Study on bubble-induced turbulence in pipes and containers with Reynolds-stress models

Liao, Yixiang; Ma, Tian

doi:10.1007/s42757-021-0128-0

Cited by 8 publications

(5 citation statements)

References 53 publications

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“…Finally, n i is the normal vector at the phase boundary directed toward the gas phase and I is the interfacial area concentration with f/ x i = -In i . To close (2), the EE approach coupled with RANS modeling [14,[24][25][26][27][28] can be employed, supplemented with a source term, S RANS k , accounting for production of BIT. This can be, e.g., embedded in the two-phase k-e model framework, reading:…”

Section: Implication For Modeling Bitmentioning

confidence: 99%

“…To close (2), the EE approach coupled with RANS modeling 14, 24–28 can be employed, supplemented with a source term,

S_{k}^{RANS}

, accounting for production of BIT. This can be, e.g., embedded in the two‐phase k − ε model framework, reading:

true \begin{matrix} left \frac{D ((1 - α) k)}{Dt} = P_{k}^{normalRANS} + D_{k}^{normalRANS} \underset{ε_{k}^{normalRANS}}{\underset{︸}{- (1 - α) ε}} + \underset{S_{k}^{normalRANS}}{\underset{︸}{C_{I} {boldF}_{normalD} \cdot (U^{G} - U^{L})}} \end{matrix}

…”

Section: Implication For Modeling Bitmentioning

confidence: 99%

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A Note on Modeling the Effects of Surfactants on Bubble‐Induced Turbulence

Liao

Hessenkemper

et al. 2023

Chem Eng & Technol

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Recent experimental results reveal that with rising concentration of surfactants, the generated bubble‐induced turbulence (BIT) increases as well, although the bubbles rise slower. Herein, it is shown that this phenomenon has not be considered so far in the standard Reynolds‐averaged Navier‐Stokes (RANS) modeling for BIT, using the Ansatz with source terms added to the transport equation of turbulent kinetic energy and dissipation, respectively. Some problematic issues related to the common concepts for closure of the liquid‐phase turbulence kinetic energy equation are also discussed. Furthermore, this issue is demonstrated by simulating the experiments using two‐fluid approach.

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Section: Implication For Modeling Bitmentioning

confidence: 99%

“…To close (2), the EE approach coupled with RANS modeling 14, 24–28 can be employed, supplemented with a source term,

S_{k}^{RANS}

, accounting for production of BIT. This can be, e.g., embedded in the two‐phase k − ε model framework, reading:

true \begin{matrix} left \frac{D ((1 - α) k)}{Dt} = P_{k}^{normalRANS} + D_{k}^{normalRANS} \underset{ε_{k}^{normalRANS}}{\underset{︸}{- (1 - α) ε}} + \underset{S_{k}^{normalRANS}}{\underset{︸}{C_{I} {boldF}_{normalD} \cdot (U^{G} - U^{L})}} \end{matrix}

…”

Section: Implication For Modeling Bitmentioning

confidence: 99%

A Note on Modeling the Effects of Surfactants on Bubble‐Induced Turbulence

Liao

Hessenkemper

et al. 2023

Chem Eng & Technol

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“…2020 b ; Ma, Lucas & Bragg 2020 a ; du Cluzeau et al. 2022; Liao & Ma 2022). It was demonstrated recently that this strong anisotropy also exists at the small scales of bubble-induced turbulence (BIT) due to the energy being injected at the scale of the bubble (Ma et al.…”

Section: Introductionmentioning

confidence: 99%

“…Direct numerical simulations (DNS) have revealed the following properties of dilute dispersed bubbly flows. (i) The liquid velocity fluctuations are highly anisotropic, with fluctuations that are much larger in the direction of the mean bubble motion (Lu & Tryggvason 2013;Ma et al 2020b;Ma, Lucas & Bragg 2020a;du Cluzeau et al 2022;Liao & Ma 2022). It was demonstrated recently that this strong anisotropy also exists at the small scales of bubble-induced turbulence (BIT) due to the energy being injected at the scale of the bubble ).…”

Section: Introductionmentioning

confidence: 99%

Effects of surfactants on bubble-induced turbulence

Ma,

Hessenkemper,

Lucas

et al. 2023

J. Fluid Mech.

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We use experiments to explore the effect of surfactants on bubble-induced turbulence (BIT) at different scales, considering how the bubbles affect the flow kinetic energy, anisotropy and extreme events. To this end, high-resolution particle shadow velocimetry measurements are carried out in a bubble column in which the flow is generated by bubble swarms rising in water for two different bubble diameters (3 and 4 mm) and moderate gas volume fractions (0.5 %–1.3 %). We use tap water as the base liquid and add 1-Pentanol as an additional surfactant with varying bulk concentration, leading to different bubble shapes and surface boundary conditions. The results reveal that with increasing surfactant concentration, the BIT generated increases in strength, even though bubbles of a given size rise more slowly with surfactants. We also find that the level of anisotropy in the flow is enhanced with increasing surfactant concentration for bubbles of the same size, and that for the same surfactant concentration, smaller bubbles generate stronger anisotropy in the flow. Concerning the intermittency quantified by the normalized probability density functions of the fluid velocity increments, our results indicate that extreme values in the velocity increments become more probable with decreasing surfactant concentration for cases with smaller bubbles and low gas void fraction, while the effect of the surfactant is much weaker for cases with larger bubble and higher void fractions.

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“…Turbulence, the pseudo-random and apparently unpredictable state of a fluid (Liao and Ma 2022), is one of the most challenging problems in fluid dynamics. Turbulent flows show a marked increase in mixing and friction and the prediction of these phenomena is of great importance in practical engineering applications (De Villiers 2006).…”

Section: Introductionmentioning

confidence: 99%

Rotational vector-based analysis of turbulent structures in channel flow using large eddy simulation simulation

et al. 2023

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Even with modern measurement techniques and data from direct numerical simulation (DNS), it is very difficult to identify the individual attached eddies and understand their dynamical behavior due to the multi-scale nature of the eddies in wall-bounded flows, which puts these issues at the center of the current debate. However, Liutex vector (L for short), a rotational vector field with information on both the rotation axis and swirling strength, has recently been developed by Prof. Liu's group as a more accurate and clear definition of a vortex. Combining conventional and L methods may provide more detailed information about the complex flow structures as well as insights into the flow's mixing and transport features. We simulated the channel flow in large eddy simulation (LES) by implementing an inflow condition based on the box turbulence. After validating the results with DNS data, we used L isosurfaces and their vector profiles to track ordered flow structures in wall-bounded turbulence. Based on the data, we observe numerous turbulent phenomena that have been described in other works with different visualization techniques. Moreover, the shear contamination on the wall is the most severe while all the root-mean-square L component variations are negligible. Due to the presence of background shear, the peak location of vorticity fluctuation is closer to the wall than the corresponding L fluctuation, and the displacement of peak location brought on by shear contamination is greatest for the spanwise component (z-component) of the vorticity fluctuation. According to the two-point correlation of L components, the streamwise size of turbulent structures does not vary considerably with y+, however, the spanwise size of turbulent structures increases gradually as y+ increases.

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Study on bubble-induced turbulence in pipes and containers with Reynolds-stress models

Cited by 8 publications

References 53 publications

A Note on Modeling the Effects of Surfactants on Bubble‐Induced Turbulence

A Note on Modeling the Effects of Surfactants on Bubble‐Induced Turbulence

Effects of surfactants on bubble-induced turbulence

Rotational vector-based analysis of turbulent structures in channel flow using large eddy simulation simulation

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