Turbulence Modeling Effects on Calculation of Lobed Nozzle Flowfields

Georgiadis, Nicholas J.; Rumsey, Christopher L.; Yoder, Dennis A.; Zaman, K. B. M. Q.

doi:10.2514/1.17160

Cited by 26 publications

(16 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Engblom et al [6] investigated a series of cold and hot single flow subsonic nozzle flows including a baseline round nozzle and several chevron nozzles, and a similar trend in the computations indicated much slower mixing towards the nozzle centerline than observed in experiments. Georgiadis et al [4] investigated a reference subsonic lobed nozzle flow with linear two-equation and explicit algebraic stress turbulence models, and found similar trends. Additionally, far downstream of the end of the jet potential core, it had been generally found that the computed far-field mixing rate became too high.…”

Section: Introductionsupporting

confidence: 51%

“…In recent years, nonlinear explicit algebraic stress model (EASM) formulations have been explored for improving the capability to predict turbulent jet flowfields with significant turbulent anisotropy [1][2][3][4]. However, EASMs use an underlying two-equation approach and are subject to the same deficiencies as the linear two-equation models.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

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

2006

Self Cite

View full text Add to dashboard Cite

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

show abstract

Section: Introductionsupporting

confidence: 51%

Section: Introductionmentioning

confidence: 98%

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

2006

Self Cite

View full text Add to dashboard Cite

show abstract

“…First, a RANS calculation was carried out with the Spalart-Allmaras turbulence model [28,29], which is widely used in complex compressible flows [38,39]. As the streamwise vorticity plays a role in the present flows, the rotational correction of this model [40] was used to limit excessive turbulent diffusion in the vortex cores.…”

Section: Resultsmentioning

confidence: 99%

Zonal Detached Eddy Simulation of a Controlled Propulsive Jet

2007

View full text Add to dashboard Cite

This paper presents zonal detached-eddy simulation of a round underexpanded sonic jet exhausting from a realistic aircraft afterbody and controlled by four radial injections. The comparison with a former experiment proves the capability of zonal detached-eddy simulation to reproduce mean flow induced by the complex interaction between the compressible waves and the turbulent jet shear layer. However, the very near-field jet structure indicates that the shear-layer transition to a fully turbulent state is delayed. Therefore, a modification of the characteristic length scale used in the modeling is proposed which is shown to improve the prediction of the shear-layer growth. The control injectors are aimed to enhance jet mixing. Experiment indicated the efficiency of this additional device but also expressed the need for more data to get a deeper and more complete insight into the whole flowfield. Both spatial and temporal information are provided by zonal detached-eddy simulation which is then a good candidate. This method is shown to correctly simulate streamwise vortices generated by secondary injections, their action in jet distortion, as well as their subsequent decay. Finally, computational results allow us to evaluate the action of the hypermixer on turbulent activity and its consequences on jet dilution. Nomenclature a = critical speed of the primary flow D = nozzle throat diameter d = distance to the closest wall k = turbulent kinetic energy k = nondimensionalized turbulent kinetic energy integrated in jet cross sections Y; Z M = Mach number N = normalized vorticity vector p = pressure hp i jp i0 i = nondimensionalized stagnation pressure averaged in the jet volume Pr = Prandtl number Q = mass flow rate S ij = components of the strain tensor T = temperature U = longitudinal velocity u = velocity vector V c = core volume V j = jet volume X, Y, Z = Cartesian coordinates linked to the scale model X, R, = cylindrical coordinates x, y, z = local coordinates linked to the grid cells = mesh characteristic length max = based on the maximum cell size vol = based on the cell volume ! = based on the vorticity x, y, z = cell sizes in the local coordinate system = small parameter = small vector = molecular dynamic viscosity t = turbulent dynamic viscosity t = turbulent kinematic viscosity = density d ij = components of the deviatoric part of the Reynolds-averaged Navier-Stokes/subgridscale stress tensor R xr , RM xr , RR xr = total, modeled, and resolved Reynolds shear stress in the plane (X;R) X = normalized streamwise vorticity ! xD=2a ! = vorticity vector r u Subscripts i = isentropic stagnation value 0 = ambient flow value 1 = primary flow value 2 = ventilation flow value 3 = control flow value IntroductionA ERONAUTICAL applications and more generally many engineering issues are concerned with high Mach and Reynolds-number flows featuring attached and detached boundary layers in internal as well as external parts. Experiment has proved to be essential in the past while computational tools were still not mature, and ...

show abstract

“…The high resolution upwind discrete scheme was used on both convective and diffusive terms. According to the recommendation of paper, [35][36][37][38] turbulence closure was achieved through the shear stress transport (SST) k-! two-equation turbulence model, since it was capable of modeling both wall-bounded and free shear flows.…”

Section: Computational Modelingmentioning

confidence: 99%

Numerical research on the mixing mechanism of lobed mixer with inlet swirl in linear radial distribution

Lei

Zhang

Zhu

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part A:

View full text Add to dashboard Cite

A detailed numerical simulation is presented to investigate the effects of inlet swirl and its radial distribution on the mixing mechanisms of a turbofan mixer with 12 lobes, by using the commercial ANSYS CFX solver and k-! SST model. The core-to-bypass temperature ratio and pressure ratio were set to 2.59 and 0.97, respectively, giving the Mach number of 0.66 and bypass ratio of 2.65 at mixing nozzle outlet. In the core inlet, the swirl angle was raised from 0 to 30 in a uniform or linear radial distribution manner. The inlet swirl and its radial gradient did enhance the development, interaction, and dissipation of the vortices downstream of lobed mixer, resulting in accelerating the lobed jet mixing. When the inlet swirl was less than 20 , the total pressure and thrust loss increments of lobed jet were acceptable and no more than 0.26% and 1.57%, respectively, compared with the baseline case. The results also showed that the three-dimensional separation bubble on center-body and the backflows along jet axis at the rail of center-body, resulting from the swirling flow between lobes' trough and center-body, were the dominant sources of total pressure and thrust losses for all cases with inlet swirl. And, reasonable radial distribution of inlet swirl could inhibit the aforementioned 3D separation and backflow, and thus limited the increment of jet mixing loss favorably.

show abstract

Turbulence Modeling Effects on Calculation of Lobed Nozzle Flowfields

Cited by 26 publications

References 25 publications

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

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

Zonal Detached Eddy Simulation of a Controlled Propulsive Jet

Numerical research on the mixing mechanism of lobed mixer with inlet swirl in linear radial distribution

Contact Info

Product

Resources

About