Model test method for upward wave quantity of open cargo hold of open box ship in waves

Abstract

The invention discloses a method for testing a wave uplift model of an open cargo hold of an open box ship in waves. The method comprises the following steps: step 1, simulating test environment conditions and test objects; step 2, performing tests, including performing a preliminary test and a basic test; and step 3, evaluating a test result. The method is wide in application range and high in test result precision.

Description

Technical Field

[0001] The present invention relates to the technical field of ships, and particularly relates to a method for model test of the overwash quantity on the open cargo hold of an open-top box ship in waves. Background Art

[0002] With the changes in the global economic and trade pattern, the demand for open-top box ships has increased significantly. The International Maritime Organization and classification societies stipulate that open-top box ships need to consider the influence of the overwash quantity on the open cargo hold. In the past, the model tests of the overwash quantity on the open cargo hold of open-top box ships were mostly occupied by foreign basins. Since 2020, two domestic basin scientific research institutions have started to provide support for the model tests of large open-top ships.

[0003] The existing technologies for obtaining the overwash quantity on the open cargo hold include numerical simulation technology and physical model test technology. Numerical simulation technology includes computational fluid dynamics (CFD) and empirical formula calculation; physical model test technology includes wave basin test and full-scale ship test at sea. Computational fluid dynamics (CFD) is to use professional software to construct a digital model of the ship and waves and simulate the overwash process. Empirical formula calculation is to summarize formulas based on a large amount of test data and actual navigation experience to estimate the overwash quantity. Full-scale ship test at sea is to install measuring equipment on the full-scale ship to record the overwash quantity during navigation. Wave basin test is to make a ship model in proportion in the basin, use a wave maker to simulate different sea conditions, and measure the overwash quantity through equipment such as pressure sensors and flow meters.

[0004] For the computational fluid dynamics (CFD) technology, the accuracy of the model depends on reasonable assumptions and empirical formulas, and its ability to simulate complex wave phenomena is limited, making it difficult to accurately capture dynamic changes.

[0005] For the empirical formula calculation technology, the applicable range is narrow. Usually, it is obtained based on specific ship types, sea conditions, and test conditions, and the calculation accuracy drops significantly.

[0006] For the full-scale ship test at sea technology, the risk is high. Severe sea conditions pose a threat to the safety of ships, personnel, and equipment, and the cost is high.

[0007] For the wave basin test technology, since the domestic basins started relatively late, problems such as how to accurately simulate environmental conditions such as sea waves and ship speed, how to truly construct the structural characteristics of the full-scale ship, how to fully evaluate the trim and center of gravity range of the actual operation of the ship, and how to design the test process cannot be accurately grasped. It is difficult to ensure the accuracy and reliability of the test. To avoid risks, there are often problems such as too many test conditions, high cost, and low efficiency; problems such as the test object and condition simulation being too conservative, affecting the economy of the ship. During the test, reasonable measures cannot be taken in time, resulting in problems such as increasing the number of test times and delaying the design and construction cycle.

[0008] The paper "Study on the evaluation method of deck waves for determining the freeboard of open container ships" (author Sun Anlin et al., China Shipbuilding Volume 60, Issue 3 (Total Issue 231)) discloses the study on the evaluation method of deck waves for determining the freeboard of open container ships. The prior art has the following deficiencies: This prior art proposes "covering the remaining five open cargo holds with flexible waterproof materials so as to contain the accumulated water caused by the inflow of waves", but it has the problem of conservative object simulation and cannot improve the economy of the ship.

[0009] The paper "The impact of DNV•GL's new regulations on the overall design of open multi-purpose ships and measures to reduce waves" (author He Xinyu et al., Ships, Issue 3, 2021, Issue 192) discloses the research on the overall design requirements of open multi-purpose ships. The existing technology has the following deficiencies: First, the prior art proposes that "the GM of the ship under all wave directions shall select the GM value corresponding to the resonance between the roll period and the spectrum peak period in the transverse wave. If the GM value corresponding to the resonance exceeds the maximum value of the ship's limit GM curve, the maximum value of the limit GM curve may be selected. For the three wave directions with poor results, the maximum value of the limit GM curve is then taken." The prior art has the problem that the method of taking the initial steady center height leads to a safe test result.

[0010] Second, the prior art proposes "to measure the water inflow from the upper waves in all wave directions for 1 hour in each condition, and then repeat the measurement in the three wave directions with poor results, and the additional trim value needs to be added to the open seakeeping model test". It has the problem of too many test conditions and long test time due to the 8 horizontal trim test conditions and the possibility of 8 additional trim test conditions being superimposed.

[0011] There is currently no effective solution to the above problems. Summary of the invention

[0012] In order to overcome the above-mentioned defects in the prior art, the present invention provides a model test method for wave load on an open cargo hold of an open box ship in waves.

