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Xia, Z., Brethouwer, G. & Chen, S. (2018). High-order moments of streamwise fluctuations in a turbulent channel flow with spanwise rotation. PHYSICAL REVIEW FLUIDS, 3(2), Article ID 022601.
Åpne denne publikasjonen i ny fane eller vindu >>High-order moments of streamwise fluctuations in a turbulent channel flow with spanwise rotation
2018 (engelsk)Inngår i: PHYSICAL REVIEW FLUIDS, ISSN 2469-990X, Vol. 3, nr 2, artikkel-id 022601Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

It is well known that the spanwise rotation in turbulent channel flow alters the mean velocity distribution to a linear law. In the present work, we have studied the higher-order moments of the streamwise fluctuations in a turbulent channel flow with spanwise rotation. Our results show that in a significant part of the channel the 2p-order moments, raised by the power 1/p with p = 1,2, ... ,6, also follow linear behavior according to <(u'(+))(2p)>(1/p) = a(p) (y/h) + b(p). Here, u'(+) is the streamwise velocity fluctuation normalized by the global friction velocity, h is the channel half width, and b(p) and a(p) are the intercept and the slope, respectively, which vary with Reynolds and rotation numbers. The linear regions can be extended by introducing a self-similar scaling, that is, 2p-order moments as a function of 2q-order moments. The slopes in the self-similar scaling a(p)/a(1) do not reveal sub-Gaussian behavior as in nonrotating wall-bounded flows, but rather Gaussian or super-Gaussian behaviors.

sted, utgiver, år, opplag, sider
AMER PHYSICAL SOC, 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-223793 (URN)10.1103/PhysRevFluids.3.022601 (DOI)000424921500001 ()2-s2.0-85043281406 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2016-03533
Merknad

QC 20180307

Tilgjengelig fra: 2018-03-07 Laget: 2018-03-07 Sist oppdatert: 2018-03-07bibliografisk kontrollert
Brethouwer, G. (2018). Passive scalar transport in rotating turbulent channel flow. Journal of Fluid Mechanics, 844, 297-322
Åpne denne publikasjonen i ny fane eller vindu >>Passive scalar transport in rotating turbulent channel flow
2018 (engelsk)Inngår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 844, s. 297-322Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Passive scalar transport in turbulent channel flow subject to spanwise system rotation is studied by direct numerical simulations. The Reynolds number R-e= U(b)h/nu is fixed at 20 000 and the rotation number R-o= 2 Omega h/U-b is varied from 0 to 1.2, where U-b is the bulk mean velocity, h the half channel gap width and Omega the rotation rate. The scalar is constant but different at the two walls, leading to steady scalar transport across the channel. The rotation causes an unstable channel side with relatively strong turbulence and turbulent scalar transport, and a stable channel side with relatively weak turbulence or laminar-like flow, weak turbulent scalar transport but large scalar fluctuations and steep mean scalar gradients. The distinct turbulent-laminar patterns observed at certain Ro on the stable channel side induce similar patterns in the scalar field. The main conclusions of the study are that rotation reduces the similarity between the scalar and velocity field and that the Reynolds analogy for scalar-momentum transport does not hold for rotating turbulent channel flow. This is shown by a reduced correlation between velocity and scalar fluctuations, and a strongly reduced turbulent Prandtl number of less than 0.2 on the unstable channel side away from the wall at higher Ro. On the unstable channel side, scalar scales become larger than turbulence scales according to spectra and the turbulent scalar flux vector becomes more aligned with the mean scalar gradient owing to rotation. Budgets in the governing equations of the scalar energy and scalar fluxes are presented and discussed as well as other statistics relevant for turbulence modelling.

sted, utgiver, år, opplag, sider
CAMBRIDGE UNIV PRESS, 2018
Emneord
rotating turbulence, turbulence simulation, turbulent mixing
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-238930 (URN)10.1017/jfm.2018.198 (DOI)000448729500004 ()2-s2.0-85044935235 (Scopus ID)
Merknad

