A fluid dynamic capture method based on vortex-induced vibration

Abstract

The present invention discloses a fluid dynamics capture method based on vortex-induced vibration, which belongs to the field of fluid dynamics capture. First, three-dimensional modeling is performed according to the design file of the supporting structure of the power generation device to obtain the internal flow channel model of the supporting structure; the flow field in the flow channel is calculated by using computational fluid dynamics software, and the flow field in the flow channel is visualized through post-processing to determine the vortex distribution and Reynolds value in the flow channel; on this basis, a circuit module that can convert alternating current into direct current is designed, so that when water flows into the power generation device, the flow velocity is adjusted through a double-layer orifice plate, which can make the round rod vibrate up and down and maintain a large amplitude, drive the magnet rod to cut the magnetic flux lines, so that the magnetic flux lines generate alternating current, and generate direct current through the circuit module, which flows into the battery. The present invention effectively avoids many disadvantages of traditional turbines, is simple and easy to use, greatly simplifies the experimental design process, and opens up a new path for fluid dynamics capture methods.

Description

Technical Field

[0001] The invention belongs to the field of fluid dynamics capture, and in particular relates to a fluid dynamics capture method based on vortex-induced vibration. Background Art

[0002] At present, my country's hydropower generation is mainly based on large-scale turbine units, which have many restrictions and defects. For example, the normal operation of the unit has strict requirements on water flow rate and load, the impeller blades are seriously worn by sediment, maintenance is difficult, and the impact on the ecological environment is huge. Although the application of turbines is relatively mature, most of the defects are still difficult to overcome, which seriously hinders the further development of fluid power resources. Changing the traditional form of turbine power generation and expanding the way of obtaining fluid energy will undoubtedly bring huge benefits.

[0003] Karman vortex street phenomenon can be seen everywhere in fluid. Under certain conditions (60 <Re<510 3 ) When the steady flow of water passes by certain objects, double-row line vortices with opposite rotation directions and regular arrangement will be periodically shed on both sides of the object, accompanied by acoustic effects, resonance effects and other phenomena. When the vortices of the Karman vortex street are shed, they will produce an impact force on the object flowing around, causing it to vibrate and reach the maximum amplitude under certain conditions. Converting the mechanical energy generated by this vortex-induced vibration into usable electrical energy can effectively avoid many disadvantages of traditional turbines and realize a new type of utilization of fluid power.

[0004] Finite element analysis is to decompose an object or system into a geometric model composed of multiple interconnected, simple, and independent points, and use a finite number of unknown quantities to approximate a real system with infinite unknown quantities. Finite element analysis not only has high calculation accuracy, but also can adapt to various complex shapes, so it is widely used in the field of engineering analysis. Applying the finite element analysis method to the study of vortex-induced vibration hydropower generation can simplify theoretical calculations, efficiently process data, and obtain reliable calculation results. Through numerical simulation of the flow field based on the finite element analysis method, the vorticity magnitude and flow velocity distribution in the power generation device can be obtained, so as to optimize the device parameters and effectively verify the power generation effect. Summary of the invention

[0005] The purpose of the present invention is to solve the defects in the prior art and provide a fluid dynamic capture method based on vortex-induced vibration.

[0006] The specific technical solutions adopted by the present invention are as follows:

[0007] The present invention provides a fluid dynamic capture method based on vortex-induced vibration, which is as follows:

[0008] S1: According to the design file of the power generation device, a three-dimensional structural model of the support structure in the power generation device is constructed by three-dimensional modeling software, and then a support structure entity model is established according to the three-dimensional structural model; according to the internal flow channel of the support structure entity model, an internal flow channel model of the support structure is extracted; through meshing software, the internal flow channel model is discretized into a first internal flow channel mesh model; according to the design file, the inlet and outlet boundary conditions of the first internal flow channel mesh model are set by computational fluid dynamics software, and at the same time, the entire space occupied by the model is assigned fluid properties according to the design file to obtain a second internal flow channel mesh model;

[0009] S2: Select the corresponding turbulence model in transient state through computational fluid dynamics software; set the parameters of the turbulence model and perform calculation under the conditions of the sand content (referring to the sand content in the water body entering the power generation device) and flow rate (referring to the flow rate of the water body entering the power generation device) given by the working environment, and stop the calculation after observing the image of vortex shedding; select the solution animation in the solution, select the vorticity magnitude in the speed, take the longitudinal section of the second internal flow channel grid model as the object, and draw the vorticity magnitude cloud map at the longitudinal section; judge the vibration frequency, vibration amplitude and viscous force (including the viscous force magnitude in the x-direction and the y-direction) of the object flowing around under vortex-induced vibration according to the vortex magnitude cloud map;

[0010] S3: Determine whether the Reynolds number Re of the monitoring point in the vorticity magnitude cloud map is between (2 and 4)×10 4 <Re<(1~2)×10 5 In actual use, the severity of the vortex street in the vorticity magnitude cloud map can also be judged at the same time:

[0011] If the vortex street changes are not obvious on the vortex magnitude cloud map or the Reynolds number Re of the monitoring point on the vortex magnitude cloud map is ≤ (2~4)×10 4 , then reduce the distance between the objects flowing around in the second internal flow channel grid model obtained in step S1, and then repeat steps S1 to S3 based on the second internal flow channel grid model to determine whether the Reynolds number is within the specified range;

