JPH07165156A - Turbulent flow frictional resistance reducing device - Google Patents

Abstract

PURPOSE:To improve the sectional surface shape of a small plate for reducing the frictional resistance which is arranged in parallel to the wall surface, concerning a device for reducing the frictional resistance which a turbulent flow boundary layer set along the wall surface as the outer plate surface of a vessel, aircraft, etc., exeerts on the wall surface. CONSTITUTION:In a turbulent flow boundary layer set along a wall surface 3, a slender small plate 1 is arranged so as to be parallel to the wall surface 3 and so that the longitudinal direction crosses at right angle with the main stream direction of the flow, and the sectional surface shape of the small plate 1 is formed so as to have the max. plate thickness in the rear half part. Accordingly, the swirl layer 4 produced behind the small plate 1 is intensified, and the burst phenomenon that the mixing of fluid is repeated intermittently between the wall surface 3 and the outer edge of the turbulent flow boundary layer is shielded sufficiently, and the swirl layer 5 in the vicinity of the wall surface of the turbulent flow boundary layer is offset by the swirl 4a close to the wall surface of the swirl layer 4, and the frictional resistance of the wall surface 3 is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for reducing the frictional resistance exerted by a turbulent boundary layer along a wall surface on the wall surface, and in particular for ships, aircraft, trains, automobiles, rockets, underwater vehicles, etc. The present invention relates to a turbulent flow frictional resistance reduction device that is preferably attached to an outer plate.

[0002]

2. Description of the Related Art Conventionally, there is a hull friction resistance reducing device as shown in Japanese Patent Publication No. 3-62594, and as shown in FIG. 6 (perspective view) and FIG. Is disposed inside the turbulent boundary layer having a thickness δ so as to be parallel to the wall surface 3 serving as the hull outer plate surface and orthogonal to the direction of fluid flow.

As shown in FIGS. 7 and 8, the mechanism of reducing the frictional resistance by the small plate 1 is such that the vortex layer 4 formed in the wake of the small plate 1 causes the wall surface 3 and the boundary layer outer edge 2 to be separated from each other. It is possible to block (suppress) the burst phenomenon in which fluid mixing is intermittently repeated between the small plates 1, and the vortex direction of the vortex 4a generated near the wall surface 3 behind the small plate 1 is formed near the wall surface 3 in the turbulent boundary layer. The main factor is to weaken the vortex layer 5 by reversing the direction of vortex movement of the vortex layer 5. Even when the small plates 1 are arranged in two rows, the above-described mechanism is the same, and the effect is emphasized more than in the case of one row.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to an improvement of the conventional device as described above, and a turbulent flow friction resistance reducing device for further enhancing the effect of reducing the turbulent flow friction resistance of the wall surface by the small plate. The purpose is to provide.

[0005]

In order to achieve the above-mentioned object, the turbulent frictional resistance reducing device of the present invention is arranged in the turbulent boundary layer of the flow of the fluid along the wall surface slightly apart from the wall surface. A thin friction resistance reducing small plate arranged substantially parallel to the wall surface and having a longitudinal direction substantially orthogonal to the main flow direction of the flow, and a cross-sectional shape of the small plate along the main flow direction,
It is characterized in that it is formed so as to have the maximum plate thickness in the latter half portion.

Further, the turbulent flow friction resistance reducing device of the present invention is characterized in that the cross-sectional shape of the small plate is formed into a triangle having a front edge as an apex and a rear edge as a base.

Further, the turbulent frictional resistance reducing device of the present invention is
The cross-sectional shape of the small plate is characterized in that it is formed in a wing shape having a front edge and a rear edge, respectively.

Further, in the turbulent flow friction resistance reducing device of the present invention, the cross-sectional shape of the small plate has a thick portion mainly on the wall surface side with respect to a straight line drawn parallel to the wall surface from the most apex of the front edge thereof. It is characterized by doing.

