JP2006223271A - Rearing water tank for fishes and method for removing sludge in rearing water tank or the like - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for removing sludge in a rearing water tank for fishes designed to gather the sludge such as fish feces precipitating in the bottom of the water tank by actions of a fluid during draining and effectively discharge the sludge. <P>SOLUTION: The water tank 1 is formed by installing a large-diameter part 1a and a small-diameter part 1b so that the diameter D2 of the cylindrical lower part is smaller than the diameter D1 in the upper part and dividing the parts through a net body or a lattice body 11. A drain 2 and a discharge pipe 3 having a diameter comparable to that of the drain 2 are mounted in the bottom of the water tank with a somewhat gap S kept from the bottom of the water tank. When water is periodically discharged from the drain 2, a swirling flow is imparted to water in the upper part 1a of the water tank. When discharged from the drain 2 in the bottom, water is moved to the lower part 1b of the water tank. Since the diameter D2 of the lower part 1b of the water tank is smaller than the diameter D1 of the upper part of the water tank, the swirling speed is increased by the law of preservation of angular momentum. On the other hand, the swirling speed is extremely reduced due to the viscosity of water in the bottom of the water tank 1. Thereby, centrifugal force by swirling is smaller than that of water in the upper part. A strong flow toward the center is produced in the bottom because of the imbalance and the flow is bent upward in the center of the swirling. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for purifying water in an aquarium such as a fish rearing aquarium.

  Conventionally, there are various methods for removing precipitates in fish rearing tanks. For example, cleaning by draining water, or collecting a sediment in the center with a conical slope at the bottom of a flat aquarium, using a siphon effect, or an automatic cleaning robot. However, since seawater is used for breeding, the pump is easily rusted, and it is desirable that the mechanical equipment be as simple as possible. In addition, if the bottom of the water tank is inclined, not only the danger of cleaning work in the water tank is increased, but labor and cost are increased.

  Therefore, as a device for removing floating substances on the water surface in the water tank, there are a water intake port for sucking water, a purification means for purifying the sucked water, and a discharge port for discharging the purified water into the water tank. The water intake is provided at the bottom of the water tank, and a plurality of outlets are provided so as not to face the opposite side walls of the water tank, and a spiral flow with the water intake as the center of the vortex is generated in the water tank. A drainage pipe is erected on the bottom of a fish tank for raising fish (for example, see Patent Document 1), and suspended matter near the water surface is provided at the upper end of the drainage pipe. There is one that discharges deposits (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2000-15017 JP 2001-224277 A

  However, what is described in the above-mentioned Patent Document 1 generates a simple swirling flow to entrain and discharge suspended matter, and it is necessary to constantly circulate a large amount of water. Moreover, what was described in patent document 2 is not what is collected and discharged | emitted at once, and it is hard to say that purification efficiency is good. In view of the above-mentioned problems, the present invention provides a method for removing sludge from fish rearing tanks and the like that can collect and effectively discharge sludge such as fish excrement precipitated at the bottom of the aquarium by the action of fluid during drainage. An object is to provide a water tank using the method.

  Therefore, the fish tank according to the present invention has a tornado effect generated by a swirling flow applied to the contained fluid, which is formed by dividing the cylindrical aquarium so that the lower diameter is smaller than the upper diameter. The first characteristic is that the sludge at the bottom of the water tank is collected toward the rotating shaft of the swirl flow. In addition, the second feature is that the sludge at the bottom of the water tank is aggregated toward the rotational axis of the swirl flow, and is raised along the rotation axis of the swirl flow to be aggregated. Furthermore, a third feature is that a sludge discharge cylinder is provided on the rotating shaft of the swirling flow and protrudes upward from the bottom of the water tank, and the sludge raised along the rotating shaft is discharged. Furthermore, the cross section of the upper and / or lower part of the aquarium is elliptical, rectangular and / or polygonal or circular, and the horizontal cross-sectional area of the lower part of the aquarium is defined so as to be smaller than the upper part. 4 features. Further, in the method for removing sludge from the fish rearing tank of the present invention, the water tank is divided into an upper part and a lower part, and the lower part of the diameter or horizontal cross-sectional area is smaller than the upper part. The fifth feature is that the sludge at the bottom of the water tank is concentrated toward the rotation axis of the swirl flow by the tornado effect generated by the swirl flow applied to the swirl flow. A sixth feature is that the sludge at the bottom of the water tank is gathered toward the center of the rotating shaft of the swirling flow, and is raised and gathered along the rotating shaft of the swirling flow. Furthermore, a seventh feature is that a sludge discharge cylinder is provided on the rotating shaft of the swirling flow and protrudes upward from the bottom of the water tank, and the sludge raised along the rotating shaft is discharged. Furthermore, the tank is formed by dividing the tank into an upper part and a lower part, and the bottom diameter or horizontal cross-sectional area is smaller than the upper part. In the method of collecting the sludge of the swirl flow toward the rotating shaft of the swirling flow, providing a sludge discharge cylinder protruding upward from the bottom of the water tank on the rotating shaft of the swirling flow, and discharging the sludge raised along the rotating shaft, The eighth feature is that sludge is discharged from both the sludge discharge cylinder and the bottom drain port by repeatedly opening and closing the valve of the drain port provided at the bottom of the water tank.

