JP2017009527A - Flow field measuring method and flow field measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow field measuring method and a flow field measuring system that can visualize a flow field of a place not applied by irradiation light around a model having a configuration with components stacked without using a high refractive index water solution.SOLUTION: A flow field measuring method is provided for forming a flow of water containing tracer particles around a model provided underwater, applying light around a model from a light source, receiving the light returning from the tracer particles by light receiving means, and measuring a flow field. The flow field measuring method is characterized in that a model ship 20 and a model component 30 are formed by using fluorine-based resin for passing through ultra-violet light and/or visible light and having a refraction index to the ultra-violet light and/or the visible light of 1.30 to 1.40, and the model ship 20 with a configuration of stacking the model component 30 of the model ship 20 is used in the irradiation of ultraviolet laser radiation 41 from a laser apparatus 40, and thereby a flow field is measured by applying ultraviolet laser radiation 41 in a sheet form from the laser apparatus 40.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a flow field measurement method and a flow field measurement system using tracer particles.

A technique for measuring a flow field by forming a flow of water containing tracer particles around a model provided in water and tracking the position of the tracer particles is known.
The technique for measuring the flow field is used, for example, for research on energy saving of ships. Regarding energy saving of ships, methods for attaching devices and energy-saving additives around the hull and propeller have been devised, and various principles and methods have been devised as energy-saving additives for ships. Many are aimed at reducing resistance and improving propulsion efficiency. In order to confirm the energy-saving principle and effect of actual energy-saving adjuncts and to aim for higher efficiency, it is necessary to know in detail the changes in flow due to the adjuncts, so flow field measurements using model ships are performed. Yes. The analysis of the stern complex flow by the experimental approach shows that the reliability has been greatly improved by non-contact detailed flow field measurement using a laser Doppler velocimeter (LDV). LDV measurement is still difficult. An example of a place where the laser beam does not reach is the inside of a duct that is one of the hull appendages for the purpose of saving energy.
In order to measure the flow field where the laser beam does not reach, it is conceivable to use a refractive index matching technique that matches the refractive index of the working fluid with the model made of a highly transparent material. By using the refractive index matching technique, it is possible to visualize the movement of the tracer particles used for optical measurement such as LDV and PIV (Particle Image Velocity) through a model in which the refractive index is matched.

Here, Patent Document 1 discloses a visualization measurement or optical measurement made of a fluorinated copolymer having a refractive index of 1.30 to 1.40 and a light transmittance in the wavelength range of 250 to 700 nm of 80% or more. A molded product is disclosed.
In Table 2 of Patent Document 2, the light transmittance at 300 nm is 81 to 88%, the light transmittance at 600 nm is 91 to 94%, and the refractive index is 1.33 to 1.35. Coalescence is disclosed.
Patent Document 3 discloses that a flow path model is formed with a transparent member, and a liquid having a refractive index substantially the same as the refractive index of a transparent member (for example, glass or plastic) (for example, an iodine containing phenolphthalein). A flow test apparatus for observing the flow of a liquid in a flow path by flowing sodium chloride into a model is disclosed.
Further, in Patent Document 4, in order to visualize and measure the flow of fluid inside an object without causing a so-called blur, a transparent model is placed in the liquid, and the liquid that flows inside the transparent model and the liquid that fills the outside And adjusting the refractive index of the model material (for example, silicon rubber) and the liquid (for example, glycerin aqueous solution), and determining this matching by using a laser device and an irradiation light analyzing device. A three-dimensional flow field visualization device is disclosed.

JP 2007-302708 A JP 2004-217728 A JP-A-61-148340 JP-A-2005-300515

Until now, flow field measurement using refractive index matching technology brings the refractive index of a working fluid (sodium iodide aqueous solution) closer to the refractive index of a general transparent material (such as acrylic) as described in Patent Document 3 or 4. Measurement has been carried out. Tables 1 and 2 show the refractive index of the transparent material and working fluid summarized by Budwig (Budwig, R., 1994, Refractive index matching methods for liquid flow investigations, Experiments in Fluids, Vol. 17, 1994).
Table 1 shows the refractive index of the transparent material, and Table 2 shows the refractive index of the working fluid.

