Generation of turbulent inflow and initial conditions based on multi‐correlated random fields

Fathali, Mani; Klein, Markus; Broeckhoven, Tim; Lacor, Christian; Baelmans, Martine

doi:10.1002/fld.1627

Cited by 29 publications

(9 citation statements)

References 33 publications

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“…This method guarantees spatially correlated velocity fields which can be tuned to reflect real turbulent flow conditions. [51][52][53][54][55] At the side boundaries, the streamwise velocity is assumed equal to U c and the remaining velocity components are equal to zero. Hence, there is no flow through the side boundaries.…”

Section: Simulation Set-up and Forcing Proceduresmentioning

confidence: 99%

Controlled mixing enhancement in turbulent rectangular jets responding to periodically forced inflow conditions

Tyliszczak

Geurts

2015

Journal of Turbulence

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We present numerical studies of active flow control applied to jet flow. We focus on rectangular jets, which are more unstable than their circular counterparts. The higher level of instability is expressed mainly by an increased intensity of mixing of the main flow with its surroundings. We analyse jets with aspect ratio A r = 1, A r = 2 and A r = 3 at Re = 10,000. It is shown that the application of control with a suitable excitation (forcing) at the jet nozzle can amplify the mixing and qualitatively alter the character of the flow. This can result in an increased spreading rate of the jet or even splitting into nearly separate streams. The excitations studied are obtained from a superposition of axial and flapping forcing terms. We consider the effect of varying parameters such as the frequency of the excitations and phase shift between forcing components. The amplitude of the forcing is 10% of the inlet centreline jet velocity and the forcing frequencies correspond to Strouhal numbers in a range St = 0.3-0.7. It is shown that qualitatively different flow regimes and a rich variety of possible flow behaviours can be achieved simply by changing aspect ratio and forcing parameters. The numerical results are obtained applying large eddy simulation in combination with a high-order compact difference code for incompressible flows. The solutions are validated based on experimental data from literature for non-excited jets for A r = 1 at Re = 1.84 × 10 5 and A r = 2 at Re = 1.28 × 10 5 . Both the mean velocities as well as their fluctuations are predicted with good accuracy.

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Section: Simulation Set-up and Forcing Proceduresmentioning

confidence: 99%

Controlled mixing enhancement in turbulent rectangular jets responding to periodically forced inflow conditions

Tyliszczak

Geurts

2015

Journal of Turbulence

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“…37 This method generates synthetic turbulence through a linear combination of uncorrelated random white noise fields such that the resulting velocity field has prescribed turbulent length scales and Reynolds stresses. The method has been extended for periodic boundary conditions and is used to generate two-dimensional periodic turbulent flow fields with the prescribed input Reynolds stresses and length scales.…”

Section: Computational Setup and Conditionsmentioning

confidence: 99%

Two-dimensional direct numerical simulation evaluation of the flame-surface density model for flames developing from an ignition kernel in lean methane/air mixtures under engine conditions

Reddy¹,

Abraham²

2012

Physics of Fluids

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Flame surface density (FSD) models are often used in premixed turbulent combustion modeling to provide closure in large eddy simulations (LES) and Reynolds-averaged simulations. In the present study, data obtained from direct numerical simulation, with reduced chemistry, of flames developing from ignition kernels in lean methane-air mixtures is used to study the accuracy of the FSD modeling terms for LES applications. This study is conducted at elevated temperature and pressure conditions relevant to lean-burn natural gas engines. The closure models for four terms in the FSD transport equation are studied. It is observed that the propagation term as resolved by the LES grid adequately models the actual propagation term without additional sub-grid scale modeling. On the other hand, the closure of the curvature term requires a sub-grid scale model. Two sub-grid scale curvature models are studied and it is seen that there are differences between the actual and the modeled curvature terms during the early evolution of the ignition kernel. The agreement improves as the developing flame approaches a statistically steady-state. The modeling of the sub-grid convection term is analyzed and differences between the actual and the modeled terms are observed to grow during the transient evolution of the ignition kernel. A sub-grid scale model for the closure of the strain rate term shows disagreement at both early and late stages of kernel growth. In general, the sensitivity of the strain rate and curvature models to the filter width is found to be greater than for convection and propagation.

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“…The method that is employed to generate turbulence is the one developed by Fathali et al (2007). This method generates a homogenous decaying turbulent flow field with a specified set of Reynolds stresses and length scales.…”

Section: Computational Setupmentioning

confidence: 99%

Evaluation of scalar dissipation rate sub-models for modeling unsteady reacting jets in engines

Ameen

Abraham

2015

Chemical Engineering Science

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Generation of turbulent inflow and initial conditions based on multi‐correlated random fields

Cited by 29 publications

References 33 publications

Controlled mixing enhancement in turbulent rectangular jets responding to periodically forced inflow conditions

Controlled mixing enhancement in turbulent rectangular jets responding to periodically forced inflow conditions

Two-dimensional direct numerical simulation evaluation of the flame-surface density model for flames developing from an ignition kernel in lean methane/air mixtures under engine conditions

Evaluation of scalar dissipation rate sub-models for modeling unsteady reacting jets in engines

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