JP7185269B2 - Fluid control system - Google Patents

Description

The present invention relates to a flow velocity measuring device, a flow velocity distribution measuring system, a fluid control system, and a flow velocity measuring method.

Scattered light is generated when minute particles flowing in a fluid such as gas or liquid pass through an interference fringe formed in an area where two laser beams intersect. The frequency of this scattered light is shifted with respect to the frequency of the original laser light due to the Doppler effect of light. It is known that the displacement of the frequency is proportional to the passage speed of the particles. Acquired using a board, the velocity of the particles can be estimated.
This is the principle of velocity measurement using a laser Doppler velocimetry (LDV). Since LDV is a method that uses light, it is a measurement method with high time resolution and has the feature of not requiring absolute calibration. In addition, it is a non-invasive (non-contact) measurement method because the speed can be obtained by irradiating only light without inserting a sensor or the like into the flow path or air path to be measured.
Based on the above characteristics, LDV can be used from large-scale flow fields around transportation equipment such as automobiles and railways to biochemical analysis systems such as micro-total analysis systems (μTAS) and lab-on-a-chip. This is one of the typical velocity measurement methods used for velocity measurement in a wide range of scale flow fields, including microscale flow fields within a chip.

Usually, many LDV devices are composed of two probes: an irradiation probe for irradiating a flow channel with laser light, and a probe incorporating a light-receiving element for receiving scattered light. In addition, a device has been developed in which a light-receiving element is incorporated in an irradiation probe, and a single probe performs from laser light irradiation to data acquisition.

On the other hand, LDV is a method of measuring velocity only in the area where two laser beams intersect (point measurement), so the amount of information that can be obtained regarding the flow field is small.
In the flow field to be measured, it is necessary to mechanically scan (traverse) the device in order to obtain velocity distributions such as velocity in the flow direction, height direction, and depth direction.
Also, the two laser beams are condensed by a lens attached to the laser irradiation port of the irradiation probe and intersect. Therefore, this crossing position is also determined by the focal length of the lens, and depending on the device, the distance (working distance) from the irradiation port to the crossing position becomes very large.
Furthermore, depending on the measurement target, it is necessary to consider the traverse amount and working distance of the device itself, which limits the degree of freedom in the installation space of the device. There was a problem of putting it away.

Techniques capable of obtaining velocity distribution in the depth direction in a flow field by LDV without traversing the probe in the depth direction are disclosed in Non-Patent Document 1 and Non-Patent Document 2, for example.

"Monochromatic heterodyne fiber-optic profile sensor for spatially resolved velocity measurements with frequency division multiplexing", Applied Optics, 44(13), pp. 2501-2510, 2005. "Axial scanning laser Doppler velocimeter using wavelength change without moving mechanism in sensor probe", Optics Express, 19(7), pp. 5960-5969, 2011.

In these documents, it is necessary to use a plurality of devices such as very expensive acousto-optic devices, and to appropriately adjust the frequencies and passage positions of a plurality of laser beams (Non-Patent Document 1), and to use a plurality of diffraction devices. It is described that the optical system must be strictly adjusted in order to selectively cross appropriate light among the diffracted lights generated from the grating (Non-Patent Document 2).
Therefore, not only must a special device be used, but also a very skilled technique is required to adjust the position of the laser beam, and it is difficult to say that anyone can easily handle the device and technique.

In view of the circumstances as described above, an object of the present invention is to provide a flow velocity measurement system that has a simple configuration, is easy to handle, and can acquire the velocity distribution in the depth direction in a flow field without traversing the probe in the depth direction. An object of the present invention is to provide an apparatus, a flow velocity distribution measuring system, a fluid control system, and a flow velocity measuring method.

In order to achieve the above object, a flow velocity measuring device according to one aspect of the present invention includes an emission section that emits two laser beams, and a focal length that can be changed to obtain two laser beams emitted from the emission section. an intersecting varifocal lens system, and an observation unit for observing scattered light generated when particles flowing in the fluid to be measured pass through the interference fringes formed in the region where the two laser beams intersect. have

A flow velocity distribution measurement system according to one embodiment of the present invention is a flow velocity distribution measurement system that measures the flow velocity distribution of a fluid near a wall. This system is configured by embedding the flow rate measuring device having the above configuration in the wall so that the area where the two laser beams emitted from the emitting portion intersect is located near the wall.

