Tornado Vortex Simulation at Purdue University

Abstract

A 4 m wide and 7 m tall tornado vortex generator (including exhaust fan and duct work) has been constructed at Purdue University that operates on a principle similar to that of the earlier machine modeled by Ward (1972). Characteristics of the Purdue simulator are described, as well as the corresponding modifications and improvements that have been made to Ward's machine. Selected photographs of vortex configurations obtained in the simulator demonstrate the ability of the machine to achieve vortex breakdown and multiple vortex configuration. A radial-axial profile of velocity magnitudes (using hot-film anemometry) has been obtained for the state of vortex breakdown characterized by two interlocking helical spiral vortices. This preliminary result shows the potential that the experimental system offers for obtaining quantitative information about the flow field of selected vortex configurations. Multiple vortex phenomena in the thunderstorm-tornado system are examined in light of the laboratory simulation and the similarity concept.

Physical simulation of a single-celled tornado-like vortex, Part A: Flow field characterization

“…The vortex, or vortices, that are produced in the simulator are contained within the meso-cyclone. Consistent with most physical tornado simulators, the swirl ratio, defined herewith as is the primary dimensionless parameter that characterizes the type of vortex formed (Church et al, 1977). In Eq.…”

“…Church et al (1977) developed a tornado vortex chamber (TVCI) at Purdue University that used a rotating wire mesh to provide circulation. They found a secondary circulating flow existing within the primary vortex flow but judged that it exerted negligible flow near the centerline.…”

“…Complete kinematic and dynamic similarity is impossible, however, as the Reynolds number (Re) of a natural tornado is orders of magnitude larger than a simulated one. Fortunately, it has been demonstrated that as long as the flow is turbulent, the effect of Re on a tornado-like vortex is weak, Davies-Jones (1973,1976) from data collected by Ward (1972) and Church et al (1977). Additionally, flow separation over sharp-edged bluff bodies (e.g.…”

Optimal Excitation of Asymmetric Perturbations on an Axisymmetric Barotropic Vortex: A Linear Singular-Value Analysis

“…Later, Fujita (1971) found the corresponding structure in natural vortices: strong tornadoes spawned by supercell thunderstorms. This finding motivated several meteorologists to design wind tunnels with a special setup to model the supercell thunderstorm (Ward 1972;Church et al 1977;Monji 1985). They successfully reproduced tornado-like vortices in which several subsidiary vortices that intertwined with each other formed double, triple, or quadruple helical structures within their parent vortices.…”

A Laboratory Investigation of the Structure of Multiple Vortices

“…Church et al (1977) constructed a similar type of the simulator at Purdue University with a larger dimension and more improved stability to remove the vortex wondering. Church et al (1979) investigated the condition for various types of vortices including the multiple vortices as a function of the swirl ratio and the Reynolds number.…”