A study on ceiling jet flow behaviour

对在无约束顶板下流动的顶板射流的流动特性进行了一系列实验研究。在实验结果的基础上，考虑倾角的影响，建立了沿径向距离的温升降速、厚度及分布的经验公式。为了研究火源形状对顶棚射流的影响，采用矩形火源。通过与方形火源的温升衰减和温度分布的比较，确定了温升衰减随径向距离的典型差异。通过对矩形横截面水平隧道的温升和速度的详细测量，考察了侧壁对顶棚射流的影响。建立了沿隧道水平方向计算顶棚射流温升和速度下降的经验关系式。

A series of experiments that focused on the flow behavior of ceiling jet, which flows under an unconfined ceiling, were conducted. Based on the experimental results, empirical formula for temperature rise and velocity decreasing, thickness and distribution against radial distance were developed considering the effect of inclination angle.To examine the effect of fire source shape to the ceiling jet flow, the rectangular fire source was employed. By comparing the temperature rise decreasing and temperature distribution with them obtained by a square fire source, typical difference for temperature rise decreasing against radial distance was confirmed. Detailed measurements of the temperature rise and velocity in a horizontal tunnel with a rectangular cross section were conducted to examine the effect of side wall on the ceiling jet. Empirical relationship to estimate the decrease in the ceiling jet temperature rise and velocity along the horizontal axis of the tunnel was developed.