Particle–turbulence interaction and local particle concentration in sediment-laden open-channel flows

Effect of particle clusters on turbulence modulations in liquid flow laden with fine solid particles

“…4) The particles change the energy balance relation and an extra dissipation term is introduced to maintain the energy balance; our results validate the physical model presented by Noguchi and Nezu (2009) that, when the particle diameter is less than the Kolmogorov microscale length, the addition of the particle will increase the turbulence dissipation.…”

“…The influence of the particles on the liquid velocity is very similar to the numerical results of Pan and Banerjee (1996) Because the Stokes number of the particle (St=0.15) is less than unity in the present study, which implies comparatively good following performance of the particles relative to the carrier phase, the particles almost approach the fluid velocity in the outer region of y + >100. The velocity distribution trends of the particles and the liquid are in approximate agreement with the results reported by Noguchi and Nezu (2009), which further shows that our computation is correct. Figure 5 exhibits the profiles of the turbulence intensities along the wall coordinates.…”

“…This means that the addition of the particles leads to an extra dissipation. According to the turbulence modulation criteria presented by Noguchi and Nezu (2009), this phenomenon will occur only if the diameter of the particles is less than the Kolmogorov microscale length.…”

“…According to Noguchi and Nezu (2009), the turbulence should be attenuated near the wall but strengthened at the centre of the channel. On the whole, the turbulence should be reduced along the width of the channel.…”

“…Yarin and Hetsroni (1994) showed that the ratio of the particle diameter to the turbulence scale does not generalize the experimental data for all flows laden with particles of different sizes. Additionally, the experimental work of Noguchi and Nezu (2009) showed that the particle-fluid interaction is governed by the Kolmogorov microscale rather than the macroscale such as the integral scale in sediment-laden flows. Although our numerical results support the physical standard presented by Noguchi and Nezu (2009), there is still lots of work to do to further check and verify the accuracy and correctness of the conclusion.…”