Control program for air lubrication system that takes into account the surface roughness of the ship's bottom, air lubrication system, and air lubrication system

Abstract

The present invention provides a control program for an air lubrication device, an air lubrication device, and an air lubrication system that can effectively mitigate or prevent the increase in hull frictional resistance associated with an increase in surface roughness through air lubrication. [Solution] The control program for an air lubrication system that takes into account the surface roughness of the ship's bottom is a program that controls an air lubrication system that reduces frictional resistance by flowing air under the ship's bottom, and causes the computer 10 to execute a condition acquisition step S1 to acquire input conditions necessary to determine the amount of blown air (Q) to be blown under the ship's bottom, a ship speed acquisition step S2 to acquire information on the ship's speed (V), a surface roughness calculation step S4 to calculate the surface roughness (ks) of the ship's bottom, and an air amount determination step S6 to determine the amount of blown air (Q) to be blown under the ship's bottom based on the relationship between the ship's speed (V) acquired in the ship speed acquisition step S2, the surface roughness (ks) calculated in the surface roughness calculation step, and the air thickness of the air covering the surface of the ship's bottom.

Description

[Technical Field]

[0001] The present invention relates to a program, apparatus, and system for controlling an air lubrication device that reduces the frictional resistance of a ship's hull by blowing air onto the bottom of the ship. [Background technology]

[0002] Air lubrication methods that reduce frictional resistance by covering the bottom of a ship with a flow of bubbles are known, and air lubrication devices using this technology are gradually becoming popular as energy-saving devices. For example, Patent Document 1 discloses a bubble control unit that controls a bubble ejection mechanism that ejects bubbles from an air outlet provided on the ship's hull, and the bubble control unit starts ejecting bubbles or increases the amount of bubbles ejected when the hull resistance of the ship meets preset conditions. Furthermore, it is known that ships become fouled during actual operation due to factors such as biological fouling, and the roughness of the hull surface increases. Non-patent document 1 discusses the validity verification of an approximate estimation method for propulsion performance in actual sea conditions, including fouling and the effects of aging. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-13216 [Non-patent literature]

[0004] [Non-Patent Document 1] Masashi Miyamoto, "Estimation and Evaluation of Propulsion Performance in Actual Sea Conditions," Transactions of the Japan Society of Naval Architects and Ocean Engineers, No. 6, pp. 205-214, December 2007. [Overview of the project] [Problems that the invention aims to solve]

[0005] While ships show little hull fouling in the early stages of operation or after cleaning, the submerged parts of the hull gradually become fouled due to factors such as biological fouling during actual operation, and the roughness of the hull surface increases. This increased roughness of the hull surface raises concerns that it will increase hull friction resistance, diminishing the effectiveness of air lubrication. Patent Document 1, mentioned above, states that when calculating the actual hull resistance, which is the criterion for determining when bubbles start to be ejected or when the amount of bubbles to be ejected increases, information regarding hull fouling, such as barnacle attachment, may be taken into consideration (paragraph 0056). However, it is unclear how the amount of air ejected is determined by taking into account information regarding hull fouling. Therefore, the present invention aims to provide a control program for an air lubrication device, an air lubrication device, and an air lubrication system that can effectively mitigate or prevent the increase in hull frictional resistance associated with an increase in surface roughness through air lubrication. [Means for solving the problem]

[0006] A control program for an air lubrication system that takes into account the surface roughness of the ship's bottom, corresponding to claim 1, is a program for controlling an air lubrication system that reduces frictional resistance by flowing air over the bottom of a ship, characterized in that it causes a computer to execute a condition acquisition step to acquire input conditions necessary for determining the amount of blown air (Q) to be blown onto the ship's bottom, a ship speed acquisition step to acquire information on the ship's speed (V), a surface roughness calculation step to calculate the surface roughness (ks) of the ship's bottom, and an air amount determination step to determine the amount of blown air (Q) to be blown onto the ship's bottom based on the relationship between the ship's speed (V) acquired in the ship speed acquisition step, the surface roughness (ks) calculated in the surface roughness calculation step, and the air film thickness covering the surface of the ship's bottom. According to the present invention as described in claim 1, the amount of air blown out by the air lubrication device is appropriately determined according to the degree of surface roughness. Therefore, even when the surface roughness is high due to hull fouling, the effect of reducing hull friction resistance by air lubrication can be exerted in the same manner as when the surface roughness is low.

[0007] The present invention as described in claim 2 is characterized in that, in the step of determining the amount of air, the air thickness is set to the equivalent air thickness (tb), and the amount of blown air (Q) is determined using formulas (1) and (2). According to the present invention as described in claim 2, the amount of discharged air can be more appropriately determined using formulas (1) and (2) relating to the equivalent air film thickness.

[0008] The present invention as described in claim 3 is characterized in that, in the surface roughness calculation step, the surface roughness (ks) is calculated using formulas (3) and (4). According to the present invention as described in claim 3, the surface roughness required when determining the amount of blown air can be accurately calculated by formula (3), which determines the roughness correction coefficient from actual ship monitoring data, and formula (4), which uses the draft length in a planned fully loaded state.

[0009] The present invention as described in claim 4 is characterized in that, in the surface roughness calculation step, the surface roughness (ks) is calculated using formulas (3) and (5). According to the present invention as described in claim 4, the surface roughness necessary for determining the amount of blown air can be accurately calculated using formula (3), which determines the roughness correction coefficient from actual ship monitoring data, and formula (5), which is considered a representative calculation formula for the roughness correction coefficient at the ITTC (International Test Tank Conference).

[0010] The present invention as described in claim 5 is characterized in that, in the surface roughness calculation step, the surface roughness (ks) is calculated using formulas (3) and (6). According to the present invention as described in claim 5, the surface roughness necessary for determining the amount of blown air can be accurately calculated using formula (3), which determines the roughness correction coefficient from actual ship monitoring data, and formula (6), which is considered a typical calculation formula for the roughness correction coefficient at SRC (Japan Shipbuilding Technology Center).