[0009]

In the above-described turbulent flow frictional resistance reducing device of the present invention, since the cross-sectional shape of the small plate is formed so as to have the maximum plate thickness in the latter half portion, the vortex layer formed behind the small plate is strong. As a result, the burst phenomenon between the wall surface and the outer edge of the boundary layer can be sufficiently suppressed, and the vortex layer in the vicinity of the wall surface of the turbulent boundary layer can be accurately offset, so that the turbulent frictional resistance of the wall surface is reduced. It will be greatly reduced. And
The cross-sectional shape of the small plate may be, for example, a triangle or a wing shape as described above, but in any case, the vortex layer behind the small plate becomes strong, and for the above reason. The turbulent frictional resistance on the wall surface is reduced.

Further, when the cross-sectional shape of the small plate has a main thick portion on the wall surface side with respect to a straight line drawn parallel to the wall surface from the most apex of the front edge thereof, the small plate is located near the wall surface behind the small plate. The generated vortex becomes stronger, and the vortex layer formed in the turbulent boundary layer in the vicinity of the wall in the opposite direction to the vortex direction of the vortex is accurately offset and the turbulent friction of the wall surface The resistance can be reduced more efficiently.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a turbulent flow friction resistance reducing device as a first embodiment of the present invention, and FIG. 2 shows the operation of the device of FIG. It is an explanatory view shown.

As shown in FIGS. 1 and 2, two rows of elongated small plates 1 and 1 are slightly separated from the wall surface 3 in a turbulent boundary layer of water flow along the wall surface 3 such as the outer plate surface of the hull. Separated and same wall 3
Are arranged so as to be substantially parallel to and the longitudinal direction thereof is substantially orthogonal to the main flow direction of the flow. Both ends of each small plate 1 are supported on the wall surface 3 by support members (not shown). And, the cross-sectional shape of the small plate 1 along the main flow direction of the flow is formed so as to have the maximum plate thickness in the latter half portion. Specifically, in the case of the present embodiment, specifically, the cross-sectional shape of the small plate 1 is: It is formed in a triangle with the leading edge as the apex and the trailing edge as the base.

Due to the sectional shape of the small plate 1 as described above, in this first embodiment, as shown in FIG. 2, the vortex layer 4 behind the small plate 1 becomes strong, which causes the wall surface 3 and the turbulent flow. Since it becomes possible to sufficiently block and suppress the burst phenomenon in which fluid mixing is intermittently repeated with the outer edge of the boundary layer, the vortex 4a near the wall surface 3 of the vortex layer 4 has a vortex direction near the wall surface 1. The turbulent flow frictional resistance of the wall surface 3 is significantly reduced in combination with the vortex layer 5 formed in the turbulent boundary layer in the direction opposite to the vortex direction and weakening the vortex layer 5. Also in the case of the second embodiment of the present invention shown in FIG. 3, the small plate 1 arranged along the wall surface 3 has the maximum plate in the latter half of the sectional shape along the main flow direction of the flow as in the first embodiment. It is formed to have a thickness, and specifically, the cross-sectional shape is formed in a wing shape having a tip at each of a leading edge and a trailing edge.

Also, in the case of the second embodiment, the same operational effect as that of the first embodiment described above can be obtained, and the small plate 1 itself is formed by forming the small plate 1 in a wing shape. There is also an effect that the resistance can be reduced.

Next, a third embodiment of the present invention shown in FIG. 4 will be described. Also in the case of this embodiment, the small plate 1 is a turbulent boundary of the flow of water along the wall surface 3 such as the outer plate surface of the hull. In layers,
It is arranged slightly apart from the wall surface 3 so as to be substantially parallel to the wall surface 3 and the longitudinal direction thereof is substantially orthogonal to the main flow direction of the flow. In addition to being formed in the shape of a wing having a tip at each of the edge and the trailing edge, with respect to a straight line b drawn parallel to the wall surface 3 from the most apex a at the leading edge, the main thick portion is thickened on the wall surface 3 side. have.

