JPH0654279B2 - 3D observation method of flow - Google Patents

Description

Detailed Description of the Invention I. Object of the Invention (Industrial field of application) The present invention is one of the methods for three-dimensional analysis of flow behavior, and enables flow behavior to be qualitatively and quantitatively observed three-dimensionally. For how to.

(Prior Art) Visualization of flow is the most common method for observing flow behavior. Most of the visualization of the flow was originally limited to qualitative observation, which mainly focuses on the flow state and flow direction including separation of the flow and generation of vortices. Even if sufficient accuracy cannot be expected yet, quantitative measurement is becoming possible. For example, it has become possible to easily obtain the flow velocity distribution of an arbitrary flow field from a tracer trace obtained by using intermittent light, or from a timeline by an electric control method capable of electrically controlling the generation of the tracer. It was

(Problems to be Solved by the Invention) However, when analyzing the behavior of a flow by a conventional visualization method, since it is generally performed based on a tracer trace recorded in a photograph or the like, a planar flow, that is, The behavior in a three-dimensional flow can only be grasped, and the mechanism of a three-dimensional flow with swirl, vortex, or fluctuation, that is, three-dimensional flow, has not been quantitatively evaluated.
That is, when observing the behavior of laminar flow, it is sufficient to set the observation cross section in the flow direction and understand the flow behavior in the observation cross section, but under turbulent flow conditions, the flow direction always changes. Therefore, it is necessary to understand the behavior of the flow in the direction orthogonal to the observation cross section. Therefore, when three-dimensional behavior such as turbulent flow is shown, it is virtually impossible to set the plane flow observation cross section so as to match the three-dimensional flow direction. Three-dimensional analysis is difficult with the visualization method. Therefore, it is required under turbulent flow conditions to be able to observe the behavior of the flow in the direction orthogonal to the observation cross section, that is, in the direction deviating from the observation plane.

The present invention realizes three-dimensional analysis of unsteady flow,
It is an object of the present invention to provide a stereoscopic visualization method of a flow that enables three-dimensional observation.

II. Configuration of the Invention (Means for Solving the Problems) In order to achieve such an object, the three-dimensional flow observation method of the present invention uses a fluid in which a tracer composed of fine particles or fine bubbles is dispersed at a uniform concentration. While forming a flow field,
This flow field is simultaneously illuminated by using multiple slit lights in different wavelength bands, and multiple cross sections are visualized at the same time by scattering due to the tracer of the illumination light. By obtaining the correlation between a plurality of observation cross sections formed by scattered light in the wavelength band, qualitative and quantitative information about the flow behavior in three dimensions of the flow is detected.

(Embodiment) First, a specific apparatus example for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 2 is a schematic diagram showing an example of a visualization device for reproducing the flow field. This visualization system is a model tank 1 that reproduces the flow field.
And a fluid supply unit 2 and a model tank 1 for supplying a fluid in which a tracer 4 is dispersed in the model tank 1 at a uniform concentration.
It is mainly composed of a slit light source 3 which irradiates a planar light 5 converged on a flow field inside. In this visualization device, the fluid flowing from the bottom surface of the model tank 1 reproduces the flow field in the model tank 1, and then is discharged from the discharge port 6 above the model tank 1 through a discharge pipe (not shown).
The fluid is usually discharged as it is or after being subjected to necessary treatment, to the outside of the tank. The fluid can be introduced from above the model tank 1 and discharged from the bottom surface, or can be introduced from the side surface and discharged from another surface.

The model tank 1 is preferably made of a material that does not absorb light in a specific frequency band, particularly light in the visible region. For example, a translucent material such as acrylic resin or glass makes the model tank 1 circular or square. Is formed into a predetermined shape. The model tank 1 is merely a container for forming a finite flow field when the model is installed inside, but is itself used as a model when visualizing the fluid flow in the pipe. It Moreover, when reproducing the flow field in an infinite space, instead of the model tank 1, the entire laboratory is used as the flow field to obtain a static space. The model tank 1 has a discharge port 6 above it and an injection port 7 on the bottom surface, and a model 8 for reproducing a flow field to be observed is generally attached to the injection port 7 on the bottom surface. However, model 7
It may be installed in the model tank 1 at a distance from, and the fluid flow may not be changed at the injection port 7. In the model tank 1 of this embodiment, the entire peripheral wall is formed of a material that transmits visible light, but it is not necessary to form the entire peripheral wall of a transmissive material, and at least the surface for observing scattered light and the slit light are incident. It suffices if the surface to be transparent has translucency. For example, since optimum diffused reflection is obtained at the position of the angle θ of 90 to 145 degrees with the incident direction of the slit lights 5B, 5G, and 5R, it is sufficient to position the observation window and the incident window in that range, and the rectangular model When the tank 1 is used, it is sufficient if at least two adjacent surfaces are made of a translucent material. In this case, if the peripheral wall surface other than the observation window and the entrance window is formed of a light absorber, the scattered light can be detected very easily. Furthermore, when observing the flow field in slices, slit light 5B that crosses the flow field,
In order to observe 5G and 5R, an observer or an observation device is arranged above the model tank 1.

