Device and method for determining vertical water entry starting time of model in waves

Abstract

According to the device and method for determining the vertical water entry starting time of the model in the waves, a falling body model is arranged on the upper end face of an experimental pool through a support, and an acceleration sensor, a pressure sensor and a resistance strain gauge sensor are arranged on the inner bottom face of the falling body model; a wave maker is arranged at the end, away from the falling body model, of the pool, three wave height meters used for measuring the height of waves are arranged on the pool, and the acceleration sensor, the pressure sensor, the resistance strain gauge sensor and the three wave height meters are connected with the signal input end of a dynamic signal acquisition instrument. The signal output end of the dynamic signal acquisition instrument is connected with the signal input end of the terminal computer, and the control signal output end of the terminal computer is connected with the signal input end of the wave maker and the support. According to the invention, the three wave height meters / dynamic signal acquisition instruments and the dynamic signal acquisition instrument are used for acquiring real-time parameters of waves, so that the falling body model can be controlled to generate falling body slamming under a set wave phase condition.

Description

Technical Field

[0001] This invention relates to a test of a model undergoing vertical water impaction in waves. In particular, it relates to an apparatus and method for determining the start-up time of a model undergoing vertical water impaction in waves.

[0002] A control system for controlling large-scale models to undergo vertical water impact tests in waves belongs to the field of shipbuilding and ocean engineering. Background Technology

[0003] Currently, slamming is a common phenomenon in the shipbuilding industry. When a ship is sailing in rough seas, due to the violent movement of the hull and waves, slamming can occur when the hull structure is submerged and then re-submerged. Slamming poses a potential risk to the local structure of the bow and the overall structural strength of the ship. Slamming can threaten the safety of the ship, and severe slamming can lead to damage to the local structure.

[0004] Water impact is a transient problem. The moment a falling model enters the water, it generates a short-term, large instantaneous pressure, which is difficult to study theoretically. Experimental research is an important way to solve the fluid-structure interaction problem of water impact on ship hull structures. By studying the fluid-structure interaction effect of local structural impact through falling impact tests, reasonable experimental data can be obtained, which has important practical engineering significance for the design and performance optimization of ships.

[0005] Currently, there are many slamming tests conducted on structural models in still water, but very few slamming tests conducted in waves, which presents significant challenges.

[0006] (1) Current experimental systems have difficulty controlling the falling body model to slam under arbitrary given wave phase conditions;

[0007] (2) The free fall and slamming experiment in the waves cannot guarantee that the falling model will fall vertically in the waves. The falling model will tilt during the fall. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a device and method for determining the vertical entry time of the model into the water in the waves in order to ensure that the falling model falls vertically and to control the falling model under a predetermined wave phase condition in the falling impact experiment.

[0009] The technical solution adopted in this invention is: a device for determining the start-up time of a model vertically entering the water in waves, comprising an experimental water tank, a falling model mounted on the upper surface of the water tank via a support, an acceleration sensor, a pressure sensor, and a resistance strain gauge sensor respectively mounted on the inner bottom surface of the falling model, a wave generator mounted at the end of the water tank away from the falling model, and three wave height gauges for measuring wave height mounted on the water tank, the three wave height gauges being arranged sequentially at the upper end of the water tank from near to far from the wave generator, the acceleration sensor, pressure sensor, resistance strain gauge sensor, and the three wave height gauges being respectively connected to the signal input terminal of a dynamic signal acquisition instrument, the signal output terminal of the dynamic signal acquisition instrument being connected to the signal input terminal of a terminal computer, and the control signal output terminal of the terminal computer being respectively connected to the signal input terminal of the wave generator and the support.

[0010] A method for determining the initiation time of a model vertically entering water in waves involves controlling the model to slam under predetermined wave phase conditions. Given the model's fall height, the system's inherent delay time, and wave parameters, the wave number is calculated using dispersion relations and Newton's iteration method. After detecting the predetermined phase, the time from point A (where the first wave height meter is located) to point C (where the third wave height meter is located) of the same wave is calculated. The fall time of the model and the system's inherent delay time are then taken into account to determine the release command time. This allows the model to be released at a predetermined time and slam under predetermined wave phase conditions, thus achieving the requirement of controlling the model to slam under any phase condition.

