CN201732497U - Reynolds experimental apparatus - Google Patents

Abstract

The utility model discloses a Renault experimental instrument, which is provided with a water supply tank under the test platform, a stable water tank above the test platform, a small water tank for holding colored water above the stable water tank, a water pump in the water supply tank and a water supply pipeline connected to each other, and a water supply valve is installed on the water supply pipeline; a water diversion tee is provided in the water stabilization tank, and the water supply valve is connected to the water diversion tee through a pipeline, and vertically intersecting side partitions I and II are set in the water stabilization tank , there is a stabilizing hole on the side partition Ⅰ, the other side of the side partition Ⅱ is connected to the overflow channel, and a trumpet-shaped inlet is installed on the side wall of the lower section of the stabilizing water tank, and the trumpet-shaped inlet is connected with the experimental pipeline. Two pressure measuring nozzles are installed at intervals on the experimental pipeline, and the two pressure measuring nozzles are connected to the pycnometer. The end of the experimental pipeline is provided with a tail water valve; the small water tank is inserted into the trumpet-shaped inlet through the colored water pipeline and the needle. The utility model enables Raynaud's experiment to be verified accurately.

Description

Renault tester

technical field

The utility model belongs to the technical field of fluid mechanics experiment equipment, and relates to a Renault experiment instrument.

Background technique

Reynolds experiment is one of the necessary experiments in the teaching of fluid mechanics (hydraulics). It was first developed by British mechanics, physicist and engineer Reynolds. In 1885, Reynolds used experiments to reveal the different nature of laminar flow and turbulent flow in actual liquid movement. It has a history of more than 100 years. At present, there are many Reynolds experimental instruments at home and abroad, some are placed horizontally and some are vertically placed. For example, the JK-LN Renault experimental instrument produced by China Xiangtan Jinkai Chemical Equipment Technology Co., Ltd. is 1.2m long and 0.45m high; the LNS-B Renault experimental instrument is only 0.6m long and 2.35cm in inner diameter, which is a relatively short instrument. ; The H-1 Renault experimental instrument developed by Zhejiang University in China, the test table is 1.5m long, and the water tank is 0.55m high; the above-mentioned instruments are all placed horizontally. China Zhejiang Zhongkong Science and Education Instrument Equipment Co., Ltd. produces the LN100Y Renault demonstration experiment device, which is vertical.

One common point of the above instruments is that when judging laminar flow and turbulent flow, they all use the color water in the pipeline to estimate when it is laminar flow and when it is turbulent flow. If the color water is a colored straight line, it is laminar flow, if the color water vibrates, it is the transition zone from laminar flow to turbulent flow, and if the color water is completely mixed in the water, it is turbulent flow. The lower critical Reynolds number (Re=2320) is measured by visual estimation, which is the Reynolds number when laminar flow changes to turbulent flow.

，但对于一般程度的粗糙壁管，

值稍小，约为2000。因此，这种目估的实验方法存在着严重的缺陷。而雷诺实验本身是需要测量出两个参数，即流速(或雷诺数)和沿程水头损失，通过点绘流速(或雷诺数)与沿程水头损失的关系，求出下临界流速或下临界雷诺数，这样作避免了目估的局限性，保证了下临界雷诺数的唯一性。The above experiment is not strict in operation, because the Reynolds experiment is a classic verification experiment, and Reynolds has given the lower critical Reynolds number (Re=2320) through the experiment. However, when the Reynolds number is less than 2320, the color water is always a straight line, so in the experiment, it is not known which colored straight line is the colored straight line required for the lower critical Reynolds number. Debug traffic to meet the requirements of the experiment. However, experiments have shown that the Reynolds number of different instruments is slightly different. For a very smooth and uniform straight circular tube, the lower critical Reynolds number

, but for generally rough-walled tubes,

The value is slightly smaller, around 2000. Therefore, this experimental method of visual estimation has serious flaws. The Reynolds experiment itself needs to measure two parameters, that is, the flow velocity (or Reynolds number) and the head loss along the way. By plotting the relationship between the flow velocity (or Reynolds number) and the head loss along the way, the lower critical flow velocity or lower critical Reynolds number, which avoids the limitation of visual estimation and ensures the uniqueness of the lower critical Reynolds number.

The research on Raynaud's experimental apparatus has also gone through a long process of change. In the past (before the 1970s), the length of the Renault tester was relatively long, generally several meters long. For example, the pipe length of an original Renault tester was 6m. In recent decades, the Renault tester has been miniaturized. The length is suddenly shortened. At present, the Renault experimental instrument developed by Zhejiang University in China is widely used in the market. The experimental table is only 1.5m long. Excluding the length of the water tank, the experimental pipe section is even shorter. The length of the pipe section is suddenly shortened from several meters in the past to less than 1 meter. Objectively speaking, the accuracy of the experiment will be affected to a certain extent. This is also the reason why many Reynolds experiments do not measure the head loss along the way, because the pressure difference is small when the pipe is short, and the measurement accuracy is not high.

