Method for calculating coupling of number of main umbrellas and resistance coefficient of reloading air-drop system

Abstract

The invention discloses a calculation method for coupling of the number of main umbrellas and a resistance coefficient of a reloading air-drop system. According to a large number of test results, the resistance coefficient of the group parachutes is inversely calculated according to the air-drop falling speed, the air-drop weight, the landing field density and the number of the main parachutes in the air-drop test, and the relation between the resistance coefficient and the number of the main parachutes is obtained. The area of a single parachute is selected according to the air-drop weight and the air-drop landing field, when the air-drop weight is larger than 1 ton, the method is suitable for selecting a main parachute of 760 square meters, and when the air-drop weight is smaller than 1 ton, the method is not suitable. Setting an initial landing speed and an initial resistance coefficient, and calculating the number of main umbrellas according to a formula. If the air-drop weight, the landing speed and the landing field change, the number of the main parachutes can be calculated again according to the steps. The method can solve the problem of selection of the number of the main umbrellas during air-drop of the reloading air-drop system.

Description

Technical Field

[0001] This invention relates to the field of airdrop technology, and in particular to a calculation method for coupling the number of main parachutes and drag coefficient in a heavy-duty airdrop system. Background Technology

[0002] The main parachute used in the heavy equipment airdrop system is a 760-square-meter planar circular parachute. When a single main parachute cannot withstand a large load, the number of main parachutes needs to be increased, using multiple main parachutes for deceleration during the airdrop. Ignoring components such as parachute lines, the drag coefficient of a single planar circular parachute is 0.75–0.8. For the multi-parachute main parachute system in heavy equipment airdrops, the drag coefficient of individual parachutes within the group is reduced. The drag coefficient of the multi-parachute system is not a direct summation of the drag coefficients of multiple individual parachutes; currently, there is no relevant data for selecting the drag coefficient of multi-parachute systems.

[0003] Currently, there is a lack of experimental data on the drag coefficient of a heavy-duty multi-parachute system, making it difficult to calculate the number of main parachutes in a multi-parachute system. Summary of the Invention

[0004] The purpose of this invention is to provide a calculation method that couples the number of main parachutes and the drag coefficient of a heavy equipment airdrop system. This method can solve the problem of selecting the number of main parachutes during airdrop of a heavy equipment airdrop system.

[0005] The technical solution to achieve the objective of this invention is: a calculation method for the coupling of the number of main parachutes and the drag coefficient in a heavy-duty airdrop system, comprising the following steps:

[0006] (1) Drag coefficient of multiple parachutes: Based on a large amount of airdrop test data, the drag coefficients corresponding to different numbers of main parachutes are shown in Table 1.

[0007] Table 1. Drag coefficient of a single umbrella in a group umbrella system

[0008] Number of umbrellas n Drag coefficient C 2 0.971 3 0.95 4 0.929 5 0.908 6 0.887 7 0.866

[0009] The data was organized and analyzed to obtain the following relationships:

[0010] ;

[0011] (2) Parachute type selection: Based on the airdrop weight G, airdrop landing density ρ, and landing speed v of the airdrop mission, select the area A of a single parachute. If the airdrop weight is greater than 2 tons, select a main parachute of 760 square meters.

[0012] (3) Set the initial drag coefficient: The drag coefficient C1 of the main umbrella with a diameter of 760 square meters is temporarily set to the maximum value of 0.971;

[0013] (4) Calculate the initial value of the number of main umbrellas:

[0014]

[0015]

[0016] If n1, calculated using the formula, is not an integer, round it up to get n2.

[0017] (5) Iterative calculation:

[0018] a. Based on the table or formula for the drag coefficient of n2 and the group of parachutes. This yields a new drag coefficient C2;

[0019] b. Recalculate the number of main parachutes using C2:

[0020]

[0021] When n3 calculated using the formula is not an integer, round it up to get n4;

[0022] c. Compare n2 and n4. If they are equal, output the final number of main umbrellas n. If they are not equal, let n2=n4 and C1=C2, and return to step (5) to continue iterating until two adjacent roundings are consistent.

