A method for calculating the emergency anchor-dragging braking distance of a ship

Abstract

The present invention discloses a method for calculating the emergency anchor dragging braking distance of a ship, including: establishing a ship deceleration motion equation according to the water resistance acting on the hull, the dynamic grip of the anchor during braking, and Newton's second law; obtaining the longitudinal additional mass empirical value of the moving ship, and obtaining the water resistance coefficient relationship formula based on it; fitting the corresponding anchor dynamic grip coefficient under the ratio of different chain lengths to anchoring depths, and obtaining the dynamic grip function of ordinary stockless anchors and large grip anchors; substituting the obtained water resistance coefficient relationship formula and the anchor dynamic grip function into the ship deceleration motion equation, and obtaining the estimation formula of the dragging single anchor braking distance of ordinary stockless anchor ships and the estimation formula of the dragging single anchor braking distance of large grip anchor ships. The calculation method of the present application takes into account the influence of physical parameters such as ship additional mass and water resistance on the dragging anchor braking distance, and is more scientific and reasonable compared with the existing dragging anchor braking distance estimation formula, and has a wider applicable ship speed range and more reliable calculation results.

Description

Technical Field

[0001] The present invention relates to the technical field of braking distance calculation, and in particular to a method for calculating the emergency anchor-dragging braking distance of a ship. Background Art

[0002] When a ship needs emergency braking during navigation, conventional ship braking can be divided into the following main forms according to different working principles and technical means:

[0003] Reverse Braking: When you need to quickly slow down or stop the boat, you can switch the main engine to reverse mode and use reverse thrust to achieve braking effect. This method is particularly effective in emergency situations.

[0004] Turning brake: After the ship turns the rudder to the left or right, the ship's oblique resistance and rudder resistance increase, and the ship's speed decreases significantly. This method is suitable for open waters.

[0005] Z-type braking: To protect the main engine, first reduce the speed of the ship by repeatedly operating the left and right rudders, and then reverse when the speed drops to a low level to stop the ship as quickly as possible. This method is particularly effective when the initial speed is high.

[0006] Anchor dragging and braking: In an emergency, the anchor can be dropped to generate resistance to help the ship slow down faster or stop in time. Therefore, the anchor is the "second life" of the captain and the pilot. When in restricted waters, the ship has a sudden machine failure that causes it to lose control, encounters extremely bad weather that makes it impossible to sail safely, or there is an imminent danger with other ships or facilities, in order to avoid maritime traffic accidents or reduce accident losses, the pilot usually drops a short chain anchor to further control the movement of the ship. In the practice of anchoring, whether it is emergency risk avoidance or operational safety, the pilot is most concerned about the ship's anchor dragging and braking distance. However, in the prior art, the calculation of the anchor dragging and braking distance mostly relies on the experience of the pilot, and there is no clear and standardized calculation standard. Therefore, the present application proposes a method for measuring the emergency anchor dragging and braking distance of a ship to solve the above problems. Summary of the invention

[0007] Therefore, the purpose of the present invention is to provide a method for calculating the emergency anchor dragging braking distance of a ship, so as to provide a theoretical basis and data support for emergency anchor dragging operation.

[0008] In order to achieve the above object, a method for calculating the emergency anchor dragging braking distance of a ship according to the present invention comprises the following steps:

[0009] S1. According to the water resistance acting on the hull when the ship moves against the water, the dynamic grip of the anchor during anchor dragging and braking, and Newton's second law, the ship deceleration motion equation is established.

[0010]

[0011] Where: is the anchor-hauling braking distance; is called the coefficient of inertia; is the water resistance coefficient; is the initial velocity, is the dynamic holding force of the anchor; is the longitudinal additional mass of the moving ship;

[0012] S2. Obtaining the longitudinal added mass empirical value of the moving ship, and obtaining the water resistance coefficient relationship according to the longitudinal added mass empirical value of the moving ship;

[0013] S3, fitting the corresponding anchor dynamic holding force coefficient under different ratios of the chain length to the anchoring depth, and obtaining the dynamic holding force function of the common stockless anchor and the dynamic holding force function of the large holding force anchor;

