Author(s): Delaram Kazemian; Mahmoud F. Maghrebi
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Abstract: Determination of velocity distribution profiles at hydraulic sections has always been important in river and hydraulic engineering. There are several factors which influence the velocity distribution in the channels cross-section. One of them is ice as it forms in open channels basically alters velocity distribution by increasing the magnitude of wetted perimeter and hydraulic resistance. River ice processes include complex interactions among the hydrodynamic, mechanical, and thermal processes. There are various methods to estimate distribution of isovel contours. The single point velocity measurement method (SPM) is a relatively new method of estimating distribution of isovel contours in the channels. In this paper, the verification of this method is investigated in terms of the presence of full ice cover in the rectangular channels and compared with the experimental results. An experimental program was developed at the Hydraulics laboratory of Ferdowsi University, Mashhad, Iran. A 8-m-long, 0.4-m-wide rectangular channel was used, and a simulated ice cover was installed on the bed and top of the channel. Experiments were designed in order to quantify the effects of channel-bed and ice roughness on the flow characteristics within a completely ice-covered rectangular channel. Measurements are performed from ice cover by means of a current meter attached to a vertical rigid rod supported on the channel bed. It was found that roughness had a significant impact on isovel counters below the ice cover. The results of the experiments showed that the presence of the full ice cover caused an almost symmetrical development of the velocity distribution profiles in the flow cross-section. A rough surface was shown to decrease water velocity near to the rough boundary. The minimum error occurs in the central position of the flow and as moving to the upper and lower rough boundaries the error in estimating the velocity is increased.
Year: 2020