However, if a chemical for adjusting the refractive index is added to water, the density, viscosity, and the like change, which makes it difficult to analyze the measurement results. Further, since a high refractive index aqueous solution such as a sodium iodide aqueous solution used for refractive index matching is toxic, it is necessary to ensure safety. In addition, when the high refractive index aqueous solution is left for 1 to several days, it is colored pale yellow, so that a transparent model can be seen. In addition, it is necessary to request a special treatment company for wastewater treatment of the high refractive index aqueous solution. In addition, since the high refractive index aqueous solution is more corroded by metal than water, rust prevention measures are necessary. Moreover, since the electrical characteristics of the high refractive index aqueous solution change, the specification of the contact-type measuring instrument needs to be changed according to the aqueous solution. In addition, it is difficult from the viewpoint of safety and cost to fill a large-scale tank facility such as a towing tank with a highly efficient aqueous solution.
Patent Document 1 and Patent Document 2 disclose a fluorine-containing copolymer having a refractive index close to that of water (1.333) and having a high refractive index, and uses a model such as a model ship. In the conventional flow field measurement by LDV or PIV, there is no disclosure of a technique for measuring the flow field in a portion where light such as a duct or a propeller is superimposed and shadows are blocked when light from a light source is irradiated. .

  Accordingly, the present invention has an object to provide a flow field measurement method and a flow field measurement system that can visualize a flow field in a place where irradiation light does not reach in the vicinity of a model having a structure in which components are superimposed without using a high refractive index aqueous solution. And

The flow field measurement method according to claim 1, wherein a flow of water containing tracer particles is formed around a model provided in water, light is irradiated from the light source to the periphery of the model, and the tracer particles are received by a light receiving means. In the flow field measurement method for measuring the flow field by receiving the light returning from the surface, the model transmits ultraviolet light and / or visible light and has a refractive index of 1.30 to 1.40 for ultraviolet light and / or visible light. The flow field is measured using ultraviolet light or visible light as the light of the light source using the model of the structure that is formed using the fluorine-based material of the above and the model parts are superimposed when the light from the light source is irradiated. Features.
According to the first aspect of the present invention, by forming the model with a material that transmits ultraviolet light and / or visible light, the part that forms the model overlaps, that is, the part blocks the irradiation light. Even in a part that becomes a wall, it is possible to measure the flow field on the back side of the part. Also, instead of adjusting the refractive index of the working fluid in accordance with the refractive index of the model material, water is used as the working fluid, and the model is formed with a transparent material that matches the refractive index of the water (1.333). Therefore, problems such as changes in density and viscosity due to the addition of chemicals for refractive index adjustment to water, toxic problems of sodium iodide aqueous solution used for refractive index matching, and working fluids that have been adjusted for refractive index The problem of safety and cost can be solved by filling a large tank facility such as a towing tank and experiment. Note that as the fluorine-based material, a fluorine-based resin, a fluorine-based rubber, or the like can be used.

The present invention according to claim 2 is characterized in that the flow field is measured by moving the light source and the light receiving means with respect to a plurality of parts of the model.
According to the second aspect of the present invention, it is possible to measure flow fields around a plurality of parts without readjusting the light source and the optical system.

The present invention according to claim 3 is characterized in that the light source irradiates ultraviolet laser light or visible laser light in a sheet form.
According to the third aspect of the present invention, the movement of the tracer particles can be easily grasped, and the flow field measurement can be performed with higher accuracy.

According to a fourth aspect of the present invention, a spectroscopic camera that receives light returning from the tracer particles is used as the light receiving means.
According to the fourth aspect of the present invention, a spectral image of an imaging target can be obtained.

The present invention according to claim 5 is characterized in that a true flow direction is estimated using a multi-time tracking method in measuring a flow field.
According to the fifth aspect of the present invention, the true flow direction of the flow field can be estimated by tracking the tracer particle trajectory over multiple times.

The present invention according to claim 6 is characterized in that the difference in refractive index between water and the model is adjusted by changing the temperature of water and / or adding an additive to water.
According to the sixth aspect of the present invention, when there is a difference in the refractive index between water and the transparent model, the difference is adjusted, so that a part during which the parts constituting the model overlap, that is, the part is irradiated with light. Even if it is a part that becomes a wall that blocks the flow, it is possible to accurately measure the flow field on the back side of the part.

The present invention according to claim 7 is characterized in that sucrose is used as an additive.
According to the seventh aspect of the present invention, it is possible to adjust the difference in refractive index between water and the transparent model using sucrose which is safe and easy to manage and drain.

The present invention according to claim 8 is characterized in that the model is obtained by further removing residual stress from a molded fluorine-based material.
According to the present invention described in claim 8, by removing the residual stress, it is possible to eliminate the influence of the difference in refractive index caused by the residual strain.

The present invention according to claim 9 is characterized in that the process for removing the residual stress is performed by heating and cooling while applying vibration to the model during molding.
According to this invention of Claim 9, a residual stress can be reduced.

