thus extends through the entire convergent 3. In particular, the second bar 12 crosses the entire section of the convergent 3.

[0088] It is therefore understood that the second bar 12 is arranged so that the longitudinal direction B2 is inclined with respect to the second axis Y and the third axis Z.

[0089] The second bar 12 is also arranged so that the longitudinal direction B2 is inclined with respect to the first axis X.

[0090] The second bar 12 thus does not extend straight, vertically, or horizontally in the convergent 3. For example, the first end 12a of the second bar 12 (i.e., the lower end) is closer to the outlet of the convergent 3 than the second end 12b of the second bar 12 (i.e., the higher end).

[0091] Preferably, the second bar 12 is oriented so that the airflow 6 arrives on a longitudinal face of the second bar 12 (in this case, four in number). The second bar 12 is therefore oriented so that a lateral face of the second bar 12 is the part of the second bar 12 arranged closest to the inlet of the convergent 3. The second bar 12 thus forms a plane (extending through the entire convergent 3) for the airflow 6 coming from the first bar.

[0092] Thus arranged, the two bars 11,12 form two independent elements.

[0093] Thus arranged, the two bars 11,12 are spaced apart from each other in the converge 3 in particular along the first axis X. The two bars 11, 12 therefore do not touch.

[0094] It is also understood that the two bars 11, 12 extend at an angle to each other. In particular, the longitudinal directions Bi and B2 are inclined relative to each other.

[0095] More specifically here, the two bars 11,12 jointly form a cross in the convergent 3.

[0096] More precisely here, in a Euclidean frame linked to the first bar 11, with the longitudinal direction Biforming one of the axes of this frame, the longitudinal direction B2 is inclined with respect to the three axes of this frame.

[0097] With reference to Figures 3 and 4, a second embodiment will now be described. This second embodiment is identical to the first embodiment except that the device 10 includes an additional bar 13.

[0098] The device 10 thus comprises at least three bars. In the second embodiment, the device comprises strictly three bars. Preferably, the Device 10 consists solely of these three bars 11, 12, 13 (with optional means of attaching the bars to the convergent 3).

[0099] We will now describe the third bar 13.

[0100] The third bar 13 is full.

[0101] The third bar 13 extends longitudinally along a longitudinal direction B3.

[0102] The third bar 13 has a polygonal cross-section (along a section plane whose normal is along the longitudinal direction B3). Preferably, said cross-section is in the shape of a quadrilateral. Preferably, said cross-section is square.

[0103] The third bar 13 is identical along its entire length (considered along the longitudinal direction B3). The third bar 13 thus has the same cross-section along its entire length. The third bar 13 therefore has the same cross-section (shape and dimensions) as the first bar 11 and / or the second bar 12. However, the third bar 13 is shorter than the first bar 11 and / or the second bar 12. For example, the third bar 13 has a length between 10 and 30% of the vein height (considered along the second Y-axis) and, for example, between 15 and 20% of the vein height.

[0104] Whether in the first or second embodiment, the first bar 11 and / or the second bar preferably have a length such that the first bar 11 and / or the second bar 12 are supported against opposite areas of the convergent.

[0105] At least the height and / or width (i.e., one side) of the cross-section of the second bar 12 is equal to between 5 and 20% of the height (considered along the second Y axis) of the vein 4 and is for example between 8 and 18% and is for example 10%.

[0106] The third bar 13 is for example made of or based on wood, plastic, etc. The third bar 13 is for example made of the same material as the first bar 11 and / or the second bar 12.

[0107] We will now describe the positioning of the third bar 13 in the wind tunnel 1.

[0108] The third bar 13 is arranged here downstream of the first bar 11. The third bar 13 is arranged here upstream of the second bar 12. The third bar 13 is thus arranged between the first bar 11 and the second bar 12. For example, the third bar is arranged equidistant from the first bar 11 and the second bar 12.

[0109] The third bar 13 is arranged in the convergent 3.

[0110] Optionally, the third bar 13 is fixed to the converging element 3. This fixing may be permanent or temporary. This fixing may be achieved by any known means of attachment (removable or not): adhesive, screw and nut, welding, etc. This fixing is, for example, independent of that of the first bar 11 and / or the second bar 12.

[0111] A single end of the third bar 13 is here fixed to the convergent 3.

[0112] The third bar 13 is arranged so as to extend through the convergent 3.

[0113] The third bar 13 is here of such a length that only one of its ends touches at least one wall of the convergent 3. The other end of the third bar 13 thus extends freely inside the convergent 3. Hereafter by "touch" we mean that the contact between the third bar 13 / and the wall considered of the convergent 3 is direct (optionally apart from the means of attachment).

[0114] The first end 13a of the third bar 13 (i.e. the lowest end) is the one here fixed to the first wall 21.

