A Masjedi, M Fathi Moghadam, B Shomalnasab,
Volume 12, Issue 46 (1-2009)
Abstract
Tamarix sricta plant grows in riversides of Karun river. Outer body plant in the flood times causes decrease in water velocity, preventing erosion. One of the factors by which the hydraulic resistance is expressed is the roughness coefficient. Measurement of roughness coefficient of the existing plants in these riversides and floodplains, and surveying their effects on the velocity decrease and shear stress of the flow are important. The present research studies roughness coefficient of the plants manning existing in the riverside. Tamaix sricta was studied in non-submerged and sub-critical conditions in a flume with the length of 12.6 m, width of 0.5 m and height of 0.6 m in different velocity, discharge and depth ranges. The height of plants in this study was 35 cm with a natural arrangement in a bench of 2.8 m in length put in the bed of the flume. The total number of the experiments is 22. The results of this study show that roughness coefficients of plants are functions of velocity, depth, hydraulic radius and type of plants. Roughness coefficients in non-submerge condition change nonlinearly with changes in velocity, depth, Reynolds number, submerge depth and (VR) in natural conditions.
A. Nasseri,
Volume 27, Issue 2 (9-2023)
Abstract
The selection of precision value for Roughness coefficient (RC) is necessary to design and utilize earth canals due to the vast distribution of Echinocola crus-galli in earth canals. Therefore, the current study was conducted to evaluate roughness coefficients in earth canals with Echinocola crus-galli at the Moghan plain (in the North-west of Iran). In the network of Moghan, 42 canal sections were selected to measure vegetation density and wet weight, water flow velocity (with a flow meter), and canal cross sections (with profilimetery devices). The hydraulic characteristics were estimated after water depth measurements. The Manning roughness coefficient (n) was applied to estimate the roughness coefficient. Path analysis was applied to identify the factors affecting the roughness coefficient. Multivariate cluster analysis using Ward's method and squared Euclidean distance was applied to cluster factors affecting the roughness coefficient in canals. The results revealed that RC averaged 0.015. The path analysis showed that the wetted perimeter, crop biomass, flow cross-sectional area, flow velocity, and hydraulic radius had the highest total effect on the roughness coefficient, respectively. The factors clustering showed that two clusters were obtained in the Euclidean distance of 11. The first cluster included flow velocity, crop biomass, flow rate, and bed slope; and the second cluster included flow cross-sectional area, wetted perimeter, and hydraulic radius. The findings could be helpful for designing and operating canals in the studied or similar regions.
H. Ebrahimi Golbosi, E. Fazel Najafabadi, M. Shayannejad,
Volume 28, Issue 2 (8-2024)
Abstract
Surface irrigation is one of the most common irrigation methods. Due to the low efficiency of surface irrigation, water loss is significant in this system. It is necessary to know the characteristics and coefficients of water infiltration rate in the soil for accurate and adequate planning of surface irrigation. One of the equations used in this field is Phillip's infiltration equation. In this study, the infiltration coefficients of Phillip's equation and Manning's roughness coefficient in border irrigation are determined based on the comparison of the actual advance curve with the advance curve calculated with the dynamic wave model, and the results were compared with the double cylinder method and the two-point method of Ebrahimian et al. (5). The actual infiltration volume was obtained from the difference between the inlet and outlet volumes. The error of the mentioned method in calculating the infiltration volume was 5.53%. Meanwhile, the errors in the double cylinder and two-point Ebrahimian (5) method were 59.62% and 19.08%, respectively. In heavy soils, the longer the length of the border increases, the method is more accurate in estimating Philip's coefficients, while in light soils, the advancing time, which in addition to length is a function of permeability, input discharge, and the slope of the bottom of the bed is increased, the accuracy of the method in estimating Philip's penetration coefficients is increased.
