Acta Mech Sinica (2006) 22: 99–108 DOI 10.1007/s10409-006-0103-9 RESEARCH PAPER Yi Wu · Hangfeng Wang · Zhaohui Liu · Jing Li Liqi Zhang · Chuguang Zheng Experimental investigation on turbulence modification in a horizontal channel flow at relatively low mass loading * Received: 11 July 2005 / Accepted: 6 January 2006 / Revised: 16 January 2006 / Published online: 13 April 2006 © Springer-Verlag 2006 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 6826 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 Kol- mogorov 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 , respec- tively. The results show that the presence of particles can dra- matically modify the turbulence even under the lowest mass loading ratio of 5×10 -4 . The mean flow is attenuated and de- creased 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, indi- cating 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 ∗ 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. Y. Wu · H. F. Wang · Z. H. Liu (B ) · J. Li · L. Q. Zhang · C. G. Zheng State Key Lab. Coal Combustion, Huazhong Univ. of Sci. & Tech., Wuhan 430074, China E-mail: zliu@hust.edu.cn particles. The inertia of particles is proved to be very impor- tant for the turbulence modification and particles behaviors and thus should be considered in horizontal channels. Keywords Horizontal channel · Particle-laden flow · Turbulence modification · PIV 1 Introduction Particle-laden flows exist in various natural, industrial and environmental processes such as sediment transports in riv- ers, pneumatic transports of granular materials, pollution con- trols and so on. Obviously, the behaviors of particles will be affected by the turbulence, on the other hand, in some cases, if the particle mass loading is high enough, the turbulence might be modified by the particles. This is known as tur- bulence modification or two-way coupling of particle-laden flows. In the past decades, numerous studies on this topic have been performed, which proved that many parameters were involved in determining the turbulence modification. First, Gore et al. [1] summarized the previous work and concluded that the ratio of particle diameter/fluid length scale could be used to distinguish the regimes of turbulence augmentation and attenuation. But Vinberg et al. [2] and Yarin et al. [3] both found that small particle could also enhance the turbu- lence in some cases. Then Hetsroni [4] proposed that par- ticles with a low particle Reynolds number Re p tended to suppress the turbulence whereas particles with high Re p would enhance turbulence, due to vortex shedding. However, the experimental work of Hardalupas et al. [5] showed that particles without wake shedding (small Re p ) could also in- crease the turbulence. Eaton [6] reviewed previous experi- mental and numerical studies and pointed out that dramatic turbulence attenuation took place when the mass loading ratio was greater than 0.1. Later in his subsequent work, Eaton [7] showed that the magnitude of turbulence modifica- tion was dependent on the dominant turbulence production mechanism. Recently Sato et al. [8] claimed that the inter- particle spacing was a more critical parameter for turbulence