Large eddy simulation of natural convection heat transfer and fluid flow around a horizontal cylinder

Natural convection heat transfer and fluid flow in a thermal chimney with multiple horizontally-aligned cylinders

“…Even for the simplest case of natural convection around a single heated horizontal cylinder, a numerical error of 52% to 143% in terms of velocity magnitude at the plume centerline is reported by Grafsrønningen and Jensen [36] in their large eddy simulations. This error was reduced to 15%-48% through tuning the domain boundary conditions in the large eddy simulations presented by Ma and He [17]. Under these contexts, CFD errors in the present RANS and URANS computations are both acceptable.…”

“…Numerical simulations are first carried out for the simplest case of natural convection around a single horizontal cylinder to calibrate the performance of six different RANS models in predicting the transitional behavior of buoyant plume, based on the measurement data of Grafsrønningen et al [39]. The numerical domain, mesh, boundary condition, solver setting and experimental validation have been elaborated in the previous work by Ma and He [17], and will be restated briefly in this section.…”

“…On the top boundary, pressure outlet with a static pressure of 1 atm is imposed. Such boundary condition setup has been employed and validated by Ma and He [17], Heo et al [20] and Sebastian and Shine [43]. On the cylinder surface, non-slip wall with isothermal boundary condition (T w =373 K) is specified.…”

“…Although the geometry of the computational domain seems simple, the flow physics of buoyant plume is quite complicated. Thermal plume is inherently weak and prone to instability, which will trigger transition to turbulence as it develops (Ma and He [17], Kitamura et al [24]). Moreover, plume from adjacent cylinders interacts strongly with each other and might affect the flow instability.…”

“…They stated that Nusselt number is increased notably in the transitional and turbulent regions on the cylinder surface. Ma and He [17] found through high-fidelity large eddy simulations that laminar thermal plume leaving the single cylinder accelerates subject to work done by buoyancy force, becomes unstable and transits to turbulence as it develops.…”