JP2015197293A - Fluid resistance measurement method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device capable of accurately measuring the fluid resistance of swimwear fabric and the like.SOLUTION: In the fluid resistance measurement method of the present invention, first, fabric or material is attached to the outer surface of a cylindrical part of a cylindrical substrate (1) of a density higher than the water density. Then, (A) the cylindrical substrate (1) is dropped into a static water (12) in a water tank (11) in a state in which the substrate (1) is erected, and the time when the tip of the cylindrical substrate (1) travels a predetermined drop distance is measured. Alternatively, (B) the cylindrical substrate (1) is dropped from an air medium into a static water (12) in a state in which the substrate (1) is erected, and the drowning period since the tip of the cylindrical substrate (1) comes into contact with the water surface until the rear end enters water is measured. Then, the time or drowning period is used as an evaluation value of the fluid resistance of the surface of the fabric or material.

Description

  The present invention relates to a method and apparatus capable of measuring a fluid resistance such as a swimsuit.

One function required for materials such as swimwear fabrics and swimming caps is to reduce the surface frictional resistance in water that occurs during swimming. For this purpose, it is necessary to grasp the surface frictional resistance in water. Conventionally, methods for measuring the fluid resistance of a swimsuit have been proposed. Patent Document 1 discloses a method in which a fabric of a swimsuit is attached to the surface of an aluminum circular tube adjusted to an apparent specific gravity of 0.68 g / cm ³ , is placed in a water stream while being supported by a thread, and the fluid resistance is measured from the tension of the thread. Has been proposed. Patent Document 2 proposes a method of calculating fluid resistance by pasting a swimsuit cloth on the surface of a plate, placing it in a water flow, and measuring the strain of the plate.

Japanese Patent Laid-Open No. 7-63749 WO2007 / 142232

  However, the conventional fluid resistance measurement methods and apparatuses all require an operation of flowing a fluid around the object to be measured. If the fluid resistance varies depending on the flow velocity of the fluid or if turbulent flow occurs, the fluid resistance is greatly affected. Therefore, there is a problem that accurate measurement is difficult, and further development of an accurate method has been desired.

  The present invention provides a method and an apparatus capable of measuring an accurate fluid resistance of a swimsuit fabric or a material in order to solve the conventional problems.

The fluid resistance measuring method of the present invention is a method for measuring the fluid resistance of the fabric or material surface in the inside, wherein the fabric or material is attached to the outer surface of the cylindrical portion of the cylindrical base having a density heavier than the density of water. (A) The cylindrical base body is dropped and placed in static water in a water tank, and the time for the tip of the cylindrical base body to pass a predetermined drop distance is measured, or (B) the cylindrical base body Measure the water entry time from when the tip of the cylindrical substrate contacts the water surface until the rear end is submerged.
It is set as the evaluation value of the fluid resistance of the cloth or material surface.

  The fluid resistance measuring device of the present invention is a fluid resistance measuring device for carrying out the above-described fluid resistance measuring method, and can attach a cloth or a material to the outer surface of the cylindrical portion and is heavier than the density of water. A cylindrical base body having a density, a water tank, a high-speed camera, and (A) the cylindrical base body is dropped and placed in still water in the water tank, and the tip of the cylindrical base body passes a predetermined drop distance. Or a means for measuring time, or (B) the cylindrical base body is dropped and placed in air standing still, and the rear end of the cylindrical base body is submerged after the front end of the cylindrical base body contacts the water surface. Means for measuring the water entry time until the fluid resistance is evaluated as a fluid resistance evaluation value on the surface of the fabric or material.

  In the present invention, since the cylindrical base body is dropped in the still water in the water tank, the falling speed and acceleration in water can be measured in a stable state at all times. That is, it is possible to accurately measure the time required for the tip of the cylindrical substrate to pass a predetermined drop distance, and to calculate the frictional resistance value with high accuracy and accuracy. This can be evaluated as the frictional resistance value of swimsuit fabrics and materials in water, and is useful for the development of swimsuit fabrics.

  In addition, the cylindrical base body is dropped from the air in a standing state and can be measured by measuring the water entry time from when the front end of the cylindrical base body contacts the water surface until the rear end is submerged. It can be set as an evaluation value of the fluid resistance of the cloth or material surface. This can be evaluated as the frictional resistance value of swimsuit fabrics and materials when jumping into the water from the air, and is useful for the development of swimsuit fabrics and materials.

