Unsteadiness of Flow Separation and End-Effects Regime in a Thrust-Optimized Contour Rocket Nozzle

Nguyen, Anh; Deniau, Hugues; Girard, Steve; Roquefort, T. Alziary de

doi:10.1023/b:appl.0000014927.61427.ad

Cited by 77 publications

(67 citation statements)

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“…Such a condition occurs in TOC type nozzles, in which an internal shock appears near the throat region. The experimental study performed by Nguyen et al [14] on the LEATOC nozzle has shown that during the start-up process of this nozzle at low NPR, there exists FSS §ow regime. This free shock separated §ow suddenly turns into RSS §ow regime when NPR reaches the value of 24.…”

Section: Resultsmentioning

confidence: 99%

“…5c). It has been observed that this FTQP point appears when the NPR is about 24, and experimentally it is shown that in LEATOC nozzle, §ow transition takes place when NPR = 24 [13,14]. One may conclude that the NPR at which this FTQP point occurs is the critical value for the §ow transition and it is called CNPR.…”

Section: Resultsmentioning

confidence: 99%

“…Numerically obtained wall pressure pro¦les at di¨erent NPR during this transition are compared with the available experimental data [14]. Figure 7 shows the plots of the wall pressure (normalized with the inlet stagnation pressure P 0 ) along the nozzle axis (normalized with the throat radius r t ).…”

Section: Resultsmentioning

confidence: 99%

“…Evolution of mean wall pressure in Figure 11 Evolution of mean wall pressure (curves) in comparison with experimental data [14] (signs): 1 ¡ NPR ≈ 25.5; and 2 ¡ NPR ≈ 38 the case of RSS §ow regime is quite complicated due to the reattachment of the supersonic jet. To understand the pressure evolution along the nozzle wall, mean wall pressure at two NPRs is shown in Fig.…”

Section: Evolution Of Wall Pressurementioning

confidence: 98%

“…The LEATOC nozzle has a throat radius r t = 0.01362 m, divergent length L = 0.204 m, and an area ratio ǫ = A exit /A throat of about 30.32. The computational domain used to perform numerical simulations is set according to the experimental setup [14]. It is composed of two zones, i. e., (i) nozzle, and (ii) exterior, as shown in Fig.…”

Section: Description Of the Computationsmentioning

confidence: 99%

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Numerical simulation of shock-induced separated flows in overexpanded rocket nozzles

Shams

Girard

Comte

2012

Progress in Flight Physics

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Flow separation in rocket nozzles is undesirable because of its unsteady and nonsymmetric nature, which leads to dangerous side-loads. At the initial stages of start-up, when a thrust optimized contour (TOC) nozzle operates under overexpanded conditions, free shock separation (FSS) takes place. Under certain conditions, this free separated §ow reattaches back to the nozzle wall and forms restricted shock separation (RSS). The appearance of restricted shock separated §ow depends upon the nozzle contour in a well-de¦ned range of nozzle pressure ratios (NPR) and is characterized by a cap-shock pattern. The §ow transition process from FSS to RSS §ow con¦gurations is a complex phenomenon and has been an area of interest for a few decades now. In the present study, an attempt has been made to understand the formation of the cap-shock pattern and the RSS §ow con¦guration in a thrust optimized contour (TOC) nozzle. The presented research work consists of two parts. In the ¦rst part of the paper, numerical investigation of §ow transition (FSS−→RSS) has been performed to understand the formation of the cap-shock pattern, which is believed to be the main cause for this §ow transition from FSS to RSS. Axisymmetric numerical calculations on a wide range of NPRs (15 25) are performed to reproduce the forward transition process and are found to be in good agreement with the experiments. In the second part, some light has been shed on various aspects of RSS §ow regime. Three-dimensional (3D) numerical simulations have been performed on a wide range of NPRs, i. e., 25.0, 30.0, 38.0, 41.0, and 46.0. Detailed analysis of these numerical results allows examining the evolution of the separation point and the cap-shock pattern with respect to the NPR. Furthermore, some insights based on the axial momentum along the nozzle axis and radial momentum distributions across the quadruple point are given.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Evolution Of Wall Pressurementioning

confidence: 98%

Section: Description Of the Computationsmentioning

confidence: 99%

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