JP5590443B2 - Moving body outer wall - Google Patents

Description

The present invention relates to a mobile outside wall, yo Ri in particular, aircraft, high speed trains, and mounted on the surface of the high-speed moving bodies such as a ship, a fluid air or water or the like into contact with the surface of the fast-moving objects It is related with the structure of the outer wall of a mobile body which reduces the frictional resistance of this, and significantly reduces energy consumption, such as a fuel required for propulsion.

As is well known, high-speed transportation equipment such as high-speed trains such as airplanes, bullet trains, and ships, and linear motor cars that will be realized in the future are used to transport fuel and cargo in order to transport passengers and cargo at high speed and in large quantities. It consumes a lot of power. For enterprises that operate these high-speed transportation equipment, reducing energy consumption such as electricity and fuel not only improves the profit margin of the enterprise, but also burdens Japan to import most of the energy from other countries. It is extremely important for reducing the environmental load and reducing the environmental load.
Attempts to reduce the energy consumption of high-speed transport equipment have been studied at all angles and technology has evolved. There are roughly three approaches to improving the energy efficiency of high-speed transportation equipment. One approach is to improve the energy efficiency of engines and motors that provide propulsion for high-speed transport equipment. Another approach is to reduce the weight of high-speed transportation equipment. The last one is an approach for reducing frictional resistance with a fluid such as air or water that comes into contact with the airframe of a high-speed transport device. This specification refers to the last frictional resistance.

JP 2002-266816 A

Science & Technology Trends September 2006 feature article 02: [Search February 23, 2010], Internet <URL: http://www.nistep.go.jp/achiev/ftx/jpn/stfc/stt066j/0609_03_featurearticles/0609fa02/200609_fa02. html>

Conventional attempts to reduce the frictional resistance of high-speed transportation equipment include, in addition to classical fluid friction reduction methods such as streamline the airframe, as well as providing streaky irregularities along the fluid flow on the airframe surface. A method based on hydrodynamics has been proposed.
In particular, as disclosed in Patent Document 1 and Non-Patent Document 1, various attempts have been made to reduce the fluid friction resistance by providing ridge-shaped riblets on the surface of the outer wall of the moving body. Shapes have been proposed. However, it is known that any of these methods has a limit in the improvement effect.

The present invention solves the problem of only implemented in conventional aircraft surfaces can be reduced fluid friction resistance, to improve the energy efficiency, and to provide a novel moving outside wall.

但し、νは、移動体外壁に接触する流体の動粘度、τ _ｗ は航速度及び移動体の進行方向の長さから計算した壁面摩擦応力τ _ｗ 、ρは流体の密度ρである。 In order to solve the above-mentioned problems, the outer wall of the moving body of the present invention has a uniform period length with respect to the fluid flow direction , and is a first meandering left and right at equal intervals with respect to the orthogonal direction of the fluid flow. A rib and a second rib meandering left and right in a line-symmetric shape in the flow direction with respect to the first rib are provided on the surface . The period length of the first rib and the second rib is Lx, the distance between the closest positions of the first rib and the second rib is Lz, and the height of the first rib and the second rib Where Lx, Lz, and h satisfy the following formula.

Where ν is the kinematic viscosity of the fluid in contact with the outer wall of the moving body, τ _w is the wall friction stress τ _w calculated from the navigation speed and the length of the moving body in the traveling direction , and ρ is the density ρ of the fluid.

  A riblet in which a wide portion and a narrow portion are regularly repeated in the fluid flow direction is provided on the surface of the moving body. As the fluid flows along the riblet, regular vibration is added to the turbulent flow generated between the fluid and the airframe surface, the turbulence is reduced, and the fluid friction is reduced.

By the present invention lever, simply implemented in conventional aircraft surfaces can be reduced fluid friction resistance, to improve the energy efficiency, you to provide a novel moving outside wall.

It is a perspective view of the movable body outer wall which is embodiment of this invention. It is the figure which looked at the moving body outer wall from the top, and sectional drawing of a moving body outer wall. It is an external view of the aircraft which mounts the mobile body outer wall of this embodiment. It is a graph explaining the relationship between the length of the mobile body outer wall of this embodiment, and a frictional resistance reduction effect. It is the schematic which shows another embodiment of a moving body outer wall.

FIG. 1 is a perspective view of a moving body outer wall according to an embodiment of the present invention.
On the surface of the moving body outer wall 101, a rib-shaped riblet 102 is provided.
The fluid flows on the surface of the moving body outer wall 101 in the direction of arrow A105. The riblet 102 is configured by alternately arranging A ribs 103 that meander to the left and right periodically along the fluid flow direction and B ribs 104 that meander to the left and right in a pattern opposite to that of the A ribs 103. The

2A and 2B are a top view of the moving body outer wall 101 and a cross-sectional view of the moving body outer wall 101. FIG.
2A is a top view of the movable body outer wall 101, and FIG. 2B is a cross-sectional view of the movable body outer wall 101 seen from the line aa ′ in FIG.
As can be seen from FIGS. 1 and 2A, the A rib 103 and the B rib 104 are line symmetric in the direction of fluid flow.
The shape and arrangement relationship of the A rib 103 and the B rib 104 are configured by the following parameters shown in FIGS.
The length Lx in the fluid flow direction of the A rib 103 and the B rib 104
The inclination angle θ of the A rib 103 and the B rib 104 with respect to the fluid flow direction
The width Lz of the narrowest part of the A rib 103 and the B rib 104
・ Height h of A rib 103 and B rib 104
・ Thickness T of A rib 103 and B rib 104

  The thinner the thickness T, the better. Actually, it is determined in consideration of the height h in order to ensure the rigidity of the riblet 102 and due to restrictions in the manufacturing process.