[0013] The present invention solves the above technical problems through the following technical solutions: A model test method for wave load on an open cargo hold of an open box ship in waves, comprising: Step 1, simulating the test environment conditions and test objects; Step 2: Conducting tests, including preliminary tests and basic tests; The loading schemes during the test include the first loading scheme and the second loading scheme; The first loading scheme includes the combination of the deepest open draught T1, the horizontal trim TR1 and the initial metacentric height GM1 corresponding to the deepest open draught on the initial metacentric height limit curve; The second stowage plan includes a combination of the deepest draft T1 in open water navigation, the longitudinal trim TR1, and the initial metacentric height GM2. GM2 is the value of the initial metacentric height corresponding to the resonance between the actual ship's rolling period and the spectral peak period. If the resonance initial metacentric height value is greater than the maximum initial metacentric height value GM3 on the initial metacentric height limit curve or the maximum initial metacentric height value GM4 corresponding to the deepest draft loading condition of the actual ship in open water, then one of GM3 and GM4 is selected as GM2. The preliminary tests include: adjusting the ship model to the first stowage plan, without arranging containers in the open cargo holds, establishing the preliminary test conditions, respectively measuring the water inflow into each open cargo hold of the ship model in all preliminary test conditions, and determining the most unfavorable cargo hold for each of the five wave directions of head sea, bow oblique sea, beam sea, stern oblique sea, and following sea. The basic tests include: establishing the basic test conditions, dynamically adjusting the container arrangement in the open cargo holds according to the wave direction change. Under any wave direction, the most unfavorable cargo hold obtained from the preliminary test for this wave direction is simulated as having no containers, and the other open cargo holds are fully loaded with containers above the open deck. The ship model is adjusted to the first stowage plan and the second stowage plan respectively, and the water inflow into each open cargo hold of the ship model is measured in all basic test conditions, and the most unfavorable wave direction and the maximum hourly water inflow height of the open cargo hold are determined. Step 3, evaluate the test results.

[0014] Further, in step 1, the simulation of the test environmental conditions includes simulating the wave spectrum and the wave direction, and the simulation of the test object includes determining the ship model used to simulate the actual ship, determining the ship model stowage plan corresponding to each test condition and debugging, and determining the test speed; determining the ship model stowage plan corresponding to each test condition includes: determining the draft, trim, initial metacentric height, longitudinal moment of inertia, and transverse moment of inertia, roll natural period, and decay coefficient of the stowage plan corresponding to each test condition.

[0015] Further, in step 1, the ship model can use a spare propeller and a spare rudder instead of the designed propeller and the designed rudder.

[0016] Further, in step 2, when the natural rolling period of the actual ship is twice the encounter period, under the stern oblique sea and following sea conditions, increase the minimum maneuvering speed by 1 or 2 kn, and determine the propeller speed N corresponding to this speed in still water. S 1, conduct the test at the propeller speed N S 1.

[0017] Further, in step 2, the stowage plan during the test includes the third stowage plan; the third stowage plan includes a combination of the deepest draft T1 in open water navigation, the additional trim TR2, and the initial metacentric height value GM1 corresponding to the deepest draft on the initial metacentric height limit curve.

[0018] Further, in Step 2, the loading plan during the test includes the fourth loading plan; the fourth loading plan includes a combination of the deepest draft T1 during open sea navigation, additional trim TR2, and initial metacentric height GM2, where GM2 is the initial metacentric height value corresponding to the resonance between the actual ship's rolling period and the spectral peak period; if the resonance initial metacentric height value is greater than the maximum initial metacentric height value GM3 on the initial metacentric height limit curve or the maximum initial metacentric height value GM4 corresponding to the deepest draft loading condition of the actual ship in the open sea, then one of GM3 and GM4 is selected as GM2.

[0019] Further, in Step 2, conducting the test also includes conducting additional tests; establishing additional test conditions; when conducting additional tests, the ship model is adjusted to the third loading plan, containers are arranged in the same way as in the basic test, and the additional test is carried out in the most unfavorable wave direction obtained from the basic test, and the requirements of the additional test are the same as those of the basic test; subsequently, the ship model is adjusted to the fourth loading plan and tested according to the test method under the third loading plan.

[0020] Further, in Step 3, the evaluation includes: comparing with the evaluation criteria and the countermeasures taken when exceeding the evaluation criteria.

[0021] Further, the evaluation criteria are that the maximum hourly water ingress height of any open cargo hold measured in the test should not exceed the maximum allowable value specified for each navigation area.

[0022] Further, the countermeasures taken when exceeding the evaluation criteria include: giving priority to conducting test conditions in more unfavorable wave directions. For test conditions that exceed the evaluation criteria, additional measures such as increasing the simulation of cargo covers stacked on the hatch coaming of the cargo hold or on the open deck are adopted to reduce the water entering the empty cargo hold, and Step 2 is repeated for testing.

[0023] The beneficial effects of the present invention are as follows: The method of the present invention can simulate complex wave phenomena and accurately capture dynamic changes. The method of the present invention has a wide range of applications and can be applied to open-top container ships in all navigation areas to simulate the ship motion responses in various navigation area sea conditions, and the test results have high accuracy. The method of the present invention can avoid the problem of high technical risks in sea trials of actual ships, prevent bad sea conditions from threatening the safety of ships, personnel and equipment, and reduce costs.