In the flow field measurement system corresponding to claim 10, a water tank, a model provided in the water tank, a water flow forming means for forming a flow of water containing tracer particles around the model, and light irradiation to the periphery of the model And a light receiving means for receiving the light returning from the tracer particles, and the model transmits ultraviolet light and / or visible light and has a refractive index of 1.30 to 1 for ultraviolet light and / or visible light. It is formed using 40 fluorine-based materials, and is configured under the condition that model parts overlap when light is emitted from the light source means, and the flow field is measured by irradiating ultraviolet light or visible light as light from the light source means. It is characterized by doing.
According to the tenth aspect of the present invention, by forming the model with a material that transmits ultraviolet light and / or visible light, the part constituting the model is overlapped, that is, the part blocks the irradiation light. Even in a part that becomes a wall, it is possible to measure the flow field on the back side of the part. Also, instead of adjusting the refractive index of the working fluid in accordance with the refractive index of the model material, water is used as the working fluid, and the model is formed with a transparent material that matches the refractive index of the water (1.333). Therefore, problems such as changes in density and viscosity due to the addition of chemicals for refractive index adjustment to water, toxic problems of sodium iodide aqueous solution used for refractive index matching, and working fluids that have been adjusted for refractive index There is no problem of safety and cost by experimenting with large tank facilities such as towing tanks.

The eleventh aspect of the present invention is characterized by comprising a moving means for moving the light source means and the light receiving means as a set with respect to a plurality of parts of the model.
According to the eleventh aspect of the present invention, it is possible to measure flow fields around a plurality of regions without readjusting the light source and the optical system.

The light source means uses ultraviolet laser light or visible laser light as ultraviolet light or visible light, and irradiates the ultraviolet laser light or visible laser light in a sheet form.
According to the present invention of the twelfth aspect, the movement of the tracer particles can be easily grasped, and the flow field measurement can be performed with higher accuracy.

The invention according to claim 13 is characterized in that a spectroscopic camera for receiving light returning from the tracer particles is used as the light receiving means.
According to the thirteenth aspect of the present invention, a spectral image of an imaging target can be obtained.

The present invention according to claim 14 further includes a flow field analyzing means for analyzing the light reception data obtained by the light receiving means using a multi-time tracking method, and estimating the true flow direction.
According to the present invention as set forth in claim 14, the true flow direction of the flow field can be estimated by tracking the tracer particle trajectory over multiple times.

The present invention according to claim 15 is characterized in that the water tank is a towing tank or a circulating water tank.
According to this invention of Claim 15, a model can be provided in a towing tank or a circulating water tank, and flow field measurement can be performed.

  According to the flow field measurement method of the present invention, a model is formed of a material that transmits ultraviolet light and / or visible light, so that a part during which parts constituting the model overlap, that is, a wall that blocks the irradiation light. Even in such a part, the flow field measurement on the back side of the part can be performed. Also, instead of adjusting the refractive index of the working fluid in accordance with the refractive index of the model material, water is used as the working fluid, and the model is formed with a transparent material that matches the refractive index of the water (1.333). Therefore, problems such as changes in density and viscosity due to the addition of chemicals for refractive index adjustment to water, toxic problems of sodium iodide aqueous solution used for refractive index matching, and working fluids that have been adjusted for refractive index The problem of safety and cost can be solved by filling a large tank facility such as a towing tank and experiment.

  In addition, when measuring the flow field by moving the light source and light receiving means with respect to multiple parts of the model, measure the flow field around the multiple parts without re-adjusting the light source or optical system. Can do.

  Further, when the light source irradiates ultraviolet laser light or visible laser light in the form of a sheet, it becomes easy to capture the movement of the tracer particles, and the flow field measurement can be performed with higher accuracy.

  Further, when a spectroscopic camera that receives light returning from the tracer particles is used as the light receiving means, a spectroscopic image to be imaged can be obtained.

  Also, when estimating the true flow direction using the multi-time tracking method when measuring the flow field, the true flow direction of the flow field is estimated by tracking the tracer particle trajectory over multiple times. be able to.

  In addition, by adjusting the difference in refractive index between water and the model by changing the temperature of the water and / or adding additives to the water, the part between the parts that make up the model overlaps, that is, the part is irradiated with light. Even if it is a part that becomes a wall that blocks the flow, it is possible to accurately measure the flow field on the back side of the part.

  Moreover, when using sucrose as an additive, the difference in refractive index between water and the transparent model can be adjusted by using an additive that is highly safe and easy to manage and drain.

  Further, in the case where the residual stress is further removed from a model obtained by molding a fluorine-based material, the effect of causing a difference in refractive index due to residual strain can be eliminated.

