A method for calibrating a ship model in water

Abstract

The present invention relates to a method for calibrating a ship model in water, including a hull. A measuring beam is installed in the middle of the hull, and the measuring beam is connected to the inner wall of the hull through a supporting cross beam. The hull is of a segmented type. The calibration process includes the following steps: the first step is to determine the position where the weights are placed; the second step is to determine the position of the measuring section and the connection method of the strain gauges; the third step is to place the hull statically in a water tank; the fourth step is to obtain the mean value of the change in each strain signal; the fifth step is to calculate the coefficient to be calibrated for the nth measuring section. By calibrating the ship model in water, the calibration coefficient can better reflect the actual physical state. By calculation, the position where the weights are placed to make the draft change of each cross section of the ship model the same is obtained, and the weights are gradually loaded and unloaded at the corresponding positions to calibrate the ship model in the actual state. This method takes into account the influence of the deformation of the ship model after being launched into the water on the calibration coefficient, ensures the accuracy of the calibration in water, and further improves the accuracy of the wave load test.

Description

Technical Field

[0001] The present invention relates to the technical field of ship model wave load tests, and in particular to a method for calibrating a ship model in water. Background Art

[0002] When a ship sails in waves, it will bear large wave loads. Excessive wave loads pose a great threat to the hull structural strength. How to obtain reasonable wave loads for ship structure design to ensure the safety of ship navigation has always been the focus of attention of ship structure designers. The sectional hull model test is an important method for studying ship wave loads.

[0003] In the traditional ship model wave load test, before the ship model is launched into the water, the measuring beam is calibrated, and the ship model wave load is obtained according to the calibration coefficient and the strain signal of the measuring beam in the formal test. However, in fact, after the ship model is launched into the water, the initial state of the measuring beam will change, which will have a certain impact on the calibration coefficient. Summary of the Invention

[0004] The applicant of the present invention aims at the above-mentioned disadvantages in the existing production technology and provides a method for calibrating a ship model in water, so that the calibration coefficient of the measuring beam is more accurate and the wave load can be measured more precisely.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for calibrating a ship model in water, including a hull, a measuring beam is installed in the middle of the hull, the measuring beam is connected to the inner wall of the hull through a support cross beam, and the hull is sectional;

[0007] The calibration process includes the following steps:

[0008] The first step is to determine the position where the weights are placed:

[0009] Define a local coordinate system on the waterline plane of the hull, and the origin of the local coordinate system is O(0, 0);

[0010] The origin O of the local coordinate system is the intersection point of the hull cross-section where the stern seal plate of the hull is located, the longitudinal middle section of the hull, and the waterline plane. The positive direction of the X-axis is towards the bow of the ship, and the positive direction of the Y-axis points to the port side;

[0011] Determine the position where the weights are placed so that the draft change of each cross-section of the ship model is the same:

[0012] When calibrating the midship bending moment coefficient: the position where the weights are placed is at the centroid A0 of the waterline plane of the hull, A0 is located in the local coordinate system and the coordinates of A0 in the local coordinate system are (l0, 0);

[0013] When calibrating the mid-arch bending moment coefficient: The positions where the weights are placed are at B1 and B2 in the local coordinate system. The coordinates of B1 in the local coordinate system are (l1, 0), and the coordinates of B2 in the local coordinate system are (l2, 0), where l1 < l2;

[0014] When calibrating the torsion coefficient: The positions where the weights are placed are at C1 and C2 in the local coordinate system. And C1 and C2 are located in the first quadrant and the fourth quadrant of the local coordinate system respectively. The abscissa of C1 is l1, the abscissa of C2 is l2, the ordinates of C1 and C2 are equal in magnitude, opposite in sign, and the absolute value is l3;

[0015] l0 is: When calibrating the mid-sag bending moment coefficient, the X-direction coordinate of the weight in the local coordinate system;

[0016] l1 is: When calibrating the mid-arch bending moment coefficient, the X-direction coordinate of the tail weight in the local coordinate system;

[0017] l2 is: When calibrating the mid-arch bending moment coefficient, the X-direction coordinate of the bow weight in the local coordinate system;

[0018] l3 is: When calibrating the torsion coefficient, the absolute value of the Y-direction coordinates of the tail and bow weights in the local coordinate system;

[0019] The area of the ship's waterplane is A,

[0020]

[0021] In formula (1), x is the position variable in the X direction in the local coordinate system; f(x) represents the half waterline width at the X-direction coordinate x in the local coordinate system, and L is the total length of the ship's waterplane;

[0022] Δh is the increase in the ship's draft after placing a weight of mass m once when calibrating the mid-sag bending moment coefficient,