[0023] Compared with the prior art, the present invention has the following significant advantages: the present invention is based on the relationship between the drag coefficient of the group of umbrellas and the number of main umbrellas, which makes it highly operable, simple and practical, and can be used in engineering practice. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0025] The calculation method of coupling the number of main parachutes and the drag coefficient of the heavy equipment airdrop system of the present invention first calculates the drag coefficient of the group of parachutes based on a large number of test results, according to the airdrop descent speed, airdrop weight, landing zone density and the number of main parachutes in the airdrop test, and obtains the relationship between the drag coefficient and the number of main parachutes.

[0026] Secondly, the area of ​​a single parachute is selected based on the airdrop weight and the airdrop landing site. This method applies when the airdrop weight is greater than 1 ton and a 760-square-meter main parachute is selected; it does not apply when the airdrop weight is less than 1 ton. The initial landing speed and initial drag coefficient are set, and the number of main parachutes is calculated using the formula.

[0027] If the airdrop weight, landing speed, or landing site changes, the number of main parachutes can be recalculated using this method.

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] The calculation process involves the following steps:

[0030] Group parachute drag coefficient: Based on a large amount of airdrop test data, the drag coefficients corresponding to different numbers of main parachutes are shown in Table 1.

[0031] Table 1. Drag coefficient of a single umbrella in a group umbrella system

[0032] Number of umbrellas n Drag coefficient C 2 0.971 3 0.95 4 0.929 5 0.908 6 0.887 7 0.866

[0033] The data was organized and analyzed to obtain the following relationships:

[0034]

[0035] (1) Parachute type selection: Based on the airdrop weight G, airdrop landing density ρ, and landing speed v, select the area A of a single parachute. If the airdrop weight is determined to be greater than 2 tons, select a main parachute of 760 square meters;

[0036] (2) Set the initial drag coefficient: The drag coefficient C1 of the main umbrella with a diameter of 760 square meters is temporarily set to the maximum value of 0.971;

[0037] (3) Calculate the initial value of the number of main umbrellas:

[0038]

[0039]

[0040] If the n1 calculated using the formula is not an integer, round it up to get n2.

[0041] (4) Iterative calculation:

[0042] a. Based on the table or formula for the drag coefficient of n2 and the group of parachutes. Thus, a new drag coefficient C2 is obtained.

[0043] b. Recalculate the number of main parachutes using C2:

[0044]

[0045] When n3 calculated using the formula is not an integer, round it up to get n4.

[0046] c. Compare n2 and n4. If they are equal, output the final number of main umbrellas, n. If they are not equal, set n2=n4 and C1=C2, return to step 5 and continue iterating until two consecutive roundings are consistent.

[0047] The parameters such as airdrop weight G, airdrop landing density ρ, and landing speed v may change. After the changes, recalculate according to the above steps.

[0048] Flowchart as follows Figure 1 As shown.

[0049] This invention fills the gap in the current calculation of the number of main umbrellas in a cluster system. Based on the relationship between the drag coefficient of the cluster system and the number of main umbrellas, it is highly operable, simple and practical, and can be used in engineering practice.

Claims

1. A calculation method coupling the number of main parachutes and drag coefficient in a heavy-duty airdrop system, characterized in that, Includes the following steps: (1) Drag coefficient of multiple parachutes: Based on a large amount of airdrop test data, the drag coefficients corresponding to different numbers of main parachutes are shown in Table 1. Table 1. Drag coefficient of a single umbrella in a group umbrella system The data was organized and analyzed to obtain the following relationships: ； (2) Parachute type selection: Based on the airdrop weight G, airdrop landing density ρ, and landing speed v of the airdrop mission, select the area A of a single parachute. If the airdrop weight is greater than 2 tons, select a main parachute of 760 square meters. (3) Set the initial drag coefficient: The drag coefficient C1 of the main umbrella with a diameter of 760 square meters is temporarily set to the maximum value of 0.971; (4) Calculate the initial value of the number of main umbrellas: ， ， If n1, calculated using the formula, is not an integer, round it up to get n2. (5) Iterative calculation: a. Based on the table or formula for the drag coefficient of n2 and the group of parachutes. This yields a new drag coefficient C2; b. Recalculate the number of main parachutes using C2: ， When n3 calculated using the formula is not an integer, round it up to get n4; c. Compare n2 and n4. If they are equal, output the final number of main umbrellas n. If they are not equal, let n2=n4 and C1=C2, and return to step (5) to continue iterating until two adjacent roundings are consistent.

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