Abstract

The effect of the emergence of quasi-periodic oscillations of particle (with size >50 mсm) concentrations in the saltation flow has been detected in similar arid conditions in desertified areas: (1) using high-speed video in Astrakhan region (2009); (2) by acoustic method in the Republic of Kalmykia (2021). During the field experiments were revealed characteristic low frequencies (<50 Hz), which is associated with the peculiarities of the microrelief shape. More high frequences (>50 Hz) have been observed also. The appearance of these frequencies is determined by changes in the saltation cycle in heterogeneous topography. Such processes is simulated in a numerical experiment using the OpenFoam package. There are demonstrated the characteristic frequencies of changes in the number of particles (from 10 to 200 Hz) in the saltation flow over the surface ledge of the ripple type. Numerical experiments include analysis of frequency characteristics of particle concentration changes in the flow behind the ledge. Spectral analysis of data of numerical realizations of the saltation flow at variation of boundary parameters and height of the obstacle shows that the characteristic frequency or frequencies change and are close to those observed in the experiment. Input parameters such a models can be adjusted with such analysis.

中文翻译：

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论跳动流周期模态的出现条件

摘要

在荒漠化地区的类似干旱条件下，已检测到跃移流中颗粒（尺寸 > 50 mсm）浓度出现准周期振荡的影响：（1）在阿斯特拉罕地区使用高速视频（2009 年）；(2) 在卡尔梅克共和国采用声学方法（2021 年）。在现场实验中发现了特征低频（<50 Hz），这与微浮雕形状的特殊性有关。还观察到了更高的频率（> 50 Hz）。这些频率的出现是由异质地形中跳跃周期的变化决定的。使用 OpenFoam 软件包在数值实验中模拟此类过程。展示了波纹型表面凸缘上跃动流中粒子数量变化（从 10 到 200 Hz）的特征频率。数值实验包括分析壁架后面流中颗粒浓度变化的频率特性。对边界参数和障碍物高度变化时跳动流数值实现数据的频谱分析表明，特征频率发生变化，并且与实验中观察到的结果接近。可以通过此类分析来调整模型等输入参数。