Investigation of Roughness Coefficient for Selected Rivers Of Khorasan e Razavi
2013
Abbasi, Ali Akbar
One of the important problems in river engineering is determination of flow resistance. Various empirical methods have been suggested for estimating bed roughness coefficient by researchers which most of these methods can only be applied to Special Rivers. Given the importance of this factor, determine the appropriate amount, have effective role to accurately estimate of velocity and flow rate. Since the relations are represented mainly based on laboratory data or developed for specific rivers or streams, which are used within the same Specifications. In this study, five selected rivers of Khorasan (Ferizi, Kardeh, Shandiz, Radkan and Torogh) have been considered to determine flow conditions and river geometry data. Then by using the measured values of roughness coefficients, estimate the appropriate relationships. To achieve the desired objectives, flow must be uniform, turbulent, hydraulically roughness and without vegetations or obstacles and bed forms, until could ignore from effects of these cases and could assume that the flow resistance is only due size of bed material. The result showed in addition bed material the hydraulic behavior is effective on calculating for flow resistance coefficient. For this reason after the dimensional analysis the flow resistance coefficient (n) will be inversely proportional to the Froude number. Finally, relationships were developed for each river that can estimate the flow resistance coefficient with more accuracy. Besides relationships based on hydraulic radius for estimating roughness coefficients were presented.
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