[0012] If the vortex street changes are not obvious on the vortex magnitude cloud map or the Reynolds number Re of the monitoring point on the vortex magnitude cloud map is ≥ (1~2)×10 5 , then reduce the inlet flow velocity of the second internal flow channel grid model obtained in step S1, and then repeat steps S1 to S3 based on the second internal flow channel grid model to determine whether the Reynolds number is within the specified range;

[0013] If the vortex street in the vortex magnitude cloud map changes significantly and the Reynolds number Re of the monitoring point in the vortex magnitude cloud map is within the specified range, directly proceed to step S4;

[0014] S4: according to the inlet flow velocity of the second internal flow channel grid model obtained after optimization in step S3, a control system is designed and negative feedback control is performed to control the average flow velocity of the second internal flow channel grid model obtained after optimization so that the error between the average flow velocity and the inlet flow velocity is within 1 m / s (without taking the endpoint value);

[0015] S5: Use the energy recovery unit and the secondary filter unit of the power module in the design document to integrate the current generated by the vibration of different objects around the flow, and convert the irregular alternating current into direct current;

[0016] S6: according to the second internal flow channel grid model obtained by optimizing step S3, a three-dimensional structure optimization model of the support structure is obtained; a flow object is placed in the three-dimensional structure optimization model, so that the length direction of the flow object is perpendicular to the water flow direction, and a vibration margin is reserved for the flow object in a direction perpendicular to both the length direction of the flow object and the water flow direction, and the vibration margin is greater than or equal to twice the equivalent diameter of the cross section of the flow object; according to the design document, a first orifice plate is fixedly covered on the inlet surface of the three-dimensional structure optimization model, and a second orifice plate with the same structure is movably connected to the outer side surface of the first orifice plate, and the opening of the inlet surface can be changed by moving the second orifice plate;

[0017] S7: Based on the structure obtained in step S6, a transmission connector is used to connect adjacent objects around the flow in a direction perpendicular to the water flow, and a rigid connector is used to connect adjacent objects around the flow in a direction parallel to the water flow; a magnet bar arranged perpendicular to the water flow direction is fixed on the rigid connector;

[0018] The second orifice plate is connected with a stepper motor in the control system, and the control system is installed on the support structure; based on the control system obtained in step S4 and performing negative feedback control, the throttling area is changed by adjusting the second orifice plate so that the error between the average flow velocity inside the support structure and the inlet flow velocity is within 1 m / s. The flow velocity is kept within the optimized range, so that the flow around the object can maintain a higher amplitude, thereby increasing the power generation and increasing the amount of fluid power captured.

[0019] The magnetic coil of the supporting structure is connected to the power module, and the transmission connecting part drives the flow-around object to vibrate through vortex-induced vibration, while driving the rigid connecting part to cut the magnetic coil to convert alternating current into direct current. The obtained direct current is stored in the battery to complete fluid dynamics capture.

[0020] Preferably, the design file includes drawings of the supporting structure of the power generation device, a control module scheme and a power module design scheme; wherein the control module scheme includes a hardware wiring diagram and a driver program, and the power module design scheme includes a circuit construction diagram of an energy recovery unit and a secondary filter unit.

[0021] Preferably, the steps of designing a control system and performing negative feedback control in step S4 are specifically as follows:

[0022] S41: Use the main control chip, voltage-stabilized power supply module, motor drive module, flow rate sensor and stepper motor in the design document to build a control system;

[0023] S42: Write a driver program in the main control chip so that the main control chip can drive the stepper motor, read the flow rate sensor signal, and communicate with the host computer through the serial port; the driver program includes a first sub-driver program that can perform mean filtering on the flow rate data read from the flow rate sensor, a second sub-driver program that generates a control quantity u(k) through incremental PID control, and a third sub-driver program that can generate a specific PWM wave with a frequency proportional to the control quantity u(k).

[0024] Furthermore, the first sub-driver is specifically as follows:

[0025] After the first sub-driver performs (n+1) A / D conversions, it takes a weighted average of the data obtained from the (n+1) A / D conversions, and uses the average as the actual flow velocity measurement value at the current moment, that is:

[0026]

[0027] Where h(t) is the actual flow velocity measurement value at time t, f is the A / D conversion frequency, and g(t-iT) are the i-th conversion values ​​mentioned above, a i is the weighted average coefficient, satisfying And take a0>a1>...>a n-1 >a n .

[0028] Furthermore, the second sub-driver is specifically as follows:

[0029] The main program is in an infinite loop. The program will remember the difference between the actual flow rate measurement value and the optimal flow rate value obtained in the previous three cycles, e(k), e(k-1), e(k-2), and the control value u(k-1) obtained in the previous cycle, and use the formula Δu(k)=K P [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k-2)] calculates the control quantity increment Δu(k), and then uses the formula u(k)=u(k-1)+Δu(k) to update the control quantity u(k); where K P , K I , K Dare the proportional coefficient, integral coefficient, and differential coefficient respectively. u(k-1) is the actual flow velocity measured by the flow velocity sensor in the previous cycle. Δu(k) is the difference between the actual flow velocities measured by the flow velocity sensor in the previous cycle and this cycle. u(k) is the average flow velocity in the flow channel inside the support structure in this cycle.