[0014] S4, Substitute the water resistance coefficient relationship obtained in S2 and S3 and the dynamic gripping force function of the anchor into the ship deceleration motion equation in S1 to obtain

[0015] Estimation formula for the braking distance of a common stockless anchor vessel

[0016]

[0017] Estimation formula for the braking distance of a single anchor for a ship with a large holding power anchor

[0018]

[0019] Further preferably, the water resistance includes wave-making resistance, friction resistance and eddy resistance; the friction resistance is proportional to 1.852 power of the ship's speed against the water; the wave-making resistance is proportional to the fourth power of the ship's speed against the water; and the eddy resistance is proportional to the square of the ship's speed against the water;

[0020] When a ship enters or leaves a port, the speed of the ship against the water is small, which can be simplified as water resistance. ; is the water resistance coefficient; is the speed of the ship moving through the water.

[0021] Further preferably, the range of the empirical value of the longitudinal additional mass of the moving ship is 0.07m to 0.1m. In shallow water, the longitudinal additional mass of the moving ship is selected , For the quality of the ship.

[0022] Further preferably, in S3, obtaining the corresponding anchor dynamic gripping force under different ratios of the chain length to the anchoring depth, and fitting comprises the following steps:

[0023] S301. According to the general formula of the dynamic holding force of the anchor:

[0024]

[0025] S302, fitting the dynamic holding force of the anchor at different ratios of the chain length to the anchoring depth, and obtaining a fitting formula for the dynamic holding force coefficient of the anchor

[0026]

[0027] n is the chain out multiple, the ratio of different chain out lengths to anchor depth;

[0028] S303, fitting formula of dynamic holding force coefficient of anchor Substituting into the general formula of the dynamic holding force of the anchor, the dynamic holding force function of the common stockless anchor is obtained:

[0029] ;

[0030] According to the holding force of the large holding force anchor is twice that of the ordinary stockless anchor, the dynamic holding force function of the large holding force anchor .

[0031] Further, preferably, it also includes S5, taking oil tankers S, C, K and container ship W as sample ships, estimating the anchor dragging braking distances of all sample ships under different initial velocities and different chain lengths; judging the actual influencing factors of the anchor dragging braking distance according to the estimated results of the anchor dragging braking distance, and drawing a change diagram of the water resistance and the single anchor dynamic holding force under different ratios of the chain length to the anchoring depth to verify the estimation accuracy.

[0032] The method for calculating the emergency anchor dragging braking distance of a ship disclosed in the present application has at least the following advantages over the prior art:

[0033] 1. The method for calculating the emergency anchor dragging braking distance of a ship disclosed in the present application takes into account the influence of physical parameters such as the ship's additional mass and water resistance on the anchor dragging braking distance. Compared with the existing ship low-speed anchor dragging braking distance estimation formula, it is more scientific and reasonable, and the calculation result is more reliable.

[0034] 2. The method for calculating the emergency anchor-dragging braking distance of a ship disclosed in the present application is simple and practical. The pilot only needs to use tools such as a stopwatch and a calculator built into a mobile phone to obtain the anchor-dragging braking distance of the ship.

[0035] 3. According to the method for calculating the emergency anchor dragging and braking distance of a ship disclosed in the present application, the pilot can estimate in advance the anchor dragging and braking distance of the ship under a typical load state, and use the ship's position when the chain is loosened to the planned chain length as the center of the circle and the anchor dragging and braking distance as the radius to determine the maximum range of the ship's anchor dragging and braking movement, so that when the ship encounters an abnormal situation, it can make correct decisions in a timely and effective manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic flow chart of a method for calculating the emergency anchor dragging and braking distance of a ship provided by the present invention.

[0037] Figure 2 The method for calculating the emergency anchor dragging braking distance of a ship provided by the present invention is used for an S-wheel. The variation diagrams of water resistance and single anchor dynamic holding force at 2, 3, 4 and 5 respectively. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below through the accompanying drawings and specific embodiments.

[0039] The ship's anchor-dragging braking motion is a non-uniform deceleration motion. In order to estimate the ship's anchor-dragging braking distance, the following conditions are usually assumed: the seabed is flat and still water; after the anchor falls to the bottom, the anchor claws can bite into the bottom soil without turning over, that is, the dynamic grip of the anchor is a constant; it always maintains a straight line motion; in the horizontal direction, it is only affected by water resistance and anchor chain tension, and the anchor chain tension depends on the dynamic grip of the anchor.