[0023]

[0024] ΔH is the increase in the ship's draft after placing a weight of mass 2m once when calibrating the mid-arch bending moment coefficient,

[0025]

[0026] In formulas (2) and (3), ρ is the density of water;

[0027] Second step, determine the position of the measurement section and the connection method of the strain gauges:

[0028] The measurement section is located at the ship's section. The number of measurement sections is N, and the label of the currently measured measurement section is n, where n is a natural number less than or equal to N;

[0029] L nis the X - direction coordinate of the nth measurement section in the local coordinate system;

[0030] Connect the strain gauges pre - pasted on the measuring beam (b) according to a certain bridge connection method;

[0031] Step 3: Place the hull statically in the water tank and connect the strain gauges and the dynamic strain gauge with measuring wires;

[0032] Step 4: Obtain the mean value of the change in each strain signal:

[0033] When calibrating the sagging bending moment coefficient: Gradually load weights of mass m at point A0 in the local coordinate system, and then gradually unload weights of mass m to obtain the mean value of the change in the vertical bending strain signal of the nth measurement section

[0034] When calibrating the hogging bending moment coefficient: Gradually load weights of mass m simultaneously at points B1 and B2 in the local coordinate system, and then gradually unload weights of mass m simultaneously to obtain the mean value of the change in the vertical bending strain signal of the nth measurement section

[0035] When calibrating the torsion coefficient: Gradually load weights of mass m simultaneously at points C1 and C2 in the local coordinate system, and then gradually unload weights of mass m simultaneously to obtain the mean value of the change in the torsional deformation strain signal of the nth measurement section

[0036] Step 5: Calculate the coefficient to be calibrated for the nth measurement section:

[0037] The sagging bending moment coefficient δ of the nth measurement section An :

[0038]

[0039] M An is the sagging bending moment of the nth measurement section;

[0040] The hogging bending moment coefficient δ of the nth measurement section Bn :

[0041]

[0042] M sn is the hogging bending moment of the nth measurement section;

[0043] The torsion coefficient δ of the nth measurement section Cn :

[0044]

[0045] Let \(T\) be the torque borne by the hull when weights of mass \(m\) are loaded on both the starboard and port sides once, and the torques borne by each measurement section of the hull are the same.

[0046] Its further technical solution lies in:

[0047] In the first step: When calibrating the midship bending moment coefficient, the placement position of the weights is obtained through calculation, and this position is the centroid \(A_0\) of the hull waterplane. The \(X\)-direction coordinate of the centroid \(A_0\) of the hull waterplane in the local coordinate system is \(l_0\).

[0048]

[0049] \(l_0\) is calculated through formula (7) to determine the placement position of the weights when calibrating the midship bending moment coefficient.

[0050] In the first step: \(l_1\) and \(l_2\) satisfy the following relationship:

[0051]

[0052] Then:

[0053] In formulas (8) and (9), \(l_1\) and \(l_2\) also need to satisfy \(l_1 \lt L_1\) and \(l_2 \gt L\). N ,

[0054] \(L_1\) is the \(X\)-direction coordinate of the first measurement section in the local coordinate system.

[0055] \(L\) N is the \(X\)-direction coordinate of the \(N\)th measurement section in the local coordinate system.

[0056] In the first step: \(l_3 \lt f(l_1)\) and \(l_3 \lt f(l_2)\).

[0057] \(f(l_1)\) is the half waterline width representing the \(X\)-direction coordinate \(l_1\) in the local coordinate system.

[0058] \(f(l_2)\) is the half waterline width representing the \(X\)-direction coordinate \(l_2\) in the local coordinate system.

[0059] Ensure that when calibrating the torsion coefficient, the weights can be placed within the ship width.

[0060] In the fifth step: The midship bending moment \(M\) of the \(n\)th measurement section An :

[0061] When \(L\) n is greater than \(l_0\),

[0062]

[0063] When \(L\) n is less than \(l_0\),

[0064]

[0065] In Formulas (10) and (11), g is the acceleration due to gravity.

[0066] In the fifth step: the hogging moment M of the nth measurement profile Bn :

[0067]

[0068] In Formula (12), g is the acceleration due to gravity.

[0069] In the fifth step: the calculation method of the torque T:

[0070] T = 2mgl3 (13)

[0071] In Formula (13), g is the acceleration due to gravity.

[0072] The beneficial effects of the present invention are as follows:

[0073] The structure of the present invention is compact, reasonable, and easy to operate. By calibrating the ship model in water, the calibration coefficient can better reflect the actual physical state, improving the accuracy of the wave load test.

