The Calculation of Three-Dimensional Turbulent Free Jets

McGuirk, James J.; Rodi, William

doi:10.1007/978-3-642-46395-2_6

Cited by 56 publications

(39 citation statements)

References 13 publications

(23 reference statements)

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“…In order to fix this deficiency, some modifications for the model constants of the dissipation equation have been proposed as described in detail in [3]. In several modifications, the constants C 1 and C 2 (the constants in the dissipation equation) are made as a simple or complicated function of the velocity decay rate and jet width [18,23]. However despite a number of complicated modifications, Dally et al [3] have shown that, with the use of constant value of C 1 = 1.6 instead of the standard value of 1.44 a very significant improvement was obtained in the calculation results for the round jets, better than any other complicated modifications (for convenience here we denote this modification of LRR-IP model as BM-M1, for "basic model modification 1").…”

Section: Modification Of the Lrr-ip Model For The Bluff-body Flowmentioning

confidence: 99%

Numerical Investigation of a Bluff-Body Stabilised Nonpremixed Flame with Differential Reynolds-Stress Models

Naud

Roekaerts

2003

Flow, Turbulence and Combustion

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Abstract.A numerical investigation of a bluff-body stabilised nonpremixed flame, and the corresponding nonreacting flow, has been performed with differential Reynolds-stress models (DRSMs). The equilibrium chemistry model is employed and an assumed-shape beta function PDF approach is used to represent the interaction between turbulence and chemistry. The Reynolds flux of the mixture fraction is obtained from a transport equation, hence a full second moment closure is used. To clarify the applicability of the existing DRSMs in this complex flame, several models, including LRR-IP model, JM model, SSG model as well as a modified LRR-IP model, have been applied and evaluated. The existing models, with default values of the coefficients, cannot provide overall satisfactory predictions for this challenging test case. The standard LRR-IP model over predicts the centreline velocity decay rate, and therefore does not perform satisfactory. The modified LRR-IP model, with model constant C 1 = 1.6 instead of the standard value 1.44 (here named BM-M1), gives better results for the mean velocity. However in the nonreacting case this does not lead to improvement in predicting rms fluctuating velocities especially downstream of the recirculation zone. Motivated by the need to improve the prediction, a new modification of the LRR-IP model is proposed (BM-M2), with model constant C 2 = 0.7 in the pressure strain correlation rather than the standard value 0.6. With the new modified model, a very significant improvement of the prediction of flow field is obtained in the nonreacting case, whereas in the reacting case the prediction of the flow field is of the same overall quality as with BM-M1. This shows that some DRSMs have different behaviour in the nonreacting case and the reacting case. In the reacting case also the mean and variance of mixture fraction are considered and it is found that the best results are obtained with the BM-M1 model, with SSG as second best. Combining the results for flow field and mixture fraction field it is concluded that the BM-M1 model is recommended for further studies of this bluff-body stabilised flame. Grid independence of the result is demonstrated.

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Section: Modification Of the Lrr-ip Model For The Bluff-body Flowmentioning

confidence: 99%

Numerical Investigation of a Bluff-Body Stabilised Nonpremixed Flame with Differential Reynolds-Stress Models

Naud

Roekaerts

2003

Flow, Turbulence and Combustion

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“…Properties for jets that are not issuing from circular cross-section apertures are not so well documented due to the smaller number of studies of such jets [1]. Simulations of this type of jet using computational uid dynamics (CFD) have also appeared to be di cult [2]. One example where these jets are present is in the o shore oil and gas industry.…”

Section: Introductionmentioning

confidence: 99%

Simulations of high‐aspect‐ratio jets

Holdo̸

Simpson

2002

Numerical Methods in Fluids

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???The definitive version is available at www3.interscience.wiley.com '. Copyright John Wiley and Sons Ltd. DOI: 10.1002/fld.340 [Full text of this article is not available in the UHRA]There are many practical situations when jets are emanating from non-axis-symmetric apertures, yet numerical simulations of such three-dimensional jets are scarce and most of them have failed to reproduce some of the unique flow features. Examples of this type of jets are gas leaks from flanges. These can be treated as jets issuing from high aspect ratio rectangular orifices. The present work consists of a series of large eddy simulations typifying such jets using different inflow boundary conditions. Good agreement with available experiments was observed provided appropriate boundary conditions were present. A discrete method for formulating turbulence data with a known energy spectrum for an inflow condition is outlined and evaluated with three other inflow conditions???a steady uniform profile, a steady parabolic profile and pseudo-random noise. The implementation of the new inlet condition results in a more realistic centreline velocity decay where the division between the end of the potential core region and the start of the characteristic decay region is clearly visible. Large velocity oscillations are also observed in the final quarter of the domain (15???20 slot widths downstream). Similar oscillations have been observed in real jets. Off-centre mean velocity peaks are present along the major axis 10 slot widths downstream of the exit in all the simulations. The peaks are approximately 3% of the centreline velocity. The presence of the off-centre peaks are proved to be independent of jet inflow boundary conditions and an explanation for the mechanism causing the off-centre peaks is given

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“…Boundary conditions for both cases are selected such that boundaries except nozzle exit and nozzle wall have zero gradients for pressure and velocity [24]. In addition, the choked nozzle exit plane has pressure, temperature, velocity, and flow angle specified as: …”

Section: Boundary Conditionsmentioning

confidence: 99%

Passive Control of Supersonic Rectangular Jets through Boundary Layer Swirl

Han

Taghavi

Farokhi

2013

Int. J. Turbo Jet-Engines

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Mixing characteristics of under-expanded supersonic jets emerging from plane and notched rectangular nozzles are computationally studied using nozzle exit boundary layer swirl as a mean of passive flow control. The coupling of the rectangular jet instability modes, such as flapping, and the swirl is investigated. A threedimensional unsteady Reynolds-Averaged Navier-Stokes (RANS) code with shock adaptive grids is utilized. For plane rectangular nozzle with boundary layer swirl, the flapping and spanwise oscillations are captured in the jet's small and large dimensions at twice the frequencies of the nozzles without swirl. A symmetrical oscillatory mode is also observed in the jet with double the frequency of spanwise oscillation mode. For the notched rectangular nozzle with boundary layer swirl, the flapping oscillation in the small jet dimension and the spanwise oscillation in the large jet dimension are observed at the same frequency as those without boundary layer swirl. The mass flow rates in jets at 11 and 8 nozzle heights downstream of the nozzles increased by nearly 25% and 41% for the plane and notched rectangular nozzles respectively, due to swirl. The axial gross thrust penalty due to induced swirl was 5.1% for the plane and 4.9% for the notched rectangular nozzle.

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The Calculation of Three-Dimensional Turbulent Free Jets

Cited by 56 publications

References 13 publications

Numerical Investigation of a Bluff-Body Stabilised Nonpremixed Flame with Differential Reynolds-Stress Models

Numerical Investigation of a Bluff-Body Stabilised Nonpremixed Flame with Differential Reynolds-Stress Models

Simulations of high‐aspect‐ratio jets

Passive Control of Supersonic Rectangular Jets through Boundary Layer Swirl

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