[0011] The present invention as described in claim 6 is characterized in that, in the surface roughness calculation step, the surface roughness (ks) is calculated using formula (7). According to the present invention described in claim 6, the surface roughness required when determining the blown air volume can be accurately calculated in consideration of the number of years elapsed since completion and the number of years elapsed since the last docking.

[0012] In an air lubrication device that takes into account the surface roughness of the ship bottom corresponding to claim 7, it is an air lubrication device that reduces frictional resistance by blowing air onto the ship bottom, and includes a computer, a condition input means for inputting the conditions necessary for determining the blown air volume (Q) blown onto the ship bottom, a navigation state acquisition means for acquiring the navigation state including the ship speed (V) of the ship, and an output means. The computer is caused to execute a control program for the air lubrication device considering the surface roughness of the ship bottom, and at least the determined blown air volume (Q) is output from the output means for controlling the air supply control device. According to the present invention described in claim 7, since the blown air volume of the air lubrication device is appropriately determined according to the degree of surface roughness, even when the surface roughness becomes high due to fouling of the ship bottom, the effect of reducing the hull frictional resistance by air lubrication can be exerted equivalently to the case where the surface roughness is low.

[0013] The present invention described in claim 8 is configured to cause a computer to execute a control program for an air lubrication device that takes into account the surface roughness of the ship bottom described in claim 2, and a condition acquisition unit of the computer acquires at least one of the equivalent air film thickness (tb) and the air coverage width (Bt). According to the present invention described in claim 8, when calculating the blown air volume using equations (1) and (2) related to the equivalent air film thickness, at least one of the equivalent air film thickness or the air coverage width can use the value acquired by the condition acquisition unit, so the labor of calculating the acquired value separately can be saved.

[0014] The present invention described in claim 9 is configured to cause a computer to execute a control program for an air lubrication device that takes into account the surface roughness of the ship bottom described in claim 3. The navigation state acquisition means acquires at least one of the propeller rotation speed (n) and the propeller torque (QB), and the condition acquisition unit calculates the quasi-propulsion efficiency (ηD ) the density of seawater (ρ), the wetted surface area (S), the wave-making resistance coefficient (C W ), the shape coefficient (k), the frictional resistance coefficient (CF), the resistance coefficient (C AD ) increased by waves and wind, and at least one of the waterline length (L) in the planned fully loaded condition, characterized by obtaining According to the present invention described in claim 9, when calculating the surface roughness based on formula (3) and formula (4), at least one of the propeller rotation speed or the propeller torque, and the quasi-propulsion efficiency, the density of seawater, the wetted surface area, the wave-making resistance coefficient, the shape coefficient, the frictional resistance coefficient, the resistance coefficient increased by waves and wind, or at least one of the waterline length in the planned fully loaded condition can use the value obtained by the navigation state acquisition means or the condition acquisition unit. Therefore, for the obtained value, the labor of calculating by separate calculation can be saved. Note that the density of seawater (ρ) can be read as the density of water (ρ) when the air lubrication device is applied to fresh water.

[0015] The present invention described in claim 10 is configured to cause a computer to execute a control program of an air lubrication device considering the surface roughness of the ship bottom described in claim 4. The navigation state acquisition means acquires at least one of the propeller rotation speed (n) and the propeller torque (QB), and the condition acquisition unit acquires the quasi-propulsion efficiency (η D ), the density of seawater (ρ), the wetted surface area (S), the wave-making resistance coefficient (C W ), the shape coefficient (k), the frictional resistance coefficient (C F ), the resistance coefficient (C AD ) increased by waves and wind, the waterline length (L) in the planned fully loaded condition, and at least one of the Reynolds number (Re), characterized by obtaining According to the present invention described in claim 10, when calculating the surface roughness based on formula (3) and formula (5), at least one of the propeller rotation speed or the propeller torque, and at least one of the quasi-propulsion efficiency, the density of seawater, the wetted surface area, the wave-making resistance coefficient, the shape coefficient, the frictional resistance coefficient, the resistance coefficient increased by waves and wind, the waterline length in the planned fully loaded state, or the Reynolds number can use the value obtained by the navigation state acquisition means or the condition acquisition unit. Therefore, for the obtained value, the labor of calculating by separate calculation can be saved.

[0016] The present invention described in claim 11 is configured to cause a computer to execute a control program of an air lubrication device considering the surface roughness of the ship bottom described in claim 5. The navigation state acquisition means acquires at least one of the propeller rotation speed (n) and the propeller torque (QB), and the condition acquisition unit acquires the quasi-propulsion efficiency (η D ), the density of seawater (ρ), the wetted surface area (S), the wave-making resistance coefficient (C W ), the shape coefficient (k), the frictional resistance coefficient (C F ), the resistance coefficient increased by waves and wind (C AD ), at least one of the waterline length (L) in the planned fully loaded state, the molded width (B), the draft (d) at the center of the hull in the loaded state, and the Reynolds number (Re). According to the present invention described in claim 11, when calculating the surface roughness based on formula (3) and formula (6), at least one of the propeller rotation speed or the propeller torque, and at least one of the quasi-propulsion efficiency, the density of seawater, the wetted surface area, the wave-making resistance coefficient, the shape coefficient, the frictional resistance coefficient, the resistance coefficient increased by waves and wind, the waterline length in the planned fully loaded state, the molded width, the draft at the center of the hull in the loaded state, or the Reynolds number can use the value obtained by the navigation state acquisition means or the condition acquisition unit. Therefore, for the obtained value, the labor of calculating by separate calculation can be saved.

[0017] The present invention described in claim 12 is configured to cause a computer to execute a control program of an air lubrication device considering the surface roughness of the ship bottom described in claim 6. The condition acquisition unit acquires at least one of the number of years (Yb) since completion and the number of years (Yd) since the previous docking as needed. According to the present invention as described in claim 12, the number of years since completion or the number of years since the last docking, which is necessary when calculating the surface roughness based on formula (7), can be obtained through the condition acquisition unit.

