JPH0968208A - Pressure-resistance reducing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently reduce the pressure resistance of even an angular object by forming a small notch in the position of the flow-receiving object where fluid separates, or just in front of it. SOLUTION: An object 2 which receives flow has, e.g. a square cross-sectional shape, with a square notch 3 formed like a step at each of the front angles of this square shape. By setting the small notch 3 to an appropriate size, a separating line of flow F which has temporarily separated from the front edge 6 of the small notch 3 interferes with a rear edge 7 just near it, causing a part of the vortex of a shear layer to converge to the small notch 3 to gradually form a strong vortex G. Since the vortex has a lower pressure than an external stream H, the flow is curved in such a way that its radius of curvature is decreased by the balance between a pressure gradient in the radial direction of the flow and a centrifugal force, causing the separating line of flow F to come into contact with portions near the rear end 7 again. Therefore, the external stream H is also curved in such a way as to come close to the side 8 of the object 2 and to flow along the side 8. Therefore, the area of the backflow B of the object 2 is reduced appreciably, resulting in greatly decreased pressure resistance.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure resistance reducing structure.

[0002]

2. Description of the Related Art Generally, in high-speed vehicles such as airplanes, automobiles, and Shinkansen trains, it has been believed that the streamlined type with the least irregularities is most preferable in order to reduce the pressure resistance received from the air.

[0003]

The conventional streamlined manufacturing of an object is difficult to manufacture such as curved surface processing, and the manufacturing cost is high.

The present inventor defeated the existing idea that the shape of an object that receives the above-mentioned flow must be streamlined,
It is an object of the present invention to sufficiently reduce the pressure resistance of an angular body, or to further reduce the pressure resistance of a streamlined body.

[0005]

In the pressure resistance reducing structure according to the present invention, a small recess is formed at a position where a fluid is separated from a body receiving a flow or a position immediately before the position. Alternatively, a notched small recess is formed to generate a strong vortex that attracts the separated external flow.

Further, the object that receives the flow has an angular three-dimensional shape, and a small recess is formed at the front edge of the object. Alternatively, a notched small recess is formed on the ridge on the front surface side and the ridge on the rear surface side of the object.

Further, the object which receives the flow has a rectangular cross-sectional shape, and rectangular cutout small recesses are formed at both front corners thereof. Alternatively, the object that receives the flow has a square cross-sectional shape, and square cutout small recesses are formed at both front corners.

When the length of one side of the square of the cross-sectional shape of the object that receives the flow is D and the length of one side of the square of the cross-sectional shape of the cutout small recess is d, (D-2
The value of d) / D was set to 0.6-0.95.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a fluid flow (streamline) in the case where a prism having a square cross-sectional shape is provided as an object 41 for receiving a flow in a uniform flow, and the front (the upstream side of the flow) is shown. )
Both corners A and A are largely separated as the peeling positions 1 and 1. B is the wake of the object 41 that receives the flow, and the wake region B ₀ is large.

An embodiment of the present invention is illustrated in FIG. That is, the object 2 that receives a flow has a square cross-sectional shape, and at the peeling positions 1 and 1 shown in FIG.
The small recesses 3 and 3 are formed. That is, the square small recesses 3, 3 are formed in a stepped shape at both front corners A, A of the square. In other words, the object 2 that receives this flow is a quadrangular prism, and the cutout small recess 3 is formed in the ridge on the front surface 4 side.
To form

Further, as shown in FIG. 2B, the rear corners C, C may be provided with small recesses 3, 3 having a square cross section. That is, the cutout small recesses 3 are formed (at a total of 4 places) at the ridge on the front surface 4 side and the ridge on the rear surface 5 side of the object that receives the flow.

FIG. 3 and FIG. 4 show the case where an object having such a shape is arranged in a uniform flow. If the size of the notch small recess 3 is set appropriately, the front edge of the notch small recess 3 will be described. The flow once separated from the portion 6--represented by the streamline F--reattaches to the trailing edge portion 7. In other words, the flow separated from the front edge portion 6 is a shear layer, and this separation streamline F interferes with the trailing edge portion 7 in the immediate vicinity, so that a part of the vortex of the shear layer gathers in the notch small recess 3. , Gradually forming a strong vortex G. Since this vortex portion has a much lower pressure than the external flow H, it is bent so that the radius of curvature of the flow becomes smaller due to the balance between the pressure gradient in the radial direction of the flow and the centrifugal force. It reattaches near the edge 7. Therefore, the external flow H is also bent so as to approach the side surface 8 of the object 2 and flows along the side surface 8 following the separation streamline F of the notch small recess 3.

