Test method for effectiveness of open cargo hold drainage ports on open ships

Abstract

The present invention discloses a method for testing the effectiveness of open cargo hold drainage ports on open vessels. The method comprises: simulating test environmental conditions and test objects; determining the most unfavorable open cargo hold of an open container vessel; simulating the volume of water flooded in the open cargo holds of the open vessel; injecting water into each open cargo hold; conducting an effectiveness test of the open cargo hold drainage ports; and evaluating the test results. The method of the present invention has a wide range of applications, high accuracy, reliability, repeatability, and safety.

Description

Technical Field

[0001] The present invention relates to the technical field of ships, and in particular to a method for testing the effectiveness of an open cargo hold drainage port on an open ship. Background Art

[0002] In recent years, demand for open-deck vessels has surged. IMO and classification societies have tightened safety and seaworthiness requirements, requiring open-deck vessels to examine the discharge capacity of open cargo hold freeing ports. The placement of freeing ports is closely linked to ship stability and longitudinal strength. Proper design and accurate verification of their effectiveness can reduce shipbuilding costs and operational risks.

[0003] Existing technologies for verifying the effectiveness of freeing ports include numerical simulation and physical model testing. Numerical simulation, namely computational fluid dynamics (CFD), and physical model testing, namely wave tank testing. CFD simulation uses specialized software to construct a digital model of the ship and waves, simulating the wave action on the open cargo hold and the drainage of the freeing ports. Wave tank testing involves constructing a scaled ship model in a tank, using a wave generator to simulate various sea conditions, and observing the wave action on the open cargo hold and the drainage of the freeing ports.

[0004] When a ship is sailing, the amount of water in the open cargo hold increases due to waves and rainfall, and the amount of water decreases due to drainage from the drainage ports. These changes are dynamic and are related to many factors, including the instantaneous wave volume, the simultaneous drainage of several drainage ports on the ship, and the movement of the ship in the waves. Computational fluid dynamics (CFD) technology has limited ability to simulate complex wave phenomena and it is difficult to accurately capture dynamic changes.

[0005] Wave tank testing technology started late in China, so we cannot accurately grasp how to truly construct the structural characteristics of a real ship, how to construct the structural characteristics of the drainage port, how to simulate the flooded volume of the open cargo hold, how to design the test process, and other issues. Therefore, it is difficult to ensure the accuracy and reliability of the test.

[0006] The model test of the effectiveness of open cargo hold drainage ports on open ships simulates the dynamic process of a ship sailing in complex sea conditions, with waves, rainwater, and other water continuously accumulating in the open cargo hold, paralyzing the ship's drainage system, and relying solely on the cargo hold drainage ports to drain water. The test verifies whether the drainage capacity of the drainage ports ensures safe navigation and prevents the ship from capsizing. This test is quite difficult, and failure would not only severely damage the ship model but also the test equipment, resulting in high economic losses and wasted practical costs.

[0007] Currently, relevant specifications are relatively brief and lack specific guidance, making it difficult to conduct experiments accurately.

[0008] The paper "Experimental Study on the Seakeeping Performance of a 13,000 DWT Open Multipurpose Vessel" (authors He Xinyu et al., Ship and Ocean Engineering, Vol. 33, No. 5, 2017 (Total No. 117)) discloses research on an open seakeeping model test of an open multipurpose vessel. This existing technology has the following deficiencies:

[0009] First, the prior art proposes "filling the cargo hold with water to the lower edge of the drainage port to place the ship model in a static equilibrium state. This innovatively employs an equivalent elbow." Because the distance between the top of the equivalent elbow and the lower edge of the drainage port on a real ship is greater than 1 meter, when water is poured to the lower edge of the drainage port, the water in the cargo hold does not flow out of the ship through the top of the equivalent elbow. Consequently, the amount of water flooding the open cargo hold during the test is too small, reducing the safety of the drainage port in real-world applications.