[0018] An air lubrication system that takes into account the surface roughness of the ship's bottom, corresponding to claim 13, is an air lubrication system that reduces frictional resistance by blowing air onto the bottom of a ship, and is equipped on the ship with a computer, navigation status acquisition means, condition input means and output means for the air lubrication device that takes into account the surface roughness of the ship's bottom, as described in claim 7, and is equipped with monitoring means at a remote location away from the ship, and the computer and monitoring means are connected via an information and communication network, and the monitoring means can receive condition inputs from other condition input means and signals from the output means at the remote location. According to the present invention as described in claim 13, it is possible to transmit the conditions necessary to determine the amount of air to be blown out to the bottom of the ship to a computer on board the ship from a location away from the ship (for example, on land), and to receive and confirm the amount of air to be blown out calculated by the computer on board the ship. [Effects of the Invention]

[0019] According to the present invention, the increase in hull frictional resistance associated with an increase in surface roughness can be effectively mitigated or prevented by air lubrication. [Brief explanation of the drawing]

[0020] [Figure 1] This figure shows the flow of the control program for an air lubrication device according to an embodiment of the present invention. [Figure 2] Schematic diagram of the air lubrication system. [Figure 3] A diagram showing a ship equipped with the same air lubrication system. [Figure 4] This figure shows the relationship between the total drag coefficient and tb / V of a long, flat-plate model ship in a tank test. [Figure 5] This figure shows the relationship between the difference in total resistance coefficients between each rough surface and a smooth surface and tb / V, using the same approximation formula. [Figure 6] This figure shows the relationship between tb / V, where the total resistance coefficient is 0, and surface roughness for each rough surface. [Figure 7] Schematic diagram of an air lubrication system according to an embodiment of the present invention. [Figure 8] Bottom view of a long, flat-plate model ship in a tank test. [Figure 9] Diagram showing the shape of each roughness level. [Figure 10] A diagram showing the distribution of roughness in a flat plate of the same roughness. [Figure 11] This figure shows the results of a resistance test of a long, flat-plate model ship under the same conditions without air lubrication. [Figure 12] This figure shows the results of a resistance test of a long, flat-plate model ship at a towing speed of 5.0 m / s under the same air-lubricated conditions. [Figure 13] This figure shows the results of a resistance test of a long, flat-plate model ship at a towing speed of 6.0 m / s under the same air-lubricated conditions. [Figure 14] This figure shows the relationship between the amount of blown air and the drag reduction rate at a towing speed of 5.0 m / s. [Figure 15] This figure shows the relationship between the amount of blown air and the drag reduction rate at a towing speed of 6.0 m / s. [Modes for carrying out the invention]

[0021] This document describes a control program for an air lubrication device that takes into account the surface roughness of the ship's bottom, an air lubrication device, and an air lubrication system according to the present invention. Figure 1 shows the flow of the control program for the air lubrication system, Figure 2 is a schematic diagram of the air lubrication system's configuration, and Figure 3 shows a ship equipped with the air lubrication system. Ship 1 is equipped with an air lubrication system that reduces hull friction resistance by flowing air near the surface of the bottom of the hull. As shown in Figure 3, the air lubrication system comprises a chamber 2 located at the bottom of the hull near the bow, an air supply means 3 such as a blower that supplies air into the chamber 2, and an air supply control device 4 that controls the air supply means 3. An air outlet 2A is opened at the bottom of the chamber 2, and the air inside the chamber 2 is blown out into the water from the air outlet 2A, forming bubbles that flow towards the stern. The bottom surface of the hull is covered by the resulting bubble flow, reducing the hull friction resistance of Ship 1.

[0022] As shown in Figure 2, the control device for the air lubrication system includes a computer 10 that determines the amount of blown air, a condition input means 20 such as a mouse or keyboard used to input conditions to the computer 10 from the outside, a navigation state acquisition means 30 such as various sensors or information processing devices that acquire the navigation state of the vessel, and an output means 40 that outputs the determined amount of blown air to the air supply control device 4. The condition input means 20, the navigation state acquisition means 30, and the output means 40 are connected to the computer 10.

[0023] The computer 10 includes a condition acquisition unit 101, a ship speed acquisition unit 102, a preliminary calculation unit 103, a surface roughness calculation unit 104, a blown air calculation unit 105, a blown air determination unit 106, an output unit 107, a first storage unit 108, a second storage unit 109, a control unit 110, and an information provision unit 111. The condition acquisition unit 101 acquires the conditions entered by the condition input means 20. The ship speed acquisition unit 102 acquires the ship speed from the data related to the navigation state acquired by the navigation state acquisition means 30. The preliminary calculation unit 103 calculates the conditions necessary to determine the amount of blown air to be released into the bottom of the ship that have not been acquired by the condition acquisition unit 101. The first memory unit 108 or the second memory unit 109 stores data transmitted to the computer 10 from the condition input means 20 or the navigation status acquisition means 30. The control unit 110 controls the operation of each part, such as the condition acquisition unit 101 and the ship speed acquisition unit 102, as well as the overall control of the computer 10.