[0011] This invention relates to a device and method for determining the vertical entry time of a model into waves. It utilizes three wave height meters / dynamic signal acquisition devices to acquire real-time wave parameters. A structural release control system controls the falling model to initiate a slamming motion. This allows for the prediction of the falling model's release time and control of the falling model to slam under predetermined wave phase conditions. The system is simple to operate, integrating multiple systems into one, making the lifting, securing, and releasing of heavy falling models easier and more convenient. It is suitable for studying the structural response of the internal structure of falling models and ensures the vertical descent of the model. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the overall structure of the device for determining the start-up time of a model vertically entering the water in waves according to the present invention.

[0013] Figure 2 yes Figure 1 A schematic diagram of the structure combining the slide rail on the central support with the pulley assembly on the free-fall model;

[0014] Figure 3This is a flowchart of the method of the present invention.

[0015] In the picture,

[0016] 1: Water tank 2: Support frame

[0017] 2.1: Slide Rail 3: Falling Model

[0018] 3.1: Control hook 4: Wave generator

[0019] 5: Dynamic signal acquisition device 6: Dynamic signal acquisition device

[0020] 7: First wave height gauge 8: Second wave height gauge

[0021] 9: Third wave height gauge 10: Control hook Detailed Implementation

[0022] The apparatus and method for determining the vertical entry time of a model into waves according to the present invention will be described in detail below with reference to embodiments and accompanying drawings.

[0023] like Figure 1 As shown, the device for determining the start-up time of a model vertically entering the water in waves according to the present invention includes an experimental water tank 1. A falling model 3 is mounted on the upper surface of the water tank 1 via a support 2. An acceleration sensor, a pressure sensor, and a resistance strain gauge sensor are respectively mounted on the inner bottom surface of the falling model 3. A wave generator 4 is mounted at the end of the water tank 1 away from the falling model 3. Three wave height meters for measuring wave height are mounted on the water tank 1. The three wave height meters are arranged sequentially at the upper end of the water tank 1 in order of distance from the wave generator 4. The acceleration sensor, pressure sensor, resistance strain gauge sensor, and the three wave height meters are respectively connected to the signal input terminal of a dynamic signal acquisition instrument 5. The signal output terminal of the dynamic signal acquisition instrument 5 is connected to the signal input terminal of a terminal computer 6. The control signal output terminal of the terminal computer 6 is respectively connected to the signal input terminal of the wave generator 4 and the support 2 for controlling the wave generation of the wave generator 4 and controlling the unhooking and entry of the falling model 3 into the water.

[0024] The three wave height meters are arranged in order of distance from the wave generator 4, namely, the first wave height meter 7, the second wave height meter 8, and the third wave height meter 9. The first wave height meter 7 and the second wave height meter 8 are located between the falling model 3 and the wave generator 4, and the distance between the first wave height meter 7 and the second wave height meter 8 is less than one wavelength. The third wave height meter 9 is located at the point where the falling model 3 is impacted.

[0025] The support 2 is equipped with a control hook 10 that hooks onto the top of the freefall model 3. The control end of the control hook 10 is connected to the control signal output of the terminal computer 6, and under the control of the control signal, the freefall model 3 is detached and enters the water. That is, the control hook 10 maintains the freefall model at a predetermined height before receiving a release command from the terminal computer 6, and releases it at a predetermined time after receiving the command.

[0026] like Figure 2 As shown, corresponding slide rails 2.1 are vertically arranged on two corresponding inner sides of the support 2. On the two sides of the falling model 3 opposite to the slide rails 2.1, a set of pulley assemblies 3.1 that can slide up and down along the slide rails 2.1 are respectively arranged. When the terminal computer 6 controls the control hook to disengage, the falling model 3 can fall vertically into the water along the slide rails 2.1, ensuring that the falling model falls vertically and makes a bang, ensuring that it does not overturn during the fall, and at the same time, the pulley assembly 3.1 avoids excessive sliding friction.

