Study to develop a network system of snow removal channels

为了开展除雪通道网络的设计，有必要了解作为除雪通道网络基本特征的具有折射、分支、接缝等复杂几何形状的开放热流的水力特性。采用具有折光、分支和节理部分的模型明渠，在实验室进行了除雪通道的水力试验。试验研究了雪的流动机理和输运机理。精确测量了折光、分支和接头附近各断面的流速分布。在明渠的折射、分支和节理情况下，对明渠的基本特征水面形态进行了精确测量。为明确除雪通道中雪块的运移机理，分别进行了塑料球抛掷实际雪和模型雪的实验。在实验中，不同情况下的放水量发生了变化，抛掷雪块的时间间隔也发生了变化。对雪块的阻塞和顺滑机理进行了较详细的研究。在折光通道和节理通道中，在一定的抛掷时间间隔内，雪块有时会被阻塞。几乎所有的雪块都堵在了支路上。在设计除雪通道网络时应考虑到这些结果。为掌握明渠内水的流动特征，提出了明渠侧入侧出的解析模型。该模型以平均流动能守恒方程代替动量守恒方程为基础。该模型可以考虑复杂几何形状的能量损失；即河道宽度的变化以及河道的分支和接头。明渠流动的解析模型考虑了这种几何形状的能量损失，较好地解释了无雪块情况下明渠折射率表面形状和接缝的实验结果。由于大块雪块的流动本质上是不稳定的，而且水面在时间和空间上是变化的，因此测量表面形状是非常困难的。该模型还粗略地解释了带有雪块的地表形状。少

In order to develop the design of the snow removal channel network, it is necessary to understand the hydraulic characteristics of open thermal flow with complex geometries such as the refraction, the branch and the joint which are the basic features of the snow removal channel network. The hydraulic experiment the snow removal channels were carried using the model open channel which has the refraction, branch and joint parts in the laboratory. The flow mechanism and the transport mechanism of snow are investigated in the experiments. The flow velocity distributions were measured preciselyin the each section near the refraction, branch and joint parts. The shapes of the water surface, which is the basic feature of the open channel, were also measured prescisely in the cases of the refraction, branch and joints of channels.To clarify the transport mechanism of snow chunks in a snow removal channel, the experiments of throwing actual snow or model snow using plastic balls were carried ou … More t. In the experiment, the value of water discharge were changed for the several cases and the interval of throwing snow chunks were also changed. The mechanism of blocked or flowing down of snow chunkes are investigated prrecisely. In the refraction channel and joint channel, the snow chunkes were sometimes blocked in some case of the time interval of throw. Almost all snow chunks were blocked in the branch channel. These results should be taken into account when we will design the network of the snow removal channels.To grasp the flow feature of water in the channel, the analytical model calculating the open-chennel with the side inflow or outflow are presented. This model were based on the conservation equation of kinetic energy of mean flow insrtead of the conservation equation of momemtum. This model can consider the energy loss of complex geometries ; I.e. the variation of the channel width and the branch and joint of the channel.The presnt analytical model of open channel flow explains well the experimental results of the surface shape of the refraction and the joint of channel with no snow chunkes, because the model can take the energy loss of such geometry into account. The measurement of surface shape with snow chunkes are very difficult, because the flow with large chunkes are essencially unsteady and the water surface are is varied in time and space. The model also explains roughly the surface shape with snow chunks. Less