Amphibious aircraft water landing coefficient calculation method

Abstract

The present application belongs to the field of water load design of amphibious aircraft, and aims at the problem of accurate calculation of water landing load. The present application provides a method for calculating the water landing load coefficient of amphibious aircraft, comprising the following steps: step one, obtaining the three-wave height encountered by the sea wave according to the sea surface landing marine environment database of the amphibious aircraft, and determining the wave state coefficient; step two, determining the additional mass coefficient of the ship bottom impact according to the ship bottom parameters and the sea surface landing attitude angle of the amphibious aircraft; step three, determining the approach parameters according to the sea surface landing approach attitude angle and the track angle of the amphibious aircraft; and step four, determining the water landing load theoretical coefficient and the water landing load coefficient calculation method according to the wave state coefficient, the additional mass coefficient and the approach parameters. The present application is suitable for accurate prediction of the water landing load of the amphibious aircraft for engineering application.

Description

Technical Field

[0001] This invention belongs to the field of water load design for amphibious aircraft, and specifically relates to a method for calculating the water load of amphibious aircraft. Background Technology

[0002] Landing on water is the normal operating mode for amphibious aircraft. Due to the complexity of the water environment, especially the strong nonlinear water loads caused by waves, severe water loads can lead to deformation or damage to the hull of the amphibious aircraft. Therefore, the water load is a major design load for amphibious aircraft, and accurately predicting the water load is crucial for the structural design and strength verification of amphibious aircraft. The factors influencing the water load of amphibious aircraft are very complex, closely related to the hull shape, weight, landing speed, flight parameters, and wave environment factors. It is essential to establish a quantitative relationship between the water load and these influencing factors, especially to correlate the theoretical water load coefficient with the wave environment. Summary of the Invention

[0003] The purpose of this invention is to provide a method for calculating the water load coefficient of amphibious aircraft, addressing the problem of accurate calculation of water load. This method provides accurate load input for the structural design and strength verification of amphibious aircraft, thereby improving the safety of amphibious aircraft landing on water.

[0004] The technical solution of this invention is:

[0005] A method for calculating the water load factor of an amphibious aircraft includes:

[0006] Step 1: Based on the marine environment database for amphibious aircraft landing on the water, obtain the three-wave height of the encountered waves and determine the wave state coefficient.

[0007] Step 2: Determine the impact mass coefficient of the amphibious aircraft based on the hull parameters and the landing attitude angle on the water surface.

[0008] Step 3: Determine the approach parameters based on the amphibious aircraft's attitude angle and track angle for water landing;

[0009] Step 4: Determine the theoretical coefficient of water-laying load and the calculation method of water-laying load coefficient based on the wave state coefficient, the added mass coefficient, and the approach parameters.

[0010] Step one is as follows:

[0011] Based on the actual marine environment of an amphibious aircraft landing on water, the three-wave height of the actual landing area was obtained, and the expression for wave state coefficient was calculated: C h =0.065H 2 +0.4H+1, the wave state coefficient C of the amphibious aircraft is calculated.h Where H represents the wave height of the sea area.

[0012] Step two is as follows:

[0013] Measure the bottom lift angle at the step of the amphibious aircraft, measure the landing attitude angle of the amphibious aircraft, and then calculate the expression based on the added mass coefficient: The added mass coefficient K for the amphibious aircraft's landing on the hull is calculated; where β is the hull tilt angle at the step break, and τ is the aircraft's landing attitude angle.

[0014] Step three specifically involves:

[0015] Measure the hull tilt angle, water-touching attitude angle, and water-touching trajectory angle of the amphibious aircraft at the step, and then calculate the expression based on the approach parameters. The water approach parameters B of the amphibious aircraft were calculated; where γ is the aircraft's water approach trajectory angle, A is a parameter, and ρ is the density of water.

[0016] Step four is as follows:

[0017] After obtaining the wave state coefficient, added mass coefficient, and water approach parameters of the amphibious aircraft, the expression C = C is calculated based on the theoretical coefficient of water landing load. h BK 1 / 3 The theoretical coefficient C for the water load of the amphibious aircraft was calculated.

[0018] Based on the formula for calculating the water landing stall speed, water landing weight, and water landing load factor of amphibious aircraft The water load coefficient of the amphibious aircraft is calculated; where n w V is the water load factor, where V is the water stall speed of the amphibious aircraft, and W is the weight of the aircraft upon landing.

[0019] 0.5m≤H≤3.2m.

[0020] 15°≤β≤25°; 3°≤τ≤6°.

[0021] 1°≤γ≤4°.

[0022] The advantages of this invention are:

[0023] The method for calculating the water load of amphibious aircraft provided by this invention solves the problems of multiple influencing factors and difficulty in quantitative analysis of the water load of amphibious aircraft. It establishes a mathematical model of water load under the influence of multiple factors, obtains the correspondence between the theoretical coefficient of water load and the three-dimensional wave height, and establishes an accurate prediction method for the water load of amphibious aircraft that can be applied to engineering applications. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the hull tilt angle at the step of the amphibious aircraft of the present invention.

[0025] Figure 2 This is a schematic diagram of the amphibious aircraft's water landing attitude angle and track angle according to the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0027] To address the problem of accurate calculation of water landing load, this invention provides a method for calculating the water landing load coefficient of amphibious aircraft. This method links the water landing load coefficient with various influencing factors, enabling reasonable and accurate prediction of the water landing load. This provides accurate load input for the structural design and strength verification of amphibious aircraft, thereby improving the safety of amphibious aircraft landing on water.

