非恒定流冲沙模型时间比尺变态及其修正方法

Time scale distortion in a movable-bed unsteady flow test and its improvement methods

非恒定流条件下,时间比尺变态将显著影响动床河工模型试验结果的可靠性。本研究以三峡水库上游引航道非恒定流冲沙试验为例,利用模型试验确定了非恒定流时段的长度,基于对时间比尺变态影响的分析,提出了改进试验精度的措施。研究表明,有条件地改变模型时间比尺后,模型中恒定流时段长度能够更好地反映原型的真实情况。通过延长总的冲沙时间来抵消因时间变态引起的有效冲沙时间的减少,可提高模型的冲沙过程与原型的相似性。

The time scale distortion is the main factor that affects the precision and reliability of the movable-bed models in ease of unsteady flow. This paper presents a ease study on the time scale distortion problems in the physical model for the sluicing of the navigation channel upstream of the Three Goreges Dam. The impact of time scale distortion is analyzed. The time length of unsteady flow is identified in a preparatory hydraulic experiment, based on which a method to improve the precision of the test results is proposed. By conditionally modifying the time scale, the time length of steady flow in the model could better represent the process in the prototype. Extending the total length of sediment flushing time can make up for the reduction of effective flushing time and thereby enhance the similarity of sediment flushing process between the model and the prototype.