Fully resolved numerical simulation of particle-laden turbulent flow in a horizontal channel at a low Reynolds number

Abstract

A fictitious domain method is used to perform fully resolved numerical simulations of particle-laden turbulent flow in a horizontal channel. The effects of large particles of diameter 0.05 and 0.1 times the channel height on the turbulence statistics and structures are investigated for different settling coefficients and volume fractions (0.79 %–7.08 %) for the channel Reynolds number being 5000. The results indicate the following. (a) When the particle sedimentation effect is negligible (i.e. neutrally buoyant), the presence of particles decreases the maximum r.m.s. of streamwise velocity fluctuation near the wall by weakening the intensity of the large-scale streamwise vortices, while increasing the r.m.s. of the streamwise fluctuating velocity in the region very close to the wall and in the centre region. On the other hand, the particles increase the r.m.s. of transverse and spanwise fluctuating velocities in the near-wall region by inducing the small-scale vortices. (b) When the particle settling effect is so substantial that most particles settle onto the bottom wall and form a particle sediment layer (SL), the SL plays the role of a rough wall and parts of the vortex structures shedding from the SL ascend into the core region and substantially increase the turbulence intensity there. (c) When the particle settling effect is moderate, the effects of particles on the turbulence are a combination of the former two situations, and the Shields number is a good parameter for measuring the particle settling effects (i.e. the particle concentration distribution in the transverse direction). The average velocities of the particle are smaller in the lower half-channel and larger in the upper half-channel compared to the local fluid velocities in the presence of gravity effects. The effects of the smaller particles on the turbulence are found to be stronger at the same particle volume fractions.

Onset of sediment transport in mono- and bidisperse beds under turbulent shear flow

“…This is comparable to the boxes used in some other studies [21,25,29]. However, Kidanemariam and Uhlmann [20] used a domain with streamwise extent of ≈ 300d p and still reported influence of the box size.…”

“…Therefore, not many studies in that field exist. Pan and Banerjee [25] and Shao et al [29] investigated channel flow with buoyant particles, but put more emphasis on the turbulence structure in the fluid than on particle dynamics. Kidanemariam and Uhlmann performed simulations of particle beds under laminar [21] and turbulent [20] flow and focused on the time evolution of the beds.…”

Measurement of turbulence statistics in single-phase and two-phase flows using ultrasound imaging velocimetry

“…In future work, we will apply the techniques outlined here for a systematic study of particleladen flows. With the present techniques, it will be possible to validate, for instance, the recent work on densely laden channel flows (Picano et al 2015;Shao et al 2012). A wide range of other applications, such as sediment transport or dune/ripple formation is within reach.…”

Momentum balance in flows over mobile granular beds: application of double-averaging methodology to DNS data

“…This is standard practice followed in all numerical studies of this type of configuration (e.g. Kidanemariam et al, 2013;Papista, Dimitrakis, & Yiantsios, 2011;Shao et al, 2012).…”

“…Campagnol et al, 2013), it will take some time before they are used in full for revealing physical mechanisms and testing theoretical predictions. Direct numerical simulations (DNS) with spatially resolved solid-liquid interfaces using the immersed boundary method (IBM) as proposed by Kajishima, Takiguchi, Hamasaki, and Miyake (2001), Uhlmann (2005), or Kempe and Fröhlich (2012a) may serve as an alternative or complimentary approach, providing a huge wealth of data (Chan-Braun, García-Villalba, & Uhlmann, 2011;Kidanemariam, Chan-Braun, Doychev, & Uhlmann, 2013;Shao, Wu, & Yu, 2012;Vowinckel, Jain, Kempe, & Fröhlich, 2017). This approach, however, requires an appropriate representation of the physical configuration targeted.…”