Modeling of turbulent mixing in opposed jet configuration: One-dimensional Monte Carlo probability density function simulation

Simulations of turbulent CH 4 -air counterflow flames are presented, obtained in terms of zero and two-dimensional first-order Conditional Moment Closure (CMC) to study the flame structure and extinction limits. The CMC equation with detailed chemistry is solved without the need for operator splitting, while the accompanying flow field is determined using a commercial CFD software employing a Reynolds stress turbulence model and additional transport equations for the turbulent scalar flux and for the mean scalar dissipation rate. Two detailed chemical mechanisms and different conditional scalar dissipation rate models have been examined and small differences were found.The first-order CMC captures the overall structure of the counterflow flame accurately for the unconditional averages. The calculated conditional averages behave as if the scalar dissipation rate were under-predicted, although a comparison with measurement of the conditional scalar dissipation rate is reasonable. The calculated extinction velocity is found to be much higher than the experimental value, but the trend of increasing extinction velocity with air dilution of the fuel stream is captured well. The discrepancies with the data are mostly attributed to the neglect of conditional fluctuations.

Section: Flow Fieldsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Simulations of Turbulent Non-Premixed Counterflow Flames with First-Order Conditional Moment Closure

Kim

Mastorakos

2006

“…2a for the lowest Reynolds-number (5,000, TOJC) and in Fig. 2b for the highest Reynolds-number (7,200,TOJE). The images give an impression of the development and break-up of the central jet.…”

Section: Particle Image Velocimetry (Piv)mentioning

confidence: 92%

“…Another series of simultaneous measurements of the flow-field and the flame position provides information on flame turbulence interactions [2] with additional time resolved measurements of the extinction process caused by the turbulent flowfield [4]. This burner has also been investigated by numerical simulation [7,10,14]. Geyer et al [10] and Kempf et al [14] have performed Large Eddy Simulations (LES) of the case, a technique that resolves the large energy-containing scales (eddies) directly, by integrating the underlying conservation equations, while modeling the effect of the small scales.…”

Section: Introductionmentioning

confidence: 99%

In-Nozzle Measurements of a Turbulent Opposed Jet Using PIV

Böhm

Stein

Kempf

et al. 2010

Turbulent opposed jet burners are an excellent test case for combustion research and model development due to the burners' compactness, relative simplicity, and the good optical access they provide. The flow-field in the flame region depends strongly on the turbulence generation inside the nozzles, so that realistic flow simulations can only be achieved if the flow inside the nozzles is represented correctly, which must be verified by comparison to suitable experimental data. This paper presents detailed particle image velocimetry (PIV) measurements of the flow issuing from the turbulence generating plates (TGP) inside a glass nozzle. The resulting data is analyzed in terms of first and second moments, time-series, frequency spectra and phase averages. The measurements show how individual high velocity jets emerging from the TGP interact and recirculation zones are formed behind the solid parts of the TGP. Vortex shedding is observed in the jet's shear layer were high levels of turbulent kinetic energy are generated. Time series measurements revealed periodic pulsations of the individual jets and implied a coupling between adjacent jets. The peak frequencies were found to be a function of the Reynoldsnumber.Keywords LES inflow data · High-speed particle image velocimetry · Large eddy simulation · Turbulent opposed jet burner · Turbulence generating plate · Wind-tunnel turbulence Electronic supplementary material The online version of this article (

“…A number of numerical studies, mostly based on one-and two-dimensional simplifications of turbulent stagnation point flows in the RANS framework, have been published by Craft et al [7], Dianat et al [8], Lindstedt and Vaos [26,27], Eckstein et al [9], Chou et al [5], Korusoy and Whitelaw [22] and others. Generally, mean quantities were predicted more accurately than fluctuating components and Reynolds stress turbulence models yielded better results than eddy viscosity approaches.…”

Section: Introductionmentioning

confidence: 99%

Highly-resolved LES and PIV Analysis of Isothermal Turbulent Opposed Jets for Combustion Applications

Stein

Böhm

Dreizler

et al. 2010

Turbulent opposed jet (TOJ) burners are an interesting test case for fundamental combustion research and a good benchmark for the available modelling approaches. However, these opposed jet flames strongly depend on the turbulence generation inside the nozzle, which is usually achieved through a perforated plate upstream of the nozzle exit. The present work investigates the flow from these perforated plates and the subsequent turbulence generation in great detail. We present results from highly-resolved large eddy simulations (LES) of the in-nozzle flow in turbulent opposed jets alongside state-of-the-art particle image velocimetry (PIV) at standard and high repetition rates taken inside a glass nozzle. The in-nozzle PIV data provides the LES inflow conditions with unprecedented detail, which are used to follow the initial jet development behaviour known from PIV, before jet coalescence, turbulence production and decay further downstream in the nozzles are successfully predicted. In regions where the PIV experiment suffers from inherent limitations like reflections and the velocity bias, the LES data is available to still obtain a detailed picture of the flow. The sensitivity of the simulations to various physical and numerical parameters is discussed in detail. Results from LES and PIV are compared Flow Turbulence Combust (2011) 87:425-447 qualitatively and quantitatively in terms of first and second moments of velocity, temporal autocorrelations, and energy density spectra. Significant deviations are found in the frequency (20%) and strength of vortex shedding from the inlet plane only, whereas the qualitative and quantitative agreement between simulation and experiment is otherwise excellent throughout, implying that a successful large eddy simulation of a turbulent opposed jet can be performed in a domain that includes the perforated plates.