The influence of thermal boundary conditions on turbulent forced convection pipe flow at two Prandtl numbers

Straub, Steffen; Forooghi, Pourya; Marocco, Luca; Wetzel, Thomas; Vinuesa, Ricardo; Schlatter, Philipp

doi:10.1016/j.ijheatmasstransfer.2019.118601

Cited by 13 publications

(4 citation statements)

References 43 publications

(64 reference statements)

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“…This identity was first derived as a tool for investigating the contribution of Reynolds stress to the skin friction coefficient in channel, pipe and flat boundary layer flows. Similar equations have since been derived to analyse contributions to the Nusselt number in boundary layer and pipe flows [31][32][33][34][35][36]. In this paper, the identity is applied for the Sherwood number Sh, the non-dimensional gradient of concentration at the wall (equivalent to Nusselt number for mass transfer), and employed to quantify the contribution of individual POD and EPOD modes to the time-average wall mass transfer rate.…”

Section: Introductionmentioning

confidence: 99%

Analysis of wall mass transfer in turbulent pipe flow combining extended proper orthogonal decomposition and Fukagata-Iwamoto-Kasagi identity

2022

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We combine extended proper orthogonal decomposition (EPOD) together with the Fukagata-Iwamoto-Kasagi (FIK) identity to quantify the role of individual coherent structures on the wall mass transfer in a turbulent pipe flow. Direct numerical simulation (DNS) at a Reynolds number of 5300 (based on bulk velocity) is performed with the passive scalar released at the pipe inlet. The proper orthogonal decomposition (POD) eigenvalues show that the scalar field can be described by a more compact set of modes compared to the velocity field, and that these modes are skewed towards

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Section: Introductionmentioning

confidence: 99%

Analysis of wall mass transfer in turbulent pipe flow combining extended proper orthogonal decomposition and Fukagata-Iwamoto-Kasagi identity

2022

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“…3. This high sensitivity on thermal boundary condition is typical for liquid metal flows (Straub et al (2019) and references therein).…”

Section: Why Can't the Mixed Convection Onset Be Observed In The Nu Profiles Yet In The Velocity Profiles It Can?mentioning

confidence: 78%

Forced and mixed convection experiments in a confined vertical backward facing step at low-Prandtl number

et al. 2021

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In this paper, we present experimental results for a non-isothermal vertical confined backward facing step conducted with a low-Prandtl number fluid. The eutectic alloy gallium–indium–tin is used as the working fluid. We conducted experiments for different Reynolds and Richardson numbers covering both forced and mixed convection regimes. Time-averaged velocity profiles were measured at six streamwise positions along the test section center-plane with so-called permanent magnet probes. The local Nusselt number was measured in streamwise and spanwise directions along the heating plate mounted right after the step. We further ran RANS simulations of the experiment to study the qualitative influence of assuming a constant specific heat flux thermal boundary condition for the experiment heating plate. The measured velocity profiles show the expected behavior for both studied convection regimes, while the measured streamwise local Nusselt number profiles do not. This is explained by how the heating plate thermal boundary condition is defined. We performed an order of magnitude estimate to estimate the forced- to mixed convection transition onset. The estimate shows good agreement with the experimental data, although further measurements are needed to further validate the estimated transition threshold. The measurement of fluctuating quantities remains an open task to be addressed in future experiments, since the permanent magnet probe measurement equation needs further adjustments. Graphical Abstract

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“…is the source term arising from the exponential decay of cB (z). The corresponding equation for passive scalar, where v i = u i , appears in Straub et al (2019). The governing equations are therefore (2.1) and (5.2), with the flow and scalar quantities being homogeneous in the streamwise direction, and expression (2.5) relating particle and fluid velocities.…”

Section: Resolvent Operator Of Turbulent Flow Laden With Low-inertia ...mentioning

confidence: 99%

Resolvent analysis of turbulent flow laden with low-inertia particles

Schlander,

Rigopoulos,

Papadakis

2024

J. Fluid Mech.

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We extend the resolvent framework to two-phase flows with low-inertia particles. The particle velocities are modelled using the equilibrium Eulerian model. We analyse the turbulent flow in a vertical pipe with Reynolds number of $5300$ (based on diameter and bulk velocity), for Stokes numbers $St^+=0-1$ , Froude numbers $Fr_z=-4,-0.4,0.4,4$ and $1/Fr_z = 0$ (gravity omitted). The governing equations are written in input–output form and a singular value decomposition is performed on the resolvent operator. As for single-phase flows, the operator is low rank around the critical layer, and the true response can be approximated using one singular vector. Even with a crude forcing model, the formulation can predict physical phenomena observed in Lagrangian simulations, such as particle clustering and gravitational effects. Increasing the Stokes number shifts the predicted concentration spectra to lower wavelengths; this shift also appears in the direct numerical simulation spectra and is due to particle clustering. When gravity is present, there are two critical layers, one for the concentration field, and one for the velocity field. For upward flow, the peak of concentration fluctuations shifts closer to the wall, in agreement with the literature. We explain this with the aid of the different locations of the two critical layers. Finally, the model correctly predicts the interaction of near-wall vortices with particle clusters. Overall, the resolvent operator provides a useful framework to explain and interpret many features observed in Lagrangian simulations. The application of the resolvent framework to higher $St^+$ flows in combination with Lagrangian simulations is also discussed.

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The influence of thermal boundary conditions on turbulent forced convection pipe flow at two Prandtl numbers

Cited by 13 publications

References 43 publications

Analysis of wall mass transfer in turbulent pipe flow combining extended proper orthogonal decomposition and Fukagata-Iwamoto-Kasagi identity

Analysis of wall mass transfer in turbulent pipe flow combining extended proper orthogonal decomposition and Fukagata-Iwamoto-Kasagi identity

Forced and mixed convection experiments in a confined vertical backward facing step at low-Prandtl number

Resolvent analysis of turbulent flow laden with low-inertia particles

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