A fluid control system according to one aspect of the present invention includes an influence imparting section, the flow velocity measuring device configured as described above, and a control section. The influence applying section influences the flow of the fluid flowing in the vicinity of the wall. The flow velocity measuring device is configured to be embedded in the wall around the influencing section so that a region where two laser beams emitted from the emitting section intersect is positioned near the wall. The control unit controls the influence of the influence imparting unit on the flow of the fluid based on the flow velocity of the fluid measured by the flow velocity measuring device.

A flow velocity measuring method according to an embodiment of the present invention emits two laser beams, intersects the emitted two laser beams through a variable focus lens system capable of changing the focal length, and measures the Scattered light generated when particles in the fluid pass through the interference fringes formed in the area where the two laser beams intersect is observed.

According to the present invention, the velocity distribution in the depth direction in the flow field can be obtained with a simple configuration, easy handling, and without traversing the probe in the depth direction.

1 is a block diagram showing a schematic configuration of a flow velocity measuring device 1 according to one embodiment of the present invention; FIG. 3 is a diagram showing an example of specific configurations of an emission section 10, a variable focus lens system 20, and an observation section 30 according to the present embodiment; FIG. 1 is a schematic perspective view for explaining the principle of a laser Doppler anemometer; FIG. 1 is a schematic front view for explaining the principle of a laser Doppler anemometer; FIG. 4A and 4B are diagrams for explaining the action of the liquid lens 21; FIG. FIG. 4 is a diagram (part 1) for explaining changes in spatial resolution with respect to changes in focal length; FIG. 2 is a diagram (2) for explaining changes in spatial resolution with respect to changes in focal length; 7 is a graph showing an example of changes in spatial resolution with respect to changes in focal length; FIG. 2 is a schematic diagram showing the configuration of a flow velocity distribution measurement system 100 according to another embodiment of the present invention; It is a graph which shows the relationship between the distance from a wall and the flow velocity. FIG. 3 is a schematic diagram showing the configuration of a fluid control system 200 according to still another embodiment of the present invention; 3 shows a schematic perspective view of a main wing 301 of an aircraft and a flap 302 deployable relative to the main wing 301. FIG. FIG. 4 is a diagram for explaining an application example of the flow velocity measuring device according to the present embodiment, and shows a state in which an exit portion and an observation portion are seen through a liquid lens 21;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

<Flow rate measuring device according to one embodiment>
FIG. 1 is a block diagram showing a schematic configuration of a flow velocity measuring device 1 according to one embodiment of the present invention. As shown in FIG. 1, the flow velocity measuring device 1 is mainly composed of a probe 2 including an emission part 10 and a variable focus lens system 20, an observation part 30, and a control part 40. It acquires the flow velocity distribution Vp of Dd. Although the probe 2 of the flow velocity measuring device 1 according to this embodiment shares the illumination probe and the light receiving probe, the present invention is not limited to this, and the illumination probe and the light receiving probe may be separate.
The emitting unit 10 emits two parallel laser beams L1 and L2 at a predetermined interval in a direction orthogonal to the depth direction Dd. The two laser beams L1 and L2 are typically the same light source and have the same frequency and phase.

The varifocal lens system 20 can change the focal length f, and causes the two laser beams L1 and L2 emitted from the emitting section 10 to intersect at the focal length f. The variable focus lens system 20 is also called a varifocal lens, and is typically a liquid lens whose focal length can be controlled by voltage control. Note that the varifocal lens system 20 according to the present embodiment may be an optical system other than a liquid lens as long as it can change the focal length f. For example, the varifocal lens system 20 may be an optical system in which a plurality of lenses are configured and part of which is moved along the optical axis to continuously change the focal length.
The observation unit 30 observes a particle P in the fluid to be measured, typically a particle, when it passes through the interference fringes formed in the area where the two laser beams L1 and L2 intersect, that is, the area of the focal length f. , through the variable focus lens system 20.
The controller 40 functions as a calculator and estimates the flow velocity of the fluid based on the frequency of the scattered light Ls observed by the observer 30 . Also, the control unit 40 controls operations of the output unit 10 , the varifocal lens system 20 , and the observation unit 30 . For example, the control unit 40 controls the emission unit 10 to emit the laser beams L1 and L2, electrically controls the varifocal lens system 20 to control the focal length of the varifocal lens system 20, and controls the focal length of the varifocal lens system 20. 30 is controlled to receive the scattered light Ls. The control unit 40 can typically be configured by a PC (personal computer).