QC 20181114

Tilgjengelig fra: 2018-11-14 Laget: 2018-11-14 Sist oppdatert: 2018-11-14bibliografisk kontrollert
Montecchia, M., Brethouwer, G., Johansson, A. V. & Wallin, S. (2017). Taking large-eddy simulation of wall-bounded flows to higher Reynolds numbers by use of anisotropy-resolving subgrid models. Physical Review Fluids, 2, Article ID 034601.
Åpne denne publikasjonen i ny fane eller vindu >>Taking large-eddy simulation of wall-bounded flows to higher Reynolds numbers by use of anisotropy-resolving subgrid models
2017 (engelsk)Inngår i: Physical Review Fluids, E-ISSN 2469-990X, Vol. 2, artikkel-id 034601Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Properly resolved large-eddy simulations of wall-bounded high Reynolds number flows using standard subgrid-scale (SGS) models requires high spatial and temporal resolution. We have shown that a more elaborate SGS model taking into account the SGS Reynolds stress anisotropies can relax the requirement for the number of grid points by at least an order of magnitude for the same accuracy. This was shown by applying the recently developed explicit algebraic subgrid-scale model (EAM) to fully developed high Reynolds number channel flows with friction Reynolds numbers of 550, 2000, and 5200. The near-wall region is fully resolved, i.e., no explicit wall modeling or wall functions are applied. A dynamic procedure adjusts the model at the wall for both low and high Reynolds numbers. The resolution is reduced, from the typically recommended 50 and 15 wall units in the stream-and spanwise directions respectively, by up to a factor of 5 in each direction. It was shown by comparison with direct numerical simulations that the EAM is much less sensitive to reduced resolution than the dynamic Smagorinsky model. Skin friction coefficients, mean flow profiles, and Reynolds stresses are better predicted by the EAM for a given resolution. Even the notorious overprediction of the streamwise fluctuation intensity typically seen in poorly resolved LES is significantly reduced whenEAMis used on coarse grids. The improved prediction is due to the capability of the EAM to capture the SGS anisotropy, which becomes significant close to the wall.

sted, utgiver, år, opplag, sider
American Physical Society, 2017
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-220931 (URN)10.1103/PhysRevFluids.2.034601 (DOI)000396070400001 ()2-s2.0-85028541529 (Scopus ID)
Merknad

QC 20180110

Tilgjengelig fra: 2018-01-09 Laget: 2018-01-09 Sist oppdatert: 2019-04-04bibliografisk kontrollert
Lenaers, P., Schlatter, P., Brethouwer, G. & Johansson, A. V. (2016). A new high-order method for simulating turbulent pipe flow. In: Springer Proceedings in Physics: . Paper presented at 6th International Conference on Progress in Turbulence, iTi 2014, 29 August 2014 through 29 August 2014 (pp. 211-215). Springer
Åpne denne publikasjonen i ny fane eller vindu >>A new high-order method for simulating turbulent pipe flow
2016 (engelsk)Inngår i: Springer Proceedings in Physics, Springer, 2016, s. 211-215Konferansepaper, Publicerat paper (Fagfellevurdert)
sted, utgiver, år, opplag, sider
Springer, 2016
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-194619 (URN)10.1007/978-3-319-29130-7_37 (DOI)2-s2.0-84966937466 (Scopus ID)9783319291291 (ISBN)
Konferanse
6th International Conference on Progress in Turbulence, iTi 2014, 29 August 2014 through 29 August 2014
Merknad

Correspondence Address: Schlatter, P.; Linné FLOW Centre, KTH MechanicsSweden; email: pschlatt@mech.kth.se. QC 20161101

