Seaplane dynamic water-landing load calculation method

Abstract

The present application belongs to the technical field of aircraft load design, and relates to a seaplane dynamic water-landing load calculation method. A dynamic water-landing response analysis model is established according to rigidity distribution and mass distribution data, single wave, regular wave form and characteristics in different sea conditions are calculated in combination with aircraft parameters, the modal transient response method is used to respectively solve the incremental load response of the aircraft when encountering single wave and regular wave, the baseline load is superimposed, the dynamic water-landing load of the aircraft is obtained, then the safety factor is considered, the extreme load extreme value of each component is selected, and the dynamic water-landing extreme load envelope of the aircraft is composed. The influence of wave dynamic characteristics and aircraft elastic deformation is considered, the dynamic water-landing load of each component is quickly obtained through batch processing, the calculation efficiency is improved, the load bearing condition of the seaplane structure can be truly evaluated, which is beneficial to reduce the aircraft structure design risk and improve the optimization iteration efficiency of the aircraft structure weight, and provides a basis for aircraft load design and structure strength design.

Description

Technical Field

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

[0002] When designing the structure of a seaplane, it is essential to consider the loads on the aircraft structure when it lands on water under different wave patterns and environments. In the past, empirical formulas were mainly used to calculate the static water loads of rigid-body aircraft when landing in different attitudes. However, these methods did not consider the dynamic characteristics of waves and the effects of elastic deformation of the aircraft, and therefore could not accurately assess the load conditions on the seaplane structure, thus affecting the structural safety and the optimization and iteration of structural weight. Summary of the Invention

[0003] Purpose of the invention

[0004] This paper provides a method for calculating the dynamic water load on seaplanes, which can accurately assess the load conditions on the seaplane structure.

[0005] Technical solution

[0006] A method for calculating the dynamic water-landing load of a seaplane is proposed. Based on stiffness distribution and mass distribution data, a dynamic water-landing response analysis model is established. Combined with aircraft parameters, the morphology and characteristics of single waves and regular waves under different sea states are calculated. The incremental load response when the aircraft encounters single waves and regular waves is solved by modal transient response method. The reference load is superimposed to obtain the dynamic water-landing load of the aircraft. Then, considering the safety factor, the extreme values ​​of the ultimate load of each component are selected to form the dynamic water-landing ultimate load envelope of the aircraft.

[0007] The method for calculating the dynamic water-landing load of a seaplane includes the following steps:

[0008] Step 1: Based on stiffness distribution data, mass distribution data, and modeling rules, and combined with the structural model used in aeroelastic analysis, establish a dynamic water-receiving response analysis model;

[0009] Step 2: Combine aircraft parameters, wave parameters, and modeling rules to establish dynamic characteristic models of single waves and regular waves under different sea states;

[0010] Step 3: Use the modal transient response method to solve the response characteristics of the aircraft when encountering a single wave and a regular wave, respectively. Combine the model node and coordinate definition rules to obtain the incremental load of each component.

[0011] Step 4: According to the defined rules, superimpose the incremental loads encountered by single waves and regular waves onto the reference load to solve the dynamic water landing load of the aircraft.

[0012] Step 5: Considering the safety factor, extract the extreme values ​​of the ultimate load of each component to form the dynamic water-landing ultimate load envelope of the aircraft.

[0013] In step 1, the modeling rules are as follows: based on the principle of equivalent structural stiffness and connection stiffness, large component structures (including fuselage, wings, vertical tail, and horizontal tail) are simplified into single-beam structures, and each large component is connected separately using beam elements; large-mass external stores (such as engine nacelles, floats, etc.) are simplified into lumped mass elements and connected to the wings using beam elements. The structural model used should be corrected based on the results of the ground resonance test (GVT) of the entire aircraft.

[0014] In step 2, aircraft parameters include, but are not limited to, aircraft stall speed, aircraft center of gravity and angle of climb at the center of gravity, and aircraft design landing weight. Wave parameters include, but are not limited to, wave height, wavelength, wave speed, frequency, peak load, and load inflection time. These are calculated by determining the characteristic parameters of the waves. The modeling rules are as follows:

[0015] For a single wave, the load growth time is 0.065s to 0.25s, and the peak load calculation formula is as follows:

[0016]

[0017] In the formula, F W1 —Peak load of a single wave, N; W —Aircraft weight, kg; g —Acceleration due to gravity, m / s²; C1 —Empirical coefficient, taken as 0.0348; V S0 — Stall speed of the aircraft with flaps deployed to the corresponding water-touch position, without considering the effect of slipstream, m / s; β — Lift angle at the longitudinal position where the load is applied, °.

[0018] For a regular wave, the load growth time is 0.1s, the number of periods is 3 to 4, and the frequency is calculated using the following formula:

[0019]

[0020] In the formula, f is the encounter frequency (Hz). —Wave speed, m / s; V1 —Aircraft gliding speed on water, m / s; L —Wavelength, m. Wavelength L is determined based on the length-to-height ratio of the ocean waves, with the length-to-height ratio L / h1 / 3 ranging from 20 to 40, and h1 / 3 representing the significant wave height. The frequency is adjusted by modifying parameters such as the length-to-height ratio and significant wave height to match the aircraft's first 5 to 6 elastic frequencies.

