JPH0551856B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is one of the methods for three-dimensionally analyzing the behavior of a flow, and relates to a method of quantitatively visualizing a flow in three dimensions.

(Prior Art) Visualizing the flow is the most common means of observing the behavior of the flow. Originally, this visualization of flow was mostly limited to qualitative observation, mainly focusing on flow conditions and direction, including flow separation and generation of vortices.
Recently, it has become possible to perform quantitative measurements, although sufficient accuracy cannot be expected yet. For example, it has become possible to easily determine the flow velocity distribution of any flow field from a tracer trajectory obtained using intermittent light, or from a timeline using electrical control methods that can electrically control tracer generation. Ta.

(Problem to be Solved by the Invention) However, when analyzing flow behavior using conventional visualization methods, it is generally based on tracer trails recorded in photographs, etc.
It is only possible to understand the behavior in a planar flow, that is, a two-dimensional flow, and it has not yet been possible to quantitatively evaluate the mechanism of a three-dimensional flow, that is, a three-dimensional flow that involves swirls, vortices, or fluctuations.

In order to realize three-dimensional analysis of flow, the present invention
The purpose of this invention is to provide a three-dimensional flow visualization method that can instantaneously achieve three-dimensional visualization of a flow while allowing qualitative and quantitative observation.

(Means for Solving the Problems) In order to achieve the above object, the method for three-dimensional visualization of a flow of the present invention uses a scattering medium consisting of fine particles or fine bubbles in large quantities and uniformly to the extent that a collection of scattered light can be formed. A flow field to be visualized is formed using dispersed colloidal fluid, and this flow field is intermittently illuminated with an instantaneously moving slit light to detect the flow at different cross sections of the flow field due to diffused reflection of the scattering medium. While the brightness and darkness of light consisting of a collection of scattered lights are visualized sequentially in an instant, this is sequentially imaged and captured as image data of the flow in different cross sections of the flow field.

(Example) Hereinafter, the configuration of the present invention will be described in detail based on an example shown in the drawings.

First, the flow visualization principle of the present invention will be explained based on the visualization device shown in FIG. This visualization device includes a model tank 1 that reproduces a flow field, and a fluid supply unit 2 that supplies a fluid in which a scattering medium 4 is dispersed at a uniform concentration to the model tank 1, for example, from the bottom.
and instantaneous flat light 5 on the flow field in the model tank 1.
It mainly consists of a slit light source 3 that emits light. The fluid flowing in from the bottom of the model tank 1 reproduces a flow field in the model tank 1 and is then discharged from the drain port 6 above the model tank 1 through a discharge pipe (not shown). The fluid is normally drained as is or after any necessary treatment. still,
Depending on the case, it is also possible to introduce the fluid from above the model tank 1 and discharge it from the bottom, or to introduce it from the side.

The model tank 1 is, for example, as shown in FIG.
It is formed of a translucent material such as acrylic resin or glass into a predetermined shape, and has a drain port 6 above and a jet port 7 at the bottom. This model tank 1 is only a container for forming a finite flow field when a nozzle, a burner, etc. used. Furthermore, when reproducing a flow field in an infinite space, the entire laboratory is used as a flow field instead of the model tank 1 to obtain a static space. A model that reproduces the flow field to be observed is generally attached to the injection port 7 on the bottom of the model tank. For example, a burner nozzle model 8 and a burner tile model 9 are installed, and in order to measure the mixing state of fuel and space, its ratio, etc.
is injected, and a fluid (corresponding to secondary air) not mixed with a scattering medium is injected from the surrounding area so as to mix the two inside the burner tile model 9. However, there are cases where the model is placed in the model tank 1 away from the injection port 7 and no change is made to the flow of fluid at the injection port 7.

Here, when carrying out three-dimensional visualization of the flow according to the present invention, for example, in the case of the embodiment shown in FIG. 4A, a plurality of light sources 3 are arranged in a circle around the model tank 1, Since the slit light 5 is made to be incident on the model tank 1, the entire peripheral wall of the model tank 1 is preferably formed of a material that transmits visible light. However, the model tank 1 does not need to have its entire peripheral wall made of a transparent material, and at least the observation window 1
It is sufficient that the entrance window 11 and the entrance window 11 have transparency. For example, the incident direction of the slit light 5 and the angle θ of 90 to 145 degrees
Since optimal diffused reflection can be obtained at a position of , it is sufficient to position the observation window 10 and the entrance window within that range. Therefore, when using a rectangular model tank as in the embodiment shown in FIG. 4B for the three-dimensional visualization of the flow according to the present invention, it is sufficient to form at least two adjacent sides with a translucent material. . In this case, if the peripheral wall surface other than the observation window 10 and the entrance window 11 is formed of a light absorber, detection of scattered light becomes extremely easy. Furthermore, when observing the flow field in slices, an observer or observation equipment is placed above the model tank 1 in order to observe the slit light 5 that crosses the flow field.

