CN108760232B - A test device and test method for exploring the surface drag reduction mechanism - Google Patents

Abstract

The invention belongs to the technical field of drag reduction tests, and discloses a test device for exploring a surface drag reduction mechanism, which comprises a water storage tank, a peristaltic pump, an air injection pump, a pressure sensor, a PIV measuring instrument, a Micro-PIV measuring instrument and a computer receiving and processing system, wherein the water storage tank is provided with a fluid inlet and a fluid outlet; the fluid outlet is connected with the inlet of the peristaltic pump through the first conveying pipeline, and the outlet of the peristaltic pump is connected with the second conveying pipeline; the fluid inlet of the water storage tank is connected with a third conveying pipeline; the pressure sensors are arranged at two, and each pressure sensor is respectively arranged at one end of the test tube to be tested; the PIV measuring instrument and the Micro-PIV measuring instrument are used for measuring the velocity field of the fluid in the test tube to be measured. The test device can test the drag reduction effect of the drag reduction surface by using a smaller sample, is beneficial to reducing the research and development cost of drag reduction technology, and has simple structure and convenient replacement of the test tube to be tested.

Description

A test device and test method for exploring the surface drag reduction mechanism

Technical field

The invention belongs to the technical field of drag reduction testing, and more specifically, relates to a test device and a test method for exploring the surface drag reduction mechanism.

Background technique

Due to its own viscosity, the fluid will have resistance at the surrounding interface during the flow process, such as ship resistance, underwater navigation body resistance, and transportation pipeline resistance.

As the energy crisis continues to intensify, research on fluid flow drag reduction technology applied in different scenarios has become a hot topic at home and abroad. Its research methods mainly include theoretical analysis, numerical simulation and experiment. Among them, the test method is considered the most important means to study surface drag reduction technology because of its accuracy and authenticity.

However, the existing test methods have certain shortcomings, mainly as follows:

1) Current drag reduction test research is mostly conducted in large water tunnels and water tanks, and is mainly focused on evaluating the drag reduction effect. Due to the large size of the overall equipment, huge equipment maintenance and test surface preparation costs will be incurred.

2) If the drag reduction effect is measured at the laboratory level, the direct detection of resistance will have a large numerical error because the plane is too small.

3) In terms of research on the mechanism of drag reduction, current experimental research methods focus more on the macroscopic velocity field, while there are fewer observations on the microscopic velocity field caused by drag reduction, and a large number of details are ignored compared to numerical simulation.

4) Most of the current pipeline drag reduction test studies do not have replaceable structures and are difficult to process, making testing inconvenient.

Contents of the invention

In view of the above defects or improvement needs of the existing technology, the present invention provides a test device and a test method for exploring the surface drag reduction mechanism, which can be used to test a variety of different drag reduction methods, thereby exploring during the development process of the drag reduction surface. The mechanism of surface drag reduction while saving R&D costs.

In order to achieve the above object, according to one aspect of the present invention, a test device for exploring the surface drag reduction mechanism is provided, which is characterized in that it includes a water storage tank, a peristaltic pump, an air injection pump, a pressure sensor, a PIV measuring instrument, and a Micro-PIV Measuring instruments and computer reception and processing systems, wherein,

The water storage tank has a fluid inlet and a fluid outlet;

The fluid outlet is connected to the inlet of the peristaltic pump through a first delivery pipeline, and the outlet of the peristaltic pump is connected to a second delivery pipeline, and the second delivery pipeline is used to connect one end of the pipeline to be tested;

The fluid inlet of the water storage tank is connected to a third delivery pipe, and the third delivery pipe is used for the other end of the pipe to be tested;

There are two pressure sensors, each of which is installed on one end of the pipeline to be tested, for passing fluid into the pipeline to be tested and then measuring the pressure, thereby obtaining the pipeline to be tested. The pressure difference at both ends is used to obtain the resistance of the pipeline to be tested;

The PIV measuring instrument and Micro-PIV measuring instrument are used to measure the velocity field of the fluid in the pipeline to be tested;

The PIV measuring instrument, Micro-PIV measuring instrument and each pressure sensor are respectively connected to the computer receiving and processing system.

