JPS60243536A - Three-dimensional visualizing method of flow - Google Patents

Abstract

PURPOSE:To make it possible to perform three-dimensional analysis, by lighting the flow field of liquid, in which a tracer is dispersed with a uniform concentration, instantaneously, and photographying the scattered light from the tracer. CONSTITUTION:A homogeneous tracer 4 is jetted into a model tank 1 through a jetting port 7, and a flow field is formed. Slit light 5 is instantaneously and also continuously projected with constant relationship from the different places or directions into the flow field. The flow is selectively picked up and visualized by the scattered light from the tracer 4. In synchronization with the instantaneous projection of the slit light 5, high speed photographing is performed. Then the movement of the tracer 4 can be tracked. The phenomenon and the direction of the flow can be accurately observed. The intensity of the scattered light from the tracer 4 is proportional to the concentration of the tracer. The concentration is quantitatively obtained, with the brightness at the outlet of a burner 8 being reference brightness. The high speed photographing is repeated. The change in concentration of the tracer 4 in the same section of the flow field is compared by using the frames of the pictures. Thus the change in brightness can be observed. The time delay of the change in concentration is computed from the frame feeding time of the film. Thus the three-dimensional visualization can be implemented.

Description

[Detailed Description of the Invention] 1. Background of the Invention (Field of Industrial Application) The present invention is one of the methods for three-dimensional analysis of flow behavior, which quantitatively visualizes the flow in three dimensions. Regarding how to.

Visualizing the flow is the most common means of observing flow behavior. Originally, this visualization of flow was mostly limited to qualitative observation, mainly focusing on flow conditions and flow direction, including flow separation and generation of vortices, but recently, Although it is not yet possible to expect sufficient accuracy, it is becoming possible to measure the initial quantity.

For example, from tracer trails obtained using intermittent light,
Alternatively, it has become possible to easily determine the flow velocity distribution of any flow field from a timeline using an electrical control method that can electrically control the generation of the i-laser.

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

■3 Purpose of the Invention The present invention provides qualitative,
The purpose of this invention is to provide a three-dimensional flow visualization method that can instantaneously achieve three-dimensional visualization of flows while allowing quantitative observation.

■1 Structure of the invention (Summary of the invention) In order to achieve the above object, the method for three-dimensional flow visualization of the present invention creates a flow field using a fluid in which tracers made of fine particles or bubbles are dispersed at a uniform concentration. At the same time, different parts of the flow field are continuously illuminated with planar instantaneous illumination light that moves instantaneously through this flow field, and the instantaneous flow field is visualized by scattering of the instantaneous illumination light by the tracer. It is designed to continuously photograph cross sections at high speed to form a three-dimensional visible image.

(Detailed Description of the Invention) Hereinafter, the configuration of the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 schematically shows an example of an experimental apparatus for carrying out the method of the present invention for measuring the flow velocity in three-dimensional directions of a flow field. This experimental device includes a model tank 1 that reproduces a flow field, a fluid supply unit 2 that supplies fluid in which tracer 4 is dispersed at a uniform concentration to the model tank 1, for example, from the bottom, and a fluid supply unit 2 that reproduces the flow field in the model tank 1. It mainly consists of a slit light source 3 that instantaneously irradiates planar light 5. In this visualization device, fluid that flows in from the bottom of the model tank 1 reproduces a flow field within 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 normally discharged as is or after any necessary treatment. Note that 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.

In the case of this embodiment, the model tank 1 is formed of a translucent material such as acrylic resin or glass into a predetermined shape as shown in FIG. 2, and has an exhaust port 6 above it and an injection lower 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, a stationary space is obtained by using a laboratory rest area as the flow field instead of the model tank 1.

A model that reproduces the flow field to be observed is generally attached to the injection lower at the bottom of the model tank. However, there are cases where the model is placed in the model tank 1 away from the injection lower, and no change is made to the fluid flow in the injection lower. In the case of this embodiment, 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. The burner tile model 9 is provided so as to mix the two in the burner tile model 9 by injecting a fluid containing no tracer (corresponding to secondary air) from around it. In the case of the embodiment shown in FIG. 4 (A>), a plurality of light sources 3 are arranged in a circle around the model tank 1 to allow instantaneous light 5 to enter from all directions, so the model tank 1 is The entire peripheral wall is made of a material that transmits visible light.However, the entire peripheral wall of the model tank 1 does not need to be made of a transparent material, and it is sufficient that at least the observation window 10 and the entrance window 11 are transparent. For example, the incident direction of the slit light 5 and 90 to 14
Since the optimum diffused reflection can be obtained at a position of an angle θ of 5 degrees, it is sufficient to position the observation window 10 and the entrance window within that range. When using a transparent material, it is sufficient that at least two adjacent materials are made of 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.