  In addition, when the residual stress is removed by heating and cooling while applying vibration to the model during molding, the residual stress can be reduced.

  Further, according to the flow field measurement system of the present invention, by forming a model with a material that transmits ultraviolet light and / or visible light, a part during which the parts constituting the model overlap, that is, the part emits irradiation light. Even in a part that becomes a blocking wall, it is possible to measure the flow field on the back side of the part. Also, instead of adjusting the refractive index of the working fluid in accordance with the refractive index of the model material, water is used as the working fluid, and the model is formed with a transparent material that matches the refractive index of the water (1.333). Therefore, problems such as changes in density and viscosity due to the addition of chemicals for refractive index adjustment to water, toxic problems of sodium iodide aqueous solution used for refractive index matching, and working fluids that have been adjusted for refractive index There is no problem of safety and cost by experimenting with large tank facilities such as towing tanks.

  In addition, when a moving means that moves the light source means and the light receiving means as a set to a plurality of parts of the model is provided, the flow field around the plurality of parts is measured without readjustment of the light source and the optical system. can do.

  In addition, the light source means uses ultraviolet laser light or visible laser light as ultraviolet light or visible light, and when irradiating the ultraviolet laser light or visible laser light in the form of a sheet, it becomes easier to capture the movement of the tracer particles, and more accurate. The flow field can be measured well.

  Further, when a spectroscopic camera that receives light returning from the tracer particles is used as the light receiving means, a spectroscopic image to be imaged can be obtained.

  The apparatus further comprises a flow field analyzing means for analyzing the light reception data obtained by the light receiving means by using a multi-time tracking method, and when tracing the true flow direction, traces the tracer particle trajectory over multiple times. Thus, the true flow direction of the flow field can be estimated.

  Moreover, when a water tank is a towing water tank or a circulating water tank, a model can be provided in a towing water tank or a circulating water tank, and flow field measurement can be performed.

1 is a schematic configuration diagram showing a basic configuration of a flow field measurement system according to an embodiment of the present invention. Illustration of flow field measurement range of the same flow field measurement system The figure which shows a state of observing a lattice through a tube Explanatory drawing of the flow field measurement range in the flow field measurement system by other embodiment of this invention Illustration of flow field measurement range in a conventional flow field measurement system Illustration of flow field measurement range in a conventional flow field measurement system

  Hereinafter, a flow field measurement method and a flow field measurement system according to an embodiment of the present invention will be described.

FIG. 1 is a schematic configuration diagram showing a basic configuration of a flow field measurement system according to an embodiment of the present invention.
FIG. 1 is a view of a model ship 20 provided in a water tank 10 filled with water as viewed from below, and a ship bottom 21 is visible. A model propeller 31 and a model rudder 32 are provided on the stern side of the model ship 20. Further, a model duct 33 that is one of energy-saving addenda is attached at a position close to the front of the model propeller 31. The model propeller 31, the model rudder 32, and the model duct 33 (hereinafter, these three parts are collectively referred to as “model part 30”) are provided in water.
The water tank 10 is a towed water tank, and the model ship 20 moves in the water tank by towing means (not shown).

In order to measure the flow field around the model component 30, water flow forming means (not shown) is provided around the model component 30 to form a flow of water containing tracer particles. From the point of forming the water flow, the towing means also constitutes a part of the water flow forming means. On one side of the stern side of the model ship 20, a laser device 40 that is a light source means for irradiating ultraviolet light is disposed, and behind the model ship 20 is tracer particles that have received light irradiated from the laser device 40. A plurality of spectroscopic cameras 50 as light receiving means for receiving the returning light are arranged.
The laser device 40 uses ultraviolet laser light 41 as ultraviolet light, and the ultraviolet laser light 41 is irradiated around the model component 30 in a sheet shape. FIG. 1 shows a state in which the ultraviolet laser light 41 is irradiated toward the side surface of the model duct 33 so as to take a cross section of the model duct 33. By irradiating the ultraviolet laser beam 41 in the form of a sheet, it becomes easy to capture the movement of the tracer particles, and the flow field measurement can be performed with higher accuracy.
The spectroscopic camera 50 is a visible light camera. By arranging a plurality of spectroscopic cameras 50 at different positions, it is possible to measure a flow field three-dimensionally. Note that when the flow field measurement is performed two-dimensionally, one spectroscopic camera 50 may be provided.