  As a result of DNS, the following values of the width Lz, length Lx, and height h were found to be optimal.

  The constants “215.98”, “14.75”, and “7.5” in the above equation (1) are considered to be effective with a margin of about 30% in the vertical direction from the DNS result. Therefore, the above equation (1) can be rewritten as follows.

上記（１）式のパラメータのうち、動粘度ν及び流体密度ρは、対象の移動体周囲の流体が決まれば、流体の種類と温度、圧力等で一意に決まる。
壁面摩擦応力τ_ｗは、例えば以下の式で決定される。

Among the parameters of the above equation (1), the kinematic viscosity ν and the fluid density ρ are uniquely determined by the type of fluid, temperature, pressure, and the like if the fluid around the target moving body is determined.
Wall friction stress tau _w is determined, for example, by the following equation.

Or more precisely, since τ _w changes according to the position x in the flow direction, it can be determined in detail by the following equation.

First, the flow direction length L of the moving body is obtained, the cruise speed U _lam of the moving body is determined, and the kinematic viscosity ν of the fluid and the density ρ of the fluid are calculated. Next, the wall friction stress tau _w, is calculated in the above (3) or (4). as long obtained tau _w, it can be obtained above (1) in a width Lz, a length Lx and height h. Although the angle θ is currently 7.5 °, there is still room for optimization.

FIG. 3 is an external view of an aircraft on which the movable body outer wall 101 of this embodiment is mounted.
When the present invention is applied to the aircraft 301, the outer wall structure shown in FIGS. 1 and 2 is provided on the entire body including both wings.
As an example, a calculation result when the present invention is applied to an actual moving body will be described. The case of Boeing 777-300 is described as an aircraft.
The width Lz, length Lx, and height h were 81 μm, 1.2 mm, and 41 μm, respectively.

FIG. 4 is a graph for explaining the relationship between the length of the moving body outer wall 101 of the present embodiment and the frictional resistance reduction effect. It is the data obtained as a result of the experiment.
The horizontal axis of the graph is the length of the moving body outer wall 101, and the vertical axis is the frictional resistance reduction effect. In the graph, δ is about 10 mm.
It can be clearly seen that the frictional resistance reduction effect increases as the length of the moving body outer wall 101 increases.

  As described above, the riblet 102 is attached to the movable body outer wall 101. The shape of the riblet 102 can be calculated based on the cruise speed of the moving body, the kinematic viscosity of the fluid, and the length of the moving body in the direction of movement of the fluid based on the above-described arithmetic expression. A frictional resistance reducing effect is produced on the outer wall 101 of the movable body provided with the riblet 102 whose shape is determined in this way.

The material and manufacturing method of the riblet 102 are not particularly limited. Since there are no moving parts, the riblet 102 can be formed into micrometer-order minute riblets, and any material and manufacturing method can be used as long as the riblet is not damaged by fluid or dust. There may be.
For example, a general process for forming minute protrusions on the wall surface, such as a stamping process using a synthetic resin, an etching process of a synthetic resin or metal, or an application process using a paint containing putty, is used. Various riblet forming methods can be used.
Further, as disclosed in Non-Patent Document 1, a method of sticking the sheet on which the riblets 102 are formed to the movable body outer wall 101 may be used.

In this embodiment, the following application examples can be considered.
(1) The shape of the riblet is not necessarily a linear shape as shown in FIG. 1 because the wide portion and the narrow portion only have to appear periodically in the direction of fluid flow.
FIG. 5 is a schematic view showing another embodiment of the moving body outer wall. That is, the riblet 502, the A rib 503, and the B rib 504 may have a curved shape such as a sine curve as shown in FIG.

In this embodiment, the movable body outer wall 101 was disclosed.
A riblet 102 for generating a periodic change with respect to the fluid is provided on the surface of the moving body outer wall 101. The shape of the riblet 102 is determined by a cycle calculated based on the kinematic viscosity of the fluid, the cruising speed of the moving body, and the length of the moving body in the moving direction of the fluid. By covering the entire moving body outer wall 101 with the riblet 102, the disturbance of the fluid surrounding the moving body outer wall 101 is reduced, and the fluid friction can be reduced by about 20% at the maximum.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and other modifications, Includes application examples.

  DESCRIPTION OF SYMBOLS 101 ... Mobile body outer wall, 102 ... Riblet, 103 ... A rib, 104 ... B rib, 301 ... Aircraft, 502 ... Riblet, 503 ... A rib, 504 ... B rib

Claims (1)

A first rib that meanders to the left and right at regular intervals in the direction of fluid flow and at equal intervals in the direction perpendicular to the flow;
A second rib meandering left and right in the shape of line symmetry in the flow direction with respect to the first rib ;
The periodic length of the first rib and the second rib, the interval between the closest positions of the first rib and the second rib, and the height of the first rib and the second rib Is the cruising speed and the length of the moving body in the traveling direction, where Lx is the period length, Lz is the distance between the closest points, h is the height, and v is the kinematic viscosity of the fluid contacting the outer wall of the moving body. To obtain the wall friction stress τ _w from the density ρ of the fluid,

The outer wall of the moving body obtained in

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