Fluid supply unit 2 for supplying fluid to the model tank 1 described above
Is provided by providing a tracer injection part 10 in the middle of a conduit 9 connecting a fluid supply source (not shown) and the model tank 1 and quantitatively forcibly injecting the tracer 4 into the fluid being pumped or by generating the tracer 4. It is supplied as a fluid having a constant concentration. Of course, the supply unit 2 is not limited to the above. For example, it is also possible to store a fluid whose concentration is optimized for visualization in advance in a tank, take it out with a metering pump, and send it under pressure to the model tank 1.

The fluid forming the flow field is a gas or liquid in which a tracer 4 composed of fine particles or fine bubbles is dispersed at a uniform concentration, and the tracer is as far as possible within the range that does not affect the formation of the flow field. 4 is maintained at a density that is densely and uniformly present.

When a gas is used as the dispersion medium, air is used, and when a liquid is used, water is most commonly used, but the present invention is not limited to this, and other materials may be used as necessary. Gas may be used.

As the dispersed phase, that is, the tracer 4, it is preferable to employ fine particles typified by colloidal particles or fine bubbles. As a tracer 4 when a gas is used as the dispersion medium, fine particles of about 1 μm in diameter are easily available, such as MgO, Si.
So-called fine ceramic spheres such as O and Al ₂ O ₃ are suitable. This is because the fine particles made of fine ceramics are easy to handle and a gas colloid having a constant concentration is easily obtained. Of course, a gas colloid using fog or smoke as a tracer can be used if it is sufficiently homogenized.

Further, as the tracer 4 when a liquid is used as the dispersion medium, it is preferable to adopt milk or the like containing extremely fine milk fat globules, in addition to the fine ceramics described above. In particular, milk is one of the most preferable tracer fine particles because it is easily available, inexpensive, easy to handle and obtains scattered light with high brightness. Among them, processed milk generally has milk fat globules having a diameter of 2 μm or less (less than 1 μm, 41.8%, 1-2).
Since it is adjusted to 4 μm (47.7%), it is suitable for forming a colloid in a liquid. Therefore, in the case of this example, 0.2% by weight of processed milk is included in water to form the hydrocolloid.

Incidentally, when fine ceramics fine particles are adopted, unlike milk, it is not possible to immediately form a colloidal state by simply pouring the fine particles directly into the flow. Therefore, a highly concentrated colloidal solution prepared by immersing fine ceramics in a small amount of water is prepared. This highly concentrated colloidal solution is prepared, for example, by agitating and mixing a fixed ratio of water and fine ceramic particles in a tank under reduced pressure, and completely removing the bubbles adhering to the surface of the particles. This highly concentrated colloidal solution is quantitatively supplied to the fluid supply unit 2 using a metering slurry pump,
It is mixed with water supplied from a fluid source to form a colloidal solution of constant concentration.

When a liquid is used as the dispersion medium, 0.06
~ 0.2 mm fine bubbles, more preferably 0.1 ~
It can be used if fine bubbles of 0.2 mm can be dispersed at a uniform concentration. The fine bubbles have a diameter of 3 mm or less, preferably 0.8 to 0.5 mm in the middle of the pipe line 9 of the fluid supply unit 2.
By installing an orisui (not shown) with at least one small hole in the
%, Fine air bubbles averaging 0.1 mm are degassed by local decompression, and a large amount can be continuously and stably supplied.

In the case of the above-mentioned gaseous colloid, the tracer 4 is quantitatively supplied to the fluid supply unit 2 by using a quantitative injection device and mixed with air supplied from the fluid supply source to form a constant concentration, or in advance. The air and the tracer 4 are mixed and stirred to have a constant concentration and then supplied to the model tank 1.

The flow field reproduced by the fluid containing the tracer uniformly and densely is provided so that any position of the flow can be illuminated and visualized by the planar illumination represented by the slit lights 5B, 5G and 5R. ing. Slit light 5B, 5
G and 5R can be easily obtained by a known slit light source 3 or by expanding a laser beam in the visible range by using a two-dimensional optical system. Further, by oscillating the laser beam as it is at a high speed, it can be used as a substantial slit light.