A fluorescent substance such as rhodamine B is used for the tracer particles. Tracer particles excited by the sheet-like ultraviolet laser light 41 emitted from the laser device 40 emit visible light fluorescence. Thus, by obtaining visible light emission by ultraviolet excitation, the wavelength of light is varied to facilitate tracing of tracer particles. The ultraviolet laser light may be continuous light or pulsed light. In addition, the excitation laser beam may be visible light, and various tracer particles used for water can be used as the tracer particles.
The spectroscopic camera 50 receives the visible light of the tracer particles. By using the spectroscopic camera 50, a spectroscopic image of a flow field that is an imaging target can be obtained. Instead of the spectroscopic camera 50, a combination of general imaging means and an optical filter may be used.

  The laser device (light source means) 40 and the camera 50 (light receiving means) are set as a set with respect to a plurality of parts (the model propeller 31, the model rudder 32, and the model duct 33) of the model component 30 while maintaining the mutual positional relationship. In order to be able to move, they are unitized by being arranged on a common platform that can move in the front-rear direction or the width direction of the ship 20. By moving the laser device (light source means) 40 and the optical system leading to the camera 50 (light receiving means) as a set, a plurality of parts (a model propeller 31, a model rudder 32, and a model can be obtained without readjustment of the optical system. The flow field around the duct 33) can be measured.

The laser device 40 and the plurality of spectroscopic cameras 50 are connected to a personal computer 60 that is a flow field analysis means. By analyzing the received light data obtained by the spectroscopic camera 50 with a flow field analysis means (personal computer) 60, it is possible to know a change in flow due to the provision of the model duct 33 which is one of the energy-saving additive.
The flow field analysis means 60 analyzes the received light data obtained by the spectroscopic camera 50 using a multi-time tracking method. That is, the position of the tracer particle is tracked over a continuous time at a predetermined time interval. In addition, since the position of the tracer particle may be false at 2 hours, it is possible to track the position of the tracer particle for 3 or 4 hours and to obtain a correct locus by eliminating the false position of the tracer particle. preferable. This makes it possible to estimate the true flow direction of the flow field. For the flow field analysis, a method of comparing images at different times (pattern matching) or a method of tracking the positions of individual tracer particles (tracking) can be used.

FIG. 2 is an explanatory diagram of a flow field measurement range in the flow field measurement system according to the present embodiment, and FIG. 5 is an explanatory diagram of a flow field measurement range in the conventional flow field measurement system. 2A and 5A are views of the model ship as viewed from the other side, and FIGS. 2B and 5D are views of the model ship as viewed from the rear. . 2 and 5, the laser device 40 is disposed on the other side of the stern side of the model ship.
In FIG. 5, the model propeller 331, the model rudder 332, and the model duct 333 of the model ship 320 are made of an opaque material. The laser device 40 moves in the front-rear direction of the model ship 320 while maintaining the positional relationship with the camera 50, and emits the ultraviolet laser light 41 so as to take the cross sections of the model propeller 331, model rudder 332, and model duct 333. Irradiate. For example, first, the ultraviolet laser light 41 is irradiated toward the model duct 333, then moved rearward and irradiated with the ultraviolet laser light 41 toward the model propeller 331, and then moved rearward to the model rudder 332. Irradiate the ultraviolet laser beam 41 toward.
However, since the model propeller 331 and the model duct 333 are overlapped when the ultraviolet laser light 41 is irradiated from the laser device 40, the ultraviolet laser light 41 is blocked, and the propeller surface of the model propeller 331 and the model duct 333 are overlapped. The flow field inside can not be measured. That is, the model propeller 331 has a configuration in which a plurality of blades of the model propeller 331 may overlap when viewed from the laser device 40 side. The model duct 333 has a front side and a back side of the model duct 333. It is the structure which the stern tube intervening in the side and also overlaps. Since the model propeller 331 and the model duct 333 are made of an opaque material (a material that does not transmit laser light), the flow field in the part where these parts overlap is a wall that blocks the ultraviolet laser light 41. The flow field on the back side of the part cannot be measured even if it is observed from the opposite side of 180 degrees. In addition, when these parts are formed using a general transparent material as shown in Table 1, the ultraviolet laser beam 41 is transmitted, but the difference between the refractive index of the part and the refractive index of water is large. The position is distorted and accurate observation is not possible. Accordingly, the flow field in the portion where the components constituting the model propeller 331 and the model duct 333 overlap is different from the refractive index of water, so that the light does not travel straight and accurate flow field measurement cannot be performed.
Further, the flow field on the back side of the model rudder 332 cannot be measured unless observation is performed from the opposite side of 180 degrees. Therefore, it is necessary to move the laser device 40 to the other side of the model ship 320.