Tilgjengelig fra: 2016-11-01 Laget: 2016-10-31 Sist oppdatert: 2019-10-11bibliografisk kontrollert
Grigoriev, I., Wallin, S., Brethouwer, G., Grundestam, O. & Johansson, A. V. (2016). Algebraic Reynolds stress modeling of turbulence subject to rapid homogeneous and non-homogeneous compression or expansion. Physics of fluids, 28(2), 026101
Åpne denne publikasjonen i ny fane eller vindu >>Algebraic Reynolds stress modeling of turbulence subject to rapid homogeneous and non-homogeneous compression or expansion
Vise andre…
2016 (engelsk)Inngår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 28, nr 2, s. 026101-Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A recently developed explicit algebraic Reynolds stress model (EARSM) by Grigoriev et al. ["A realizable explicit algebraic Reynolds stress model for compressible turbulent flow with significant mean dilatation," Phys. Fluids 25(10), 105112 (2013)] and the related differential Reynolds stress model (DRSM) are used to investigate the influence of homogeneous shear and compression on the evolution of turbulence in the limit of rapid distortion theory (RDT). The DRSM predictions of the turbulence kinetic energy evolution are in reasonable agreement with RDT while the evolution of diagonal components of anisotropy correctly captures the essential features, which is not the case for standard compressible extensions of DRSMs. The EARSM is shown to give a realizable anisotropy tensor and a correct trend of the growth of turbulence kinetic energy K, which saturates at a power law growth versus compression ratio, as well as retaining a normalized strain in the RDT regime. In contrast, an eddy-viscosity model results in a rapid exponential growth of K and excludes both realizability and high magnitude of the strain rate. We illustrate the importance of using a proper algebraic treatment of EARSM in systems with high values of dilatation and vorticity but low shear. A homogeneously compressed and rotating gas cloud with cylindrical symmetry, related to astrophysical flows and swirling supercritical flows, was investigated too. We also outline the extension of DRSM and EARSM to include the effect of non-homogeneous density coupled with "local mean acceleration" which can be important for, e.g., stratified flows or flows with heat release. A fixed-point analysis of direct numerical simulation data of combustion in a wall-jet flow demonstrates that our model gives quantitatively correct predictions of both streamwise and cross-stream components of turbulent density flux as well as their influence on the anisotropies. In summary, we believe that our approach, based on a proper formulation of the rapid pressure-strain correlation and accounting for the coupling with turbulent density flux, can be an important element in CFD tools for compressible flows.

sted, utgiver, år, opplag, sider
American Institute of Physics (AIP), 2016
Emneord
Turbulence, compressible flow, EARSM, DRSM
HSV kategori
Forskningsprogram
Teknisk mekanik
Identifikatorer
urn:nbn:se:kth:diva-183447 (URN)10.1063/1.4941352 (DOI)000371286500057 ()2-s2.0-84958818780 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2010-3938
Merknad

QC 20160314. QC 20160704

Tilgjengelig fra: 2016-03-11 Laget: 2016-03-11 Sist oppdatert: 2017-11-30bibliografisk kontrollert
Maffioli, A., Brethouwer, G. & Lindborg, E. (2016). Mixing efficiency in stratified turbulence. Journal of Fluid Mechanics, 794, Article ID R3.
Åpne denne publikasjonen i ny fane eller vindu >>Mixing efficiency in stratified turbulence
2016 (engelsk)Inngår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 794, artikkel-id R3Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We consider mixing of the density field in stratified turbulence and argue that, at sufficiently high Reynolds numbers, stationary turbulence will have a mixing efficiency and closely related mixing coefficient described solely by the turbulent Froude number (Formula presented.), where (Formula presented.) is the kinetic energy dissipation, (Formula presented.) is a turbulent horizontal velocity scale and (Formula presented.) is the Brunt–Väisälä frequency. For (Formula presented.), in the limit of weakly stratified turbulence, we show through a simple scaling analysis that the mixing coefficient scales as (Formula presented.), where (Formula presented.) and (Formula presented.) is the potential energy dissipation. In the opposite limit of strongly stratified turbulence with (Formula presented.), we argue that (Formula presented.) should reach a constant value of order unity. We carry out direct numerical simulations of forced stratified turbulence across a range of (Formula presented.) and confirm that at high (Formula presented.), (Formula presented.), while at low (Formula presented.) it approaches a constant value close to (Formula presented.). The parametrization of (Formula presented.) based on (Formula presented.) due to Shih et al. (J. Fluid Mech., vol. 525, 2005, pp. 193–214) can be reinterpreted in this light because the observed variation of (Formula presented.) in their study as well as in datasets from recent oceanic and atmospheric measurements occurs at a Froude number of order unity, close to the transition value (Formula presented.) found in our simulations.

