Numerical study on the drag characteristics of rigid submerged vegetation patches

2021 ◽  
Vol 33 (8) ◽  
pp. 085123
Author(s):  
Mengyang Liu ◽  
Wenxin Huai ◽  
Bin Ji ◽  
Peng Han
Keyword(s):  
Numerical Study ◽  
Submerged Vegetation ◽  
Vegetation Patches

scholarly journals Riparian Vegetation Density Mapping of an Extremely Densely Vegetated Confined Floodplain

Hydrology ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 176
Author(s):  
István Fehérváry ◽  
Tímea Kiss
Keyword(s):  
Riparian Vegetation ◽  
Woody Species ◽  
Submerged Vegetation ◽  
Vegetation Types ◽  
Vegetation Density ◽  
Vegetation Zone ◽  
Density Mapping ◽  
Vegetation Zones ◽  
Branch Density ◽  
Vegetation Patches

The most crucial function of lowland-confined floodplains with low slopes is to support flood conveyance and fasten floods; however, obstacles can hinder it. The management of riparian vegetation is often neglected, though woody species increase the vegetation roughness of floodplains and increase flood levels. The aims are (1) to determine the branch density of various riparian vegetation types in the flood conveyance zone up to the level of artificial levees (up to 5 m), and (2) to assess the spatial distribution of densely vegetated patches. Applying a decision tree and machine learning, six vegetation types were identified with an accuracy of 83%. The vegetation density was determined within each type by applying the normalized relative point density (NRD) method. Besides, vegetation density was calculated in each submerged vegetation zone (1–2 m, 2–3 m, etc.). Thus, the obstacles for floods with various frequencies were mapped. In the study area, young poplar plantations offer the most favorable flood conveyance conditions, whereas invasive Amorpha thickets and the dense stands of native willow forests provide the worst conditions for flood conveyance. Dense and very dense vegetation patches are common in all submerged vegetation zones; thus, vegetation could heavily influence floods.

Impacts of turbulent flow over a channel bed with a vegetation patch on the incipient motion of sediment

2018 ◽  
Vol 45 (9) ◽  
pp. 803-816
Author(s):  
Reza Shahmohammadi ◽  
Hossein Afzalimehr ◽  
Jueyi Sui
Keyword(s):  
Experimental Study ◽  
Reynolds Stress ◽  
Streamwise Velocity ◽  
Stress Pattern ◽  
Submerged Vegetation ◽  
Incipient Motion ◽  
Vegetation Patch ◽  
Motion Process ◽  
Velocity Turbulence ◽  
Vegetation Patches

In this experimental study, the effect of a submerged vegetation patch with individual plants on the incipient motion of sediment has been examined. Results showed that a vegetation patch in the channel bed affected the incipient motion process of sediment and resulted in significant impacts on flow velocity, turbulence intensities, turbulent kinetic energy, and Reynolds stress distribution. The presence of vegetation patches completely change vertical distribution of velocity and Reynolds stress pattern and leads to negative Reynolds stress values in zones with negative velocity gradient. In the presence of a vegetation patch, threshold cross-averaged streamwise velocity is 20% smaller than that without vegetation, but because of the occurrence of the preferential path around the sheath section, the near-bed streamwise velocity is the same as without vegetation. Also, vegetation increases turbulence intensity, thus encouraging sediment motion. In the presence of a vegetation patch, the Shields parameter is, on average, one and half times that of without vegetation over the bed.

Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Lennard Jones

Numerical simulation of the tree higro-thermal response in forest fire environment

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  
Keyword(s):  
Forest Fire ◽  
Numerical Study ◽  
Thermal Response ◽  
View Factor ◽  
Tree Model ◽  
Pine Tree ◽  
Surface Temperatures ◽  
Fire Environment ◽  
Fire Front ◽  
Heat Exchanges

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.

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