scholarly journals Discrete Element Simulation on Sand-Bed Collision Considering Surface Moisture Content

Processes ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 52
Author(s):  
Hongchao Dun ◽  
Peng Yue ◽  
Ning Huang ◽  
Jie Zhang
Keyword(s):  
Moisture Content ◽  
Discrete Element ◽  
Coastal Areas ◽  
Contact Forces ◽  
Sand Transport ◽  
Aeolian Sand ◽  
Moisture Condition ◽  
Surface Moisture ◽  
Aeolian Sand Transport ◽  
Long Time

The process of aeolian sand transport is an important mechanism leading to the formation and evolution of local landforms in coastal areas and desert lakes. For a long time, the role of surface moisture in incipient motion of sand grains by wind stress has been extensively studied but, in fact, sand-bed collision is the main mechanism in steady aeolian sand flow. At present, the lack of understanding of surface moisture content on sand-bed collision limits the application of aeolian sand transport models in wet coastal areas. In this paper, we adopt numerical simulations to discuss and analyze the effect of cohesive forces formed by surface moisture content on the sand-bed collision process based on discrete element method. High density contact forces appear with the surface moisture increasing, and form a closed structure around the edge of crater to resist the avulsion in horizontal direction. Under high moisture condition, even though the ejected sand grains saltate away from the surface, the tension forces will prevent from leaving. The ejected number trend with incident velocity shows some nonlinear characteristics due to the unequally distributed force chains and liquid bridges in the unsaturated sand bed surface.

scholarly journals Discrete Element Method simulations of the saturation of aeolian sand transport

2015 ◽  
Vol 42 (6) ◽  
pp. 2063-2070 ◽  
Author(s):  
Thomas Pähtz ◽  
Amir Omeradžić ◽  
Marcus V. Carneiro ◽  
Nuno A. M. Araújo ◽  
Hans J. Herrmann
Keyword(s):  
Discrete Element Method ◽  
Discrete Element ◽  
Sand Transport ◽  
Aeolian Sand ◽  
Aeolian Sand Transport ◽  
Element Method

scholarly journals Estimating Annual Onshore Aeolian Sand Supply from the Intertidal Beach Using an Aggregated-Scale Transport Formula

2018 ◽  
Vol 6 (4) ◽  
pp. 127 ◽  
Author(s):  
Leonardo Duarte-Campos ◽  
Kathelijne Wijnberg ◽  
Suzanne Hulscher
Keyword(s):  
Moisture Content ◽  
High Tide ◽  
Sand Transport ◽  
Wind Gust ◽  
Aeolian Sand ◽  
Aeolian Transport ◽  
Aeolian Sand Transport ◽  
Sand Supply ◽  
Transport Prediction ◽  
High Tide Line

In this paper, we explore an approach for annual-scale transport prediction from the intertidal beach, in which we aggregate the surface conditions of the intertidal beach, in particular moisture content and roughness, and use hourly monitoring data of wind speed and wind direction. For our case study area (Egmond Beach, The Netherlands), we include Argus video imagery in our analysis to assess the occurrence of aeolian sand transport. With the approach described to determine a characteristic moisture content value for aeolian transport, we obtained surface moisture values of 1.2% to 3.2% for wind average and wind gust respectively, implying that we need a quite dry beach. This indicates that the main area for aeolian transport corresponds to the upper part of the intertidal source, most likely the region between mean high tide line and spring high tide line.

scholarly journals Spatiotemporal Surface Moisture Variations on a Barred Beach and their Relationship with Groundwater Fluctuations

Hydrology ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 8 ◽  
Author(s):  
Yvonne Smit ◽  
Jasper Donker ◽  
Gerben Ruessink
Keyword(s):  
Intertidal Zone ◽  
Spatiotemporal Variability ◽  
Sand Transport ◽  
Aeolian Sand ◽  
Retention Curve ◽  
Surface Moisture ◽  
Aeolian Sand Transport ◽  
Large Fluctuations ◽  
Tide Level ◽  
Upper Intertidal

Understanding the spatiotemporal variability of surface moisture on a beach is a necessity to develop a quantitatively accurate predictive model for aeolian sand transport from the beach into the foredune. Here, we analyze laser-derived surface moisture maps with a 1 × 1 m spatial and a 15-min temporal resolution and concurrent groundwater measurements collected during falling and rising tide at the barred Egmond beach, the Netherlands. Consistent with earlier studies, the maps show that the beach can be conceptualized into three surface moisture zones. First, the wet zone just above the low tide level: 18–25%; second, the intertidal zone: 5–25% with large fluctuations. In this zone, surface moisture can decrease with a rate varying between ∼2.5–4% per hour, and cumulatively with 16% during a single falling tide; and, third, the back beach zone: 3–7% (dry). The bar–trough system perturbs this overall zonation, with the moisture characteristics on the bar similar to the upper intertidal beach and the trough always remaining wet. Surface moisture fluctuations are strongly linked to the behavior of groundwater depth and can be described by a ’Van Genuchten-type’ retention curve without hysteresis effects. Applying the Van Genuchten relationship with measured groundwater data allows us to predict surface moisture maps. Results show that the predictions capture the overall surface moisture pattern reasonably well; however, alongshore variability in groundwater level should be improved to refine the predicted surface moisture maps, especially near the sandbar.

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