[0024] The method of the present invention establishes the loading methods of the ship model under the test conditions of preliminary tests, basic tests, and additional tests, and gives the determination methods of parameters such as draft, trim, initial metacentric height, longitudinal moment of inertia and transverse moment of inertia, roll natural period, and decay coefficient.

[0025] The present invention adopts the technical feature that "GM1 is the metacentric height value corresponding to the deepest draft of the open type on the metacentric height limit curve; GM2 is the metacentric height value corresponding to the resonance between the actual ship rolling period and the spectral peak period; if the resonance metacentric height value is greater than the maximum metacentric height value GM3 on the metacentric height limit curve or the maximum metacentric height value GM4 corresponding to the deepest draft loading condition of the actual ship open type, then one of GM3 and GM4 is selected as GM2". GM1 and GM4 fully consider the variation range of the metacentric height of the actual ship in light and heavy cargo operations, overcome the problem of the test results being on the safe side caused by the existing metacentric height value-taking method, and ensure the accuracy of the test.

[0026] The present invention adopts the technical feature that "the most unfavorable cargo holds in the head sea, bow quartering sea, beam sea, quartering sea, and following sea directions are obtained through preliminary tests, and the container arrangements in each test condition and each open cargo hold are dynamically adjusted according to the wave direction changes". This open cargo hold container arrangement method fully considers the loading requirements of the actual ship operation, overcomes the problem of overly conservative simulation of the test object in the existing technology, and improves the economy of the ship.

[0027] The present invention adopts the technical feature that "the basic test conditions are first tested in all wave directions and then in the beam sea, and the additional test conditions are tested in the most unfavorable wave directions obtained from the basic tests". The 6 basic test conditions and 2 additional test conditions fully evaluate the influence of the most unfavorable wave direction and the superposition of the most unfavorable wave direction and the most unfavorable ship model loading, overcome the problems of a large number of test conditions and long test time caused by the possible superposition of 8 horizontal trim test conditions and 8 additional trim test conditions in the existing technology, and improve the test efficiency while ensuring the accuracy of the test.

[0028] The method of the present invention provides countermeasures when the assessment of the green water volume on the open cargo hold of the ship is unreasonable, ensuring the smooth completion of the test. Detailed implementation mode

[0029] The following is a preferred embodiment to more clearly and completely illustrate the present invention.

[0030] A model test method for the green water volume on the open cargo hold of an open-top box ship in waves, which includes: Step 1, simulate the test environmental conditions and test object; Step 2, conduct tests, including preliminary tests and basic tests; The loading plans during the tests include the first loading plan and the second loading plan; The first loading plan includes the combination of the deepest draft T1 for open-top navigation, the horizontal trim TR1, and the metacentric height value GM1 corresponding to the deepest draft of the open type on the metacentric height limit curve; The second stowage plan includes a combination of the deepest draft T1 during open sea voyage, the longitudinal trim TR1, and the initial metacentric height GM2. GM2 is the initial metacentric height value corresponding to the resonance between the actual ship's rolling period and the spectral peak period. If the resonance initial metacentric height value is greater than the maximum initial metacentric height value GM3 on the initial metacentric height limit curve or the maximum initial metacentric height value GM4 corresponding to the deepest draft loading condition of the actual ship in the open sea, then one of GM3 and GM4 is selected as GM2. The preliminary tests include: adjusting the ship model to the first stowage plan, not arranging any containers in the open cargo holds, establishing the preliminary test conditions, measuring the water inflow into each open cargo hold of the ship model during all preliminary test conditions respectively, and determining the most unfavorable cargo hold for each of the five wave directions of head sea, bow quartering sea, beam sea, stern quartering sea, and following sea. The basic tests include: establishing the basic test conditions, dynamically adjusting the container arrangement in the open cargo holds according to the wave direction changes. Under any wave direction, the most unfavorable cargo hold obtained from the preliminary tests for this wave direction is simulated as having no containers, and the other open cargo holds are fully loaded with containers above the open deck. The ship model is adjusted to the first stowage plan and the second stowage plan respectively, and the water inflow into each open cargo hold of the ship model is measured during all basic test conditions respectively, and the most unfavorable wave direction and the maximum hourly water inflow height of the open cargo hold are determined. Step 3, evaluate the test results.

[0031] Among them, Step 1 belongs to the pre - test preparation stage, Step 2 is the test stage, and Step 3 is the test result evaluation stage. When conducting the tests in Step 2, it should be carried out under the test environmental conditions and test objects in Step 1. Therefore, the content described in "the pre - test preparation stage" below is also the conditions to be met when conducting the tests in the test stage of Step 2.

[0032] To avoid repetition, when the following text quotes the previous text, the way of using the serial number of the quoted content plus quotation marks to replace the quoted content is adopted. For example, when the following text quotes "1.1.2" in the previous text, "1.1.2" in the following text means the content in "1.1.2 Wave direction angle" in "1. Test pre - test preparation stage". The specific content of "1.1.2 Wave direction angle" will not be repeated in the following text.

[0033] 1. Test pre - test preparation stage 1.1 Simulation of environmental conditions The simulation of the test environmental conditions includes simulating the wave spectrum and simulating the wave direction.

