Numerical simulation of flow behavior in a symmetric cavity with varying aspect ratios

Self-resonant nozzles are fluid elements used in water spray devices. In this study, numerical simulations are performed to investigate the changes in the flow field by varying the cavity-to-cavity distance H and the cavity aspect ratio L/D of a symmetric cavity. The basic equations are the two-dimensional incompressible Navier-Stokes equations and the continuity equation. The representative length is the cavity depth D and the representative velocity is the incoming uniform flow velocity U0. The Reynolds number based on D is Re = DU0/ν = 6000 , the same as for a single cavity flow field. A finite difference method was used for discretization. Simulations were performed for L/D = 1.0, 1.5, 2.0, and 3.0, with H = 0.1 to 1.0 (in 0.1 increments), and calculations were carried out from time t = 0 to 300. The results showed that vortices formed in the cavity under all conditions, and the initially symmetric flow field developed into an asymmetric and complex state over time. In particular, when L/D = 1.5 or greater and H was small, the flow in the central region oscillated significantly, and dynamic behavior in which vortices alternately flowed in was observed. On the other hand, at L/D = 1.0, relatively stable symmetry and periodic oscillations were maintained. Additionally, it was confirmed that as L/D increases, the number of vortices and turbulence intensity within the cavity increase, while the Strouhal number tends to decrease.