The sludge removal method of the present invention has the following advantages.
(1) It is not necessary to incline the bottom of the aquarium, and the work in the aquarium can be performed safely.
(2) Since special machinery such as a cleaning robot is not required, it is suitable for an aquaculture tank that uses seawater.
(3) The frequency of water exchange and cleaning can be reduced even in small-scale sacrifices and viewing water tanks.

  Next, embodiments of the present invention will be described in detail with reference to examples shown in the drawings. 1 is a perspective view of a water tank according to the present invention, FIG. 2 is a cross-sectional view of a water tank schematically showing the tornado effect in the water tank, FIG. 3 is a schematic diagram of an experimental apparatus according to the present invention, and FIG. 4 shows measurement points. Schematic diagrams, FIGS. 5 to 12, are graphs showing the relationship between the opening and closing of the valve and the flow velocity.

  As shown in FIG. 1 and FIG. 2, the water tank 1 according to the present invention has a mesh or lattice on the large diameter portion 1a and the small diameter portion 1b so that the diameter D2 of the cylindrical lower portion is smaller than the diameter D1 of the upper portion. A drainage port 2 and a sludge discharge cylinder (hereinafter simply referred to as a discharge pipe 3) having the same diameter as the drainage port 2 are formed at the bottom thereof with a slight gap S ( (Preferably several centimeters). Water is periodically discharged from the drain 2. A swirling flow for raising fish is given to the water of the large diameter portion 1a. That is, water has angular momentum. When the water is discharged from the drain port 2 at the bottom, it moves to the lower part of the water tank 1. At this time, since the diameter D2 of the small-diameter portion 1b of the water tank is smaller than the diameter D1 of the large-diameter portion 1a of the water tank, the turning speed is increased on the angular momentum storage side. On the other hand, at the bottom of the water tank 1, the turning speed is extremely slow due to the viscosity of water. For this reason, the centrifugal force by turning is smaller than the centrifugal force of water in the large-diameter portion 1a, and due to this imbalance, a strong flow toward the center of the water tank occurs at the bottom as indicated by arrows in FIG. This flow is bent upward at the center of swirl. Such a flow is called a tornado effect. Furthermore, since water is also sucked in from the upper opening of the discharge pipe 3, this effect is further enhanced.

That is, when a lid is rotated at a constant angular velocity around the central axis of a cylinder in a cylindrical fixed water tank filled with a fluid and covered, the fluid inside is rotated in such a manner as to be pulled by the lid. However, since the aquarium itself is fixed, the speed is zero at the aquarium sidewall and bottom. This difference in velocity (difference in centrifugal force) causes two types of boundary layers (an Ekman layer that flows radially between the lid and the fluid, between the bottom and the fluid from the side wall toward the center of the cylinder, and between the side wall and the fluid). A circulating flow is generated that includes a Stewartson layer that flows from the lid toward the bottom. At this time, if the flow of the Ekman layer flowing between the bottom and the fluid is used, it is possible to collect a substance having a specific gravity higher than that of the fluid at the bottom of the rotating shaft. Naturally, this circulation flow is stronger as the rotation of the lid is faster, but it is impossible to generate an excessive swirl flow in an actual breeding aquarium. Therefore, the present inventors conducted an experiment to generate a strong swirl flow and a circulation flow only when the water in the aquarium is discharged based on the following conditions using the experimental apparatus shown in FIG.
(1) Change the upper and lower diameter of the tank.
(2) The valve is opened and closed when water is discharged.
(3) Attach the discharge tube to the drain outlet.
(4) Rotate the turntable attached to the upper part of the water tank.

  When removing the sludge settled on the bottom of the water tank, opening and closing of the valve (not shown) of the drain port 2 is repeated several times. By this operation, the sludge is collected around the discharge pipe 3 and discharged efficiently at a time when the valve is opened. That is, when the valve is open, the sludge concentrated in the center of the bottom due to the tornado effect is discharged sequentially from the sludge drain port 2, but once the valve is closed, an upward flow due to the tornado effect is generated, and the sludge Begins to rise along the discharge pipe 3 erected above the drain port 2. A few seconds later, when the valve of the drain port 2 is opened, the water inside the discharge pipe 3 is discharged at a stretch, and along with this, the sludge rising along the discharge pipe 3 is also discharged from the upper end opening of the discharge pipe 3. Moreover, the sludge at the bottom of the water tank is provided at the center of the bottom and is discharged from the drain port 2. After leaving for a while, the valve of the drain port is closed to generate an upward flow, and the operation of opening the valve is repeated again, whereby sludge can be discharged efficiently. As described above, sludge can be discharged efficiently by repeatedly opening and closing the valve of the drain port 2. Of course, sludge can also be discharged by keeping the valve open and closing without opening and closing the valve.