[0030] Furthermore, the third sub-driver is specifically as follows:

[0031] A specific PWM wave with a frequency proportional to the control quantity u(k) is generated and output to the motor drive module to adjust the start, stop, direction and speed of the stepper motor; the position of the second orifice plate is adjusted by the stepper motor to change the opening, thereby adjusting the average flow rate in the supporting structure.

[0032] Furthermore, the main control chip adopts one of Arduino, stm32, and stc8051.

[0033] Preferably, the transmission connecting member is a spring.

[0034] Preferably, in step S1, when the structure of the power generation device is geometrically symmetrical relative to its longitudinal section, the three-dimensional structural model is a complete model or a 1 / 2 model relative to the longitudinal section; when the structure of the power generation device is geometrically asymmetrical relative to its longitudinal section, the three-dimensional structural model is a complete model; the inlet and outlet boundary conditions include one or more of pressure inlet boundary conditions, pressure outlet boundary conditions, velocity inlet boundary conditions and velocity outlet boundary conditions; before assigning fluid properties, if the three-dimensional structural model is a complete device model, a no-slip wall boundary condition is set at the location of the inner wall surface in the first internal flow channel grid model; if the three-dimensional structural model is a 1 / 2 model relative to the longitudinal section, a no-slip wall boundary condition is set at the location of the inner wall surface in the first internal flow channel grid model, and a symmetric boundary condition is set at the location of the longitudinal section.

[0035] Preferably, the 3D modeling software adopts one of Inventor, Solidworks, Creo, UG / NX, CATIA, ANSYS Workbench DesignModeler or ANSYS Workbench SpaceClaim; the meshing software adopts one of ICEM CFD, HyperMesh, TGrid, PointWise, ANSA, GridPro or ANSYS WorkbenchMesh; the computational fluid dynamics software adopts one of ANSYS CFX, ANSYS Fluent, STAR-CD, STAR-CCM, NUMECA or OpenFOAM; the turbulence model adopts one of Standard k-ε model, Spalart-Allmaras model, RNG k-ε model, Realizable k-ε model, Standard k-ω model, BSL k-ω model or SST k-ω model.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention realizes the simulation of the fluid dynamic capture process without repeated theoretical calculations and experimental corrections, which greatly simplifies the design process of the vortex-induced vibration power generation device.

[0038] (2) The present invention improves the pain points of traditional fluid dynamics capture methods. Relying on a small-scale bladeless vortex-induced vibration power generation mode, the construction cost is low, the threshold is low, the device is easy to install, easy to maintain, and has a long life cycle, effectively avoiding the various disadvantages of traditional turbines. The device is simple and easy to use, not only does it have no noise pollution, it will not affect the surrounding biological environment; the device has no requirements for the flow direction of the fluid, and can capture the mechanical energy of the fluid in all directions, thereby increasing the service life.

[0039] (3) The product of the present invention has strong expandability. After the traditional turbine is assembled, it is difficult to carry out subsequent transformation and expansion. However, the present device can not only be used in a small-scale distributed mode, but also can be used for large-scale series power generation. It can also be applied to different fluids by adjusting the parameters of the vibration column (such as damping, diameter-width ratio, spacing, etc.), and the expansion potential is very considerable.

[0040] (4) The scope of application of the present invention is greatly improved. The device has high energy density and a wide range of energy flow rates. It can generate electricity at a flow rate as low as 0.25m / s. In addition to industrial use, it can also be used in a variety of scenarios. For example, it can be distributed on the coast to provide power for street lights along the coast at all times, power river water monitoring devices, and power infrastructure in scenic spots around lakes around the clock. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The three-dimensional structural model (a), AA cross-sectional view (b) and BB cross-sectional view (c) of the device in Example 1;

[0042] Figure 2 The two-dimensional flow channel grid model established after simplifying the original three-dimensional structure model in Example 1;

[0043] Figure 3 is a vorticity magnitude cloud map of the original flow channel in Example 1;

[0044] Figure 4 is the modified two-dimensional flow channel grid model in Example 1;

[0045] Figure 5 This is a cloud diagram of the flow channel vortex magnitude after modification in Example 1;

[0046] Figure 6 The energy recovery circuit schematic diagram (a) and simulation effect diagram (b) in Example 1;

[0047] Figure 7 It is the principle diagram of the second-order RC low-pass filter in Example 1;

[0048] Figure 8 It is a block diagram of the control system in the embodiment;

[0049] Fig. 9 It is a flowchart of feedback control in the embodiment;

[0050] Fig.10 It is a flowchart of the feedback control in the embodiment;

[0051] Fig.11 The left view (a), front view (b) and top view (c) of the rigid connector. DETAILED DESCRIPTION

[0052] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0053] The present invention designs a fluid dynamics capture method based on vortex-induced vibration by simulating the flow field and analyzing the specific conditions of vortex-induced vibration, which is as follows:

[0054] S1: proceed in sequence according to steps 1) to 7), as follows:

[0055] 1) According to the design documents of the supporting structure of the power generation device, a three-dimensional structural model of the device is constructed by three-dimensional modeling software. In the process of constructing the three-dimensional structural model, when the structure of the supporting structure is geometrically symmetrical relative to its longitudinal section, the three-dimensional structural model is a complete model or a 1 / 2 model relative to the longitudinal section; when the structure of the supporting structure is geometrically asymmetrical relative to its longitudinal section, the three-dimensional structural model is a complete model. Among them, the longitudinal section of the supporting structure is a line connecting the center point of the inlet surface of the flow channel and the center point of the outlet surface and is perpendicular to the upper and lower edges of the inlet surface.