As shown in FIG. 5, the reattachment point of the streamline F is located inside the notched small recess 3 with respect to the rear end line 7, or as shown in FIG.
Although it may be slightly shifted to the side surface 8 side as shown in (1), in any case, the separation streamline F reattaches to the body that receives the flow.

As a result, the regions B ₄ , B ₅ , B ₆ of the wake B of the body 2 receiving the flow are significantly reduced (compressed) (compared to FIG. 1), and the pressure resistance (drag) is significantly reduced. Conceivable.

Further, as shown in FIGS. 2B and 7,
If four notch small recesses 3 are formed on the ridges on the front surface 4 and rear surface 5 sides of the object 2 that receives the flow, the external flow H is similarly attracted by the vortices G in the notch small recesses 3 and the wake The area B ₇ of B is further reduced and the drag force is reduced.

As mentioned above, the present invention provides a flow receiving object 2
It can be said to be a structure that controls the flow by creating flow separation around and reduces the pressure resistance.
That is, when flow delamination occurs around an object, the resistance of the object often increases. However, when the flow separation is appropriately generated as shown in FIGS. 3 to 7, the flow around the object 2 is controlled by the flow line F of the separation flow,
The width of the wake can be reduced to reduce pressure resistance.

Stepping on a prism --- Formation of a small recess 3 of a notch-
Fig. 8 shows the results of the wind tunnel experiment showing the reduction in resistance due to
Shown in FIG. 8C shows the cross-sectional shape and dimensions of an object that receives the flow of the product of the present invention, where one side of the square is D and one side of the notch small recess (square) is d. The value of (D-2d) / D is plotted on the horizontal axis of the graph of FIG.

Alternatively, FIG. 8B shows, for comparison, the value of (D-2r) / D in the case where a radius (roundness) r is formed at the corner of a square cross section having one side D. It is on the horizontal axis of the graph in 8 (a).

In FIG. 8 (a), the vertical axis represents the pressure resistance Cd _{0 in} the case of the original square cross-section in which the cutout small recesses are not rounded at the corners, and FIG. 8 (c) or (b) The value of the pressure resistance Cd in the case of) is called the "resistance coefficient". Then, the solid line is the measured value in the case of FIG. 8C, the broken line is the case of FIG. 8B, and the respective ray-lezzle numbers Re are 8 × 10 ⁴ and 10 ⁵ . However, FIG. 8 (a)
The broken line is `` Hoerner, SF, Fluid Dynamic Drag, p3-1
3, (1958), Published by the Author ”.

From the graph of FIG. 8 (a), (D-2
It can be seen that it is preferable to set the value of d) / D to 0.6 to 0.95. It is understood that a particularly desirable range is 0.8 to 0.9, the resistance coefficient Cd / Cd ₀ is about 0.5, and the pressure resistance is halved.

In the broken line in FIG. 8 (a) showing the case of FIG. 8 (b), it is necessary to take an extremely large radius r in order to achieve a resistance coefficient of about 0.5 (it must be a cylinder. ). That is, when the notch small recess is formed as in the present invention,
It shows that a small coefficient of resistance equal to that of the large round (r r) cross-sectional shape was easily obtained.

This decrease in resistance can be estimated to be due to a decrease in the wake width (more specifically, the momentum) of the prism 2—the body 2 that receives the flow. This can be explained by the change in the pressure on the rear surface (back surface) of the object 2).

That is, it is considered that the pressure in front of the flow colliding is a positive pressure (+) and does not fluctuate much. On the other hand, the pressure on the back surface (rear surface) is a negative pressure, and the value of the negative pressure occupies a large weight in the resistance change.

The horizontal axis of FIG. 9A shows the value of (D-2d) / D (see (B) of FIG. 9), and the vertical axis shows the average back pressure coefficient Cpb. This average back pressure coefficient Cpb is shown in the following mathematical formula 1.

[0026]

[Equation 1]

As is apparent from FIG. 9, (D-2
When the value of d) / D is set in the range of 0.8 to 0.9, the negative pressure is reduced to about half as compared with the case of a prism without a notch small recess (when the value of the horizontal axis is 1). There is. (This tendency corresponds to FIG. 8A).

