Numerical investigation of the flow characteristics through discontinuous and layered vegetation patches of finite width in an open channel

Ghani, Usman; Anjum, Naveed; Pasha, Ghufran Ahmed; Ahmad, Muhammad Masood

doi:10.1007/s10652-019-09669-x

Cited by 36 publications

(10 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For submerged vegetation (Figures 12C, D), the Reynolds stress reaches a maximum value near the top of the vegetation canopy, indicating that the shear stress inside the water flow near the top of the vegetation reaches a maximum value, and there is a strong shear between the top of the vegetation and the water body. This is consistent with the findings of Anjum et al (2018) and Ghani et al (2019b) on discontinuous bilayer patch vegetation. The Reynolds stress decreases rapidly from the top of vegetation to the water surface and is almost zero near the water surface.…”

Section: Vertical Distribution Of Reynolds Stress At Specific Locatio...supporting

confidence: 93%

Flow characteristics of open channels based on patch distribution of partially discontinuous rigid combined vegetation

Zhang

Wang

et al. 2022

Front. Plant Sci.

View full text Add to dashboard Cite

To clarify the flow characteristics of open channels under the combined distribution of vegetation in a patch, this study used the computational fluid dynamics tool FLUENT and the Reynolds stress model to design four combined and four discrete distribution modes under two different inundation states (submerged and non-submerged). The flow characteristics of longitudinally discontinuous rigid vegetation patches occupying half the width of the channel were numerically simulated. The numerical model is verified by indoor open channel flume experiments, and the obtained model data is in good agreement with the measured data. The results showed that: 1) The diameter of vegetation is an important factor affecting the wake structure. Under the submerged condition. 2)The submerged state, distribution pattern and combination form of vegetation are important factors that affect the distribution of flow velocity and change the structure of water flow. That is, the influence of vegetation distribution pattern on flow velocity and turbulence intensity under submerged condition is significantly weaker than that under non-submerged condition, and the flow velocity in non-vegetation area is significantly higher than that in vegetation area. The increase in the combined vegetation comprehensive stem thickness and the discrete degree resulted in an increase in the difference in flow velocity and turbulence intensity. 3) As the water flowed downstream, the flow velocity along the vegetated area continuously decreased, while it increased continuously along the non-vegetated area, and the difference in flow velocity between the two areas became more apparent. 4) The inundation state and combination characteristics of vegetation were important factors affecting the Reynolds stress of the channel location in the patch area.

show abstract

Section: Vertical Distribution Of Reynolds Stress At Specific Locatio...supporting

confidence: 93%

Flow characteristics of open channels based on patch distribution of partially discontinuous rigid combined vegetation

Zhang

Wang

et al. 2022

Front. Plant Sci.

View full text Add to dashboard Cite

show abstract

“…In submerged vegetation cases, the peaks of the vertical velocities (Uz) were clearly noticed, which was also analyzed by Barrios-Piña et al (2014) in their numerical exploration. The positive values of vertical velocities (Uz) indicate the rising flow movement, whereas negative values of depthwise velocities (Uz) indicate descending flow (Anjum et al, 2018a;Ghani et al, 2019b;Pasha and Tanaka, 2016;Zhao and Huai, 2016). The upward movement of flow was higher for the submerged vegetation cases (Case-B and Case-D) at the measuring positions.…”

Section: Depthwise Velocities (Uz)mentioning

confidence: 97%

“…In the presence of vegetation, the flow features were investigated at the specific locations (1, 2, 3, ….., 7) as shown in Figure 3. Ghani et al (2019b), andDieter et al (2014) also conducted the study of various flow properties at these locations at upstream and downstream of the patches for different arrangements. The effect of density variation showed a considerable difference in mean streamwise velocities (Ux).…”

Section: Vegetation Cases For Numerical Simulationmentioning

confidence: 99%

3D numerical modeling of flow characteristics in an open channel having in-line circular vegetation patches with varying density under submerged and emergent flow conditions

