Numerical simulation of buoyant flow in a vertical channel for a plasma-facing component

Cooling the plasma-facing component of fusion reactors requires investigations of the characteristics of the thermofluids used in the reactors' high-temperature plasma. The working fluid (pressurized water) influences the design of advanced fusion reactors. We considered the vertical flow geometry with single-side wall heating as a flow model to examine the influence of buoyancy in the system, where buoyancy of the upward flow is produced by pressurized water. We conducted a direct numerical simulation of a vertical channel flow with a buoyancy effect. The Reynolds number, which was based on the channel half-width and friction velocity, was 1100. The values of the Prantl and Grashof numbers were 0.87 and 1.0 × 10⁸, respectively. The number of mesh points used was 1024×1024×768 in the x-, y-, and z-directions, respectively. As a result, the bulk Reynolds number based on the channel width and bulk velocity was 42,606. Turbulence parameters such as the mean flow, turbulent stresses, and the temperature statistics exhibited asymmetric profiles. This tendency was enhanced by the buoyancy effect near the wall region. Heat transfer in the cooled wall decreased at the upward flow, indicating that these phenomena under the buoyancy effect must be considered in the design of a real reactor.