[0027] The method for determining the device for determining the start time of a model vertically entering the water in waves according to the present invention involves controlling the model to slam under predetermined wave phase conditions. Given the falling height of the falling model, the inherent delay time of the system, and the wave parameters, the wave number is solved using dispersion relations and Newton's iteration method. After detecting the predetermined phase, the time from point A (where the first wave height meter 7 is located) to point C (where the third wave height meter 9 is located) of the predetermined phase of the same wave is calculated. Then, the falling time of the falling model and the inherent delay time of the system are taken into account, and finally, the time when the release command is issued is obtained. This controls the falling model to be released at a predetermined time and to slam under predetermined wave phase conditions, thereby achieving the requirement of controlling the falling model to slam under arbitrary phase conditions.

[0028] The method for determining the device for determining the start-up time of a model vertically entering water in waves according to the present invention specifically includes the following steps:

[0029] Step 1: Start the wave generator 4, dynamic signal acquisition instrument 5 and terminal computer 6. Input the preset wave height, period and total number of waves into the wave generator 4, and the wave generator 4 will generate waves.

[0030] Step 2: Collect wave data from the first wave height meter 7, the second wave height meter 8, and the third wave height meter 9 using the dynamic signal acquisition instrument 5, and obtain the propagation time of the same phase of the same wave from point A (located at the first wave height meter 7) to point B (located at the second wave height meter 8). The coordinates of point A (where the first wave height instrument 7 is located), point B (where the second wave height instrument 8 is located), and point C (where the third wave height instrument 9 is located) are set as follows: , , The distances between each point are as follows: and , The first wave height meter 7 and the second wave height meter 8 are used to acquire real-time wave data at points A and B. When a wave's set phase propagates to point A, where the first wave height meter 7 is located, the dynamic signal acquisition instrument acquires the data at that moment. When the same phase of the wave propagates to point B, where the second wave height meter 8 is located, the dynamic signal acquisition instrument acquires the data at that moment. The data is then sent to terminal computer 6, where the two timestamps are subtracted to obtain the propagation time. ;

[0031] The actual wave height is obtained by calculating the height difference between the crest and trough phases of the same wave. The actual period of a wave is obtained by calculating the time difference between the same phase of adjacent waves passing through the same wave height meter. The actual wave height and actual period are compared with the preset wave height and preset period. If the deviation is within the set range, proceed to the next step. Otherwise, if the deviation is greater than the set range, adjust the wave generator and wave height meter, and return to step 1 to generate waves again.

[0032] Step 3: Based on the obtained propagation time The dispersion relation and Newton's iteration method from wave theory are used to subsequently solve for the wave number. ;

[0033] Since the wave generation sequence is A → B → C, the phase at point B, where the second wave height gauge 8 is located, lags behind the phase at point A, where the first wave height gauge 7 is located.

[0034] First, assume a simple harmonic wave at a water depth of... The propagation along the positive x-axis in the pool, its phase It is represented as:

[0035] (1);

[0036] The phases of the three wave height gauges at locations A, B, and C are respectively

[0037] (2);

[0038] (3);

[0039] (4);

[0040] in, For time, Initial phase; wave angular frequency With period The relationship is:

[0041] (5);

[0042] Then the wave angular frequency The actual cycle obtained through real-time monitoring This is obtained and used for subsequent wavenumber analysis. Solve for it.

[0043] For wavenumber This is determined by solving the dispersion equation of linear wave theory, which will... and and water depth Connecting them:

[0044] (6);

[0045] in It is the acceleration due to gravity;

[0046] When point B and point A are in phase, the following relationship holds:

[0047] (7);

[0048] Substituting the phases of points A and B into equation (7), that is, substituting equations (2) and (3) into equation (8), we get:

[0049] (8);

[0050] Then wave number for:

[0051] (9);

[0052] The wavenumber is then calculated using Newton's iteration method. Verification of the calculation:

[0053] First, the constructor Its root That is, the solution to the dispersion equation.

[0054] (10);

[0055] The iterative algorithm of Newton's method is as follows:

[0056] (11);

[0057] in, It is the first The value of the next iteration. yes exist The first derivative at that point;

[0058] The derivation is as follows:

[0059] (12);

[0060] (13);

[0061] (14);

[0062] (15);

[0063] To initiate the iteration, a reasonable initial guess is required. The deep-water approximation is usually used, that is, assuming To estimate:

[0064] (16);

[0065] (17);

[0066] Substituting equations (10) and (15) into Newton's iteration algorithm equation (11), we get:

[0067] (18);

[0068] Iterate until... Convergence (e.g.) ,in (where it is a local minimum), at which point it can be proven that the wavenumber The correctness;

[0069] Step 4: Calculate the propagation time required for the same wave of the same phase to travel from point A (located at wave height gauge 7) to point C (located at wave height gauge 9). ;

[0070] When points A and C are in phase, the following relationship exists:

[0071] (19);

[0072] Substituting the phases of points A and C into equation (19), we get:

[0073] (20);

[0074] Based on the solved wavenumber Therefore, the time lag between point C and point A is... for:

[0075] (twenty one);

[0076] Step 5: Calculate the fall time of the freefall model (3) after release.

