JP2013079878A - Method and apparatus for measuring fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus that enable simultaneous measurement of a pressure field using a pressure-sensitive paint and a velocity field using visible particles without damaging the accuracy of each measurement and that obtain information on the pressure field and the velocity field, which are correlated with each other in a time direction at a plurality of time points regarding a same event, in order to clarify the causal relation.SOLUTION: The method simultaneously performs a pressure field measuring step where pressure distribution on an object surface in contact with a fluid is optically measured using the pressure-sensitive paint, and a velocity field measuring step where a fluid behavior in space is optically measured using the visible particles scattered in the fluid, and obtains information on the pressure field and the velocity field regarding the same event as correlated information in a time direction.

Description

  The present invention relates to a method and apparatus for measuring dynamic characteristics of a fluid, and more particularly to a fluid measurement method and apparatus suitable for land transport aircraft such as automobiles and railways and wind tunnel experiments in the aerospace field.

Conventionally, to measure the dynamic characteristics of a fluid, it is possible to measure the pressure field caused by the fluid by measuring the pressure distribution on the surface of the object in contact with the fluid, and to observe the emitted or scattered light optically in the fluid It is known that a small particle (visible particle) is dispersed and visualized to measure spatial behavior such as flow velocity and flow direction.
For example, with regard to pressure field measurement, unsteady pressure field measurement in airflow using pressure-sensitive paint (Pressure-Sensitive paint: PSP) whose emission intensity changes with changes in oxygen concentration according to the pressure of the fluid It is attracting attention in land transport aircraft such as railroads and wind tunnel experiments in the aerospace field.
This measurement technique utilizes a phenomenon in which the emission intensity of the dye contained in the pressure-sensitive paint is quenched by oxygen.
By combining a high-speed response type pressure-sensitive paint, a high-speed camera, and a high-intensity laser light source, it has become possible to measure an unsteady pressure field at a sampling rate of several kHz (see, for example, Patent Document 1). .

In addition, regarding the measurement of spatial behavior, it is possible to measure a time-series spatial flow velocity field at a sampling rate of several tens of kHz by a time-series particle image velocity measurement method (Time-Resolved Particle Image Velocimetry) or the like.
This measurement technique is a method for obtaining the airflow velocity by visualizing particles dispersed in the airflow with a laser and a camera and calculating the moving velocity from an image.
This method is also attracting attention in land transport aircraft such as automobiles and railways and in wind tunnel experiments in the aerospace field.

JP 2004-28650 A

However, the known dynamic characteristics measurement techniques of fluids as described above can be precisely measured individually, but when measuring both the pressure field and the velocity field, the pressure field is reduced by pressure-sensitive paint. The pressure field and velocity field were each measured in separate tests, such as measuring and then measuring the velocity field by particle image velocimetry.
In other words, each measurement needs to be performed in an optimized environment and a unique measuring apparatus, and it is difficult to simultaneously perform the same event.
Specifically, the particles used in the velocity field measurement are roughly divided into alcohol particles, oil droplet particles, and solid particles such as alumina and titanium dioxide. The alcohol particles dissolve the pressure-sensitive paint, and the oil droplet particles. Adheres to the pressure-sensitive paint surface and impedes oxygen permeability, and solid particles adhere to the pressure-sensitive paint due to static electricity, etc., preventing excitation light and luminescence measurement, and physically destroying the pressure-sensitive paint surface. In the presence of particles, the pressure field with a pressure-sensitive paint could not be measured with high accuracy, and each test had to be performed separately.

In addition, the projection light of a light source such as a laser used in the measurement of the velocity field by scattering of visible particles and the scattered light or light emission from the particles and the pressure-sensitive paint used in the measurement of the pressure field by the pressure-sensitive paint are projected. Excitation light and light emission from pressure-sensitive paint may interfere with each other, and accuracy cannot be ensured both in the measurement of the pressure field by pressure-sensitive paint and the velocity field by the dispersion of visible particles. It was a difficult factor.
And in the measurement results of pressure field and velocity field obtained in separate tests, the correlation information of pressure field and velocity field in the time direction cannot be obtained directly without additional information. It was difficult to clarify the causal relationship between the pressure field and the velocity field in the measurement of the dynamic characteristics of the fluid.

  Therefore, the present invention is a phenomenon that fluctuates with time by making it possible to simultaneously measure the pressure field using pressure-sensitive paint and the velocity field using visible particles without losing the accuracy of each measurement. However, an object of the present invention is to provide a fluid measurement method and apparatus that can acquire information on pressure fields and velocity fields correlated in the time direction at a plurality of times in the same event and clarify the causal relationship between them. To do.