[0074] At the same time, the present invention also has the following advantages:

[0075] (1) By calculating the weight placement positions that make the draft changes of each cross-section of the ship model the same, and gradually loading and unloading weights at the corresponding positions to calibrate the sagging moment coefficient, hogging moment coefficient, and torsion coefficient of the ship model in the actual state. This method takes into account the influence of the deformation of the ship model after launching on the calibration coefficient, ensuring the accuracy of the calibration in water and further improving the accuracy of the wave load test.

[0076] (2) Ensure that l1 and l2 satisfy l1 < L1, l2 > L N When calibrating the hogging moment coefficient and the torsional moment coefficient, measurement data of all measurement profiles can be obtained without changing the weight positions. Description of the Drawings

[0077] Figure 1 It is the mid-longitudinal sectional view of the ship model of the present invention.

[0078] Figure 2 It is the waterplane view of the ship model of the present invention.

[0079] Figure 3 It is the local coordinate system diagram of the waterplane of the ship model of the present invention.

[0080] Figure 4 It is the schematic diagram of the sagging coefficient calibration of the present invention.

[0081] Figure 5 Schematic diagram for calibrating the mid-arch coefficient of the present invention

[0082] Figure 6 Schematic diagram for calibrating the torsional coefficient of the present invention

[0083] Figure 7 Schematic diagram of the strain gauge pasting for the nth measurement section of the present invention (side view)

[0084] Figure 8 Schematic diagram of the strain gauge pasting for the nth measurement section of the present invention (front view)

[0085] Figure 9 Schematic diagram of the strain gauge pasting for the nth measurement section of the present invention (rear view)

[0086] Figure 10 Schematic diagram of the connection method of the strain gauges for the nth measurement section of the present invention (measuring vertical bending strain)

[0087] Figure 11 Schematic diagram of the connection method of the strain gauges for the nth measurement section of the present invention (measuring torsional deformation strain)

[0088] Wherein: a, hull; b, measuring beam; c, support cross beam; d, connection base Specific implementation mode

[0089] The following combines with the attached drawings to illustrate the specific implementation mode of the present invention

[0090] As Figures 1-6 shown, the method for calibrating the ship model in water in the first embodiment includes a hull a, a measuring beam b is installed in the middle of the hull a, the measuring beam b is connected to the inner wall of the hull a, and the hull a is sectionalized; the ship model is mainly composed of the hull a and the measuring beam b, the central axis of the measuring beam b coincides with the mid-longitudinal section of the hull a, a plurality of support cross beams c are arranged in parallel at intervals inside the hull a, both ends of the support cross beam c are connected to the inside of the hull a, and at the same time the support cross beam c is perpendicular to the measuring beam b, and a connection base d is installed on the support cross beam c, and the measuring beam b is installed above the connection base d

[0091] The process of calibrating the ship model in water includes the following steps

[0092] The first step, determining the weight placement position

[0093] Define a local coordinate system on the waterline plane of the hull a, and the origin of the local coordinate system is O(0, 0)

[0094] The origin O of the local coordinate system is the intersection point of the hull cross section where the stern seal plate of the hull is located, the mid-longitudinal section of the hull and the waterline plane, the positive direction of the X axis is towards the bow of the ship, and the positive direction of the Y axis points to the port side

[0095] Determine the positions for placing weights to make the draft changes of each cross-section of the ship model the same:

[0096] When calibrating the sagging bending moment coefficient: The weight placement position is at the centroid A0 of the ship's waterplane. A0 is located in the local coordinate system and the coordinates of A0 in the local coordinate system are (l0, 0);

[0097] When calibrating the hogging bending moment coefficient: The weight placement positions are at B1 and B2 in the local coordinate system respectively. The coordinates of B1 in the local coordinate system are (l1, 0), and the coordinates of B2 in the local coordinate system are (l2, 0), where l1 < l2;

[0098] When calibrating the torsion coefficient: The weight placement positions are at C1 and C2 in the local coordinate system respectively. And C1 and C2 are located in the first quadrant and the fourth quadrant of the local coordinate system respectively. The abscissa of C1 is l1, the abscissa of C2 is l2, the ordinates of C1 and C2 are equal in magnitude, opposite in sign, and the absolute value is l3;

[0099] l0 is: When calibrating the sagging bending moment coefficient, the X-direction coordinate of the weight in the local coordinate system;

[0100] l1 is: When calibrating the hogging bending moment coefficient, the X-direction coordinate of the aft weight in the local coordinate system;

[0101] l2 is: When calibrating the hogging bending moment coefficient, the X-direction coordinate of the bow weight in the local coordinate system;

