Numerical analysis of the density current by the grid generation method and its verification by the hydraulic experiments

我们准备了两种实验通道来产生密度电流。一个是产生咸水楔，另一个是产生完全的双层电流。前一种渠道是通过将海水引入下游水槽，使海水层上升到固定高度的边界层。水道的底部相当倾斜，以便产生不均匀的水流。在那里，淡水被允许从上游流下，这样就会在下游形成盐水楔。在后者中，圆柱形喷泉排水管被设置为在几乎水平的通道中保持固定的水位，并允许恒定的水流从上游流下。将海水引入下游水箱，并安装闪光板以将海水层提高到通道底部以上。海水因此在底部逆流而上，到达上游的水箱，在那里积聚起来。通过抽取适量的海水，形成下层海水向上流动，上层淡水向下流动的完整双层流。由于进出通道的流量由管道连接，因此可以用超声波流量计精确测量。由于使用的是自来水，所以很难大幅度改变流入水量，但可以改变海水的流入水量。频道中的当前状态被录下来，并通过接口板输入个人计算机。与此同时，计算机的功能也有了很大的进步，通过相对低成本的超级计算机，计算上述复杂的密度电流已经成为可能。此外，还开发了网格生成法和CIP等优秀的计算程序，具有广阔的应用前景。这里的结果还没有达到产生足够稳定的结果，但我们认为基本的工具已经准备好了。通过将数值模拟与摄像机拍摄的密度电流现象的图像联系起来进行研究已经成为可能。少

We prepared 2 types of experimental channels to generate density currents. One was for generating salt water wedges and the other was for generating complete double-layr currents. The former channel was deviesd such that the sea water layr would rise to the bundary layr of a fixed height by introducing sea water into the downstream tank. The bottom of the channel was slanted considerably to permit generation of uneven currents. There, fresh water was allowed to flow down from the upstream so that salt water wedges would be formed downstream. In the latter, a cylindrical fountain drain was set up to keep a fixed water level in the almost horizontal channel and a constant current was allowed to flow down from the upstream. Sea water was introduced to the downstream tank and a flash board was installed to raise the sea water layr above the bottom of the channel. The sea water was thus made to fow backward in the bottom opposing the current and reach the upstream tank, where it was accumul … More ated. By draining an appropriate amount of the sea water, a complate double-layr current consisting of the up-flowing sea water in the lower layr and the down-flowing fresh water in the upper layr was generated.As the flows in and out of the channel were linked by a pipe, they could be measured accurately by an ultrasonic flow-meter. It was difficult to change the inflow greatly since tap water was used but that of the sea water could be altered. The current state in the channel was video-taped and was taken into a personal computer through the interface board. Meanwhile, functions of a computer have advanced greatly and calculation of complicated density currents such as the above has become possible by relatively low-cost super computers. Moreover, excellent calculation programs including the grid generation method and CIP have been developed offering a great prospect. The result here has not achieved to produce a sufficiently stable result yet but we consider that the basic tools are ready. It has become possible to proceed a study by linking the numerical simulation and the image of a density current phenomenon taken in by video-camera. Less