A simulation calculation equivalent method for gravity deep-water cage I-frame

Abstract

The present invention discloses a method for simulating and calculating an equivalent I-frame of a gravity-type deepwater cage, comprising: S1, establishing a three-dimensional refined finite element model of the I-frame of the gravity-type deepwater cage; S2, conducting finite element analysis to calculate the mechanical responses of the I-frame of the gravity-type deepwater cage under tensile load and torsional load, respectively, to obtain a tension-displacement curve under tensile load and a torque-angle curve under torsional load; S3, calculating the equivalent tensile stiffness and equivalent torsional stiffness of the I-frame; S4, equating the I-frame to a solid rod and calculating the tensile stiffness and torsional stiffness of the solid rod; S5, based on the principle of stiffness equivalence, equating the equivalent tensile stiffness and equivalent torsional stiffness of the I-frame obtained in step S3 with the tensile stiffness and torsional stiffness of the solid rod obtained in step S4, to obtain an equivalent cross-sectional radius and an equivalent elastic modulus of the equivalent solid rod. The present invention improves the accuracy of simulation calculations of gravity-type deepwater cages.

Description

Technical Field

[0001] The invention relates to a gravity-type deep-water cage I-frame simulation calculation equivalent method. Background Art

[0002] Gravity deep-water cages will continue to be an important facility supporting the development of marine aquaculture in the future. Gravity deep-water cages are mainly composed of a floating frame system, a net system and an anchoring system. Figure 1 As shown, the I-frame 1 is an important component connecting the inner floating pipe 2 and the outer floating pipe 3 in the gravity deep-water cage floating frame system. During the hydrodynamic simulation calculation, it is limited by the current calculation methods and is generally simplified into a rod or beam. However, most of the current simplification methods still simplify it into a rod or beam structure with the same specifications as the inner and outer floating pipes. There is no accurate and effective equivalent means, which is inconsistent with the actual situation and will affect the accuracy of the gravity deep-water cage simulation calculation to a certain extent. Summary of the Invention

[0003] The object of the present invention is to provide an equivalent method for simulation calculation of an I-frame of a gravity-type deep-water cage, which can improve the simulation calculation accuracy of the gravity-type deep-water cage.

[0004] The purpose of the present invention is achieved by the following technical measures: a gravity-type deep-water cage I-frame simulation calculation equivalent method, characterized by comprising the following steps:

[0005] S1. Establish a three-dimensional refined finite element model of the gravity deepwater cage I-frame;

[0006] S2. Conduct finite element analysis to calculate the mechanical response of the gravity deepwater cage I-frame under tensile load and torsional load, and obtain the tension-displacement curve under tensile load and the torque-angle curve under torsional load;

[0007] S3. Calculate the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-frame: PL = Ten / ε / L, PN = Tor / θ / L, where L is the length of the I-frame, Ten is the tension, ε is the displacement, Tor is the torque, and θ is the angle of rotation;

[0008] S4. Treat the I-beam as a solid member and calculate the tensile stiffness BL and torsional stiffness BN of the solid member: BL = EπR 2 , BN=EπR 4 / 5.6, where E is the elastic modulus of the solid rod and R is the cross-sectional radius of the solid rod;

[0009] S5. Based on the stiffness equivalence principle, the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-beam obtained in step S3 are equivalent to the tensile stiffness BL and torsional stiffness BN of the solid rod obtained in step S4, that is, PL=BL, PN=BN, to obtain the equivalent cross-sectional radius and equivalent elastic modulus of the equivalent solid rod.

[0010] The present invention takes into account the actual structural dimensions of the I-frame of the deep-water cage, fills the gap in the current lack of accurate and effective means for the I-frame, and improves the simulation calculation accuracy of the gravity-type deep-water cage. The present invention is suitable for the simulation calculation of gravity-type deep-water cages of different specifications containing an I-frame structure, and has good engineering application value.

[0011] Step S2 of the present invention includes:

[0012] (1) Establish the first control point and the second control point at the center point of the floating pipe inside the I-shaped frame and the center point of the floating pipe outside the I-shaped frame respectively;

[0013] (2) Establish coupling connections between the first control point and the inner wall of the I-shaped frame contacted by the inner floating tube, and between the second control point and the inner wall of the I-shaped frame contacted by the outer floating tube, and couple all degrees of freedom;

[0014] ⑶ Set the boundary of the first control point as a fixed constraint, set the boundary of the second control point as a free boundary without constraint, and apply tensile and torsional loads at the second control point as required to complete the I-frame simulation calculation.

