[0044]In order to make the technical solutions and advantages of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. And in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.
[0045]In the course of the invention, the inventor noticed that when a small boat was used to drag the model at a fixed speed to measure the hydrodynamic coefficient, the frontal area in the water could not be maintained, resulting in low accuracy of the measured hydrodynamic coefficient, which made the actual Engineering is misleading. At present, the method of connecting the four corners of the manifold model with springs is mainly used to measure the additional mass coefficient. This method is too cumbersome in the process of switching heave, sway, and sway.
[0046]In view of the above shortcomings, the embodiment of the present invention proposes a large-scale structure hydrodynamic coefficient measurement device and measurement method, which will be described in detail below.
[0047]Such asFigure 1 to Figure 3 Shows the structural schematic diagrams from different angles of one of the embodiments of the large-scale structure hydrodynamic coefficient measurement device of the present invention. In this embodiment, the device for measuring the hydrodynamic coefficient of a large structure of the present invention mainly includes: an experimental water tank 1, a supporting frame 2, a screw loading and driving assembly, and a measurement system. Among them, the design standard of the experimental water tank 1, generally the length and width of the experimental water tank 1 is 8 to 15 times the length and width of the manifold model, and the height is 4 to 8 times the manifold model. In a preferred embodiment, the length and width of the experimental water tank 1 are ten times the length and width of the manifold model 14 respectively, and the height of the experimental water tank 1 is five times the height of the manifold model 14. The main body of the supporting frame 2 is connected above the experimental water tank 1, and the supporting legs of the supporting frame 2 are located on both sides of the experimental water tank 1. Here, reserve enough water area to eliminate the influence of the water tank boundary on the test piece. The measurement system includes a strain gauge 13, a sensor and a data acquisition device (or called a data acquisition system). The data acquisition device is mainly responsible for the collection and storage of all experimental data.
[0048]In one embodiment, such asFigure 1 to Figure 3 As shown, the supporting frame 2 is mainly composed of four supporting legs, two cross beams 5, and two longitudinal beams forming a supporting body spanning the experimental water tank 1. The supporting body is located on both sides of the experimental water tank 1 in the length direction, and a reinforcing beam 3 is provided between the two supporting legs on both sides of the length direction. The supporting body is also provided with a supporting beam 6, the two ends of the supporting beam 6 are connected with moving wheels 7, and the two beams 5 of the supporting body are provided with guide rails for moving the moving wheels 7.
[0049]In one embodiment, such asFigure 1 to Figure 6As shown, both ends of the transverse screw 8 are connected to the longitudinal beams of the main body of the support frame 2 through the bearings 4. One end of the transverse screw 8 extends out of the corresponding longitudinal beam and then is connected to the transverse motor 10 through a reducer 16 (a two-stage gear reducer) device. The transverse screw 8 is connected with a transversely moving slider 17 which is fixedly connected to the middle of the supporting beam 6. A square tube 19 is connected to the middle of the supporting beam 6 through a connecting piece. The lower end of the vertical lead screw 12 in the tube barrel is connected to the manifold model 14 through a 90° rotatable structure 22 through a directional structure 20, a vertical boom 21. Driven by the transverse motor 10, the force of the transverse screw 8 causes the transversely moving slider 17 to move the manifold model 14 connected under the supporting beam 6 along the X direction.
[0050]In one embodiment, such asFigure 1 to Figure 6As shown, a strain gauge 13 is installed at the lower end of the vertical boom 21 near the manifold model 14. The main function of the strain gage 13 on the vertical boom 21 is to measure the force of the test piece during the X, Y, and Z direction translational movement in the experimental water tank 1 in the process of measuring the damping coefficient of the underwater manifold. This force condition includes frictional resistance and differential pressure resistance, collectively referred to as drag force.
[0051]In one embodiment, such asFigure 1 to Figure 6As shown, the lower end of the vertical boom 21 is connected to the manifold model 14 through a 90° rotatable structure 22. Therefore, it is only necessary to rotate the manifold model 14 by 90°, and then use the same method as measuring X-direction motion parameters. Can complete the movement parameter measurement in the Y direction.
[0052]In one embodiment, such asFigure 1 to Figure 6As shown, the square tube 19 is fixed on the supporting beam 6, the upper end of the vertical lead screw 12 is connected to a stepping motor 18, and the lower end is connected to a square directional structure 20. Under the driving action of the stepping motor 18, the vertical lead screw 12 works Longitudinal movement drives the square directional structure 20 to move in the square tube without rotation, ensuring that the manifold model 14 connected by the vertical boom 21 below only measures the movement parameters in the Z direction.
[0053]In a preferred embodiment, such asFigure 1 to Figure 3 As shown, both the vertical screw 12 and the transverse screw 8 adopt ball screws, which can minimize the influence of friction on the measurement results and improve the measurement accuracy. The bearing 4 preferably adopts a thrust ball bearing, which not only can better bear the weight of the manifold model 14, but can also prevent the manifold model 14 from turning over due to the rotation of the vertical screw 12 and the transverse screw 8 during the test.