Over the years, through the development of the Reynolds experimental instrument and through teaching experiments, it is believed that the length of the tube section of the past Reynolds experimental instrument is too long, while the length of the tube section of the experimental instrument currently used is too short, and the lower critical Reynolds number is not measured by the method of visual estimation. Rigorous, not precise enough.

Contents of the invention

The purpose of this utility model is to provide a Reynolds experimental instrument, which can qualitatively judge the laminar flow and turbulent flow phenomena through the demonstration of colored water, and then calculate the Reynolds number by measuring the head loss and flow along the way, and draw the Reynolds number and the along the way Find the lower critical Reynolds number from the relation of head loss.

The technical solution adopted by the utility model is that a Renault experimental instrument includes a water supply tank under the test bench, a water stabilization tank above the test bench, and a small water tank for holding colored water above the stabilization water tank. A water pump is installed in the water supply tank, and the water pump is connected to the water supply pipeline, and a water supply valve is installed on the water supply pipeline; a water diversion tee is arranged in the water stabilization tank, and the water supply valve is connected to the water diversion tee through a pipeline. The vertical intersecting side partition I and side partition II are arranged in the stabilizing water tank, and there are water stabilizing holes on the side partition I. One side of the side partition II is the water inlet, and the other side is connected to the overflow channel. The side wall of the lower section of the water tank is equipped with a horn-shaped inlet, which is connected with an equal-diameter test pipe. The pressure measuring nozzles are respectively connected with the oblique pycnometers for measuring the pressure difference, and the end of the experimental pipeline is provided with a tail water valve for adjusting the flow rate; the small water tank is connected with the color water pipeline through a hose, and a water stop is provided on the hose. Clamp, the color water pipe is stretched in the trumpet-shaped inlet through the needle.

The Renault experimental instrument of the utility model is also characterized in that the water supply tank is connected to the water receiving box through the return pipe, and the water receiving box corresponds to the water outlet of the tail water valve above.

The beneficial effect of the utility model is that the Reynolds number and the measurement of the water head loss along the way are integrated, the structural layout of the water supply tank, the water stabilization tank, and the experimental pipeline are reasonable, the overall volume is small, and the length of the pipeline is moderate, which effectively solves the problem of lower criticality. The measurement of Reynolds number has many functions, high precision, simple structure, easy operation and easy manufacture.

Description of drawings

Fig. 1 is the front view of the utility model Renault experiment instrument;

Fig. 2 is the side view of the utility model Renault experiment instrument;

Fig. 3 is the top view of the utility model Renault experiment instrument;

Figure 4 is a relationship diagram between head loss and flow velocity along the way;

Figure 5 is a schematic diagram of the calculation of head loss along the way.

In the figure, 1. Water supply tank, 2. Water pump, 3. Water supply pipe, 4. Water supply valve, 5. Water diversion tee, 6. Stabilizing water tank, 7. Side partition Ⅰ, 8. Side partition Ⅱ, 9. Stabilizing water hole, 10. Overflow channel, 11. Overflow pipe, 12. Trumpet-shaped inlet, 13. Small water tank, 14. Hose, 15. Color water pipe, 16. Water stop clip, 17. Needle, 18. Experimental pipeline, 19. Pressure measuring nozzle, 20. Specific pressure gauge, 21. Tail water valve, 22. Water receiving box, 23. Support, 24. Return water pipe, 25. Experimental bench.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

With reference to Fig. 1, Fig. 2, Fig. 3, the structure of the Renault experiment instrument of the present utility model is, comprises the water supply box 1 and the water receiving box 22 that are arranged on the test bench 25 below, and the water receiving box 22 connects with the water supply box 1 through the return pipe 24 connected, water pump 2 is housed in water supply tank 1, and water pump 2 is connected with water supply pipeline 3, and water supply valve 4 is housed on water supply pipeline 3; There is a water diversion tee 5, and the water supply valve 4 is connected to the water diversion tee 5 through a pipeline. The vertically intersecting side partition I7 and side partition II8 are arranged in the water stabilization tank 6, and the water diversion tee 5 is located between the side partition I7 and the side partition II8. In the small space separated by the side partition II8, there is a water stabilizing hole 9 on the side partition I7, and the stabilizing hole 9 is used to input the incoming water of the water supply tank 1 into the large space of the stabilizing water tank 6, and the side partition II8 One side is water inlet, the other side is connected with the overflow channel 10, the top of the side partition II 8 is used for overflow, the lower end of the overflow channel 10 is provided with an overflow pipe 11, and the overflow pipe 11 is connected with the water supply tank 1. The side wall of the lower part of the large space of the stabilizing water tank 6 is equipped with a horn-shaped inlet 12, and the horn-shaped inlet 12 is connected with the experimental pipeline 18 of equal diameter. Two pressure measuring nozzles 19 are installed, and the two pressure measuring nozzles 19 are connected to the oblique pycnometer 20 for measuring the pressure difference through the flexible pipe 14. The valve 21 corresponds to the water receiving box 22 below; a small water tank 13 containing color water is arranged above the stable water tank 6, and the small water tank 13 communicates with the color water pipeline 15 through a flexible pipe 14, and a water tank 13 is arranged on the flexible pipe 14. Water stop clamp 16, color water pipeline 15 stretches in the horn-shaped inlet 12 by needle 17.

