Statistical Analysis of Atmospheric Flight Gust Loads Analysis Data

Clark, J. B.; Kim, M. C.; Kabe, Alvar M.

doi:10.2514/2.3602

Cited by 9 publications

(4 citation statements)

References 8 publications

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“…(14) are necessary to develop empirical gust loads analysis forcing functions 2 " and to establish loads due to atmospheric turbulence. 21 ' 22 Since the gust loads analysis accounts for the turbulent components of the winds statistically, and the average boundary between the slowly-varying and turbulent components of the wind can now be defined for the ER and WR ranges, there is the possibility of retaining in the day-of-launch loads analyses only those components of the winds that are slowly varying. 21 It is suggested that, to conservatively bracket the variation of this function, the values obtained with Eq.…”

Section: Potential Usesmentioning

confidence: 99%

Identifying Slowly-Varying and Turbulent Wind Features for Flight Loads Analyses

Spiekermann¹,

Sako²,

Kabe³

1999

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services, Directorate for Information Operations and Reports. 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and A methodology developed to determine the spectral boundary between the slowly-varying components and the more rapidly varying, or turbulent components, of measured wind profiles is presented. Pairs of measured wind velocity versus altitude profiles from the Eastern and Western launch ranges of the United States were used to establish the vertical wavelengths which could no longer be considered slowly varying over discrete time intervals. Analyses were performed for wind pairs that were 30, 60, 90, and 120 minutes apart. The wavelength boundary between slowly-varying and turbulent wind features as a function of time interval is presented. The results of this work make it now possible to identify and extract the slowly-varying and/or turbulent wind features, as needed for a specific day-of-launch flight loads analysis, for these two launch facilities. SUBJECT TERMS AbstractA methodology is developed to determine the spectral boundary between wind features that can be considered slowly varying, and the more rapidly-varying, or turbulent, features of measured wind profiles. Pairs of measured wind velocity versus altitude profiles from the Eastern and Western launch ranges of the United States were used to establish the vertical wavelengths which could no longer be considered slowly varying over discrete time intervals. Analyses were performed for wind pairs that were 30, 60, 90 and 120 minutes apart. The wavelength boundary between slowly-varying and turbulent wind features as a function of time interval is presented. The results of this work make it possible to identify and extract the slowly-varying and turbulent wind features at a particular launch site.

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Section: Potential Usesmentioning

confidence: 99%

Identifying Slowly-Varying and Turbulent Wind Features for Flight Loads Analyses

Spiekermann¹,

Sako²,

Kabe³

1999

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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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“…Дальнейшее увеличение значений θ не влияет на величины максимальных значений изгибающего момента. Для зон 4-6 максимум значения изгибающего момента оказывается локальным и располагается в зоне значений θ, близких к величине половины периода 𝑇𝑇 1 первого тона колебаний РН.Полученные результаты полностью соответствуют итогам конечноэлементного моделирования, проведенного ранее6 .Таким образом, для получения максимальных значений изгибающего момента в сечениях рассматриваемой РН необходим динамический анализ поведения конструкции с внешним воздействием в виде порыва ветра, продолжительность которого определяется параметром θ, близким по значению к половине периода первого тона колебаний РН.Обсуждение и заключения. С помощью метода наложений получены аналитические решения, описывающие движение системы с одной степенью свободы, на которую влияют сила трения и внешняя сила, меняющаяся по трапецеидальному закону.…”

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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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“…These segments are then used in Monte Carlo load analyses (Refs. 18,20) to define gust loads that are a function of both altitude and time remaining to launch.…”

Section: Turbulence/gust Loadsmentioning

confidence: 99%

A Refined and Less Conservative Day-of-Launch Atmospheric Flight Loads Analysis Approach

Kabe¹,

Spiekermann²,

Kim³

et al. 1999

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Statistical Analysis of Atmospheric Flight Gust Loads Analysis Data

Cited by 9 publications

References 8 publications

Identifying Slowly-Varying and Turbulent Wind Features for Flight Loads Analyses

Identifying Slowly-Varying and Turbulent Wind Features for Flight Loads Analyses

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

A Refined and Less Conservative Day-of-Launch Atmospheric Flight Loads Analysis Approach

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