Fluid supply unit 2 that supplies fluid to the aforementioned model tank 1
is generated by providing a tracer injection part 13 in the middle of the pipe line 12 connecting the fluid supply source (not shown) and the model tank 1, and forcibly injecting the tracer 4 quantitatively into the fluid being pumped. By doing so, the fluid is supplied at a constant temperature of a degree. Of course, the supply unit 2 is not limited to the one described above. For example, a fluid adjusted in advance to a concentration suitable for visualization may be stored in a tank and taken out with a metering pump and pumped into the model tank 1.

The fluid that forms the flow field is a gas or liquid in which tracers 4 made of fine particles or bubbles are dispersed at a uniform concentration, and it is possible to do so as long as it does not affect the formation of the flow field. The concentration is maintained such that the tracer 4 is present densely and uniformly.

The most common dispersion medium is air when a gas is used, and water when a liquid is used; however, the dispersion medium is not limited to this, and other materials may be used as necessary. Gas may also be used.

Further, as the dispersed phase, that is, the tracer 4, it is preferable to employ fine particles such as colloidal particles or fine bubbles. When using gas as a dispersion medium, 1 Herasa 4 is 1,
M(l O
, Si 2 O, Al 2 O 3 and the like are suitable.

This is because fine particles made of fine ceramics are easy to handle and it is easy to obtain a gas colloid with a constant concentration.

Of course, gas colloids using fog or smoke as tracers can also be used if they are sufficiently homogenized.

Further, when a liquid is used as the dispersion medium, the tracer 4 is preferably made of the above-mentioned fine ceramics, milk, etc. containing extremely fine milk fat balls. In particular, milk is one of the most preferred tracer particles because it is easily available, inexpensive, easy to handle, and provides high-intensity scattered light. Among them, processed milk generally has milk fat balls with a diameter of 2 μm or less (41.8% less than 1 μm, 1 to 2 μm).
m47.7%), it is suitable for forming colloids in liquids. Therefore, in the case of this example, 0.2% by weight of processed milk is included in water to form parent tree colloid.

Note that when fine ceramic particles are used, unlike milk, they cannot immediately form a colloidal state just by pouring them directly into a stream. Therefore, we prepared what could be called a highly concentrated colloidal solution by soaking fine ceramics in a small amount of water in advance. This highly concentrated colloidal solution is made, for example, 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 source to form a colloidal solution of a constant concentration.

In addition, when using a liquid as a dispersion medium, 0.06
- Q, microbubbles in the range of 2n+m, more preferably 0.
Distribute fine bubbles of 1 to 0.2111 m at a uniform concentration 1
If q, it can be used. These fine bubbles can be produced by setting an oriswiss (not shown) in the middle of the pipe line 12 of the fluid supply unit 2 with at least one small hole of 3 mm or less in diameter, preferably 0.8 to 5 mm. , 2m
Average size: 0.1 m+++, with around 70% of bubbles smaller than m
The microbubbles are degassed by localized pressure reduction, allowing for a continuous and stable supply of large quantities.

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

The flow field is provided in such a way that any position of the flow can be visualized instantaneously and sequentially in one plane using local illumination represented by slit light. The slit light 5 is easily converted to 1q by expanding it with a known slit light source 3 or using a two-dimensional optical system. Further, by oscillating the laser beam as it is at high speed, it is possible to generate 1q as a substantial slit light.

In order to instantaneously emit this slit light 5, each light source 3
A momentary shank device 14 is installed immediately in front of the shank. Although a mechanical shutter can be used as the instantaneous shutter device 14, it is most preferable to use an electric shutter without inertia in order to facilitate synchronization with development. Of course, each shutter device 14 is arranged to operate in sequence in conjunction with each other to create a condition 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 scattering of the instantaneous illumination light, it is preferable to use a high-speed photographic camera, an industrial TV camera, or the like. In particular, the use of high-speed photography cameras that can capture images at a speed of 3000 frames/second has a significant impact when recording fluctuations in the flow field, compared to ITV cameras that have a limit of 30 or 60 frames/second. be effective.