[0056] 2) Establish a supporting structure entity model based on the three-dimensional structural model. The established supporting structure entity model should be a complete model rather than a 1 / 2 model with the longitudinal section as the boundary.

[0057] 3) According to the internal flow channel of the supporting structure solid model, the internal flow channel model of the supporting structure is extracted. If a complete device model is used when constructing the three-dimensional structure model, the internal flow channel model constructed at this time is a three-dimensional geometric space structure surrounded by the inner wall surface of the device, the fluid inlet surface and the outlet surface. If the 1 / 2 with the longitudinal section as the boundary is used when constructing the three-dimensional structure model, the internal flow channel model constructed at this time is a three-dimensional geometric space structure surrounded by the inner wall surface of the device, the fluid inlet surface, the fluid outlet surface and the longitudinal section of the device, or a two-dimensional flow channel geometric structure on the longitudinal section of the device can also be constructed. Among them, the inner wall surface of the device refers to the contact surface between the inside of the device and the fluid; the fluid inlet surface refers to the dividing surface between the fluid flow space inside the device and the upstream water flow space; the fluid outlet surface refers to the dividing surface between the fluid flow space inside the device and the downstream water flow space.

[0058] 4) Importing the obtained internal flow channel model into meshing software, and discretizing it into a first internal flow channel mesh model.

[0059] 5) Importing the obtained first internal flow channel grid model into computational fluid dynamics software, and setting the inlet and outlet boundary conditions of the first internal flow channel grid model according to the original design file.

[0060] In this process, if the velocity value of the device inlet surface is specified in the document, a velocity inlet boundary condition is set for the fluid inlet surface, and the velocity value is the inlet velocity described in the design document.

[0061] 6) If a complete device model is used when constructing the three-dimensional structure model, a no-slip wall boundary condition is set at the location of the inner wall surface in the first internal flow channel grid model. If a 1 / 2 model with a longitudinal section as the boundary is used when constructing the three-dimensional structure model, a no-slip wall boundary condition is set at the location of the inner wall surface in the first internal flow channel grid model, and a symmetric boundary condition is set at the location of the longitudinal section.

[0062] 7) Assigning fluid properties to the entire space occupied by the first internal flow channel grid model processed by steps 5) and 6), wherein physical parameters such as fluid density and fluid viscosity values ​​are determined according to the original design file of the device, thereby obtaining a second internal flow channel grid model.

[0063] S2: Through computational fluid dynamics software, select the corresponding turbulence model in transient state and set the parameters to perform calculations until the image of vortex shedding is observed and stop the calculation; select the solution animation in the solution, select the vorticity level in the speed, take the longitudinal section of the obtained second internal flow channel grid model as the object, draw the vorticity level cloud map where the longitudinal section is located, and set a monitoring point in the center of the model to monitor the Reynolds number in the flow field; select a certain time step and number of time steps to perform calculations; after the calculation is completed, according to the vorticity level cloud map, judge the vibration frequency, vibration amplitude and viscous force of vortex-induced vibration and other indicators. Among them, the characteristics of the vortex street are that the characteristics on the vorticity level are line vortices with opposite rotation directions and regular arrangement, which are obviously different from the normal flow area and can be easily identified.

[0064] S3: Determine whether the intensity of the vorticity magnitude cloud map and the Reynolds number of the monitoring point are between (2 and 4)×10 4 <Re<(1~2)×10 5 within the specified range;

[0065] S4: If the vortex street changes are not obvious on the vortex magnitude cloud map or the Reynolds number of the monitoring point on the vortex magnitude cloud map is Re≤(2~4)×10 4 , then reduce the distance between the objects flowing around in the second internal flow channel grid model obtained in step S1, and then repeat steps S1 to S3 based on the second internal flow channel grid model to determine whether the Reynolds number is within the specified range;

[0066] If the vortex street changes are not obvious on the vortex magnitude cloud map or the Reynolds number Re of the monitoring point on the vortex magnitude cloud map is ≥ (1~2)×10 5 , then reduce the inlet flow velocity of the second internal flow channel grid model obtained in step S1, and then repeat steps S1 to S3 based on the second internal flow channel grid model to determine whether the Reynolds number is within the specified range;

[0067] S5: If the vortex street of the vortex magnitude cloud map changes significantly and the Reynolds number is within the specified range, no optimization is required and the next step is performed directly;

[0068] S6: Based on the optimal flow rate calculated above (i.e., the inlet flow rate of the second internal flow channel grid model obtained after optimization), a control module is designed to perform negative feedback control, so as to stabilize the internal flow rate (i.e., the average flow rate) of the obtained second internal flow channel grid model roughly around the optimal flow rate. Generally speaking, the average flow rate should be controlled so that the error between it and the inlet flow rate is within 1 m / s.