[0054]In one embodiment, such asFigure 1 to Figure 3 As shown, the main components of the supporting frame 2, such as supporting legs, cross beams 5, longitudinal beams, reinforcing beams 3 and supporting beams 6, all use steel frames. The supporting legs, the cross beam 5, the longitudinal beam, and the reinforcing beam 3 are mutually fixed by welding to ensure stability. The supporting frame 2 and the supporting beam 6 are used to support and stabilize the horizontal and vertical ball screws. In addition to the transverse motor 10 and the stepping motor 18, the driving assembly also includes a motor driver 9 and a pulse generator 11. The motor driver 9 and the pulse generator 11 are arranged close to the transverse motor 10 and are located on the same side of the support frame 2. In addition, the motor driver 9 is also connected with a power supply 15 of the motor driver. The ball screw of the driving component causes the manifold model 14 to form translational motions in the X, Y, and Z directions in the experimental water tank 1 and provides power for the oscillation of the manifold model 14 in water and air. The basic working principle is: set a movement function v=cos(ωt) of manifold oscillation, and use the pulse generator 11 to send this movement law to the motor driver 9 in the form of a pulse signal, which drives the motor to rotate in the set direction For a fixed angle, the angular displacement can be controlled by controlling the number of pulses, and the speed and acceleration of the motor can be controlled by controlling the pulse frequency, so as to achieve the purpose of positioning and speed regulation.
[0055]On the other hand, the present invention also provides a method for measuring the hydrodynamic coefficient of a large structure. The method adopts a large-scale structure hydrodynamic coefficient measuring device as in any of the above embodiments.
[0056]In an embodiment, the method for measuring the hydrodynamic coefficient of a large structure includes the following steps:
[0057]Preparation before testing;
[0058]Measure through the experimental device and obtain the drag coefficients of the underwater manifold in the X, Y and Z directions according to Morrison's equation;
[0059]By giving a fixed transmission speed to the motor in the experimental device, the lead screw makes sinusoidal oscillation motion in a certain direction, the additional mass value is measured and the additional mass coefficient is calculated according to the formula.
[0060]In one embodiment, the pre-test preparation work in the measurement method of the present invention includes: connecting the test equipment in order, filling the water tank with water, and ensuring that the water surface is stationary without fluctuations. The acceleration sensor is fixed on the bottom of the manifold model 14 as required, and a force-measuring strain gauge 13 or sensor is installed on the vertical screw 12. The manifold model 14 is connected and suspended at the lower end of the vertical screw 12, the orientation and posture of the manifold model 14 are adjusted and then fixed to keep it stationary. Adjust the height from the bottom of the model to the water surface, try to ensure that the bottom of the test piece is parallel to the water surface, and finally turn on the dynamic signal analyzer to initialize. Then, the experimental manifold model 14 is lifted to the designated position of the support frame 2 in the vertical direction (or vertical direction), and after the measurement system is debugged normally, the experimental manifold model 14 is released.
[0061]In the embodiment of the present invention, the resistance coefficient of the manifold in the X direction, Y direction and Z direction is mainly measured. Taking the measurement of the resistance coefficient in the X direction as an example, the method for measuring the hydrodynamic coefficient of a large structure of the present invention will be specifically described.
[0062]In an embodiment, obtaining the resistance coefficient in the X direction mainly includes the following steps:
[0063]Set a fixed horizontal moving speed value Vr for the transverse screw 8, so that the manifold (ie manifold model 14) will move in the X direction with a constant value Vr in the water tank;
[0064]The total resistance F of the manifold in the X direction is measured by the strain gauge 13 on the screwDX , By measuring the size of the model to obtain the frontal area A of the manifold in the X directionp;
[0065]Through Morrison equation FDX =0.5ρCDX APV2rCalculate the resistance coefficient C in the X directionDX.
[0066]In one embodiment, when obtaining the resistance coefficient in the Y direction or the Z direction, the manifold model 14 is rotated 90° around the lead screw until the front flow surface becomes the Y direction or the Z direction, and then the resistance coefficient in the X direction is measured accordingly. Method to measure the drag coefficient in Y direction or Z direction.
[0067]In the measurement method of the present invention, the main measured parameter is not only the resistance coefficient of the manifold, but also the additional quality coefficient of the manifold. The following is an example of obtaining the additional quality factor in the Z direction. Obtaining the additional quality coefficient in the Z direction mainly includes two steps: one is to obtain the additional quality in the Z direction; the other is to obtain the additional quality coefficient of the manifold in the Z direction according to the additional quality in the Z direction obtained by measurement.
[0068]In an embodiment, obtaining the additional quality in the Z direction includes the following steps:
[0069]Set a fixed transmission speed to the stepper motor 18, so that the vertical lead screw 12 has a speed V in the vertical direction2= Asinωt sinusoidal oscillating motion, through the first-order derivation of the motion speed, the acceleration of the manifold in the Z direction is a2=Aωcosωt, where A is the maximum movement speed of the manifold, and ω is the oscillation frequency.
[0070]The total resistance F of the underwater manifold at different time t is measured in real time by the strain gauge on the screw2t, According to Newton’s second law F2t=m2t*a2tAnd manifold acceleration a2t=Aωcosωt, the additional mass m of the manifold at the corresponding time t can be obtained2t, That is, the additional quality value of the manifold at time t is obtained, and m corresponding to the time step Δt of several cycles is calculated2tAnd take the average value to obtain the additional quality value M of the manifold in the Z direction2t.
[0071]In one embodiment, the average additional quality value M2tDimensionless After processing, the additional mass coefficient of the manifold in the Z direction can be obtained, where ρ is the fluid density and V is the manifold volume.
[0072]In addition, the method corresponding to the Z direction can be used to measure the additional quality coefficient λ of the manifold in the X and Y directions.0And λ1.
[0073]Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and/or modifications falling within the scope of the present invention. Changes and/or modifications made according to the embodiments of the present invention shall be covered by the protection scope of the present invention. Inside.