FIG. 2 is a diagram showing an example of specific configurations of the output section 10, the varifocal lens system 20, and the observation section 30 according to this embodiment. Note that the flow velocity measuring device 1 according to this embodiment is not limited to this configuration.
In FIG. 2, reference numeral 11 denotes a laser light source such as a semiconductor laser, reference numeral 12 denotes a beam splitter that splits the laser light L from the laser light source 11, and reference numeral 13 denotes a prism that reflects one of the laser light L2 split by the beam splitter 12. is. A mirror may be used instead of the prism. The emitting unit 10 is composed of the laser light source 11, the beam splitter 12, and the prism 13, and splits the laser light L emitted from the laser light source 11 into two laser lights L1 and L2 via the beam splitter 12 and the prism 13. diverge and exit. The frequency of the laser light emitted by the laser light source 11 is not particularly limited.
Reference numeral 21 denotes a liquid lens, and in the flow velocity measuring device 1 according to this embodiment, the variable focus lens system 20 is configured with this liquid lens 21 . The focal length f of the liquid lens 21 is controlled by voltage control using the controller 40 (see FIG. 1) as described above.
Reference numeral 31 denotes a condensing lens for condensing the scattered light Ls through the liquid lens 21; 32, an optical fiber having a light receiving port located at the focal position of the liquid lens 21; A photodetector that receives light. In the flow velocity measuring device 1 according to this embodiment, the observation section 30 is composed of at least the condenser lens 31 , the optical fiber 32 and the photodetector 33 .

The flow velocity measuring device 1 configured in this manner functions as a laser Doppler velocimetry (LDV: Laser Doppler Velocimetry). The principle of this laser Doppler anemometer will be briefly described with reference to FIGS. 3A and 3B.
As shown in FIGS. 3A and 3B, when the particles P in the flow field Ff pass through the interference fringes Fr generated by the interference of the two laser beams L1 and L2, the scattered light Ls corresponding to the brightness of the interference fringes occurs. At this time, the intensity of the scattered light Ls is caused by the Doppler effect of light. The photodetector 33 of the observation unit 30 converts the optical signal of the scattered light Ls into an electric signal, and the control unit 40 obtains the frequency when the interference fringes pass through. Since this method uses light, the signal can be obtained at the moment the light signal is emitted. Therefore, the time resolution is high.
The flow velocity U of the particles P is determined by the following equation based on the Doppler frequency _fdp and the interval d between the interference fringes Fr.
U= _fdpd
Therefore, it can be said that the flow velocity measuring device 1 according to the embodiment employing the LDV is a non-invasive (non-contact) measuring method with high temporal resolution.

Here, as shown in FIG. 4, the flow velocity measuring device 1 according to the present embodiment employs the liquid lens 21, and under the control of the control unit 40, the focal length f of the liquid lens 21 is set in the depth direction Dd. variable. For example, dotted lines in FIG. 4 indicate the laser beams L1 and L2 when the liquid lens 21 is controlled so as to increase the focal length. 4 indicate the laser beams L1 and L2 when the liquid lens 21 is controlled so as to shorten the focal length.
Since the LDV of the conventional configuration has a fixed focus, it was necessary to move the probe in the depth direction Dd in order to obtain the flow velocity in the depth direction Dd with respect to the probe. In other words, in the LDV of the conventional configuration, it is necessary to move the device itself, so there are spatial restrictions on the device. On the other hand, in the flow velocity measuring device 1 according to the present embodiment, since the LDV is configured using the liquid lens 21, the focal length can be electrically controlled, and the measurement position can be changed without moving the probe. be able to. Therefore, spatial restrictions on the depth direction Dd are reduced. Moreover, even in a place where it is difficult to move the device spatially, it is possible to acquire the flow velocity distribution Vp in the depth direction Dd without moving the device. Furthermore, the flow velocity distribution in the depth direction Dd in the flow field Ff can be instantaneously measured on the spot.

<Spatial resolution>
The flow velocity measuring device 1 according to this embodiment can change the focal length by using the liquid lens 21, but the spatial resolution changes with the change in the focal length.

As shown in FIG. 5, λ is the wavelength of the laser beams L1 and L2, δ is the interval between the laser beams L1 and L2, f is the focal length of the liquid lens 21, and f is the focal length of the laser beams L1 and L2 after passing through the liquid lens 21. Assuming that each beam diameter is D, the beam waist diameter φ, which is the intersection width of the laser beams L1 and L2 shown in FIG.
φ=4λf/πnD=4λf/πD (n is the refractive index, n=1 assuming air)
and φ corresponds to the diameter (x*y) of the measurement volume.