[0034] 1.1.1 Wave spectrum 1.1.1.1 The model test shall be carried out in long-crested irregular waves. The JONSWAP spectrum (i.e., the Joint North Sea Wave Project, English name: Joint North Sea Wave Project, abbreviated as JONSWAP) can be adopted for the test. For ships operating only in restricted sea areas, other wave spectra approved by the competent authority can be adopted.

[0035] 1.1.1.2 For ships sailing in different navigation areas, the test shall generate waves with a significant wave height in accordance with Table 1 under the most unfavorable wave period (crossing zero).

[0036] 1.1.2 Wave direction angle The model test shall be carried out at least for the following wave direction angles: (1) Head sea (wave direction angle is 180°); (2) Forward quartering sea (wave direction angle is 135° or 225°); (3) Beam sea (wave direction angle is 90° / 270°); (4) After quartering sea (wave direction angle is 45° or 315°); (5) Following sea (wave direction angle is 0° / 360°).

[0037] 1.2 Simulation of the test object 1.2.1 Integrity of the ship model 1.2.1.1 For the test model, in addition to requiring the shape of the underwater part to be similar to that of the actual ship, the shape of the above-water part (including structures such as freeboard, upper deck, bulwark, superstructure up to the wheelhouse, deckhouse, spray guard, wave breaker, hatch coaming of cargo hold, chimney, etc. that affect seawater entering the cargo hold) also meets the similarity with the actual ship.

[0038] 1.2.1.2 The openings on the above-mentioned structures and the gaps between the structures, such as the observation holes and mooring holes on the spray guard, also meet the similarity with the actual ship.

[0039] 1.2.1.3 The self-propelled unconstrained model is adopted for the test, and the appendages such as propeller, rudder, bilge keel, etc. should be similar to those of the actual ship.

[0040] 1.2.1.4 The ship model can use spare propellers and spare rudders to replace the designed propellers and designed rudders, which is convenient for designers to flexibly adjust the test schedule.

[0041] 1.2.1.5 When hatch covers are provided for individual cargo holds, the cargo holds in the model test can be simulated as having hatch covers, and containers are arranged on them, and seawater does not enter these cargo holds.

[0042] 1.2.2 Loading plan and debugging method of the ship model corresponding to each test condition 1.2.2.1 During the test, the draft of the model ship is adjusted to the position corresponding to the deepest draft of the full-scale ship in open sea navigation. That is: during the test, according to the scale ratio, the draft of the model ship is adjusted to a position similar to the deepest draft T (minimum freeboard) of the full-scale ship in open sea navigation.

[0043] 1.2.2.2 The longitudinal trim of the model ship is adjusted to horizontal trim.

[0044] 1.2.2.3 When the longitudinal trim of the full-scale ship in open sea navigation at the deepest draft exceeds the range of ±0.5% of the ship length L during operation, a loading plan with additional longitudinal trim should be added, and additional test conditions should be added. Herein, the ship length L refers to the ship length defined in the current "International Convention on Load Lines". The additional longitudinal trim is consistent with the additional longitudinal trim in the probabilistic damage stability calculation of the full-scale ship carried out in accordance with the current "International Convention for the Safety of Life at Sea".

[0045] 1.2.2.4 The debugging method for the initial metacentric height GM of the model ship: (1) For the preliminary test condition, it is adjusted to GM1 corresponding to the deepest draft in open sea navigation on the GM limit curve. The GM limit curve is obtained from the probabilistic damage stability calculation of the full-scale ship carried out in accordance with the "International Convention for the Safety of Life at Sea".

[0046] (2) For the basic test condition, first, in the five wave directions of "1.1.2", while keeping the initial metacentric height GM1 in item (1) of this article unchanged, conduct the basic test in the five wave directions; then, in the beam sea of "1.1.2", adjust it to GM2 corresponding to the resonance of the full-scale ship's rolling period and the spectral peak period, and conduct the basic test in the beam sea.

[0047] (3) When the resonance GM2 in item (2) of this article far exceeds the maximum GM3 on the GM limit curve or the maximum GM4 corresponding to the deepest draft loading condition of the full-scale ship in open sea, then in the beam sea, select one of GM3 and GM4 as GM2 and conduct the basic test in the beam sea.

[0048] (4) For the additional test condition (if any), it is adjusted to the initial metacentric height GM1 in item (1) of this article. First, conduct the additional test in the most unfavorable wave direction obtained from the basic test; then, adjust it to the initial metacentric height GM2 in item (2) or (3) of this article above and conduct the additional test in the most unfavorable wave direction.

[0049] 1.2.2.5 From "1.2.2.1" to "1.2.2.4", determine the loading plan of the model ship corresponding to each test condition. Adjust the center of gravity, longitudinal moment of inertia, and transverse moment of inertia of the model ship to be similar to those of the full-scale ship according to each loading plan. The debugging parameters of the model ship for each loading plan are shown in Table 2.

[0050] 1.2.2.6 When there is no specific requirement for the longitudinal radius of inertia of the ship model, it can be taken as 0.25Lpp; when there is no specific requirement for the transverse radius of inertia of the ship model, it can be taken as 0.35B.

[0051] 1.2.2.7 For each loading plan, a free rolling decay test is carried out in still water at zero speed to measure the natural rolling period, decay coefficient, etc. of the ship model.

