风沙跃移运动发展过程的离散动力学模拟

采用类似分子动力学的离散方法对二维风沙跃移过程运用高性能并行计算进行理论模拟。在本模拟模型中,考虑了沙粒与床面的碰撞、跃移沙粒与气流的相互作用等基本力学过程组成的复杂系统。通过并行运算技术使计算沙粒数达到72000的巨量计算得以实现。初步结果显示：自然跃移运动的基本特征如风沙流层内输沙率廓线可以较为成功的得以模拟。     

Modern observations of floccule ripples: Petitcodiac River estuary,New Brunswick,Canada

Mud floccule ripples, small mud rip‐up clasts, erosional scars and tool marks are reported for the first time from the macrotidal Petitcodiac River estuary, New Brunswick, Canada. The ripples occur on the intertidal flats and are ebb‐oriented. Observations have been conducted during the spring low tide at high‐river and low‐river discharge. Floccule ripples forming during the high‐river flow are characterized by increased silt fraction, low relief and sinuous to lunate form. The ripples forming during the low flow are clay‐dominated, have very low relief and are characterized by narrow straight ridges and patchy distribution. The preserved mud floccule ripples manifest in interbedded silt‐rich and clay‐rich deposits with parallel, wavy, lenticular and current‐ripple lamination. Presented floccule ripples are current‐generated, non‐episodic in nature and are sedimentologically characterized. The ripple origin is constrained by morphometric and grain‐size analyses, and observed hydraulic processes. It is confirmed that mud floccule ripples originate under a similar range of hydraulic parameters as documented in previous flume studies. This study confirms application of work conducted in recent decades on mud‐dominated marginal‐marine environments and helps with understanding of properties and distribution of fine‐grained sediments in tidally influenced settings.