往复潮流作用下推移质粒径趋势形成模拟初探

SIMULATION ON SEDIMENT GRAIN SIZE TRENDS WITH BEDLOAD TRANSPORT UNDER RECTILINEAR TIDAL CURRENT

粒径趋势分析是一种用于判断海洋环境中沉积物净输运方向的方法,但是至今粒径趋势形成的物理机制尚不够清楚,因而影响了粒径趋势分析适用条件的确定。针对这个问题,本文通过建立一维、推移质、往复流(近岸潮流)条件下的数值模型,采用正演方法模拟粒度参数在输运方向上的分布,以评价沉积动力过程的影响,初步探讨粒径趋势形成的物理机制。数值模型实验的初步结果显示,水动力条件的空间差异导致的沉积物粒度参数的空间分布符合粒径趋势分析的假设,粒径趋势分析中定义的两种粒径趋势可由沉积物输运强度的空间梯度而形成,并且在沉积物净输运方向上出现的频率最高。

Grain Size Trends Analysis （GSTA） has been applied widely to marine environments to identify net sediment transport pathways. However, because the physical mechanisms for the formation of grain size trends are still not fully understood, it is not clear what conditions this technique can be applied. In the present study, we attempt to establish a forward modeling approach to model the formation of the trends. A number of numerical experiments were designed for the cases of multi-sized bedload transport by rectilinear tidal currents, and the spatial distributions of sediment grain size parameters associated with the transport processes were obtained, and the influences of sediment dynamic processes on the formation of the trends were evaluated. The experimental results are consistent with the assumptions adopted in the GSTA. The two types of grain size trends used in the GSTA could be simulated by varying spatial gradients in sediment transport rate in the net sediment transport directions.