[0028] The specific implementation method of the amphibious aircraft water load coefficient calculation method proposed in this invention is as follows:

[0029] A method for calculating the water-landing load coefficient of an amphibious aircraft is provided, which is used to calculate the load input when designing the structure and verifying the strength of the amphibious aircraft. The input includes: wave state coefficient, added mass coefficient, approach parameters, and theoretical water-landing load coefficient.

[0030] Based on the actual marine environment of an amphibious aircraft landing on water, the wave state coefficient is calculated using the following formula: (The formula is then used to query the ocean database for the current wave height of the sea area, or to test the wave height of the landing area using airborne wireless equipment.)

[0031] C h =0.065H 2 +0.4H+1 (0.5m≤H≤3.2m)

[0032] In the formula, C h H represents the wave state coefficient, and H represents the three-wave height of the sea area where the waves are touching the water.

[0033] Based on the hull lift angle and water landing attitude angle at the step of the amphibious aircraft, the formula for calculating the additional mass coefficient is as follows:

[0034]

[0035] In the formula, β is the angle of ascent at the bottom of the ship at the discontinuity of the step, see Appendix Figure 1 τ is the aircraft's water-touching attitude angle, see appendix. Figure 2 ,

[0036] Based on the amphibious aircraft's bottom lift angle at the step, water-touching attitude angle, and water-touching trajectory angle, the approach parameters are calculated using the following expressions:

[0037]

[0038] In the formula, γ is the aircraft's water-touch trajectory angle, see Appendix Figure 2 A is a parameter, obtained through interpolation using the table below.

[0039] tanτ / tan(τ+γ) A tanτ / tan(τ+γ) A 0.95 0.03224 0.45 0.41318 0.9 0.07536 0.4 0.44052 0.85 0.12031 0.35 0.46626 0.8 0.16452 0.3 0.49056 0.75 0.20689 0.25 0.51354 0.7 0.24699 0.2 0.53531 0.65 0.28469 0.15 0.55600 0.6 0.32002 0.1 0.57566 0.55 0.35310 0.05 0.59441 0.5 0.38410 -0.05 0.62944

[0040] Based on the wave state coefficient, added mass coefficient, and water-landing approach parameters of the amphibious aircraft, the theoretical formula for the water-landing load coefficient is as follows:

[0041] C = C h BK 1 / 3

[0042] In the formula, C is the theoretical coefficient of water load, B is the water inlet parameter, and K is the additional mass coefficient.

[0043] After obtaining the theoretical water load coefficient, the calculation method for the water load coefficient of amphibious aircraft is as follows:

[0044]

[0045] In the formula, n w V is the water load factor, V is the water stall speed of the amphibious aircraft (m / s), and W is the water weight of the aircraft (kg).

Claims

1. A method for calculating the water load coefficient of an amphibious aircraft, characterized in that, include: Step 1: Based on the marine environment database for amphibious aircraft landing on water, obtain the tri-wave height of the encountered waves and determine the wave state coefficient. Based on the actual marine environment of the amphibious aircraft landing on water, obtain the tri-wave height of the actual landing area and calculate the expression based on the wave state coefficient. The wave state coefficient C of the amphibious aircraft was calculated. h Where H represents the wave height of the sea surface. Step 2: Determine the hull impact added mass coefficient based on the amphibious aircraft's hull parameters and water landing attitude angle: Measure the hull lift angle at the step of the amphibious aircraft, measure the amphibious aircraft's water landing attitude angle, and then calculate the expression based on the added mass coefficient: The added mass coefficient of the amphibious aircraft's landing hull was calculated. K In the formula, The angle of ascent at the bottom of the boat at the break in the steps. The aircraft's attitude angle upon landing on the water. ; Step 3: Determine the approach parameters based on the amphibious aircraft's approach attitude angle and track angle: Measure the hull tilt angle, water-touching attitude angle, and water-touching track angle at the amphibious aircraft's landing point, and then calculate the expression based on the approach parameters. The parameters for the amphibious aircraft's water landing approach were calculated. B In the formula, For the aircraft's landing track angle, A For parameters, The density of water; Step 4: Determine the theoretical coefficient of the landing load and the calculation method of the landing load coefficient based on the wave state coefficient, added mass coefficient, and approach parameters: After obtaining the wave state coefficient, added mass coefficient, and landing approach parameters of the amphibious aircraft, calculate the theoretical coefficient of the landing load using the formula. The theoretical coefficient of water load for amphibious aircraft was calculated. C ; Based on the formula for calculating the water landing stall speed, water landing weight, and water landing load factor of amphibious aircraft The water load coefficient of the amphibious aircraft was calculated; where, n w For water load factor, V The stall speed of an amphibious aircraft upon landing in water; W The weight of the aircraft when it touches water.

2. The method for calculating the water load coefficient of an amphibious aircraft as described in claim 1, characterized in that, 。 3. The method for calculating the water load coefficient of an amphibious aircraft as described in claim 1, characterized in that, ； 。 4. The method for calculating the water load coefficient of an amphibious aircraft as described in claim 1, characterized in that, 。

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