  The invention according to claim 1 is a fluid measurement method for measuring a dynamic characteristic of a fluid, a pressure field measurement step for optically measuring a pressure distribution on an object surface in contact with the fluid with a pressure sensitive paint, And a velocity field measuring step for optically measuring the spatial behavior of the fluid by spraying visible particles on the pressure-sensitive paint, and the emission intensity of the pressure-sensitive paint changes according to the change of the oxygen concentration according to the pressure of the fluid. The visible particles are sublimable particles, the pressure field measurement step and the velocity field measurement step are performed simultaneously, and information on the pressure field and the velocity field for the same event is obtained as information correlated in the time direction. The problem is solved.

  The invention according to claim 2 includes, in addition to the configuration of the fluid measurement method according to claim 1, projection light of a light source for particle visualization in the velocity field measurement step, scattered light or light emission from particles, and the pressure field. The object is solved by having an interference eliminating step for eliminating the influence of the respective optical interferences of the projection light of the light source for excitation of the pressure sensitive paint and the light emission of the pressure sensitive paint in the measurement step.

  In addition to the configuration of the fluid measurement method according to claim 2, the invention according to claim 3 solves the above-described problem by performing the interference elimination step using an optical filter.

  In the invention according to claim 4, in addition to the configuration of the fluid measurement method according to claim 2 or claim 3, the interference elimination step is performed by arithmetic processing of the pressure field measurement step and the velocity field measurement step. The above-mentioned problem is solved.

  The invention according to claim 5 is a fluid measuring device for measuring the dynamic characteristics of a fluid, and is provided on the surface of an object in contact with the fluid, and the luminescence intensity changes with the change in oxygen concentration according to the pressure of the fluid. Pressure coating, particle spraying means for spraying visible sublimable particles in a fluid, excitation light source for projecting excitation light onto the pressure sensitive paint, and pressure field measuring means for measuring light emission of the pressure sensitive paint And a visualization light source for projecting light for visualizing the sublimable particles, a velocity field measuring means for measuring scattered light or luminescence from the sublimable particles, and the pressure field measuring means and the velocity field measuring means are identical. The problem is solved by including information acquisition means for acquiring measurement information for an event as information correlated in the time direction.

  In the invention according to claim 6, in addition to the configuration of the fluid measurement device according to claim 5, the pressure field measurement unit does not directly receive the projection light of the visualization light source, and the velocity field measurement unit includes the excitation Each of the velocity field measuring means and the pressure field measuring means is provided so as not to directly receive the projection light of the light source, and each of the velocity field measuring means and the pressure field measuring means includes an optical filter for reducing light other than light to be observed. It is.

According to the fluid measurement method according to claim 1 and the fluid measurement apparatus according to claim 5, the sublimation particles are sensed by simultaneously performing pressure field measurement and velocity field measurement using the visible particles as sublimation particles. When it comes into contact with the pressure paint, it immediately sublimes and becomes a gas, so that the pressure-sensitive paint does not melt, adhere to it, and does not physically break.
This makes it possible to measure the pressure field with pressure-sensitive paint and the velocity field with visible particles at the same time without losing the accuracy of each measurement, and this is a phenomenon that varies with time. However, it is possible to acquire information on pressure fields and velocity fields correlated in the time direction at a plurality of times in the same event, and clarify the causal relationship.

According to the configurations of the second and sixth aspects, by eliminating the influence of optical interference, it is possible to further improve the accuracy of both the pressure field measurement and the velocity field measurement and to perform them simultaneously. Even for a phenomenon that varies with time, it is possible to acquire information on pressure fields and velocity fields correlated in the time direction at a plurality of times in the same event, and further clarify the causal relationship.
According to the configuration of the third and sixth aspects, the optical filter can reduce the processing load of the interference elimination process at the time of measurement, and can accurately eliminate the influence of optical interference.
According to the configuration of the fourth aspect of the present invention, it is possible to eliminate the influence of optical interference in the absence of the optical filter or the optical interference that cannot be completely excluded by the optical filter, by both the pressure field measurement and the velocity field measurement. The accuracy is further improved.

