JPS6145187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a device for photographing a trajectory of fine particles in a velocity measurement method using a trajectory.

When observing a flow field in a model experiment, etc., fine particles (e.g. mica, Cairo ash, baby powder) are suspended and illuminated with light from a light source (incandescent bulb, mercury lamp, laser, etc.), and the exposure time T is set appropriately. A method is used in which the velocity V (=L/T) of each particle is measured from the trajectory length L of each particle by photographing the trajectory of each particle.

FIG. 1 shows the arrangement of a measuring device that uses a laser as illumination light among the devices for experimenting with this measuring method.

That is, the illumination light 02 is emitted from the laser beam 01, the light is expanded into a planar shape by the lens 03, the flow field 04 of the measurement cross section is irradiated with the laser light, and the camera 0
5 to photograph the trajectory of particles downstream from model 06.

In this device, the light intensity of the irradiated light is almost constant within the exposure time for photographing, so it is impossible to distinguish between the starting point and the ending point of the photographed particle trajectory. Therefore, although the velocity can be measured, it is not possible to determine whether the flow direction is positive or negative.

In particular, in a turbulent flow field, changes in the flow direction are irregular, making it difficult to estimate by theory or experience.

The present invention eliminates the above-mentioned drawbacks, and uses a light source and a camera to suspend particles in a fluid flow field, illuminate them with light, and photograph them to measure the velocity of a trail. In the trajectory measuring device that performs
The invention is characterized in that it is equipped with a pair of shutters that apply the two lights located between the same light source and the fluid flow field to the fluid flow field at different times. To provide a trajectory measuring device that changes the wavelength of light applied to particles and changes the wavelength while the camera is taking pictures, thereby making it possible to distinguish between the starting point and the ending point of the flow of particles.

That is, in the present invention, since the light emitted from the light source is two lights with different wavelengths, the color of the fine particles changes when irradiated with each light.
Therefore, a pair of shutters was placed between the light source and the fluid flow field, and the two lights were applied at different times, so that the color of the particles photographed by the camera changed, and the color The starting and ending points of particles that moved within the imaging time can be determined from changes in the flow rate, and not only the speed of the flow but also its direction can be measured.

The present invention will now be described with reference to an embodiment of the apparatus shown in FIG.

Reference numerals 1 and 2 are light sources, where light source 1 is a helium neon laser that emits red light, and light source 2 is an argon laser that emits green light. Shutters 3 and 4 are arranged in front of the light source 1 and between the flow field 10, and use Pockels cells that utilize the Pockels effect. Reference numeral 5 denotes a pulse oscillator that generates a single rectangular pulse voltage for operating the shutters 3 and 4, and the length of the rectangle can be made variable. The pulses oscillated from the oscillator 5 directly enter the shutter 3, and the pulses enter the shutter 4 through a delay circuit 6 with a rectangular phase shift, and the rectangular pulses cause the shutters 3 and 4 to open and close.

7 is a half mirror, 8 is a plane mirror, the light from the light source 1 that has passed through the shutter 3 passes through the half mirror 7, and the light from the light source 2 that has passed through the shutter 4 is reflected by the plane mirror 8 and the half mirror 7; Each of the beams is expanded into a planar shape by a cylindrical lens 9 and irradiated onto a flow field 10 . Note that 12 is a camera for photographing.

The helium neon laser generated by the light source 1 is a laser beam with a wavelength of 0.6328 μm, and when a single rectangular pulse voltage generated by the pulse oscillator 5 is applied to the shutter 3, the shutter 3 opens and the rectangular It passes only during the pulse width T seconds of the pulse voltage. The laser beam that has passed through the shutter 3 becomes flat illumination light by the cylindrical lens 9.
A group of particles floating in the flow field 10 to be measured is illuminated. On the other hand, the argon laser generated by the light source 2 is a laser beam with a wavelength of 0.488 μm, and when the single rectangular pulse voltage generated by the pulse oscillator 5 is applied to the shutter 4 via the delay circuit 6,
The shutter 4 is opened and the rectangular pulse voltage passes for a pulse width T seconds. The laser beam that has passed through the shutter 4 is transferred to a plane mirror 8 and a half mirror 7.
The light is guided to the cylindrical lens 9 and becomes plane illumination light, which illuminates a group of particles floating in the flow field to be measured.

