Effect of inertia and gravity on the turbulence in a suspension

A theoretical model is presented for the effect of particle inertia and gravity on the turbulence in a homogeneous suspension. It is an extension of the one-fluid model developed by L'vov, Ooms and Pomyalov (2003), in which the effect of gravity was not considered. In the extended model the particles are assumed to settle in the fluid under the influence of gravity due to the fact, that their density is larger than the fluid density. The generation of turbulence by the settling particles is described, special attention being paid to the turbulence intensity and spectra. A comparison is made with DNS calculations and experimental data. Also a sensitivity study is carried out to investigate at which conditions the gravity effect becomes important. With the model it is possible to calculate the significance of the two-way coupling effect as function of the relevant dimensionless groups. Also an explanation in physical terms is given.