Characterization of Side Load Phenomena Using Measurement of Fluid/Structure Interaction

Brown, A.; Ruf, Joseph H.; Reed, Darren K.; D'Agostino, Mark; Keanini, Russell G.; Mcconnaughey, P. K.

doi:10.2514/6.2002-3999

Cited by 21 publications

(14 citation statements)

References 4 publications

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“…Once the flow reattaches, the flow expands and the pressure decreases up to the second separation point. [12] suggested that additional sources of side load disturbances are produced by fluctuating wall pressures in the separated regions of the nozzle, as well as aeroelastic fluid structure coupling; the latter was studied experimentally by Brown et al [13]. Numerical models have also been developed to provide more insight into the origin of side loads during the full duty cycle of the engine.…”

mentioning

confidence: 99%

Wall Pressure Unsteadiness and Side Loads in Overexpanded Rocket Nozzles

Baars

Tinney²,

Ruf³

et al. 2012

AIAA Journal

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Surveys of both the static and dynamic wall pressure signatures on the interior surface of a sub-scale, cold-flow and thrust optimized parabolic nozzle are conducted during fixed nozzle pressure ratios corresponding to FSS and RSS states. The motive is to develop a better understanding for the sources of off-axis loads during the transient start-up of overexpanded rocket nozzles. During FSS state, pressure spectra reveal frequency content resembling SWTBLI. Presumably, when the internal flow is in RSS state, separation bubbles are trapped by shocks and expansion waves; interactions between the separated flow regions and the waves produce asymmetric pressuredistributions. An analysis of the azimuthal modes reveals how the breathing mode encompasses most of the resolved energy and that the side load inducing mode is coherent with the response moment measured by strain gauges mounted upstream of the nozzle on a flexible tube. Finally, the unsteady pressure is locally more energetic during RSS, albeit direct measurements of the response moments indicate higher side load activity when in FSS state. It is postulated that these discrepancies are attributed to cancellation effects between annular separation bubbles.

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mentioning

confidence: 99%

Wall Pressure Unsteadiness and Side Loads in Overexpanded Rocket Nozzles

Baars

Tinney²,

Ruf³

et al. 2012

AIAA Journal

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“…As an aside, we note that rocket body vibrations, particularly those involving the nozzle or its attachments, can play a significant role in nozzle side load generation (Brown et al 2002). Because side loads, in turn, represent an important dynamical feature, the impact of rocket vibration on ascent constitutes an important open question.…”

Section: Analogue Self-propelled Brownian Oscillator (A) Overview Of mentioning

confidence: 99%

“…In large engines, side loads can reach extreme magnitudes, for example, of the order of 250 000 pounds in Apollo Saturn V rockets (Brown et al 2002).…”

Section: Introductionmentioning

confidence: 99%

“…This objective is often pursued using high area ratio, reduced length nozzles and/or optimized nozzle designs (Östlund & Muhammad-Klingmann 2005). While modern nozzles typically provide high in-vacuum performance, during low altitude flight, unsteady detachment of the over-expanded supersonic flow within the nozzle can lead to the generation of often dangerous nozzle side loads (Summerfield et al 1954;Sunley & Ferriman 1964;Nave & Coffey 1973;Dumnov 1996;Alziary 2001;Brown et al 2002;Östlund et al 2004;Östlund & Muhammad-Klingmann 2005).…”

Section: Introductionmentioning

confidence: 99%

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Ascending rockets as macroscopic self-propelled Brownian oscillators

2012

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High-fidelity numerical experiments and theoretical modelling are used to study the dynamics of a sounding-rocket-scale rocket, subject to altitude-dependent random wind and nozzle side loads and deterministic aerodynamic loading. This paper completes a series of studies that showed that Ornstein-Uhlenbeck (OU) rotational dynamics arise when random nozzle side loads dominate wind and aerodynamic loading. In contrast to the earlier work, this paper elucidates that under conditions where aerodynamic, wind and nozzle side loads are comparable, the rocket behaves as stochastic Brownian oscillator. The Brownian oscillator model allows straightforward interpretation of the complex rotational dynamics observed: three dynamical regimeseach characterized by differing balances between nozzle-side-load-induced torques, spring-like aerodynamic torques and mass flux damping torques-characterize rocket ascent. Further, the paper illuminates that in the limit where wind and aerodynamic loads are small, random mass flux variations exponentially amplify side-load-induced rotational stochasticity. In this practical limit, pitch/yaw dynamics are described by a randomly damped OU process; an exact solution of the associated Fokker-Planck equation can be obtained and used to compute, e.g. time-dependent pitch/yaw rate means and variances.

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“…This problem has been well studied through experiments as well as computations. The unsteady separation phenomenon inside the nozzle can lead to steady/unsteady forcing of the thrusting nozzle, as well as associated mechanisms due to fluid-structure interactions [1][2][3][4][5]. The presence of such unsteady side loads can also result in adverse control systems of the vehicle in pitch, roll, and yaw [6].…”

Section: Introductionmentioning

confidence: 99%