BRIEF DESCRIPTION OF THE DRAWINGS (a) The schematic explanatory drawing seen from the side of the fluid measuring apparatus which is one embodiment of this invention, (b) The schematic explanatory drawing which looked at the rectangular duct part vicinity from upper direction. The schematic diagram of the pseudo shock wave measured in one Example of this invention. Explanatory drawing of the particle spraying nozzle of 1 Example of this invention. 1 is a schematic diagram of a synchronization system according to one embodiment of the present invention. Explanatory drawing of the synchronous timing of the synchronous system of one Example of this invention. Process explanatory drawing of the pressure-sensitive paint measurement calibration of one Example of this invention. The scattered light image of the particle | grains of one Example of this invention. The distribution image of the pressure field measured by one Example of this invention, and the vector image of a velocity field. Comparison diagram of pressure distribution of unsteady pressure sensor and pressure sensitive paint measurement.

  The fluid measurement method of the present invention is a fluid measurement method for measuring the dynamic characteristics of a fluid, a pressure field measurement step for optically measuring the pressure distribution on the surface of an object in contact with the fluid with a pressure sensitive paint, And a velocity field measuring step for optically measuring the spatial behavior of the fluid by spraying visible particles, and the emission intensity of the pressure-sensitive paint is changed by changing the oxygen concentration according to the pressure of the fluid. The visible particle is a sublimable particle, the pressure field measurement step and the velocity field measurement step are simultaneously performed, and information on the pressure field and the velocity field for the same event is acquired as information correlated in the time direction. It is possible to measure the pressure field with pressure-sensitive paint and the velocity field with visible particles at the same time without impairing the accuracy of each measurement. Multiple times in The acquired information of time pressure field and velocity field having a correlation with the direction, as long as it enables to clarify the causal relationship, specific embodiments thereof may be any one.

  The fluid measuring device of the present invention is a fluid measuring device that measures the dynamic characteristics of a fluid, and is provided on the surface of an object in contact with the fluid. A coating material; particle spraying means for spraying visible sublimable particles in the fluid; an excitation light source for projecting light for excitation onto the pressure sensitive paint; and a pressure field measuring means for measuring light emission of the pressure sensitive paint. A visualizing light source that projects light for visualizing the sublimable particles, a velocity field measuring unit that measures scattered light or luminescence from the sublimable particles, and the same event of the pressure field measuring unit and the velocity field measuring unit Information acquisition means for acquiring measurement information on the time as a correlated information in the time direction, and measuring the pressure field with pressure-sensitive paint and the velocity field with visible particles, Not to lose It is possible to perform simultaneously, even if the phenomenon fluctuates in time, to acquire information on pressure and velocity fields correlated in the time direction of multiple times in the same event, and to clarify the causal relationship As long as it is possible, the specific embodiment may be any.

An embodiment of a fluid measuring method and a fluid measuring device according to the present invention will be described.
As schematically shown in FIG. 1, the fluid measuring device 100 has a suction means 102 connected to one end of a rectangular duct 101 via a valve 103 and an air flow via a particle supply container 108 to the other end. The formation nozzle 104 is connected to form a wind tunnel that forms a pressure field and a velocity field of the fluid to be measured in the rectangular duct 101.
A gas as a fluid to be measured is supplied from the gas supply means 105 to the air flow forming nozzle 104, and a particle distribution nozzle 107 is provided in the particle supply container 108 provided upstream of the air flow forming nozzle 104 and passes therethrough. The gas is sprayed with sublimable particles 131 for optically measuring the velocity field. The sublimable particles 131 to be dispersed are supplied from the particle supply tank 106.

In the rectangular duct 101, at least two adjacent surfaces are formed of a transparent material such as acrylic resin, and a pressure-sensitive paint 111 is applied to the inner surface side of the surface where at least the opposing surface and the adjacent surface are transparent.
Around the outside of the rectangular duct 101, an excitation light source 113 that projects excitation light into the rectangular duct 101 on the pressure-sensitive paint 111, a high-speed camera 112 that is a pressure field measuring unit that measures light emission of the pressure-sensitive paint 111, A visualization light source 121 that projects light for visualizing the sublimable particles 131 into the rectangular duct 101, and a high-speed camera 122 that is a velocity field measuring unit that measures scattered light or light emission from the sublimable particles 131 are arranged. .
As shown in FIG. 1B, the excitation light source 113, the high-speed camera 112 that is the pressure field measuring means, and the high-speed camera 122 that is the speed field measuring means are transparent facing the surface on which the pressure-sensitive paint 111 is applied. As shown in FIG. 1A, the visualization light source 121 is disposed outside a transparent surface adjacent to the surface to which the pressure-sensitive paint 111 is applied.

