Large eddy simulation of high-density ratio hydrogen jets

2013 ◽  
Author(s):  
F. Bonelli ◽  
A. Viggiano ◽  
V. Magi
Keyword(s):  
Large Eddy Simulation ◽  
Density Ratio ◽  
High Density ◽  
Eddy Simulation ◽  
High Density Ratio ◽  
Large Eddy

scholarly journals Direct numerical simulation and large-eddy simulation of stationary buoyancy-driven turbulence

2009 ◽  
Vol 643 ◽  
pp. 279-308 ◽  
Author(s):  
D. CHUNG ◽  
D. I. PULLIN
Keyword(s):  
Numerical Simulation ◽  
Large Eddy Simulation ◽  
Direct Numerical Simulation ◽  
Density Ratio ◽  
Stationary Flow ◽  
Small Scale ◽  
Scalar Flux ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Active Scalar

We report direct numerical simulation (DNS) and large-eddy simulation (LES) of statistically stationary buoyancy-driven turbulent mixing of an active scalar. We use an adaptation of the fringe-region technique, which continually supplies the flow with unmixed fluids at two opposite faces of a triply periodic domain in the presence of gravity, effectively maintaining an unstably stratified, but statistically stationary flow. We also develop a new method to solve the governing equations, based on the Helmholtz–Hodge decomposition, that guarantees discrete mass conservation regardless of iteration errors. Whilst some statistics were found to be sensitive to the computational box size, we show, from inner-scaled planar spectra, that the small scales exhibit similarity independent of Reynolds number, density ratio and aspect ratio. We also perform LES of the present flow using the stretched-vortex subgrid-scale (SGS) model. The utility of an SGS scalar flux closure for passive scalars is demonstrated in the present active-scalar, stably stratified flow setting. The multi-scale character of the stretched-vortex SGS model is shown to enable extension of some second-order statistics to subgrid scales. Comparisons with DNS velocity spectra and velocity-density cospectra show that both the resolved-scale and SGS-extended components of the LES spectra accurately capture important features of the DNS spectra, including small-scale anisotropy and the shape of the viscous roll-off.

Assessment of Large Eddy Simulation Predictive Capability for Compound Angle Round Film Holes

2015 ◽  
Author(s):  
Gregory Rodebaugh ◽  
Zachary Stratton ◽  
Gregory Laskowski ◽  
Michael Benson
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Density Ratio ◽  
Predictive Ability ◽  
Validation Data ◽  
Injection Angle ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Inflow Turbulence ◽  
Compound Angle

Film cooling holes with a compound angle are commonly used on high pressure turbine components in lieu of axial holes to improve effectiveness or as a result of manufacturing constraints. Whereas large eddy simulation (LES) of axial holes is becoming more common place, assessment of LES predictive ability for compound angle hole has been limited. For this study, the selected compound angle round (CAR) hole configuration has a 30 degree injection angle, a 45 degree compound angle, and a density ratio of 1.5. The geometry, flow conditions, and experimental adiabatic effectiveness validation data are from McClintic et al. [28]. The low free stream Mach number of the experiment puts the flow in the incompressible regime. Two LES solvers are evaluated, Fluent and FDL3Di, on structured meshes with a range of blowing ratios simulated for plenum, inline coolant crossflow, and counter coolant crossflow feed holes. When a steady inlet profile is used for the main flow, LES agreement with the data is poor. The inclusion of a resolved turbulent boundary layer significantly improves the predictive quality for both solvers; consequently, resolved inflow turbulence is a required aspect for CAR hole LES. The remaining differences between the simulations and IR data are partly attributed to the steady coolant inlet profiles used for the counter and inline cross feeds.

scholarly journals Large eddy simulation of high atwood number rayleigh-taylor mixing

2019 ◽  
Vol 128 ◽  
pp. 08001
Author(s):  
Ilyas Yilmaz
Keyword(s):  
Large Eddy Simulation ◽  
Growth Rates ◽  
Density Ratio ◽  
Late Time ◽  
Reynolds Stresses ◽  
Eddy Simulation ◽  
Fully Implicit ◽  
Large Eddy ◽  
Energy Conserving ◽  
Atwood Number

Large eddy simulation of Rayleigh-Taylor instability at high Atwood numbers is performed using recently developed, kinetic energy-conserving, non-dissipative, fully-implicit, finite volume algorithm. The algorithm does not rely on the Boussinesq assumption. It also allows density and viscosity to vary. No interface capturing mechanism is requried. Because of its advanced features, unlike the pure incompressible ones, it does not suffer from the loss of physical accuracy at high Atwood numbers. Many diagnostics including local mole fractions, bubble and spike growth rates, mixing efficiencies, Taylor micro-scales, Reynolds stresses and their anisotropies are computed to analyze the high Atwood number effects. The density ratio dependence for the ratio of spike to bubble heights is also studied. Results show that higher Atwood numbers are characterized by increasing ratio of spike to bubble growth rates, higher speeds of bubble and especially spike fronts, faster development in instability, similarity in late time mixing values, and mixing asymmetry.

Compound Triple Jets Film Cooling Improvements via Velocity and Density Ratios: Large Eddy Simulation

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
R. Farhadi-Azar ◽  
M. Ramezanizadeh ◽  
M. Taeibi-Rahni ◽  
M. Salimi
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Density Ratio ◽  
Cross Flow ◽  
Staggered Grid ◽  
Coolant Fluid ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy

The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged effectiveness). Moreover, the effects of density and velocity differences between the jets and cross-flow and between each of the jets were investigated. The related results showed that any increase in density ratio will increase the penetration of the jet into the cross-flow, but increasing the density ratio also increases the centerline and spanwise average film cooling effectiveness. Increasing the smaller jet velocity ratios, compared with the main jet, significantly improve the cooling effectiveness and uniform coolant distribution over the surface by keeping the main jet coolant fluid very close to the wall.

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