[0069] When in use, you only need to power on the hardware system, start Arduino, use the host computer to send the optimal flow rate to Arduino, and the program will automatically start executing. At this time, the actual flow rate can be monitored through the host computer;

[0070] S7: Use the energy recovery unit and the secondary filter unit of the power module in the design file to integrate the current generated by the vibration of different rods (i.e., the flow-around object) to convert irregular AC power into DC. During use, the energy recovery circuit unit and the secondary filter unit are coupled and used. The AC power output by the vortex-induced vibration is connected to the energy recovery circuit to obtain DC power, but the voltage ripple is large at this time. Then the output DC voltage is connected to the secondary filter circuit. After filtering, DC power with smaller ripple can be obtained, which meets the expected requirements;

[0071] S8: Select Arduino MEGA2560R3 main control chip, LM2596 voltage-stabilized power supply module, L298N motor driver module, YF-B5 flow rate sensor, 42 stepper motor and other hardware devices, and use DuPont wires for wiring to form the entire control system.

[0072] The specific connection rules are as follows: the AC power input terminal of the LM2596 voltage-stabilized power module is connected to the 220V AC mains, the 5V terminal of the DC power output terminal is connected to the power supply terminal of the Arduino MEGA2560R3, the power supply terminal of the L298N motor driver module, and the power supply terminal of the YF-B5 flow rate sensor, and the GND terminal of the DC power output terminal is connected to the GND terminal of the Arduino MEGA2560R3, the GND terminal of the L298N motor driver module, and the GND terminal of the YF-B5 flow rate sensor. The TX0 end of Arduino MEGA2560R3 is connected to the RX end of the host computer, the RX0 end is connected to the TX end of the host computer, the PWM1 port is connected to the control signal end IN1 of the L298N motor driver module, the PWM2 port is connected to the control signal end IN2 of the L298N motor driver module, the PWM3 port is connected to the control signal end IN3 of the L298N motor driver module, the PWM4 port is connected to the control signal end IN4 of the L298N motor driver module, and the A0 port is connected to the analog signal output end of the YF-B5 flow rate sensor. The OUT1 end of the L298N motor driver module is connected to the A+ end of the 42 stepper motor, the OUT2 end is connected to the A- end of the 42 stepper motor, the OUT3 end is connected to the B+ end of the 42 stepper motor, and the OUT4 end is connected to the B- end of the 42 stepper motor.

[0073] S9: Write a driver program in Arduino so that Arduino can normally drive the stepper motor, read the flow rate sensor signal, and communicate with the host computer through the serial port, as shown in steps S10 to S12.

[0074] S10: Introduce a mean filter. Perform a mean filter on the flow rate data read from the flow rate sensor. If the A / D conversion frequency of Arduino is 5000Hz, the program will take the weighted average of the data obtained from the 50 A / D conversions after every 50 A / D conversions, and use the average as the actual flow rate measurement value at the current moment. That is:

[0075]

[0076] Where, h(t) is the actual flow velocity measurement value at time t (current time), n is the filter window size minus 1, which is 49 here, and f is the A / D conversion frequency, which is 5000 Hz here. is the previous i-th conversion value, ai is the weighted average coefficient, where a0=a1=...=a9=0.035, a 10 =a 11 =... =a 19 =0.03, a 20 =a 21 =... =a 29 =0.02, a30 =a 31 =... =a 39 =0.01, a 40 =a 41 =... =a 49 =0.005;

[0077] S11: Introduce incremental PID control to generate control quantity u(k). The main program is in an infinite loop. The program will remember the difference between the actual flow rate measurement value and the optimal flow rate value obtained in the previous three cycles, e(k), e(k-1), e(k-2), and the control quantity u(k-1) obtained in the previous cycle, and use the formula Δu(k)=K P [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k-2)] calculates the control quantity increment Δu(k), and then uses the formula u(k)=u(k-1)+Δu(k) to update the control quantity u(k). Where K P , K I , K D They are proportional coefficient, integral coefficient and differential coefficient respectively, which can be adjusted according to the actual control effect. Here they are 1.25, 0.5 and 0.2 respectively.

[0078] S12: Generate a specific PWM wave with a frequency proportional to the control quantity u(k) (when u(k)=0, the output is low level), and output it to the L298N motor driver module to adjust the start, stop, direction and speed of the stepper motor. The stepper motor adjusts the position (opening) of the orifice plate, thereby adjusting the flow rate in the box.