The experimental pipeline 18 is set as a relatively long pipeline with a length of 185 cm.

The pressure gauge 20 can be used to visually display the liquid level and accurately measure the water head loss along the way.

The operating principle of the Renault experimental instrument of the present utility model is:

There are two different flow patterns in actual fluids, laminar flow and turbulent flow. The characteristic of laminar flow is that when the flow velocity is small, the particles of the fluid do not mix with each other and form a linear motion, and there is no pulsation phenomenon. The characteristic of turbulent flow is that the particles in the liquid are mixed with each other, the trajectory of its movement is tortuous and chaotic, and the moving elements pulsate. In between is the transitional flow state from laminar flow to turbulent flow, known as the transition from laminar flow to turbulent flow.

In order to qualitatively distinguish two different flow forms of laminar flow and turbulent flow, a small water tank 13 filled with colored water is arranged on the top of the water stabilization tank 6, and colored water is filled in the small water tank 13. During the test, open the water stop clamp 16 on the color water pipeline 15, make the color water enter the test pipeline 18 through the needle 17, adjust the tail water valve 21 on the test pipeline 18 to the maximum, and make the tail water valve 21 gradually decrease from large to small. Closed, it can be seen that the colored water is completely mixed in the water flow at the beginning, which is turbulent flow. When the tail water valve 21 is opened to a certain degree, it can be seen that the colored water starts to vibrate in the pipeline, which is the turbulent flow direction. In the transition of laminar flow, turn off the small tail water valve 21 again, and you can see that the colored water forms a colored straight line, which is laminar flow. If the tail water valve 21 is gradually opened from small to large, it can be seen that the evolution law of the color water is that when the flow rate is small, it is a colored straight line, which is laminar flow. When the tail water valve 21 is opened to a certain value, the color The water starts to vibrate, which is the transition from laminar flow to turbulent flow. When the tail water valve 21 is opened to a certain value, the colored water is completely mixed into the water, which is the phenomenon of turbulent flow. the

次方成比例，用公式表示：As shown in Figure 4, the Reynolds experiment also confirmed that the laws of head loss along the laminar flow and turbulent flow are also different. The head loss along the way is proportional to the first power of the flow velocity in laminar flow, and the head loss along the way is proportional to the flow velocity in turbulent flow.

The power is proportional, expressed by the formula:

(1)

为沿程水头损失；

为流速；为指数；

为比例系数。层流时

，紊流时

。可见，要确定水头损失必须先确定流动型态。In the formula

is head loss along the way;

is the flow rate; is the index;

is a proportionality factor. laminar flow

, when turbulent flow

. It can be seen that to determine the head loss, the flow pattern must be determined first.

As shown in Figure 5, the calculation principle of the head loss along the way is to install a piezometric tube on the two sections 1-1 and 2-2 of the experimental pipeline 18 respectively, and the sections 1-1 to 2-2 can be measured. 2 head loss. From the energy equation:

                  (2)

(2)

，则：In the formula, ,Pick

,but:

                        (3)                    

(3)

It can be seen from the above formula that the head difference between the two piezometric tubes at the 1-1 section and the 2-2 section is the head loss along the way.

In order to measure the water head loss along the way, a pressure measuring nozzle 19 is respectively set on the 1-1 and 2-2 sections taken, and the pressure measuring nozzle 19 is connected with the dynamometer 20 with a hose. It is to improve the accuracy of measuring head loss along the way.

