JPS634667B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluid flow measuring device, and more particularly to a fluid flow measuring device suitable for measuring the dynamics of underground water, etc., which exhibit minute movements.

In recent years, it has become increasingly necessary to accurately measure the flow of groundwater (flow velocity, flow direction, or both) in determining whether or not to adopt freezing construction methods and in conducting groundwater contamination investigations. Conventionally, a so-called tracer method has been widely used as a method for measuring groundwater flow. This method involves injecting salt or dye into one of multiple boreholes, examining changes in electrical resistance or concentration over time between it and other boreholes, and measuring arrival time and flow from that position. It is something to do. However, in the above-mentioned conventional technology, it is necessary to drill a large number of boreholes, and the survey cost becomes extremely high.
When the groundwater flow velocity is slow, it takes a long time to measure, and during that time, the groundwater flow changes due to rainwater, etc., making it difficult to make accurate measurements.

Recently, as an attempt to improve the shortcomings of the above-mentioned conventional technology, a propeller-type current meter has been used to measure the flow velocity and flow direction from the rotation speed and change of the propeller.
As in the invention disclosed in Japanese Patent Publication No. 45-25029, a disk is lowered into a borehole and the groundwater flow situation is estimated from the pressure difference due to the upward and downward flow of water in the hole acting on the disk. Alternatively, a method has been devised in which a radioisotope is poured into flowing water and the flow velocity and direction are measured by tracing changes in the radiation dose distribution due to the flowing water.

However, with the method of driving a mechanical measuring means with flowing water, it is extremely difficult to accurately measure the flow velocity when the flow velocity is as small as 2 cm per second or less. Not only is it dangerous to handle, but it also has drawbacks such as the equipment being extremely expensive.

The present invention has been made in view of the drawbacks of the prior art, and is capable of accurately measuring at least the flow direction of a fluid having an extremely small flow velocity at a single measurement point, and is easy to handle. The object of the present invention is to provide a simple object flow measurement device having the following configuration.

The present invention includes a pair of current electrodes in an observation portion of a probe inserted into a fluid to be measured, for measuring the movement state of a replacement substance having electrical properties different from that of the fluid to be measured, due to the flow of the fluid. A plurality of measurement electrode groups using the four-electrode method consisting of a pair of voltage electrodes for voltage detection installed in close proximity to each other are provided concentrically, and the pair of current electrodes are arranged in the circumferential direction, and the adjacent measurement electrodes are arranged in a circumferential direction. At least the current electrode is shared between the electrode groups, and further, the voltage is applied to the current electrode and the voltage is detected by the voltage electrode,
The above objective is achieved by configuring the measurement to be carried out in time division for each measurement electrode group.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 9.

FIG. 1 is a schematic explanatory diagram showing an example of actual measurement using the fluid flow measuring device according to the present invention. In the figure, 1 is the ground E
This is a measurement borehole that is drilled from the ground surface to a predetermined depth into the groundwater layer (sand layer, gravel layer, etc.). A measuring probe (hereinafter referred to as
3 (simply referred to as the "probe") is inserted down to the test depth. Here, the direction of the probe 3 is confirmed by a compass 4 built into the upper part of the probe 3 (see FIG. 2), and the probe 3 is installed and fixed in a predetermined direction. In the groundwater layer in the ground E, there is a flow of groundwater as shown by the arrow F in the figure, and as a result, groundwater W gushes out into the borehole 1 below the groundwater level, and the probe 3 is immersed in this groundwater W. will be done. The probe 3 is electrically connected to an external measuring device (not shown) through a cable 5 extending inside the boring rod 2, thereby allowing groundwater flow measurement and recording. It is beginning to be practiced.

Next, the specific configuration of the probe 3 described above will be explained in the second section.
As shown in the figure. The probe main body 3A, which is the main part of the probe 3, includes a cylindrical probe main body 6 with a compass 4 installed in the upper part, a disc-shaped head 7 attached to the lower end of the probe main body 6, and a probe main body 3A that is a main part of the probe 3. 7 and a bottom plate 8 disposed below it at a predetermined interval.

The head 7 is made of an insulating material,
On this head 7, a plurality of electrodes 71 to 94 constituting a four-electrode method as described later are protruded downward and arranged concentrically and radially as shown in FIG. The head 7 is screwed to the lower end surface of the probe body 6 at the upper ends of four pillars 20, 20, . It is designed to be installed in a sealed manner. A support plate 21 for supporting the lower end of the cable 5 is fixed to the upper surface side of the head 7 in FIG. 2, and the electrodes 71 to 94 are wired via the cable 5.

