Flow Pressure Behavior Downstream of Ski Jumps

Lauria, Agostino; Alfonsi, Giancarlo; Tafarojnoruz, Ali

doi:10.3390/fluids5040168

Cited by 16 publications

(12 citation statements)

References 24 publications

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“…It is evident that, for appendance elements on the step, the vortex was divided into two areas in the recirculating zones on the step and appendance elements. Also, the simulations indicate that numerical models can predict recirculation zones [26,[50][51][52][53].…”

Section: Flow Patternmentioning

confidence: 88%

Experimental and Numerical Study of the Effects of Geometric Appendance Elements on Energy Dissipation over Stepped Spillway

Ghaderi

Abbasi

2021

Water

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In the stepped spillway, the steps, by providing an artificial roughening bed, dissipate the flow of energy more than other types of spillways, so the construction costs for stilling basin are reduced. However, what is important in this type of spillway is increasing the effectiveness of steps in the rate of energy dissipation. The present study deals with experimental and numerical simulations regarding the influence of geometric appendance elements on the steps and its impact on the energy dissipation performances, flow patterns properties, turbulent kinetic energy, flow resistance and the Darcy roughness. The localization of inception point of air entrainment is also assessed. To this aim, different configurations are taken into account. The computational procedure is validated with experimental results and then used to test the hydraulic behavior of different geometric configurations. The results showed that the appendance elements on the steps increased the turbulent kinetic energy (TKE) values and Darcy–Weisbach friction and the energy dissipation increased significantly. By reducing the height of the elements, energy dissipation and the TKE value increase more significantly. With the appendance elements on step, the air entrainment inception locations a positioning further upstream than the flat step stepped spillway.

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Section: Flow Patternmentioning

confidence: 88%

Experimental and Numerical Study of the Effects of Geometric Appendance Elements on Energy Dissipation over Stepped Spillway

Ghaderi

Abbasi

2021

Water

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“…Figure 2 also shows that the deviation of the velocity profile from the log law line is greater for experimental run 4R as compared to experimental run 2R. The velocity profile deviation from the log law indicates the manifestation of the vortex shedding phenomenon [24] (Van Rijn and Kroon 1993). This indicates that vortex shedding increases with an increase in the submergence ratio.…”

Section: Wake Flow Analysismentioning

confidence: 90%

“…where k is von Karman's constant (the value of this constant is 0.41), and y 0 is the zerovelocity level. As per [24] Van Rijn and Kroon (1993), the value of y 0 is mentioned by Equation (2). Figure 2 indicates that the highest deviation of the velocity profile is observed for the section which is closest to the downstream end of the bar, i.e., 'T'.…”

Section: Wake Flow Analysismentioning

confidence: 99%

Analysis of Turbulent Flow Structure with Its Fluvial Processes around Mid-Channel Bar

Khan

Sharma

et al. 2021

Sustainability

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Researchers have recognized that the successive growth of mid-channel bar deposits can be entertained as the raison d’être for the initiation of the braiding process, which is closely interlinked with the growth, decay, and vertical distribution of fluvial turbulent kinetic energy (TKE). Thus, focused analysis on the underlying mechanics of turbulent flow structures in the proximity of a bar deposit occurring in the middle of the channel can afford crucial scientific clues for insight into the initiating fluvial processes that give rise to braiding. In the study reported herein, a physical model of a mid-channel bar is constructed in an experimental flume to analyze the turbulence parameters in a region close to the bar. Notably, the flow velocity plays an important role in understanding the flow behavior in the scour-hole location in the upstream flow divergence zone as well as near the downstream zone of flow convergence in a mid-channel bar. Therefore, the fluctuating components of turbulent flow velocity are herein discussed and analyzed for the regions located close to the bar. In the present study, the impact of the mid-channel bar, as well as its growth in turbulent flow, on higher-order velocity fluctuation moments are investigated. For near-bed locations, the results show the dominance of ejection events in upstream zones and the dominance of sweep events at locations downstream of the mid-channel bar. In scour-hole sections, the negative value of the stream-wise flux of turbulent kinetic energy and the positive value of the vertical flux of turbulent kinetic energy indicate energy transport in downward and forward directions, respectively. The downward and forward energy transport processes lead to scouring at these locations. The maximum turbulent production rate occurs in the wake region of the bar. The high rate of turbulence production has occurred in that region, which can be ascribed to the process of shedding turbulent vortices. The results show that the impact of the presence of the bar is mainly restricted to the lower layers of flow. The turbulent dissipation rate monotonically decreases with an increase in the vertical distance from the bed. The turbulent production rate first increases and then decreases with successive increases in the vertical distance from the bed. The paper concludes with suggestions for the future potential use of the present research for the practical purpose of examining braid bar occurrences in alluvial rivers to develop an appropriate response through training measures.