[0040] like Figure 1 As shown, a method for calculating the emergency anchor dragging braking distance of a ship provided by an embodiment of one aspect of the present invention comprises the following steps:

[0041] S1. According to the water resistance acting on the hull when the ship moves against the water, the dynamic grip of the anchor during anchor dragging and braking, and Newton's second law, the ship deceleration motion equation is established;

[0042] (Formula 7)

[0043] Where: is the anchor-hauling braking distance, m; is called the coefficient of inertia, m; The unit is N·s 2 / m 2 ; The unit is m / s.

[0044] In order to determine the distance of anchor dragging and braking movement of a ship, it is necessary to add the longitudinal mass of the moving ship , water resistance coefficient Dynamic grip of anchor Assign values ​​to other motion parameters or determine the calculation method.

[0045] S2. Obtaining the longitudinal added mass empirical value of the moving ship, and obtaining the water resistance coefficient relationship according to the longitudinal added mass empirical value of the moving ship;

[0046] The water resistance acting on the hull when the ship moves on the water It is mainly composed of friction resistance, wave resistance and eddy resistance. Among them: friction resistance is proportional to the 1.852 power of the ship's speed against the water; wave resistance is proportional to the fourth power of the ship's speed against the water; eddy resistance is proportional to the square of the ship's speed against the water. Since the ship's speed against the water is low, the Froude number is small, and the wave resistance is small during the period of entering and leaving the port, it can be considered that the water resistance acting on the hull is proportional to the square of the ship's speed against the water, that is,

[0047] (Formula 1)

[0048] Where: is the water resistance, N; is the water resistance coefficient; is the speed of the ship against the water, m / s

[0049] When the ship is dragging anchor and braking, the horizontal component of the anchor chain tension acting on the hull Mainly from the dynamic holding force of the anchor , so it can be considered that the tension of the anchor chain acting on the hull is equal to the dynamic grip of the anchor, that is,

[0050] (Formula 2)

[0051] Where: is the dynamic holding force of the anchor, in N; is the dynamic holding force coefficient of the anchor; is the anchor weight in air, in N; is the mass of a single anchor, in kg; is the acceleration due to gravity, 9.8m / s 2

[0052] When a ship is dragging anchor to brake, it is affected by water resistance and anchor chain tension, and these two forces are opposite to the direction of the ship's motion. Therefore, according to Newton's second law:

[0053] (Formula 3)

[0054] Where: is the mass of the ship, in kg; is the additional longitudinal mass of the ship, in kg; The ship's anchor dragging slowdown time, unit: s; is the instantaneous acceleration of the ship, in units According to the differential principle:

[0055] (Formula 4)

[0056] Substituting formulas (1), (2), and (4) into formula (3), we can obtain:

[0057] (Formula 5)

[0058] For formula (5) in the interval The internal integral processing is:

[0059] (Formula 6)

[0060] Where: The ship speed is Down to Anchor drag braking distance at 10000 km / h; is the initial velocity; is the final velocity. is 0, we can get:

[0061] (Formula 7)

[0062] Where: is the anchor-hauling braking distance, m; is called the coefficient of inertia, m; The unit is N·s 2 / m 2 ; The unit is m / s.

[0063] In order to determine the distance of anchor dragging and braking movement of a ship, it is necessary to add the longitudinal mass of the moving ship , water resistance coefficient Dynamic grip of anchor Assign values ​​to other motion parameters or determine the calculation method.

[0064] Longitudinal additional mass for a moving ship When a ship sails, it will drive the surrounding water to move together. The mass of this part of the water is the additional mass, and its size is related to many factors such as the underwater hull shape, the roughness of the hull, the ratio of the ship's draft to the water depth, and the vibration of the ship. Ship model experiments show that the longitudinal additional mass of the ship is (0.07~0.1) For most large and medium-sized ships entering and leaving the port, the navigable waters in the port are shallow waters, so 0.1 is taken in this paper. As additional mass for anchor dragging and braking the ship.