[0077] Input the drop height of the drop model (3) in this experiment. According to Newton's kinematics formula for free fall:

[0078] (twenty two);

[0079] Since the free fall model (3) has an initial velocity of 0, substituting... and The falling time of the free-fall model (3) after release is obtained. for:

[0080] (twenty three);

[0081] in, It is the acceleration due to gravity;

[0082] Step 6: Solve for the preset time of the release command sent by the falling body model (3).

[0083] Preset time for sending release command of free fall model The calculation formula is shown below;

[0084] (twenty four)

[0085] In the formula, The preset time for sending the release command to the falling model. The propagation time required for the same wave of the same phase to travel from the first wave height gauge 7 to the third wave height gauge 9. This is the inherent delay time of the system. The model's fall time;

[0086] Therefore, all three terms on the right side of the equation (24) are known. Substituting these known terms into equation (24), we finally obtain the preset time for sending the release command of the falling model. The expression:

[0087] (25)

[0088] In the formula, For wave number, This represents the distance between the first wave height gauge 7 and the third wave height gauge 9. For wave frequency, The inherent delay time of the control system is fixed and known. The falling height of the free-falling model. For local gravitational acceleration, (Depend on Export) , and All parameters are known.

[0089] The preset time for sending the release command of the falling body model is obtained by solving the problem. Afterwards, the terminal computer continues to acquire real-time wave data using a wave height meter, detecting the target phase, wave period, and wave height. If the parameters remain stable, the system will release the wave at the preset time indicated by the falling body model release command. If the parameters are unstable and cannot meet the test requirements, a release command is not sent, and the wave generator and wave height meter are debugged, then return to step 1.

[0090] The preset time for sending the release command of the falling model is mentioned. Calculation formula This is used to control the falling model to slam into the water at a set wave phase. Specifically, when the same phase of the same wave propagates from the first wave height gauge 7 to the third wave height gauge 9, the falling model will simultaneously enter the water and slam into the water. Assume the propagation time required for the same phase of the same wave to travel from the first wave height gauge 7 to the third wave height gauge 9 is... During this period, a series of processes need to be completed, including releasing the falling model and the falling model impacting the water. The time factor that needs to be considered is the inherent delay time of the system. Falling time of the free-fall model The preset time for sending the release command of the falling model The sum of the times required for these three events is equal to the propagation time required for the same wave, in the same phase, from the first wave height gauge 7 to the third wave height gauge 9. They are equal, but due to the inherent delay time of the system... The model's fall time is a fixed value. Referring to the free fall formula, the preset time for sending the release command of the falling model is thus obtained. The calculation formula.

[0091] Step 7: After the terminal computer sends the release command, the control hook receives the command and executes the mechanical release operation. Under the action of the support structure's fixed column and the track slider, the object falls vertically and impacts the target. The impact data is collected using the acquisition device for subsequent data processing and analysis.

Claims

1. An apparatus for determining the start-up time of a model vertically entering water in waves, comprising an experimental water tank (1), characterized in that, A freefall model (3) is mounted on the upper surface of the pool (1) via a support (2). An accelerometer, a pressure sensor, and a resistance strain gauge sensor are mounted on the inner bottom surface of the freefall model (3). A wave generator (4) is mounted at the end of the pool (1) away from the freefall model (3). Three wave height meters for measuring wave height are mounted on the pool (1). The three wave height meters are mounted sequentially on the upper surface of the pool (1) in order of distance from the wave generator (4). The accelerometer, pressure sensor, resistance strain gauge sensor, and the three wave height meters are connected to the signal input terminal of a dynamic signal acquisition instrument (5). The signal output terminal of the dynamic signal acquisition instrument (5) is connected to the signal input terminal of a terminal computer (6). The control signal output terminal of the terminal computer (6) is connected to the signal input terminal of the wave generator (4) and the support (2).