FIG. 1A is a side view of a cylindrical substrate according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line II. FIG. 2 is an explanatory view showing an apparatus for measuring the time during which the cylindrical substrate falls in water. FIG. 3 is an explanatory view showing a method and an apparatus for measuring the time during which the cylindrical substrate falls for a predetermined distance in water. FIG. 4 is an explanatory view showing a method and apparatus for measuring the time until a cylindrical substrate enters water from the air in another embodiment of the present invention. FIG. 5A is a perspective view when a cylindrical substrate is developed in one embodiment of the present invention, and FIG. 5B is a plan view of the same. FIG. 6 is a schematic plan view of a stretch fabric in which plain weave portions and weft double weave portions are alternately repeated according to an embodiment of the present invention. FIG. 7A is a schematic plan view of the stretch fabric, and FIG. 7B is a cross-sectional view thereof. FIG. 8 is a schematic front view of a swimsuit using the stretch fabric. FIG. 9 is a schematic back view of a swimsuit using the stretch fabric.

  The cylindrical substrate used in the present invention will be described. In order to measure the frictional resistance of the fabric or material surface attached to the cylindrical substrate, remove the influence of the shape resistance as much as possible. For that purpose, for example, a three-dimensional pencil type drop model with a cross-sectional shape resembling an airfoil was created. Unlike a sphere, it has an elongated shape with the drop direction as the major axis, the front part is hemispherical, and the rear part is a pencil type, which greatly reduces the shape resistance. Moreover, since the fall distance can be measured shortly, the effect of the additional mass that should be considered originally can be omitted with unsteady motion. Therefore, it is possible to evaluate the cloth and material worn in a cylindrical shape by this system and the frictional resistance of the surface state.

  The size of the cylindrical substrate used in the present invention is, for example, 30 mm in diameter and 300 mm in length, and the portion on which the fabric is mounted is 200 mm. In this example, the weight of the cloth to be worn is 88 g including the cloth to be worn, and a weight is attached to the inside of the base in consideration of the buoyancy of the cloth and the model so that the weight in water is 0.3N. A stainless steel pipe passes through the center of the cylindrical substrate, and a wire passes through it. As a result, the cylindrical base body falls straight, and the frictional resistance between the wire and the stainless steel pipe can be ignored.

In the present invention, the following two types of measurement methods can be implemented.
(1) The first is to measure the frictional resistance of the swimsuit fabric in water. The measurement reference point is marked with a laser pointer from the side of the water tank, and the two points below the reference point pass through the cylindrical substrate on which the swimsuit fabric is worn. Is measured from the high-speed image, and the speed and acceleration through which the model passes at two points are measured. Using this speed and acceleration, the surface resistance is calculated using an equation of motion that introduces the unsteady effect, taking into account the model mass and buoyancy. Thereafter, an unsteady resistance coefficient is calculated and evaluated for each worn swimsuit fabric.
(2) Second, the resistance evaluation when entering the water from the air. Drop the model wearing the swimsuit fabric from the air above the surface of the water, let it enter from the surface of the water, and from the tip to the rear end of the cylindrical substrate The time to enter the water is taken as the water entry time and measured from high-speed camera photography. The water entry time is evaluated as the resistance acting on the surface, and the resistance acting on the water entering the water from the air of each swimsuit fabric is evaluated as an index indicating that the shorter the water entry time is, the smaller the resistance is.

  The cylindrical substrate preferably has a spherical tip at the tip and a tapered tip at the rear end. If the tip is spherical, it is difficult to receive water resistance. Further, when the rear end is tapered, turbulent flow hardly occurs, and it is easy to fall linearly downward in water.

  The cylindrical base body preferably has a mass at the front end side and the rear side. If there is a mass at both ends, the moment of inertia will increase, and it will be easy to fall straight down in the water.

The density of the cylindrical substrate is preferably 1000 to 1200 kg / m ³ . If it is the said range, it will become a moderate fall speed. The mass of the cylindrical substrate is preferably about 50 to 200 g.

  The cylindrical substrate preferably has at least one shape whose cross section is selected from a circle, an ellipse, an ellipse and a flat circle. Among these, when the cross section is a flat circular shape, a three-dimensional pencil-type drop model resembling an airfoil can be obtained.

  The distance for measuring the drop time of the cylindrical substrate may be any length, but as an example, a specific value within a range of 100 mm to 500 mm is preferable. For example, it is 200 mm. It is preferable to measure the fall time by photographing this distance with a high-speed camera at high speed. If it is the said length, high-speed camera can image | photograph at high speed and it can measure a fall time correctly. The shooting speed of the high-speed camera is preferably 1000 to 5000 fps, and more preferably 1500 to 3000 fps.