[0102] l3 is: When calibrating the torsion coefficient, the absolute value of the Y-direction coordinate of the aft and bow weights in the local coordinate system;

[0103] The area of the ship's waterplane is A,

[0104]

[0105] In formula (1), x is the position variable in the X direction in the local coordinate system; f(x) represents the half waterline width at the X-direction coordinate x in the local coordinate system, and L is the total length of the ship's waterplane;

[0106] Δh is the increase in the draft of the ship a after placing a weight with a mass of m once when calibrating the sagging bending moment coefficient,

[0107]

[0108] ΔH is the increase in the draft of the ship a after placing a weight with a mass of 2m once when calibrating the hogging bending moment coefficient,

[0109]

[0110] In formulas (2) and (3), ρ is the density of water;

[0111] Step 2. Determine the position of the measurement section and the connection method of the strain gauges:

[0112] The measurement section is located at the hull section. The number of measurement sections is N, and the label of the currently measured measurement section is n, where n is a natural number less than or equal to N; as shown in the attached Figure 1 The sectional positions of the hull a, which are the positions of the measurement sections, are represented by SE1, SE2,..., SEN;

[0113] L n is the X-direction coordinate of the nth measurement section in the local coordinate system;

[0114] Connect the strain gauges pre-pasted on the measurement beam b according to a certain bridge connection method;

[0115] Step 3. Place the hull a statically in the water tank and connect the strain gauges to the dynamic strain gauge with measurement wires;

[0116] Step 4. Obtain the mean value of the change in each strain signal:

[0117] When calibrating the sagging bending moment coefficient: Gradually load weights of mass m at the local coordinate system A0, and then gradually unload the weights of mass m to obtain the mean value of the change in the vertical bending strain signal of the nth measurement section

[0118] When calibrating the hogging bending moment coefficient: Gradually load weights of mass m simultaneously at the local coordinates B1 and B2, and then gradually unload the weights of mass m simultaneously to obtain the mean value of the change in the vertical bending strain signal of the nth measurement section

[0119] When calibrating the torsion coefficient: Gradually load weights of mass m simultaneously at the local coordinates C1 and C2, and then gradually unload the weights of mass m simultaneously to obtain the mean value of the change in the torsional deformation strain signal of the nth measurement section

[0120] Step 5. Calculate the coefficient to be calibrated for the nth measurement section:

[0121] The sagging bending moment coefficient δ An :

[0122]

[0123] M An is the sagging bending moment of the nth measurement section;

[0124] The hogging bending moment coefficient δ Bn :

[0125]

[0126] M Bn is the hogging bending moment of the nth measurement section;

[0127] The torsional coefficient δ of the nth measurement section Cn :

[0128]

[0129] T is the torque borne by hull a when weights of mass m are loaded on both the port and starboard sides once, and the torques borne by each measurement section of hull a are the same.

[0130] According to the calibration method in this embodiment, weights are applied to the hull model in still water, and the vertical bending strain and torsional deformation strain at the measurement section of measurement beam b are measured respectively to obtain the relationship between the load and strain at the measurement section, that is, the strain coefficient.

[0131] As Figures 1-11 shown, the calibration method of the ship model in water in the second embodiment includes hull a, with a measurement beam b installed in the middle of hull a. The measurement beam b is connected to the inner wall of hull a, and hull a is of sectional type; the ship model is mainly composed of hull a and measurement beam b. The central axis of the measurement beam b coincides with the longitudinal midsection of hull a. Multiple support crossbeams c are arranged in parallel at intervals inside hull a. Both ends of the support crossbeam c are connected to the inside of hull a, and at the same time, the support crossbeam c is perpendicular to the measurement beam b. A connection base d is installed on the support crossbeam c, and the measurement beam b is installed above the connection base d.

[0132] The calibration process of the ship model in water includes the following steps:

[0133] The first step is to determine the weight placement position:

[0134] Define a local coordinate system on the waterline plane of hull a, and the origin of the local coordinate system is O(0, 0);

[0135] The origin O of the local coordinate system is the intersection point of the hull cross-section where the stern seal plate of the hull is located, the longitudinal midsection of the hull, and the waterline plane. The positive direction of the X-axis is towards the bow, and the positive direction of the Y-axis points to the port side;

[0136] The area of the hull waterline plane is A,

[0137]

[0138] In formula (1), x is the position variable in the X direction in the local coordinate system; f(x) represents the half waterline width with the X-direction coordinate of x in the local coordinate system, and L is the total length of the hull on the waterline plane;