sted, utgiver, år, opplag, sider
Cambridge University Press, 2016
Emneord
mixing and dispersion, ocean processes, stratified turbulence
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-187087 (URN)10.1017/jfm.2016.206 (DOI)000373937400003 ()2-s2.0-84962631312 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2013-5784
Merknad

QC 20160517

Tilgjengelig fra: 2016-05-17 Laget: 2016-05-17 Sist oppdatert: 2017-11-30bibliografisk kontrollert
Grigoriev, I., Brethouwer, G., Wallin, S. & Johansson, A. V. (2016). Unified explicit algebraic Reynolds stress model for compressible, heat-releasing and supercritical flowswith large density variation.
Åpne denne publikasjonen i ny fane eller vindu >>Unified explicit algebraic Reynolds stress model for compressible, heat-releasing and supercritical flowswith large density variation
2016 (engelsk)Rapport (Annet vitenskapelig)
Abstract [en]

An explicit algebraic model (EARSM) for variable denstiy turbulent flow developed by Grigoriev et al. [Phys. Fluids (2015)] is revisited here. We apply it to a quasi one-dimensional nozzle flow, a wall-jet flow with combustion and large density variation and a supercritical flow of carbon dioxide with heat transfer and buoyancy. It is confirmed that the coupling between strong mean density gradient due to high speed, heat release or thermodynamic variations and the 'local mean acceleration' of the flow produces strong turbulent density and heat fluxes, which strongly affect the turbulence. The possible calibration branches are identified and analyzed. We show that a simple and unified calibration of the model gives good predictions for all cases considered. Therefore, the model is a reliable tool for the computation of compressible flows with large density variation.

Publisher
s. 18
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-183450 (URN)
Merknad

QC20160314

Tilgjengelig fra: 2016-03-11 Laget: 2016-03-11 Sist oppdatert: 2016-03-14bibliografisk kontrollert
Lenaers, P., Schlatter, P., Brethouwer, G. & Johansson, A. (2015). A new high-order method for the accurate simulation of incompressible wall-bounded flows. In: 9th International Conference on Direct and Large-Eddy Simulation, 2013: . Paper presented at 3 April 2013 through 5 April 2013 (pp. 133-138). Springer Publishing Company
Åpne denne publikasjonen i ny fane eller vindu >>A new high-order method for the accurate simulation of incompressible wall-bounded flows
2015 (engelsk)Inngår i: 9th International Conference on Direct and Large-Eddy Simulation, 2013, Springer Publishing Company, 2015, s. 133-138Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

A new high-order method for the accurate simulation of incompressible wall-bounded flows is presented. In stream- and spanwise direction the discretisation is performed by standard Fourier series, while in wall-normal direction the method combines high-order collocated compact finite differences with the influence matrix method to calculate the pressure boundary conditions that render the velocity field divergence-free. The main advantage over Chebyshev collocation is that in wall normal direction, the grid can be chosen freely and thus excessive clustering near the wall is avoided. Both explicit and implicit discretisations of the viscous terms are described, with the implicit method being more complex, but also having a wider range of applications. The method is validated by simulating fully turbulent channel flow at friction Reynolds number Reτ=395, and comparing our data with existing numerical results. The results show excellent agreement proving that the method simulates all physical processes correctly.

sted, utgiver, år, opplag, sider
Springer Publishing Company, 2015
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-194710 (URN)10.1007/978-3-319-14448-1_18 (DOI)2-s2.0-84964892425 (Scopus ID)9783319144474 (ISBN)
Konferanse
3 April 2013 through 5 April 2013
Merknad