The pressure field measurement process consists of a pressure-sensitive paint 111 that can generate a sufficient amount of light emission and a sufficiently high-speed response than the frequency of the unsteady phenomenon assumed for the measurement object, and a large number of continuous time series with sufficient spatial resolution. A pressure field measuring unit comprising a high-speed camera 112 capable of acquiring a high-speed camera 112 and an excitation light source 113 having a sufficiently large excitation light amount including the absorption line wavelength of the pressure-sensitive dye contained in the high-speed response type pressure-sensitive paint 111. And are used.
The light emission of the pressure-sensitive paint 111 and the excitation light of the pressure-sensitive paint 111 projected by the excitation light source 113 are optically separable lights, respectively, and the projection light of the visualization light source 121 used in the velocity field measurement process described later. Light that is optically separable from scattered light or emitted light from the sublimable particles 131 is used.
The high-speed camera 112 is provided with an optical filter 114 that removes light other than light emitted from the pressure-sensitive paint 111, and selectively obtains light emitted from the pressure-sensitive paint 111, and emits light from the speed field measurement process. Remove the effect.

Using these means, obtain a measurement object luminescent image with pressure-sensitive paint 111 for multiple conditions of static and known pressure fields, and use the relationship between the known pressure information and the acquired luminescent image. Thus, a calibration formula for measuring the pressure of the pressure-sensitive paint 111 to be measured is obtained.
When the wavelength of light absorbed by the visualization light source 121 or the particle 131 in the velocity field measurement process is present in the wavelength range absorbed by the pressure-sensitive paint 111, these lights are the same or similar within the range possible. The calibration equation and the reference image for measuring the pressure of the pressure-sensitive paint 111 to be measured are obtained.

In the velocity field measurement process, it is possible to irradiate two or more shots continuously in an extremely short time interval to the extent that it can be assumed that the fluid phenomenon does not change, and the frequency of the unsteady phenomenon assumed for the measurement object. A visualization light source 121 comprising a laser oscillation means capable of continuously forming a pair of laser irradiations at a sufficiently high frequency and capable of forming a sheet-like laser irradiation light by a high repetition laser irradiation having a sufficient luminance is used. The sublimable particles 131 that pass through the measurement target region together with the airflow are irradiated by the projected laser irradiation light.
The scattered light or light emission from the particles 131 of the irradiated laser irradiation light has sufficient spatial resolution, can acquire a large number of images continuously in time series, and can be synchronized with a high repetition laser at high speed. Photographing is performed using a velocity field measuring unit comprising the camera 122.
The laser light irradiating the particles 131 and the scattered light or light emission from the sublimable particles 131 are optically separable from the excitation light of the pressure-sensitive paint 111 and the light emission of the pressure-sensitive paint 111 projected by the excitation light source 113. .

The high-speed camera 122 is provided with an optical filter 123 that removes light other than the scattered light or light emission of the sublimable particles 131 and selectively acquires the scattered light or light emission of the sublimable particles 131.
As the sublimable particles 131 dispersed in the air stream, particles such as dry ice that do not contaminate the surface of the pressure-sensitive paint 111 and do not interfere with the pressure field measurement process are used.
In supplying and spraying the sublimable particles 131, a single system or a plurality of systems are used. It is assumed that the particle spray nozzle 107 has a single hole or a hole that enables the diameter of the sublimable particles 131 to be changed and allows the uniform sublimable particles 131 to be sprayed.

Measurement that enables measurement of physical quantities such as total temperature, total pressure, composition, and sound velocity of airflow in preparation for the case where some of the sublimable particles 131 sublimate in the airflow and the physical conditions of the airflow to be measured change. The system is installed, these physical quantities are measured, and the change in airflow conditions can be corrected after measurement.
As the air flow to be measured, a dry gas that can predict in advance the influence of the air flow change caused by using the sublimable particles 131 and can suppress the influence of moisture condensation so as to minimize the influence is used.
In consideration of the influence of fluid physical quantities due to composition changes, this dry gas has a gas composition, total temperature, and temperature that have the same or similar dimensionless numbers that govern the target fluid phenomenon such as Reynolds number and Mach number. It is a mixed gas having a total pressure, and is stored or generated in the gas supply means 105.

