Boundary effects on the drag coefficient and average Nusselt number of a sphere in SCW: A comparative study

A comparative study on cold supercritical water (SCW) passing over a hot sphere is carried out using the particle-resolved direct numerical simulation (PR-DNS) to examine the wall effects. Different working conditions are considered to obtain the drag coefficient (Cd) and average Nusselt number (Nu) of hot spheres in SCW whose physical properties significantly change with temperature and pressure. The effects of wall factors on Cd and Nu under two different boundary conditions, namely a stationary one for the fluidized sphere problem and a moving one for the settling sphere problem, are compared and discussed. Numerical results show that Cd and Nu of a sphere in SCW cannot fit the previous correlations for conventional fluids well. Therefore, these correlations are improved for SCW, which are good tools to understand the basic knowledge of SCW.