[0024] Computer 10 has a control program for the air lubrication system (hereinafter referred to as the "control program") installed that takes into account the surface roughness of the ship's bottom. The control program can be stored on a storage medium (storage device) that computer 10 can read, such as a DVD-ROM. The control program may also be stored and used in the first storage unit 108 or the second storage unit 109. Furthermore, the functions of computer 10 can be used in any combination other than the configuration shown in Figure 2. The computer 10 receives data related to the conditions necessary to determine the amount of air to be blown out to the bottom of the hull, either manually or automatically, via the condition input means 20. The conditions necessary to determine the amount of air to be blown out include, for example, the equivalent air thickness, air coverage width, quasi-propulsion efficiency, seawater density, flooded surface area, wave resistance coefficient, shape coefficient, friction resistance coefficient, resistance coefficient increased by waves and wind, the planned full-load waterline length, Reynolds number, mold width, draft at the midship section of the hull in a cargo-loaded state, the number of years since completion, and the number of years since the last docking. These are input in accordance with the calculation formulas used in the preliminary calculation step S3, the surface roughness calculation step S4, and the air to be blown out calculation step S5, which are described later. In addition, the calculation formulas used in the preliminary calculation step S3 and the surface roughness calculation step S4 can also be input via the condition input means 20. The computer 10 receives information regarding the navigation status acquired by the navigation status acquisition means 30, either manually or automatically. This navigation status information includes, for example, ship speed, propeller rotation speed, propeller torque, and wave and wind conditions (wave height, wave direction, wind speed, wind direction, etc.).

[0025] The computer 10 uses the data acquired via the condition input means 20 and the data acquired via the navigation state acquisition means 30 to determine the amount of air to be blown into the water from the air outlet 2A in the following procedure, and outputs the determined amount of blown air to the air supply control device 4. The air supply control device 4 controls the operation of the air supply means 3 so that the airflow rate corresponds to the amount of blown air received from the computer 10.

[0026] The procedure for determining the amount of air to be discharged is as follows: {Step S1: Condition Acquisition Step} The condition acquisition unit 101 acquires (extracts) data used for calculating the amount of blown air from the data input via the condition input means 20 and recorded in the first storage unit 108 or the second storage unit 109. It is preferable that the condition acquisition unit 101 acquires at least one of the equivalent air film thickness and the air covering width. This allows the value acquired by the condition acquisition unit 101 to be used for at least one of the equivalent air film thickness or air covering width when calculating the amount of blown air using equations (1) and (2) for the equivalent air film thickness in the blown air amount calculation step S5 described later, thus saving the trouble of separately calculating the acquired value in the preliminary calculation step S3 described later.

[0027] {Step S2: Obtain ship speed} The ship speed acquisition unit 102 acquires (extracts) data used to calculate the amount of blown air, in addition to the ship speed, from the data input from the navigation state acquisition means 30 and recorded in the first storage unit 108 or the second storage unit 109.

[0028] {Step S3: Preliminary calculation step} The preliminary calculation unit 103 calculates data used to calculate the amount of blown air that has not been acquired in the condition acquisition step S1 or the ship speed acquisition step S2. For example, if the Reynolds number or the drag coefficient is not stored in the first storage unit 108 and the second storage unit 109, the preliminary calculation unit 103 calculates those values.

[0029] {Step S4: Surface Roughness Calculation Step} The surface roughness calculation unit 104 calculates the surface roughness of the ship's bottom. The surface roughness (roughness height) can be calculated using the monitoring results of the ship's speed and horsepower. Equation (3) below is the roughness correction coefficient ΔC F This formula is derived from actual ship monitoring data.

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[0030] The roughness correction coefficient ΔC calculated using equation (3) F The corresponding surface roughness ks can be determined using the following equations: (4), (5), or (6). Equation (4) uses the draft length in a planned full-load state, equation (5) is considered a representative formula for calculating the roughness correction factor at the ITTC (International Test Tank Conference), and equation (6) is considered a representative formula for calculating the roughness correction factor at the SRC (Japan Shipbuilding Technology Center).

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[0031] When determining surface roughness using equations (3) and (4), it is preferable to obtain at least one of the propeller rotation speed and propeller torque along with the ship speed using the navigation condition acquisition means 30, and to obtain at least one of the following using the condition acquisition unit 101: quasi-propulsion efficiency, seawater density, submerged surface area, wave resistance coefficient, shape coefficient, friction resistance coefficient, resistance coefficient increased by waves and wind, and the draft length in the planned fully loaded state. As a result, when calculating the surface roughness based on equations (3) and (4), at least one of the propeller rotation speed or propeller torque, and at least one of the quasi-propulsion efficiency, seawater density, submerged surface area, wave resistance coefficient, shape coefficient, friction resistance coefficient, resistance coefficient increased by waves and wind, or the waterline length in the planned fully loaded state can be values ​​obtained by the navigation condition acquisition means or condition acquisition unit 101. Therefore, the acquired values ​​do not need to be calculated separately in the preliminary calculation step S3.

[0032] When determining surface roughness using equations (3) and (5), it is preferable to obtain at least one of the propeller rotation speed and propeller torque along with the ship speed using the navigation condition acquisition means 30, and to obtain at least one of the quasi-propulsion efficiency, seawater density, submerged surface area, wave resistance coefficient, shape coefficient, friction resistance coefficient, resistance coefficient increased by waves and wind, draft length in the planned full load state, and Reynolds number using the condition acquisition unit 101. As a result, when calculating the surface roughness based on equations (3) and (5), at least one of the propeller rotation speed or propeller torque, and at least one of the quasi-propulsion efficiency, seawater density, submerged surface area, wave resistance coefficient, shape factor, friction resistance coefficient, resistance coefficient increased by waves and wind, planned full-load draft length, or Reynolds number can be values ​​obtained by the navigation condition acquisition means or condition acquisition unit 101. Therefore, the acquired values ​​do not need to be calculated separately in the preliminary calculation step S3.

[0033] When determining surface roughness using equations (4) and (6), it is preferable to obtain at least one of the propeller rotation speed and propeller torque along with the ship speed using the navigation condition acquisition means 30, and to obtain at least one of the following using the condition acquisition unit 101: quasi-propulsion efficiency, seawater density, submerged surface area, wave resistance coefficient, shape coefficient, friction resistance coefficient, resistance coefficient increased by waves and wind, waterline length in the planned fully loaded state, mold width, draft of the central part of the hull in the cargo-loaded state, and Reynolds number. As a result, when calculating surface roughness based on equations (3) and (6), at least one of the propeller rotation speed or propeller torque, and at least one of the following can be used: quasi-propulsion efficiency, density of seawater, submerged surface area, wave resistance coefficient, shape coefficient, friction resistance coefficient, resistance coefficient increased by waves and wind, planned full-load draft length, mold width, draft of the midship section of the hull in a cargo-loaded state, or Reynolds number. Therefore, the acquired values ​​do not need to be calculated separately in the preliminary calculation step S3.