As the slit lights 5B, 5G, and 5R, a plurality of lights having different wavelength bands are used for each irradiation cross section. Light having a different wavelength band is one in which the main wavelength band is different from other lights, and it is preferable to appropriately select from red, orange, yellow, green, indigo, and purple single-color light. It is most preferable to use light of a single wavelength, but it is possible to implement light of a color composed of a combination of these as long as it can be distinguished from other light in the wavelength band. It should be noted that it is preferable to use light in the visible region as the slit light for observation and image processing, but it is not limited to this, and it is possible to use light in the infrared region or ultraviolet region by making the imaging device side compatible. is there.

The use of monochromatic light as the illuminating light is preferable, and among these, the use of light of the three primary colors of light, red, green and blue, is most suitable for facilitating the subsequent image processing. This is because a known ITV camera, a color TV camera, or the like, which is easily available, can be used as the image pickup means when using monochromatic light whose band separation is easy. Therefore, the wavelength band to be used is basically selected from the three primary colors of light, and another single color or a composite color may be added to this in accordance with the number of visible cross sections, or one color may be excluded. The slit lights 5B, 5G, 5R of the specific wavelength band are bandpass filters 11B, 11G, 11R that mainly transmit the slit light easily obtained from white light of the specific wavelength band of an arbitrary color. It is easily obtained by passing through. Further, it can be obtained by dispersing white light using a prism or the like and then extracting light / color in an arbitrary wavelength band, or by using laser light in the visible region as a light source.

On the other hand, as means for simultaneously imaging a plurality of flow fields visualized by scattering of the slit illumination lights 5B, 5G, and 5R described above, a plurality of light beams of specific wavelength bands corresponding to the respective wavelength bands of the illumination light are transmitted. Bandpass filter 1
2B, 12G, 12R ... and the filters 12B, 12
A plurality of image input devices 13B, 13G, 13R ... Each of which inputs image information for each wavelength band that transmits G, 12R ...
It consists of and. Bandpass filter 12 on the image input side
B, 12G, 12R ... Mainly transmit light in a specific wavelength band used as illumination light, and a plurality of types are prepared corresponding to a plurality of illumination lights having different wavelength bands. . On the other hand, the image input device is appropriately selected and used from known devices according to the image processing method. For example, TV
It is preferable to use an optical type such as a camera or a video camera, or a type such as a high-speed camera, and especially RG.
Color TV with built-in B image pickup tube and bandpass filter
The use of a camera is preferable because a plurality of image information on one optical axis can be obtained at the same time. Where color TV
In the case of a camera, if the light in the red, green, and blue wavelength bands is used as the illumination light, the visible flow field for each cross section will be one camera only by imaging the visible cross section with a deep depth of field. At the same time, the images are simultaneously captured, and each of them is divided into RGB signals and input as separate image information. Therefore, these RGB color signals are individually taken out and directly output as an image signal or as a digital electric signal through high-speed A / D conversion to be used for visualization or for measurement or recording or recording, and are included in the image. Detects qualitative and quantitative information of the flow being carried. For example, when directly displayed on a commercially available monitor television, the flow field is displayed as a black and white image with a gradation corresponding to the brightness of scattered light or as a single color image. Of course, the qualitative and quantitative information about the behavior of the flow, which is replaced by the brightness of the scattered light, is not only used as the image information as it is, but also used by other forms by appropriately performing analog image processing or digital image processing. Sometimes For example, it is possible to convert a TV luminance signal into a color display having a lightness and a hue corresponding to luminance by computer processing or the like.

The bandpass filter in the present specification is a single filter that mainly transmits light in a specific wavelength band, and a short wavelength cut filter and a long wavelength cut filter in combination to provide light in a specific wavelength band only. It also includes other filters such as those that allow light to pass through.

The multi-sectional simultaneous visualization method of the flow of the present invention using the visualization device configured as described above is carried out as follows.

First, the fluid in which the homogeneous tracer 4 is densely dispersed toward the model tank 1 or the infinite space is stably supplied into the tank as much as necessary to create a desired flow field. As the fluid containing the tracer 4, a fluid which forms a flow field and is adjusted in advance to a concentration suitable for visualization, or a fluid which is mixed and adjusted during pumping in the fluid supply unit 2 is used. Then, the slit light 5 having different wavelength bands from each other is added to this flow field.
B, 5G, and 5R are simultaneously irradiated to arbitrary different sections, and each slit light 5B, 5G, and 5R is diffusely reflected by the tracer 4 to extract and visualize the flow in an arbitrary cross section.