On the other hand, in FIG. 2, the laser device 40 moves in the front-rear direction of the model ship 20 while maintaining the positional relationship with the camera 50, and takes the respective cross sections of the model propeller 31, model rudder 32, and model duct 33. The model propeller 31 and the model duct 33 are configured to overlap with each other when irradiating the ultraviolet laser light 41 and irradiating the ultraviolet laser light 41 from the laser device 40. The model rudder 32 and the model duct 33 are different from the model ship 320 in that they transmit ultraviolet light and are formed using a fluorine-based resin having a refractive index with respect to ultraviolet light of 1.30 to 1.40. . Note that a fluorine-based resin having a refractive index equal to the refractive index of water 1.333 is preferably used. In some cases, a fluorine-based rubber having a refractive index of 1.30 to 1.40 may be used.
Thus, when the model component 30 is formed of a transparent material having a refractive index that matches the refractive index of water, the model component 30 can be made invisible underwater. 41 goes straight without being refracted at the boundary between water and the model part 30, and is not obstructed by the model part 30, so that the back side of the model part 30 can be visualized without causing any deviation. Therefore, it is possible to measure the flow field at the propeller surface of the model propeller 31, around the rudder of the model rudder 32 (including the back side), and inside the model duct 33, that is, between the overlapping parts.
In the model component 30 shown in FIG. 2, the model propeller 31 and the model duct 33 correspond to the configuration in which the components of the model component 30 overlap when the ultraviolet laser beam 41 is irradiated from the laser device 40. That is, the model propeller 31 has a configuration in which a plurality of blades of the model propeller 31 may overlap when viewed from the laser device 40 side. The model duct 33 has a front side and a back side of the model duct 33. In addition, the stern tubes interposed therebetween overlap each other. As described above, conventionally, it has been difficult to measure the flow field in the portion during which the components constituting the model component 30 are overlapped because light is blocked or the refractive index is different.
Also, instead of adjusting the refractive index of the working fluid such as sodium iodide aqueous solution according to the refractive index of the transparent model, water is used as the working fluid and a transparent material that matches the refractive index of the water is selected. The problem of changes in density, viscosity, etc. due to the addition of chemicals for refractive index adjustment, the toxicity problem of sodium iodide aqueous solution used for refractive index matching, and the working fluid with adjusted refractive index The problem of safety and cost can be solved by filling a large tank facility such as

As a fluorine-type resin used as the material of the model component 30, for example, those shown in Table 3 can be used. These fluorine-based resins are thermoplastic resins or UV curable resins having a refractive index much lower than that of general transparent materials shown in Table 1. The refractive index is a measured value with visible light.

In addition, it is preferable that the model component 30 is the thing which further processed the removal of a residual stress from what shape | molded the fluorine-type resin. By removing the residual stress, it is possible to eliminate the influence of the difference in refractive index caused by the residual strain.
For example, the residual stress is removed by heating and cooling while applying vibration to the model component 30 during molding with a fluorine-based resin. Here, the time of molding includes when resin is injected and molded in a resin molding machine (compression molding machine or injection molding machine), or until the molded product cools down to room temperature, and as a part in a cut product The period until the inspection is taken. Residual stress can be reduced by heating and cooling while applying vibration to the model component 30 during molding.

Moreover, when there is a slight difference in the refractive index of the water in the model part 30 formed and the water tank 10, it adjusts by changing the temperature of water and / or adding the additive to water. In this way, by matching the refractive indexes of water and the model component 30 with temperature and / or additives, the flow field of the portion that is normally invisible such as the propeller surface of the model propeller 31 and the inside of the model duct 33 is measured. Can do.
The refractive index of water decreases with increasing water temperature and increases with decreasing water temperature. However, since the amount of change in the refractive index of water due to the rise and fall of the water temperature is small, an additive is added to the water instead of or together with the rise and fall of the water temperature. Sucrose can be used as an additive to water. Table 4 is a diagram showing the relationship between Brix (%) and refractive index (nD20 ° C., D-line = 589 nm) (Source: ICUMSA (International Sugar Unified Analysis Committee)).

  Here, as an example, FIG. 3 shows a state in which the lattice is observed through a tube of the product name THV of 3M Japan Co., Ltd. in Table 3. The refractive index of a flat plate having a thickness of 2 mm was measured in advance, and the refractive index when the thickness was increased was investigated. The refractive index of the 2 mm-thick flat plate was slightly large as nD = 1.362. The working fluid was adjusted for refractive index matching by the concentration of sugar water. The water temperature is adjusted to 20 ° C. 3A shows a sugar water concentration (Brix) of 0% [refractive index nD = 1.333], and FIG. 3B shows a sugar water concentration (Brix) of 20% [refractive index nD = 1.364]. FIG. 3C shows a sugar water concentration (Brix) of 24.2% [nD = 1.371]. In FIGS. 3A and 3C, since the refractive index is not matched, the grating appears to be distorted. In the case of FIG. 3B, the distortion was completely eliminated. Originally, the refractive index should be the same at a sugar water concentration (Brix) of 19% [nD = 1.362]. This is probably because edible sugar was used instead of sucrose. In addition, although it is possible to use a salt as an additive to water, since there is a concern about corrosion of a water tank or other equipment, it is preferable to use sucrose which is not toxic even if added to water.