[0010] Second, the existing technology proposes "to place the ship model in a zero-speed state in beam waves and observe whether the water entering from the waves can be effectively discharged from the cargo hold drainage port to ensure that the ship model does not capsize. The cargo hold of this ship adopts an asymmetric design, and this assessment must be carried out on both port and starboard sides." The impact of wave angles of 90° and 270° on the ship's roll and wave ingress was not analyzed, and the more severe wave angle was selected for the test first. There is a possibility that the test conditions carried out randomly first are safer, while the test conditions carried out later are more dangerous and may even lead to the capsizing of the ship model, test failure, and the invalidation of all test conditions. This will result in many test conditions and long test time, reducing test efficiency and increasing test costs.

[0011] Third, the prior art states that "a certain pressure is required to open the check valve, and the check valve can only be opened when the water level in the cargo hold is about 1m higher than the check valve. An equivalent elbow is creatively used. The increase in the 1m of water inflow needs to be considered when performing stability calculations and structural strength calculations for water inflow from waves into the cargo hold." The effect of the elbow diameter d on the test results was not considered, and there is a problem that the test results are biased towards safety due to inaccurate simulation of the opening pressure of the discharge port.

[0012] The paper "Research on a Method for Evaluating Waves on Deck for Determining the Freeboard of Open Container Ships" (authors Sun Anlin et al., China Shipbuilding, Vol. 60, No. 3 (Total No. 231)) discloses a method for evaluating waves on deck for determining the freeboard of open container ships. This existing technology has the following deficiencies:

[0013] This prior art proposes "covering the remaining five open cargo holds with flexible waterproof materials to contain water accumulated due to wave ingress." During the test, there were no simulated containers in the cargo holds of the open container ship, and the test object simulation was conservative, which affected the economy of the ship.

[0014] To address the above issues, no effective solutions have been proposed so far. Summary of the Invention

[0015] In order to overcome the above-mentioned defects in the prior art, the present invention provides a method for testing the effectiveness of an open cargo hold drainage port of an open ship.

[0016] The present invention solves the above technical problems through the following technical solutions:

[0017] A method for testing the effectiveness of an open cargo hold drainage port on an open ship comprises:

[0018] Step 1: simulate the test environment conditions and test objects;

[0019] Step 2, determine the most unfavorable open cargo hold of the open container ship;

[0020] Step 3, simulating the flooding volume of the open cargo hold of an open ship;

[0021] For open container ships, the volume of the most unfavorable open cargo hold determined in step 2 below the drainage port is V 不利 , place container materials so that their volume occupies 30%V 不利 ;

[0022] For open container ships, the other open cargo holds are fully loaded with containers that are higher than the weather deck, and the volume below the cargo hold drainage port is V 其他 The volume of the cargo hold below the freeing port minus the volume of the container is V 其他浸 , the cargo hold should be flooded to a volume of 70% V 其他 The submerged volume lost due to the space occupied by the container is compensated by the ballast block;

[0023] For open-deck multipurpose ships and dry cargo ships, the volume below the drainage port of each open cargo hold is V, and cargo materials are placed so that the volume occupies 10% of V;

[0024] For ship models without cargo hold inner bottoms set at actual height, the volume of cargo hold loss is calculated. For open container ships, the cargo hold permeability is 70%, and for open-navigable multipurpose ships and dry cargo ships, the cargo hold permeability is 90%. The lost flooded volume V is calculated. 损 , use counterweights to compensate;

[0025] Step 4: Fill each open cargo hold with water until the water level covers the top of the elbow and flows out overboard;

[0026] Step 5: Conduct the effectiveness test of the open cargo hold drainage port;

[0027] For symmetrically arranged open ships, establish the freeing port effectiveness test condition D001 and conduct the test;

[0028] For asymmetrically arranged open ships, establish the drainage port effectiveness test conditions D001 and D002, analyze the effects of wave angles of 90° and 270° on ship rolling and wave flooding, and select the more severe wave angle for testing first;

[0029] Step 6: Evaluate the test results.

[0030] Furthermore, in step 1, an elbow is installed at the inlet of each cargo hold drain port to simulate the process in which the water level in the cargo hold presses open the drain port check valve and flows out of the ship; the diameter of the elbow is the same as the drain port diameter, and the height of the elbow is h+d, where h is the minimum height of the cargo hold water level that presses open the valve determined based on the opening pressure of the drain port check valve on an actual ship; and d is the drain port diameter.