[0052] 1.2.3 Test speed The ship model should be tested at least at the following speeds: (1) The maximum sustained speed in head seas and bow quartering seas; (2) The minimum manoeuvring speed in quartering seas and following seas; (3) Zero speed in beam seas.

[0053] Among them, the zero speed in beam seas is required when the ship model is in a non-powered state.

[0054] 1.2.3.1 Method for determining the maximum sustained speed: (1) According to the maximum continuous power of the main engine (SMCR), combined with the results of the ship model speed performance test in still water, predict the speed V in still water; (2) Select 4 propeller revolutions per minute N1, N2, N3, N4 in still water, measure the corresponding speeds V1, V2, V3, V4, and interpolate from V to obtain the propeller revolution speed N; (3) In regular waves, with the propeller revolution speed set to N respectively in the case of head seas or bow quartering seas, and keep the course stable by steering, measure the maximum sustained speed V considering stall in head seas W 1 and the maximum sustained speed V W 2 in bow quartering seas.

[0055] 1.2.3.2 The minimum manoeuvring speed is calculated in accordance with the "Guidelines for Determining the Minimum Propulsion Power for Maintaining Ship Maneuverability in Severe Sea Conditions (MEPC.1 / Cir.850 / Rev.2)": V S = max(4, V ref - 10(A R - 0.009)) Where: V ref is the minimum reference course-keeping speed, obtained by the calculation method given in Table 3; A R is the ratio of the actual ship rudder area Ar to the underwater lateral immersed area A of the ship corrected for width influence LS , A R = A r / A LS . In the following table, A F / AL is the lateral windward area \(A\) of the actual ship F and the longitudinal windward area \(A\) L ratio

[0056] 1.2.3.3 For the ship speeds \(V\) and \(V\) in still water S respectively determine the corresponding propeller revolutions \(N\) and \(N\) S . Under the head sea and bow quartering sea conditions, the ship model is tested at the propeller revolution \(N\); under the beam sea condition, the ship model is tested at zero speed (stationary state); under the stern quartering sea and following sea conditions, the ship model is tested at the propeller revolution \(N\) S .

[0057] 1.2.3.4 When the natural rolling period of the actual ship is twice the encounter period, under the stern quartering sea and following sea conditions, the above minimum maneuvering speed can be increased by 1 or 2 kn to avoid the problem of excessive water ingress into the open cargo hold due to resonant rolling and prevent the ship model from being damaged or even the test from failing. Determine the propeller revolution \(N\) corresponding to this speed in still water S 1, and conduct the test at the propeller revolution \(N\) S 1

[0058] 2 Test stage The test stage should be carried out under the conditions satisfying the above "1. Pre - test preparation stage". The test content in the above "1. Pre - test preparation stage" is included in this test stage

[0059] The over - wash volume test for the open cargo hold includes: preliminary test, basic test and additional test (if any).

[0060] 2.1 General requirements 2.1.1 The test time for each test condition should be at least corresponding to 1 h of the actual ship time (except for the preliminary test), and each test condition can consist of multiple test voyages

[0061] 2.1.2 In addition to measuring the usual parameters (ship model motion, speed, relative motion, rudder angle, etc.) for each test voyage, the water inflow into each open cargo hold should also be measured. The cumulative water inflow for multiple times is the measured over - wash volume

[0062] 2.1.3 After each test voyage, the water pumped into the hold should be drained and measured to avoid significant influence on the initial metacentric height, moment of inertia and displacement due to accumulated water

[0063] 2.2 Preliminary test 2.2.1 The preliminary test is used to determine the most unfavorable cargo hold for each wave direction in "1.1.2" and provide a basis for the container arrangement in the open cargo hold in the basic test and additional test (if any).

[0064] 2.2.2 Adjust the ship model to the stowage plan A001 in "1.2.2.5", without arranging containers in all open cargo holds. Conduct tests at the ship speed specified in "1.2.3" in the five wave directions in "1.1.2". The preliminary test conditions are shown in Table 4.

[0065] 2.2.3 The test time for the preliminary test conditions does not need to correspond to the actual ship time of 1 h.

[0066] 2.2.4 Measure the water inflow into each open cargo hold in the preliminary test conditions to determine the most unfavorable cargo hold in each wave direction. Take the case of setting 3 open cargo holds (assuming the hatch opening area of the first cargo hold is 400 m 2 , the hatch opening area of the second cargo hold is 800 m 2 , and the hatch opening area of the third cargo hold is 500 m 2 ). See Table 5 for details.

[0067] As can be seen from the above table, the most unfavorable cargo hold in head seas is the first cargo hold, the most unfavorable cargo hold in bow quartering seas is the third cargo hold, the most unfavorable cargo hold in beam seas is the second cargo hold, the most unfavorable cargo hold in stern quartering seas is the second cargo hold, and the most unfavorable cargo hold in following seas is the third cargo hold.

[0068] 2.3 Basic tests 2.3.1 The basic tests are used to measure the water inflow into each open cargo hold of the ship model under the basic test conditions, and to determine the most unfavorable wave direction and the maximum hourly water inflow height of the open cargo hold.

