The study of asymmetric distribution of cross-corre function of turbulence modulation

As reported in the study of Chang et al. (2003), the modulation of the carrier-phase turbulence, that is, the effect of the presence of dispersed phase on the turbulence structure, is heavily dependent on the term of (<u_gi′u_pi′>-2k). Nevertheless, very few experimental data of <u_gi′u_pi′> can be found in the literature. Wang and Huang (1995) made the <u_gi′u_pi′> measurements by using a phase Doppler anemometer in a planar mixing-layer flow leaded with polydispersed spray. However, the accuracy of the measured <u_gi′u_pi′> data made by Wang and Huang was in doubt according to the comparison results with the model predictions in the study of Chang et al. Tsai (2003) found that Wang and Huang overestimated the turbulence modulation quantity in the shear layer in the downstream regions, and the symmetric assumption of cross-correlation function is unavailable for large particles (30 μm). Lu et al. (2006) found that the <u_gi′u_pi′> term and <u_pi′u_gi′> term are also different besides asymmetric graph of cross-correlation function by using a Particle Doppler Analyzer in a turbulence field with 70 μm monodispersed droplet. This paper will discuss the reason for this.