Next, a specific example of the fluid measuring method and the fluid measuring apparatus according to the present invention will be described below.
<Measurement target>
The wall pressure field and space velocity field were measured for a shock wave group in a supersonic flow called a pseudo shock wave as shown in FIG. One surface of the rectangular duct 101 was painted with a pressure-sensitive paint 111, and the pressure field was measured. The velocity field was measured for a cross section parallel to the wall surface where the pressure field was measured and passing through the center of the rectangular duct 101.

<Experimental equipment>
In the system of the present embodiment in which unsteady pressure-sensitive paint measurement and time-series particle image flow velocity measurement were simultaneously performed, an air bag as the gas supply unit 105 of the fluid measurement device 100 of the above-described embodiment illustrated in FIG. A supersonic nozzle was used as the airflow forming nozzle 104, and a vacuum tank was used as the suction means 102.
The particle supply tank 106 was a carbon dioxide cylinder, and the sublimable particles 131 sprayed from the particle spray nozzle 107 were fine powder of dry ice.
The most upstream air bag is for filling with dry air. When humid air was used, dry air was used because moisture in the humid air was condensed during the supply of dry ice, which hindered measurement. Two particle supply systems were installed in the particle supply container 108. The supersonic nozzle has a design Mach number of 2.0.

The upper plate of the rectangular duct 101 of the measurement unit is made of metal, and one of the bottom plate and the two side plates on the camera side is made of transparent acrylic. The remaining side plates were made of metal, and a high-speed response type porous pressure-sensitive paint 111 was coated on the inner surface side.
The downstream valve 103 is a manual butterfly valve. By opening the valve 103, the dry air in the air bag and the supplied dry ice are accelerated through the supersonic nozzle. The accelerated airflow passes through the rectangular duct 101 of the measurement unit and is sucked into the vacuum tank.

<Pressure sensitive paint measuring system>
The pressure-sensitive paint measurement system includes an excitation light source 113 and a high-speed camera 112 as pressure field measurement means in addition to the above-described painted surface of the pressure-sensitive paint 111.
The coated surface of the pressure sensitive paint 111 was manufactured as follows. The used plate material is an Al-Mg alloy (A5052). Using this plate material as an anode, current was passed in an acidic electrolyte (sulfuric acid, oxalic acid, phosphoric acid). In this way, an anodized aluminum film was formed on the surface of the plate material by anodizing the surface. After the anodizing treatment, the plate material was immersed in a phosphoric acid solution in order to remove the hydrate on the model surface. Furthermore, in order to remove phosphoric acid, it was immersed in distilled water several times. [Ru (dpp) ₃ ] ²⁺ was used as the pressure-sensitive paint dye, and a solution containing the pressure-sensitive paint dye was prepared using dichloromethane as a solvent. The plate material subjected to the above treatment was immersed in a solution containing the pressure-sensitive paint pigment, thereby adsorbing the pressure-sensitive paint pigment on the plate material. After drying, a hydrophobization treatment was performed by immersing the plate material on which the pressure-sensitive dye was adsorbed in a solution of stearic acid in hexane.

As the excitation light source 113, light having a wavelength different from that of the light source used in the particle image velocimetry described later is used. As the excitation light source 113 for pressure-sensitive paint measurement, a semiconductor laser having an emission wavelength of 450 to 455 nm was used. From the irradiator connected to the liquid light guide, the wall surface coated with the pressure-sensitive paint 111 was irradiated through the transparent acrylic window on the side wall of the rectangular duct 101 serving as the measurement unit.
The high-speed camera 112 that measures light emission from the pressure-sensitive paint 111 uses a CMOS high-speed camera (Phantom V7.3, Vision research) equipped with a lens (Nikkor 50 mm f / 1.2, Nikon). A band pass filter (O58 filter) was attached to the front surface of the lens as an optical filter 114 for removing light other than the above light emission.

<Particle image flow velocity measurement system>
The particle image flow velocity measurement system includes a particle supply system using dry ice particles as tracer particles as sublimable particles 131, a laser sheet system for projecting sheet-shaped laser irradiation light for visualizing the tracer particles, and scattered light from the tracer particles. Or it is comprised from the high speed camera 122 which is a speed field measurement means which measures light emission.
The particle supply system was configured by a liquefied carbon dioxide cylinder as a particle supply tank 106, a particle supply container 108, and a particle spray nozzle 107.
As shown in FIG. 3, the particle spray nozzle 107 includes an injector 132 having a minute hole 134 and a metal tube 133 downstream of the injector 132. In this example, dry ice particles were supplied by injecting liquefied carbon dioxide from the micro holes 134 having a diameter of 1 mm. A metal tube 133 having a large number of side holes 135 was installed downstream of the minute holes 134 having a diameter of 1 mm. By installing this metal tube 133, it is possible to promote the growth of dry ice particles, and it is possible to uniformly disperse it in the air current.

