Atmospheric Flight Gust Loads Analysis

Kim, M. C.; Kabe, Alvar M.; Lee, S. S.

doi:10.2514/2.3603

Cited by 16 publications

(4 citation statements)

References 17 publications

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“…Один из наиболее важных случаев нагружения -полет РН в плотных слоях атмосферы [1,5]. Влияние неспокойной атмосферы на нагружение РН можно определить статистическими методами [6,7] либо в рамках консервативного подхода, когда учитываются максимально возможные (с некоторым уровнем вероятности) характеристики ветра. В данной статье рассматривается второй подход.…”

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“…Динамическое нагружение в этом случае рассчитывается с помощью специально разработанного программного обеспечения, позволяющего варьировать внешние нагрузки и автоматически обрабатывать результаты расчета.Для сложной конструкции РН уравнения (7) сохраняют свой вид [3]. Стандартная информация вывода программы Nastran может быть базой для получения параметров эквивалентной системы осцилляторов, массы и момента инерции РН, а также для вычисления обобщенных сил, входящих в третье уравнение системы(7).Для формирования левой части третьего уравнения в (7) необходимы значения собственных частот 𝑝𝑝 𝑗𝑗 (Radians) и обобщенных масс 𝑚𝑚 𝑗𝑗 (Generalized mass). Для определения обобщенных сил в правой части третьего уравнения в (7) необходимы функции собственных форм колебаний 𝑓𝑓 𝑗𝑗 (𝑥𝑥) (Eigenvector).…”

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Analytical solution to approximate equations of the launch vehicle motion under the gust action for the dynamic loading calculation

Malykhina

2022

Vestnik Donskogo gosudarstvennogo tehničeskogo universiteta

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Introduction. The launch vehicle (LV) in flight and the dynamic components of loads from the impact of a trapezoidal wind gust are considered. It is proposed to determine the dynamic components of the force factors using analytical solutions for the structure points accelerations. The work objective is to create a technique for selecting the duration of the standard gust, under the influence of which maximum loads are provided in the sections of the LV structure.Materials and Methods. The launch vehicle is presented as an uneven beam. The description of its vibrations is reduced to a system of independent ordinary differential equations that determine the motion of an equivalent system of oscillators. The equation of oscillator vibrations under the action of a trapezoidal pulse load is solved by the overlay method, and it is reduced to the calculation of the Duhamel integral. It is proposed to get the parameters of an equivalent system of oscillators based on the results of the calculation of dynamic characteristics for a finite element LV model in the Nastran program.Results. Analytical relations for the LV structure point accelerations under the action of a trapezoidal wind gust are given. For the beam model, test calculations of accelerations were carried out according to the technique proposed in this paper. These data are compared to the results of finite element modeling. With the help of analytical solutions, dependences are constructed that determine the nature of the change in the magnitude of the bending moment for different sections of the launch vehicle when the duration of the wind gust varies.Discussion and Conclusions. The presented technique provides building an equivalent dynamic model of systems with a large number of degrees of freedom on the example of a LV and obtaining analytical solutions for accelerations of points of a mechanical system under trapezoidal external action. These solutions are applicable for the study of dynamic loads. The analysis results enable to select the duration of the wind gust, at which maximum loads are reached in the sections of the LV structure. Calculations based on the analytical solutions are very economical in terms of time spent. They can be used in design calculations for preliminary assessment of loading.

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Analytical solution to approximate equations of the launch vehicle motion under the gust action for the dynamic loading calculation

Malykhina

2022

Vestnik Donskogo gosudarstvennogo tehničeskogo universiteta

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“…In the 60s and 70s, further progress was made on developing spectral techniques to design aircraft subject to gust encounters [67]. These techniques were based on two main assumptions: the time histories of gust velocities obtained from aircraft may be converted to space fixed 'temporarily frozen' histories and the scale of the turbulence is larger compared to the airplane dimensions.…”

Section: In Flight Gust Identificationmentioning

confidence: 99%

“…In 1999, in the context of space and missile systems, a Monte-Carlo flight gust loads analysis approach was proposed [67]. The procedure uses forcing functions that were derived by extracting the short-duration, turbulent components of measured wind profiles.…”

Section: In Flight Gust Identificationmentioning

confidence: 99%

Numerical and experimental studies of aeroelastic hinged wingtips

Balatti¹

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Aeroelasticity is the science that investigates the mutual interaction between aerody-namic, elastic, and inertia forces and how this affects the static and dynamic structural response. Aeroelastic models can be defined considering different levels of fidelity de-pending on the models’ aim. Gust loads are among the most critical cases an aircraft can encounter, and so mitigating the loads enables the design of a lighter structure, consequently reducing production and fuel consumption costs. Hinged wingtips have shown potential to improve the wing aerodynamic performance while alleviating struc-tural loads. The aim of this work is the numerical and experimental study of aeroelastic wings with hinged wingtips subjected to gusts. Measurements from wind tunnel tests are used to validate the numerical model. Two numerical models, representative of the same aircraft with hinged wingtips subjected to gusts, were considered, a detailed and a simplified one. The latter model, due to its low number of degrees of freedom, was used for wingtip design optimisation. Gust and turbulence events cannot be measured di-rectly, but they can be identified from in-flight measurements. Cubic B-spline functions were used for gust identification considering simulated flight data from the simplified and detailed models. Results have shown the ability of the simplified model to identify the gust and turbulence considering simulated data from the detailed model. To validate the numerical models, a gust generator was designed, installed and commissioned for the Swansea University wind tunnel. Experimental results have shown the difficulty of creating a perfect ‘1-cos’ gust at the desired location. Two techniques to improve the ‘1-cos’ gust were considered. In the first case, the transfer function between the vane rotation and the gust produced at the aircraft model location was identified, and its in-verse was used to calculate the vane rotation. The improvements using this approach are limited by the strong nonlinearity of the aerodynamics. A parametric study of the vane rotation has shown that a more complicated vane rotation function allows ‘1-cos’ gusts at the aircraft model location to be obtained with a mean square error two orders of magnitude smaller than the initial case. An elastic wing able to accommodate different wingtips was manufactured. Three wingtips, namely a fixed wingtip, a hinged wingtip, and a hinged wingtip with a torsional spring at the hinge were considered. Static and dynamic wind tunnel tests have shown the potential of hinged wingtips in reducing wing gust loads. Measured gust loads were used to validate the aeroelastic models.

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Launch Vehicle Operational Environments

Kabe

Kendall

2010

Encyclopedia of Aerospace Engineering

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There are numerous operational environments that a launch vehicle and its payload are subjected to during launch and flight. These include both external environments, such as ground wind loading and atmospheric pressure, as well as self‐induced, such as vibration due to engine thrust. The relative influence of these environments varies significantly during the different phases of flight, necessitating multi‐disciplinary design and analysis approaches. This chapter describes the various environments, as well as the approaches used to establish the viability of launch vehicle and spacecraft designs to survive the launch and flight environments. In addition, day‐of‐launch operational considerations for flying a launch vehicle safely through the atmosphere, while staying within its structural and control system design limits are also discussed.

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Atmospheric Flight Gust Loads Analysis

Cited by 16 publications

References 17 publications

Analytical solution to approximate equations of the launch vehicle motion under the gust action for the dynamic loading calculation

Analytical solution to approximate equations of the launch vehicle motion under the gust action for the dynamic loading calculation

Numerical and experimental studies of aeroelastic hinged wingtips

Launch Vehicle Operational Environments

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