[0139] Δh is the increase in the draft of hull a after a weight of mass m is placed once during the calibration of the hogging bending moment coefficient,

[0140]

[0141] ΔH is the increase in the draft of hull a after placing a weight of 2m once during the calibration of the midship bending moment coefficient,

[0142]

[0143] In formulas (2) and (3), ρ is the density of water;

[0144] Determine the weight placement positions that make the draft changes of each cross-section of the ship model the same:

[0145] During the calibration of the hogging bending moment coefficient: The weight placement position is at the centroid A0 of the waterplane of the hull. A0 is located in the local coordinate system and the coordinates of A0 in the local coordinate system are (l0, 0);

[0146] During the calibration of the sagging bending moment coefficient: The weight placement positions are at B1 and B2 in the local coordinate system respectively. The coordinates of B1 in the local coordinate system are (l1, 0), and the coordinates of B2 in the local coordinate system are (l2, 0), where l1 < l2;

[0147] During the calibration of the torsion coefficient: The weight placement positions are at C1 and C2 in the local coordinate system respectively. And C1 and C2 are located in the first quadrant and the fourth quadrant of the local coordinate system respectively. The abscissa of C1 is l1, the abscissa of C2 is l2, and the ordinates of C1 and C2 are equal in magnitude, opposite in sign, and the absolute value is l3;

[0148] l0 is: During the calibration of the sagging bending moment coefficient, the X-direction coordinate of the weight in the local coordinate system; Calculate and determine the X-direction coordinate l0 of the centroid A0 of the waterplane of the hull where the weight is placed.

[0149]

[0150] Obtain l0 by calculating through formula (7), determine the weight placement position during the calibration of the sagging bending moment coefficient, place the weight at the centroid position, the draft of the ship model increases, and without considering the deformation of the hull, the increase in the draft of each section of hull a is the same;

[0151] l1 is: During the calibration of the hogging bending moment coefficient, the X-direction coordinate of the aft weight in the local coordinate system;

[0152] l2 is: During the calibration of the hogging bending moment coefficient, the X-direction coordinate of the forward weight in the local coordinate system,

[0153] l1 and l2 satisfy the following relationship, so that placing weights of the same mass at the mid-longitudinal section of l1 and l2 makes the draft changes of each section of the hull the same without considering the deformation of the hull:

[0154]

[0155] Then:

[0156] In Formulas (8) and (9), l1 and l2 also need to satisfy l1 < L1 and l2 > L N ,

[0157] L1 is the X-direction coordinate of the first measurement section in the local coordinate system,

[0158] L N is the X-direction coordinate of the Nth measurement section in the local coordinate system,

[0159] Determine the position of l1, and obtain the value of l2 according to Formula (9), that is, determine the positions where weights are placed at the midship section at distances l1 and l2 from the stern when calibrating the midship bending moment coefficient; according to the actual ship model sectioning situation, when determining l1, the position of the stern weight loading should be about 30 cm to 50 cm from the first measurement section to ensure the accuracy of the measurement data; ensure that l1 and l2 satisfy l1 < L1 and l2 > L N When calibrating the midship bending moment coefficient and the torsional moment coefficient, all measurement data of the measurement sections can be obtained without changing the position of the weights;

[0160] l3 is: when calibrating the torsional coefficient, the absolute value of the Y-direction coordinate of the stern and bow weights in the local coordinate system,

[0161] l3 < f(l1) and l3 < f(l2),

[0162] f(l1) is the half waterline width representing the X-direction coordinate of l1 in the local coordinate system,

[0163] f(l2) is the half waterline width representing the X-direction coordinate of l2 in the local coordinate system,

[0164] Ensure that when calibrating the torsional coefficient, the weights can be placed within the ship width. Determine l1 and l2. After determining l1 and l2, the positions of the weights placed at the bow and stern are moved l3 to the port side and starboard side respectively, which are the positions where the weights are placed when calibrating the torsional coefficient.

[0165] Step 2: Determine the positions of the measurement sections and the connection method of the strain gauges:

[0166] The measurement sections are located at the ship hull sections. The number of measurement sections is N. The label of the currently measured measurement section is n, and n is a natural number less than or equal to N; as shown in the attached Figure 1 The sectional positions of the hull a, which are the positions of the measurement sections, are represented by SE1, SE2,..., SEN;

[0167] L n is the X-direction coordinate of the nth measurement section in the local coordinate system;

[0168] Connect the strain gauges pre-pasted on the measuring beam b according to a certain bridge connection method;