The laser sheet-based visualization light source 121 includes a 532 nm high repetitive double pulse neodymium yag (Nd: YAG) laser (rated output of 10 mJ / pulse at 10 kHz, LDP-200MQG DUAL DIODE PUMPED), which is different from the emission wavelength of the pressure sensitive paint 111 LASER, LEE LASER) were used. The visualization light source 121 has two laser heads, and can irradiate two laser beams at a short time interval by irradiating the laser beam at a shorter time interval than each laser head. Sheet-shaped laser irradiation light was formed by a lens system including a cylindrical lens, and was irradiated from the bottom plate of the rectangular duct 101 made of transparent acrylic.
The high-speed camera 122 that measures the scattered light from the dry ice particles irradiated by the sheet-like laser light is a CMOS high-speed camera (Phantom V710, Vision research) equipped with a lens (Nikkor 105mm f / 2, Nikon). Was used.
An interference filter (532 nm transmission) is mounted on the front surface of the lens as an optical filter 123 for removing excitation light and light emission of the pressure-sensitive paint 111 measurement, and scattered light from dry ice particles is selectively selected by the high-speed camera 122. I took a picture.

<Synchronous system>
FIG. 4 shows a schematic diagram of a synchronized system of a pressure sensitive paint measurement system (PSP) and a particle image flow velocity measurement system (PIV).
There are a plurality of particle image velocimetry methods, and the synchronization method of the camera and the laser is different for each method. In this embodiment, the particle image velocimetry is a method of capturing two consecutive frames, one exposure per frame. An image was taken. Four systems of signals are generated from a high speed camera synchronization signal device (High speed controller) which is a signal generator.
The first system is a signal (Q1) directed to the laser at the first time of the particle image velocimetry system. This signal is branched into two systems in the midway delay signal generator (DG535). One system branched from the delay generator is input to Laser 1 without being delayed. A signal delayed by the delay signal generator is output to the remaining one system. This delayed signal is input as a synchronization signal of the camera for pressure sensitive paint measurement.
The second system (Q2) output from the high-speed camera synchronization signal device is directly input to Laser2. Two lasers (Q1, Q2) output from the high-speed camera synchronization signal device set the oscillation interval of one set of lasers.

The third system (cam1) output from the high-speed camera synchronization signal device is input as a synchronization signal of the particle image velocimetry camera. The three systems (Q1, Q2, cam1) synchronize the particle image velocimetry camera with the laser. In addition, the particle image flow velocity measurement system and the pressure-sensitive paint measurement system are synchronized with each other by a delay signal directed to the pressure-sensitive paint measurement camera branched from the delay generator and these three systems (Q1, Q2, cam1).
The fourth system (Trigger) output from the high-speed camera synchronization signal device is a signal for inputting the measurement start timing. In the embodiment, in order to use the pressure value of the test section as a trigger, a trigger signal is generated from a signal generator (Pulse Generator) based on the voltage signal of the pressure measurement system, and the high-speed camera synchronization signal is based on that signal. A trigger signal for starting measurement was generated from the device. These signals are branched into three, one line is sent to the particle image flow velocity measuring camera, one line is sent to the pressure sensitive paint measuring camera, and the last one line is sent to the data recording logger (WE7000) for recording.

The captured images of the pressure-sensitive paint measurement camera and the particle image flow velocity measurement camera are sent to each measurement PC via an Ethernet (registered trademark) cable.
FIG. 5 shows the synchronization timing of the pressure-sensitive paint measurement camera (PSP CAMERA), the particle image flow velocity measurement camera (PIV CAMERA), and the two lasers (LASER1, LASER2) realized by the above-described synchronization system. The rise time of the line represents the exposure time for the camera, and the light emission time for the laser.