[0079] S13: A vibrating round rod (i.e., a flow object) is placed in the support structure. The support structure is a rectangular block constructed of acrylic plates, with fluid inlets and outlets on both sides. The fluid inlet has a fixed orifice plate. The support structure has small holes on both sides above the fluid area for passing the magnet rod, and a magnetic coil is placed above these small holes. The length, width, and height of the support structure should be within 500 mm. The length direction of the round rod is perpendicular to the water flow direction, and sufficient vibration margin should be left for the round rod in the direction perpendicular to both the round rod direction and the water flow direction. The vibration margin should be greater than or equal to twice the equivalent diameter of the cross section of the flow object. The margin is left by placing two orifice plates with a certain distance inside the support structure parallel to the water flow direction. The position of the hole is the position of the round rod, and the shape of the hole is a straight groove. The direction of the groove is the vibration direction of the round rod, and the length of the groove is the vibration margin. This margin should be greater than twice the diameter of the round rod, the distance between the two orifice plates inside the support structure should be greater than or equal to 80% of the length of the round rod, the spacing between the centers of the round rods should also be greater than twice the diameter of the round rods, the diameter of the round rods should be within the range of 10 to 20 mm, and the number of round rods can be adjusted according to the specific size of the support structure, with a minimum of no less than 10 and a maximum of hundreds. The inlet surface of the power generation device needs to have a fixed first orifice plate, and there are guide rails on both sides of the outside of the inlet surface, and then another layer of movable second orifice plates will be inserted into the guide rails.

[0080] S14: There should be a transmission connection between the round rods. For example, the round rods can be connected with springs perpendicular to the water flow direction, and the round rods can be connected with rigid connectors parallel to the water flow direction. The rigid connector has a cylindrical groove facing upward (i.e., perpendicular to the water flow direction), and a magnet bar is placed in the groove so that the magnet bar cuts the magnetic coil fixed on the device when the round rod vibrates. The movable orifice plate is connected with a motor, and the control module is installed on the power generation device to monitor the flow rate of the water flowing into the device. When the flow rate deviates from the required optimal flow rate, the orifice plate is adjusted up and down by the motor to change the throttling area and adjust the flow rate. The coil is connected to the circuit module to convert AC into DC, and finally the DC current enters the battery to complete the fluid dynamic capture.

[0081] Example 1

[0082] S1: Figure 1 The figure shows the three-dimensional structure model of the device of this embodiment. Figure 1 It can be seen that the structure of the device is symmetrical about its longitudinal section, so a 1 / 2 device model symmetrical about the longitudinal section can be established. In the 3D modeling software, a solid model of the device is established. According to the internal flow channel of the solid model, it is simplified into a 2D internal flow channel mesh model. Through the meshing software, the internal flow channel model is discretized into an internal flow channel mesh model, and the area near the round rod is meshed, such as Figure 2As shown, it is an internal flow channel mesh model divided by ICEM, and there are two fluid regions with different mesh sizes;

[0083] The obtained internal flow channel grid model is imported into the computational fluid dynamics software FLUENT, and according to the design file, the velocity inlet boundary condition of the internal flow channel grid model is set to an inlet velocity of 3m / s. The no-slip wall boundary condition is set at the inner wall surface of the internal flow channel grid model, the interface condition between the two fluid regions with different grid sizes is set to match, and the symmetric boundary condition is set at the longitudinal section. The fluid properties are assigned to the entire space occupied by the internal flow channel grid model according to the design file;

[0084] S2: In the computational fluid dynamics FLUENT software, after selecting the corresponding turbulence model and setting the remaining parameters, set the solution animation of the solution to select the vorticity level in the velocity, save an image after each calculation, and then start the calculation. After a certain time step and number of time steps, after the calculation is completed, an animation is generated in the animation of the computational fluid dynamics FLUENT software;

[0085] S3: Figure 3 As shown, the calculated Re≈3×10 4 , within the specified range, but the Karman vortex street is not obvious and the change is not drastic, so it needs to be optimized. Without changing the diameter of the round rod, only changing its arrangement, reducing the spacing between the upper and lower round rods in the flow channel, the flow velocity is still 3m / s, and its internal flow channel model is as follows Figure 4 The vorticity level cloud diagram obtained after calculation of the modified flow channel model is shown in Figure 5 As shown, the Karman vortex street is obvious, and the optimization process is ended.

[0086] S4: Figure 6 The figure shows the energy recovery circuit and simulation effect diagram. The circuit only uses two diodes, three capacitors and two resistors to reduce the loss. Compared with the buck-boost circuit, the circuit can increase the voltage to 2 times without the need for external energy supply. Figure 7 The figure shows a second-order RC low-pass filter, which consists of two capacitors and two resistors. It has a simple structure. After passing through the filter, the current output is not only related to the input at the current moment, but also to the output at the previous two moments. Therefore, the output voltage ripple can be effectively reduced under high-frequency working conditions.

[0087] S5: Select Arduino MEGA2560R3 main control chip, LM2596 voltage regulator module, L298N motor driver module, YF-B5 flow sensor, 42 stepper motor and other hardware devices, and use DuPont wires for wiring to form the following Figure 8The entire control system is shown in the figure. The driver is written into Arduino so that Arduino can drive the motor normally, read the flow sensor signal, and communicate with the host computer through the serial port. Mean filtering and incremental PID control are introduced. Finally, the control quantity u(k) generates a specific PWM wave with a frequency proportional to it (when u(k) = 0, the output is low level), which is output to the L298N motor driver module to adjust the start, stop, direction and speed of the motor, forming the following Fig. 9 , Fig.10 The software system shown.

