Flow separation and side-loads in rocket nozzles

Frey, Manuel; Hagemann, G.

doi:10.2514/6.1999-2815

Cited by 77 publications

(25 citation statements)

References 7 publications

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“…The upper wall shows the Restricted shock separation (RSS) and in the lower wall, the Free shock separation (FSS) is developed.The wall pressure distribution in Fig. 9-a shows a similar nature as the pressure distribution explained by the Vulcaine engine [5]. The black line represents the free shock separation in the lower wall and the red line indicate the restricted shock separation near the upper wall.…”

Section: -4supporting

confidence: 48%

“…In parabolic nozzles, side loads occurred as a result of flow transition from free shock separation (FSS) where the flow detaches from the wall after 110-2 separation to restricted shock separation(RSS) where the flow re-attaches to the wall after separation and vice versa. The cap-shock pattern was identified to be the cause of this transition [4][5][6][7][8]. At low NPR, internal shock interacts with separation induced shock and then, as NPR increases, it interacts with the Mach disk.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Computational Analysis of Bell Nozzles

Baloni¹,

Kumar²,

Channiwala³

2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

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-A Bell type nozzle is most commonly used shape for rocket nozzles. This type of nozzle not only offers significant advantages in terms of size and performance over the conical nozzle but also reduces complexity compared to annular nozzles. The nozzle uses the stagnation temperature (To) and stagnation pressure (Po) generated in the combustion chamber to create thrust by accelerating the combustion gases to a high supersonic velocity. The nozzle expansion ratio was governed by the exit velocity. During flight, the jet flow is ideally expanded and adapted to the surrounding flow only during a short period. The rest of the time, the rocket engine operates in off-design conditions. The present work incorporates 2D axisymmetric flow analysis within the bell type nozzle, at design and off-design conditions, by using computational fluid dynamic software GAMBIT 2.4.6 and FLUENT 6.3.26. A computer code, with the use of the method of characteristics and stream function, is developed to define the higher efficiency nozzle contours for analysis. Simulation has been carried out separately for two different flow conditions i.e. cold and hot. Shear Stress Transport k-ω turbulence model has been chosen for flow analysis. The converged solutions captured asymmetric lambda shock in the nozzles at higher nozzle pressure ratios (NPR) for viscous flows. It also predicted aftershock and flow separation depending upon NPR. The strength of the normal shock, at Mach stem in viscous prediction, generally increases with an increase in NPR. Good agreement is observed between predicted simulation and analytical results in terms of shock structure, shock location, the size of normal shock, aftershock, and asymmetric lambda shocks.

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Section: -4supporting

confidence: 48%

Section: Introductionmentioning

confidence: 99%

Computational Analysis of Bell Nozzles

Baloni¹,

Kumar²,

Channiwala³

2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

View full text Add to dashboard Cite

show abstract

“…Both cases lead to di erent wall pressure distributions that may generate side-loads if the symmetry is not ensured. This phenomenon has been experimentally and numerically observed [8,9]. 3.…”

Section: Interests For the Studymentioning

confidence: 95%

Numerical validation of a stability model for a flexible over-expanded rocket nozzle

Lefrançois

2005

Int. J. Numer. Meth. Fluids

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SUMMARYA numerical approach for the aeroelastical stability of an over-expanded rocket engine is proposed in this paper. The main idea is to o er a better understanding of the repercussions likely to appear from the aeroelastic coupling in terms of side loads that may be responsible for damage e ects on the engine. After a brief description of the stability model issued from previous works (Pekkari's team) and details upon a numerical uid-structure coupling code, comparative calculations are conducted. The stability model is then called into question and a ÿner analysis is proposed to explain its major tendency to over-predict the aeroelastic frequency shift in comparison with numerical coupling results.

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“…The more specialized problem of flow separation and side load generation in rocket nozzles has also attracted significant attention; Östlund & Muhammad-Klingmann (2005) and Östlund et al (2004) provide comprehensive reviews. Original work on in-nozzle shock structure, side load generation and, for example, rocket structural response can be found, for example, in Onofri & Nasuti (1999), Shimizu et al (2008), Frey & Hagemann (1999, 2000, Pekkari (1994), Schwane & Xia (2005) and Wang (2004).…”

Section: Introductionmentioning

confidence: 99%

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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Flow separation and side-loads in rocket nozzles

Cited by 77 publications

References 7 publications

Computational Analysis of Bell Nozzles

Computational Analysis of Bell Nozzles

Numerical validation of a stability model for a flexible over-expanded rocket nozzle

Ascending rockets as macroscopic self-propelled Brownian oscillators

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