<Pressure-sensitive paint measurement calibration method and data processing method>
The calibration coefficient for pressure sensitive paint measurement was derived by the following procedure. First, an image of the pressure-sensitive paint painted surface is taken without excitation light and illumination. This is called a dark image. Thereafter, the pressure of the measurement unit is changed by a vacuum pump and dry air at intervals of 10 kPa. Under each pressure condition, an excitation light source is irradiated and a light emission image of the pressure-sensitive paint coating surface is taken. This is performed for about 10 points from 10 kPa to atmospheric pressure.
The dark image is subtracted from the photographed emission image to remove noise components. The light emission image group under each pressure reduced from the dark image is averaged. The emission intensity image of the average emission image in the atmospheric pressure state (P _ref ) is _defined as a reference emission intensity image (I _ref ). The reference emission intensity image (I _ref ) is divided by the average emission intensity image (I) at each pressure to obtain an intensity ratio image (I _ref / I) of both. Using the obtained pressure-sensitive paint emission intensity image and pressure data at the time of measurement, a calibration coefficient is calculated. Each emission intensity image and dark image were obtained by acquiring and averaging 200 images. The relationship between the emission intensity ratio and the pressure is represented by a Stan-Volmer equation. In the calibration, a coefficient part of a formula obtained by modifying the Stan-Volmer formula with respect to the pressure was obtained from the known pressure and the emission intensity ratio at the time of calibration. In the measurement, the light emission intensity ratio was measured, and the pressure field was obtained based on an equation modified from the issued intensity ratio.
The process of obtaining the calibration formula is shown in FIG. In the present embodiment, the calibration coefficient is obtained for each fixed region based on the process of FIG. 6 in consideration of the variation of the calibration coefficient in the measurement unit.

In the measurement, first, a dark image and a reference emission intensity image (I _ref ) were taken under atmospheric pressure. Since the laser light used in the particle image flow velocity measurement enters the absorption band of the pressure-sensitive paint, when taking a reference emission intensity image, in addition to the excitation light for pressure-sensitive paint measurement, a sheet image for particle image flow velocity measurement A reference emission intensity image (I _ref ) was taken by irradiating the laser irradiation light. Then, the wind tunnel was started and the ventilation image (I) was image | photographed. After subtracting the dark image from the reference emission intensity image _{(I ref)} and ventilation image (I), the reference luminous intensity image _{(I ref)} and the intensity ratio of the draft image (I) and _{(I ref} / _I) was obtained. The pressure was calculated from this intensity ratio.

<Particle image velocimetry data processing method>
In the particle image flow velocity measurement, a scattered light image of particles as shown in FIG. 7 was acquired. An image obtained by photographing the measurement part in a state where only the sheet-like laser irradiation light was irradiated without flowing the tracer particles was used as a background image. Processing was performed on the image obtained by subtracting the background image from the scattered light image of the particles. An area of 64 pixels × 64 pixels was cut out from the image at the first time, and pattern matching was performed using the correlation method with the image of the same area at the second time. The amount of movement with the highest correlation value was taken as the distance of particle movement. The moving speed of the particles was calculated by dividing this moving distance by the time interval of laser irradiation at the first time and the second time.

<Result>
FIG. 8 shows a pressure field and a velocity field measured by a combined system of a pressure-sensitive paint measurement system and a particle image flow velocity measurement system in order of time from FIG. 8 (a) to FIG. 8 (d). The upper distribution diagram represents the pressure field, and the lower vector diagram represents the velocity field. The measurement start time is 0 s, and the measurement times of the pressure field and velocity field are shown in the upper left of the figure. The airflow is flowing from left to right. The pressure distribution is actually a color image, and indicates that the pressure is higher as the color is closer to red (color with density from the right), and the pressure is lower as it is closer to blue (color with density from the left). It can be seen that the pressure increases from the downstream side as time passes. Moreover, the change of the pressure change is clear and it can be seen that the pressure is changed by the shock wave.
The lower speed vector diagram is actually a color image, and the closer the color is to red, the faster the speed is, and the closer the color is to blue, the slower the speed is (the dark color near the center in FIG. 8A is red). The dark color near the upper and lower ends of FIG. 8D is blue.) It can be seen that at T = 1.0000 s, the color of the vector is red in almost the entire region, indicating a supersonic airflow. In the pressure distribution at the same time, a pressure increase can be seen even at the same position.
From the velocity vector data, it can be seen that even if there is an increase in pressure on the wall surface, a high-speed airflow flows in the center of the duct, and the shock wave does not reach the velocity field measurement region in the center of the duct. When T = 1.565 s, it can be seen that in the velocity vector diagram, a shock wave exists on the downstream side on the right side of the drawing, the boundary layer in the vicinity of the wall surface that interferes with the shock wave peels off, and a low speed region exists. When the time further advances, as shown in FIGS. 8C and 8D, the color of the vector is switched to green (bright color near the center), and it can be seen that the air flow velocity is decreased opposite to the pressure.