[0069] 2.3.2 During the test, the container arrangement in the open cargo holds of the ship model is dynamically adjusted according to the wave direction change. That is, under a certain wave direction in "1.1.2", the most unfavorable cargo hold in this wave direction obtained from the preliminary test is simulated as having no containers, and the other open cargo holds are fully loaded with containers that are higher than the open deck.

[0070] 2.3.3 Keep the ship model stowed to A001 unchanged. First, adjust the container arrangement in the open cargo holds in each wave direction in "1.1.2", and then conduct tests at the ship speed specified in "1.2.3" in this wave direction. The tests in the five wave directions in "1.1.2" are carried out in the same way. Adjust the ship model to the stowage plan A002 in "1.2.2.5", arrange the containers in the same way, and conduct tests at zero speed in beam seas. The basic test conditions are shown in Table 6.

[0071] 2.3.4 Measure the water inflow into each open cargo hold under the basic test conditions and determine the most unfavorable wave direction. Still taking the case of setting 3 open cargo holds as an example (assuming the open hatch area of the first cargo hold is 400 m 2 , the open hatch area of the second cargo hold is 800 m 2 , and the open hatch area of the third cargo hold is 500 m 2 ). See Table 7 for details.

[0072] As can be seen from the above table, the most unfavorable wave direction is bow quartering sea, and the maximum hourly water inflow height of the open cargo hold is 240 mm / h.

[0073] 2.4 Additional tests 2.4.1 The additional tests are used to measure the water inflow into each open cargo hold of the ship model under the additional test conditions and determine the maximum hourly water inflow height of the open cargo hold.

[0074] 2.4.2 According to the provisions of "1.2.2.3", if a loading plan with additional trim needs to be added, the ship model is adjusted to the loading plan A003 in "1.2.2.5". Similarly, containers are arranged and the test is carried out in the most unfavorable wave direction obtained from the basic test. The requirements of the additional test are the same as those of the basic test. Subsequently, the ship model is adjusted to the loading plan A004 in "1.2.2.5" and the test is carried out in the same way.

[0075] The additional test conditions are shown in Table 8.

[0076] 3 Evaluation of test results The evaluation includes: comparison with the evaluation criteria and the countermeasures taken when exceeding the evaluation criteria.

[0077] 3.1 Evaluation criteria 3.1.1 Evaluation criteria for the overtopping volume test of open cargo holds The overtopping volume per hour of the open cargo hold = the open hatch area × the hourly water inflow height.

[0078] The evaluation criterion is that the maximum hourly water inflow height measured in any open cargo hold during the test should not exceed the maximum allowable value specified for each navigation area.

[0079] The maximum allowable value of the hourly water inflow height of the open cargo hold in each navigation area is shown in Table 9.

[0080] 3.2 Evaluation of the rationality of the overtopping volume model test results of open cargo holds 3.2.1 For a ship model that meets the following requirements, the model test results are reasonable: In the basic test conditions and additional test conditions (if any), the maximum hourly water ingress height measured for any open cargo hold does not exceed the maximum allowable value specified for each navigation area.

[0081] That is: When there are no additional test conditions, in the basic test conditions, the maximum hourly water ingress height measured for any open cargo hold does not exceed the maximum allowable value specified for each navigation area; When there are additional test conditions, in the basic test conditions and additional test conditions, the maximum hourly water ingress height measured for any open cargo hold does not exceed the maximum allowable value specified for each navigation area; 3.2.2 Reasonably arrange the order of test conditions, give priority to the more adverse wave direction conditions. For test conditions that exceed the evaluation criteria, promptly adopt reasonable countermeasures. The countermeasures include adding simulated cargo covers stacked on the hatch coaming of the cargo hold or on the open deck as additional measures to reduce water ingress into the empty cargo hold; repeat the tests in "2.3" and "2.4", including the basic test conditions and additional test conditions (if any). For this situation, impose corresponding restrictions during the operation of the actual ship in the open state.

[0082] The method for fully simulating the test object in the present invention can truly construct the structural characteristics of the actual ship and accurately reflect the seakeeping characteristics of the actual ship; the debugging method of the ship model loading plan corresponding to each test condition can fully assess the longitudinal inclination and center of gravity range of the actual ship operation; the container layout plan of each test condition determined by the test method is closer to the actual ship operation while considering the most unfavorable situation; the method for determining the minimum maneuvering speed in the special cases of following sea and quartering sea conditions can avoid the problem of excessive water ingress into the open cargo hold caused by resonant rolling and prevent the damage of the ship model and even the failure of the test; the determination method of each test condition assesses the influence of the most adverse wave direction, the superposition of the most adverse wave direction and the most unfavorable ship model loading, simplifies the number of conditions, and ensures the test accuracy and improves the efficiency.

[0083] The present invention method establishes the loading methods of the ship model under the preliminary test, basic test, and additional test conditions, and gives the determination methods of parameters such as draft, longitudinal inclination, initial metacentric height, longitudinal moment of inertia and transverse moment of inertia, roll natural period, and decay coefficient.