In the above embodiment, the light source means is the laser device 40 that irradiates the ultraviolet laser light 41, the tracer particles are fluorescent materials, and the light receiving means emits light returning from the tracer particles that are excited by the ultraviolet laser light 41 and emit visible light. Although described as the spectroscopic camera 50 for receiving visible light, the light source means is also a laser device 40 that irradiates the ultraviolet laser light 41, and the tracer particle is a substance that reflects and / or scatters ultraviolet light, The light receiving means may be a spectroscopic camera for ultraviolet light that receives reflected light and / or scattered light from tracer particles exposed to ultraviolet laser light 41.
In the above embodiment, since ultraviolet light is easier to match the refractive index of water and the transparent model than visible light, ultraviolet light is used as light source light, but the light source means irradiates visible laser light. In the laser device, the tracer particles may be a fluorescent material or a material that reflects and / or scatters visible light, and the light receiving means may be a visible light spectroscopic camera 50 that receives light returning from the tracer particles. In this case, the model component 30 is formed using a fluorine-based resin or rubber that transmits visible light and has a refractive index with respect to visible light of 1.30 to 1.40.

  Further, the water tank 10 may be a circulating water tank instead of a towing tank. The circulating water tank has a flow in the water of the water tank, and the position of the model ship 20 is fixed. The size of the circulating water tank is smaller than that of the towed water tank. Therefore, when the water tank 10 is a circulating water tank, the amount of additives (sucrose, etc.) to the water can be reduced.

  Further, when measuring a plurality of parts, the laser device 40 is not moved, but the wavelength of the laser light irradiated for each measurement part or the substance suspended in the tracer particles is changed, and the measurement is performed from the laser device 40 at a predetermined position. A method of simultaneously irradiating a plurality of laser beams toward a plurality of target portions may be employed.

Next, a flow field measurement method and a flow field measurement system according to another embodiment of the present invention will be described with reference to FIGS. FIG. 4 is an explanatory diagram of a flow field measurement range in the flow field measurement system according to the present embodiment, and FIG. 6 is an explanatory diagram of a flow field measurement range in the conventional flow field measurement system. 4 and 6 are views of the model ship as viewed from the rear. Note that members having the same functions as those in the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.
In FIG. 6, the model ship 420 has two model skegs, one model skeg 421a and the other model skeg 421b at the stern. One model skeg 421a includes one outer model duct 422ao and one inner model duct. 422ai, and the other model skeg 421b includes the other outer model duct 422bo and the other inner model duct 422bi. One outer model duct 422ao and one inner model duct 422ai have different shapes, and the other outer model duct 422bo and the other inner model duct 422bi have different shapes. One model skeg 421a, the other model skeg 421b, one outer model duct 422ao, one inner model duct 422ai, the other outer model duct 422bo, and the other inner model duct 422bi are formed of an opaque material. The laser device 40 is disposed on one side of the stern side of the model ship 420.
One model skeg 421a, the other model skeg 421b, one outer model duct 422ao, one inner model duct 422ai, the other outer model duct 422bo, and the other inner model during irradiation of the ultraviolet laser beam 41 from the laser device 40 Since the ducts 422bi overlap each other, in this case, one model skeg 421a, the other model skeg 421b, one outer model duct 422ao, one inner model duct 422ai, the other outer model duct 422bo, and the other inner side The flow field inside the model duct 422bi cannot be measured.

On the other hand, in FIG. 4, the model ship 120 includes one model skeg 121a, the other model skeg 121b, one outer model duct 122ao, one inner model duct 122ai, the other outer model duct 122bo, and the other inner model duct. 122bi and the laser device 40 is arranged on one side of the stern side of the model ship 120 in the same manner as the model ship 420, but one model skeg 121a, one outer model duct 122ao, and one Is different from the model ship 420 in that the inner model duct 122ai is made of a fluorine-based resin that transmits ultraviolet light and has a refractive index with respect to ultraviolet light of 1.30 to 1.40.
In this way, one model skeg 121a, one outer model duct 122ao, and one inner model duct 122ai are formed of a material having a refractive index that is transparent and matches the refractive index of water. The laser beam 41 is not blocked by one model skeg 121a, one outer model duct 122ao, and one inner model duct 122ai. Therefore, it is possible to measure the flow field in the part of one model skeg 121a, one outer model duct 122ao, and one inner model duct 122ai, that is, between overlapping parts.
One model skeg 121a may be entirely formed of a fluorine-based resin, or may be formed only on the surface using a fluorine-based resin and filled with water.

