The effect of particle clusters on gas-solids fluctuation coupling terms in Reynolds stresses transport equations was investigated in this work. Based on its transport equation, covariance of solids phase volume fraction and gas phase fluctuating velocity, namely drift velocity was closured by an algebraic model, which wasa function of both degree of segregation and mean slip velocity. Thereby two different kinetic-based Euler-Euler mesoscale methods were applied to simulate a dilute gas-particle flow in a triple periodic domain where solids phase averaged volume fraction was 1%. Stokes drag law was applied for inter-phase momentum transfer. Inter-particle collisions were approximated by Bhatnagar-Gross-Krook model. Mesh resolution in this study was as 1.75 times as particle diameter dp. The difference between these two approaches was the way to solve solids phase kinetic equation. The first approach was an Anisotropic Gaussian (AG) Quadrature based moment methodof which particle phase velocity density function fwas assumed to follow a multivariate anisotropic Gaussian. The second approach was a typical two-fluid model (TFM) of which assumedf to follow isotropic distribution. To validate these two methods, results were compared with results given by a Euler-Lagrange(E-L) method in the literature. It demonstrated that AG method was able to produce better comparable results than TFM. For instance, the flow field properties given by AG method were closer to results given by E-L method, including mean slip velocity, gas and solids phase turbulent kinetic energy. Results showed thattheintegral scale of particle clusters was smaller than that of gas-phase fluctuation velocities. And the integral scale of both particle clusters and gas-phase fluctuation velocities turned out to be anisotropic that vertical components were larger than lateral components. The falling of particle clusters was mainly suppressed by form drag (i.e. gas pressure between front and tail). In the end, the coefficients of both gas-solids fluctuation velocity covariance and drift velocity were identified.
|Translated title of the contribution||Effects of particle clusters on fluctuation coupling terms in dilute gas-particle turbulent flows|
|Number of pages||10|
|Journal||Guocheng Gongcheng Xuebao/The Chinese Journal of Process Engineering|
|State||Published - 1 Apr 2019|