[0034] In any of the formulas (3) to (6) used, any data necessary for calculating surface roughness that cannot be obtained via the condition input means 20 or the navigation state acquisition means 30 is calculated by the preliminary calculation unit 103.

[0035] Furthermore, the surface roughness calculation unit 104 can also calculate the surface roughness ks due to hull fouling using the following formula (7).

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[0036] {Step S5: Airflow Volume Calculation Step} The discharge air calculation unit 105 calculates the amount of discharge air to be blown onto the bottom of the ship based on the relationship between the ship speed acquired by the ship speed acquisition unit 102, the surface roughness calculated by the surface roughness calculation unit 104, and the air thickness of the air covering the surface of the ship's bottom. The air film thickness should preferably be equivalent air film thickness. Equivalent air film thickness is the thickness of the air film assuming that all the air blown out onto the bottom of the ship becomes an air film (bubbles) and flows away towards the stern at the same speed as the ship while remaining in that air film state. When using equivalent air film thickness, the blown air calculation unit 105 determines the equivalent air film thickness tb [mm] for which the resistance during air lubrication is approximately the same for both smooth and rough surfaces, based on the ship speed and surface roughness, using the following formula (1). Then, the blown air volume Q [l / s] is calculated from the determined air film thickness using the following formula (2). This allows for accurate calculation of the blown air volume.

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[0037] The above equation (1) was obtained through a tank test using the long, flat-plate model ship 6 described later. Figure 4 shows the relationship between the total drag coefficient Ct and tb / V of a long, flat-plate model ship. Figure 5 shows the relationship between the difference in total drag coefficients dCt between each roughened surface and a smooth surface and tb / V, obtained by linear approximation from the test results shown in Figure 4. Figure 6 shows the relationship between tb / V and surface roughness ks, determined from the relationship between the difference in total drag coefficients and tb / V for each roughened surface, where the total drag coefficient becomes 0. From the relationship shown in Figure 6, the tb / V at which the increase in resistance compared to a smooth surface is zero can be calculated for each rough surface. Since V is the ship speed, the amount of air that can eliminate the increase in resistance due to roughness is determined by equation (1).

[0038] {Step S6: Air volume determination step} The discharge air determination unit 106 determines the amount of air calculated by the discharge air calculation unit 105 as the amount of air to be discharged onto the bottom of the ship. The amount of air calculated by the discharge air calculation unit 105 is the minimum amount of air required to achieve frictional resistance equivalent to that of a smooth surface, assuming no fouling of the ship's bottom due to biological attachment or an increase in surface roughness due to aging. Therefore, by determining a larger amount of air as the discharge air amount in the discharge air determination unit 106, a more reliable reduction in frictional resistance can be achieved. The amount of air to be discharged, determined by the air discharge determination unit 106, is transmitted from the output unit 107 to the output means 40. The output means 40 outputs the received amount of air to the air supply control device 4, and the air supply control device 4 controls the operation of the air supply means 3 so that the airflow rate corresponds to the amount of air discharged. Furthermore, information regarding the equivalent air film thickness, ship speed, etc., stored in the first memory unit 108 or the second memory unit 109 can be transmitted from the information provision unit 111 to the output means 40, and output from the output means 40 to an external computer or the like.

[0039] As described above, the control program of the present invention determines the amount of air blown onto the bottom of the ship based on the relationship between ship speed, surface roughness, and air film thickness. This ensures that the amount of air blown is appropriate according to the degree of surface roughness, and the effect of reducing hull friction resistance by air lubrication can be exerted as efficiently as when the bottom of the ship is not heavily fouled and has low surface roughness, even when the surface roughness is high due to bottom fouling. Furthermore, when using any one of equations (3), (4) to (6), or equation (7), the surface roughness required when calculating the amount of blown air can be calculated with high accuracy.

[0040] Next, we will describe an air lubrication system that can remotely monitor and support air lubrication in a ship underway. Figure 7 is a schematic diagram of the air lubrication system. The air lubrication system consists of a computer 10, navigation status acquisition means 30, condition input means 20, and output means 40 of the air lubrication device described above, which are installed on the ship 1, and a monitoring means 50 installed in a location away from the ship 1, such as on land. The vessel 1 is equipped with communication means 5 for communication with the outside world, and the computer 10 and monitoring means 50 are connected by an information and communication network 60 such as the Internet. In addition, the computer 10 is also connected by the information and communication network 60 to a real-world sea performance calculation means 70 located in a remote location separate from the monitoring means 50.

[0041] The monitoring means 50 is used for remote monitoring of the operating status of the vessel 1 and includes a computer and monitor. The monitoring means 50 is connected to a condition input means 80 similar to the condition input means 20 on the vessel 1, and the monitor can use the condition input means 80 to input conditions and formulas necessary to determine the amount of blown air to the monitoring means 50, such as the shape coefficient and the number of years since completion. The input conditions and formulas are transmitted from the monitoring means 50 to the computer 10 on the vessel 1 and stored in the first storage unit 108 or the second storage unit 109. This allows the computer 10 on the vessel 1 to determine the amount of blown air based on the conditions and formulas set remotely. Furthermore, the data on the amount of air to be discharged determined by the computer 10 is output from the output means 40 to the communication means 5 and transmitted to the monitoring means 50, allowing the observer to remotely check the amount of air to be discharged determined by the computer 10. The observer can also continuously monitor the surface roughness of the ship's bottom through the monitoring means 50 and determine the timing of the next dry-docking and the repairs to be carried out during dry-docking based on the increasing trend of surface roughness. In addition, the computer 10 installed on the ship 1 can be installed in a remote location other than the ship 1, or the functions of the computer 10 can be installed together with the monitoring means 50, and the calculation results can be transmitted from the information provision unit 111 to the ship 1 via the information communication network 60 to control the air supply control device 4, allowing for any combination of components of the air lubrication system via the information communication network 60.