[0015] In the step (2) of the present invention, before the I-frame model is meshed, a coupling connection is established between the first control point and the inner wall of the I-frame where the inner floating tube contacts the geometry, and a coupling connection is established between the second control point and the inner wall of the I-frame where the outer floating tube contacts the geometry. Alternatively, after the I-frame model is meshed, a coupling connection is established between the first control point and the grid node of the inner wall of the I-frame where the inner floating tube contacts the geometry, and a coupling connection is established between the second control point and the grid node of the inner wall of the I-frame where the outer floating tube contacts the geometry.

[0016] Compared with the prior art, the present invention has the following significant effects:

[0017] (1) The present invention takes into account the actual structural dimensions of the I-frame of the deep-water cage, fills the gap in the current lack of accurate and effective means for the I-frame, and improves the simulation calculation accuracy of the gravity-type deep-water cage.

[0018] (2) The present invention is applicable to the simulation calculation of gravity deep-water cages of different specifications with I-frame structures, and has good engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1It is a structural diagram of a gravity-type deep-water cage floating frame system;

[0021] Figure 2 It is the overall flow chart of the present invention;

[0022] Figure 3 It is a flowchart of the present invention for establishing a three-dimensional refined finite element model of an I-shaped frame;

[0023] Figure 4 Schematic diagram of the I-frame control points and the contact of the floating tube with the inner wall of the gravity-type deepwater cage of the present invention;

[0024] Figure 5 It is a front view of a computing example of the present invention;

[0025] Figure 6 is a top view of a calculation example of the present invention;

[0026] Figure 7 This is a three-dimensional refined finite element model of a C90 gravity deepwater cage I-frame used as a calculation example in the present invention;

[0027] Figure 8 Schematic diagram of the reference point of the calculation example of the present invention and the coupling connection between the inner and outer walls of the inner and outer main floating tubes;

[0028] Figure 9 is a tension (Ten)-displacement (ε) curve of a calculation example of the present invention;

[0029] Figure 10 1 is a torque (Tor)-rotation angle (θ) curve diagram of a calculation example of the present invention.

[0030] In the figure: 1, I-frame, 2, inner floating tube, 3, outer floating tube, 4, second control point, 5, first control point, 6, outer floating tube contacts the inner wall of the I-frame, 7, inner floating tube contacts the inner wall of the I-frame, RP-1, first control point, RP-2, second control point. DETAILED DESCRIPTION

[0031] The present invention is further illustrated below through the description of specific implementation methods, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of the present invention, but as long as they do not deviate from the basic idea of the present invention, they are all within the scope of protection of the present invention.

[0032] like Figure 2 As shown in FIG. 1 , a gravity-type deepwater cage I-frame simulation calculation equivalent method of the present invention comprises the following steps:

[0033] S1. Establish a three-dimensional refined finite element model of the gravity deepwater cage I-frame;

[0034] S2. Conduct finite element analysis to calculate the mechanical response of the gravity deepwater cage I-frame under tensile load and torsional load, and obtain the tension (Ten)-displacement (ε) curve under tensile load and the torque (Tor)-rotation angle (θ) curve under torsional load;

[0035] like Figure 3 As shown, step S2 specifically includes:

[0036] (1) Establish the first control point 5 and the second control point 4 at the center of the inner and outer floating tubes of the I-shaped frame, wherein the first control point 5 is located at the center of the inner floating tube 2, and the second control point 4 is located at the center of the outer floating tube 3. Figure 4 ;