  In order to show that the response characteristic of the pressure sensitive paint measurement is not lost by the dry ice particles, FIG. 9 shows a comparison of the pressure distribution of the unsteady pressure sensor (manufactured by Kulite) and the pressure sensitive paint measurement. In FIG. 9, the vertical axis represents the wall pressure made dimensionless at atmospheric pressure, and the horizontal axis represents the measurement time. The dark line (transition on the upper side) is the measurement result of the unsteady pressure sensor, and the thin line (transition on the lower side) is the result of the pressure-sensitive paint measurement. As shown in the lower part of the enlarged figure, the two fluctuations are in good agreement and contain a certain amount of bias error, but the response characteristics of unsteady pressure-sensitive paint measurement are not lost by dry ice particles. I understand that.

The fluid measuring method and the fluid measuring device according to the present invention are used in aerospace field, transportation machines such as railways and automobiles, fluid machines such as air conditioners, fans and windmills, engines, medical fields and chemical plants. It can be used for measurement of flow fields that cause problems such as vibration, noise, and metal fatigue that correlate unsteady pressure field and unsteady velocity field over a wide range of fields such as pipe flow.
In these fields, obtaining the spatial information of the unsteady flow that generates the unsteady pressure field from the velocity field makes it easy to identify the mechanism and shape that cause the unsteady flow. As a result, it is a basic technology that can be used for various purposes such as machine design and efficiency improvement in these fields, noise and vibration reduction.

DESCRIPTION OF SYMBOLS 100 ... Fluid measuring apparatus 101 ... Rectangular duct 102 ... Suction means 103 ... Valve 104 ... Airflow formation nozzle 105 ... Gas supply means 106 ... Particle supply tank 107 ... Particle Spray nozzle 108 ・ ・ ・ Particle supply container 111 ・ ・ ・ Pressure sensitive paint 112 ・ ・ ・ High speed camera 113 ・ ・ ・ Excitation light source 114 ・ ・ ・ Optical filter 121 ・ ・ ・ Visualization light source 122 ・ ・ ・ High speed camera 123 .... Optical filter 131 ... Sublimable particle 132 ... Injector 133 ... Metal tube 134 ... Micro hole 135 ... Side hole

Claims (6)

A fluid measurement method for measuring a dynamic property of a fluid, comprising:
A pressure field measuring step for optically measuring the pressure distribution on the surface of the object in contact with the fluid with a pressure sensitive paint, and a velocity field measuring step for optically measuring the spatial behavior of the fluid by dispersing visible particles in the fluid; Have
The pressure-sensitive paint has a light emission intensity that changes due to a change in oxygen concentration according to the pressure of the fluid, and the visible particles are sublimable particles.
A fluid measurement method, wherein the pressure field measurement step and the velocity field measurement step are performed simultaneously, and information on the pressure field and the velocity field for the same event is acquired as information correlated in the time direction.   Light source projection light for particle visualization in the velocity field measurement step, scattered light or light emission from the particle, light source projection light for pressure-sensitive paint excitation in the pressure field measurement step and pressure-sensitive paint emission A fluid measurement method comprising an interference elimination step of eliminating the influence of each optical interference.   The fluid measurement method according to claim 2, wherein the interference eliminating step is performed by an optical filter.   The fluid measurement method according to claim 2, wherein the interference rejection step is performed by arithmetic processing of the pressure field measurement step and the velocity field measurement step. A fluid measuring device for measuring dynamic characteristics of a fluid,
A pressure-sensitive paint that is provided on the surface of an object in contact with the fluid, and whose emission intensity changes with a change in oxygen concentration according to the pressure of the fluid;
A particle spraying means for spraying visible sublimable particles in the fluid;
An excitation light source that projects excitation light onto the pressure-sensitive paint;
Pressure field measuring means for measuring light emission of the pressure sensitive paint;
A visualizing light source for projecting light for visualizing the sublimable particles;
Velocity field measuring means for measuring scattered light or luminescence from the sublimable particles;
A fluid measurement apparatus comprising: information acquisition means for acquiring measurement information for the same event of the pressure field measurement means and the velocity field measurement means as information correlated in the time direction. The pressure field measuring means is not directly received by the projection light of the visualization light source, and the velocity field measurement means is disposed so as not to directly receive the projection light of the excitation light source,
6. The fluid measuring device according to claim 5, wherein each of the velocity field measuring unit and the pressure field measuring unit includes an optical filter that reduces light other than light to be observed.