Therefore, in this third embodiment, the small plate 1
Generated behind the wall near the wall 3 (see symbol 4a in Fig. 2)
Becomes stronger, and the vortex layer (see reference numeral 5 in FIG. 2) formed in the turbulent boundary layer in the vicinity of the wall surface 3 in the direction opposite to this vortex is accurately offset, and Three
The turbulent frictional resistance of is reduced more efficiently.
Further, in the fourth embodiment of the present invention shown in FIG. 5, the third embodiment of FIG.
Although the small plate 1 is provided according to the same idea as that of the embodiment, the cross-sectional shape of the small plate 1 is a triangle, and the thick portion is formed only on the wall surface 3 side with respect to the straight line b similar to the above.
The aforementioned vortex (4a) is further strengthened, which allows the vortex layer (5) of the turbulent boundary layer to be sufficiently offset, and
Although its resistance is slightly increased, the structure is greatly simplified.

[0017]

As described above in detail, according to the turbulent flow frictional resistance reducing device of the present invention, the following effects can be obtained. (1) Since the cross-sectional shape of the small plate is formed so as to have the maximum plate thickness in the latter half part, the vortex layer formed behind the small plate becomes strong, and as a result, between the wall surface and the outer edge of the boundary layer. In addition to sufficiently suppressing the burst phenomenon in, the vortex layer near the wall surface of the turbulent boundary layer can be canceled exactly.
The turbulent frictional resistance on the wall surface is significantly reduced. (2) When the cross-sectional shape of the small plate is formed in a triangle with the front edge as the apex and the rear edge as the bottom side, the effect of the above (1) can be obtained and the small plate can be easily manufactured. There is also an advantage. (3) If the cross-sectional shape of the small plate is formed in a wing shape having a tip at each of the leading edge and the trailing edge,
In addition to the effect of item (1), there is also an advantage that the resistance of the small plate itself is reduced. (4) If the cross-sectional shape of the small plate has a main thick part on the wall surface side with respect to the straight line drawn in parallel with the wall surface from the most apex of its front edge, it should be closer to the wall surface behind the small plate. The generated vortex becomes stronger, and the vortex layer formed in the turbulent boundary layer near the wall in the direction opposite to the vortex direction of the vortex is properly offset and the turbulent friction of the wall surface is eliminated. The resistance can be reduced more efficiently.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a turbulent flow frictional resistance reduction device as a first embodiment of the present invention.

FIG. 2 is an explanatory view showing the operation of the apparatus of FIG.

FIG. 3 is an explanatory view schematically showing a turbulent flow frictional resistance reduction device as a second embodiment of the present invention.

FIG. 4 is an explanatory view schematically showing a turbulent flow frictional resistance reduction device as a third embodiment of the present invention.

FIG. 5 is an explanatory diagram schematically showing a turbulent flow frictional resistance reduction device as a fourth embodiment of the present invention.

FIG. 6 is a perspective view schematically showing a conventional turbulent flow frictional resistance reduction device.

7 is a cross-sectional view of the device of FIG.

FIG. 8 is an explanatory view showing the operation of the apparatus of FIG.

[Explanation of symbols]

 1 small plate 2 turbulent boundary layer outer edge 3 wall surface 4 vortex layer 4a vortex 5 turbulent boundary layer vortex layer

Claims (4)

[Claims] 1. A turbulent boundary layer for a fluid flow along a wall surface is arranged at a distance from the wall surface so as to be substantially parallel to the wall surface and the longitudinal direction thereof is substantially orthogonal to the main flow direction of the flow. A turbulent flow friction resistance reduction device comprising an elongated friction resistance reduction small plate, wherein the cross-sectional shape of the small plate along the mainstream direction has a maximum plate thickness in the latter half. 2. The turbulent flow friction resistance reducing device according to claim 1, wherein the cross-sectional shape of the small plate is formed in a triangle having a front edge as an apex and a rear edge as a bottom side. , Turbulent friction resistance reduction device. 3. The turbulent flow frictional resistance reduction device according to claim 1, wherein the cross-sectional shape of the small plate is formed in a wing shape having a tip at each of a front edge and a rear edge. A turbulent friction resistance reduction device. 4. The turbulent flow friction resistance reducing device according to claim 2 or 3, wherein the cross-sectional shape of the small plate is on the wall surface side with respect to a straight line drawn in parallel with the wall surface from the most apex of the front edge thereof. A turbulent flow friction resistance reducing device having a main thick portion.