[0031] Furthermore, the elbow is formed by a plurality of sleeves; the diameters of the sleeves decrease from the outside to the inside; and the diameter of the sleeve opening is larger than the diameter below the sleeve opening.

[0032] Furthermore, 1 to 2 spare drainage ports are added near each drainage port as an additional measure, and when the diameter of the drainage port needs to be adjusted, they are adjusted to an open state.

[0033] Furthermore, step 2 includes: establishing preliminary test conditions B001, where the open container ship is tested at zero speed in beam waves with a wave angle of 90° or 270°, with no containers loaded in any open cargo holds; the test time of the preliminary test conditions does not need to correspond to the actual ship time of 1 hour; measuring the amount of water entering each open cargo hold under the preliminary test conditions, and determining the most unfavorable open cargo hold.

[0034] Furthermore, in step 3, when using the ballast weight for compensation, the center of gravity of the ballast weight should correspond to the center of gravity of the water loss in the cargo hold.

[0035] Furthermore, during the experiment, the optical motion test equipment was moved out of the ship model.

[0036] Furthermore, step 4 includes: pouring water into each open cargo hold in turn until the water covers the top of the drainage port bend pipe and flows out of the drainage port; the ship model reaches a static equilibrium state, and the flooding condition C001 is established.

[0037] Furthermore, in step 6, when evaluating the test results, the setting of the open cargo hold drainage port is effective for ships that meet the following requirements: during the model test, the water level in any open cargo hold does not continue to increase and the ship does not capsize.

[0038] Furthermore, for ships that do not meet the effectiveness requirements for the setting of open cargo hold drainage ports, the following measures can be taken: enlarge the size of the drainage port or open the spare drainage port, repeat steps 4 to 6, and explain them in the test report, and make corresponding settings on the actual ship.

[0039] The beneficial effects of the present invention are as follows: the method of the present invention has a wide range of applications and can be applied to all open ships in limited and unlimited navigation areas. The method of the present invention can simulate complex wave phenomena and accurately capture dynamic changes; the method can accurately simulate the environmental conditions required by the specifications, truly construct the structural characteristics of the actual ship, scientifically and rationally design the test process, provide countermeasures, and ensure the accuracy and reliability of the test; the test method has high repeatability and high safety. The method of the present invention can reduce costs and improve efficiency; avoid overly conservative simulation of test objects and test conditions, which affects the economy of the ship. Avoid operational errors such as inaccurate simulation of the opening pressure of the drainage port and insufficient water immersion in the cargo hold, which reduce the safety of actual ship applications. The method of the present invention provides reasonable countermeasures for various special circumstances in the test to ensure the smooth completion of the test. Avoid increasing the number of tests, delaying the design and construction cycle, and other problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of the elbow according to a preferred embodiment of the present invention.

[0041] Figure 2 for Figure 1 Middle AA section view. DETAILED DESCRIPTION

[0042] A preferred embodiment is given below to more clearly and completely illustrate the present invention.

[0043] Cargo hold drain ports are openings located on both sides of the hull above the full-load waterline in the cargo hold area. These openings, fitted with stop check valves, allow water in the cargo hold to overflow through the check valves under all circumstances, while preventing seawater from entering the hold through the openings. The effectiveness model test of open cargo hold drain ports on open-deck ships verifies whether the discharge capacity of the ports is sufficient to prevent the ship from capsizing.

[0044] The present invention provides a method for testing the effectiveness of drainage ports on open cargo holds of open ships. The purpose of the present invention is to standardize model test objects and working conditions, standardize the test process, accurately verify the effectiveness of drainage ports, and ensure the safety and economy of ships.

[0045] A method for testing the effectiveness of an open cargo hold drainage port on an open ship comprises:

[0046] Step 1: simulate the test environment conditions and test objects;

[0047] Step 2, determine the most unfavorable open cargo hold of the open container ship;

[0048] Step 3, simulating the flooding volume of the open cargo hold of an open ship;

[0049] Step 4, filling each open cargo hold with water;

[0050] Step 5: Conduct the effectiveness test of the open cargo hold drainage port;

[0051] Step 6: Evaluate the test results.