The crossing angle θ of the beams is
θ=tan ⁻¹ (0.5δ/f)
and the fringe space (interference fringe spacing) Δx is
Δx=λ(2nsinθ)=λ(2sinθ)
and the probe volume length (the length of the portion where the laser beams L1 and L2 intersect) l is
l=φ/sin θ
is.
The size of the probe volume l is the spatial resolution. Since the value of θ also changes as the focus changes, it can be said that the volume length l also changes according to the change in focus. Therefore, when l becomes smaller, the space can be measured more precisely, so the spatial resolution increases. Conversely, if l becomes large, the space cannot be measured very finely, so the spatial resolution decreases.

<Spatial resolution and uncertainty>
The flow velocity measuring device 1 according to this embodiment employs a configuration in which the liquid lens 21 is used to change the focal length. Therefore, for example, when performing measurement while changing the focal length f of the liquid lens 21, the smaller the value of the probe volume length l, the higher the spatial resolution in the depth direction Dd. That is, when the value of the focal length f decreases, the value of θ increases, and accordingly the value of sin θ increases, so that the volume length l of the probe decreases. That is, the spatial resolution in the depth direction Dd where the focal length f is short is high, and the flow velocity in the portion close to the probe can be obtained with high accuracy.
On the other hand, as shown in FIG. 7, the probe volume increases as the focal length f increases. That is, the resolution is degraded. At this time, since the flow velocity is uniquely determined within the probe volume at any position being measured, if the flow velocity has a distribution within the probe volume, the distribution is the uncertainty of the mean value of the flow velocity at the point being measured. is expressed as
A change in spatial resolution with respect to a change in focal length f is, as shown in FIG. 7, at most about 2% even if the focus changes by about 10 mm. Therefore, even if the liquid lens 21 is used to change the focal length as in the flow velocity measuring device 1 according to the present embodiment, the uncertainty of the measurement itself is small unless the focal length is greatly changed during the measurement. It is thought that it will not become very large. FIG. 7 is calculated assuming that the original beam diameter D=1 mm and the beam spacing .delta.=15 mm as preconditions.

Also, the fact that the spatial resolution changes according to the focal length may be positively utilized as described below.

<Flow velocity distribution measurement system according to one embodiment>
FIG. 8 is a schematic diagram showing the configuration of a flow velocity distribution measurement system 100 according to another embodiment of the invention.
As shown in FIG. 8 , the flow velocity distribution measurement system 100 measures the flow velocity distribution Vp of fluid such as gas near the wall 101 .

The flow velocity distribution measurement system 100 is configured such that the flow velocity measurement device 1 according to the above-described embodiment is configured so that the area where the two laser beams L1 and L2 emitted from the emission part 10 (see FIG. 1) intersect is located in the vicinity of the wall 101. , embedded in the wall 101. FIG.

Here, the closer the flow velocity distribution Vp is to the wall 101, the smaller the value. The uncertainty of the flow velocity near the wall 101 becomes small. That is, the width of the error bars is reduced. On the other hand, the flow velocity distribution Vp has a larger value as it moves away from the vicinity of the wall 101, but as the distance from the vicinity of the wall 101 increases, the focal length f becomes longer and l becomes larger, so the spatial resolution becomes lower. The uncertainty of the flow velocity near 101 becomes large. In other words, the width of the error bars increases. In FIG. 9, the plotted points are the flow velocities (u) at each point at a predetermined distance (z) away from the vicinity of the wall 101, and the vertical and horizontal thin lines extending from the plotted points indicate the width of the error bar. . The error bars in the vertical direction are the error bars of the measurement position associated with the size of l, and the error bars in the horizontal direction are the error bars of the flow velocity.

Moreover, in order to acquire the flow velocity distribution Vp in the vicinity of the wall 101, the conventional LDV requires a highly accurate positioning device for moving the device. In addition, there have been conventional sensors smaller in size than the value of the probe volume length l, but the sensor had to be inserted into the flow path, disturbing the flow.

On the other hand, the flow velocity distribution measurement system 100 according to the present embodiment uses a varifocal lens system, so that the flow velocity measurement device 1 is not moved, and since it is a noninvasive measurement method, the flow is not disturbed. The flow velocity distribution Vp near the wall 101 can be measured. It has been confirmed that the flow velocity distribution measuring system 100 according to the present embodiment can adjust the focal length with an accuracy of 1 mm or less.