The cross section of the flow field visualized by the scattering of the plurality of slit illumination lights 5B, 5G, and 5R, that is, the observation cross section, is unclear and indistinguishable by the eyes of the observer, but the band pass filters 12B, 12G, and 12R. .. are separated for each wavelength band, that is, separated and input as image information for each cross section. The image formed by the intensity of scattered light and its variation due to the density of the tracer 4 contains various qualitative and quantitative information such as the concentration of the flow field and its variation, and the flow velocity. Therefore, if each image input is output as it is using a monitor TV or the like and visualized, the movement of the tracer 4 in different cross sections of the same flow field, that is, the flow behavior can be simultaneously tracked by an image. Therefore, not only the flow phenomenon in one plane, the flow direction, etc., but also the qualitative information in the three-dimensional direction can be accurately known. Here, it is considered that the intensity of the light scattered by the tracer 4 which is sufficiently fine and homogeneous is proportional to the number of tracers in a unit volume, that is, the tracer density, which means that the intensity of the scattered light corresponds to the concentration. The concentration and concentration distribution can be visually observed at the same time depending on the intensity of scattered light due to the density of the tracer 4.

The concentration is represented by a number density in a mixed state of a fluid containing the tracer 4 and a fluid not containing the tracer 4, and has a similarity relationship with the brightness of scattered light, and is a ratio of the fluid not containing the tracer 4 in the two fluids in the mixed state. Since the tracer amount in the unit volume decreases and the brightness is lost as the value becomes higher, the brightness at the other points is quantitatively obtained with the brightness near the injection port 7 as the reference brightness (corresponding to 100% density). . For example,
The flow field of each section is displayed on a monitor TV, and the intensity of light, that is, the density of the light, is detected by converting it into an electric signal by a photo sensor installed near the injection port and on the cathode ray tube corresponding to an arbitrary measurement point. After the electric signal is passed through the filter 23 to remove the screen scan signal, the signal is passed through the transient recorder to the oscilloscope or XY.
It can be output to a recorder and measured or recorded.
Moreover, in this measurement, the concentration of the fluid in different sections of the flow field is visualized at the same time and image processing is performed, so that the instantaneous concentration distribution in the entire flow field can be analyzed three-dimensionally and quantitatively.

Furthermore, the behavior of the flow in each section is
As a group movement, diffusion, and aggregation phenomenon, that is, a variation in concentration, a change in an image composed of a set of scattered light, for example, a variation in brightness can be easily compared and known. That is, in a flow field created by a fluid in which fine and homogeneous tracers 4 are densely contained, a phenomenon in which a group of constant concentration tracers 4 moves appears as a concentration change at one measurement point. Then, the movement phenomenon of the tracer group appears as a density change of a waveform that is very similar at a very close point. Therefore, for example, the behavior such as the velocity of the flow varies with time in the time until a very similar waveform concentration change is observed between two points that are very close to each other in the same section or between two points that are two sections that are very close to each other in three dimensions. By detecting the deviation, the velocity of the flow in the two-dimensional direction or the three-dimensional direction can be measured. Further, the flow direction can be three-dimensionally obtained by obtaining the correlation of the concentration fluctuation between different observation cross sections.

That is, it is practically impossible to identify one colloid particle 4 and measure the time taken for the colloid particle 4 to travel a predetermined distance ΔL, but the time taken for a colloid particle group having a certain concentration to move is close. It can be understood as a time lag in the change in concentration between the two points. Further, in a flow field created by a fluid in which fine and uniform colloidal particles 4 are densely contained, a phenomenon in which a colloidal particle group having a constant concentration moves is represented as a concentration change at one measurement point. Then, the movement phenomenon of the colloidal particle group appears as a concentration change of a waveform that is very similar at other points that are very close (see FIG. 5). From this, the moving time Δt between two adjacent points of the colloidal particle group can be grasped as a time difference of the concentration change at both points. Therefore,
When very similar waveform concentration changes are observed in the flow fields of two parallel parallel planes, the velocity of the flow in the three-dimensional direction can be measured from the time shift of the concentration change between them. It should be noted that the concentration fluctuation is caused by the amount of colloidal particles in a unit volume as the ratio of the fluid not containing the colloidal particles 4 increases or the fluid becomes diluted by diffusion in a mixed state of the fluid containing the colloidal particles 4 and the fluid not containing the colloidal particles 4. And the brightness of scattered light per unit area decreases. This phenomenon appears as a change in brightness on the television screen when the image signal is used as it is.

