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Clustering and settling dynamics of inertial particles under turbulence

Abstract : Turbulent particle laden flows are widespread in industrial applications, and natural phenomena. Over the last decades, two observations: preferential concentration, and particle settling velocity modification have stood out as the most relevant consequences of such particle - turbulence interactions. Given the complexity of the problem, this work is composed of four work packages.The first package involves a pitfall analysis of the Vorono"{i} tessellation method, which is widely used to quantify preferential concentration. We found some pitfalls that compromise the results of the analysis using uni-dimensional records. In addition, we propose a new method to disentangle turbulence driven clusters from random spatial fluctuations, a common problem reported by other researchers.The second package involve the analysis of the carrier phase turbulence in our wind tunnel facility. In this regard, we conjecture that the different turbulence generators (active, open, and passive grids) do change the turbulence cascade, and thereby, they could impact the particles preferential concentration and settling behavior. To this aim, we have analysed active grid generated flows, and found that an active grid left open (with minimum blockage) exhibits scalings similar to those found in fractal grids. Moreover, The integral length scale could not be easily computed for active grid generated flows using triple random protocols due to the behavior of the autocorrelation function in such flows, which does not cross zero. We propose a new method to tackle this problem which could be easily applied in a myriad of situations.The third package consist of estimating the turbulent dissipation rate on the carrier phase due to the particle presence. By means of an extension of the Rice theorem, which relates the Taylor length scale with the average distance between zero crossings, we have proposed a method to estimate the carrier phase turbulence in the presence of particles. This method uses particle datasets recorded by phase doppler interferometry. Our results are consistent with previous experiments, and numerical simulations.The fourth package refers to the particle settling modification. We found that the Taylor Reynolds number Re_lambda is the leading order contributor the particles settling modification: at increasing values of Re_lambda the settling velocity of the particles is reduced. Also, at increasing values of Re_lambda the boundaries between positive, and negative particle settling modification shifts to smaller values of the Rouse number Ro=V_T/u.
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Submitted on : Sunday, October 3, 2021 - 1:02:24 AM
Last modification on : Wednesday, November 3, 2021 - 5:58:26 AM
Long-term archiving on: : Tuesday, January 4, 2022 - 6:02:26 PM


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  • HAL Id : tel-03363092, version 1




Daniel Mora-Paiba. Clustering and settling dynamics of inertial particles under turbulence. Fluid mechanics [physics.class-ph]. Université Grenoble Alpes [2020-..], 2020. English. ⟨NNT : 2020GRALI044⟩. ⟨tel-03363092⟩



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