<Fluid control system according to one embodiment>
FIG. 10 is a schematic diagram showing the configuration of a fluid control system 200 according to still another embodiment of the invention. Here, an example in which the fluid control system 200 is typically applied to an aircraft wing is shown.
In FIG. 10 , reference numeral 201 indicates a wing, which is one aspect of the wall, and reference numeral 202 indicates the upper surface of the wing 201 . Also, the left side in the figure is the leading edge side of the blade 201 .
The main part of the fluid control system 200 according to this embodiment is mounted inside the wing 201 .

The fluid control system 200 mainly includes an influence imparting section 210 that influences the flow of the fluid flowing near the blade 201 and the flow velocity measuring device 1 according to the above-described embodiment. and a synchronizer 220 for synchronizing the operations of the flow velocity measuring device 1 and a controller 230 .

Here, the influencing section 210 can be configured by, for example, a blowing device embedded in the wing 201 and blowing fluid upward from the surface of the wing 201 at high speed. Note that the influencing section 210 can be configured not only by a blowout device, but also by a protruded device such as a vortex generator, a dielectric barrier discharge plasma actuator, or the like.
The probe 2 of the flow velocity measuring device 1 is located on the rear end side of the blade 201 relative to the influence imparting section 210 so that the area where the two laser beams L1 and L2 emitted from the emission section 10 intersect is located near the blade 201. In addition, it is embedded in the wing 201 . Note that the flow velocity measuring device 1 may be embedded in the blade 201 upstream of the influence imparting section 210 instead of downstream.
The control unit 230 is configured by, for example, a PC, and controls the influence of the influence imparting unit 210 on the flow of fluid based on the flow velocity of the fluid measured by the flow velocity measuring device 1 . Synchronizer 220 and controller 230 may be located in the fuselage of the aircraft.

In the fluid control system 200 configured as described above, the velocity measurement device 1 measures in real time the scattered light generated by the particles following the flow with large velocity fluctuations on the surface of the blade 201, and the control unit 230 outputs the Doppler signal When it exceeds a certain threshold, the flow is controlled by, for example, blowing out high-speed gas from the influencing unit 210 to add momentum to the flow on the surface of the blade 201 . Thereby, large fluctuations occurring in the flow on the surface of the blade 201 can be suppressed. Then, in the system according to the present embodiment, the optical signal of the scattered light of the particles generated in the area where L1 and L2 intersect in time series is acquired, and the surface of the wing 201 is It becomes possible to control the flow above in real time. By enabling real-time control, flow separation on the surface of the blade 201 can be suppressed more accurately.

<Usage example of the flow velocity measuring device according to the present embodiment>
FIG. 11 shows a schematic perspective view of a main wing 301 of an aircraft and flaps 302 deployable relative to the main wing 301 . FIG. 11 shows the flap 302 deployed.
Numeral 300 is a single MEMS sensor module formed by arranging a plurality of the above-described flow velocity measuring device 1 itself by microfabrication (MEMS). The MEMS sensor module 300 is embedded, for example, on the front edge side of the surface of the flap 302 so as to be parallel to the front edge. This position may not be directly observable from the surroundings even when the flap 302 is stored in the main wing 301 or the flap 302 is deployed from the main wing 301 .

Typically, in an environment such as a wind tunnel test room, surrounded by walls and without a measurement window, the MEMS sensor module 300 is embedded in the flap 302 to pass between the main wing 301 and the flap 302. It is possible to obtain the velocity distribution of the airflow.

In addition, in the flow velocity measuring device 1 according to the present embodiment, it is possible to create something like an endoscope and measure the flow velocity in a portion that is out of reach of human hands through a probe.
Also, by inserting the flow velocity measuring device 1 according to the present embodiment into the combustion engine of a running automobile, it is possible to measure the state of combustion from the movement of fine particles in the combustion engine.
Furthermore, the flow velocity measuring device 1 according to the present embodiment is inserted into the human body through the skin, and is aligned with the blood vessel wall. It is possible to measure the velocity distribution of

<Application example of the flow velocity measuring device according to the present embodiment>
FIG. 12 is a diagram for explaining an application example of the flow velocity measuring device according to the present embodiment, and shows a state in which the exit part and the observation part are seen through the liquid lens 21. As shown in FIG.
A flow velocity measuring device 401 according to this application example has first and second emission sections 10a and 10b as emission sections, and first and second observation sections 30a and 30b as observation sections.
The first emitting portion 10a emits two laser beams L1 and L2, and the second emitting portion 10b forms a second straight line orthogonal to the first straight line l1 connecting the two laser beams L1 and L2. Other two laser beams L3 and L4 that intersect in the same region as the region where the two laser beams L1 and L2 intersect are emitted from above l2. The first observation unit 30a observes the scattered light originating from the two laser beams L1 and L2, and the second observation unit 30b observes the scattered light originating from the other two laser beams L3 and L4. do.