Next, referring to FIG. 10, another embodiment is shown, in which the vertical and horizontal dimensions of the cutout small recesses--steps--are made different (when rectangular cutout small recesses are used). Resistance is about 4
It shows that it can be reduced to a relatively small amount. This Cd / Cd
A value of ₀ of about 0.4 is smaller than that of a cylinder (about 0.5). The formation of the cutout small concave portion having a rectangular cross-sectional shape as described above has an excellent effect of reducing a large pressure resistance.

FIG. 11A shows another embodiment in which the cross-sectional shape of the object 2 that receives a flow is trapezoidal and the front surface 4 thereof is
.. are formed in the corners on the side and the corners on the rear surface 5 side. Further, in FIG. 11B, when the cross-sectional shape is circular, the notch small recesses 3 are formed on the front surface 4 side at the fluid peeling position 1 to the position immediately before the position where there is no notch small recess 3 ... are doing. (And also on the rear surface 5 side, the small recesses 3,
3 is formed. ) The small recess 3 is in the shape of a right triangle.

Further, FIG. 11A shows a case of an elliptical cross section. Further, in this case, the small cutout recess 3 is V-shaped.

In addition to this FIG. 11, various cross-sectional shapes can be considered, but in short, it is assumed that there is no notch small recess 3 and the fluid separation position in the body 2 receiving the flow or immediately before that position. In addition, it is important to form the small recesses 3 and 3. It should be noted that the notch small recesses 3, 3 may be formed on the rear surface 5 side as necessary.

Next, FIG. 12 is a cross-sectional view of an essential part illustrating the shape of the small cutout recess 3, where (a) to (f) show the case where the object 2 receiving the flow has an angular solid shape. G) ~
In (e), the object 2 that receives the flow is streamlined (not square)
The case of a three-dimensional shape is shown.

Further, as shown in FIG. 13, the object 2 which receives the flow may be a hollow object--a hollow rod (tube / cylinder) or a shell-like object. As an application example, see Fig. 13 (a) for the frame and handle of bicycles and motorcycles.
A pipe having a cross section such as (b) and (c) may be used. Alternatively, it may be used for a supporting column of a hydrofoil or the like, a screw holding casing of a high-speed ship, a rudder, or the like.

FIG. 14 shows a trailer, a cargo truck, a freight car,
The case of a box-shaped moving object such as a train is shown as an example, and the front surface 4
A small cutout recess 3 is formed in the side edge. The cutout small recess 3 may be formed also on the rear surface 5 side (see the same drawing).

Further, as shown in FIG. 15, it is also preferable to additionally provide a resistance reducing device 9 having a small recess 3 in the cab of the cargo truck. Further, FIG. 16A shows a side view of a current collector 10 projecting from the ceiling of a train such as a bullet train. It is also promising to consider the casing (cover) 11 of the current collector 10 as an object that receives the flow of the present invention and form the small recesses 3 ...

Further, FIG. 17 is a sectional view of a side mirror 12 of an automobile, in which a small cutout recess 3 is formed in the peripheral edge of the front surface 4 side which receives the wind as shown by the arrow. In addition, the present invention can be applied to a portion that has jumped out of a vehicle such as an automobile, a ship, or an airplane.

Further, the chimney 13 shown in FIG. 18 (a), the tower 14 shown in FIG. 18 (b), or the bridge pier 15 shown in FIG. 18 (c), or the pillars of a building, For locations where you want to reduce the resistance during strong winds or reduce the resistance of ocean currents and river currents,
It is also preferable to apply the present invention.

Further, as shown in FIG. 19A, the small diameter conduit 16
It is also preferable to form a small cutout 3 in the portion 18 that suddenly expands to the large diameter conduit 17 to reduce the flow resistance. Alternatively, as shown in FIG. 19B, it is preferable to form the cutout small recess 3 in the portion 19 where the large diameter conduit 17 is rapidly reduced to the small diameter conduit 16. That is, the present invention can be applied to the internal flow.

Next, FIG. 20 shows a grid 21 in the duct 20 (in the case of an intermediate flow between the internal flow and the external flow), the cross-sectional shape of which is shown in FIGS. You may do like this. Alternatively, it is also preferably applied to a lattice of an air intake port or an air outlet port.

Further, by applying it to the heat exchanger 22 shown in FIG. 21 (a), the cross-sectional shape of the pipe is changed to that shown in FIG. 21 (b) or (c).
It is also preferable to use a cross pipe having the small cutouts 3 ...

[0041]

The present invention has the following significant effects due to the above-mentioned configuration.