QC 20161122

Tilgjengelig fra: 2016-11-22 Laget: 2016-10-31 Sist oppdatert: 2016-11-22bibliografisk kontrollert
Grigoriev, I. A., Wallin, S., Brethouwer, G. & Johansson, A. V. (2015). Capturing turbulent density flux effects in variable density flow by an explicit algebraic model. Physics of fluids, 27(4), Article ID 1.4917278.
Åpne denne publikasjonen i ny fane eller vindu >>Capturing turbulent density flux effects in variable density flow by an explicit algebraic model
2015 (engelsk)Inngår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 27, nr 4, artikkel-id 1.4917278Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The explicit algebraic Reynolds stress model of Grigoriev et al. ["A realizable explicit algebraic Reynolds stress model for compressible turbulent flow with significant mean dilatation," Phys. Fluids 25, 105112 (2013)] is extended to account for the turbulent density flux in variable density flows. The influence of the mean dilatation and the variation of mean density on the rapid pressure-strain correlation are properly accounted for introducing terms balancing a so-called "baroclinic" production in the Reynolds stress tensor equation. Applying the weak-equilibrium assumption leads to a self-consistent formulation of the model. The model together with a K - ω model is applied to a quasi-one-dimensional plane nozzle flow transcending from subsonic to supersonic regimes. The model remains realizable with constraints put on the model parameters. When density fluxes are taken into account, the model is less likely to become unrealizable. The density variance coupled with a "local mean acceleration" also can influence the model acting to increase anisotropy. The general trends of the behaviour of the anisotropy and production components under the variation of model parameters are assessed. We show how the explicit model can be applied to two- and three-dimensional mean flows without previous knowledge of a tensor basis to obtain the general solution. Approaches are proposed in order to achieve an approximate solution to the consistency equation in cases when analytic solution is missing. In summary, the proposed model has the potential to significantly improve simulations of variable-density flows.

Emneord
Algebra, Anisotropy, Cyclone separators, Pipe flow, Reynolds number, Tensors, Approximate solution, Explicit algebraic models, Explicit algebraic reynolds stress models, Production components, Quasi-one dimensional, Rapid pressure-strain correlation, Reynolds stress tensors, Variable-density flows
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-166978 (URN)10.1063/1.4917278 (DOI)000353835700030 ()2-s2.0-84928130090 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2010-3938 2013-5784 2014-5700
Merknad

QC 20150528

Tilgjengelig fra: 2015-05-28 Laget: 2015-05-21 Sist oppdatert: 2017-12-04bibliografisk kontrollert
Lazeroms, W., Brethouwer, G., Wallin, S. & Johansson, A. (2015). Efficient treatment of the nonlinear features in algebraic Reynolds-stress and heat-flux models for stratified and convective flows. International Journal of Heat and Fluid Flow, 53, 15-28
Åpne denne publikasjonen i ny fane eller vindu >>Efficient treatment of the nonlinear features in algebraic Reynolds-stress and heat-flux models for stratified and convective flows
2015 (engelsk)Inngår i: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 53, s. 15-28Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This work discusses a new and efficient method for treating the nonlinearity of algebraic turbulence models in the case of stratified and convective flows, for which the equations for the Reynolds stresses and turbulent heat flux are strongly coupled. In such cases, one finds a quasi-linear set of equations, which can be solved through an appropriate linear expansion in basis tensors and vectors, as discussed in earlier work. However, finding a consistent and truly explicit algebraic turbulence model requires solving an additional equation for the production-to-dissipation ratio (P+G)/ε of turbulent kinetic energy. Due to the nonlinear nature of the problem, the equation for (P+G)/ε is a higher-order polynomial equation for which no analytical solution can be found. Here we provide a new method to approximate the solution of this polynomial equation through an analysis of two special limits (shear-dominated and buoyancy-dominated), in which exact solutions are obtainable. The final result is a model that appropriately combines the two limits in more general cases. The method is tested for turbulent channel flow, both with stable and unstable stratification, and the atmospheric boundary layer with periodic and rapid changes between stable and unstable stratification. In all cases, the model is shown to give consistent results, close to the exact solution of (P+G)/ε. This new method greatly increases the range of applicability of explicit algebraic models, which otherwise would rely on the numerical solution of the polynomial equation.

HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-166800 (URN)10.1016/j.ijheatfluidflow.2015.01.005 (DOI)000355367500002 ()2-s2.0-84923270425 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2013-5784
Merknad

QC 20150521

Tilgjengelig fra: 2015-05-18 Laget: 2015-05-18 Sist oppdatert: 2017-12-04bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-9819-2906