Tariq

Ghani

Anjum

et al. 2022

Journal of Hydrology and Hydromechanics

Self Cite

View full text Add to dashboard Cite

In the marine ecological system, the prime role of water management and durability of an ecosystem is being played by the vegetation patches. The vegetation patches in open channels can significantly affect the flow velocity, discharge capacity and hinder energy fluxes, which ultimately helps in controlling catastrophic floods. In this study, the numerical simulation for turbulent flow properties, i.e. velocity distribution, Reynolds stresses and Turbulent Intensities (TI) near the circular vegetation patches with progressively increasing density, were performed using the computational fluid dynamics (CFD) code ANSYS FLUENT. For examination of the turbulent flow features in the presence of circular patches with variable densities, Reynolds averaged Navier-Stokes equations, and Reynolds stress model (RSM) were employed. The numerical investigation was performed in the presence of in-line emergent and submerged patches having variable vegetation density in the downstream direction. Two of the cases were investigated with three circular patches having a clear gap to patch diameter ratio of La/D = 1 (where La is the clear spacing between the vegetation patches and D is the diameter of the circular patch), and the other two cases were analyzed with two patches having a clear gap ratio of La/D = 3. The case with a clear gap ratio (La/D = 3) showed 10.6% and 153% inflation in the magnitude of longitudinal velocity at the downstream of the sparse patch (aD = 0.8) and upstream of the dense patch (aD = 3.54), respectively (where aD is the flow blockage, in which “a” represents the patch frontal area and “D” represents the patch diameter). The velocity was reduced to 94% for emergent and 99% for submerged vegetation due to successive increase in vegetation density made by introducing a middle patch which reduced the clear gap ratio (La/D = 1). For La/D = 1, the longitudinal velocities at depth z = 15cm were increased by 319% than at depth z = 6cm at the downstream of the dense patch (aD = 3.54). Whereas it was observed to 365% higher in the case of La/D = 3. The magnitude of turbulent characteristics was observed 36% higher for submerged vegetation cases having a clear gap ratio of La/D = 1. The successive increase in the patch density reduced the Reynolds stresses, turbulent kinetic energy and turbulent intensities significantly within the gap region. The major reduction in the flow velocities and turbulent properties in the gaps provides a stable environment for aquatic ecosystems nourishment and fosters sediment deposition, and supports further vegetation growth.

show abstract

“…Similarly, increasing computational power and data storage have solved some issues, particularly those related to insufficient resolution, making scientific computing for large scale tsunami simulations increasingly accepted [42,43]. This increased interest in high-performance computing for tsunami runup has led to several inter-comparison efforts published in recent years [44][45][46][47][48][49][50][51] that add valuable transparency to high-fidelity computational approaches.…”

Section: Introductionmentioning

confidence: 99%

Forest density is more effective than tree rigidity at reducing the onshore energy flux of tsunamis: Evidence from Large Eddy Simulations with Fluid-Structure Interactions

Mukherjee

Cajas²,

Houzeaux

et al. 2022

Preprint

View full text Add to dashboard Cite

Communities around the world are increasingly interested in nature-based solutions to mitigation of coastal risks like coastal forests, but it remains unclear how much protective benefits vegetation provides, particularly in the limit of highly energetic flows after tsunami impact. The current study, using a three-dimensional incompressible computational fluid dynamics model with a fluid-structure interaction approach, aims to quantify how energy reflection and dissipation vary with different degrees of rigidity and vegetation density of a coastal forest. We represent tree trunks as cylinders and use the elastic modulus of hardwood trees such as pine or oak to characterize the rigidity of these cylinders. The numerical results show that energy reflection increases with rigidity only for a single cylinder. In the presence of multiple cylinders, the difference in energy reflection created by varying rigidity diminishes as the number of cylinders increases. Instead of rigidity, we find that the blockage area created by the presence of multiple tree trunks dominates energy reflection. As tree trunks are deformed by the hydrodynamic forces, they alter the flow field around them, causing turbulent kinetic energy generation in the wake region. As a consequence, trees dissipate flow energy, highlighting coastal forests reducing the onshore energy flux of tsunamis by means of both reflection and dissipation.

show abstract

Numerical investigation of the flow characteristics through discontinuous and layered vegetation patches of finite width in an open channel

Cited by 36 publications

References 42 publications

Flow characteristics of open channels based on patch distribution of partially discontinuous rigid combined vegetation

Flow characteristics of open channels based on patch distribution of partially discontinuous rigid combined vegetation

3D numerical modeling of flow characteristics in an open channel having in-line circular vegetation patches with varying density under submerged and emergent flow conditions

Forest density is more effective than tree rigidity at reducing the onshore energy flux of tsunamis: Evidence from Large Eddy Simulations with Fluid-Structure Interactions

Contact Info

Product

Resources

About