Notch small recess 3 (according to claim 1)
Positively causes flow separation, and controls the flow around an object receiving the flow by the separation flow.
The pressure resistance can be reduced. This recess 3 can be small, and is easy to manufacture (process). Further, since the peeling position is stable, there is an advantage that noise or vibration is not generated.

In addition to the same effect as in claim 1, (according to claim 2), the flow separated once by the vortex G in the notch small recess 3 is drawn toward the object side, and The width (wake area B) may be reduced to reduce pressure resistance.

(According to claim 3) It is often difficult or expensive to process the ridges of a square object, but instead of this, it is necessary to process a small cutout small recess 3. Is easy and cheap. Then, the same effect as that of the above-mentioned claim 1 is obtained.

Claim 3 (according to claim 4)
It is possible to obtain the same effect as described above and further reduce the wake region.

(According to claim 5 or 6) It is possible to reduce the pressure resistance with a simple shape that is the easiest to process.

(According to claim 7) (D-2d)
If the value of / D is smaller than 0.6, the machining of the small cutout concave portion 3 becomes troublesome, and the labor is the same as when processing a round (roundness). On the other hand, when it exceeds 0.95, the notch small recess 3 is too small, the effect of reducing the wake region B is small, and the effect of reducing the pressure resistance cannot be expected so much. Therefore, 0.6 to 0.95 is advantageous because it has a large effect of reducing the pressure resistance and requires a small amount of notching.

[Brief description of drawings]

FIG. 1 is an operation explanatory view.

FIG. 2 is a simplified explanatory sectional view of the present invention.

FIG. 3 is an enlarged sectional view of a main part.

FIG. 4 is a flow chart.

FIG. 5 is another flow explanatory diagram.

FIG. 6 is another flow explanatory diagram.

FIG. 7 is a diagram illustrating a modified example and its flow.

8A and 8B are a graph and an explanatory diagram showing a result of a wind tunnel experiment (actual measurement).

9A and 9B are a graph and an explanatory diagram of a measurement result of an average back pressure coefficient.

10A and 10B are a graph and an explanatory diagram showing a resistance coefficient when the shape of the notched small recess is changed.

FIG. 11 is an explanatory diagram showing various other embodiments.

FIG. 12 is an explanatory view of a main part showing still another various embodiments.

FIG. 13 is a cross-sectional view showing another embodiment.

FIG. 14 is a perspective view showing an application example.

FIG. 15 is a side view showing another application example.

FIG. 16 is an explanatory diagram of another application example.

FIG. 17 is a cross-sectional view of yet another application example.

FIG. 18 is an explanatory diagram showing another application example.

FIG. 19 is an explanatory diagram showing another application example.

[Fig. 20] Fig. 20 is an explanatory diagram showing still another application example.

FIG. 21 is an explanatory diagram of another application example.

[Explanation of symbols]

 1 Peeling position 2 Object receiving flow 3 Notch small recess 4 Front surface 5 Rear surface A Corner D One side length d One side length

Claims (7)

[Claims] 1. A pressure resistance reducing structure characterized in that a cutout small recess (3) is formed at a fluid peeling position (1) or a position immediately before it in an object (2) receiving a flow. 2. A cutout small recess 3 for forming a strong vortex G attracting the separated external flow H is formed at a fluid separation position 1 or a position immediately before it in an object 2 receiving a flow. Pressure resistance reduction structure. 3. A pressure resistance reducing structure characterized in that an object 2 that receives a flow has an angular three-dimensional shape, and a small recess 3 is formed in a ridge on the front surface 4 side of the object 2. 4. A pressure characterized in that an object 2 receiving a flow has an angular three-dimensional shape, and cutout small recesses 3 ... Are formed at the ridge on the front surface 4 side and the ridge on the rear surface 5 side of the object 2. Drag reduction structure. 5. A pressure resistance reducing structure characterized in that the object 2 that receives a flow has a rectangular cross-sectional shape, and rectangular cutout small recesses 3 are formed at both front corners A, A. 6. A pressure resistance reducing structure characterized in that the body 2 receiving a flow has a square cross-sectional shape, and square notch recesses 3, 3 are formed at both front corners A, A. . 7. When one side length of a square of the cross-sectional shape of the object 2 which receives a flow is D and one side length of the square of the cross-sectional shape of the notch small recess 3 is d, (D-2d )
The pressure resistance reducing structure according to claim 6, wherein the value of / D is set to 0.6 to 0.95.