[0052] Step 1 is the pre-test preparation phase, steps 2 through 5 are the test phase, and step 6 is the test result evaluation phase. The test phase should be conducted within the test environment and test subjects described in step 1. Therefore, the content described in the "pre-test preparation phase" below also reflects the conditions that must be met during the test phase.

[0053] To avoid redundancy, when quoting content from a previous document, the referenced content is replaced by the serial number of the referenced content plus quotation marks. For example, when quoting "1.3.1" from a previous document, "1.3.1" in the subsequent text refers to the content in "1.3.1" of "1. Preliminary Preparation Stage of the Test"; the specific content of "1.3.1" will not be repeated in the subsequent text.

[0054] 1. Preliminary preparation stage of the experiment

[0055] 1.1 Simulation of environmental conditions

[0056] 1.1.1 The test should be conducted in long-peaked irregular waves. The JONSWAP spectrum (Joint North Sea Wave Project, JONSWAP) may be used for the test. For ships operating only in limited sea areas, other wave spectra agreed by the Administration may be used.

[0057] 1.1.2 For ships sailing in different navigation areas, the test is to create waves with significant wave heights as specified in Table 1 under the most unfavourable wave period (crossing zero).

[0058]

[0059] 1.2 Simulation of test subjects

[0060] 1.2.1 For the test model, in addition to the requirement that the shape of the underwater part is similar to that of the actual ship, the shape of the above-water part must also be similar to that of the actual ship.

[0061] 1.2.2 The division of the model cargo hold should be consistent with that of the actual ship, and the length, width and height of each cargo hold hatch should be similar to those of the actual ship. If the inner bottom height of the model cargo hold needs to be raised, the effect of the raised inner bottom on the reduction of the flooded volume of the cargo hold must be considered.

[0062] 1.2.3 Anti-rolling measures such as bilge keels and anti-rolling tanks are to be fully considered, similar to those of actual ships.

[0063] 1.2.4 For open container ships, when individual cargo holds are provided with hatch covers, such holds may be simulated as having hatch covers during model tests, and containers may be loaded thereon without seawater entering the holds.

[0064] 1.2.5 For multi-purpose dry cargo ships and general dry cargo ships that can sail with open hatches, if the hatch covers are not opened during navigation, the cargo holds may be simulated as having hatch covers during model tests and seawater will not enter the holds.

[0065] 1.2.6 The height, number and dimensions of the freeing ports of each open cargo hold are to be similar to those of the actual ship.

[0066] 1.2.7 A hinged flap is to be installed at the outlet of each cargo hold drain port to simulate the one-way opening characteristic of the drain port.

[0067] 1.2.8 An elbow is installed at the inlet of each cargo hold drain port to simulate the process of water level in the cargo hold opening the drain port check valve and flowing outboard. The diameter of the elbow is the same as the drain port diameter, and the height of the elbow is h + d. Where h is the minimum height of the cargo hold water level that will open the valve, determined based on the actual ship's drain port check valve opening pressure; d is the drain port diameter.

[0068] The structure of the elbow is as follows Figure 1 and Figure 2 The elbow 10 is provided in the cargo hold and is connected to a drainage port 20. The drainage port 20 extends from the cargo hold longitudinal wall 21 to the hull outer plating 22.

[0069] 1.2.9 Additional measures may be provided to enable quick adjustment of the freeing port dimensions during testing, such as a multi-layer casing structure.

[0070] Bend pipe structure Figure 1 and Figure 2 As shown. The elbow is formed by a plurality of sleeves. The elbow of this embodiment is formed by a sleeve of three sleeves. The elbow includes an outermost sleeve 10, a middle sleeve 11 and an innermost sleeve 12. From the outside to the inside, the diameters of the sleeves decrease successively. The diameter of the sleeve mouth is larger than the diameter below the sleeve mouth. Of the two adjacent sleeves, the diameter of the inner sleeve mouth is larger than the diameter below the outer sleeve mouth. This structure can prevent the accumulated water in the open cargo hold from flowing out of the ship directly through the outer elbow with a larger diameter. From the inside to the outside, the heights of the three sleeves are h1+d1, h2+d2, and h3+d3, respectively.

