风速对海岸沙丘表面风沙流结构影响的实证研究

Field measurements of influence of total sand transport rate on the structure of wind-sand flow on the coastal transverse ridge

在河北昌黎黄金海岸形态典型的横向沙脊顶部，对不同风速下的风沙流结构进行了观测。结果表明：随着风速的增加，风沙流中40cm高度内的绝对输沙量增加，40～60cm高度内各层的绝对输沙量减少；相对输沙量，在0～4cm高度内减少，4～20cm高度内增加，20～44cm高度内变化较小，44—60cm高度内减少；风沙流结构模式在0～40cm高程内为指数分布，但在0～60cm高程内随风速增大由幂函数分布转变为指数函数分布，在40～60cm高程内则转变为相关性更强的多项式函数分布。风速变化对风沙流结构的上述影响，主要与随风速增加增大了沙粒的搬运高度以及气流搬运沙物质的粒度组成有关。

On the crest of typical coastal transverse ridge at Changli Gold Coast in Hebei Province, the data of structure of wind - sand flow at the different wind velocity was measured by use of field vertical anemometer and sand trap. The field measurement results showed, with the increasing of wind - velocity, the absolute sand transport rates of layers in 40cm height in the wind - sand flow increased, but the absolute sand transport rates of layers in 40 - 60cm decreased. The ratio of sand transport rate of different height layer in total sand transport rate in wind -sand flow decreased at the low height layer （0 -4cm） , but increased in the layers of 4 -20cm, nearly unchanged in the layers of 20 - 44cm and decreased in the layers of 44 - 60cm. The distribution model of the sand transport rate in the wind -sand flow could be expressed by an exponential function at the height of 0 40cm, but it changed from power function model to exponential function model in the whole height （0 -60cm） and changed into polynomial function model at the height 40 -60cm with the increasing of wind velocity. These changes had a close relationship with the transport height increasing of sands in the wind - sand flow with the increasing of wind velocity, and composition of sand grain size in the wind - sand flow.