Therefore, for example, as shown in FIG. 4, at positions where correlations are considered to be required when assuming almost the same or three-dimensional flow on the cathode ray tube of each monitor television 21B, 21G, 21R that outputs each image signal. Photo sensor 22
B, 22G and 22R are installed and the concentration fluctuation at each point is measured. Then, in the computer 24, the time lag / maximum delay time Δ of the density change occurring at each measurement point
t is calculated using the cross-correlation function method. As described above, similar concentration changes occur at the two measurement points P ₁ and P ₂ that are close to each other, as shown in FIG. Therefore, the concentration change at each measurement point is statistically processed to obtain each characteristic peak, and the maximum delay time Δt
Ask for. The maximum delay time at a certain point, that is, the moving time between the photosensors 22B and 22G of the colloidal particle group Δ
If t is obtained, v == since the minute distance ΔL between the photosensors 22B and 22G is predetermined.
The flow velocity can be easily obtained from ΔL / Δt. In FIG. 4, reference numeral 25 is a display, 26 is an XY recorder, and 27 is a printer.

Of course, the above-described density measurement and the like are realized by real-time image processing by continuously detecting with a photo sensor on the monitor TV by utilizing the brightness change of the TV image displayed using an industrial TV camera. The present invention is not limited to this, and it is also possible to immediately subject the image signal to computer processing to obtain a composite image, digitize it, or record it.

It is also possible to take an image with a high-speed photography camera and perform three-dimensional analysis. In this case, since a shooting speed of 3000 frames / second can be obtained, a great effect is exhibited in recording fluctuations in the flow field, as compared with an ITV camera having a limit of 30 to 60 / second.

III. EFFECTS OF THE INVENTION As is clear from the above description, the three-dimensional flow observation method of the present invention forms a flow field with a fluid in which a tracer composed of fine particles or fine bubbles is dispersed at a uniform concentration. The fields are simultaneously illuminated by using multiple slit lights of mutually different wavelength bands, and multiple cross sections are visualized at the same time by scattering due to the tracer of the illumination light, and this flow field is simultaneously imaged for each wavelength band, and different wavelength bands The qualitative and quantitative information about the flow behavior in three dimensions of the flow was detected by calculating the correlation between the multiple observation cross sections formed by the scattered light of the flow. Not only qualitative observations such as the flow direction and the flow direction, but also the concentration distribution and fluctuations can be observed at a glance from the intensity of scattered light, and it is formed by light in each wavelength band. By analyzing the images of multiple observation cross sections and obtaining the correlation between the observation cross sections in the three-dimensional direction, not only the three-dimensional qualitative observation of the flow field but also the instantaneous concentration distribution and its variation throughout the flow field In addition, quantitative measurement of flow velocity and the like can be performed in real time without contact. In other words, a three-dimensional analysis of unsteady flow behavior, which was impossible in the past, was realized in real time without contact.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a schematic diagram of a visualization device for carrying out a three-dimensional flow observation method according to the present invention, FIG. 3 is an explanatory diagram showing a visualized flow field, and FIG. FIG. 5 is an explanatory view showing an example of an apparatus for processing image information obtained by the three-dimensional flow observation method of the present invention, and FIG. 5 is a graph showing a time shift of concentration fluctuation in a multi-section flow field. 3 ... Slit light source, 4 ... Tracer, 5B, 5G, 5R ... Slit light of different wavelength bands, 11B, 11G, 11R ... Bandpass filter, 12B, 12G, 12R ... Bandpass filter, 13B , 13G, 13R ... Imaging means.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Atsushi Inumaru 1-16 Iwatokita, Komae-shi, Tokyo (56) References JP-A-58-154666 (JP, A) JP-A-59-87334 (JP, A)

Claims (3)

[Claims] 1. A flow field is formed by a fluid in which a tracer composed of fine particles or fine air bubbles is dispersed at a uniform concentration, and the flow field is simultaneously irradiated by using a plurality of slit lights having mutually different wavelength bands. Simultaneous visualization of multiple cross-sections by scattering due to the tracer of illumination light, simultaneously imaging this flow field for each wavelength band, and obtaining the correlation between multiple observation cross-sections formed by scattered light in different wavelength bands. A three-dimensional observation method of a flow, characterized by detecting qualitative / quantitative information relating to the behavior of the flow in the three-dimensional of the above-mentioned. 2. The three-dimensional flow observation method according to claim 1, wherein the observation cross-section is imaged for each wavelength band through a bandpass filter. 3. The three-dimensional flow observation method according to claim 1, wherein the slit light is composed of light having a single wavelength different from each other.