[0169] As Figures 7-11 shown, for the nth measurement section, paste a unidirectional longitudinal strain gauge ε n1 and ε n2 on the upper and lower surfaces of the measuring beam b respectively, and connect them in a half-bridge manner. The connection method is as Figure 10 shown. The strain gauges ε n1 and ε n2 are used to measure the vertical bending strain that occurs when the ship sails in waves. Similarly, for the nth measurement section, paste a bidirectional strain gauge on each side of the left and right of the measuring beam b. The strain gauge on the left is ε n3 and ε n4 , and the strain gauge on the right is ε n5 and ε n6 . As Figure 8 , Figure 9 shown, the two axes of the bidirectional strain gauge are respectively at 45° and -45° to the longitudinal direction of the measuring beam. The connection method of the bidirectional strain gauge is as Figure 11 shown, and it is used to measure the torsional deformation strain that occurs when the ship sails in waves.

[0170] Step 3: Place the hull a statically in the water tank, and connect the strain gauge and the dynamic strain gauge with a measuring wire;

[0171] Step 4: Obtain the mean value of the change amount of each strain signal:

[0172] When calibrating the sagging bending moment coefficient: Gradually load weights of mass m at the local coordinate A0, and then gradually unload weights of mass m to obtain the mean value

[0173] of the change amount of the vertical bending strain signal of the nth measurement section. When calibrating the hogging bending moment coefficient: Gradually load weights of mass m at the local coordinates B1 and B2 simultaneously, and then gradually unload weights of mass m simultaneously to obtain the mean value

[0174] of the change amount of the vertical bending strain signal of the nth measurement section. When calibrating the torsion coefficient: Gradually load weights of mass m at the local coordinates C1 and C2 simultaneously, and then gradually unload weights of mass m simultaneously to obtain the mean value

[0175] of the change amount of the torsional deformation strain signal of the nth measurement section. Step 5: Calculate the coefficient to be calibrated for the nth measurement section:

[0176] The sagging bending moment coefficient δ An of the nth measurement section:

[0177]

[0178] M An is the mid - vertical bending moment of the nth measurement section,

[0179] When L n is greater than l0,

[0180]

[0181] When L n is less than l0,

[0182]

[0183] In Formulas (10) and (11), g is the acceleration due to gravity;

[0184] The mid - arch bending moment coefficient δ of the nth measurement section Bn :

[0185]

[0186] M Bn is the mid - arch bending moment of the nth measurement section,

[0187]

[0188] In Formula (12), g is the acceleration due to gravity;

[0189] The torsion coefficient δ of the nth measurement section Ch :

[0190]

[0191] T is the torque borne by the hull (a) when weights of mass m are loaded on both the port and starboard sides once. The torques borne by each measurement section of the hull (a) are the same.

[0192] The calculation method of the torque T:

[0193] T = 2mgl3 (13)

[0194] In Formula (13), g is the acceleration due to gravity.

[0195] Apply weights to the hull model in still water according to the calibration method in this embodiment, and measure the vertical bending strain and torsional deformation strain at the measurement beam b measurement section respectively to obtain the relationship between the load and strain at the measurement section, that is, the strain coefficient.

[0196] As Figures 1-6 shown, the calibration method of the ship model in water in Embodiment 3:

[0197] (1) Mid - vertical coefficient calibration steps:

[0198] The calibration of the sagging coefficient is as Figure 4 shown. In the figure, SE1, SE2, …, SE9 respectively represent 9 measurement profiles from the stern to the bow of the ship model. The specific calibration steps are as follows:

[0199] (i) Adjust the state of the ship model, and then place the adjusted ship model in the water tank;

[0200] (ii) Calculate the position of the centroid A0 of the still water plane of the ship model according to formula (7). In the Figure 4 reference coordinate system, the centroid A0 is located at the mid-longitudinal section of the hull, and the distance from the stern seal plate of the hull is l0;

[0201] (iii) Load weights at the centroid A0. At this time, the ship model is in a sagging state. Use the method of gradually loading and then gradually unloading weights of the same mass to calibrate the sagging bending moment coefficient of the ship model. Select formula (10) and formula (11) to calculate the sagging bending moment received by each measurement profile according to the position of the measurement profile;

[0202] (iv) During the process of loading weights, use a dynamic strain gauge to measure the vertical bending strain signals of each measurement profile, and then obtain the mean value of the change in the vertical bending strain signals of each measurement profile;

[0203] (V) Calculate the sagging bending moment coefficient according to formula (4).

