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Calculation of Drag Coefficient and Friction Factor of Non-Submerged Rigid Vegetation in Symmetric Compound Channel, Using Direct Measurement Method
  • Mehdi Behdarvandi Askar
Mehdi Behdarvandi Askar
Khorramshahr University of Marine Science and Technology

Corresponding Author:[email protected]

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Given that the most basic issue in the study of drag coefficient is the correct and accurate measurement of force, so the use of a method that can directly measure the force of flow is very important because it can provide a more realistic analysis of drag coefficient. Also, the results obtained from this method are compared with the results obtained from other methods .This research has calculated the drag coefficient and friction factor using the direct measurement method and physical modeling in a hydraulic knife-edge flume, which is a particular type of flume capable of directly measuring the flow force. In this study, five vegetation diameters, 20, 25, 30, 40, and 50 mm, as well as two types of ordered and non-ordered arrangement, and three vegetation positions in floodplains, main channel and simultaneously vegetation in main channel and floodplain, considering five inline spacing, and three Cross line spacing between vegetation, which included a total of 451 different experiments, were examined. In this paper, the φ value is between 0.0017-0.31, and the vegetation’s Reynolds number is in the range 3512-29213. The results revealed that the method and calculations implemented in the field of drag coefficient are suitably similar to the drag coefficient obtained from the force balance equation; moreover to calculate drag coefficient and friction factor in the examined scope, C D = α 1 ( λ * ) α 2 and f T = β 1 ( Ln λ * + β 2 were achieved based on the vegetation parameter ( λ * ) . The coefficients of α 1 . α 2 . β 1  and  β 2 considering the experiments and different position and arrangement of vegetation were presented.