Axisymmetric modeling to efficiently simulate tornado-like vortex in Ward-type chamber using OpenFOAM

Tornadoes represent a substantial hazard to nuclear power plant infrastructures, particularly in terms of potential damage caused by wind-borne debris. A comprehensive understanding of the three-dimensional flow structure of tornadoes is essential to assess such hazards. Ward-type tornado-like vortex (TLV) generators have been used to provide experimental insight into the influence of wind loading on potential debris and infrastructures. However, these experiments address challenges arising from highly turbulent and three-dimensional flow structures. Recent advancements in the area of TLVs have seen a surge in numerical analyses. Three-dimensional simulations are capable of reproducing the flow field, although the computational requirements appear to be prohibitive for hazard assessment applications. A numerically proficient model that could reproduce the velocity profile from TLV generators is highly regarded. To achieve this, axisymmetric modeling of TLV in a Ward-type chamber is attempted. This paper uses the VorTECH facility at Texas Tech University, a large-scale Ward-type TLV generator, as a reference case. Through a series of simulations, the critical role of the mesh resolution in the development of the boundary layer is revealed. The axisymmetric model underestimated the experimentally observed pressure at the core center while showing good agreement for the core width and velocity distribution for both single-cell and two-cell TLV flow fields. Through alterations in the domain configuration, including the influence of the inflow, floor roughness, and the presence of a honeycomb rectifier, the effect of such factors on the velocity profiles near the touchdown region was identified. The boundary layer development by the inflow inside the confluence region, the floor roughness of the touchdown region, and flow resistance at the rectifier should be carefully discussed to develop a reproducible axisymmetric TLV model.