<i>A priori</i>assessment of the subgrid scale viscous/scalar dissipation closures in compressible turbulence

Vaghefi, Navid S.; Nik, Mehdi B.; Pisciuneri, Patrick; Madnia, C. K.

doi:10.1080/14685248.2013.854901

Cited by 15 publications

(12 citation statements)

References 40 publications

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“…In another work, Dahm (2005) has proposed that the effects of heat release on the growth rate of exothermic low compressible reacting mixing layers can be characterized by finding an extended density ratio and using this density ratio in the equations obtained for the non-reacting mixing layers. Furthermore, several experimental and computational studies including the non-reacting cases of our previous work (Papamoschou & Roshko 1988;Samimy & Elliott 1990;Pantano & Sarkar 2002;Hadjadj et al 2012;Vaghefi et al 2013;Jahanbakhshi & Madnia 2016;Chinzei et al 1986;Debisschop et al 1994) have shown that the growth rate of a non-reacting compressible mixing layer is dependent on the convective Mach number, and the results from these works agree well with Barone et al (2006) regression fit that suggests the growth rate of a non-reacting compressible mixing layer is proportional to…”

Section: Heat Release and Compressibility Effectssupporting

confidence: 69%

The effect of heat release on the entrainment in a turbulent mixing layer

Jahanbakhshi

Madnia

2018

J. Fluid Mech.

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Direct numerical simulations of a temporally evolving compressible reacting mixing layer have been performed to study the entrainment of the irrotational flow into the turbulent region across the turbulent/non-turbulent interface (TNTI). In order to study the effects of heat release and interaction of the flame with the TNTI on turbulence several cases with different heat release levels, $Q$, and stoichiometric mixture fractions are chosen for the simulations with the highest opted value for $Q$ corresponding to hydrogen combustion in air. The combustion is mimicked by a one-step irreversible global reaction, and infinitely fast chemistry approximation is used to compute the species mass fractions. Entrainment is studied via two mechanisms: nibbling, considered as the vorticity transport across the TNTI, and engulfment, the drawing of the pockets of the outside irrotational fluid into the turbulent region. As the level of heat release increases, the total entrained mass flow rate into the mixing layer decreases. In a reacting mixing layer by increasing the heat release rate, the mass flow rate due to nibbling is shown to decrease mostly due to a reduction of the local entrainment velocity, while the surface area of the TNTI does not change significantly. It is also observed that nibbling is a viscous dominated mechanism in non-reacting flows, whereas it is mostly carried out by inviscid terms in reacting flows with high level of heat release. The contribution of the engulfment to entrainment is small for the non-reacting mixing layers, while mass flow rate due to engulfment can constitute close to 40 % of the total entrainment in reacting cases. This increase is primarily related to a decrease of entrained mass flow rate due to nibbling, while the entrained mass flow rate due to engulfment does not change significantly in reacting cases. It is shown that the total entrained mass flow rate in reacting and non-reacting compressible mixing layers can be estimated from an expression containing the convective Mach number and the density change due to heat release.

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Section: Heat Release and Compressibility Effectssupporting

confidence: 69%

The effect of heat release on the entrainment in a turbulent mixing layer

Jahanbakhshi

Madnia

2018

J. Fluid Mech.

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“…The criteria for this selection is to have the broadest range of dilatation values, since it has been shown by Suman & Girimaji (2010) that the local flow topology and the behaviour of velocity gradients are highly dependent on the dilatation. A brief description of the DNS is provided in this section while a detailed description can be found in the previous works by Vaghefi et al (2013) and Vaghefi (2014).…”

Section: Dns Of Compressible Mixing Layermentioning

confidence: 99%

Local flow topology and velocity gradient invariants in compressible turbulent mixing layer

Vaghefi

Madnia

2015

J. Fluid Mech.

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The local flow topology is studied using the invariants of the velocity gradient tensor in compressible turbulent mixing layer via direct numerical simulation (DNS) data. The topological and dissipating behaviours of the flow are analysed in two different regions: in proximity of the turbulent/non-turbulent interface (TNTI), and inside the turbulent region. It is found that the distribution of various flow topologies in regions close to the TNTI differs from inside the turbulent region, and in these regions the most probable topologies are non-focal. In order to better understand the behaviour of different flow topologies, the probability distributions of vorticity norm, dissipation and rate of stretching are analysed in incompressible, compressed and expanded regions. It is found that the structures undergoing compression-expansion in axial-radial directions have the highest contraction rate in locally compressed regions, and in locally expanded regions the structures undergoing expansion-compression in axial-radial directions have the highest stretching rate. The occurrence probability of different flow topologies conditioned by the dilatation level is presented and it is shown that the structures in the locally compressed regions tend to have stable topologies while in locally expanded regions the unstable topologies are prevalent.

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“…They studied SGS parameters, such as viscous/scalar dissipation 13 ; divergence of the SGS stresses, and the kinetic energy transfer term 14 ; and orientation and magnitude of SGS scalar flux. 15 In addition, they evaluated some SGS models, including viscous/scalar dissipation closures 13 ; scale similarity, one-equation viscosity, and non-viscosity dynamic structure models 14 ; and Smagorinsky, Vreman, and gradient models. 15 Particularly, Vaghefi et al 13 proposed a modification in the SGS viscous dissipation model to improve its estimation, based on a priori analysis.…”

Section: A Priori Evaluation Of Subgrid-scale Modelsmentioning

confidence: 99%

“…15 In addition, they evaluated some SGS models, including viscous/scalar dissipation closures 13 ; scale similarity, one-equation viscosity, and non-viscosity dynamic structure models 14 ; and Smagorinsky, Vreman, and gradient models. 15 Particularly, Vaghefi et al 13 proposed a modification in the SGS viscous dissipation model to improve its estimation, based on a priori analysis.…”

Section: A Priori Evaluation Of Subgrid-scale Modelsmentioning

confidence: 99%

Removal of the highest energy POD mode for optimal construction of subgrid-scale parameters in a SPIV-measured turbulent mixing layer flow

Rahmani

Kalaei

Akbari

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part C:

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Large eddy simulation is based on decomposition of turbulent flow structures to large energy-containing scales and small subgrid-scale (SGS) structures. The present study analyzes the effect of removing high-energy modes of flow to find the optimal construction of SGS parameters using the a priori approach. The data belong to a shear layer flow measured by stereoscopic particle image velocimetry (SPIV). The proper orthogonal decomposition (POD) method is used to capture all energy modes of the acquired velocity field. The missing/erroneous data are reconstructed using the gappy POD method. Particularly, similarity and mixed models are used to evaluate the SGS parameters. The results of the mixed model are compared via the a priori approach, before and after removing the high-energy modes. For the present flow, it is found that removal of just the first POD mode (as a representative of the mean flow) leads to the best SGS reconstruction, and this results in one order of magnitude higher precision of the average SGS stresses.

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A prioriassessment of the subgrid scale viscous/scalar dissipation closures in compressible turbulence

Cited by 15 publications

References 40 publications

The effect of heat release on the entrainment in a turbulent mixing layer

The effect of heat release on the entrainment in a turbulent mixing layer

Local flow topology and velocity gradient invariants in compressible turbulent mixing layer

Removal of the highest energy POD mode for optimal construction of subgrid-scale parameters in a SPIV-measured turbulent mixing layer flow

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