Document Type : Research Article
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Abstract
This research presents recent advances on morphodynamic modeling over gravel dunes. Experiments were carried out on flow over 4 different dunes developed in 12m flume at Institute of Hydraulic Engineering and Water Resource Management of Technical University of Graz, Austria. Dunes are developed in the height of 4,6 and 8 cm and in wavelength of 1m with 2 different particle sizes (6 and 13 mm) and also two different lee angles (38 and 8 degree). The separation of flow over gravel fixed dunes is investigated by Acoustic Doppler Velocimetry (ADV) and Particle Image Velocimetry (PIV) and to compare the experimental results with numerical models over dunes, the 3D numerical model (SSIIM) is applied in this study. The results show that for the same two dunes under the same velocity but different flow depths, larger separation occurs under lower flow depths and a decrease in dune height causes a reduction in length of separation. Moreover the separation zone has a strong relation with lee angle and in the situation of low lee angle no flow separation was detected. Finally the result reveal that numerical model successfully simulate flow over dune in compared with ADV and PIV data. Although ADV application near the bed indicates probably weak performance for high discharge and low water depth of dune No.4, PIV results present more agreement with the numerical model in this region.
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