[0037] ⑵See Figure 4 , a first control point 5 establishes a coupling connection with the inner wall 7 of the I-frame in contact with the inner floating tube, coupling all degrees of freedom, and establishing a geometric coupling connection between the first control point 5 and the inner wall 7 of the I-frame in contact with the inner floating tube before the I-frame model is meshed, or establishing a coupling connection between the first control point 5 and the mesh nodes of the inner wall 7 of the I-frame in contact with the inner floating tube after the I-frame model is meshed; a second control point 4 establishes a coupling connection with the inner wall 6 of the I-frame in contact with the outer floating tube, coupling all degrees of freedom, and establishing a geometric coupling connection between the second control point 4 and the inner wall 6 of the I-frame in contact with the outer floating tube before the I-frame model is meshed, or establishing a coupling connection between the second control point 4 and the mesh nodes of the I-frame in contact with the outer floating tube;

[0038] ⑶ Set the boundary of the first control point 5 as a fixed constraint, that is, U1=U2=U3=UR1=UR2=UR3=0 (constrain all degrees of freedom), set the boundary of the second control point 4 as a free boundary without constraints, and apply tensile, torsion and other loads at the second control point 4 as required to complete the I-frame simulation calculation.

[0039] S3. Calculate the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-frame: PL = Ten / ε / L, PN = Tor / θ / L, where L is the length of the I-frame, Ten is the tension, ε is the displacement, Tor is the torque, and θ is the angle of rotation;

[0040] S4. Treat the I-beam as a solid member and calculate the tensile stiffness BL and torsional stiffness BN of the solid member: BL=EπR 2 , BN=EπR 4 / 5.6, where E is the elastic modulus of the solid rod and R is the cross-sectional radius of the solid rod;

[0041] S5. Based on the stiffness equivalence principle, the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-beam obtained in step S3 are equivalent to the tensile stiffness BL and torsional stiffness BN of the solid rod obtained in step S4, that is, PL=BL, PN=BN, to obtain the equivalent cross-sectional radius and equivalent elastic modulus of the equivalent solid rod.

[0042] Examples

[0043] Take the I-shaped frame of a C90 gravity deep-water cage with a circumference of 90m as an example. Figure 5 、 6 As shown, the dimensions of the I-beam are as follows:

[0044] parameter value parameter value Length L 710mm Outer float tube diameter D2 408mm Width W 220mm Wall thickness T 20mm Internal floating tube diameter D1 408mm *** ***

[0045] (Table 1)

[0046] S1. Based on the general finite element analysis software ABAQUS, according to the I-frame parameters in Table 1, the I-frame geometric model was established. The mesh type was C3D4, the mesh scale was 10 mm, and the finite element mesh was divided to establish the three-dimensional refined finite element model of the C90 gravity deepwater cage I-frame. Figure 7 As shown;

[0047] S2. Establish a first control point RP-1 at the center of the inner floating tube of the I-frame, and establish a second control point RP-2 at the center of the outer floating tube of the I-frame. The first control point RP-1 is coupled to the inner floating tube contacting the inner wall 7 of the I-frame, and the second control point RP-2 is coupled to the outer floating tube contacting the inner wall 6 of the I-frame. In this example, the coupling method adopts the geometric coupling connection method between the control point and the inner wall of the I-frame, such as Figure 8 As shown;

[0048] The boundary of the first control point RP-1 is set as a fixed constraint, and the boundary of the second control point RP-2 is set as a free boundary without constraints. Then, in this example, a tensile load (0-10kN) and a torsional load (0-10kN·m) are applied at the second control point RP-2 to calculate the mechanical response of the gravity deepwater cage I-frame.

[0049] After the calculation is completed, the displacement and rotation angle of the second control point RP-2 are extracted to obtain the corresponding tension (Ten)-displacement (ε) curve (such as Figure 9 As shown in the figure) and the torque (Tor)-angle (θ) curve (as shown in the figure) Figure 10 shown);

[0050] S3. Calculate the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-beam frame, where PL = Ten / ε / L and PN = Tor / θ / L, where L is the length of the I-beam frame. Based on the simulation results, the equivalent stiffness values of the I-beam frame are as follows:

[0051] Tensile stiffness: PL = Ten / ε / L = 14915.97 kN (Equation 1)

[0052] Torsional stiffness: PN = Tor / θ / L = 76.34 kN m 2 (Equation 2)

[0053] S4. Calculation of tensile and torsional stiffness of solid rods: The calculation formula for the tensile stiffness BL and torsional stiffness BN of solid rods is: BL=EπR 2 , BN=EπR 4 / 5.6, where E is the elastic modulus of the solid rod and R is the cross-sectional radius of the solid rod. If the I-beam is equivalent to a solid rod (radius R, elastic modulus E), then:

[0054] Tensile stiffness: BL=EπR 2 (Equation 3)

[0055] Torsional stiffness: BN=EπR 4 / 5.6 (Equation 4)

[0056] S5. Calculation of equivalent solid rod geometry and material parameters: Based on the stiffness equivalence principle, the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-beam are equivalent to the tensile stiffness BL and torsional stiffness BN of the solid rod, that is:

[0057] PL=BL (Equation 5)

[0058] PN=BN (Formula 6)

[0059] By combining (Equation 1) to (Equation 6), we can calculate the equivalent cross-sectional radius R and equivalent elastic modulus E of the equivalent solid rod, and obtain: E=166.24MPa, R=0.169m, that is, after the I-beam is equivalent, the elastic modulus E of the equivalent solid rod is 166.24MPa, and the cross-sectional radius R is 0.169m.

[0060] At this point, the equivalent calculation of a C90 type gravity deep-water cage I-frame equivalent to a solid rod in this example is completed.

[0061] The present invention belongs to the field of fishery breeding facilities. By constructing a three-dimensional refined finite element model of a deep-water cage I-frame, its mechanical response under tensile and torsional loads is calculated, and the tension-displacement curve and torque-angle curve are obtained. By calculating the equivalent tensile stiffness and torsional stiffness, based on the stiffness equivalence principle, the cage I-frame is equivalent to an equal-length solid rod, and its equivalent geometry (radius) and material parameters (elastic modulus) are calculated. This method takes into account the actual structural dimensions of the deep-water cage I-frame, fills the gap in the current lack of accurate and effective means for I-frames, and improves the accuracy of gravity-type deep-water cage simulation calculations. This method is applicable to the simulation calculation of gravity-type deep-water cages of different specifications containing I-frame structures, and has great engineering application value.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A gravity-type deepwater cage I-frame simulation calculation equivalent method, characterized by The following steps are involved: S1. Establish a three-dimensional refined finite element model of the gravity deepwater cage I-frame; S2. Conduct finite element analysis to calculate the mechanical response of the gravity deepwater cage I-frame under tensile load and torsional load, and obtain the tension-displacement curve under tensile load and the torque-angle curve under torsional load; S3. Calculate the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-beam: PL = Ten / ε / L, PN = Tor / θ / L, where L is the length of the I-beam, Ten is the tension, ε is the displacement, Tor is the torque, and θ is the angle of rotation; S4. Treat the I-beam as a solid member and calculate the tensile stiffness BL and torsional stiffness BN of the solid member: BL = EπR 2 , BN=EπR 4 / 5.6, where E is the elastic modulus of the solid rod and R is the cross-sectional radius of the solid rod; S5. Based on the principle of stiffness equivalence, the equivalent tensile stiffness PL and equivalent torsional stiffness PN of the I-beam obtained in step S3 are equivalent to the tensile stiffness BL and torsional stiffness BN of the solid rod obtained in step S4, that is, PL=BL, PN=BN, to obtain the equivalent cross-sectional radius and equivalent elastic modulus of the equivalent solid rod.

2. The equivalent method for simulating and calculating the gravity-type deepwater cage I-frame according to claim 1, characterized in that: Step S1 includes: based on finite element analysis software and according to the I-frame parameters, establishing an I-frame geometric model and dividing the finite element grid, and establishing a three-dimensional refined finite element model of the gravity deepwater cage I-frame.

3. The equivalent method for simulating and calculating the gravity-type deepwater cage I-frame according to claim 2, characterized in that: The step S2 comprises: (1) Establish the first control point and the second control point at the center point of the floating pipe inside the I-shaped frame and the center point of the floating pipe outside the I-shaped frame respectively; (2) Establish coupling connections between the first control point and the inner wall of the I-shaped frame contacted by the inner floating tube, and between the second control point and the inner wall of the I-shaped frame contacted by the outer floating tube, and couple all degrees of freedom; ⑶ Set the boundary of the first control point as a fixed constraint, set the boundary of the second control point as a free boundary without constraint, and apply tensile and torsional loads at the second control point as required to complete the I-frame simulation calculation.

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