[0042] The actual sea performance calculation means 70 can use CFD (Computational Fluid Dynamics) or the like to calculate the Reynolds number and the drag coefficient which increases due to waves and wind, and transmit the calculated values ​​to the computer 10 of the ship 1. This reduces the load on the computer 10 equipped with the preliminary calculation unit 103 by having the actual sea performance calculation means 70 perform at least a portion of the preliminary calculations.

[0043] Next, with respect to the present invention, we will describe a tank test conducted to investigate the effect of fouling of the ship's bottom due to biological attachment and increased surface roughness due to aging on the resistance reduction effect of air lubrication. In this tank test, four types of surfaces were tested: three types of roughness plates with roughness levels simulating the shape of barnacles, and one type of smooth plate (smooth surface plate) as a reference. Each plate was attached to the bottom of a long flat plate model ship 6, and the resistance under air lubrication was measured.

[0044] Figure 8 is a bottom view of a long, flat-plate model ship, showing the mounting positions for rough or smooth plates. The long-length flat-plate model ship 6 is a model ship designed to allow tank testing at a length close to that of an actual ship and at the same speed as an actual ship, with the aim of conducting tests under conditions that simultaneously satisfy the Reynolds number, which is the governing parameter of frictional resistance, and the Weber number, which is the governing parameter related to the behavior of bubbles such as coalescence and splitting. The long-length flat-plate model ship 6 is 20.6m long and 1m wide, with a flat bottom, and is used with a draft of 50mm to 80mm. The long-length flat-plate model ship 6 is designed to minimize wave resistance and shape resistance components even when towed at high speeds equivalent to those of an actual ship.

[0045] Table 1 below shows the main specifications of the long-length flat-plate model ship 6. In this experiment, to investigate the effects of hull fouling and increased surface roughness on the air lubrication effect, a flat plate with a shape parameter-controlled roughness was attached to the bottom of one block (8.0m in length) of a long flat plate model ship 6, which consists of three blocks, and the amount of resistance reduction due to air lubrication was measured. The long-length plank model ship 6 is constructed by combining a 6.0m long bow block, an 8.0m long central block which is a parallel section, and a 6.0m long stern block. Rails are attached to both ends of the bottom of the central block and on both sides of the center keel so that each plank can be attached. The shaded areas in Figure 8 indicate the attachment positions of the test planks. To prevent any steps from occurring at the connections between the various sections of the hull after the installation of the test plate, 30 cm long connecting sections were incorporated between each section to allow for adjustment of the hull's height. In addition, an air outlet 6A for bubble formation was provided in the bow block. [Table 1]

[0046] The bottom of the central block of the long-flat-plate model ship 6 (8m in length x 1m in width) is divided into two sections by a center keel. Rail-shaped channel fittings, which are flat-plate model fixing jigs, are attached to the end plates and center keel installed on both sides of the long-flat-plate model ship 6. Using this, a total of 20 flat plates, each 800mm in length and 493mm in width, were arranged in a pattern of 10 plates in the bow-stern direction and 2 plates in the width direction, and installed on the bottom of the long-flat-plate model ship 6.

[0047] The roughness formed on the roughness plate was designed to simulate the fouling caused by organisms and other organisms that occurs on the bottom of a ship during actual operation. Specifically, the fouling caused by barnacles and other organisms, which have a significant impact on hull resistance, was targeted, and the roughness was designed to mimic a controlled geometric shape that resembles barnacles. The roughness shape, which mimics that of a barnacle, was based on the paper "Uzun, D., Zhang, Y., Demirel, Y., K., and Turan, O., Experimental Determination of Added Resistance due to Barnacle Fouling on Ships by Using 3D Printed Barnacles, The 5th International Conference on Advanced Model Measurement Technology for the Maritime Industry, 2017," which investigated the increase in resistance caused by barnacles. The simulated roughness levels were of three types: low roughness, medium roughness, and high roughness. They were arranged in an equally spaced grid pattern, and the spacing was determined so that the total frontal projected area of ​​each roughness level was equal.

[0048] Table 2 below shows the specifications of the roughness shape, and Table 3 below shows the intervals and number of roughness levels. Figure 9 shows the shape of each roughness level, with Figure 9(a) being small roughness, Figure 9(b) being medium roughness, and Figure 9(c) being large roughness. Figure 10 shows the arrangement of roughness levels on a roughened plate, with Figure 10(a) being small roughness, Figure 10(b) being medium roughness, and Figure 10(c) being large roughness. The low-roughness plate has a diameter of 2.5 mm, a height of 1.25 mm, and a spacing of 10 mm between the front, back, left, and right sides. The medium-roughness plate has a diameter of 5.0 mm, a height of 2.5 mm, and a spacing of 20 mm between the front, back, left, and right sides. The high-roughness plate has a diameter of 10.0 mm, a height of 5.0 mm, and a spacing of 40 mm between the front, back, left, and right sides. As described above, each rough or smooth plate is 800 mm long and 493 mm wide, and 20 of each of the four types of plates were manufactured. [Table 2] [Table 3]

[0049] During the test, the towing speed was set to two patterns: 5.0 m / s and 6.0 m / s. The parameter used to represent the amount of blown air was the equivalent air film thickness tb [mm] shown in equation (2) below.

number

[0050] First, a resistance test was conducted using a long, flat plate model ship 6, which had smooth or roughened surfaces attached, without air lubrication. Figure 11 shows the results of this resistance test. Note that the total resistance value Rt has been converted to the value at a water temperature of 15°C. Figure 11 shows that the resistance is greater on the roughened surface compared to the smooth surface. The total frontal projected area of ​​the roughness is consistent regardless of the degree of roughness, but there is a tendency for the increase in resistance to be greater with greater roughness. Since roughness exists in a region of the boundary layer velocity distribution, it is thought that when the roughness is small and the height is low, the portion that exists in the slower velocity region of the boundary layer increases, resulting in a smaller increase in resistance. Furthermore, it can be observed that as the towing speed increases, the difference in the amount of resistance increase due to the roughness level decreases. This is thought to be because as the towing speed increases, the boundary layer thins, and therefore the difference in the average flow velocity of the flow hitting the roughness due to differences in roughness level decreases.

