LAUSR

Abstract The impact of the external thermal stratification on the flow behavior and the mass flow rate in an open ended vertical channel with one side uniformly heated is investigated experimentally and numerically. Both experimental and numerical studies show that the increase of the external stratification lowers the velocity and the mass flow rate but also displaces the transition height at a lower location in the channel. The numerical model was used to study the cases of weak and negative thermal stratifications which are barely achievable in non-controlled experimental laboratory conditions but are common in the atmosphere. Different flow regimes are identified with flow being fully laminar when the stratification is weak or negative and flow being transitional to turbulent for higher stratifications. Finally, the numerically obtained mass flow rates with the various external thermal stratifications are shown to be in excellent agreement with a theoretical model developed in a previous work.