[0088] S6: Assemble the round rod, box, magnet bar, coil, spring and other parts to form Figure 1 In the model shown, the connection between the round rod and the magnet bar is as follows Fig.11 As shown, the two circular holes at the bottom are inserted into the vibrating round rods, the circular hole in the middle facing upward is inserted into the magnet rod, and the upper end of the magnet rod is inserted into the magnetic coil. When water flows into the device, it drives the round rod to vibrate, and the round rod drives the magnet rod to move up and down to cut the magnetic flux lines, causing the coil to generate unstable alternating current, which is converted into direct current through the energy recovery circuit and flows into the battery, completing the conversion of water energy into electrical energy.

[0089] The present invention effectively avoids many disadvantages of traditional water turbines, is simple and easy to use, has no noise pollution and will not affect the surrounding biological environment, avoids complex theoretical calculations and experimental corrections, greatly simplifies the experimental design process, and opens up a new path for fluid dynamics capture.

[0090] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A fluid dynamic capture method based on vortex-induced vibration, characterized in that: The details are as follows: S1: constructing a three-dimensional structural model of a supporting structure in the power generation device by using three-dimensional modeling software according to the design document of the power generation device, and then establishing a supporting structure entity model according to the three-dimensional structural model; and extracting an internal flow channel model of the supporting structure according to the internal flow channel of the supporting structure entity model; The internal flow channel model is discretized into a first internal flow channel grid model by using grid division software; according to the design file, the inlet and outlet boundary conditions of the first internal flow channel grid model are set by using computational fluid dynamics software, and at the same time, the fluid properties are assigned to the entire space occupied by the model according to the design file to obtain a second internal flow channel grid model; S2: Selecting a corresponding turbulence model in a transient state by using computational fluid dynamics software; setting parameters of the turbulence model and performing calculations under the conditions of the sand content and flow velocity given by the working environment, and stopping the calculations after observing the image of vortex shedding; taking the longitudinal section of the second internal flow channel grid model as the object, drawing a vorticity magnitude cloud map at the location of the longitudinal section; judging the vibration frequency, vibration amplitude and viscous force of the object flowing around under vortex-induced vibration according to the vortex magnitude cloud map; S3: Determine whether the Reynolds number Re of the monitoring point in the vorticity magnitude cloud map is between (2 and 4)×10 4 <Re<(1~2)×10 5 within the specified range; If the Reynolds number of the monitoring point in the vorticity magnitude cloud map is Re≤(2~4)×10 4 , then reduce the distance between the objects flowing around in the second internal flow channel grid model obtained in step S1, and then repeat steps S1 to S3 based on the second internal flow channel grid model to determine whether the Reynolds number is within the specified range; if the Reynolds number Re of the monitoring point in the vorticity magnitude cloud map is ≥ (1 to 2) × 10 5 , then reduce the inlet flow velocity of the second internal flow channel grid model obtained in step S1, and then repeat steps S1 to S3 based on the second internal flow channel grid model to determine whether the Reynolds number is within the specified range; if the Reynolds number Re of the monitoring point in the vorticity magnitude cloud map is within the specified range, directly proceed to step S4; S4: according to the inlet flow velocity of the second internal flow channel grid model obtained after the optimization in step S3, a control system is designed and a negative feedback control is performed to control the average flow velocity of the second internal flow channel grid model obtained after the optimization so that the error between the average flow velocity and the inlet flow velocity is within 1 m / s; S5: Use the energy recovery unit and the secondary filter unit of the power module in the design document to integrate the current generated by the vibration of different objects around the flow, and convert the irregular alternating current into direct current; S6: according to the second internal flow channel grid model obtained by optimizing step S3, a three-dimensional structure optimization model of the support structure is obtained; a flow object is placed in the three-dimensional structure optimization model, so that the length direction of the flow object is perpendicular to the water flow direction, and a vibration margin is reserved for the flow object in a direction perpendicular to both the length direction of the flow object and the water flow direction, and the vibration margin is greater than or equal to twice the equivalent diameter of the cross section of the flow object; according to the design document, a first orifice plate is fixedly covered on the inlet surface of the three-dimensional structure optimization model, and a second orifice plate with the same structure is movably connected to the outer side surface of the first orifice plate, and the opening of the inlet surface can be changed by moving the second orifice plate; S7: Based on the structure obtained in step S6, a transmission connector is used to connect adjacent objects around the flow in a direction perpendicular to the water flow, and a rigid connector is used to connect adjacent objects around the flow in a direction parallel to the water flow; a magnet bar arranged perpendicular to the water flow direction is fixed on the rigid connector; The second orifice plate is connected with a stepper motor in the control system, and the control system is installed on the support structure; based on the control system obtained in step S4, negative feedback control is performed, and the throttling area is changed by adjusting the second orifice plate so that the error between the average flow velocity inside the support structure and the inlet flow velocity is within 1 m / s; the magnetic coil of the support structure is connected to the power module, and the transmission connecting part drives the flow-around object to vibrate through vortex-induced vibration, and at the same time drives the rigid connecting part to cut the magnetic coil to convert alternating current into direct current, and the obtained direct current is stored in a battery to complete fluid dynamic capture.