[0084] The paper "The Impact of New DNV•GL Standards on the Overall Design of Open Multipurpose Ships and Measures to Reduce Waves" (author He Xinyu et al., Ships, Issue 3, 2021, Issue 192 in total) proposes that "the GM of the ship under all wave directions shall select the GM value corresponding to the resonance between the roll period and the spectrum peak period in the transverse wave. If the GM value corresponding to the resonance exceeds the maximum value of the ship's limit GM curve, the maximum value of the limit GM curve can be selected. For the three wave directions with poor results, the maximum value of the limit GM curve is taken", and the present invention adopts "GM1 GM1 is the initial steady center height value corresponding to the deepest draft of the exposure on the initial steady center height limit curve; GM2 is the initial steady center height value corresponding to the resonance between the actual ship rolling period and the spectrum peak period; if the resonant initial steady center height value is greater than the maximum initial steady center height value GM3 on the initial steady center height limit curve or the maximum initial steady center height value GM4 corresponding to the actual ship's deepest draft loading condition, then one of GM3 and GM4 is selected as the technical feature of GM2". GM1 and GM4 fully consider the variation range of the initial steady center height of the actual ship in operation with light and heavy cargo, overcome the problem of the test result biased to safety caused by the initial steady center height value selection method in the prior art, and ensure the accuracy of the test.

[0085] The paper “Study on Deck Wave Assessment Method for Determining Freeboard of Open Container Ships” (author Sun Anlin et al., China Shipbuilding Vol. 60, No. 3 (No. 231 in total)) proposes that “the remaining five open cargo holds shall be covered with flexible waterproof materials to contain water accumulation caused by wave ingress”, while the present invention adopts the technical feature of “obtaining the most unfavorable cargo holds for each of the five wave directions of head waves, bow oblique waves, transverse waves, stern oblique waves and following waves through preliminary tests, and dynamically adjusting the container layout in each test condition and each open cargo hold according to the change of wave direction”. This method of container layout in open cargo holds fully considers the loading needs of actual ship operation, overcomes the problem of conservative simulation of test objects in the prior art, and improves the economy of the ship.

[0086] The paper "The Impact of DNV•GL's New Standards on the Overall Design of Open Multipurpose Ships and Measures to Reduce Waves" (author He Xinyu et al., Ships, Issue 3, 2021, Issue 192 in total) proposes "to measure the amount of wave water inflow under all wave directions, 1 hour for each condition, and then repeat the measurement in the three wave directions with poor results. Additional trim values ​​need to be added to the open seakeeping model test". The present invention adopts the technical feature of "the basic test conditions are first tested under all wave directions and then in transverse waves, and the additional test conditions are tested in the most unfavorable wave direction obtained in the basic test". The 6 basic test conditions and 2 additional test conditions fully assess the influence of the most unfavorable wave direction, the most unfavorable wave direction and the most unfavorable ship model loading. The problems of the existing technology of 8 horizontal trim test conditions and long test time caused by the possible superposition of 8 additional trim test conditions are overcome, thereby ensuring the accuracy of the test while improving the test efficiency.

[0087] The method of the present invention provides countermeasures to be taken when the assessment of the amount of water splashing into the open cargo hold of a ship is unreasonable, ensuring the smooth completion of the test.

[0088] The present invention has the following advantages: (1) The method of the present invention can simulate complex wave phenomena and accurately capture dynamic changes; (2) The method of the present invention has a wide range of applications and can be applied to open-top container ships in all navigation areas to simulate the ship motion responses under various sea conditions in different navigation areas, with high accuracy of test results; (3) The method of the present invention can avoid the problem of high technical risks in sea trials of actual ships, prevent bad sea conditions from threatening the safety of ships, personnel and equipment, and reduce costs.

[0089] (4) The method of the present invention accurately simulates environmental conditions such as sea waves and ship speed, truly constructs the structural characteristics of an actual ship, determines the container layout plan for each test condition by test methods, fully examines the trim and center of gravity ranges during actual ship operation, scientifically and reasonably designs the test process, provides countermeasures to be taken when the assessment of the amount of water splashing into the open cargo hold of a ship is unreasonable, ensuring the accuracy and reliability of the test; avoiding being overly conservative in simulating the test objects and conditions, which may affect the economy of the ship; providing reasonable countermeasures for various special situations during the test, ensuring the smooth completion of the test.

[0090] The present invention innovatively constructs a model test method for the amount of water splashing into the open cargo hold of an open-top container ship in waves, filling the gaps in the existing specifications in terms of details and depth, providing a more comprehensive implementation basis and guiding criteria, and providing guarantee for the safe navigation of ships in complex sea conditions.