  In the present invention, any object can be measured as long as it can be attached to, for example, a swimsuit cloth, a cap material, or any other device.

This will be described below with reference to the drawings. In the following drawings, the same symbols indicate the same items. FIG. 1A is a side view of a cylindrical substrate according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line II. The front end 3 of the cylindrical base body (model) 1 is spherical and the rear end 4 is tapered. A swimsuit fabric sample 9 is attached to the cylindrical portion 2. The area of the dough sample 9 attached to the cylindrical portion 2 is about 0.016 mm ² . A weight 5 is inserted into the lower portion of the cylindrical portion 2. A hollow portion (pipe) 6 is placed in the shaft portion of the cylindrical base body (model) 1 and a wire 7 is inserted therein as shown in FIG.

  FIG. 2 is an explanatory view showing an apparatus 10 for measuring the time during which the cylindrical substrate falls in water. Water 12 is put in a transparent water tank 11 made of acrylic resin or the like. A shielding sheet 13 is pasted on the back side of the water tank 11, a lamp 14 is arranged on the rear side, and a high speed camera 15 is arranged on the front side. In this state, the cylindrical substrate (model) 1 is gently dropped from above the water tank. The cylindrical base body (model) 1 falls along the wire 7.

  FIG. 3 is an explanatory view showing a method and an apparatus for measuring the time during which the cylindrical substrate falls for a predetermined distance in water. First, the cylindrical base body (model) 1 is arranged so that the rear end thereof is located on the water surface, the laser spot 17 is 200 mm below the tip 16, the first measurement point 18 is 100 mm below, and the second measurement is 100 mm below. Let it be point 19. The laser spot 17 has a hole in the shielding sheet 13 shown in FIG. In such a state, the cylindrical base body (model) 1 is gently dropped, and when the tip 16 passes the laser point 17, the high-speed camera is turned on, and the first measurement point 18 to the second measurement point are turned on. Measure the time to drop to 19. The measurement is performed 10 times per sample and the average value is used. The acceleration is obtained from the following calculation formula (Equation 1).

ｕ₁＝ｋ₁／ｔ₁
ｕ₂＝ｋ₂／ｔ₂
Δｔ＝ｔ₂
（但し、ｋ₁は図３のレーザ点から第１測定ポイントまでの落下距離（ｍｍ）、
ｔ₁は図３のレーザ点から第１測定ポイントまでの通過時間（秒）、
１₂ は第１測定ポイント１８から第２測定ポイント１９までの落下距離（ｍｍ）、
ｔ₁は第１測定ポイント１８から第２測定ポイント１９までの通過時間（秒）。
本例の場合ｋ₁は２００ｍｍ、ｋ₂は１００ｍｍとした。）

u ₁ = k ₁ / t ₁
u ₂ = k ₂ / t ₂
Δt = t ₂
(Where k ₁ is the drop distance (mm) from the laser point of FIG. 3 to the first measurement point,
t ₁ is the passage time (seconds) from the laser point to the first measurement point in FIG.
1 ₂ is a drop distance (mm) from the first measurement point 18 to the second measurement point 19;
t ₁ is the passage time (seconds) from the first measurement point 18 to the second measurement point 19.
In this example, k ₁ is 200 mm and k ₂ is 100 mm. )

The frictional resistance coefficient C _f of the swimsuit fabric in water is calculated by the following equations (Equation 2) and (Equation 3). Measurement accuracy of the frictional resistance coefficient C _d may be issued to a value of 0.001.

但し、Ｗは重力でＷ＝ｍｇ（ｍは円筒状基体の質量（ｋｇ），ｇは重力加速度（ｍ／ｓ²））
Ｂは浮力でＢ＝ρ_wｇＶ（ρ_wは水の密度（ｋｇ／ｍ³），Ｖは円筒状基体の体積（ｍ³））
Ｄは抵抗でＤ＝Ｃ_f×（１／２）×ρｕ²Ａ（Ｃ_dは水着生地の摩擦抵抗係数，ρは水の密度，ｕは落下速度，Ａは水着生地の表面積）

Where W is gravity and W = mg (m is the mass of the cylindrical substrate (kg), g is gravitational acceleration (m / s ² ))
B is buoyancy, B = ρ _w gV (ρ _w is the density of water (kg / m ³ ), V is the volume of the cylindrical substrate (m ³ ))
D is resistance and D = C _f × (1/2) × ρu ² A (C _d is the frictional resistance coefficient of the swimsuit fabric, ρ is the density of water, u is the falling speed, and A is the surface area of the swimsuit fabric)