[0065] 1. Water resistance coefficient In order to obtain the water resistance coefficient, the ship inertia coefficient must be obtained first.

[0066] 1) The inertia coefficient expression of the ship during parking brake is:

[0067] (8)

[0068] In the formula, For oneself Down to Time required.

[0069] When the ship is in a state of slow or medium speed parking brake and linear motion, the pilot can read the GPS positioning terminal , The value of Substituting the measured value into equation (8), the value of the inertia coefficient can be calculated.

[0070] Practice has shown that the more reasonable the selected speed range and the longer the observation time, the higher the credibility of the inertia coefficient calculated by formula (8).

[0071] 2) Add 0.1 mass to the longitudinal direction of the ship Substituting into formula (8), we can get

[0072] (9)

[0073] Substituting the values ​​of ship mass and ship inertia coefficient into formula (9), the value of water resistance coefficient can be obtained.

[0074] 2. Dynamic grip of anchor

[0075] S3, fitting the corresponding anchor dynamic holding force coefficient under different ratios of the chain length to the anchoring depth, and obtaining the dynamic holding force function of the common stockless anchor and the dynamic holding force function of the large holding force anchor;

[0076] In order to obtain the dynamic holding force formula of the anchor under different ratios of the chain length to the water depth, the silt bottom is selected to fit the dynamic holding force coefficient of the anchor, so that the dynamic holding force coefficient expression of the ordinary stockless anchor is obtained as follows:

[0077] (10)

[0078] Where: It is the chain out multiple, that is, the ratio of the chain out length to the water depth.

[0079] The fitting values ​​and fitting error values ​​are shown in Table 1. It can be seen that the calculation accuracy of the fitting formula (10) is very high and can be directly quoted.

[0080] Table 1 Dynamic holding force coefficient of common stockless anchor at different ratios of chain length to water depth [4] and fitting error

[0081]

[0082] According to the references, the holding force of a high holding force anchor is at least twice that of an ordinary stockless anchor of the same mass. Therefore, the dynamic holding force coefficient of a high holding force anchor can be expressed as

[0083] (11)

[0084] Substituting equation (10) into equation (2), the dynamic holding force expression of a common stockless anchor can be obtained:

[0085] (12)

[0086] Substituting equation (11) into equation (2), we can get the dynamic holding force expression of the large holding force anchor:

[0087] (13)

[0088] The ships are divided into ships equipped with ordinary stockless anchors and ships equipped with large holding power anchors in order to obtain the expression for the braking distance of ships dragging anchors.

[0089] 1) Anchor-dragging braking distance for vessels equipped with common stockless anchors

[0090] Will Substituting formula (12) into (7), the estimation formula for the braking distance of a single anchor for a ship equipped with an ordinary stockless anchor is:

[0091] (14)

[0092] 2) Anchor-dragging braking distance for ships equipped with high-holding anchors

[0093] Will Substituting formula (13) into (7), the estimation formula for the braking distance of a towing anchor of a ship equipped with a large holding power anchor is obtained:

[0094] (15)

[0095] It also includes S4, taking oil tankers S, C, K and container ship W as sample ships, and estimating the anchor dragging and braking distances of all sample ships under different initial velocities and different chain lengths; based on the estimated results of the anchor dragging and braking distances, the actual influencing factors of the anchor dragging and braking distances are judged, and a graph of the changes in water resistance and single anchor dynamic holding force under different ratios of chain lengths to anchoring depths is drawn to verify the accuracy of the estimation.

[0096] In order to facilitate technical personnel in this field to intuitively understand the algorithm of the ship anchor dragging braking distance and explore the changing law of the ship anchor dragging braking distance, the oil tanker S, the handymax C, K and the container ship W are selected as sample ships (the main data are listed in Table 2), and the anchor dragging braking distances of these merchant ships under different initial velocities and different chain lengths are estimated.