[0091] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only for illustration purposes. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A model test method for the amount of water splashing into the open cargo hold of an open box ship in waves, characterized in that, It includes: Step 1: Simulate the test environment conditions and the test object. Step 2: Conduct tests, including preliminary tests and basic tests. The loading plans during the tests include the first loading plan and the second loading plan. The first loading plan includes the combination of the deepest draft T1 during open-sea navigation, the horizontal trim TR1, and the metacentric height value GM1 corresponding to the deepest draft on the metacentric height limit curve. The second loading plan includes the combination of the deepest draft T1 during open-sea navigation, the horizontal trim TR1, and the metacentric height GM2, where GM2 is the metacentric height value corresponding to the resonance between the actual ship's rolling period and the spectral peak period; if the resonance metacentric height value is greater than the maximum metacentric height value GM3 on the metacentric height limit curve or the maximum metacentric height value GM4 corresponding to the actual ship's deepest draft loading condition, then select one of GM3 and GM4 as GM2. The preliminary tests include: Adjust the ship model to the first loading plan, do not arrange containers in the open cargo holds, establish the preliminary test conditions, measure the water inflow into each open cargo hold of the ship model during all preliminary test conditions respectively, and determine the most unfavorable cargo hold for each of the five wave directions of head sea, bow quartering sea, beam sea, stern quartering sea, and following sea. The basic tests include: Establish the basic test conditions, the container arrangement in the open cargo holds is dynamically adjusted according to the wave direction. Under any wave direction, the most unfavorable cargo hold obtained from the preliminary tests for this wave direction is simulated as having no containers, and the other open cargo holds are fully loaded with containers above the open deck. The ship model is adjusted to the first loading plan and the second loading plan respectively, measure the water inflow into each open cargo hold of the ship model under all basic test conditions respectively, and determine the most unfavorable wave direction and the maximum hourly water inflow height of the open cargo hold. Step 3: Evaluate the test results.

2. The wave overtopping quantity model test method for the open cargo hold of an open box ship in waves according to claim 1, characterized in that, In Step 1, the simulation of the test environment conditions includes simulating the sea wave spectrum and the wave direction, and the simulation of the test object includes determining the ship model used to simulate the actual ship, determining and debugging the ship model loading plan corresponding to each test condition, and determining the test speed. Determining the ship model loading plan corresponding to each test condition includes: Determining the draft, trim, metacentric height, longitudinal moment of inertia, transverse moment of inertia, natural rolling period, and decay coefficient of the loading plan corresponding to each test condition.

3. The model test method for the amount of water boarding on the open cargo hold of an open box ship in waves according to claim 1, wherein In Step 1, the ship model can use a spare propeller and a spare rudder instead of the designed propeller and the designed rudder.

4. The wave overtopping quantity model test method for the open cargo hold of an open box ship in waves as claimed in claim 1, wherein, In Step 2, when the natural rolling period of the actual ship is twice the encounter period, under the conditions of following sea and quartering sea, increase the minimum maneuvering speed by 1 or 2 knots, and determine the propeller speed N corresponding to this speed in still water. S 1. Conduct tests at the propeller speed N S 1.

5. The method for model test of the amount of water splashing into the open cargo hold of an open box ship in waves according to claim 1, characterized in that, In Step 2, the loading plans during the tests include the third loading plan; the third loading plan includes the combination of the deepest draft T1 during open-sea navigation, the additional trim TR2, and the metacentric height value GM1 corresponding to the deepest draft on the metacentric height limit curve.

6. The method for the model test of the overwashing volume of the open cargo hold of an open box ship in waves as described in claim 5, characterized in that, In Step 2, the loading plans during the tests include the fourth loading plan; the fourth loading plan includes the combination of the deepest draft T1 during open-sea navigation, the additional trim TR2, and the metacentric height GM2, where GM2 is the metacentric height value corresponding to the resonance between the actual ship's rolling period and the spectral peak period; if the resonance metacentric height value is greater than the maximum metacentric height value GM3 on the metacentric height limit curve or the maximum metacentric height value GM4 corresponding to the actual ship's deepest draft loading condition, then select one of GM3 and GM4 as GM2.

7. The method for model test of the amount of water shipped over the open cargo hold of an open box ship in waves as described in claim 6, characterized in that, In Step 2, conducting the test also includes conducting additional tests; establishing the additional test conditions; when conducting the additional tests, the ship model is adjusted to the third loading plan, the containers are arranged in the same way as in the basic test, and the additional tests are carried out in the most unfavorable wave direction obtained from the basic test. The requirements for the additional tests are the same as those for the basic test; subsequently, the ship model is adjusted to the fourth loading plan, and the test is carried out according to the test method under the third loading plan.

8. The method for model test of overtopping volume on the open cargo hold of an open box ship in waves as claimed in claim 1, wherein In Step 3, the evaluation includes: comparing with the evaluation criteria and the countermeasures to be taken when the evaluation criteria are exceeded.

9. The wave impact model test method for the open cargo hold of an open box ship in waves according to claim 8, characterized in that, The evaluation criteria are that the maximum hourly water inflow height of any open cargo hold measured in the test should not exceed the maximum allowable value specified for each navigation area.

10. The wave overtopping quantity model test method for the open cargo hold of an open box ship in waves according to claim 8, characterized in that, The countermeasures to be taken when the evaluation criteria are exceeded include: giving priority to conducting the test conditions in the more unfavorable wave directions. For the test conditions that exceed the evaluation criteria, additional measures are taken, such as increasing the simulation of the cargo covers stacked on the hatch coaming of the cargo hold or on the open deck, as an additional measure to reduce the water entering the empty cargo hold, and repeating Step 2 to conduct the test.

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