  In addition, although illustration is abbreviate | omitted, also when a model fin is attached as one of the energy-saving additions, while passing the model light through the ultraviolet light, the refractive index with respect to the ultraviolet light is 1.30 to 1.40. By using this resin, the flow field around the fins (hull, rudder, boss cap) can be measured.

  The flow field measurement method and the flow field measurement system of the present invention provide a propeller / rudder / attachment itself that becomes a wall and is difficult to visualize, that is, a propeller rotating around the inside of the duct, around the rudder, and rotating. In-plane, other duct propeller propeller surface, around the fins attached to the hull, boss cap, rudder, etc. because ultraviolet light or visible light arrives without changing the light source arrangement, the visualization range of flow field measurement by PIV or LDV Can be enlarged. In addition, it can be applied to many applications in which a flow field is measured using a model in which parts are superimposed in water as well as in a ship.

DESCRIPTION OF SYMBOLS 10 Water tank 20 Model ship 30 Model parts 31 Model propeller 32 Model rudder 33 Model duct 40 Laser apparatus (light source means)
41 Ultraviolet laser beam 50 Spectroscopic camera (light receiving means)
60 Personal computer (flow field analysis means)

Claims (15)

  A flow of water containing tracer particles is formed around a model provided in water, light is irradiated to the periphery of the model from a light source, and light returning from the tracer particles is received by a light receiving means to measure a flow field. In the flow field measurement method, the model is formed using a fluorine-based material that transmits ultraviolet light and / or visible light and has a refractive index of 1.30 to 1.40 with respect to the ultraviolet light and / or visible light. And using the model having a configuration in which parts of the model overlap when the light from the light source is irradiated, and measuring the flow field using the ultraviolet light or the visible light as the light of the light source. Flow field measurement method.   The flow field measuring method according to claim 1, wherein the flow field is measured by moving the light source and the light receiving unit with respect to a plurality of parts of the model.   The flow field measuring method according to claim 1, wherein the light source irradiates ultraviolet laser light or visible laser light in a sheet shape.   The flow field measurement method according to claim 1, wherein a spectroscopic camera that receives light returning from the tracer particles is used as the light receiving unit.   5. The flow field measurement method according to claim 1, wherein in the measurement of the flow field, a true flow direction is estimated using a multi-time tracking method.   The difference in refractive index between the water and the model is adjusted by changing the temperature of the water and / or adding an additive to the water. The described flow field measurement method.   The flow field measuring method according to claim 6, wherein sucrose is used as the additive.   8. The flow field measurement method according to claim 1, wherein the model is a molded product of the fluorine-based material and further processed to remove residual stress. 9. .   9. The flow field measuring method according to claim 8, wherein the treatment for removing the residual stress is performed by heating and cooling while applying vibration to the model during molding.   A water tank, a model provided in the water tank, water flow forming means for forming a flow of water containing tracer particles around the model, light source means for irradiating light around the model, and light returning from the tracer particles Light receiving means for receiving the light, and the model transmits a fluorine-based material that transmits ultraviolet light and / or visible light and has a refractive index of 1.30 to 1.40 with respect to the ultraviolet light and / or visible light. The model part is configured to overlap when the light from the light source means is irradiated, and the flow field is measured by irradiating the ultraviolet light or the visible light as the light of the light source means. A flow field measurement system characterized by   The flow field measurement system according to claim 10, further comprising a moving unit that moves the light source unit and the light receiving unit as a set with respect to a plurality of parts of the model.   12. The light source means uses ultraviolet laser light or visible laser light as the ultraviolet light or the visible light, and irradiates the ultraviolet laser light or the visible laser light in a sheet shape. Flow field measurement system described in 1.   The flow field measurement system according to claim 10, wherein a spectroscopic camera that receives light returning from the tracer particles is used as the light receiving unit.   14. The flow field analyzing means for analyzing the light reception data obtained by the light receiving means using a multi-time tracking method is further provided, and the true flow direction is estimated. The flow field measurement system according to item 1. The flow field measurement system according to claim 10, wherein the water tank is a towing water tank or a circulating water tank.