THE FLOW FIELD AND ITS DYNAMICS PROCESSES OF PYRAMIDAL DUNE
THE FLOW FIELD AND ITS DYNAMICS PROCESSES OF PYRAMIDAL DUNE
复制标题
金字塔形沙丘流场及其动力学过程
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Zhang Weimin Qu Jianjun Dong Zhibao Li Xiaoze
中科院分区：
文献类型：
--
作者：
Zhang Weimin Qu Jianjun Dong Zhibao Li Xiaoze
本文通过对敦煌莫高窟顶部金字塔形沙丘的风洞实验和沉积结构测定，旨在重建金字塔形沙丘表面的流场，进一步探讨沙丘形成和演化的动力学过程。莫高窟顶金字塔形沙丘是在NW、NE、SW三个方向的风作用下形成的，NE、SW风向将沙丘的主臂吹出E-NW向，WN风向形成沙丘的次臂，金字塔形沙丘的动力学过程是主臂变形产生次臂。金字塔形沙丘特有的“聚流循环”和“散流循环”的作用是沙丘顶部形成的关键动力。在金字塔形沙丘的形成过程中，水流方向与沙丘脊的有效夹角必须大于30°。在此条件下，沙丘背风面出现一个反向加速流速带，使沙物质从沙丘脊两侧向上发育。否则，沙丘将纵向发展。从风成地貌和演变过程的角度，认为复杂沙丘之间存在着某种内在联系。在主、次支（脊）演变过程中，多方向风场的一种组合可以形成一种适合地面环流的地形。当风场发生变化时，沙丘类型将演变为与地面相对环流相适应的沙丘类型。反过来，地形也是决定环境风况的重要因素。提出了将沉积构造测定与风洞实验相结合的综合研究方法，是一种比以往单一过程研究更全面、更系统、更深入的研究方法。
The paper, based on wind tunnel experiment and sedimentary structure determination to the pyramidal dunes on top of Mogao grotto of Dunhuang, aims at re establishing the flow field of pyramidal dune surface and further discussing the dynamics processes of dune forming and evolution. \ \ The pyramidal dunes on top of Mogao grotto are formed in condition of wind blowing from three directions including NW, NE and SW. NE and SW wind directions have blow out the dune's main arm in E-NW direction, and WN wind direction has formed the secondary arm of it. The dynamics processes of pyramidal dune are that main arm deforms then produce secondary arms. The acting of special assembling circulation" and diffusing circulation" of pyramidal dune is the key force for dune's top forming. In the forming of pyramidal dune, the effective angle between flow direction and dune ridge must be more than 30°. Under this condition, an inverse accelerating flow velocity belt appears at leeward side of dune, which makes sand materials develop upward from the two sides of dune ridge. Otherwise, the dune will develop longitudinally. In the views of eolian landforms and evoluting processes, it is thought that some internal relations are existed among complicate sand dunes. One combination of multi direction wind regime can form a landform suitable to surface circulation in the processes of main and secondary arms (ridges) evoluting. When wind regime changes, the type of sand dune will evolute to another type suitable to the relative surface circulation. In return, landform is also the important factor determining the environmental wind regime. The integrated research combining sedimentary structure determining and wind tunnel experiment is suggested to be a more all round, systematic and further method than before single process research.