An investigation of particles effects on wall-normal velocity fluctuations in sand-laden atmospheric surface layer flows

Liu, Hongyou; He, Xibo; Zheng, Xiaojing

doi:10.1063/5.0064193

Cited by 8 publications

(9 citation statements)

References 84 publications

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“…Substantial modification of VLSMs (and turbulence statistics more generally) was observed in the present study, and evidence of similar behaviour is being observed in the atmospheric surface layer (Liu et al. 2021). The complexity of the nonlinear coupling of inertial particles with high- wall turbulence and the high cost of the simulations, however, precludes a full description at this stage.…”

Section: Discussionsupporting

confidence: 91%

“…Finally, we recall the scientific questions posed at the beginning of this paper, namely whether the turbulence modification of VLSMs will persist at high Reynolds number, and whether the mechanisms which modify them are similar to those found in . Substantial modification of VLSMs (and turbulence statistics more generally) was observed in the present study, and evidence of similar behaviour is being observed in the atmospheric surface layer (Liu et al 2021). The complexity of the nonlinear coupling of inertial particles with high-Re wall turbulence and the high cost of the simulations, however, precludes a full description at this stage.…”

Section: Discussionsupporting

confidence: 84%

“…The present results at the higher Reynolds number would seem to suggest that the results of Wang & Richter (2019) may unique to Reynolds numbers near the cusp of being considered asymptotic in the outer layer, but additional simulations at a wider range of at would be needed to confirm this. It is worth noting that at much larger Reynolds numbers in the atmospheric surface layer (), Wang, Gu & Zheng (2020 a ) and Liu, He & Zheng (2021) have observed that the effect of airborne sand/dust is to increase the energy contained in the VLSM range as compared with dust-free conditions.…”

Section: Resultsmentioning

confidence: 99%

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Direct numerical simulation of particle-laden flow in an open channel at

2023

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We perform two-way coupled direct numerical simulation of particle-laden flow in an open channel at a friction Reynolds number ( $Re_{\tau }$ ) of 5186, which exhibits many characteristics of high-Reynolds-number wall-bounded turbulence, such as the distinct separation of scales in the inner and outer layers. Three representative cases, an unladen case and low- and high-Stokes-number particle-laden cases, are performed to investigate the turbulent modification by particles. To this end, we compare several statistical quantities to understand the particle effect on momentum exchange and interphasial energy transfer. The modulation of large-scale motions (LSMs) and very-large-scale motions (VLSMs) are analysed using spectral information, and we find that the LSMs and VLSMs are generally weakened in the inner and outer layers, which is qualitatively different from similar simulations at lower Reynolds numbers ( $Re_{\tau } \approx 500$ ). The spatial structures are investigated with correlation analysis, and inclined VLSMs are observed in the near-wall region, with decreased inclination angles by particles. The particles tend to widen and shorten the spanwise and streamwise extent of coherent structures, respectively. Furthermore, we find that the vorticity vector displays a preferential alignment with the eigenvector corresponding to the intermediate eigenvalue of the strain-rate tensor, independent of the particle Stokes number.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

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Direct numerical simulation of particle-laden flow in an open channel at

2023

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“…Moreover, sandstorms contain not only suspended particles scattered in the air, but also saltating particles at near-wall locations (<0.5 m) (Shao 2008;Zheng 2009). The experimental set-up was improved in 2021 based on the deployment in 2016 to collect information of near-wall saltating particles in wind-blown sand flows/sandstorms Liu, He & Zheng 2021). In addition to the equipment in 2016, an additional pair of sonic anemometer and aerosol monitor were placed at 0.5 m. For the particle concentration measurements of near-wall saltating particles, five sand particle counters (SPC-91, Niigata Electric Co., Ltd.; f s = 1 Hz; z = 0.03, 0.05, 0.1, 0.28 and 0.5 m) and five outdoor hot wires (ComfortSence 54T35, Dantec Dynamics A/S; f s = 2 Hz; z = 0.03, 0.05, 0.1, 0.16 and 0.28 m) were deployed in the range of 0.03-0.5 m (shown in figure 1d,e).…”

Section: Experimental Site and Set-upmentioning

confidence: 99%

“…2017), and the turbulence statistics in particle-laden flows in QLOA have been analysed in detail in Liu et al. (2021, 2023).…”

Section: Experiments and Datamentioning

confidence: 99%

The effect of turbulent motions on particle spatial distribution in high-Reynolds-number particle-laden flows

He,

Liu

2023

J. Fluid Mech.

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The spatial relationship between turbulent and particle concentration structures is investigated based on the turbulent velocity and particle concentration data obtained synchronously at the Qingtu Lake Observation Array site. In addition to the observation of particle concentration structures that contain not only large-scale coherence but also significant energy in the high-Reynolds-number atmospheric surface layer (ASL), the scale of turbulent motions that have the most significant coherence with particle concentration is found to follow a 1/2 power scaling law with the local height and ASL thickness. Moreover, large-scale turbulent velocity fluctuations have a significant amplitude modulation effect on particle concentration fluctuations, but the modulating influence is different for small dust particles and large saltating particles. Based on the interphase amplitude modulation, there exists a particle–turbulence structure phase difference that varies with height, which further makes the structure inclination angle of the particle concentration larger than that of the turbulence. In this scenario, a conceptual model reflecting the relationship between the two is proposed, and a quantitative formulation is further derived and found to be in good agreement with the experimental results. These findings and the proposed model contribute insights into particle–turbulence interactions, thereby providing theoretical support for a unified model of turbulence dynamics and particle kinematics.

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Wall-attached structure characteristics of flow and dust concentration fields in high-Reynolds-number particle-laden flows

He,

Liu,

Zheng

2024

J. Fluid Mech.

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The wall-attached structure characteristics of flow and dust concentration fields are investigated in this study based on high-Reynolds-number ( $Re_{\tau } \sim O(10^{6})$ ) synchronous multiphase observations from the Qingtu Lake observation array site (recorded by Liu et al., J. Fluid Mech., vol. 957, 2023, A14). The results show that not only the particle-free flow field but also the particle-laden flow and dust concentration field contain wall-attached structures. The linear coherence spectrum, as a data-driven filter, is adopted to separate the wall-attached portions from the premultiplied spectra. The decomposed spectra for wall-attached structures in streamwise velocity fluctuations under particle-free and particle-laden conditions show obvious outer-scaling and wall-scaling at large-scale and medium-scale ranges, respectively, but the spectra of dust concentration exhibit only wall-scaling rather than outer-scaling. The streamwise length of the most significant wall-attached dust clustering structures in the logarithmic region is approximately five times the boundary layer thickness, and does not change significantly with height. Furthermore, the streamwise turbulence intensity for wall-attached portions follows the universal Townsend–Perry constant, without particle mass loading effect. Correspondingly, the wall-attached portions of the dust concentration also exhibit universal logarithmic decay slope. The remaining non-attached portions for the turbulent velocity and dust concentration have significant dependence on the particle mass loading.

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An investigation of particles effects on wall-normal velocity fluctuations in sand-laden atmospheric surface layer flows

Cited by 8 publications

References 84 publications

Direct numerical simulation of particle-laden flow in an open channel at

Direct numerical simulation of particle-laden flow in an open channel at

The effect of turbulent motions on particle spatial distribution in high-Reynolds-number particle-laden flows

Wall-attached structure characteristics of flow and dust concentration fields in high-Reynolds-number particle-laden flows

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