FIG. 4 is an explanatory view showing a method and apparatus for measuring the time until a cylindrical substrate (model) enters water from the air in another embodiment of the present invention. A cylindrical base body (model) 1 is made to enter water 12 in a water tank from the air. Before entering the water, the swimsuit fabric may be soaked in water for about 1 minute in advance. The description of each step in FIG. 4 is as follows.
(A) State in which cylindrical base body (model) 1 is present in the air (b) State in which tip of cylindrical base body (model) 1 has landed (t ′ ₀ )
(C) to (d) showing a state of entering water (e) a state in which the cylindrical substrate (model) 1 is submerged (t ′ ₁ )

Using a high-speed camera, the times t ₀ and t ₁ are measured. The water entry time T is obtained using the following equation (Equation 4). It can be evaluated that a material sheet having a short water entry time has a low frictional resistance when diving, for example.

  FIG. 5A is a perspective view when a cylindrical substrate is developed in one embodiment of the present invention, and FIG. 5B is a plan view thereof. In order to attach the dough sample, the dough is wound around the cylindrical portion 2, pressed by the cylindrical jigs 8a and 8b, and the front end portion 3 and the rear end portion 4 are inserted.

  The present invention will be specifically described below with reference to examples. The present invention is not limited to the following examples.

<Friction resistance evaluation test>
The weight of the cylindrical substrate (model) 1 shown in FIG. 1 in water was 0.3 N with a swimsuit cloth attached, and the volume was 1.2 × 10 ⁻³ m ³ . The whole is made of resin. The hollow portion 6 has a diameter of 2.3 mm. Model 1 had a diameter of 30 mm and a length of 300 mm, and the part to which the fabric was attached was 200 mm. The mass was set to 88 g including the attached fabric sample, and a weight was attached to the inside of the substrate in consideration of the buoyancy of the fabric and model, so that the weight in water was 0.3 N.

  The water tank 11 shown in FIG. 2 is made of a transparent acrylic resin, has a height (H) of 1.7 m, a width (L) and a depth of 0.22 m, and the high-speed camera 15 is 4.25 m away from the water tank. And, it was arranged at a height of 0.85 m from the floor. The shooting speed of the high-speed camera 15 was 1900 fps. In this state, the measurement shown in FIG. 3 was performed, and the frictional resistance coefficient of the swimsuit fabric was measured using the above equations (Equations 1 to 3).

<Incoming time>
Using the measurement apparatus shown in FIG. 4, the water entry time of the swimsuit fabric was measured using the above equation (Equation 4).

<Elongation rate>
Measured according to JIS L1096 A method cut strip method. The width of the test piece was 5 cm and the holding interval was 20 cm. The initial load was a load corresponding to gravity applied to a length of 1 m in the width of the test piece. The tensile speed was 20 cm / min. The elongation percentage (%) when loaded with 17.7 N (1.8 kg) was measured. The elongation rate indicates stretch properties.

<Stress at 30% elongation>
The stress (N) at the time of 30% elongation at the time of measuring the elongation rate in the warp and weft directions was measured and converted to 1 cm and displayed as N / cm. The stress at 30% elongation is a standard for evaluating the compression function.

(Example 1)
This example is an example of a fabric.
1. Thread usage (1) Warp core: Polyurethane (Finety 44decitex)
Covering yarn: nylon filament wooly processed yarn (fineness 33decitex, 48 filaments)
Single covering yarn (SCY)
(2) Weft core: Polyurethane (fineness 44decitex)
Covering yarn: nylon filament wooly processed yarn (fineness 33decitex, 48 filaments)
Single covering yarn (SCY)
2. Fabric A stretch fabric 21 in which plain weave portions 22 and weft double weave portions 23 shown in FIGS. 6 to 7 are alternately repeated is woven. Using an air jet loom, the warp density of the plain weave portion 22 is 186 pieces / inch, the weft density is 164 pieces / inch, the weight per unit area (weight per unit area) is 144 g / m ² , the same thickness is 0.25 mm, and the entire woven fabric. The finished width was 116 cm.

  The stretch rate of this woven fabric was 64.8% in the warp direction, 65.5% in the weft direction, and the stress at 30% elongation was 0.76 N / cm in the warp direction and 0.88 N / cm in the weft direction. This fabric is called plain fabric.

  Next, the surface of the plain woven fabric was smoothed. The smoothing process is a process of heating and pressing between a pair of rolls, and the roll temperature is 220 ° C., the linear pressure is 5500 kgf, and the roll speed is about 6 to 10 m / min. This fabric is called a calendered product.

