Experimental investigation on turbulence modification in a horizontal channel flow at relatively low mass loading |
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Authors: | Yi Wu Hangfeng Wang Zhaohui Liu Jing Li Liqi Zhang Chuguang Zheng |
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Institution: | (1) State Key Lab. Coal Combustion, Huazhong Univ. of Sci.&Tech, Wuhan, 430074, China |
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Abstract: | Particle-laden flows in a horizontal channel were investigated by means of a two-phase particle image velocimetry (PIV) technique.
Experiments were performed at a Reynolds number of 6 826 and the flow is seeded with polythene beads of two sizes, 60 μm and 110 μm. One was slightly smaller than and the other was larger than the Kolmogorov length scale. The particle loadings were relatively
low, with mass loading ratio ranging from 5×10−4 to 4×10−2 and volume fractions from 6×10−7 to 4.8×10−5, respectively. The results show that the presence of particles can dramatically modify the turbulence even under the lowest
mass loading ratio of 5×10−4. The mean flow is attenuated and decreased with increasing particle size and mass loading. The turbulence intensities are
enhanced in all the cases concerned. With the increase of the mass loading, the intensities vary in a complicated manner in
the case of small particles, indicating complicated particle-turbulence interactions; whereas they increase monotonously in
the case of large particles. The particle velocities and concentrations are also given. The particles lag behind the fluid
in the center region but lead in the wall region, and this trend is more prominent for the large particles. The streamwise
particle fluctuations are larger than the gas fluctuations for both sizes of particles, however their varying trend with the
mass loadings is not so clear. The wall-normal fluctuations increase with increasing mass loadings. They are smaller in the
60 μm particle case but larger in the 110 μm particle case than those of the gas phase. It seems that the small particles follow the fluid motion to certain extent while
the larger particles are more likely dominated by their own inertia. Finally, remarkable non-uniform distributions of particle
concentration are observed, especially for the large particles. The inertia of particles is proved to be very important for
the turbulence modification and particles behaviors and thus should be considered in horizontal channels.
The project supported by the National Natural Science Foundation of China (50276021), and Program for New Century Excellent
Talents in University, Ministry of Education (NCET-04-0708) The English text was polished by Yunming Chen. |
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Keywords: | Horizontal channel Particle-laden flow Turbulence modification PIV |
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