Computational Study of Axisymmetric Off-Design Nozzle Flows

DalBello, T.; Georgiadis, Nicholas J.; Yoder, Dennis A.; Keith, Theo G.

doi:10.2514/6.2004-530

Cited by 18 publications

(10 citation statements)

References 8 publications

(3 reference statements)

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“…With 0:25, Eqs. (24) and (25) show that the diffusion coefficients will become four times smaller than the standard values when the turbulent length scale becomes very large in comparison to the potential core width, and will result in increased turbulent diffusion in such regions.…”

Section: E Variable Diffusion Modelmentioning

confidence: 96%

“…The SST model has been found to provide very good calculations of wall bounded flows even with highly separated regions. One example of this may be found in [25] where the SST model was found to provide the best predictions of several one-and two-equation models in the Wind code for separated nozzle flows. The details of the complete SST model are provided in [18,19], but here we only consider the outer equation set, which is in effect for jet calculations.…”

Section: B Menter Shear Stress Modelmentioning

confidence: 96%

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Evaluation of Modified Two-Equation Turbulence Models for Jet Flow Predictions

2006

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Three two-equation turbulence models developed specifically to improve prediction of jet flowfields are investigated. These models are the Tam-Ganesan k-" formulation, a standard k-" model with modification for heated jets referred to as the PAB temperature correction, and a standard k-" model employing variable diffusion for the k and " equations. Two standard two-equation models are also investigated for comparison with the modified formulations. The standard models are the Chien k-" and Menter shear stress transport formulations. All of the models were investigated for a reference nozzle producing heated and unheated jets at a low acoustic Mach number of 0.5 to avoid complications of large compressibility effects. The primary deficiency of the standard models was the delayed initial jet mixing rate. All of the modified turbulence model formulations provided improved mean flow predictions relative to the standard models. The improved mixing rate enabled by the Tam-Ganesan model and the variable diffusion correction resulted from increased turbulent diffusion enabled by both models. The TamGanesan model and PAB temperature correction improved predictions of mean axial velocities for the heated jet, but did not improve prediction of the calculated turbulent kinetic energy fields.Nomenclature a = speed of sound D = jet exit diameter k = turbulent kinetic energy L t = turbulent length scale M a = acoustic Mach number M t = turbulent Mach number Pr t = turbulent Prandtl number r = distance to centerline S ij = normalized rate-of-strain tensor T g = normalized stagnation temperature gradient T t = stagnation temperature t = time U jet = jet exit velocity u j = velocity tensor X = vortex stretching invariant x j = position tensor " = turbulent dissipation rate " s = solenoidal turbulent dissipation rate = dynamic viscosity = density contribution to the eddy viscosity T = total eddy viscosity, Tam-Ganesan model t = eddy viscosity = density ij = turbulent shear stress tensor = vorticity magnitude ! = specific turbulent dissipation rate ! ij = normalized rotation tensor

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Section: E Variable Diffusion Modelmentioning

confidence: 96%

Section: B Menter Shear Stress Modelmentioning

confidence: 96%

Evaluation of Modified Two-Equation Turbulence Models for Jet Flow Predictions

2006

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“…For a fixed nozzle expansion ratio of 1.5, their experimental study showed the best mixing was achieved when the NPR was in the range of 1.4-1.6. In a numerical study conducted on CDN with Mach number in the range 0.9 < < 1.2 and NPR of 4 and 6, DalBello et al [15] found that the SST − model could match well with experimental measurements.…”

