野外非稳态跃移风沙运动及其输沙率的时空变化研究

Saltation transport in the near surface layer is the main cause of wind erosion and dust emission that forms dust storm. Understanding of the mechanism of saltation transport and is the key to wind erosion and dust storm prediction and control. Majority of the saltation models now available are established on the hypothesis of stationary flow and steady saltation and predict the sand transport rate based typically on the shear velocity, which is the primary reason of their poor performance for predicting field saltation transport rate. This project will implement a research scheme of in-situ measurement aided by wind tunnel experiment and numerical simulation to study the spatiotemporal variability of saltation transport rate and its relevance to turbulence statistic and structure feature. It is expected that the variations of saltation response and transport rate will be revealed quantitatively as a function of primary parameters of fluctuating wind speed. Based on the above research, saltation transport rate model involving statistical features will finally be established to predict field saltation transport rate more accurately.

近地表跃移风沙流是导致土壤风蚀和粉尘扬起形成沙尘暴的主要原因，对跃移输沙机理、过程的正确认识和对输沙率的准确预测也是土壤风蚀和沙尘数值预报及其防治的关键。现有输沙模型大多基于定常来流风场、稳态输沙过程而建立，并以摩阻风速（平均风速）为主要参数进行输沙率预测，是导致对野外输沙率预测误差的主要原因之一。本项目拟采用野外观测为主、辅以风洞实验和数值模拟的方案，研究野外实际非平稳输沙率的时空变化，揭示其与湍流风场统计参量、结构特征之间的关系，提炼出实际跃移输沙率随流场主要脉动参数的变化规律，进而建立考虑风场脉动特征的输沙率模型。

在甘肃民勤地区开展近地表风沙流中风速与输沙率的实时同步野外观测。基于野外观测数据分析给出的影响风沙流输沙率的时间尺度和风速脉动方差变化范围，数值模拟周期风速下风沙流输沙过程，进而提炼给出考虑风速脉动特征的输沙率预测公式，该公式不仅包含平均风速影响，同时引入风速变化的周期/频率和幅值作为参数，改进了已有的仅基于平均风速预测输沙率的方法。将该模型推广至火星条件不仅再现火星存在低风速情况下的输沙，还发现地球与火星输沙率并不具有相同标度关系。为模拟实际野外观测到的条带状输沙结构，将一维风沙流模型推广至三维，初步实现野外风沙流的大涡模拟和统计分析，为进一步研究奠定基础。项目发表论文3篇，其中sci论文2篇，核心期刊论文1篇，准备投稿论文2篇，已提交软件著作权申请一项，负责人在项目执行期间晋升为副教授。