Buoyancy-Driven Exchange Flow through Double Openings with Having Multi Flow Patterns.

Abstract

Buoyancy-driven helium-air exchange flow throgh 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 flows through the double openings. 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 were evaluated in the forced flow experiment. Only the flow pattern(b)was observed in the forced flow experiment. The relationship between the entrainment ratio α and flow rate q was measured for the flow pattern(b), resulting in the entrainment characteristic curve. A new correlation for the exchange flow rate was proposed with considering the entrainment. With applying the obtained entrainment characteristic curve 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.