(Experimental example)
In the experimental device, a water tank 1 is provided with a valve 4, a valve opening / closing device 4a, a rotating disk 5 motor 5a and a motor control device 5b. Water in the water tank 1 is discharged by operating the valve opening / closing device. The experimental apparatus can set the full open / close time of the valve to 0 to 30 seconds, respectively, and it takes 10 seconds from the full open to the full close and from the full close to the full open. Further, when measuring the flow velocity, a probe 7 of an LDV (Laser Doppler velocimeter) 6 is fixed to the support base 8. By adjusting the handle 9 of the probe support 8, the laser intersection can be adjusted to the measurement point. Here, the diameter D1 of the large diameter portion 1a of the water tank 1 is 600 mm, the diameter D2 of the small diameter portion 1b is 300 mm, the height H1 of the large diameter portion 1a is 150 mm, and the height H2 of the small diameter portion 1b is 350 mm. In the figure, 10 is a personal computer.

Flow velocity measurement:
At the four measurement points A, B, C, and D of the water tank 1 shown in FIG. 4, when the valve is kept open, when the valve is opened periodically, or when a discharge cylinder is attached (hereinafter, there is a cylinder) The flow velocity in each state where no discharge cylinder was attached (hereinafter referred to as “no cylinder”) was measured by LDV. When the rotating disk was rotated (rotation number 15.18 rpm), both the axial component and the circumferential component were measured, and when not rotating, only the axial component was measured. here,
Measurement point A: r = 135, z = 240 Measurement point B: r = 15, z = 240
Measurement point C: r = 135, z = 80 Measurement point D: r = 15, z = 80
(R: distance from the center z: height from the bottom unit: mm).

Measurement result:
Compared to the vicinity of the central axis (points B and D), the vicinity of the side wall (points A and C) has a maximum speed and valve opening and closing (valid and hereinafter referred to as opening) for both the axial speed and the circumferential speed. The speed change during periodic opening and closing (hereinafter referred to as opening and closing) is small. Also, in the axial velocity, the upper measurement point (point A, point B) is similarly smaller in the upper measurement point (point A, point B) than the lower measurement point (point C, point D). It is thought that this is due to the suction of the drain outlet. Based on the above, the following points D were considered.

When valve is open:
As shown in FIGS. 5 and 6, at the point D, the axial speed becomes the minimum speed in about 80 seconds and then increases. As shown in FIGS. 7 and 8, the circumferential speed increased with time, and reached the maximum speed in about 120 seconds from the start of measurement.
When opening and closing the valve:
At point D, the axial speed has a larger speed change than when the valve is open. The circumferential speed was slightly changed when the valve was opened and closed. In addition, the graphs of the axial speed and the circumferential speed are in opposite phases, which is a proof that the vertical circulation is further accelerated by opening and closing the valve.

Difference with and without discharge tube:
When the discharge cylinder is installed, the amplitude of the axial speed at the time of opening and closing becomes larger than when the discharge cylinder is not installed. This seems to be due to the rectification effect of the discharge tube.

  The rotation of the turntable generated a swirl flow and a circulation flow in the fluid in the water tank. This was verified by flow measurements. When the valve is opened, the water surface reaches the lower part of the water tank 1a in about 120 seconds. Further, as shown in the graphs of FIGS. 7 and 8, the circumferential speed reaches the maximum speed in about 120 seconds from the start of measurement. From this result, it is considered that a stronger swirling flow was generated by providing a step in the water tank. Also, as can be seen from the graphs of FIGS. 9, 10, 11 and 12, by periodically opening and closing the valve, the circulation in the vertical direction is accelerated, and the tea leaves (which could not be removed only by turning with the rotating disk) It was possible to discharge the precipitate (substitute for sludge). Furthermore, it was found that by attaching the discharge cylinder, the maximum speed increases when opened and the amplitude of the speed increases when opening and closing, which is the result of the tornado effect being strengthened by the discharge cylinder. It shows validity.