[0115] More specifically here, the third bar 13 extends so that its first end 13a is arranged opposite the first wall 21, that is, the wall of the convergent 3 closest to the ground or the base on which the wind tunnel 1 rests.

[0116] It is therefore understood that the third bar 13 does not extend through the entire convergent 3. In particular, the third bar 13 does not cross the entire section of the convergent 3.

[0117] The third bar 13 is arranged so that the longitudinal direction B3 is here parallel to the second axis Y and therefore orthogonal to the first axis X.

[0118] The third bar 13 thus extends straight and vertically in the convergent 3.

[0119] Preferably, the third bar 13 is here oriented so that the flow Air 6 arrives on an edge of the third bar 13. The third bar 13 is therefore oriented so that a longitudinal edge of the third bar 13 (which has four of them here) is the part of the third bar 13 arranged closest to the entrance of the convergent 3. The third bar 13 thus forms a point (extending only in the lower part of the convergent 3) for the arrival of the air flow from the first bar 11.

[0120] Thus arranged, the three bars 11, 12, 13 form three independent elements.

[0121] Thus arranged, the three bars 11, 12, 13 are spaced from each other by particular along the first X axis. The three bars 11, 12, 13 therefore do not touch.

[0122] It is also understood that the three bars 11, 12, 13 extend at an angle to each other. In particular, the longitudinal directions Bi and B2 and B3 are inclined with respect to each other.

[0123] Apart from what has been indicated above, everything that has been said for the first embodiment (in particular with regard to the first bar 11 and the second bar 12) is also applicable to the second embodiment.

[0124] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0125] Although each bar here has an identical cross-section along its entire length, at least one of the bars may have a variable cross-section along its length. For example, the cross-section of said bar may increase between one end of the bar and the other end of the bar. For example, said cross-section may increase progressively between the two ends of said bar.

[0126] Although here the cross-section of each of the bars is polygonal, at least one of the bars may have a rounded cross-section. For example, at least one of the bars may be shaped into a cone or a truncated cone.

[0127] The first end of the first bar may be further from the outlet of the convergent section than the second end of the first bar. In this case, it is preferable to have the second end of the second bar further from the outlet of the convergent section than the first end of the second bar. At least one of the first or second bars may be arranged so that its first end is as far from the outlet of the convergent section as its second end. This bar will thus extend orthogonally to the first X-axis (which defines) the length of the convergent section. In this case, it is preferable to have at least one of the bars having a cross-section that varies along its length. Although here the different bars are fixed to the convergent section, at least one of the first or second bars may simply be arranged within the convergent section until its two ends come into contact with one or more walls of the convergent section.The bar in question will then simply be wedged in the convergent section between one or more walls of the convergent section.

[0128] At least one end of the bar may be fixed temporarily or permanently to the convergent.

[0129] At least one end of the bar can be fixed by adhesive, by screwing, ... to the convergent.

[0130] At least one of the bars may be made of wood, plastic, metal, ... At least one of the bars may be made of a single material or of multiple materials.

[0131] Although here the vein has a square or rectangular cross-section, the vein may have a cross-section of a different shape and for example oval or circular. The cross-section of the vein can therefore be of a different shape from the cross-section of at least one of the bars.

Claims

Demands

1. Turbulence generating device for wind tunnel, the device comprising at least a first bar (11) and a second bar (12) both intended to be arranged in a convergent of a wind tunnel, the two bars forming two independent elements intended to be arranged spaced apart from each other in the convergent, the two bars extending in service through the convergent inclined to each other.

2. Device according to claim 1, wherein at least one of the bars has a polygonal cross-section.

3. Device according to any one of the preceding claims, wherein the first bar (11) and the second bar (12) have, for at least one section of the first bar and at least one section of the second bar, the same cross-section.

4. Wind tunnel comprising at least successively an air inlet chamber (2), a convergent (3), a test section (4) and a divergent (5), the wind tunnel comprising at least one device according to one of the preceding claims arranged in the convergent.

5. Blower according to claim 4, wherein the first bar (11) is arranged in the second half of the convergent (3).

6. A wind tunnel according to any one of claims 4 to 5, wherein the second bar (12) is arranged in the third third of the convergent (3).

7. A wind tunnel according to any one of claims 4 to 6, wherein the first bar (11) is arranged upstream of the second bar (12), the first bar (11) being arranged so that one of its edges forms its end closest to the inlet of the convergent (3).

8. Blower according to claim 7, wherein the second bar (12) is arranged so that one of the flat faces forms its end closest to the inlet of the convergent (3).

9. Blower according to any one of claims 4 to 8, wherein the device comprises an additional bar (13) arranged between the first bar (11) and the second bar (12).

10. Blower according to claim 9, wherein the additional bar (13) extends vertically in the convergent (3).

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