A study on buoyancy-driven flows in two series-connected chambers

An experimental study on buoyancy-driven flows in two series-connected chambers in a homogeneous environment is presented in the paper. Two chambers have the same height and a common divider. Two chambers are connected to the outside homogeneous environment through their own openings and the common shared divider only has one connection opening. A buoyancy source is placed in a chamber, denoted as the forced chamber, which is connected to the other chamber without any buoyancy source, denoted as the unforced chamber. This paper presents a theoretical approach and experimental results on buoyancy-driven flows, when the forced chamber is located downstream. It is denoted as the pull-type buoyancy-driven flows. The application of this research is related to natural ventilation of buildings. Theoretical analysis is based on plume theory, but salt water and clean water are used to simulate the buoyancy force difference in the experiments. However, the coordinate system is consistent in the whole paper. The theoretical model shows that series-connected openings of partitioned buildings have the same effect for both wind-driven and pull-type buoyancy-driven flows. This research shows that the same size opening at a different level on the unforced side wall almost has the same effect on the flow rate, and the total effective area takes every opening at a different level into account equally. When the openings in the forced chamber are fixed, the opening area ratio in the unforced chamber plays a certain role on the flow rate. When this opening area ratio is larger than one, the flow rate in the space changes less than 10%. When this opening area ratio is less than one, the flow rate starts to reduce dramatically. The same reduced area size at any one of connection openings in this space is also investigated.

► A theoretical analysis approach and experimental results are presented.
► The light attenuation technique is applied to measure the density change.
► Series-connected openings have the same effect for wind-driven and pull-type flows.
► The same size unforced side wall opening at a different level almost has the same effect on the flow.
► The opening area ratio in the unforced chamber plays a certain role on the flow.