Preferably, the second transportation pipe is connected to the pipe to be tested through a joint, the second transportation pipe is a round pipe, the pipe to be tested is a square pipe, and the cross section of the inner cavity of the second transportation pipe is The area is larger than the cross-sectional area of the inner cavity of the pipeline to be tested.

Preferably, the pipeline to be tested is surrounded by an upper wall, two side walls and a lower wall, and the upper wall is detachably connected to the two side walls, and the lower wall is also detachably connected to the two side walls.

Preferably, the third transportation pipe is connected to the pipe to be tested through a joint, the third transportation pipe is a round pipe, the pipe to be tested is a square pipe, and the cross section of the inner cavity of the third transportation pipe is The area is larger than the cross-sectional area of the inner cavity of the pipeline to be tested.

Preferably, it also includes an air injection pump and a high-speed camera for injecting air into the inside of the pipe to be tested from the air injection hole provided on the pipe to be tested, thereby generating bubbles, which are then photographed by the high-speed camera to record The shape and velocity of bubbles near the inner wall of the pipe to be tested.

Preferably, the fluid inlet and the fluid outlet are respectively provided on two opposite side walls of the water storage tank, and the height of the fluid inlet is greater than the height of the fluid outlet;

A bubble isolation net is provided in the water storage tank to remove bubbles flowing into the water storage tank.

According to another aspect of the present invention, there is also provided a test method for exploring the surface drag reduction mechanism using the test device, which is characterized in that it includes the following steps:

a. Select the pipeline to be tested without drag reduction treatment and connect it to the second transportation pipeline and the third transportation pipeline;

b. Turn on the peristaltic pump and adjust the fluid flow rate to make the fluid flow in the pipeline to be tested smooth and even;

c. Turn on the PIV measuring instrument, measure the velocity field of the fluid in the pipeline to be tested, and transmit the velocity field data to the computer receiving and processing system;

d. Turn on the Micro-PIV measuring instrument, measure the velocity field of the fluid close to the inner wall of the pipe to be tested, and transmit the velocity field data to the computer receiving and processing system;

e. Use two pressure sensors to measure the pressure at both ends of the pipeline to be tested, and transmit the data to the computer receiving and processing system;

f. Use the computer receiving and processing system to process the received data to obtain the drag reduction effect, flow field velocity distribution and vortex structure under the current fluid flow rate;

g. Perform drag reduction treatment on the pipeline to be tested in step a, and then connect it to the second transportation pipeline and the third transportation pipeline;

h. Repeat steps b to f;

i. Obtain drag reduction rate DR:

Among them, ΔP _none is the pressure difference at both ends of the pipeline to be tested without drag reduction treatment, and ΔP is the pressure difference at both ends of the pipeline to be tested with drag reduction treatment.

Preferably, the drag reduction treatment in step g includes arranging micro-texture, arranging a flexible surface, arranging a polymer coating and/or inputting air bubbles on the inner wall surface of the pipeline to be tested.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The present invention can use smaller samples (pipes to be tested) to test the drag reduction effect of the drag reduction surface, which is beneficial to reducing the research and development costs of drag reduction technology. Moreover, the test device of the present invention has a simple structure and is easy to test. Pipe replacement is also easier;

(2) In the present invention, both the upper wall and the lower wall of the test pipeline can be replaced, so the inner wall surface of the upper wall and the inner wall surface of the lower wall can be subjected to drag reduction treatment, which is beneficial to the drag reduction effect of different drag reduction treatment methods. Compare the drag reduction mechanism;

(3) The testing of the PIV measuring instrument and the testing of the Micro-PIV measuring instrument can be carried out simultaneously in this test device, which is conducive to measuring velocity fields of different scales and more accurately exploring the drag reduction mechanism of the inner wall of the pipeline to be tested.