[0021] The peak load of a regular wave, taking into account the effects of wave height and wavelength, is calculated using the following formula:

[0022]

[0023] In the formula, F W2 — Peak value of regular wave load, N; h1 — Calculated wave height, m; h0 — Design meaningful wave height, m.

[0024] For a single wave, the duration is 2L / V1; for a regular wave, the duration is 6L / V1.

[0025] In step 3, the dynamic water-landing response analysis model is combined with the dynamic characteristic models of single wave and regular wave. According to the operating conditions and modeling rules, dynamic water-landing response analysis models, main analysis files, and batch files for single wave and regular wave are generated respectively. Combining the model node and coordinate definition rules, the dynamic incremental loads of each component are quickly obtained. The coordinate definition rules are consistent with the overall machine coordinate definition.

[0026] In step 4, the incremental loads of the aircraft encountering single waves and regular waves are added to the corresponding 2 / 3g reference loads to obtain its limiting dynamic water landing load.

[0027] In step 5, the dynamic water load of the aircraft encountering a single wave is taken as 1.5, and the dynamic water load of the aircraft encountering a regular wave is taken as 1.3.

[0028] The beneficial effects of this application are as follows:

[0029] During water landing, the aircraft structure experiences water surface loads and undergoes elastic deformation, resulting in changes in the load distribution across the airframe. This invention provides a method for calculating the dynamic water landing load of seaplanes, considering the dynamic characteristics of waves and the influence of the aircraft's elastic deformation. By using batch processing, the dynamic water landing load of each component is rapidly obtained, improving computational efficiency. This method can accurately assess the load conditions on the seaplane structure, reducing design risks and improving the efficiency of iterative optimization of aircraft structural weight. It provides a basis for aircraft load design and structural strength design. The method provided by this invention can also be used for dynamic response analysis during landing and taxiing, determining the load response characteristics of the aircraft during these conditions and ensuring the safety of the aircraft structure. Attached Figure Description

[0030] Figure 1 This is a diagram of the dynamic water-receiving response analysis model in the example of this invention;

[0031] Figure 2 This is a diagram illustrating the dynamic characteristics of a single wave in an example of this invention.

[0032] Figure 3 This is a diagram illustrating the dynamic characteristics of a regular wave in an example of this invention.

[0033] Figure 4 This is a response history diagram of shear force and bending moment at typical locations of a seaplane encountering a single wave, as shown in the example of this invention.

[0034] Figure 5 This is a response history diagram of shear force and bending moment at typical parts of a seaplane encountering a regular wave, as shown in the example of this invention.

[0035] Figure 6 This is a dynamic water-touch limit load envelope diagram of the bending moment of a typical part of a seaplane in the example of this invention. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments. The following description represents only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] All features, methods, or steps disclosed in this specification may be combined in any way, except for mutually exclusive features and / or steps.

[0038] The present invention provides a method for calculating the dynamic water-landing load of seaplanes. Taking a typical seaplane as an example, it analyzes the response characteristics of the seaplane when encountering a single wave and a regular wave, and calculates the limiting dynamic load of the aircraft to form the dynamic water-landing limit load envelope of the aircraft. The specific implementation process is as follows:

[0039] Step 1: Extract the structural model used for aeroelastic analysis, including nodal coordinates, stiffness elements, mass elements and their property parameters, and name and store them in different sub-files.

[0040] To facilitate subsequent load extraction, structural elements in each part should be numbered and distinguished. The structural model can be adjusted or simplified as needed.

[0041] After obtaining the results of the full-aircraft ground resonance test, the stiffness distribution of the structural model must be corrected using the test results to ensure that the main inherent modal analysis results of the aircraft are consistent with the test results, thereby improving the effectiveness of the structural model.

[0042] Step 2: Combining aircraft parameters, wave parameters, and modeling rules, establish dynamic characteristic models of single waves and regular waves under different sea states, including wave height, wavelength, wave speed, frequency, peak load, and load growth time.

[0043] Step 3: Name the wave models from Step 2 and store them in different sub-files for easy access later.

[0044] Step 4: Generate the main analysis file, call the wave model and structural model sub-files mentioned above to form a dynamic water-landing response analysis model, and generate batch processing executable files according to the type of working condition.

[0045] The main file is also named to facilitate differentiation of wave patterns, loading status, etc.

[0046] Step 5: In the main file of Step 4, define the analysis parameters for each working condition and specify the output requirements, including acceleration output and output of shear force, bending moment, and torque for each part.

[0047] Step 6: Use the batch processing file from Step 4 to call the dynamic water-receiving response analysis model from Step 5 to perform modal and transient response analysis and solve the response history of each part of the body.

[0048] Step 7: Extract the time response history of shear force, bending moment, and torque of each part of the body when encountering a single wave and a regular wave, respectively.

[0049] During response extraction, the machine parts are identified based on the structural unit number, and the analysis conditions are identified based on the naming of the main file and its naming rules.

