渦流型素子に見られる渦室内流れの数値解析

Abstract

To study the incompressible axisymmetrical laminar swirl flow in a short vortex chamber with exhaust pipe, which characterizes the flow in a vortex diode, the full Navier-Stokes equations with the primitive variables are numerically integrated. For the singularity existing at the axis in cylindrical coordinates system, a novel technique is adopted. The generated flow pattern well agree with the visualized pattern. So, effects of swirl intensity and Reynolds number on the velocity and pressure field, which are difficult to be estimated by experiments, are discussed. The general results obtained by this calculation are summarized: (a) As the swirl intensity increases, the pressure field except for the core tends to take the gradient in radial direction only. (b) Due to this gradient, the radial velocity profiles in the axial direction show unique profiles in the chamber. Near the walls where the boundary layers of tangential flow exist, the radial flow is accelerated towards the axis, while it is decelerated far from the walls and tends to become zero or even reverse for high swirl. (c) Therefore, the flow to e xhaust pipe is restricted near the walls and flow resistance results as the swirl intensity increases.