Buoyancy-driven Exchange Flow through Double Openings with Having Multi Flow Patterns

Abstract

Buoyancy-driven helium-air exchange flow through double small openings was investigated. The double openings with rectangular cross section were settled side by side, in order to evaluate the interaction between the flow through the double opening. In the exchange flow experiment, the exchange flow rate and the flow pattern around the openings were simultaneously measured. Two flow patterns were formed even in the same boundary condition, i.e., (a) uncaptured flow pattern with larger exchange flow rate, and (b) captured flow pattern with smaller exchange flow rate. The entrainment effect caused the two flow patterns. In order to clarify the mechanism, characteristics of the entrainment was evaluated in the forced flow experiment. Only (b) flow pattern was observed in forced flow experiment. The relationship between the entrainment ratio a and flow rate q were measured for the flow patters (b). A new correlation for the exchange flow rate was proposed with considering the entrainment. With applying the a-q relationship for flow pattern (b) to the correlation, the exchange flow rate was predicted. It agreed with the measured value better than the conventional prediction without consideration of the entrainment.