Characteristics of a buoyant plume in a channel with cross-flow

Abstract

We present data from direct numerical simulation (DNS) of a buoyant plume in a channel with cross-flow. The plume originates from a line heat source at the bottom channel wall, impinging the top wall and propagates downstream and/or upstream based on the strength of the cross-flow. We study the critical velocity, defined as the minimum cross-flow velocity which prevents negative backlayering length from occurring. For cross-flow velocities higher than the critical velocities, all the plume generated from the source would be forced downstream and the location of the backlayering front would move downstream. We also visualise the structure of the plume for different source Reynolds number, which indicates that the backlayering is thicker at lower source Reynolds numbers. The thicker backlayering acts like as a blockage, which influences the cross-flow. In addition, an investigation into the relationship between critical velocity, source Reynolds number and the heat release rate has been carried out. A one-third power between the heat release rate critical is found, which is in good agreement with previous studies. For a fixed heat release rate, the critical velocity increases with increasing source Reynolds number. However, the critical velocity approaches an asymptotic value when the source Reynolds number is sufficiently high.