Taylor Length-scale Size Particles in Isotropic Turbulence
Author | : Francesco Lucci |
Publisher | : |
Total Pages | : 149 |
Release | : 2011 |
ISBN-10 | : 1124517685 |
ISBN-13 | : 9781124517681 |
Rating | : 4/5 (85 Downloads) |
Book excerpt: The present study investigates the two-way coupling effects of finite-size solid spherical particles on decaying isotropic turbulence using an immersed boundary method. study of the interactions between finite-size particles andisotropic turbulence. The conventional point particle assumption is valid only in the case of particles with a diameter, dp, much smaller than the Kolmogorov length scale, %eta. In a simulation with particles of diameter dp/sub” %eta the flow around each particle needs to be resolved. In this study, we use a method similar to that of Uhlmann(2005) that adapts the Immersed Boundary(IB) Method developed by Peskin to simulate the flow around suspended spherical solid particles. The main idea of the method is to distribute a number of Lagrangian points uniformly over the surface of the particle. A force is applied at each Lagrangian point to represent the momentum exchange between the particle and the surrounding fluid. An analytic three-point delta function is used to distribute the force to the Eulerian grid points saddling the spherical surface to satisfy the no-slip condition at each Lagrangian point. Decaying turbulence is simulated in a periodic box with a uniform mesh of up to (512)sup3/sup grid points and an initial microscale Reynolds number of up to Resub%lambda 0= 110. We compare the single phase flow (SPF) with particle-laden flows with particles of different diameters. The density of the particle varies from 2.56 to 10 times that of the fluid. The effects of the particles on the temporal development of turbulence kinetic energy E(t), its dissipation rate e(t), its two-way coupling rate of change Psi_p(t) and frequency spectra E(%omega) are discussed. In this study, in contrast to particles with d_p %eta, particles with d_p %eta always increase the dissipation rate of turbulence kinetic energy, e(t). In addition, \Psi_p(t) is always positive, whereas it can be positive or negative for particles with d_p