Narrowband components in two-celled tornado-like vortices generated in a Ward-type simulator

While many studies have been conducted to characterize tornado-like flows, most of the knowledge resulting from these studies is on the mean components of the flows. This paper presents a study aimed at further understanding the turbulence in tornado-like vortices simulated in a Ward-type simulator as well as the fluctuations of the pressures on the surface beneath the simulated vortices. The focus is placed on the narrowband components that have been discovered in both the flows of two-celled vortices and the surface pressures caused by these vortices. The dependences of the characteristic frequency of the narrowband components and the spatial distributions of the standard deviations of these components in the flow and pressure fields on the swirl ratio and radial Reynolds number of the vortices are investigated. The relationship between some observed characteristics of the flow and the corresponding characteristics of the surface pressure are also interpreted to investigate the mechanism that produces the narrowband components.