[0051] Next, a resistance test was conducted using a long, flat-plate model ship 6, which was fitted with smooth or roughened surfaces, under air-lubricated conditions. Figures 12 and 13 show the relationship between the amount of blown air (equivalent air film thickness) and the resistance value based on the results of this resistance test. Figure 12 shows the case at a towing speed of 5.0 m / s, and Figure 13 shows the case at a towing speed of 6.0 m / s. The total resistance value Rt has been converted to the value at a water temperature of 15°C. Figures 12 and 13 show that for all rough surfaces, as the amount of blown air increases, the total resistance value approaches that of a smooth surface, eventually becoming approximately the same. Furthermore, a lower roughness level tends to achieve a total resistance value equivalent to that of a smooth surface with a smaller amount of blown air.

[0052] The drag reduction rate was determined by dividing the amount of drag reduction due to air lubrication by the frictional resistance of the smooth surface of the air-coated section. Figure 14 shows the relationship between the amount of blown air and the drag reduction rate dR / Rf0 at a towing speed of 5.0 m / s, and Figure 15 shows the relationship between the amount of blown air and the drag reduction rate at a towing speed of 6.0 m / s. For the drag reduction rate, "dR" is the amount of drag reduction, and "Rf0" is the frictional resistance value of the smooth plate without air lubrication, calculated using Schoenherr's formula. As shown in Figures 14 and 15, on a smooth surface, the resistance reduction rate increases almost proportionally to the increase in the amount of air blown out, and saturates when the resistance reduction rate approaches 100%. On the other hand, on a rough surface, the overall trend is the same as on a smooth surface, but the resistance reduction rate is higher than that of a smooth surface. In the case of a rough surface, the frictional resistance of a smooth surface is used as a reference, and since the resistance without air lubrication is inherently high, it eventually saturates at a resistance reduction rate of over 100%, but it is thought that it saturates at a frictional resistance value similar to that of a smooth surface when the resistance reduction rate is saturated.

[0053] The results of the tank test revealed the following: - Hull frictional resistance was greater when the bottom surface was rough than when it was smooth, and increased with increasing roughness. - When the bottom surface of a ship is rough, the drag reduction effect of air lubrication is greater than when the surface is smooth. - When the bottom surface of the hull is rough, the frictional resistance is greater than that of a smooth surface in the range where the amount of blown air is small, but when the amount of blown air exceeds a certain value, it becomes approximately the same as that of a smooth surface. These results confirm that even if the hull becomes fouled and its roughness increases during actual operation, applying the present invention can suppress or prevent a decrease in the resistance reduction effect due to air lubrication. Furthermore, it was found that using the air lubrication method reduces the impact of increased resistance due to roughness compared to not using it, resulting in a higher energy-saving effect. [Industrial applicability]

[0054] By implementing the air lubrication method using the present invention, the effects of increased resistance due to hull fouling can be reduced, and fuel efficiency during actual ship operation can be improved. Furthermore, the air lubrication method using the present invention can also be applied to periodic blow-out air lubrication systems that intermittently blow air. It can also be applied to side-blowing type air lubrication systems that consider not only the surface roughness of the hull bottom but also the surface roughness of the hull sides. [Explanation of symbols]

[0055] 1 ship 10 Computers 101 Condition Acquisition Unit 20. Condition Input Means 30 Means for acquiring navigation status 40 Output means 50 Monitoring methods 60 Information and Communication Networks S1 Condition Acquisition Step S2 Ship speed acquisition step S3 Preliminary calculation step S4 Surface Roughness Calculation Step S6 Air volume determination step

Claims

1. A program for controlling an air lubrication system that reduces frictional resistance by flowing air through the bottom of a ship, On the computer, A condition acquisition step to acquire input conditions necessary to determine the amount of blown air (Q) to be blown out to the bottom of the ship, A ship speed acquisition step to obtain information about ship speed (V), A surface roughness calculation step for calculating the surface roughness (ks) of the bottom of the ship, A control program for an air lubrication system that takes into account the surface roughness of a ship's bottom, characterized by executing an air volume determination step that determines the amount of blown air (Q) to be blown onto the ship's bottom based on the relationship between the ship's speed (V) obtained in the ship's speed acquisition step, the surface roughness (ks) calculated in the surface roughness calculation step, and the air film thickness of the air covering the surface of the ship's bottom.

2. The control program for an air lubrication device that takes into account the surface roughness of the ship's bottom according to claim 1, characterized in that in the step of determining the amount of air, the air film thickness is set to the equivalent air film thickness (tb), and the amount of blown air (Q) is determined using equations (1) and (2). [Math 1] [Math 2] tb (mm): Equivalent air film thickness ks (μm): Surface roughness V (m / s): Ship speed Q (l / s): Discharge air volume Bt (m): Width of the air-covered area

3. The control program for an air lubrication device that takes into account the surface roughness of a ship's bottom according to claim 1, characterized in that the surface roughness (ks) is calculated using equations (3) and (4) in the surface roughness calculation step. [Math 3] [Math 4] ΔC Ｆ Coarseness correction factor n: Propeller rotation speed QB: Propeller Torque η Ｄ : Quasi-propulsion efficiency ρ: Density (seawater) S: flooded surface area V: Ship speed C Ｗ Wave resistance coefficient k: shape factor C Ｆ : coefficient of friction C ＡＤ : Drag coefficient increases due to waves and wind L (m): Draft length when fully loaded.