The fluid supply unit 2 that supplies fluid to the model tank 1 described above includes a scattering medium injection section 13 in the middle of a pipe line 12 that connects a fluid supply source (not shown) and the model tank 1.
The scattering medium 4 is supplied as a colloidal fluid in which the scattering medium 4 is uniformly dispersed in large quantities at a constant concentration by quantitatively forcibly injecting the scattering medium 4 into the fluid being pumped or by generating the scattering medium 4. be. Of course, the supply unit 2 is not limited to the one described above. For example, a colloidal fluid adjusted in advance to the optimal concentration for visualization is stored in a tank,
This may be taken out using a metering pump and fed under pressure to the model tank 1.

The fluid that forms the flow field can be gas or liquid.
A colloidal fluid in which a scattering medium 4 consisting of fine particles or bubbles is dispersed at a uniform concentration,
The concentration is maintained such that the scattering medium 4 is present as densely and uniformly as possible within a range that does not affect the formation of the flow field. Although the fluid in this state is not a colloidal solution in the strict sense of the word, it does contain microbubbles with a diameter of about 0.1 mm and particles of 1 to 1 mm in diameter.
Since the state in which fine particles of about 2 μm are dispersed without floating or settling is similar to a colloidal solution, in this specification, to simplify the explanation, it is expressed as a colloidal fluid or simply a gas colloid.

The most common dispersion medium is air when using a gas, and water when using a liquid. The gas may also be used.

Further, as the dispersed phase, that is, the scattering medium 4, it is preferable to employ fine particles such as colloidal particles or fine bubbles. As the scattering medium 4 when a gas is used as the dispersion medium, spherical particles of so-called fine ceramics such as MgO, SiO, Al ₂ O ₃ , etc., of which fine particles with a diameter of about 1 μm are easily available, are suitable. This is because fine particles made of fine ceramics are easy to handle and gas colloids of a constant concentration can be easily obtained. Of course,
Gas colloids using fog or smoke as a scattering medium can also be used if they are sufficiently homogenized.

In addition to the above-mentioned fine ceramics, as the scattering medium 4 when a liquid is used as the dispersion medium,
Milk or the like containing extremely fine milk fat globules is preferably used. In particular, milk is one of the most preferred scattering media/fine particles because it is easily available, inexpensive, easy to handle, and provides high-intensity scattered light. Among them, processed milk generally has milk fat globules with a diameter of 2 μm or less (41.8% less than 1 μm, 47.7% 1-2 μm).
%), it is suitable for forming colloids in liquids. Therefore, 0.2% by weight of processed milk is included in water to form a hydrocolloid. Note that when fine ceramic particles are used, unlike milk, they cannot immediately form a colloidal state just by pouring them directly into a flow. Therefore, a highly concentrated colloid solution in which fine ceramics are soaked in a small amount is prepared. This highly concentrated colloid solution is
For example, it is produced by stirring and mixing a certain ratio of water and fine ceramic particles in a tank under reduced pressure, and completely defoaming air bubbles attached 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 and mixed with water supplied from the fluid supply to form a colloidal solution of constant concentration.

In addition, when using a liquid as a dispersion medium,
Microbubbles in the range of 0.06-0.2mm, more preferably
It can be used if fine bubbles of 0.1 to 0.2 mm can be dispersed at a uniform concentration. These fine bubbles can be created by setting an orifice (not shown) in which at least one small hole with a diameter of 3 mm or less, preferably 0.8 to 0.5 mm, is bored in the middle of the pipe line 12 of the fluid supply unit 2. Average 0.1 with bubbles accounting for about 70%
Microbubbles of mm size are degassed by local decompression and can be continuously and stably supplied in large quantities.

