We carried out the miniature experiment of the 1/3 scale in order to suggest techniques to predict mass flow rate, temperature, cross-sectional shape of the buoyant jet at the end of eaves soffit. These techniques are necessary for a calculation of the mass flow rate of the buoyant jet rising into the atrium connected to the fire room. In experiment, we installed the sidewall under eaves to grasp a property change of the smoke in the route that reaches from an opening the end of eaves in detail. In this experiment, we got the following information.
(1)Change of the property of the jet from opening to the end of eaves
(When the width of the jet is the same as opening width up to the end of eaves)
·As for the cause of the increase of mass flow rate at the end of eaves, the entrainment in the vertical direction before colliding with eaves is dominant. That in the horizontal direction is small so as to be able to ignore it.
·The thickness of the jet at the opening and the end of eaves differ greatly. When eaves are installed in the opening upper end, thickness at the end of eaves is reduced to half. When the vertical distance from the opening upper end to eaves is long, the thickness at the end of eaves may thicken from an opening.
·The temperature of the jet is affected by the heat loss to wall surfaces and the entrainment.
(When the width of the jet at the end of eaves spreads than opening width)
·We cannot ignore the effect of the entrainment in the horizontal direction when the jet spreads radially.
·The thickness of the jet at the end of eaves increases in comparison with the case the width of the jet at the end of eaves is the same as that of the opening.
·The temperature of the jet at the end of eaves decreases in comparison with the case the width of the jet at the end of eaves is the same as that of the opening.
(2)Suggestion of prediction expression
Based on the above-mentioned result, we suggested an expression to predict the mass flow rate, thickness, temperature at the end of eaves from opening information.
·The mass flow rate of the jet can be similar in a line fire source model. The entrainment in the horizontal direction when the jet spreads radially is evaluated in the width of the jet to the power of 4/3.
·The temperature is almost predictable by consideration the heat loss and the entrainment of the fresh air.
·The thickness is almost predictable by the adoption of the concept of the density current.
