Abstract
In point-source models for solid particles, the differences of velocity and angular velocity between the object and surrounding fluid are usually considered in the traditional equation of motion. But the curvature of streamline of undisturbed flow has not been considered enough. It suggests that the lift force is ignored in a free vortex, resulting in the poor accuracy for the prediction of particle behavior in turbulence. We investigate the motion of a spherical particle in two different types of background undisturbed flow, namely free and forced vortices, by the direct numerical simulation. For the simulation, we proposed an outflow boundary condition to deal with the circular flow within a limited domain size. To observe the rotating motion of the particle, the particle center was fixed, and freely-rotatable condition and nonrotatable condition were dealt with. By investigating the drag force, lift force and torque acting on the particle, the effect of the geometric parameter of the vortices was clarified. Then we proposed a new correlation equation of the angular velocity. In addition, a general formula for the lift coefficient was suggested taking into account the curvature of the streamlines of the undisturbed flow, the vorticity and the angular velocity.Keywords: Solid Particle, Rotation, Lift Force, Streamline Curvature, Wake, Direct Numerical Simulation