The criterion for identifying the flow pattern is the Reynolds number. For circular pipe flow, the Reynolds number is calculated by the following formula

                           (4)

(4)

为雷诺数；

为圆管断面水流的平均流速；

为水流的运动粘滞系数，计算式为：In the formula,

is the Reynolds number;

is the average flow velocity of the water flow in the section of the circular pipe;

is the kinematic viscosity coefficient of water flow, and the calculation formula is:

                     (5)

(5)

Experiments have proved that when the Reynolds number is less than 2320, the water flow in the pipeline is laminar flow, and when the Reynolds number is greater than 2320, the water flow in the pipeline is turbulent flow. Therefore, the flow pattern of water flow can be judged by Reynolds number.

The operating steps of the utility model device are:

和两个测压断面之间的距离L。1) Record the pipe diameter

and the distance L between the two piezometric sections.

2) Turn on the water pump 2 to make the water stabilization tank 6 full of water and keep the overflow state. Then adjust the tail water valve 21, and after the water flow is stable, open the color water valve to observe the change of the color water. When the colored water is in a stable and obvious straight line in the test pipe 18, the pipe is in a laminar flow state. Gradually adjust the tail water valve 21 to increase the flow rate. At this time, the colored water starts to vibrate, bend, have a wave profile, and gradually spread. When it spreads to the whole pipe, the water flow is so turbulent that the colored streamline can no longer be seen clearly. Turbulent flow pattern.

3) Determine the lower critical Reynolds number. After the second step is completed, close the water stop clamp 16 on the color water pipeline 15, close the tail water valve 21 at the same time, open the air release nozzle on the pressure gauge 20, and discharge the air in the pressure gauge 20, whether the air is exhausted The best inspection method is that the water surfaces of the two pressure measuring tubes on the pycnometer should be flush when the pipeline does not flow.

4) Open the tail water valve 21 and adjust the tail water valve 21 to the maximum. After the water flow is stable, use a steel ruler to measure the readings L ₁ and L ₂ of the two piezometric tubes on the pycnometer, and the two piezometric tubes are The water surface difference is Δ L = L ₁ - L ₂ . Measure the flow with a graduated cylinder and a stopwatch.

5) Gradually close the tail water valve 21 and repeat step 4 N times.

6) Measure the water temperature with a thermometer.

7) After the experiment, restore the instrument to its original state.

(α为比压计斜面与水平面的夹角)与雷诺数

的关系，求出下临界雷诺数

。8) Plot head loss on logarithmic paper

(α is the angle between the slope of the pressure gauge and the horizontal plane) and the Reynolds number

The relationship between and find the lower critical Reynolds number

.

The beneficial effects of the utility model are: the measurement of the Reynolds number and the measurement of the head loss along the way are closely combined, and the lower critical Reynolds number is obtained by plotting the relationship between the head loss along the way and the Reynolds number, so that the experimental results remain unique. The result is clear at a glance, avoiding the errors caused by human estimation, and bringing the Reynolds experiment back to Reynolds' original method. The instrument can also measure the head loss coefficient along the way, which is a multifunctional instrument. The instrument is small in size, simple in structure, multi-functional, high in precision, easy to operate and easy to manufacture.

Claims (2)

1. A kind of Renault experiment instrument, it is characterized in that, comprise being provided with water supply box (1) below test bench (25), be provided with stabilizing water tank (6) above test bench (25), in stabilizing water tank (6) The top is provided with the small water tank (13) that fills colored water, A water pump (2) is housed in the water supply tank (1), and the water pump (2) is connected to the water supply pipeline (3), and a water supply valve (4) is housed on the water supply pipeline (3); The water stabilizing tank (6) is provided with a water diversion tee (5), the water supply valve (4) is connected to the water diversion tee (5) through a pipeline, and the vertical intersecting side partition I is set in the stabilizing water tank (6) (7) and the side partition II (8), on the side partition I (7) there is a stabilizing hole (9), one side of the side partition II (8) is the water inlet, and the other side is connected to the overflow channel (10) is connected, and the lower section sidewall of stabilizing water tank (6) is equipped with trumpet-shaped inlet (12), and the trumpet-shaped inlet (12) is connected with the experiment pipeline (18) of equal diameter, and experiment pipeline (18) passes support ( 23) It is arranged on the upper surface of the test platform (25), and two pressure measuring nozzles (19) are installed at intervals on the experimental pipeline (18). The pressure gauge (20) is connected, and the end of the experimental pipeline (18) is provided with a tail water valve (21) for adjusting the flow rate; The small water tank (13) communicates with the color water pipe (15) through a hose (14), and a water stop clip (16) is arranged on the hose (14), and the color water pipe (15) extends into the water pipe (15) through a needle (17). In the trumpet-shaped inlet (12). 2. The Renault tester according to claim 1, characterized in that, the water supply tank (1) is connected to the water receiving box (22) through the water return pipe (24), and the water receiving box (22) is connected to the tail of the top. The water outlet of water valve (21) is corresponding.

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