湿地内的水文连通对维持湿地生态系统的完整性具有重要意义。本文以Google Eearth Engine为平台支撑,在全局尺度上利用水体面积、水文连通CFV指数(Connectivity Function Value)、像元月均淹没频率对1986—2020年黄河三角洲湿地水文连...湿地内的水文连通对维持湿地生态系统的完整性具有重要意义。本文以Google Eearth Engine为平台支撑,在全局尺度上利用水体面积、水文连通CFV指数(Connectivity Function Value)、像元月均淹没频率对1986—2020年黄河三角洲湿地水文连通进行定量分析,并利用灰色关联法进行驱动力分析;在淡咸水交互的典型区域尺度上选择水文环度(α指数)、节点连接率(β指数)、水文连通性(γ指数)进行区域水文连通定量分析。结果表明:(1)湿地水体面积整体增加,水文连通CFV指数减少,研究区内发生了连通阻断,重度淹没和永久性淹没主要集中在浅海区域;(2)湿地水体面积和水文连通CFV指数均呈季节性差异,自然因素对水文连通影响大于人类活动。黄河三角洲湿地水文连通性30余年一直保持中等水平。研究结果可为黄河三角洲湿地水文连通保护与修复提供参考。展开更多
This study investigates the initialization of nonlinear free-surface simulations in a numerical wave flume. Due to the mismatch between the linear input wavemaker motion and the kinematics of fully nonlinear waves, di...This study investigates the initialization of nonlinear free-surface simulations in a numerical wave flume. Due to the mismatch between the linear input wavemaker motion and the kinematics of fully nonlinear waves, direct numerical simulations of progressive waves, generated by a sinusoidally moving wavemaker, are prone to suffering from high-frequency wave instability unless the flow is given sufficient time to adjust. A time ramp is superimposed on the wavemaker motion at the start that allows nonlinear free-surface simulations to be initialized with linear input. The duration of the ramp is adjusted to test its efficiency for short waves and long waves. Numerical results show that the time ramp scheme is effective to stabilize the wave instability at the start of the simulation in a wave flume.展开更多
文摘湿地内的水文连通对维持湿地生态系统的完整性具有重要意义。本文以Google Eearth Engine为平台支撑,在全局尺度上利用水体面积、水文连通CFV指数(Connectivity Function Value)、像元月均淹没频率对1986—2020年黄河三角洲湿地水文连通进行定量分析,并利用灰色关联法进行驱动力分析;在淡咸水交互的典型区域尺度上选择水文环度(α指数)、节点连接率(β指数)、水文连通性(γ指数)进行区域水文连通定量分析。结果表明:(1)湿地水体面积整体增加,水文连通CFV指数减少,研究区内发生了连通阻断,重度淹没和永久性淹没主要集中在浅海区域;(2)湿地水体面积和水文连通CFV指数均呈季节性差异,自然因素对水文连通影响大于人类活动。黄河三角洲湿地水文连通性30余年一直保持中等水平。研究结果可为黄河三角洲湿地水文连通保护与修复提供参考。
基金The National Natural Science Foundation of China under contract No.50779004
文摘This study investigates the initialization of nonlinear free-surface simulations in a numerical wave flume. Due to the mismatch between the linear input wavemaker motion and the kinematics of fully nonlinear waves, direct numerical simulations of progressive waves, generated by a sinusoidally moving wavemaker, are prone to suffering from high-frequency wave instability unless the flow is given sufficient time to adjust. A time ramp is superimposed on the wavemaker motion at the start that allows nonlinear free-surface simulations to be initialized with linear input. The duration of the ramp is adjusted to test its efficiency for short waves and long waves. Numerical results show that the time ramp scheme is effective to stabilize the wave instability at the start of the simulation in a wave flume.