[0204] (2) Calibration steps for hogging coefficient:

[0205] The calibration of the hogging coefficient is as Figure 5 shown. In the figure, SE1, SE2, …, SE9 respectively represent 9 measurement profiles from the stern to the bow of the ship model. The specific calibration steps are as follows:

[0206] (i) Determine the tail weight loading position B1. In the Figure 4 reference coordinate system, B1 is located at the mid-longitudinal section of the hull, and the distance from the stern seal plate of the hull is l1. According to the actual ship model segmentation situation, l1 needs to be determined so that the tail weight loading position is about 30 cm to 50 cm away from the first measurement profile;

[0207] (ii) Calculate l2 according to formula (9), and determine the bow weight loading position B2. B2 is located at the mid-longitudinal section of the hull, and the distance from the stern seal plate of the hull is l2;

[0208] (iii) Place weights of the same mass at l1 and l2 positions respectively. At this time, the ship model is in a hogging state. Use the method of gradually loading and then gradually unloading weights of the same mass to calibrate the hogging bending moment coefficient of the ship model, and calculate the hogging bending moment received by each profile according to formula (12);

[0209] (iv) During the process of loading weights, use a dynamic strain gauge to measure the vertical bending strain signals of each section, and then obtain the mean value of the change in the vertical bending strain signals of each measurement section.

[0210] (v) Calculate the hogging moment coefficient according to formula (5).

[0211] (III) Torque coefficient calibration steps:

[0212] The torsion coefficient calibration is as Figure 6 shown. SE1, SE2, …, SE9 in the figure respectively represent 9 measurement sections from the stern to the bow of the ship. The specific calibration steps are as follows:

[0213] (i) Move the weights at the bow and stern of the ship in the hogging condition to the port and starboard by the same distance l3 respectively to obtain the positions C1 and C2 of the weights during torsion calibration.

[0214] (ii) Use the method of gradually loading and then gradually unloading weights of the same mass to conduct torsion calibration on the ship model. Calculate the torque received by the hull according to formula (13).

[0215] (iii) During the process of loading weights, use a dynamic strain gauge to measure the torsional deformation strain signals of each section.

[0216] (iv) Calculate the torsion coefficient according to formula (6).

[0217] Due to the action of buoyancy and its own weight, after the ship model is launched into the water, it will be in the sagging or hogging condition. And due to the experimental errors, it is difficult to ensure that the mass distribution of the hull model is in an absolutely balanced state between the port and starboard sides, and the ship body will have slight vertical bending and torsional deformation, and the initial state of the strain gauges will change slightly, resulting in a slight change in the calibration coefficient. When calibrating the ship model, the working environment of the ship model is in water. The calibration coefficient in water can better reflect the actual physical problems. This calibration method determines the positions of the weights loaded on the hull model based on scientific calculations, realizes calibration in water while ensuring the accuracy of calibration, and further improves the accuracy of the wave load test. In order to improve the accuracy of the wave load test, when the test conditions permit, this calibration method provides a practical method for calibrating the segmented hull model in water.

[0218] The above description is an explanation of the present invention, not a limitation of the invention. The scope defined by the present invention can be seen in the claims. Within the protection scope of the present invention, any form of modification can be made.