[0097] Table 2 Main data of sample ships

[0098]

[0099] The initial speed of the ship during low-speed parking brake will be measured , Final velocity and deceleration time Substitute into formula (8) to calculate the ship inertia coefficient The values ​​of are tabulated, and then the values ​​of the ship mass and inertia coefficient are substituted into formula (9) to calculate the ship water resistance coefficient See Table 3 for the values ​​of

[0100] Table 3 Measured values ​​of sample ship speed and stopping time and calculated values ​​of inertia coefficient and water resistance coefficient

[0101]

[0102] According to the type of anchor equipped on the ship, select formula (14) or (15), and substitute the ship mass, water resistance coefficient, anchor mass and other parameter values ​​into the corresponding expression to obtain the estimation formula of the ship's anchor dragging braking distance.

[0103] The practical estimation formula for the braking distance of an S-wheel towing a single anchor is:

[0104] (16)

[0105] According to the above formula, for a specific ship, the anchor-dragging braking distance is only related to the initial speed of the ship and the chain-out multiple; when braking with two anchors, the anchor chain tension acting on the ship is twice the dynamic grip of a single anchor. The values ​​of are 8kn, 6kn, 4kn, 3kn, and 2kn (kn needs to be converted to m / s during calculation), and assuming that the chain multiples are 2, 3, 4, and 5, respectively, the anchor drag braking distance of the S wheel is calculated. The specific values ​​are shown in Table 4

[0106] Table 4 S-wheel anchor dragging braking distance

[0107]

[0108] The practical estimation formula for the braking distance of a C-wheel towing single anchor is:

[0109] (17)

[0110] Similarly, the anchor dragging braking distance of wheel C can be calculated as shown in Table 5.

[0111] Table 5 C wheel anchor dragging braking distance

[0112]

[0113] The practical estimation formula for the braking distance of a K-vehicle towing a single anchor is:

[0114] (18)

[0115] Similarly, the anchor dragging braking distance of ship K can be calculated, as shown in Table 6.

[0116] Table 6 Anchor dragging braking distance of wheel K

[0117]

[0118] The practical estimation formula for the braking distance of a W-trailer towing a single anchor is:

[0119] (19)

[0120] Similarly, the anchor dragging braking distance of ship W can be calculated as shown in Table 7.

[0121] Table 7 W-wheel anchor dragging braking distance

[0122]

[0123] By comparing and analyzing the anchor-dragging braking distances of ships listed in Tables 4 to 7, the following rules can be found:

[0124] 1) For any ship, its anchor-dragging braking distance has the following characteristics:

[0125] ① With the increase of chain out multiples, the anchor dragging braking distance is significantly reduced, and with the increase of chain out multiples, the reduction of anchor dragging braking distance is significantly reduced.

[0126] ② As the initial speed of the ship decreases, the anchor-dragging braking distance decreases significantly, and as the initial speed decreases, the reduction in the anchor-dragging braking distance decreases significantly.

[0127] ③ The braking distance when the ship is towing double anchors is smaller than that when towing a single anchor. With the decrease of initial velocity and the increase of chain out multiples, the braking distance when the ship is towing a single anchor is infinitely close but always less than twice the braking distance when the ship is towing double anchors.

[0128] 2) By comparing the anchor-dragging braking distances of the S-wheel and the C-wheel, it can be seen that for ships with similar block coefficients and equipped with the same anchor type, the larger the displacement, the larger the corresponding anchor-dragging braking distance.

[0129] 3) Comparing the anchor-dragging braking distances of C and K, it can be seen that for ships with similar block coefficients and approximately the same displacement, the anchor-dragging braking distance of the ship equipped with a large holding power anchor is smaller.

[0130] 4) Comparing the anchor-dragging braking distances of the K and W vessels, we can see that: for ships with approximately equal displacement and equipped with the same anchor type, the smaller the block coefficient and the larger the hull immersion area, the greater the water resistance; on the other hand, the greater the number of ship outfitting, the greater the anchor mass, and the greater the dynamic grip of the anchor. Therefore, the anchor-dragging braking distance of the W vessel is significantly smaller than that of the K vessel.

[0131] At present, when those skilled in the art estimate the anchor drag braking distance, they usually use the estimation formula given by Satoshi Iwai based on the kinetic energy theorem:

[0132] (20)

[0133] Where: is the displacement of the ship, t; is the initial ship speed, kn; is the dynamic holding force of the anchor, t.