Description of the drawings

Figure 1 is a structural diagram of the present invention;

Figure 2 is a schematic diagram of the test pipeline in the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Referring to Figures 1 and 2, a test device for exploring the surface drag reduction mechanism includes a water storage tank 9, a peristaltic pump 6, an air injection pump 3, a pressure sensor 13, a PIV measuring instrument 1, a Micro-PIV measuring instrument 2 and a computer receiver. Processing system 4, where,

The water storage tank 9 has a fluid inlet and a fluid outlet;

The fluid outlet is connected to the inlet of the peristaltic pump 6 through the first delivery pipeline 15, and the outlet of the peristaltic pump 6 is connected to the second delivery pipeline 14. The second delivery pipeline 14 is used to connect one end of the pipeline 10 to be tested;

The fluid inlet of the water storage tank 9 is connected to a third delivery pipe 7, which is used for the other end of the pipe to be tested 10;

There are two pressure sensors 13 , and each pressure sensor 13 is installed at one end of the pipeline 10 to be tested, and is used to measure the pressure after passing fluid into the pipeline 10 to be tested, thereby obtaining the required pressure. Describe the pressure difference at both ends of the pipeline to be tested 10, and then obtain the resistance of the pipeline to be tested 10;

The PIV measuring instrument 1 and Micro-PIV measuring instrument 2 are used to measure the velocity field of the fluid in the pipeline 10 to be tested;

The PIV measuring instrument 1, the Micro-PIV measuring instrument 2 and each of the pressure sensors 13 are respectively connected to the computer receiving and processing system 4.

Further, the second transportation pipe 14 is connected to the pipe to be tested 10 through the joint 5. The second transportation pipe 14 is a round pipe, the pipe to be tested 10 is a square pipe, and the second transportation pipe 14 The cross-sectional area of the inner cavity is larger than the cross-sectional area of the inner cavity of the pipe 10 to be tested.

Further, the third conveying pipe 7 is connected to the pipe to be tested 10 through the joint 5. The third conveying pipe 7 is a round pipe, the pipe to be tested 10 is a square pipe, and the third conveying pipe 7 The cross-sectional area of the inner cavity is larger than the cross-sectional area of the inner cavity of the pipe 10 to be tested.

Furthermore, an air injection pump 3 and a high-speed camera are included for injecting air into the interior of the pipe to be tested 10 from the air injection hole 11 provided on the pipe to be tested 10 to generate bubbles, which are then photographed by the high-speed camera. , to record the shape and speed of the bubble near the inner wall surface of the pipe 10 to be tested.

Further, the fluid inlet and the fluid outlet are respectively provided on two opposite side walls of the water storage tank 9, and the height of the fluid inlet is greater than the height of the fluid outlet, and there is a height difference h between the two;

A bubble isolation net 8 is provided in the water storage tank to remove bubbles flowing into the water storage tank 9 .

The specific steps of the test method to explore the surface drag reduction mechanism are:

a. Select the pipeline to be tested 10 without drag reduction treatment and connect it to the second transportation pipeline 14 and the third transportation pipeline 7;

b. Turn on the peristaltic pump 6 and adjust the fluid flow rate to make the fluid flow in the pipeline 10 to be tested smooth and even;

c. Turn on the PIV measuring instrument 1, measure the velocity field of the fluid in the pipeline 10 to be tested, and transmit the velocity field data to the computer receiving and processing system 4;

d. Turn on the Micro-PIV measuring instrument 2, measure the velocity field of the fluid close to the inner wall of the pipeline 10 to be tested, and transmit the velocity field data to the computer receiving and processing system 4;

e. Use two pressure sensors 13 to measure the pressure at both ends of the pipeline 10 to be tested, and transmit the data to the computer receiving and processing system 4;

f. Use the computer receiving and processing system 4 to process the received data to obtain the drag reduction effect, flow field velocity distribution and vortex structure under the current fluid flow rate;

g. Perform drag reduction treatment on the pipeline to be tested 10 in step a, and then connect it to the second transportation pipeline 14 and the third transportation pipeline 7;

h. Repeat steps b to f;

i. Obtain drag reduction rate DR:

Among them, ΔP _none is the pressure difference at both ends of the pipeline to be tested 10 without drag reduction treatment, and ΔP is the pressure difference at both ends of the pipeline to be tested 10 with drag reduction treatment. The greater the drag reduction rate DR, it proves that the adopted drag reduction measures have better drag reduction effect.

j. Turn off the peristaltic pump 6, drain the fluid in the pipeline to be tested 10 and each delivery pipe, and end the test.

The fluid of the present invention is driven by a peristaltic pump 6, which sucks the fluid out of the storage tank 9 and flows into the pipeline to be tested through the first transportation pipeline 15; the first transportation pipeline 15 and the pipeline to be tested 10 need to be connected in series with a practical pipeline connection joint 5 , the first to third conveying pipes are all seamless pipes. The larger circular structure of the first conveying pipe 15 and the smaller square structure of the pipe to be tested 10 make the fluid flow in the pipe to be tested more uniform. ; The pipeline to be tested 10 is fixed on the bottom surface of the measurement bench using the test pipeline bracket 12; a pair of pressure sensors 13 are arranged at a distance inward at both ends of the pipeline to be tested 10, and the pressure difference between the front and rear of the pipeline is used to describe the resistance of the pipeline; in the pipeline to be tested PIV measuring instrument 1 and Micro-PIV measuring instrument 2 are arranged in the middle section, and the flow field inside the pipeline 10 to be tested at the same axial position and near the inner wall surface can be measured through different plane arrangements; if the drag reduction effect of bubble drag reduction is tested, the flow field can be measured. Arrange an air injection hole 11 upstream of the wall to be tested (close to the first delivery pipe), use the air injection pump 3 to inject air near the wall, and use a high-speed camera to record the bubble shape; after the fluid flows through the pipe to be tested 10, It flows back into the storage tank 9 along the third conveying pipe 7; there is a height difference between the fluid inlet and the fluid outlet of the storage tank 9, and this height difference and the arranged bubble isolation net 8 are used to remove bubbles in the fluid; pressure sensor 13, PIV measuring instrument The data obtained by 1 and Micro-PIV measuring instrument 2 are finally transferred to the computer receiving and processing system 4 for data processing and analysis.

Referring to Figure 2, the pipe to be tested 10 of the measuring device of the present invention is designed to be detachable and assembleable. It includes an upper wall 16, two side walls 17 and a lower wall 18. The material is a transparent acrylic plate; the upper wall 16 and the lower wall 18 are The main test surface can be replaced by disassembling and replacing the required test drag reduction method; the pressure sensor 13 is arranged at a fixed position on the side wall 17; to ensure detachability, waterproof tape is used on the outside of the wall for fixation.

This invention can measure the friction resistance of pipelines on walls with different flow rates and different drag reduction methods, and evaluate the drag reduction effect of the tested drag reduction methods through the drag reduction rate; at the same time, the PIV test and the Micro-PIV test are used to test the structures near the fluid wall. The measurement is processed by the computer receiving and processing system to explore the drag reduction mechanism of the tested drag reduction method. The test device has a simple structure and is easy to operate; it can test different drag reduction methods as needed, including surface micro-texture, surface polymer coating, flexible surface, input bubbles, etc. The test principle of the invention is intuitive, the results are accurate, and it has a wide range of application.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (7)