[0071] 1.2.10 Alternatively, one or two spare freeing ports may be provided near each freeing port as an additional measure, which can be opened when the freeing port diameter needs to be adjusted.

[0072] 1.2.11 During the test, the optical motion test equipment shall be removed from the ship model to prevent damage to the equipment due to the ship model capsizing. It is not necessary to measure parameters such as ship motion, speed, and acceleration.

[0073] 1.3 Ship model loading plan and debugging method

[0074] 1.3.1 During the test, the draught of the ship model is adjusted to a position similar to the deepest draught T (minimum freeboard) of the actual ship when open to sea, and trimmed horizontally.

[0075] 1.3.2 The initial metacentric height (GM) of the ship model is the GM value corresponding to the deepest draft for open navigation on the limiting GM curve. The limiting GM curve is derived from the probabilistic damage stability calculation of the ship conducted in accordance with the International Convention for the Safety of Life at Sea.

[0076] 1.3.3 Establish the ship model loading plan A001 based on 1.3.1 and 1.3.2. Adjust the center of gravity, longitudinal moment of inertia and transverse moment of inertia of the ship model according to loading plan A001 to be similar to that of the actual ship.

[0077] 1.3.4 The ship model is subjected to a free roll attenuation test in still water at zero speed using loading scheme A001, and the ship's roll natural period, attenuation coefficient, etc. are measured.

[0078] 1.4 Test speed

[0079] 1.4.1 Zero speed (vessel without power).

[0080] 2. Experimental Phase

[0081] 2.1 Determining the most unfavorable open cargo hold for open container ships

[0082] 2.1.1 Establish preliminary test condition B001 for open container ships. Conduct the test at zero speed in beam waves with a wave angle of 90° or 270°. No containers are to be loaded in any open cargo holds. The test duration for the preliminary test condition does not need to correspond to the actual ship time of 1 hour. The preliminary test conditions are shown in Table 2.

[0083]

[0084] 2.1.2 Measure the amount of water entering each open cargo hold under the preliminary test conditions and determine the most unfavorable open cargo hold. Take a ship with three open cargo holds as an example (assuming the opening area of ​​the first cargo hold is 400m 2 、Opening area of ​​the second cargo hold hatch: 800m 2 、Opening area of ​​the third cargo hold hatch: 500m 2 See Table 3 for details.

[0085]

[0086] It can be seen from the table that the second cargo hold is the most unfavorable open cargo hold.

[0087] 2.2 Open cargo hold flooding

[0088] 2.2.1 The ship model is free and unconstrained and is secured with a hook and a soft rope (the soft rope is in a completely relaxed state) to facilitate salvage in the event of capsizing.

[0089] 2.2.2 For open container ships, the volume of the most unfavorable open cargo hold verified in "2.1" below the drainage port of the cargo hold is V 不利 , place container materials, including container simulation materials (foam, wood blocks, etc.), cable protection covers, counterweights, etc., so that the volume of container materials accounts for 30%V 不利 .

[0090] 2.2.3 For open container ships, other open cargo holds can be simulated as fully loaded with containers above the weather deck, and the volume below the cargo hold drainage port is V 其他 The volume of the cargo hold below the freeing port minus the volume of the container is V 其他浸 , the cargo hold should be flooded to a volume of 70% V 其他 , lost due to container space occupation (i.e. 70% V 其他 - V 其他浸 ) is compensated with counterweights, which are accurately placed so that their center of gravity corresponds to the center of gravity of the lost water volume.

[0091] 2.2.4 For open-deck multipurpose dry cargo ships and general dry cargo ships, the volume below the freeing port of the open cargo hold is V, where cargo materials, including cargo simulants (foam, wood, etc.), cable covers, ballast, etc., are placed so that the volume of cargo materials accounts for 10% of V.

[0092] 2.2.5 For ship models where the cargo hold inner bottom is not installed at the actual height as per 1.2.2, the effect of raising the inner bottom on the reduction in cargo hold flooding volume should be considered. Calculate the lost cargo hold volume using a 70% cargo hold permeability for open-top container ships and a 90% cargo hold permeability for open-top multipurpose dry cargo ships and general dry cargo ships. Compensate for this loss with ballast weights, which should be accurately positioned so that their centre of gravity corresponds to the centre of gravity of the lost cargo hold flooding volume.