On the other hand, the bottom plate 8 has pillars 20, 20,...
is fixed to the lower end of the head 7 by nuts 22, 22, .
is formed, and groundwater can flow into this observation section 23. This bottom plate 8 has a function as a bottom of a container filled with an electrolytic solution (for example, NaCl solution) 24 as a replacement substance, as described later, and also has a function when lowering the entire probe in the borehole 1. Even if the probe 3 is pressed down by mistake on the bottom of the
94 from being damaged, and also has functions such as stabilizing the flow within the observation section 23.

Between the circumferential edge of the head 7 and the circumferential edge of the bottom plate 8, there are electrodes 71 to 71 implanted in the head 7.
A cylindrical wire mesh 25 is disposed to surround 94. This wire mesh 25 is a hole wall 1A of the borehole 1.
(See Figure 1) Due to collapse of the observation unit 23, etc.
In addition to preventing foreign matter from entering the electrodes 71 to 9,
4 parts are electrically shielded to eliminate the influence of external noise such as ground current, and as will be described later, the occurrence of turbulence that occurs when the sleeve 30 rises is suppressed. This is for rectifying the current inside the tank.

A guide rod 26 having a smaller diameter than the outer diameter of the probe body 6 is fixed to the upper end of the probe body 3A configured as described above, and the entire body is configured in a piston shape. The boring rod 2 is further connected to the upper end of the shaft. An annular stopper 27 is fitted onto the upper end of the guide rod 26 to limit upward movement of a sleeve 30, which will be described later.

A sleeve 3 that surrounds the outer periphery of the probe body 3A over the entire length of the probe body 3A.
0 is equipped to be able to move up and down. This sleeve 30 is formed into a bottle-like cylinder shape with an open bottom. That is, the sleeve 30 has a cylindrical portion 31 that covers the side surface of the probe body 3A.
The upper end of this cylindrical portion 31 has a shoulder portion 32 bent inwardly into a substantially conical shape at the upper end of the probe body 6, and the inner end of this shoulder portion 32 abuts against the guide rod 26. The neck portion 33 extends upward.
It is composed of. The cylindrical portion 3
1 and the probe body 3A, and the O-ring 37 attached to the upper end of the neck 33 seals the space between the neck 33 and the guide rod 26, and the entire sleeve 30 is sealed. It is formed so that it can freely slide up and down. A piston-cylinder mechanism 38 is formed by the sleeve 30 thus constructed, the guide rod 26, and the probe body 6. To explain this in more detail, the sleeve 3 as a cylinder part
As shown on the left side of FIG.
A discharge port 39 is provided, and a nozzle 41 connected to a hose 40 is fitted to the outside of the discharge port 39. Then, from a water pressure pump (not shown) provided externally via the hose 40,
A predetermined amount of pressurized water is injected between the shoulder portion 32 of the sleeve 30 and the upper end surface of the probe body 6 serving as a piston portion (see arrow A in FIG. 2). By injecting this pressurized water, the sleeve 30 receives a reaction force and is moved upward (see FIG. 4).
On the other hand, the downward movement (return) of the sleeve 30 can be easily performed by opening the release valve 42 provided on the right side of the shoulder portion 32 in FIG. 2 and pushing down the entire sleeve 30. There is.

The upward movement of the sleeve 30 is restricted by the aforementioned stopper 27, and at this time the entire observation section 23 is exposed (see FIG. 4). Further, the downward movement of the sleeve 30 is restricted by the step portion 43 provided inside the shoulder portion 32 coming into contact with the upper edge of the probe body 6, and at this time, the lower end of the cylindrical portion 31 is (Fig. 2,
(See Figure 3). Therefore, the observation section 23 is sealed from the outside.

The sleeve 30 configured in this manner is placed downward before flow measurement, and the observation section 23 is filled with a liquid replacement substance (for example, NaCl solution) 24 having a conductivity different from that of groundwater in advance. Also, when measuring the flow, it is moved upward to allow groundwater to enter the observation section 23, thereby forcing the replacement substance to the outside according to the flow of the groundwater. It is.
The sleeve 30 also has the function of protecting the probe body 3A from the hole wall 1A when the probe 3 is lowered into the borehole 1.

Next, electrodes 71 to 94 protruding from the head 7
The configuration and flow measurement method will be explained based on FIGS. 6 and 7.

First, in FIG. 6, external electrodes 83 are arranged in a circle at equal intervals in the circumferential direction near the bottom end of the head 7.
~94 are arranged. In addition, this external electrode 8
Inside electrodes 3 to 94, internal electrodes 71 to 8 are arranged concentrically in the vicinity of and opposite to each of the external electrodes 83 to 94.
2 are arranged. These external electrodes 83 to 9
4 and internal electrodes 71 to 82 are four adjacent electrodes, for example, external electrodes 83 and 84 and internal electrode 7
1, 72, etc. are successively formed to form a four-electrode method, which is one of the methods for measuring the conductivity of liquids, with internal electrodes 71 and 72 having the function of current electrodes, and external electrodes 83 and 84. have the function of voltage electrodes for voltage detection, and these constitute one set of measurement electrodes.
P ₁ is formed so that one (for example, the S ₁ direction) of the 12 quantized directions S ₁ to S ₁₂ (see FIG. 6) can be measured. The other measurement electrode groups, for example, the outer electrodes 84, 85 and the inner electrodes 72, 73 (see _P2 in FIG. 6) function in exactly the same way.

