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

我们制备了两种实验通道来产生密度电流。一种是产生盐水楔，另一种是产生完整的双层流。前一个通道的设计是通过将海水引入下游水箱，使海水层上升到固定高度的中间层。通道底部倾斜得很大，以允许产生不均匀的电流。在那里，淡水被允许从上游流下来，这样盐水楔就会在下游形成。在后者中，设置了一个圆柱形的喷泉排水管，以保持几乎水平的通道中的固定水位，并允许恒定的水流从上游向下流动。将海水引入下游水箱，并安装防水板以将海水层提升到通道底部以上。这样，海水就在底部逆流而上，到达上游的水箱，在那里被冲走。 ...更多信息 过时了通过排放适量的海水，形成下层海水上升、上层淡水下降的双层流，并通过管道将进出通道的水流连接起来，利用超声波流量计可以准确测量。由于使用的是自来水，因此很难大幅改变流入量，但海水的流入量可以改变。通道中的当前状态被录像，并通过接口板进入个人计算机。与此同时，计算机的功能已经大大地进步，并且诸如上述的复杂密度电流的计算已经可以通过相对低成本的超级计算机进行。此外，还开发了包括网格生成方法和CIP在内的优秀计算程序，具有广阔的前景。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异重流现象图像相结合进行研究成为可能。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