For example, the laser beams emitted from the first and second emitting portions 10a and 10b have different wavelengths, the first observation portion 30a is provided with a filter for receiving only the laser beams L1 and L2, and the second observation portion 30b is provided with a filter for receiving only the laser beams L3 and L4, so that scattered light emitted from particles passing through the interference fringes can be separately observed.

In the flow velocity measuring device 401 according to this application, the direction of the fluid flowing on the surface of the wall and the flow velocity distribution of the fluid in that direction can be measured by calculation in the control unit 40 (see FIG. 1).

<Others>
The present invention is not limited to the above embodiments, and can be modified and implemented within the scope of the technical idea, and can also be applied and implemented. Of course, the scope of these implementations also belongs to the technical scope of the present invention.

Reference Signs List 1: flow velocity measuring device 10: emission unit 11: laser light source 12: beam splitter 13: prism 20: variable focus lens system 21: liquid lens 30: observation unit 31: condenser lens 33: photodetector 40: control unit 100: flow velocity distribution Measurement system 101 : Wall 200 : Fluid control system 210 : Influencing unit 230 : Control unit 401 : Velocity measuring device D : Beam diameter Dd : Depth direction Ff : Flow field Fr : Interference fringes L : Laser beam L1 : Laser beam L2 : Laser light L3: Laser light L4: Laser light Ls: Scattered light P: Particle U: Flow velocity Vp: Flow velocity distribution f: Focal length fdp: Doppler frequency l: Probe volume l1: First straight line l2: Second straight line λ: Wavelength θ of laser beams L1 and L2: Crossing angle δ: Beam spacing φ: Beam waist diameter

Claims (6)

an influencing unit arranged at a predetermined position on an aircraft wing to influence the flow of the fluid by adding momentum to the fluid flowing on the surface of the wing;
A varifocal lens system that consists of an output unit that outputs two laser beams and a liquid lens whose focal length can be controlled by voltage control, and that intersects the two laser beams output from the output unit; an observation part for observing scattered light generated when particles flowing in a certain fluid pass through interference fringes formed in the region where the two laser beams intersect, and the light emitted from the emission part a flow velocity measuring device embedded in the wing so that the area where two laser beams intersect is located on the surface of the wing upstream or downstream from the influencing portion;
From the flow velocity measuring device, an optical signal of the scattered light of the particles generated in the area where the two laser beams intersect in time series is obtained, and based on the signal, the separation of the flow on the surface of the blade is suppressed. and a controller that controls the momentum imparted to the fluid by the influencer to control the flow on the surface of the wing in real time so as to perform: The emitting unit has a laser light source, a beam splitter that splits the laser light from the laser light source, and a prism that reflects one of the laser light split by the beam splitter, and the laser light emitted from the laser light source. is split into the two laser beams via the beam splitter and the prism and emitted. The observation unit includes a condenser lens that collects the scattered light that has passed through the varifocal lens system, and a light receiving opening that is positioned at a focal position of the condenser lens and receives the scattered light through the light receiving opening. 3. A fluid control system according to claim 1 or 2, comprising a photodetector. 4. The fluid control system according to claim 1, further comprising a computing unit that estimates the flow velocity of the fluid based on the frequency of the scattered light. an influencing unit arranged at a predetermined position of a transport device and exerting momentum on the fluid flowing on the surface of the transport device to affect the flow of the fluid;
A varifocal lens system that consists of an output unit that outputs two laser beams and a liquid lens whose focal length can be controlled by voltage control, and that intersects the two laser beams output from the output unit; an observation part for observing scattered light generated when particles flowing in a certain fluid pass through interference fringes formed in the region where the two laser beams intersect, and the light emitted from the emission part a flow velocity measuring device embedded in the transportation equipment such that the area where the two laser beams intersect is positioned on the surface of the transportation equipment upstream or downstream from the influencing part;
From the flow velocity measuring device, an optical signal of the scattered light of the particles generated in the area where the two laser beams intersect in time series is obtained, and based on the signal, the separation of the flow on the surface of the transportation device is determined. a control unit for controlling the momentum imparted to the fluid by the influencing unit to control the flow on the surface of the vehicle in real time to provide restraint;
A fluid control system comprising: The transportation equipment is an automobile or a railroad
6. The fluid control system of claim 5.

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