4. The control program for an air lubrication device that takes into account the surface roughness of a ship's bottom according to claim 1, characterized in that the surface roughness (ks) is calculated using equations (3) and (5) in the surface roughness calculation step. [Math 3] [Math 5] ΔC Ｆ Coarseness correction factor n: Propeller rotation speed QB: Propeller Torque η Ｄ : Quasi-propulsion efficiency ρ: Density (seawater) S: flooded surface area V: Ship speed C Ｗ Wave resistance coefficient k: shape factor C Ｆ : Coefficient of friction C ＡＤ : The drag coefficient increases due to waves and wind. L (m): Draft length when fully loaded. Re: Reynolds number

5. The control program for an air lubrication device that takes into account the surface roughness of a ship's bottom according to claim 1, characterized in that the surface roughness (ks) is calculated using equations (3) and (6) in the surface roughness calculation step. [Math 3] [Math 6] ΔC Ｆ Coarseness correction factor n: Propeller rotation speed QB: Propeller Torque η Ｄ : Quasi-propulsion efficiency ρ: Density (seawater) S: flooded surface area V: Ship speed C Ｗ Wave resistance coefficient k: shape factor C Ｆ : coefficient of friction C ＡＤ : The drag coefficient increases due to waves and wind. L (m): Draft length when fully loaded. B (m): Mold width d(m): Draft of the midship section of the hull when loaded with cargo. Re: Reynolds number

6. A control program for an air lubrication device that takes into account the surface roughness of a ship's bottom, characterized in that the surface roughness (ks) is calculated using formula (7) in the surface roughness calculation step, as described in claim 1. [Number 7] Yb: Number of years since completion Yd: Number of years since the last docking

7. An air lubrication system that reduces frictional resistance by blowing air onto the bottom of a ship, Computers and, A condition input means for inputting the conditions necessary to determine the amount of blown air (Q) to be blown out to the bottom of the ship, Navigation state acquisition means for acquiring the navigation state of the aforementioned vessel, including the ship speed (V), It includes an output means, An air lubrication system that takes into account the surface roughness of the ship's bottom, characterized in that the computer executes a control program for the air lubrication system that takes into account the surface roughness of the ship's bottom as described in any one of claims 1 to 6, and outputs at least the determined amount of blown air (Q) from the output means to control the air supply control device.

8. The computer is configured to execute a control program for an air lubrication system that takes into account the surface roughness of the ship's bottom as described in claim 2. The air lubrication device for a ship's bottom that takes into account the surface roughness of the ship's bottom according to claim 7, characterized in that the condition acquisition unit of the computer acquires at least one of the equivalent air film thickness (tb) and the air coverage width (Bt).

9. The computer is configured to execute a control program for an air lubrication system that takes into account the surface roughness of the ship's bottom, as described in claim 3. The navigation state acquisition means acquires at least one of the propeller rotation speed (n) and the propeller torque (QB), and the condition acquisition unit acquires the quasi-propulsion efficiency (η). Ｄ ), density of seawater (ρ), surface area submerged (S), wave resistance coefficient (C) Ｗ ), shape factor (k), frictional resistance coefficient (C) Ｆ ), the drag coefficient (C) increases due to waves and wind. ＡＤ The air lubrication system for the bottom of a ship that takes into account the surface roughness of the ship, as described in claim 7, characterized in that it obtains at least one of the following: the waterline length (L) in a planned fully loaded state.

10. The computer is configured to execute a control program for an air lubrication system that takes into account the surface roughness of the ship's bottom as described in claim 4. The navigation state acquisition means acquires at least one of the propeller rotation speed (n) and the propeller torque (QB), and the condition acquisition unit acquires the quasi-propulsion efficiency (η). Ｄ ), density of seawater (ρ), surface area submerged (S), wave resistance coefficient (C) Ｗ ), shape factor (k), frictional resistance coefficient (C Ｆ ), the drag coefficient (C) increases due to waves and wind. ＡＤ The air lubrication system for the bottom of a ship that takes into account the surface roughness of the ship, as described in claim 7, characterized in that it obtains at least one of the following: the waterline length (L) in a planned fully loaded state, and the Reynolds number (Re).

11. The computer is configured to execute a control program for an air lubrication system that takes into account the surface roughness of the ship's bottom as described in claim 5. The navigation state acquisition means acquires at least one of the propeller rotation speed (n) and the propeller torque (QB), and the condition acquisition unit acquires the quasi-propulsion efficiency (η). Ｄ ), density of seawater (ρ), surface area submerged (S), wave resistance coefficient (C) Ｗ ), shape factor (k), frictional resistance coefficient (C Ｆ ), the drag coefficient (C) increases due to waves and wind. ＡＤ The air lubrication system for the bottom of a ship that takes surface roughness into consideration, according to claim 7, characterized in that it obtains at least one of the following: the waterline length (L) in the planned fully loaded state, the mold width (B), the draft at the center of the hull in the cargo-loaded state (d), and the Reynolds number (Re).

12. The computer is configured to execute a control program for an air lubrication system that takes into account the surface roughness of the ship's bottom as described in claim 6. The air lubrication system for the bottom of a ship that takes into account the surface roughness of the ship, as described in claim 7, characterized in that the condition acquisition unit acquires at least one of the number of years since completion (Yb) and the number of years since the last docking (Yd) as needed.

13. An air lubrication system that reduces frictional resistance by blowing air onto the bottom of a ship, An air lubrication system for a ship's bottom that takes into account the surface roughness of the ship's bottom as described in claim 7, comprising a computer, a means for acquiring navigation conditions, a means for inputting conditions, and an output means, wherein the ship is equipped with a monitoring means located at a remote location away from the ship, and the computer and the monitoring means are connected via an information and communication network, enabling the monitoring means to receive condition inputs from other condition input means and signals from the output means at the remote location.

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