[0134] Select the S ship as the research object, substitute formula (12) into formula (20), and substitute the ship displacement, anchor mass and other parameter values, and the estimation formula of anchor dragging braking distance when the S ship drags a single anchor is obtained:

[0135] (twenty one)

[0136] Similarly, assuming that when dragging double anchors for braking, the dynamic gripping force of the double anchors is twice that of the single anchor, the initial speed The values ​​are 8kn, 6kn, 4kn, 3kn, and 2kn, and the anchor-dragging braking distances when the chain-out multiples are 2, 3, 4, and 5, respectively. The specific calculation results are listed in Table 8.

[0137] Table 8 Estimation formula for the braking distance of the S-wheel anchor dragging

[0138]

[0139] Comparing the data in Table 4 and Table 8, the following characteristics can be found:

[0140] 1) When the initial speed of the anchor-dragging braking of the S wheel is 8 kn and 6 kn, the calculated value according to formula (20) is significantly greater than the calculated value according to formula (16), and the greater the initial speed and the smaller the chain-out multiple, the greater the difference in the anchor-dragging braking distance.

[0141] 2) When the initial speed of the anchor-dragging braking motion of the S wheel is 4 kn, 3 kn, and 2 kn, the calculated value based on formula (20) and the calculated value based on formula (16) are slightly different with the different chain-out multiples.

[0142] 3) The data in Table 8 show that, under the same initial speed conditions, the braking distance of the S-wheel towing a single anchor is twice the braking distance of towing two anchors.

[0143] The following will compare the estimation formula (20) given by Satoshi Iwai based on the kinetic energy theorem adopted in the prior art with the estimation formula (14) for the braking distance of a common stockless anchor ship and the estimation formula (15) for the braking distance of a high-holding anchor ship proposed in this application.

[0144] 1) The estimation formula (20) in the prior art does not take into account the effect of the longitudinal additional mass of the ship on the anchor dragging braking distance, while the estimation formulas (14) and (15) of the present application involve the longitudinal additional mass of the ship.

[0145] 2) The estimation formula (20) in the prior art does not involve water resistance, while the estimation formulas (14) and (15) of the present application reflect the influence of water resistance on the anchor-dragging braking distance of a ship.

[0146] In order to further illustrate the influence of water resistance on the anchor-dragging braking distance of a ship, the water resistance of the S-wheel is taken as an example to compare it with the dynamic holding force of a single anchor.

[0147] The water resistance of wheel S is:

[0148] (twenty two)

[0149] The dynamic holding force of a single anchor is:

[0150] (twenty three)

[0151] According to formula (22) and (23), Take 2, 3, 4, and 5 respectively, and use drawing software to draw the change diagram of water resistance and single anchor dynamic holding force, as shown in Figure 2 shown.

[0152] When the speed of the S wheel on the water is 4.7 kn, the water resistance it encounters is equal to the dynamic grip of the anchor when the length of the chain is 2 times the water depth. As the speed on the water increases, the water resistance increases sharply. When the speed of the S wheel on the water is 8.2 kn, the water resistance it encounters is equal to the dynamic grip of the anchor when the length of the chain is 5 times the water depth. Obviously, the higher the speed of the S wheel on the water, the greater the impact of the water resistance on the anchor drag braking distance, and the more distorted the calculated value of the estimation formula (20) is.

[0153] When the speed of the S wheel against the water is 3 kn, the water resistance is 20.2 kN; when the speed of the S wheel against the water is 2 kn, the water resistance is 9.0 kN. It can be seen that the lower the speed of the S wheel against the water, the smaller the influence of the water resistance on the anchor dragging braking distance, and the smaller the error of the calculated value obtained according to formula (20).

[0154] In summary, the estimation formula (20) of the prior art is only applicable to the estimation of the anchor-dragging braking distance when the initial speed of the ship is low (less than 4 kn), while the estimation formulas (14) and (15) of the present application indicate that the anchor-dragging braking distance is related to the water resistance and are applicable to the calculation of the anchor-dragging braking distance at a higher ship speed. It can be seen that the initial speed range applicable to the formulas (14) and (15) of the present application is wider, and the calculation results are more accurate when the ship drops anchor rapidly during medium and low speed driving.