In the case of the above-mentioned gas colloid, the scattering medium 4 is quantitatively supplied to the fluid supply unit 2 using a metering injection device, and mixed with air supplied from a fluid supply source to form a constant concentration, or Alternatively, the air is mixed and stirred with the scattering medium 4 in advance, and the mixture is supplied to the model tank 1 at a constant concentration.

In such a visualization device, a colloidal fluid in which a large amount of visualization medium is uniformly dispersed to the extent that a collection of scattered light can be formed is used alone, or a colloidal fluid and a fluid containing no visualization medium are used in combination, Once a desired flow field is formed, by irradiating it with slit light, the flow field is instantaneously visualized as bright and dark light consisting of a collection of scattered lights due to scattering that occurs in the visualization medium.
Visualization of this flow field is obtained as a distribution image of scattered light intensity due to the difference in the intensity of scattered light per unit area, which is proportional to the aggregation/dispersion of the visualization medium caused by flow turbulence, diffusion, etc.

Here, in order to realize the three-dimensional visualization of the flow according to the present invention, a light source and an imaging means that instantaneously move and intermittently illuminate the flow field to be visualized are required. Examples of such a light source and imaging means include those having the arrangement shown in A or B in FIG. 4, for example. At this time, the flow field can be visualized instantaneously and sequentially through cross-sections at arbitrary positions of the flow using local illumination such as slit light. The slit light 5 can be easily obtained by a known slit light source 3 or by expanding it using a two-dimensional optical system. Furthermore, by oscillating the laser beam as it is at high speed, it is also possible to obtain a substantial slit beam. In order to instantaneously emit this slit light 5, an instantaneous shutter device 14 is installed immediately before each light source 3. Instant shutter device 1
4 is possible with a mechanical shutter, but it is most preferable to use an electric shutter with no inertia in order to facilitate synchronization with instantaneous lighting. Of course, the shutter devices 14 are provided so as to operate in sequence in conjunction with each other to create a state in which the illumination light flashes and moves instantaneously within the flow field. Note that instead of using the shutter device 14, it is also possible to employ a high-speed repetition light source such as a ruby pulse laser or a Xe flash.

On the other hand, as the means 15 for continuously recording the flow field visualized by the scattering of the instantaneous illumination light, it is preferable to use a high-speed photographic camera, an industrial TV camera, or the like. Among them, the use of high-speed photography cameras that have a shooting speed of 3000 frames per second is
Also, compared to ITV cameras, which have a limit of 60 frames per second, they are highly effective in recording fluctuations in flow fields.

The above-mentioned light source 3 and photographing means 15 are installed in such an angular relationship because optimal scattered light is obtained when their optical axes intersect within a range of approximately 90 to 145 degrees. For example, as shown in FIG. 4A, when the instantaneous illumination light moves circumferentially around the flow field, a plurality of light sources 3a to 3e are used.
and photographing means 15a to 15e corresponding to these, respectively.
and are arranged on the circumference. In addition, as shown in FIG. 4B, when the light sources 3a to 3e are arranged in a straight line and the instantaneous illumination light 5 is instantaneously moved in a straight line in the depth direction or the front direction of the model tank 1, it is possible to The device 15 can be made to record the flow conditions of different sections continuously.

A method for three-dimensionally visualizing a flow according to the present invention using the visualization device configured as described above will be explained in detail by taking a burner model as an example.

First, a fluid in which a large amount of homogeneous scattering medium 4 is uniformly dispersed is stably supplied as necessary to the model tank 1 or infinite space, and is blown out from the injection port 7 at the bottom of the tank to create a flow field. The fluid containing the scattering medium 4 forms a flow field and the total amount is adjusted in advance to a concentration suitable for visualization, or the fluid is mixed and adjusted during pumping in the fluid supply unit 2. Next, this flow field is sequentially irradiated with instantaneously flashing slit light 5 from different locations or directions with a certain directionality or relationship, and each instantaneous illumination light 5 is diffusely reflected by the scattering medium 4. The flow in an arbitrary cross section is extracted and visualized.