1. A test device for exploring the surface drag reduction mechanism, characterized by including a water storage tank, a peristaltic pump, an air injection pump, a pressure sensor, a PIV measuring instrument, a Micro-PIV measuring instrument and a computer receiving and processing system, wherein, The water storage tank has a fluid inlet and a fluid outlet; The fluid outlet is connected to the inlet of the peristaltic pump through a first delivery pipeline, and the outlet of the peristaltic pump is connected to a second delivery pipeline, and the second delivery pipeline is used to connect one end of the pipeline to be tested; The fluid inlet of the water storage tank is connected to a third delivery pipe, and the third delivery pipe is used for the other end of the pipe to be tested; There are two pressure sensors, each of which is installed on one end of the pipeline to be tested, for passing fluid into the pipeline to be tested and then measuring the pressure, thereby obtaining the pipeline to be tested. The pressure difference at both ends is used to obtain the resistance of the pipeline to be tested; The PIV measuring instrument and Micro-PIV measuring instrument are used to measure the velocity field of the fluid in the pipeline to be tested; The PIV measuring instrument, the Micro-PIV measuring instrument and each of the pressure sensors are respectively connected to the computer receiving and processing system; It also includes an air injection pump and a high-speed camera for injecting air into the inside of the pipe to be tested from the air injection hole provided on the pipe to be tested, thereby generating bubbles, and then photographing the bubbles through the high-speed camera to record the movement of the bubbles. Test the shape and velocity near the inner wall of the pipe; The fluid inlet and the fluid outlet are respectively disposed on two opposite side walls of the water storage tank, and the height of the fluid inlet is greater than the height of the fluid outlet. 2. A test device for exploring surface drag reduction mechanism according to claim 1, characterized in that the second transportation pipe is connected to the pipe to be tested through a joint, and the second transportation pipe is a round pipe, The pipeline to be tested is a square tube, and the cross-sectional area of the inner cavity of the second transport pipeline is larger than the cross-sectional area of the inner cavity of the pipeline to be tested. 3. A test device for exploring surface drag reduction mechanism according to claim 1, characterized in that the pipeline to be tested is surrounded by an upper wall, two side walls and a lower wall, and the upper wall and the two The two side walls are detachably connected, and the lower wall and the two side walls are also detachably connected. 4. A test device for exploring surface drag reduction mechanism according to claim 1, characterized in that the third transportation pipe is connected to the pipe to be tested through a joint, and the third transportation pipe is a round pipe, The pipe to be tested is a square pipe, and the cross-sectional area of the inner cavity of the third delivery pipe is larger than the cross-sectional area of the inner cavity of the pipe to be tested. 5. A test device for exploring surface drag reduction mechanism according to claim 1, characterized in that a bubble isolation net is provided in the water storage tank to remove bubbles flowing into the water storage tank. 6. A test method for exploring the surface drag reduction mechanism using the test device according to any one of claims 1 to 5, characterized in that it includes the following steps: a. Select the pipeline to be tested without drag reduction treatment and connect it to the second transportation pipeline and the third transportation pipeline; b. Turn on the peristaltic pump and adjust the fluid flow rate to make the fluid flow in the pipeline to be tested smooth and even; c. Turn on the PIV measuring instrument, measure the velocity field of the fluid in the pipeline to be tested, and transmit the velocity field data to the computer receiving and processing system; d. Turn on the Micro-PIV measuring instrument, measure the velocity field of the fluid close to the inner wall of the pipe to be tested, and transmit the velocity field data to the computer receiving and processing system; e. Use two pressure sensors to measure the pressure at both ends of the pipeline to be tested, and transmit the data to the computer receiving and processing system; f. Use the computer receiving and processing system to process the received data to obtain the drag reduction effect, flow field velocity distribution and vortex structure under the current fluid flow rate; g. Perform drag reduction treatment on the pipeline to be tested in step a, and then connect it to the second transportation pipeline and the third transportation pipeline; h. Repeat steps b to f; i. Obtain drag reduction rate DR: Among them, ΔP _none is the pressure difference at both ends of the pipeline to be tested without drag reduction treatment, and ΔP is the pressure difference at both ends of the pipeline to be tested with drag reduction treatment. 7. The test method according to claim 6, characterized in that the drag reduction treatment in step g includes arranging micro-texture, arranging flexible surface, arranging polymer coating and/or arranging micro-texture on the inner wall surface of the pipeline to be tested. Input bubble.