Generally, the conductivity of a measured object is determined from the relationship between the voltage and current applied to the measured object, but when a current is passed through a liquid, an electrode reaction occurs and the current gradually becomes difficult to flow. , causing measurement errors. In the four-electrode method, the voltage applied to a pair of current electrodes is adjusted so that the voltage applied between a pair of voltage electrodes is always constant, thereby eliminating the measurement error and performing highly accurate measurements. It is something. Next, a measuring circuit 50 according to this embodiment is shown in FIG. In the figure, the internal electrodes 71, 72, 73, 74, . . . of each measurement electrode group P ₁ to P ₁₂ include:
A predetermined voltage is applied by an AC power supply 51 via a voltage control section 52, and current is made to flow through the liquid near each electrode. Here, voltage is applied to each pair of internal electrodes 71, 72, 73, 74, . . . by a pair of analog switches 53,
54, it is configured to perform switching sequentially at a predetermined timing. On the other hand, a pair of external electrodes ₈₃ , ₈₄ , 85,
The voltage between 86 and . and is sent to the voltage control section 52 via an amplifier 57. This voltage control section 52
is connected to each pair of internal electrodes 71, 72, 73, 7 so that the detection voltage input from the amplifier 57 is always constant for each measurement electrode group _P1 to _P12 .
4. The voltage applied between each measurement electrode group P ₁
~P ₁₂ has the function of being independently controlled. On the other hand, a resistor R for current measurement is inserted between the voltage control section 52 and the analog switch 54, and the current flowing through this resistor R is converted into a voltage between both ends of the resistor R. .about.56, and is recorded by a multi-channel recorder 60 for each of the measurement electrode groups P1 to P12. Here, the conductivity G of the liquid can be accurately measured from the relationship G = I/V using the current I flowing through the resistor R and the voltage V between the voltage electrodes. However, since V is constant, the conductivity can be measured from the change in I. Changes in rate can be measured directly. Therefore, due to the difference in conductivity between groundwater and the replacement substance, groundwater is detected in each measurement electrode group P1 to P1.
It becomes possible to accurately measure the time when the second position is reached.

Next, the overall operation of the above embodiment will be explained based on FIGS. 8 and 9.

First, in advance, in the observation part 23 of the probe 3, a substitute substance having a conductivity different from that of the groundwater to be measured (for example, an electrolytic solution such as NaCl solution if the groundwater has low conductivity; If the conductivity is relatively high, use pure water, etc. (Here, we will use NaCl solution.) 24 and move it to the lowest part of the sleeve 30 (see Fig. 3). The probe 3 is lowered into the borehole 1 to a predetermined measurement depth. At this time, the probe 3 is placed in a predetermined direction by the compass 4.

Next, after the disturbance of the groundwater due to the descent of the probe 3 subsides, pressurized water is poured into the sleeve 30 through the hose 40, and the sleeve 30 is gently moved upward. At this time, as the sleeve 30 rises, turbulent flow is generated near the lower end of the sleeve 30, but the turbulent flow inside the observation section 23 is suppressed by the action of the wire mesh 25, and the NaCl solution 24 is Almost no spillage occurs (see Figure 5).

Then, when the sleeve 30 moves to the uppermost end,
According to the flow of groundwater W, the observation section 23 gradually
Groundwater W flows into the interior, and NaCl solution 24 is pushed out. At this time, groundwater W flowing into the observation section 23 due to the action of the wire mesh 25 described above.
As shown in 2 in FIG. 8, the water advances in a convex shape in the flow direction, but since it is rectified by the wire mesh 25 and the bottom plate 8, the flow inside the observation section 23 is almost the same as the flow inside the groundwater aquifer. This results in a laminar flow state.