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 in the range of approximately 90 to 1454 degrees. For example, as shown in FIG. 4(A), when the instantaneous illumination light moves circumferentially around the flow field,
A plurality of light sources 38 to 3e and corresponding photographing means 15a to 15e are arranged on the circumference. Also,
As shown in FIG. 4(B), when the light sources 3a to 3f 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, one shooting 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 using a burner model as an example.

First, a fluid in which a homogeneous tracer 4 is densely dispersed is stably supplied as necessary to the model tank 1 or infinite space, and is blown out from the injection lower at the bottom of the tank to create a flow field. The fluid containing the tracer 4 forms a flow field and is either pre-adjusted to a concentration suitable for visualization, or mixed and adjusted during pressure feeding in the fluid supply unit 2. Next, the flow field is sequentially irradiated with slit light 5 that momentarily flashes from different locations or directions with a certain directionality or relationship, and each momentary illumination light 5 is diffusely reflected on the tracer 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 moving instantaneously at high speed appears to the observer's eyes only as an unreadable three-dimensional image even with the reduction of afterimages, but the instantaneous illumination light 5a, 5b,
If high-speed photography is performed in synchronization with ..., the movement of the tracer 4 in one cross section can be tracked, so that the appearance of the flow, the flow direction, etc. can be accurately known. Furthermore, the intensity of light scattered by a sufficiently fine and homogeneous tracer 4 is considered to be 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 density and 111 degree distribution can be visually observed at the same time depending on the intensity of the scattered light associated with the density of 4.

In addition, the concentration has a similar relationship with the brightness of the scattered light, and as the proportion of the fluid that does not contain tracer 4 increases in two fluids in a mixed state, the amount of toner in the unit volume increases. From this, the brightness at the exit of the 5-burner model 8 can be quantitatively determined as a reference interval of 11 degrees (equivalent to 100%). 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 an extremely approximate one. .

Furthermore, by repeating this high-speed imaging, the four groups of tracers move in the same section of the flow field.

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

Of course, the above-mentioned concentration measurement and the like can also be carried out by using 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 photosensor on a monitor television.

However, since images can only be obtained at 3 to 60 frames per second, this method can only be applied to low-velocity fluids.

■0 Effects of the Invention As is clear from the above explanation, the method for three-dimensional flow visualization of the present invention is capable of forming a flow field using a fluid in which tracers made of fine particles or microbubbles are dispersed at a uniform concentration. , a planar instantaneous illumination light that moves instantaneously across this flow field is used to continuously instantaneously illuminate different parts of the flow field, and the instantaneous cross sections of the flow field visualized by scattering of the instantaneous illumination light due to the tracer are continuously visualized. Since the system uses high-speed photography to form a three-dimensional visible image, it is possible to not only qualitatively observe the state and direction of the flow reflected in the cross section, but also to observe I! from the strength and weakness of scattered light. The degree distribution and fluctuations can be observed at a glance, and by assembling the visible cross sections, it becomes possible to qualitatively observe and quantitatively measure the instantaneous concentration distribution or 11 degree fluctuations over the entire three-dimensional flow field.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a visualization device that implements the flow visualization method of the present invention, Figure 2 is a cross-sectional plan view showing the principle of the relationship between a model tank, a light source, and a photographing device, and Figure 3 is a visualized diagram. An explanatory diagram showing a flow field, FIG. 4 shows a specific example of implementing the flow visualization method of the present invention. It is an explanatory view showing a case of linear movement. 4...Tracer, 3...Light source, 5...Momentary illumination,
14... Shitotsuta device, 15... Photographing device. @Inventor Toshio Abe [Phase] Inventor Nobu Hisamatsu 2-11-1 Iwatokita, Komae City, Energy Research Institute, Central Research Institute of Electric Power Industry

Claims (1)

[Claims] A flow field is formed using a fluid in which tracers consisting of microscopic particles or microbubbles are dispersed at a uniform concentration, while a planar instantaneous illumination light that moves instantaneously through this flow field is used to continuously illuminate different parts of the flow field instantaneously. A method for three-dimensional visualization of a flow, comprising: illuminating the flow field and continuously photographing instantaneous cross-sections of the flow field visualized by the scattering of the instantaneous illumination light by the tracer at high speed to form a three-dimensional visible image.