A comparative study of variant turbulence modeling in the physical behaviors of diesel spray combustion

Abstract

In this research, the performance of non-linear k-ε turbulence model in resolving the time delay between mean flow changes and its proportionate turbulent dissipation rate adjustment was investigated. For this purpose, the ability of Launder-Spalding linear, Suga non-linear, Yakhot RNG and Rietz modified RNG k-ε models are compared in the estimation of axial mean velocity profile and turbulent integral length scale evolution during engine compression stroke. Computed results showed that even though all the models can predict the acceptable results for velocity profile, for turbulent integral length scale curve, non-linear model is in a good agreement with modified RNG model prediction that depicts correspondence with experimental reported data, while other models show a different unrealistic behaviors. Also after combustion starts and piston is expanding, non-linear model can predicts actual manner for integral length scale while linear one cannot. It is concluded that, physical behavior of turbulence models characteristics should be ascertained before being successfully applied to simulate complex flow fields like internal combustion engines

Numerical investigation on cooling performance of Ranque-Hilsch vortex tube

“…When such models are applied to a range of flows, the overall performance may be inferior to the standard model [34]. Previous applications of the original RNG k-e model showed an unrealistic prediction of the mixing and turbulent viscosity which indicates a need to modify the model's coefficients for a particular physics of flow [35,36]. Figure 12 illustrates the stream-lines within the RHVT as predicted by the Standard k-e model.…”

Application of different turbulence models for improving construction of small-scale boiler fired by solid fuel

“…Turbulence modeling through the CFD commonly includes the use of two concepts, Eddy viscosity and Eddy diffusivity concept [9,10,[12][13][14][15]. Bousinesq's hypothesis is the base of Eddy viscosity concept and it introduces assumption that Reynolds turbulent stress is proportional to velocity gradients.…”

“…(1) Standard k-ε turbulence model [9,[13][14][15][16][17][18] Standard k-ε turbulence model was introduced for modeling of fully developed turbulent flows (corresponding to high Re numbers) where the value of molecular viscosity is neglected:…”

“…As the turbulence is one of the key components defining combustion process in stoves and small-scale boilers, the commercial CFD packages are widely used for combustion modeling through defining reactive fluid flows together with the stoichiometry and chemical reactions [5,8,9]. First step in this complicated algorithm is defining velocity field in considered geometry taking into account turbulence intensity and mass continuity.…”

Numerical Droplet Cooling Simulation of Methane Conversion into Syngas Products

“…В связи с важностью технического применения капельно-го охлаждения в мире выполнен большой объем экспериментальных и теоретических работ [2][3][4][5][6][7][8][9]. Однако при записи уравнений баланса импульса энергии и массы в некоторых работах имеются погрешно-сти [10].…”