Budget analysis of the turbulent kinetic energy for bubbly flow in a vertical channel

Santarelli, Claudio; Roussel, Jean; Fröhlich, Jochen

doi:10.1016/j.ces.2015.10.013

Cited by 48 publications

(34 citation statements)

References 40 publications

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“…Particles were also observed to decrease the thickness of the boundary layer and increase the skin friction. A similar modification to the near-wall velocity profile was observed in dense suspensions of neutrally buoyant particles (Picano et al 2015;Santarelli et al 2016;Lashgari et al 2016Lashgari et al , 2017. Even at small density ratios, significant turbulence modulation was observed in those studies, with three distinct regimes revealed by the Reynolds stress budget: laminar, turbulent and inertial shear-thickening depending on the relative contribution from viscous and particle stresses on the momentum transfer across the channel.…”

Section: Introductionsupporting

confidence: 69%

On the transition between turbulence regimes in particle-laden channel flows

2018

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Turbulent wall-bounded flows exhibit a wide range of regimes with significant interaction between scales. The fluid dynamics associated with single-phase channel flows is predominantly characterized by the Reynolds number. Meanwhile, vastly different behaviour exists in particle-laden channel flows, even at a fixed Reynolds number. Vertical turbulent channel flows seeded with a low concentration of inertial particles are known to exhibit segregation in the particle distribution without significant modification to the underlying turbulent kinetic energy (TKE). At moderate (but still low) concentrations, enhancement or attenuation of fluid-phase TKE results from increased dissipation and wakes past individual particles. Recent studies have shown that denser suspensions significantly alter the two-phase dynamics, where the majority of TKE is generated by interphase coupling (i.e. drag) between the carrier gas and clusters of particles that fall near the channel wall. In the present study, a series of simulations of vertical particle-laden channel flows with increasing mass loading is conducted to analyse the transition from the dilute limit where classical mean-shear production is primarily responsible for generating fluid-phase TKE to high-mass-loading suspensions dominated by drag production. Eulerian–Lagrangian simulations are performed for a wide range of particle loadings at two values of the Stokes number, and the corresponding two-phase energy balances are reported to identify the mechanisms responsible for the observed transition.

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Section: Introductionsupporting

confidence: 69%

On the transition between turbulence regimes in particle-laden channel flows

2018

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“…The latter effort calculated terms in a budget equation of TKE in coordinates attached to moving particles in particle-laden homogeneous isotropic turbulence. A direct investigation of the TKE budget equations of a fully resolved particle–fluid two-phase system was performed by Santarelli, Roussel & Fröhlich (2016) for a turbulent channel flow laden with small bubbles acting as rigid particles. This effort provided useful data to understand the turbulence modulation by light particles, but only the budget equation of the total TKE was investigated.…”

Section: Resultsmentioning

confidence: 99%

A direct numerical investigation of two-way interactions in a particle-laden turbulent channel flow

2019

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Understanding the two-way interactions between finite-size solid particles and a wall-bounded turbulent flow is crucial in a variety of natural and engineering applications. Previous experimental measurements and particle-resolved direct numerical simulations revealed some interesting phenomena related to particle distribution and turbulence modulation, but their in-depth analyses are largely missing. In this study, turbulent channel flows laden with neutrally buoyant finite-size spherical particles are simulated using the lattice Boltzmann method. Two particle sizes are considered, with diameters equal to 14.45 and 28.9 wall units. To understand the roles played by the particle rotation, two additional simulations with the same particle sizes but no particle rotation are also presented for comparison. Particles of both sizes are found to form clusters. Under the Stokes lubrication corrections, small particles are found to have a stronger preference to form clusters, and their clusters orientate more in the streamwise direction. As a result, small particles reduce the mean flow velocity less than large particles. Particles are also found to result in a more homogeneous distribution of turbulent kinetic energy (TKE) in the wall-normal direction, as well as a more isotropic distribution of TKE among different spatial directions. To understand these turbulence modulation phenomena, we analyse in detail the total and component-wise volume-averaged budget equations of TKE with the simulation data. This budget analysis reveals several mechanisms through which the particles modulate local and global TKE in the particle-laden turbulent channel flow.

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“…The particle configuration adopted by Vreman & Kuerten (2018) may bring some difficulty to the assessment of how the modulation effects brought by particles interact with the near-wall turbulence. A budget analysis applied to a general particle-fluid two-phase system was carried out by Santarelli, Roussel & Fröhlich (2016), who explicitly calculated each term in a TKE budget equation for a turbulent channel flow laden with bubbles. In these mentioned studies, only a budget analysis applied to the total TKE was performed.…”

Section: Introductionmentioning

confidence: 99%

“…Since particles can slip on the channel wall while fluid cannot, freely moving particles appearing in the near-wall region may create large local velocity gradients that require very fine grid resolutions to resolve, which were not usually affordable. In the reported TKE budget analyses with every term explicitly computed, the errors were beyond 10 % (see Santarelli et al 2016;Peng & Wang 2019;Peng et al 2019b). This level of error complicates reliable quantitative analyses of the results.…”

Section: Introductionmentioning

confidence: 99%