2. The fluid dynamic capture method based on vortex-induced vibration according to claim 1 is characterized in that: The design documents include drawings of the supporting structure of the power generation device, a control module scheme and a power module design scheme; wherein the control module scheme includes a hardware wiring diagram and a driver program, and the power module design scheme includes a circuit construction diagram of an energy recovery unit and a secondary filter unit.

3. The fluid dynamic capture method based on vortex-induced vibration according to claim 1 is characterized in that: The steps of designing a control system and performing negative feedback control in step S4 are specifically as follows: S41: Use the main control chip, voltage-stabilized power supply module, motor drive module, flow rate sensor and stepper motor in the design file to build a control system; S42: Write a driver program in the main control chip so that the main control chip can drive the stepper motor, read the flow rate sensor signal, and communicate with the host computer through the serial port; the driver program includes a first sub-driver program that can perform mean filtering on the flow rate data read from the flow rate sensor, a second sub-driver program that generates a control quantity u(k) through incremental PID control, and a third sub-driver program that can generate a specific PWM wave with a frequency proportional to the control quantity u(k).

4. The fluid dynamic capture method based on vortex-induced vibration according to claim 3 is characterized in that: The first sub-driver program is specifically as follows: After the first sub-driver performs (n+1) A / D conversions, it takes a weighted average of the data obtained from the (n+1) A / D conversions, and uses the average as the actual flow velocity measurement value at the current moment, that is: Where, h(t) is the actual flow velocity measurement value at time t, f is the A / D conversion frequency, T is the A / D conversion period, and g(t-iT) are the i-th conversion values ​​mentioned above, a i is the weighted average coefficient, satisfying And take a0>a1>...>a n-1 >a n .

5. The fluid dynamic capture method based on vortex-induced vibration according to claim 3 is characterized in that: The second sub-driver is specifically as follows: The main program is in an infinite loop. The program will remember the difference between the actual flow rate measurement value and the optimal flow rate value obtained in the previous three cycles, e(k), e(k-1), e(k-2), and the control value u(k-1) obtained in the previous cycle, and use the formula Δu(k)=K P [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k-2)] calculates the control quantity increment Δu(k), and then uses the formula u(k)=u(k-1)+Δu(k) to update the control quantity u(k); where K P , K I , K D are the proportional coefficient, integral coefficient, and differential coefficient respectively. u(k-1) is the actual flow velocity measured by the flow velocity sensor in the previous cycle. Δu(k) is the difference between the actual flow velocities measured by the flow velocity sensor in the previous cycle and this cycle. u(k) is the average flow velocity in the flow channel inside the support structure in this cycle.

6. The fluid dynamic capture method based on vortex-induced vibration according to claim 3 is characterized in that: The third sub-driver program is specifically as follows: A specific PWM wave with a frequency proportional to the control quantity u(k) is generated and output to the motor drive module to adjust the start, stop, direction and speed of the stepper motor; the position of the second orifice plate is adjusted by the stepper motor to change the opening, thereby adjusting the average flow rate in the supporting structure.

7. The fluid dynamic capture method based on vortex-induced vibration according to claim 3 is characterized in that: The main control chip is one of Arduino, stm32 and stc8051.

8. The fluid dynamic capture method based on vortex-induced vibration according to claim 1, characterized in that: The transmission connecting member is a spring.

9. The fluid dynamic capture method based on vortex-induced vibration according to claim 1, characterized in that: In the step S1, when the structure of the power generation device is geometrically symmetrical relative to its longitudinal section, the three-dimensional structural model is a complete model or a 1 / 2 model relative to the longitudinal section; when the structure of the power generation device is geometrically asymmetrical relative to its longitudinal section, the three-dimensional structural model is a complete model; the inlet and outlet boundary conditions include one or more of the pressure inlet boundary conditions, the pressure outlet boundary conditions, the velocity inlet boundary conditions and the velocity outlet boundary conditions; before assigning the fluid properties, if the three-dimensional structural model is a complete device model, a no-slip wall boundary condition is set at the location of the inner wall surface in the first internal flow channel grid model; if the three-dimensional structural model is a 1 / 2 model relative to the longitudinal section, a no-slip wall boundary condition is set at the location of the inner wall surface in the first internal flow channel grid model, and a symmetric boundary condition is set at the location of the longitudinal section.

10. The fluid dynamic capture method based on vortex-induced vibration according to claim 1, characterized in that: The 3D modeling software adopts one of Inventor, Solidworks, Creo, UG / NX, CATIA, ANSYS Workbench Design Modeler or ANSYS Workbench Space Claim; the meshing software adopts one of ICEMCFD, HyperMesh, TGrid, PointWise, ANSA, GridPro or ANSYS Workbench Mesh; the computational fluid dynamics software adopts one of ANSYS CFX, ANSYS Fluent, STAR-CD, STAR-CCM, NUMECA or OpenFOAM; the turbulence model adopts one of Standard k-ε model, Spalart-Allmaras model, RNG k-ε model, Realizable k-ε model, Standard k-ω model, BSL k-ω model or SST k-ω model.

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