  The frictional resistance coefficient and the water entry time of the plain fabric and the calendered product were as shown in Table 1.

  A female swimsuit for swimming shown in FIGS. 8 to 9 was sewn using the plain fabric and the calendered product. When this swimsuit was subjected to a wear test, it was confirmed that the swimsuit was suitable for swimming because of its high stretchability and ease of wearing, and good adhesion to the human skin.

(Example 2)
This embodiment is an example of a half tricot knitted fabric.
(1) Front polyester (fineness 56 decitex, 24 filaments)
(2) Back polyurethane (fineness 44 decitex)
(3) Knitting structure wale: 80 yarns / inch, weft density: 112 yarns / inch Weight per unit area (weight) 245 g / m ² , the same thickness 0.60 mm, and the finished width of the entire woven fabric was 165 cm . The elongation rate was 129.5% in the warp direction, 90.3% in the weft direction, and the stress at the time of 30% elongation was 0.98 N / cm in the warp direction and 0.49 N / cm in the weft direction. This knitted fabric is called a plain knitted fabric. In addition, a calendar processed product was also prepared as in Example 1. The frictional resistance coefficient and the water entry time of the plain knitted fabric and the calendered product were as shown in Table 2.

  A female swimsuit for swimming shown in FIGS. 8 to 9 was sewn using the plain knitted fabric and the calendar processed product. When this swimsuit was subjected to a wear test, it was confirmed that the swimsuit was suitable for swimming because of its high stretchability and ease of wearing, and good adhesion to the human skin.

  As described above, the frictional resistance evaluation test of the present invention is a highly accurate measurement test, and is useful as an evaluation test for swimsuit fabrics and materials in water. In addition, a drop test with a cylindrical substrate upright could be evaluated as a frictional resistance value of a swimsuit fabric or material when jumping into the water from the air, confirming that it was useful for the development of swimsuit fabric and material.

1 Cylindrical substrate (model)
2 Cylindrical part 3, 16 Model tip 4 Model rear end 5 Weight 6 Hollow part (pipe)
7 Wire 8a, 8b Cylindrical jig 9 Dough sample 10 Friction resistance measuring device 11 Water tank 12 Water 13 Shielding sheet 14 Lamp 15 High speed camera 17 Laser point 18 First measurement point 19 Second measurement point

Claims (8)

A method for measuring the fluid resistance of a fabric or material surface in water,
Attach the fabric or material to the outer surface of the cylindrical part of the cylindrical base with a density heavier than that of water,
(A) The cylindrical base body is dropped in standing water in a water tank, and the time required for the tip of the cylindrical base body to pass a predetermined drop distance is measured, or (B) the cylindrical base body is Drop in standing water from standing air, measure the water entry time from the end of the cylindrical substrate contacting the water surface until the rear end is submerged,
A fluid resistance measuring method, characterized in that an evaluation value of fluid resistance on the surface of a cloth or material is used.   The fluid resistance measuring method according to claim 1, wherein the cylindrical base has a spherical front end and a tapered rear end. The fluid resistance measuring method according to claim 1 or 2, wherein a rear end of the cylindrical base body is tapered and an angle thereof is 10 degrees to 30 degrees.   The fluid resistance measuring method according to claim 1, wherein the cylindrical substrate has a center of gravity on a tip side. The fluid resistance measurement method according to claim 1, wherein the cylindrical base has a density of 1000 to 1200 kg / m ³ .   The fluid resistance measuring method according to claim 1, wherein the cylindrical base has at least one shape selected from a circle, an ellipse, an ellipse, and a flat circle in cross section.   The fluid resistance measurement method according to claim 1, wherein the predetermined drop distance is a specific value within a range of 100 mm or more and 500 mm or less, and the drop time is measured by high-speed shooting with a high-speed camera. . A fluid resistance measuring device for carrying out the fluid resistance measuring method according to any one of claims 1 to 7,
Dough or material can be attached to the outer surface of the cylindrical part, and it has a cylindrical base body and water tank with a density heavier than the density of water, and a high-speed camera.
(A) a unit for dropping the cylindrical base body into standing water in a water tank and measuring a time for the tip of the cylindrical base body to pass a predetermined drop distance; or (B) the cylinder A means for measuring a water entry time from when the cylindrical base end is in contact with the water surface until the rear end is submerged,
An apparatus for measuring fluid resistance, characterized in that it is an evaluation value of fluid resistance on the surface of a cloth or material.

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