[0093] 2.2.6 Open all cargo hold drain ports (except the spare drain port in “1.2.10”) and fill water into each open cargo hold in turn until water flows out of the drain port through the top of the bend pipe. Stop filling water.

[0094] 2.2.7 The ship model reaches static equilibrium and the submerged condition C001 is established.

[0095] 2.3 Effectiveness test of open cargo hold drainage ports

[0096] 2.3.1 For symmetrically arranged open ships, the freeing port effectiveness test condition D001 is to be established. The ship model is to be tested in beam seas at zero speed under the submerged condition C001. The test time is to be at least 1 hour corresponding to the actual ship time.

[0097] 2.3.2 For ships with asymmetrically arranged open ports, e.g., ships with only one side equipped with cranes, chimneys or other structures that may affect the entry of seawater into the cargo holds, or ships with open holds that are not arranged symmetrically in the center, the freeing port effectiveness test conditions D001 and D002 shall be established. The tests shall be carried out at zero speed in beam waves with wave angles of 90° and 270°, and the test time shall correspond to at least 1 hour of actual ship time.

[0098] The test conditions for the effectiveness of open cargo hold drainage ports are shown in Table 4.

[0099]

[0100] 2.3.3 For open ships with asymmetrical layout, the effects of wave direction angles of 90° and 270° on ship rolling and water ingress are to be analyzed based on the buoyancy of the ship model in flooding condition C001. The more severe wave direction angle is to be selected for testing first.

[0101] 3 Evaluation of test results

[0102] 3.1 Effectiveness evaluation of open cargo hold drainage ports on open ships

[0103] 3.1.1 The provision of open cargo hold freeing ports is effective for ships that meet the following requirements:

[0104] During the model test, the water level in any open cargo hold did not continue to increase and the ship did not capsize.

[0105] 3.1.2 For ships that do not meet the requirements of "3.1.1", the following measures may be taken:

[0106] Enlarge the size of the freeing port, or open the spare freeing port, repeat the effectiveness test of the open cargo hold freeing port, explain it in the test report, and set it accordingly on the actual ship.

[0107] The present invention can standardize model test objects and working conditions, regulate the test process, accurately verify the effectiveness of the drainage port, and ensure the safety and economy of the ship.

[0108] This invention innovatively constructs a model test method for the effectiveness of open cargo hold drainage ports on open ships, filling the gaps in details and depth in existing specifications, providing a more comprehensive implementation basis and guiding principles, and providing an indispensable key reference for ship design and navigation safety.

[0109] The beneficial effects of the present invention are:

[0110] The key factors affecting the results of the freeing port effectiveness test are: open cargo hold cargo simulation method, open cargo hold cargo flooding volume simulation method, open cargo hold flooding water level determination method, freeing port simulation method, and effectiveness test conditions sequence selection method.

[0111] 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 (Total No. 231)) proposed that "the remaining five open cargo holds are covered with flexible waterproof materials to collect water caused by the incoming waves." The present invention adopts "the most unfavorable open cargo hold in beam waves is obtained through preliminary tests, and the container materials are placed in the most unfavorable open cargo hold so that its volume accounts for 30% of V 不利 The method for arranging containers in open cargo holds fully loaded with containers that are higher than the weather deck fully considers the loading requirements of actual ship operations, overcomes the problem of conservative test object simulation in the existing technology, and improves the economic efficiency of the ship.

[0112] The present invention innovatively proposes a method for simulating the flooded volume of open cargo holds of open-top container ships, a method for simulating the flooded volume of open cargo holds of open-top navigable multipurpose ships and dry cargo ships, and a method for simulating the flooded volume of open cargo holds where the inner bottom of the cargo hold is not set according to the actual height. The present invention provides guidance for effectiveness testing of freeing ports on all open-top ships in all navigation areas, overcomes the problem of invalid experimental results due to errors in simulating the flooded volume of open cargo holds, and ensures the safety of freeing ports in actual ship applications.

