Experimental Studies on Debris Flow with Logs Focusing on Specific Weight Difference of Log Species

There are many experimental approaches,field investigations and numerical calculations for movements of woods in a clear water and debris flow.However,kinematic conditions for accumulated logs and the interactions between a main flow and logs have not been fully evaluated.Mitigations for woods need taking into account the characteristics of tree species such as conifer and broad-leaf trees and of shapes such as root swells and crown.In the present study,we focus on the differences in specific weight of conifer and broad-leaf trees with some moisture in a sediment-water mixture flow with narrow flow width,and consider that conifer and broad-leaf tree are floating and submerged solid phase,respectively.Flume tests are conducted in steady flow of clear and debris flow over a rigid bed in order to evaluate conifer and broad-leaf tree movement in clear water and debris flow.Experimental data indicates that dimensionless transverse diffusion coefficient can be 0.1 to 0.4 and 0.3 to 0.9 in flow direction.Those diffusive characteristics seem to be independent of Reynolds number and Froude number,but dependent of bed slope,i.e.,gravity,though detailed considerations are needed to discuss about flow characteristics such as spatial eddy structures,momentum transfer induced by interactions of logs and so on.

桃枝条梢端生长及其与温度、叶水势和比叶重关系的研究

以金冠、汉瑞、红港、卡尔红为试材，探讨了桃枝条梢端生长与环境温度、叶水势和比叶重之间的关系及其昼夜变化规律。表明：在试验条件下枝条梢端生长速率与环境温度呈显著正相关，与一天中早、晚碳水化合物积累也呈显著相关，而与叶片水势变化无关。梢端生长速率昼夜总的变化趋势与气温变化相吻合，最大值出现在平均气温最高的傍晚（１６：００～２０：００），最小值出现在平均温度最低的凌晨（０：００～８：００）。在２５±０．５℃恒温条件下，梢端生长速率最大值出现后，并不随即下降，而是保持这个生长速率直至午夜，尔后逐渐降至最低值。太阳升起后，生长速率又逐渐回升。