PDF modeling of a bluff-body stabilized turbulent flame

Abstract

The velocity-turbulent frequency-compositions PDF method combined with the consistent hybrid finite volume (FV)/particle solution algorithm is applied to a bluff-body stabilized turbulent flame. The statistical stationarity is shown and the performance of the PDF method is assessed by comparing the mean fields with the available experimental data. The effects of the model constants C 1 in the turbulence frequency model and C in the mixing model on the numerical solutions are examined and it is found that all the mean fields are very sensitive to the changes in C 1 while only the mixture fraction variance seems to be very sensitive to the changes in C but not the other mean fields. The spatial and bias errors are also examined and it is shown that the hybrid method is second order accurate in space and the bias error is vanishingly small in all the mean fields. The grid size and the number of particles per cell are determined for a 5% error tolerance. The chemistry is described by the simplest possible flamelet/PDF model. Hence the main focus of the paper is on the accurate calculations of the mean flow, turbulence and mixing, which lays the foundation for future work in which the chemistry is described in greater detail.

Scalar PDF and velocity-scalar PDF modelling of the bluff-body stabilised flame HM1 using ILDM

“…The results shown in Fig. 1, 2 and 3 for mean axial velocity, mean radial velocity and fluctuating axial velocity are very similar to the results of [7] or [25,26]. As discussed in [26], good agreement with experimental data is observed within the recirculation zone.…”

“…A convective outlet boundary condition [24] is used in order to avoid reflecting waves. Inlet boundary conditions are specified at cell centres in the same way as done in [25]. Results are obtained on a 160×128 cartesian grid stretched both in axial and radial directions.…”

“…An important observation for the present study is that the very small differences between scalar PDF and velocity-scalar PDF results (due to some differences in mean density) are negligible. (-frequency) results [7,25]. Looking at the mean transport equation, Eq.…”

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

“…The bluff-body stabilised flame has received special attention and been widely studied recently [3,4,8,9,12,13,19,20,28,29]. In addition to its practical interest, the bluff-body flame is a very challenging test for turbulence models as well as chemistry models.…”

“…But it is noteworthy that all models employed in [19] underestimate the persistence of the jet, which means that the minimum value of the velocity on the symmetry axis is underpredicted especially further downstream. The same flame has also been modelled with a conditional moment closure (CMC) model by Kim et al [12,13] and with a coupled radiation/flamelet combustion model by Hossain et al [8], and also with Monte Carlo PDF models by Jenny et al [9] and Muradoglu et al [20] more recently. A similar bluff-body stabilised flame with different geometrical configuration and fuel has also been studied numerically by Wouters et al [28][29][30] using k-model and Reynolds-stress models as well as hybrid finite volume/Monte Carlo PDF model.…”