[0113] The paper "Experimental Study on the Seakeeping of a 13,000 DWT Open Multipurpose Vessel" (authors He Xinyu et al., Ship and Ocean Engineering, Vol. 33, No. 5, 2017 (Total No. 117)) proposes "filling the cargo hold with water to the lower edge of the drainage port to place the ship model in a static equilibrium state. This innovative approach utilizes an equivalent elbow pipe. This invention employs the technical feature of "sequentially filling each open cargo hold with water until the water level exceeds the top of the elbow pipe and flows outboard, at which point water filling is stopped." This approach fully accounts for the fact that the distance between the top of the elbow pipe and the lower edge of the drainage port on a real ship is greater than 1 meter. This overcomes the existing problem of smaller flooded open cargo holds, which results in less reliable experimental results, thereby ensuring test accuracy.

[0114] The above-mentioned paper proposes that "a certain pressure is required to open the check valve, and the check valve can only be opened when the water level in the cargo hold is about 1m higher than the check valve. An equivalent elbow is creatively used. The increase of the water inflow of 1m needs to be considered when performing stability calculations and structural strength calculations for water inflow from waves into the cargo hold." The present invention adopts "the elbow height is h+d, where h is the minimum height of the valve opened by the water level in the cargo hold; d is the diameter of the drainage port." The influence of the elbow diameter d on the test results is taken into account, overcoming the problem in the existing technology of inaccurate simulation of the drainage port opening pressure, resulting in a safe test result, and ensuring the accuracy of the test.

[0115] In addition, the present invention adopts the technical features of "multi-layer casing structure, spare drainage port and other additional measures for quickly adjusting the drainage port size", which greatly shortens the time for test personnel to adjust the drainage port size and improves test efficiency.

[0116] The above-mentioned paper proposes that "the ship model is in a zero-speed state in beam waves, and the water entering from the waves is observed to be able to be effectively discharged from the cargo hold drainage port to ensure that the ship model does not capsize. The cargo hold of this ship adopts an asymmetric design, and this assessment must be carried out on both port and starboard sides." The present invention adopts the technical feature of "analyzing the impact of wave angles of 90° and 270° on the ship's roll and wave inflow, and selecting the more severe wave angle for the first test." This overcomes the situation in the prior art where the test conditions carried out randomly first are safer, while the test conditions carried out later are more dangerous and may even lead to the capsizing of the ship model, test failure, and the invalidation of all test conditions, thereby improving test efficiency and reducing test costs.

[0117] The present invention has the following advantages:

[0118] (1) The method of the present invention has a wide range of applications and can be applied to all open ships in limited and unlimited navigation areas;

[0119] (2) The method of the present invention can simulate complex wave phenomena and accurately capture dynamic changes;

[0120] (3) The method of the present invention accurately simulates the environmental conditions required by the specifications, realistically constructs the structural characteristics of the actual ship, scientifically and rationally designs the test process, and provides countermeasures to ensure the accuracy and reliability of the test.

[0121] (4) The test method is highly repeatable and safe.

[0122] (5) The test method can reduce costs and improve efficiency; avoid overly conservative simulation of test objects and test conditions, which may affect the economic efficiency of the ship. Avoid operational errors such as failure to simulate the opening pressure of the drainage port and insufficient flooding of the cargo hold, which may reduce the safety of actual ship application.

[0123] (6) Provide reasonable response measures for special circumstances during the test to ensure the smooth completion of the test. Avoid increasing the number of tests and delaying the design and construction cycle.