2. The apparatus for determining the start-up time of a model vertically entering water in waves according to claim 1, characterized in that, The three wave height meters are the first wave height meter (7), the second wave height meter (8), and the third wave height meter (9) arranged in order from the nearest to the farthest from the wave generator (4). The first wave height meter (7) and the second wave height meter (8) are located between the falling model (3) and the wave generator (4), and the distance between the first wave height meter (7) and the second wave height meter (8) is less than one wavelength. The third wave height meter (9) is located at the point where the falling model (3) is impacted.

3. The apparatus for determining the start-up time of a model vertically entering water in waves according to claim 1, characterized in that, The support (2) is provided with a control hook (10) that hooks onto the top of the falling model (3). The control end of the control hook (10) is connected to the control signal output end of the terminal computer (6), and the falling model (3) is unhooked and enters the water under the control of the control signal.

4. The apparatus for determining the start-up time of a model vertically entering water in waves according to claim 1, characterized in that, The bracket (2) has two corresponding inner sides with vertically arranged slide rails (2.1), and the falling model (3) has a set of pulley assemblies (3.1) that can slide up and down along the slide rails (2.1) on two sides opposite to the slide rails (2.1).

5. A method for determining the starting time of a device for vertically entering water in waves, characterized in that, The control model is to cause a slam under a predetermined wave phase. Given the falling height of the falling model, the inherent delay time of the system, and the wave parameters, the wave number is solved by the dispersion relation and Newton's iteration method. After the predetermined phase is detected, the time from point A where the first wave height meter (7) is located to point C where the third wave height meter (9) is located is calculated. Then, the falling time of the falling model and the inherent delay time of the system are taken into account, and the time when the release command is issued is finally obtained. Thus, the falling model is controlled to be released at a predetermined time and cause a slam under the predetermined wave phase, thereby achieving the requirement of controlling the falling model to cause a slam under any phase condition.