The flow field visualized by the scattering of the instantaneous illumination light 5 that moves instantaneously at high speed appears to the observer's eyes only as an unreadable three-dimensional image due to the afterimage phenomenon.
When high-speed photography is performed in synchronization with the instantaneous illuminations 5a, 5b, etc., it is possible to accurately determine the flow phenomenon, flow direction, etc. from the light and dark movement of the light formed by the collection of scattered light by the scattering medium 4 in one cross section. I can do it.
Moreover, the intensity of light scattered by a sufficiently fine and homogeneous scattering medium 4 is considered to be proportional to the number of scattering media in a unit volume, that is, the number density of scattering media, and this means that the intensity of the scattered light constitutes a flow field. This means that it corresponds to the volume concentration (hereinafter simply referred to as concentration) when two fluids (a colloidal fluid and a fluid that does not contain a scattering medium) are mixed, so it depends on the intensity of scattered light due to the density of the scattering medium 4. The concentration and concentration distribution can also be visually observed at the same time.

In addition, the concentration of the flow field has a similar relationship with the brightness of the scattered light, and as the proportion of the fluid that does not contain the scattering medium 4 increases in two fluids in a mixed state, the amount of scattering medium in a unit volume decreases and the brightness increases. Therefore, the brightness at the outlet of burner model 8 can be quantitatively determined as the standard brightness (equivalent to 100% concentration). Moreover, since the concentration of the fluid in different sections of the flow field is instantly visualized and recorded by the high-speed camera 15, the instantaneous concentration distribution in the entire flow field can be analyzed three-dimensionally and quantitatively as a highly approximated one. .

Furthermore, by repeating this high-speed imaging, the movement of the four groups of scattering media in the same section of the flow field,
By comparing the images of each frame, diffusion and aggregation phenomena, that is, density variations, can be known as variations in brightness. Furthermore, since this density fluctuation appears as a density change with extremely similar waveforms at extremely close points, it is possible to change the direction of instantaneous illumination light movement (three-dimensional direction) between two extremely close points within the same section or between two extremely close sections. The velocity of the flow can be measured in two or three dimensions by determining the time lag in fluctuations until a very similar waveform density change is observed between two points from the film frame advance time.

Of course, the above-mentioned concentration measurement etc. can also be carried out by utilizing changes in the brightness of a television image displayed using an industrial TV camera. In this case, real-time image processing can be realized by continuously detecting changes in brightness, that is, changes in density, using a photo sensor on a monitor television. However, since it can only obtain images at 30 to 60 frames per second, it can only be applied to low-velocity fluids.

(Effects of the Invention) As is clear from the above description, the method for three-dimensional visualization of a flow according to the present invention enables scattering media consisting of fine particles or bubbles to be dispersed uniformly in large quantities to the extent that a collection of scattered light can be formed. A flow field to be visualized is formed using colloidal fluid, and this flow field is intermittently illuminated with a slit light beam that moves instantaneously to detect the flow at different cross sections of the flow field, and to detect scattering caused by diffused reflection of the scattering medium. While the brightness and darkness of the light consisting of a collection of lights are visualized sequentially in an instant, this is sequentially imaged and captured as image data of the flow in different cross sections of the flow field, so it is possible to visualize the state of the flow and the flow in a certain cross section. In addition to qualitative observation such as direction, concentration distribution and fluctuations can be observed at a glance from the strength and weakness of scattered light, and by assembling the visible cross sections, instantaneous concentration over the entire three-dimensional flow field can be observed. Qualitative observation and quantitative measurement of distribution or concentration fluctuations, etc., becomes possible.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the visualization principle of a flow field reproduced using a colloidal fluid in which a large amount of visualization medium is uniformly dispersed. Figure 2 shows the relationship between the model tank, light source, and imaging device viewed from above. Figure 3 is a diagram explaining the principle showing an example of a visualized flow field, Figure 4 is a diagram showing an example of the flow visualization method of the present invention, and A is a case where instantaneous illumination light is rotated. , B are schematic diagrams showing the case where instantaneous illumination light is moved in a straight line. 4...Scattering medium, 3...Light source, 5...Momentary illumination, 14...Shutter device, 15...Photographing device.

Claims (1)

[Claims] 1 A flow field to be visualized is formed using a colloidal fluid in which a scattering medium consisting of fine particles or bubbles is uniformly dispersed in large quantities to form a collection of scattered light, and a slit is used to instantaneously move this flow field. Intermittent instantaneous illumination with light is used to instantaneously and sequentially visualize the flow in different cross sections of the flow field as brightness and darkness of light consisting of a collection of scattered light caused by diffused reflection of the scattering medium, and this is sequentially imaged. A method for three-dimensional visualization of a flow, characterized in that image data of the flow in different cross sections of the flow field is captured.