Claims

1. A method for calibrating a ship model in water, characterized in that: It includes a hull (a), a measuring beam (b) is installed in the middle of the hull (a), the measuring beam (b) is connected to the inner wall of the hull (a) through a support cross beam (c), and the hull (a) is of a segmented type; The calibration process includes the following steps: The first step: Determine the weight placement positions: Define a local coordinate system on the waterline plane of the hull (a), and the origin of the local coordinate system is O(0, 0); the origin O of the local coordinate system is the intersection point of the hull cross-section where the stern seal plate of the hull is located, the mid-longitudinal section of the hull, and the waterline plane. The positive direction of the X-axis is towards the bow of the ship, and the positive direction of the Y-axis points to the port side; Determine the weight placement positions that make the draft changes of each cross-section of the ship model the same: When calibrating the sagging bending moment coefficient: The weight placement position is at the centroid A0 of the waterline plane of the hull, A0 is located in the local coordinate system and the coordinates of A0 in the local coordinate system are (l0, 0); When calibrating the hogging bending moment coefficient: The weight placement positions are at B1 and B2 in the local coordinate system respectively. The coordinates of B1 in the local coordinate system are (l1, 0), and the coordinates of B2 in the local coordinate system are (l2, 0), where l1 < l2; When calibrating the torsion coefficient: The weight placement positions are at C1 and C2 in the local coordinate system respectively, and C1 and C2 are located in the first quadrant and the fourth quadrant of the local coordinate system respectively. The abscissa of C1 is l1, the abscissa of C2 is l2, the ordinates of C1 and C2 are equal in magnitude, opposite in sign, and the absolute value is l3; l0 is: When calibrating the sagging bending moment coefficient, the X-direction coordinate of the weight in the local coordinate system; l1 is: When calibrating the hogging bending moment coefficient, the X-direction coordinate of the aft weight in the local coordinate system; l2 is: When calibrating the hogging bending moment coefficient, the X-direction coordinate of the forward weight in the local coordinate system; l3 is: When calibrating the torsion coefficient, the absolute value of the Y-direction coordinates of the aft and forward weights in the local coordinate system; The area of the waterline plane of the hull is A, In formula (1), x is the position variable in the X direction in the local coordinate system; f(x) represents the half waterline width with the X-direction coordinate of x in the local coordinate system, and L is the total length of the hull on the waterline plane; Δh is the increase in the draft of the hull (a) after placing a weight of mass m once when calibrating the sagging bending moment coefficient, ΔH is the increase in the draft of the hull (a) after placing a weight of mass 2m once when calibrating the hogging bending moment coefficient, In formulas (2) and (3), ρ is the density of water; The second step: Determine the positions of the measurement sections and the connection method of the strain gauges: The measurement sections are located at the hull segmentation positions, the number of measurement sections is N, and the label of the currently measured measurement section is n, where n is a natural number less than or equal to N; L n is the X - direction coordinate of the nth measurement profile in the local coordinate system; Connect the strain gauges pre-pasted on the measuring beam (b) according to a certain bridge circuit connection method; The third step: Place the hull (a) statically in the water tank, and connect the strain gauges and the dynamic strain gauge with measuring wires; The fourth step: Obtain the mean value of the change in each strain signal: When calibrating the midship bending moment coefficient: successively load weights of mass m at the local coordinate system A0, and then successively unload weights of mass m to obtain the mean value of the change in the vertical bending strain signal at the nth measurement section When calibrating the mid-arch bending moment coefficient: successively load weights of mass m at local coordinates B1 and B2 simultaneously, and then successively unload weights of mass m simultaneously to obtain the mean value of the change in the vertical bending strain signal at the nth measurement section When calibrating the torsional coefficient: successively load weights of mass m at local coordinates C1 and C2 simultaneously, and then successively unload weights of mass m simultaneously to obtain the mean value of the change in the torsional deformation strain signal of the nth measurement profile. The fifth step: Calculate the coefficient to be calibrated for the nth measurement section: The mid-span bending moment coefficient δ of the nth measurement section An : M An is the mid-span bending moment of the nth measurement profile; The hogging moment coefficient δ of the nth measurement profile Bn : M Bn is the hogging moment of the nth measurement section; The torsional coefficient δ of the nth measurement profile Cn : T is the torque borne by the hull (a) when weights of mass m are loaded on both the port and starboard sides once. The torques borne by each measurement section of the hull (a) are the same.

2. A method for calibrating a ship model in water according to claim 1, characterized in that: In the first step: When calibrating the midship bending moment coefficient, the position where the weights are placed is obtained through calculation, and this position is the centroid A0 of the ship's waterplane. The X-direction coordinate of the centroid A0 of the ship's waterplane in the local coordinate system is l0. l0 is obtained through calculation using formula (7) to determine the position where the weights are placed when calibrating the midship bending moment coefficient.

3. A ship model underwater calibration method as claimed in claim 1, wherein: In the first step: l1 and l2 satisfy the following relationship: Then: In Formulas (8) and (9), l1 and l2 also need to satisfy l1 < L1 and l2 > L N , L1 is the X-direction coordinate of the first measurement section in the local coordinate system. L N is the X - coordinate of the Nth measurement profile in the local coordinate system.

4. A ship model underwater calibration method as claimed in claim 1, wherein: In the first step: l3 < f(l1) and l3 < f(l2), f(l1) is the half waterline width representing the X-direction coordinate of l1 in the local coordinate system. f(l2) is the half waterline width representing the X-direction coordinate of l2 in the local coordinate system. Ensure that when calibrating the torsion coefficient, the weights can be placed within the ship's width range.

5. A ship model underwater calibration method as claimed in claim 1, wherein: In the fifth step: the mid-span bending moment M of the nth measurement section An : When L n is greater than l0, When L n is less than l0, In formulas (10) and (11), g is the acceleration due to gravity.

6. A ship model underwater calibration method as claimed in claim 1, wherein: In the fifth step: the hogging moment M of the nth measurement section Bn : In formula (12), g is the acceleration due to gravity.

7. A ship model underwater calibration method as claimed in claim 1, wherein: In the fifth step: The calculation method of the torque T: T = 2mgl3 (13) In formula (13), g is the acceleration due to gravity.

Images