[0050] Step 8: Considering the influence of the loading status, calculate the 2 / 3g reference load of the aircraft, including shear force, bending moment, and torque.

[0051] For the fuselage, vertical tail, or other similar components, the 2 / 3g reference load can be ignored.

[0052] Step 9: Superimpose the incremental loads of shear force, bending moment, and torque of each part of the machine body extracted in Step 7 onto the reference loads corresponding to Step 8 to determine its dynamic water-sealing limit load.

[0053] Step 10: When encountering a single wave, the safety factor is taken as 1.5; when encountering a regular wave, the safety factor is taken as 1.3. The maximum and minimum values ​​of shear force, bending moment, and torque under all calculation conditions are taken to form the dynamic water landing limit load envelope of the aircraft.

[0054] The dynamic water-landing load calculation method for seaplanes provided by this invention mainly follows modeling and processing rules, combined with an aeroelastic analysis model, to quickly solve the load response of the aircraft when encountering a single wave and a regular wave. Then, the reference load is superimposed to obtain the dynamic water-landing load of the aircraft structure when encountering a single wave and a regular wave, which guides the structural strength design of seaplanes.

[0055] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the dynamic water-landing load of a seaplane, characterized in that, Includes the following steps: Step 1: Extract the structural model used for aeroelastic analysis, including nodal coordinates, stiffness elements, mass elements and their property parameters, and name and store them in different sub-files respectively; By combining aircraft parameters, wave parameters, and modeling rules, dynamic characteristic models of single waves and regular waves under different sea states are established, including wave height, wavelength, wave speed, frequency, peak load, and load growth time. The wave models are named and stored in different sub-files for easy access later. Step 2: Generate the main analysis file, call the wave model and structural model sub-files mentioned above to form a dynamic water-landing response analysis model, and generate batch processing executable files according to the type of working condition; the main file is also named to facilitate the differentiation of wave morphology and loading status. Step 3: Use the modal transient response method to solve the response characteristics of the aircraft when encountering a single wave and a regular wave, respectively. Combine the model node and coordinate definition rules to obtain the incremental load of each component. Step 4: Superimpose the incremental loads encountered by single waves and regular waves with the reference load to solve the dynamic water-landing load of the aircraft. Step 5: Considering the safety factor, extract the extreme values ​​of the ultimate load of each component to form the dynamic water-landing ultimate load envelope of the aircraft; In step 1, the modeling rules are as follows: based on the principle of equivalent structural stiffness and connection stiffness, the large component structure is simplified into a single beam structure, and each large component is connected by beam elements; for large mass external stores, they are simplified into lumped mass elements and connected to the wing using beam elements; the structural model used should be corrected based on the results of the full-aircraft ground resonance test (GVT test). In step 2, aircraft parameters include, but are not limited to, aircraft stall speed, aircraft center of gravity and angle of climb at the center of gravity, and aircraft design water landing weight; wave parameters include, but are not limited to, wave height, wavelength, wave speed, frequency, peak load, and load incubation time. The characteristic parameters of the waves are calculated; the modeling rules are as follows: For a single wave, the load growth time is 0.065s~0.25s, and the peak load calculation formula is as follows: In the formula, Peak load of a single wave, N; W—aircraft weight, kg; g—acceleration due to gravity, m / s²; —Empirical coefficient, taken as 0.0348; —The stall speed of the aircraft with flaps deployed to the corresponding water-touch position, without considering the effects of slipstream, in m / s; —The angle of ascent at the longitudinal position where the load is applied.

2. The method as described in claim 1, characterized in that, For a regular wave, the load growth time is 0.1s, the number of periods is 3~4, and the frequency is calculated using the following formula: In the formula, f is the encounter frequency (Hz). — Wave speed, m / s; —Aircraft gliding speed on water, m / s; L —wavelength, m; Wavelength L is considered according to the length-to-height ratio range of the ocean waves, with the length-to-height ratio L / h1 / 3 taken as 20~40, and h1 / 3 as the meaningful wave height; by adjusting the length-to-height ratio and meaningful wave height parameters, the frequency is made equal to the first 5~6 elastic frequencies of the aircraft. The peak load of a regular wave, taking into account the effects of wave height and wavelength, is calculated using the following formula: （3） In the formula, —Peak load of regular wave, N; — Calculate wave height, in meters; —The design has a wave height of m.

3. The method as described in claim 2, characterized in that, In step 3, the dynamic water-receiving response analysis model is combined with the dynamic characteristic models of single wave and regular wave. According to the working conditions and modeling rules, the dynamic water-receiving response analysis models of single wave and regular wave are generated respectively. Combined with the model node and coordinate definition rules, the dynamic incremental load of each component is quickly obtained. The coordinate definition rules are consistent with the overall machine coordinate definition.

4. The method as described in claim 3, characterized in that, In step 4, the incremental loads of the aircraft encountering single waves and regular waves are added to the corresponding 2 / 3g reference loads to obtain its limiting dynamic water landing load.

5. The method as described in claim 4, characterized in that, In step 5, the dynamic water load of the aircraft encountering a single wave is taken as 1.5, and the dynamic water load of the aircraft encountering a regular wave is taken as 1.3.

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