Visible experiment:
After putting water in the water tank, tea leaves were put in the upper part of the water tank. Next, the movement of the tea leaves was observed when the rotating disk was rotated (rotation speed: 15.18 rpm) and when the valve was opened and closed periodically. Similarly, the movement of the tea leaves was observed when the valve was opened without rotating the turntable. In either case, the test was conducted without a drain tube.
(When there is no rotation)
When the fluid in the aquarium is stationary, the tea leaves floating on the top of the aquarium hardly fall even when the valve is opened. Even when the water surface reached the bottom of the aquarium, the tea leaves did not fall, and even when all the water was drained, most of the tea leaves remained in the aquarium.
(With rotation)
When the rotating disk was rotated, the rotation was transferred to the fluid, and the tea leaves floating at the top of the aquarium began to fall, and then all the tea leaves fell to the bottom of the aquarium. When the valve was opened, the tea leaves flowed out of the drain, and when the valve was closed, it gathered near the center. Then, when the valve was opened again, the collected tea leaves flowed all at once. By repeating this operation, most of the tea leaves in the aquarium could be removed.

  In addition, the water tank used as the object of the present invention includes not only a cylindrical water tank but also a water tank having a rectangular horizontal section and a polygonal water tank. Even in a tank having an elliptical, rectangular, or polygonal cross section, if the lower part is formed smaller than the upper part, a tornado effect is generated by the swirling flow applied to the contained fluid. Moreover, the upper part is cylindrical and the lower part is rectangular or polygonal, or vice versa, or the horizontal cross section may be arbitrarily combined up and down with a circular, elliptical, rectangular or polygonal water tank. In the experiment, a swirling flow was generated using a disk. However, in a real water tank, a method of generating a swirling flow by ejecting a fluid or a method of generating a swirling flow using a rotating propeller may be adopted. .

  INDUSTRIAL APPLICABILITY The present invention is useful in the purification technology for aquariums for raising fish such as fish breeding and ginger.

It is a perspective view of the water tank concerning the present invention. It is sectional drawing of the water tank which shows the tornado effect in a water tank typically. It is the schematic of the experimental apparatus which concerns on this invention. It is a schematic diagram which shows the measurement point of the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity. It is a graph which shows the relationship between the opening and closing of a valve | bulb, and the flow velocity.

Explanation of symbols

1 Water tank 1a Large diameter part 1b Small diameter part 2 Drain port 3 Sludge discharge pipe (discharge pipe)
4 Valve 4a Valve opening / closing device 5 Turntable 5a Motor 5b Motor control device 6 LDV
7 Probe 8 Support base 9 Handle 10 Personal computer 11 Network or lattice

Claims (8)

The bottom of the cylindrical tank is divided and formed so that it is smaller than the diameter of the upper part, and the sludge at the bottom of the tank is turned into the rotation axis of the swirling flow by the tornado effect generated by the swirling flow applied to the contained fluid. A fish tank for collecting fish, characterized by concentrating toward it. 2. The fish rearing tank according to claim 1, wherein the sludge at the bottom of the aquarium is gathered toward the rotation axis of the swirling flow, and is raised and gathered along the rotation axis of the swirling flow. The fish breeding according to claim 1 or 2, wherein a sludge discharge cylinder is provided on the rotating shaft of the swirling flow and protrudes upward from the bottom of the water tank, and the sludge raised along the rotating shaft is discharged. Aquarium. The upper and / or lower section of the aquarium is elliptical, rectangular and / or polygonal or circular, and the horizontal section of the lower section of the aquarium is partitioned so as to be smaller than the upper section. The fish tank for raising fish according to any one of claims 1 to 3. The tank is divided into an upper part and a lower part.The lower part has a lower diameter or horizontal cross-sectional area than the upper part, and the sludge at the bottom of the tank is formed by the tornado effect generated by the swirling flow applied to the contained fluid. A method for removing sludge from fish breeding aquariums, etc., characterized by concentrating toward a rotational axis of a swirling flow. 6. The sludge removal of a fish breeding aquarium or the like according to claim 5, wherein the sludge at the bottom of the aquarium is gathered toward the center of the rotating shaft of the swirling flow and is gathered by raising along the rotating shaft of the swirling flow. Method. 6. The fish breeding according to claim 4 or 5, wherein a sludge discharge tube is provided on the rotating shaft of the swirling flow and protrudes upward from the bottom of the water tank, and the sludge raised along the rotating shaft is discharged. Sludge removal method for water tanks. The tank is divided into an upper part and a lower part.The lower part has a lower diameter or horizontal cross-sectional area than the upper part, and the sludge at the bottom of the tank is formed by the tornado effect generated by the swirling flow applied to the contained fluid. In a method of providing a sludge discharge tube that is concentrated toward the rotating shaft of the swirling flow and protrudes upward from the bottom of the water tank on the rotating shaft of the swirling flow, the sludge raised along the rotating shaft is discharged. A method for removing sludge from a fish rearing tank or the like, wherein sludge is discharged from both the sludge discharge tube and the bottom drain port by repeatedly opening and closing the valve of the drain port provided.

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