[0155] 1) Formulas (14) and (15) take into account the influence of physical parameters such as ship's additional mass and water resistance on the anchor-dragging braking distance. Compared with the traditional ship low-speed anchor-dragging braking distance estimation formula, they are more scientific and reasonable, and the calculation results are more reliable.

[0156] 2) The estimation method of this application is simple and practical. The pilot only needs to use the built-in stopwatch, calculator and other application software on the mobile phone to obtain the anchor dragging and braking distance of the ship.

[0157] 3) According to the method given in this application, the pilot can estimate in advance the anchor-dragging braking distance of the ship under typical load conditions, and use the ship's position when the chain is loosened to the planned chain length as the center of the circle and the anchor-dragging braking distance as the radius to determine the maximum range of the ship's anchor-dragging braking movement, so that when the ship encounters an abnormal situation, it can make correct decisions in a timely and effective manner.

[0158] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A method for calculating the emergency anchor-dragging braking distance of a ship, characterized in that: The following steps are involved: S1. According to the water resistance acting on the hull when the ship moves against the water, the dynamic grip of the anchor during anchor dragging and braking, and Newton's second law, the ship deceleration motion equation is established. Where: is the anchor-hauling braking distance; is called the coefficient of inertia; is the water resistance coefficient; is the initial velocity, is the dynamic holding force of the anchor; is the longitudinal additional mass of the moving ship; m is the mass of the ship; S2. Obtaining the longitudinal added mass empirical value of the moving ship, and obtaining the water resistance coefficient relationship according to the longitudinal added mass empirical value of the moving ship; S3, fitting the corresponding anchor dynamic holding force coefficient under different ratios of the anchoring chain length to the anchoring depth, and obtaining the dynamic holding force function of the common stockless anchor and the dynamic holding force function of the large holding force anchor; Obtaining the corresponding anchor dynamic gripping force under different ratios of the chain length to the anchoring depth, and fitting includes the following steps: S301. According to the general formula of the dynamic holding force of the anchor: S302, fitting the dynamic holding force of the anchor at different ratios of the chain length to the anchoring depth, and obtaining a fitting formula for the dynamic holding force coefficient of the anchor It is the chain out multiple, the ratio of different chain out lengths to the anchoring depth; m a is the mass of a single anchor; S303, fitting formula of dynamic holding force coefficient of anchor Substituting into the general formula of the dynamic holding force of the anchor, the dynamic holding force function of the common stockless anchor is obtained: ； According to the holding force of the large holding force anchor is twice that of the ordinary stockless anchor, the dynamic holding force function of the large holding force anchor ; S4, Substitute the water resistance coefficient relationship obtained in S2 and S3 and the dynamic holding force function of the anchor into the ship deceleration motion equation in S1 to obtain Estimation formula for the braking distance of a common stockless anchor vessel Estimation formula for the braking distance of a single anchor for a ship with a large holding power anchor 。 2. The method for calculating the emergency anchor dragging braking distance of a ship according to claim 1, characterized in that: The water resistance includes wave resistance, friction resistance and eddy resistance; the friction resistance is proportional to the 1.852 power of the ship's speed against the water; the wave resistance is proportional to the fourth power of the ship's speed against the water; the eddy resistance is proportional to the square of the ship's speed against the water; when the ship enters and leaves the port, the ship's speed against the water is small, which is simplified to water resistance ; is the water resistance coefficient; is the speed of the ship moving through the water.

3. The method for calculating the emergency anchor dragging braking distance of a ship according to claim 1, characterized in that: The empirical value of the longitudinal additional mass of the moving ship ranges from 0.07m to 0.1m. is the ship mass, the longitudinal additional mass of the moving ship in shallow water .

4. The method for calculating the emergency anchor dragging braking distance of a ship according to claim 1, characterized in that: It also includes S5, taking oil tankers S, C, K and container ship W as sample ships, and estimating the anchor dragging and braking distances of all sample ships under different initial velocities and different chain lengths. According to the estimated results of the anchor dragging and braking distances, the actual influencing factors of the anchor dragging and braking distances are judged, and a graph of the changes in the water resistance on the ship and the single anchor dynamic holding force under different ratios of chain lengths to anchoring depths is drawn.

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