Here, if the groundwater W is, for example, the external electrodes 83, 8
External electrodes 89, 90 from measurement electrode group P ₁ related to 4
When flowing in the _7th direction of the measurement electrode group P related to (8th
(see K in the figure), at the time when the sleeve 30 is ascended, the groundwater W has not yet flowed into the observation section 23, and therefore all the measurement electrode groups are in the NaCl solution.
The detected conductivity is also high (1 in Figure 8, 1 in Figure 9).
(see T ₀ ). Next, the groundwater W is connected to the outer electrode 8.
When it starts to reach between 3 and 84, the conductivity of groundwater is low, so the current near the external electrodes 83 and 84 required to keep the detected voltage between the external electrodes 83 and 84 constant becomes small, and therefore the internal The current flowing between the electrodes 71 and 72 decreases, and the conductivity of the liquid detected by the measurement electrode group P ₁ in the S ₁ direction first decreases (see 2 in Figure 8 and T ₁ in Figure 9). ). This results in
At the same time as it is detected that the flow direction of the groundwater W is the _S1 direction, the timing at which the groundwater W reaches the position between the external electrodes 83 and 84 is determined. On the other hand, for other measurement electrode groups, for example P2, the arrival timing of groundwater W is delayed compared to the measurement electrode group P1, so the detected change in conductivity is also delayed (T ₂ in Fig. 9).
()reference).

As the groundwater W advances, the NaCl solution 24
As the replacement progresses and the leading edge of the groundwater W reaches the position of the measurement electrode group P7, the conductivity measured by the measurement electrode group P7 begins to decrease in the same way as described above (3 in Figure 8). , see T ₃ () in Figure 9). This decrease in conductivity is determined by representing the timing at which the groundwater W reaches the position of the measurement electrode group P7.
The groundwater flow rate can be determined from the formula L/(T ₃ -T ₁ ), where L is the distance between the measurement electrode groups P1 and P7. The same is true even if groundwater flows from other directions.

According to this example, since the four-electrode method was used to measure changes in conductivity, it was possible to accurately measure the flow of groundwater. , there is no gap in the flow detection area, so it is possible to always reliably measure flow in any direction. In addition, since the electrodes of adjacent measurement electrode groups are shared, multi-directional detection can be performed with a small number of electrodes, and conductivity changes by each measurement electrode group can be measured using a single measurement circuit. It can be done using
It becomes possible to reduce the cost of the entire device.

Further, according to this embodiment, the sleeve can be raised by simply injecting pressurized water from the outside using a piston-cylinder mechanism, and therefore the outer wall of the sleeve can be extended to the ground and raised. It is possible to reliably move upward without using a complicated structure such as this, and by preventing erroneous operations such as tangles of wires when lifting with wires or the like.

In the above embodiment, the voltage electrode for voltage detection was arranged outside the current electrode, but
As shown in FIG. 10, a pair of independent voltage electrodes 65, 65 are connected to each measurement electrode group,
The current electrodes 66 may be arranged approximately concentrically with the current electrodes 66 , 66 . Furthermore, in the above embodiments, an electrolytic solution was used as the replacement substance, but measurement sensitivity may also be improved by, for example, making use of the difference in dielectric constant, or by using a composite substance mixed with metal particles, etc. In short, any liquid substance (including sol-like substances) that has electrical (conductivity, permittivity, etc.) properties different from those of the groundwater to be measured and similar specific gravity and viscosity is sufficient. Moreover, as the above-mentioned substitution substance, one in which an ion layer is formed in the object to be measured by discharge or the like may be used.

As described above, according to the present invention, the configuration of the entire device can be simplified, and at least the flow direction of a fluid having an extremely small flow velocity can be constantly measured in any direction at a single measurement point. It is possible to provide a fluid flow measurement device that can accurately measure fluid flow and is easy to handle.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a state in which measurement is performed using the fluid flow measuring device according to the present invention, and FIG.
1 is a detailed partial cross-sectional view showing the probe portion in FIG. 1, FIGS. 3 and 4 are explanatory views of the operation of the sleeve according to a part of FIG. 2, and FIG. FIG. 6 is a partially omitted cross-sectional view taken along the - line in FIG. 2, FIG. 7 is a circuit diagram showing the measurement principle of the present invention, and FIG. 3 to 3 are explanatory diagrams showing measurement conditions, FIG. 9 is a diagram showing an example of measurement results, and FIG. 10 is a schematic diagram showing another example of the external electrode portion in FIG. 6. 3...Probe, 23...Observation section, 24...Replacement substance, 65...Voltage electrode, 66...Current electrode,
71-82...Internal electrode as current electrode, 8
3-94...External electrode as voltage electrode, 50...
...Measurement circuit.

Claims (1)

[Claims] 1. A pair of current electrodes for measuring the movement of a replacement substance having electrical properties different from those of the fluid to be measured due to the flow of the fluid, and a pair of current electrodes in the observation section of the probe inserted into the fluid to be measured, and a pair of current electrodes adjacent to the current electrodes. A plurality of measurement electrode groups using the four-electrode method each consisting of a pair of voltage detection voltage electrodes are provided concentrically, and the pair of current electrodes are arranged in the circumferential direction, and the adjacent measurement electrodes are arranged in a circumferential direction. At least the current electrode is shared between groups, and the fluid is configured such that application of voltage to the electrode and detection of voltage by the voltage electrode are performed in a time-sharing manner for each measurement electrode group. flow measuring device.