Section: Introductionmentioning

confidence: 96%

Numerical Simulation Of An Over-Expanded Supersonic Nozzle Flow

Qurooni¹,

Vakil²,

Elsaadawy³

et al. 2018

Progress in Canadian Mechanical Engineering

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Flaring in oil and gas production is the controlled burning of unwanted exhaust gases to enhance safety. Obtaining complete combustion and thus eliminating or reducing smoke is critical to meet increasingly strict environmental regulations. To improve flare combustion, gas flares are equipped with air nozzles that introduce extra oxygen and improve mixing in the combustion zone. These nozzles are operated in the subsonic, sonic, or supersonic regimes. In this paper we are concerned with turbulence modeling of the jet flow exiting from a particular convergent-divergent nozzle used in flare systems. The Realizable − and SST − models are used to study the compressible flow within that specific nozzle, which has an exit diameter of 3.38 mm and has convergent and divergent sections that are connected via a throat section with a finite length and constant diameter. The velocity profiles and turbulent kinetic energy predicted by both turbulence models, in the vicinity of the nozzle outlet and along the symmetry axis of the nozzle, are compared for nozzle pressure ratios in the range 1.18 ≤ NPR ≤ 1.78 . It is shown that for ≤ 1, both turbulence models predict nearly identical flow evolution along the nozzle. When the flow becomes supersonic, the shock surface, and consequently nozzle outlet velocity profiles, predicted by the SST − model deviates slightly from the other model. The differences, however, become negligible a couple of diameters downstream of the nozzle outlet. Computed entrainment rate coefficients vary slightly when changing the turbulence model, and this difference remains insignificant with increasing downstream distance.

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“…A 8 = nozzle throat area A 9 = nozzle full expansion area C fg = gross (or uninstalled) thrust coefficient = actual thrust / ideal thrust C T-D = installed thrust coefficient = (actual thrust -drag) / ideal thrust D max = vehicle outer diameter = 19 in. NPR = nozzle pressure ratio = nozzle stagnation pressure / freestream static pressure R max = vehicle outer radius R 9 = nozzle exit radius corresponding to full expansion area y+ = wall normal coordinate θ = nozzle divergence angle…”

Section: Nomenclaturementioning

confidence: 99%

“…NPR = nozzle pressure ratio = nozzle stagnation pressure / freestream static pressure R max = vehicle outer radius R 9 = nozzle exit radius corresponding to full expansion area y+ = wall normal coordinate θ = nozzle divergence angle…”

Section: Nomenclaturementioning

confidence: 99%

Aerodynamic Design and Analysis of High Performance Nozzles for Mach 4 Accelerator Vehicles

Georgiadis

DalBello

Trefny

et al. 2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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The aerodynamic design and performance analysis of two exhaust nozzles considered for use on a vehicle following an accelerating flight profile to a maximum flight speed corresponding to Mach 4.2 is presented. The vehicle operational requirements were set by the Air Vehicle Baseline Study commissioned by the Office of Naval Research. An afterburning engine cycle was assumed in the design and analysis process. The two nozzles investigated here were an axisymmetric convergent-divergent (C-D) nozzle with variable throat and exit area and an isentropic plug nozzle with variable throat area enabled by a translating outer cowl. Computational fluid dynamics was used to assist in the design process and to investigate the installed performance of the two nozzles at flight points from Mach 1.2 to Mach 4.2. For both nozzle configurations, the nozzles could not achieve perfectly expanded exit areas at the highest Mach numbers in order for the nozzle exit area to not exceed the vehicle cross sectional area. At the lower Mach numbers, the installed performance of the C-D nozzle was higher than that of the plug nozzle while at the highest Mach numbers, the performance of the two nozzles was similar. = nozzle exit radius corresponding to full expansion area y+ = wall normal coordinate θ = nozzle divergence angle Nomenclature

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Computational Study of Axisymmetric Off-Design Nozzle Flows

Cited by 18 publications

References 8 publications

Evaluation of Modified Two-Equation Turbulence Models for Jet Flow Predictions

Evaluation of Modified Two-Equation Turbulence Models for Jet Flow Predictions

Numerical Simulation Of An Over-Expanded Supersonic Nozzle Flow

Aerodynamic Design and Analysis of High Performance Nozzles for Mach 4 Accelerator Vehicles

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