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“…According to the actual spray operation, the spray flow field model (Figure 4a) was constructed in ANSYS ICEM CFD 18.0 [37,38]. As shown in Figure 4b, the model is mainly composed of the front turbulent airflow duct, the main spray airflow duct, the rear anti-drift airflow duct, and the external spray basin.…”

Section: Simulation Methods 231 Geometric Modelmentioning

confidence: 99%

Research on Droplets Deposition Characteristics of Anti-Drift Spray Device with Multi-Airflow Synergy Based on CFD Simulation

et al. 2022

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With the increase in orchard areas and the transfer of rural labor, various air-assisted sprayers have been widely used in China. However, the problem of off-target drift still exists, which has caused pesticide waste and environmental pollution. In order to improve the droplet deposition in the canopy of fruit trees, a V-shaped anti-drift spray device with multi-airflow synergy was designed in this paper. A droplet spatial motion model was constructed, and the anti-drift mechanism of multi-airflow synergy was clarified based on particle dynamics analysis. The influences of spray pressure and V-shaped wind speed on droplet movement were investigated by Matlab, and the experimental results showed that the machine’s anti-drift effect was better when the V-shaped wind speed ranged from 15 m/s to 25 m/s. According to modern orchards with low root stock in a high-density planting, a simulation model of the flow field between the spray device and the fruit trees canopy was established by the method of computational fluid mechanics (CFD). By considering crosswind speed, V-shaped wind speed, and spray pressure, three-level simulation experiments of droplet deposition were designed for each factor using a partial multivariate orthogonal regression method. The influence of V-shaped wind speed on the droplets’ spatial distribution was analyzed, and the prediction model of the drift distance of the droplets’ deposition center was established. The simulation results showed that the three factors had a significant influence on the droplets’ deposition characteristics, and the degree from big to small was V-shaped wind speed, crosswind speed, and spray pressure. The fitting degree of the prediction model was high, and the correlation coefficient was 0.998. The anti-drift experiments of the machine were carried out, and the results showed that when the crosswind speed, the spray pressure, and V-shaped wind speed were 2.2 m/s, 0.52 MPa, and 20.8 m/s, respectively, the droplet drift rate was 29.2% lower than that of single-airflow. The drift distance of the droplets deposition center was 5.0 cm, which was consistent with the prediction model. The research can provide a basis for the design and parameters optimization of the similar sprayers used in modern orchards with low root stock in a high-density planting.

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Flow Pressure Behavior Downstream of Ski Jumps

Cited by 16 publications

References 24 publications

Experimental and Numerical Study of the Effects of Geometric Appendance Elements on Energy Dissipation over Stepped Spillway

Experimental and Numerical Study of the Effects of Geometric Appendance Elements on Energy Dissipation over Stepped Spillway

Analysis of Turbulent Flow Structure with Its Fluvial Processes around Mid-Channel Bar

Research on Droplets Deposition Characteristics of Anti-Drift Spray Device with Multi-Airflow Synergy Based on CFD Simulation

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