[0124] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A method for testing the effectiveness of open cargo hold drainage ports on open ships, characterized in that: It includes: Step 1: Simulate the test environment conditions and test objects, including the ship model loading plan A001; According to the loading scheme A001, the center of gravity, longitudinal moment of inertia and transverse moment of inertia of the ship model are debugged to be similar to those of the actual ship; Loading plan A001 includes: During the test, the draft of the ship model is adjusted to a position similar to the deepest draft T of the actual ship in open sailing, and the ship model is trimmed horizontally; the initial metacentric height GM of the ship model is the GM value corresponding to the deepest draft in open sailing on the limit GM curve; Step 2, determine the most unfavorable open cargo hold of the open container ship; Step 3, simulating the flooding volume of the open cargo hold of an open ship; For open container ships, the volume of the most unfavorable open cargo hold determined in step 2 below the drainage port is V 不利 , place container materials so that their volume occupies 30% of V 不利 ; For open container ships, the other open cargo holds are fully loaded with containers that are higher than the weather deck, and the volume below the cargo hold drainage port is V 其他 The volume of the cargo hold below the freeing port minus the volume of the container is V 其他浸 , the cargo hold should be flooded with 70% of its volume V 其他 The submerged volume lost due to the space occupied by the container is compensated by the ballast block; For open-deck multipurpose ships and dry cargo ships, the volume below the freeing port of each open cargo hold is V, and cargo materials are placed so that their volume occupies 10% of V; For ship models without cargo hold inner bottoms set at actual height, the volume of cargo hold loss is calculated. For open container ships, the cargo hold permeability is 70%, and for open-navigable multipurpose ships and dry cargo ships, the cargo hold permeability is 90%. The lost flooded volume V is calculated. 损 , use counterweights to compensate; Step 4: Fill each open cargo hold with water in turn until the water covers the top of the drainage port elbow and flows out of the drainage port; the ship model reaches a static equilibrium state, and the flooding condition C001 is established; Step 5: Conduct the effectiveness test of the open cargo hold drainage port; For symmetrically arranged open ships, the freeing port effectiveness test condition D001 is established, and the ship model is tested in the submerged condition C001 at zero speed in beam waves; For asymmetrically arranged open ships, the effectiveness test conditions for the freeing ports are established, D001 and D002. Tests are conducted at zero speed in beam waves with wave angles of 90° and 270°. Based on the buoyancy of the ship model in the flooding condition C001, the effects of wave angles of 90° and 270° on the ship's rolling and water ingress are analyzed, with the more severe wave angle being selected for testing first. Among them, test conditions D001 and D002 represent the working conditions: the wave angles are 90° and 270° respectively, the still water speed is 0 kn, and the loading scheme is A001; Step 6: Evaluate the test results.

2. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 1, characterized in that: In step 1, an elbow is installed at the inlet of each cargo hold drain port to simulate the process in which the water level in the cargo hold presses open the drain port check valve and flows out of the ship; the diameter of the elbow is the same as the drain port diameter, and the height of the elbow is h+d, where h is the minimum height of the cargo hold water level that presses open the valve determined based on the opening pressure of the drain port check valve on an actual ship; and d is the drain port diameter.

3. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 2, characterized in that: The elbow is formed by a plurality of sleeves; the diameters of the sleeves decrease from the outside to the inside; and the diameter of the sleeve opening is larger than the diameter below the sleeve opening.

4. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 2, characterized in that: As an additional measure, 1 to 2 spare drainage ports are added near each drainage port. When the drainage port diameter needs to be adjusted, they can be adjusted to the open state.

5. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 1, characterized in that: Step 2 includes: establishing preliminary test condition B001, where the open container ship is tested at zero speed in beam waves with a wave angle of 90° or 270°, with no containers loaded in any open cargo holds; the test time of the preliminary test condition does not need to correspond to the actual ship time of 1 hour; measuring the amount of water entering each open cargo hold under the preliminary test condition and determining the most unfavorable open cargo hold.

6. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 1, characterized in that: In step 3, when using ballast weights for compensation, the center of gravity of the ballast weights should correspond to the center of gravity of the water loss in the cargo hold.

7. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 1, characterized in that: During the test, the optical motion test equipment was removed from the ship model.

8. The method for testing the effectiveness of open cargo hold drainage ports of open ships according to claim 1, characterized in that: In step 6, when evaluating the test results, the provision of open cargo hold drainage ports is considered effective for ships that meet the following requirements: during the model test, the water level in any open cargo hold does not continue to increase and the ship does not capsize.

9. The method for testing the effectiveness of open cargo hold drainage ports of an open ship according to claim 8, characterized in that: For ships that do not meet the effectiveness requirements for the setting of open cargo hold drainage ports, the following measures can be taken: enlarge the size of the drainage port or open the spare drainage port, repeat steps 4 to 6, and explain them in the test report, and make corresponding settings on the actual ship.

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