6. The determination method according to claim 5, characterized in that, Specifically, the steps include the following: Step 1: Start the wave generator (4), dynamic signal acquisition instrument (5) and terminal computer (6). Input the preset wave height, period and total number of waves into the wave generator (4) and the wave generator (4) will generate waves. Step 2: Collect wave data from the first wave height meter (7), the second wave height meter (8), and the third wave height meter (9) respectively using the dynamic signal acquisition instrument (5) to obtain the propagation time of the same phase of the same wave from point A where the first wave height meter (7) is located to point B where the second wave height meter (8) is located. The coordinates of point A (where the first wave height meter (7) is located), point B (where the second wave height meter (8) is located), and point C (where the third wave height meter (9) is located) are set as follows: , , The distances between each point are as follows: and , The real-time wave data at points A and B are obtained using the first wave height meter (7) and the second wave height meter (8). When the set phase of a wave propagates to point A where the first wave height meter (7) is located, the dynamic signal acquisition instrument acquires the data at that moment. When the same phase of the wave propagates to point B where the second wave height meter (8) is located, the dynamic signal acquisition instrument acquires the data at that moment. The data is then sent to the terminal computer (6) to subtract the two times to obtain the propagation time. ; Step 3: Based on the obtained propagation time The dispersion relation and Newton's iteration method from wave theory are used to subsequently solve for the wave number. ; Since the wave generation sequence is A → B → C, the phase at point B where the second wave height meter (8) is located lags behind the phase at point A where the first wave height meter (7) is located; First, assume a simple harmonic wave at a water depth of... The propagation along the positive x-axis in the pool, its phase It is represented as: （1）； The phases of the three wave height gauges at locations A, B, and C are respectively; （2）； （3）； （4）； in, For time, Initial phase; wave angular frequency With period The relationship is: （5）； Then the wave angular frequency The actual cycle obtained through real-time monitoring This is obtained and used for subsequent wavenumber analysis. Solve for; For wavenumber This is determined by solving the dispersion equation of linear wave theory, which will... and and water depth Connecting them: （6）； in It is the acceleration due to gravity; When point B and point A are in phase, the following relationship holds: （7）； Substituting the phases of points A and B into equation (7), that is, substituting equations (2) and (3) into equation (8), we get: （8）； Then wave number for: （9）； The wavenumber is then calculated using Newton's iteration method. Verification of the calculation: First, the constructor Its root This is the solution to the dispersion equation; （10）； The iterative algorithm of Newton's method is as follows: （11）； in, It is the first The value of the next iteration. yes exist The first derivative at that point; The derivation is as follows: （12）； （13）； （14）； （15）； To initiate the iteration, a reasonable initial guess is required. That is, assuming To estimate: （16）； （17）； Substituting equations (10) and (15) into Newton's iteration algorithm equation (11), we get: （18）； Iterate until... Convergence, at which point the wavenumber can be proven. The correctness; Step 4: Calculate the propagation time required for the same wave of the same phase to travel from point A (where the first wave height meter (7) is located) to point C (where the third wave height meter (9) is located). ; When points A and C are in phase, the following relationship exists: （19）； Substituting the phases of points A and C into equation (19), we get: （20）； Based on the solved wavenumber Therefore, the time lag between point C and point A is... for: （21）； Step 5: Calculate the fall time of the freefall model (3) after release. ; Input the drop height of the drop model (3) in this experiment. According to Newton's kinematics formula for free fall: （22）； Since the free fall model (3) has an initial velocity of 0, substituting... and The falling time of the free-fall model (3) after release is obtained. for: （23）； in, It is the acceleration due to gravity; Step 6: Solve for the preset time of the release command sent by the falling body model (3). , Preset time for sending release command of free fall model The calculation formula is as follows: （24）； In the formula, The preset time for sending the release command to the falling model. The propagation time required for the same wave and phase to travel from the first wave height gauge (7) to the third wave height gauge (9) is given. This is the inherent delay time of the system. The model's fall time; Therefore, all three terms on the right side of the equation (24) are known. Substituting these known terms into equation (24), we finally obtain the preset time for sending the release command of the falling model. The expression: （25）； In the formula, For wave number, The distance between the first wave height gauge (7) and the third wave height gauge (9) is the distance between them. For wave frequency, The inherent delay time of the control system is fixed and known. The falling height of the free-falling model. For local gravitational acceleration, , , and All parameters are known. The preset time for sending the release command of the falling body model is obtained by solving the problem. Afterwards, the terminal computer continues to acquire real-time wave data using a wave height meter, detecting the target phase, wave period, and wave height. If the parameters remain stable, the system will release the wave at the preset time specified by the falling body model release command. If the parameters are unstable and cannot meet the test requirements, a release command is not sent, and the wave generator and wave height meter are debugged, then return to step 1. Step 7: After the terminal computer sends the release command, the control hook receives the command and executes the mechanical release operation. Under the action of the support structure's fixed column and the track slider, the object falls vertically and impacts the target. The impact data is collected using the acquisition device for subsequent data processing and analysis.

7. The determination method according to claim 6, characterized in that, In step 2, the actual wave height is obtained by calculating the height difference between the crest and trough phases of the same wave. The actual period of a wave is obtained by calculating the time difference between the same phase of adjacent waves passing through the same wave height meter. The actual wave height and actual period are compared with the preset wave height and preset period. If the deviation is within the set range, proceed to the next step. Otherwise, if the deviation is greater than the set range, adjust the wave generator and wave height meter, and return to step 1 to generate waves again.

8. The determination method according to claim 6, characterized in that, The preset time for sending the release command of the falling model as described in step 6 Calculation formula This is used to control the falling model to slam under a set wave phase, that is, when the same phase of the same wave propagates from the first wave height meter (7) to the third wave height meter (9), the falling model just enters the water and slams; assuming the propagation time required for the same phase of the same wave to propagate from the first wave height meter (7) to the third wave height meter (9) is During this period, a series of processes need to be completed, including releasing the falling model and the falling model impacting the water. The time factor that needs to be considered is the inherent delay time of the system. Falling time of the free-fall model The preset time for sending the release command of the falling model The sum of the times required for these three measurements is equal to the propagation time required for the same wave to travel from the first wave height gauge (7) to the third wave height gauge (9) in the same phase. They are equal, but due to the inherent delay time of the system... The model's fall time is a fixed value. Referring to the free fall formula, the preset time for sending the release command of the falling model is thus obtained. The calculation formula.

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