Note that the delay time of the delay circuit 6 is set to the same value as the pulse width T seconds of the rectangular pulse voltage.

In this way, the camera 12 loaded with color film can detect two colors of light reflected from the particles in the flow field 10, that is, the laser light generated by the light source 1 and the laser light generated by the light source 2. Double photography of reflected light within the same exposure time.

Then, as shown in Fig. 3, the trajectory of each particle constituting the particle group moving for twice the pulse width T seconds of the rectangular pulse, that is, 2T seconds, has two colors of red and green at the starting point and ending point, as shown in Figure 3. The images are color-coded and photographed.

In other words, in this example, two light sources that emit laser beams with different colors in the laser illumination light, that is, different wavelengths, were provided, and the irradiation times were staggered to take photographs, so the colors of the starting and ending points of the photographed particles were Since the flow rates are different and identified, velocity and direction of flow can be measured simultaneously.

Therefore, it is now possible to simultaneously measure velocity and flow direction, especially in turbulent areas such as the wake of an object or in flow fields where the direction of flow fluctuates significantly, which was impossible with conventional techniques. is extremely effective in flow analysis.

Next, another embodiment of the present invention is shown in FIG. In this embodiment, the light emitted from one light source is separated into two lights with different wavelengths using a prism.

30 is a light source with wavelengths of 0.6764, 0.6471,
A krypton laser with multiple oscillation lines such as 0.5309 and 0.4762 μm is used.

A prism 31 has the function of separating the laser light generated by the light source 30 as a spectrum, that is, separating it into monochromatic light components and arranging them in order of wavelength. Note that two spectra are shown in FIG. 4 for simplicity. The separated laser beams are reflected by plane mirrors 32 to 35, respectively, and enter apertures 38 and 39 having holes through which only the separated light passes, and reach shutters 3 and 4.

It should be noted that those designated by reference numerals 3 to 10 and 12 have the same structure and function as those shown in FIG. 2, and the explanation thereof will be omitted.

In FIG. 4, the laser beams generated by the light source 30 have wavelengths of 0.6764, 0.6471, 0.5309, and 0.4762 μm.
The laser light is a composite light of monochromatic laser light such as, and the laser light is guided to a prism 31, and is separated in descending order of wavelength by the spectroscopic action of the prism 31. Among the laser beams separated into monochromatic laser beams by the prism 31, for example, light with a wavelength of 0.5309 μm (green) and light with a wavelength of 0.4762 μm (blue) are reflected by plane mirrors 32 and 33 and plane mirrors 34 and 35, respectively. , shutters 3 and 4 via apertures 38 and 39
Put it in. The subsequent operations are the same as in the first embodiment.

The only difference from the first embodiment is that the particles captured on the color film of the camera 12 are separated into green and blue, but the same effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional trajectory measuring device, Fig. 2 is an explanatory diagram of an apparatus showing an embodiment of the present invention, Fig. 3 is a diagram showing photographed particles, and Fig. 4 is an explanatory diagram of a device showing an embodiment of the present invention. It is an explanatory view showing another example. 1, 2: light source, 3, 4: shutter, 5: pulse oscillator, 6: delay circuit, 10: flow field, 12: camera.

Claims (1)

[Claims] 1. In a trajectory measurement device that has a light source and a camera and measures the velocity of a trajectory by suspending particles in a fluid flow field and photographing them by shining light on them, It is characterized by comprising a pair of shutters in which the light is two lights of different wavelengths, and the two lights located between the same light source and the fluid flow field are applied to the fluid flow field at different times. Path measurement device.