انجمن هیدرولیک ایران نشریه علمی هیدرولیک 2345-4237 3 3 2008 11 21 Effects of Bed Roughness Shape on the Length of Hydraulic Jump تاثیر شکل زبری بستر بر طول پرش هیدرولیکی در کانال های مستطیلی 29 40 85472 10.30482/jhyd.2008.85472 FA محمود شفاعی بجستان دانشگاه شهید چمران اهواز 0000-0003-3688-9561 کبری نیسی Journal Article 2008 03 22 In this study, effects of shape of roughness elements on the length of hydraulic jump have<br />been investigated experimentally. For the purpose of this study, prismatic roughness elements<br />with different shapes (rectangular, triangular, circular, lozenge and hexangular) have been<br />tested in a rectangular flume 7.5m long and 30cm wide. Experiments were performed in the<br />hydraulic laboratory of Shahid Chamran University, Ahwaz, Iran. The roughed elements are<br />glued on the bed of flume downstream of ogee spillways in such a way that the incoming<br />water jet is just above the element surface. It should be noted that in previous studies the<br />rough elements have been tested such that the incoming jet was at the same level of the<br />element bottom so the elements act as baffle blocks. Each rough element was tested under<br />different flow conditions. The incoming Froude number was in the range of 4.5 to 12. During<br />each test the water surface profile, the roller length and the jump length were measured. In<br />few tests the longitudes and vertical flow velocity were measured. The results indicate that the<br />presence of rough element can reduce the hydraulic jump length and the amount of the<br />reduction depends on the Froude number and the roughness shape. The lozenge element shape<br />was found to produce lesser jump length (up to 40% of the smooth bed jump). Relations have<br />been presented in this study to predict jump length, roller length and the amount of energy<br />which is dissipated. Comparison of this study with previous results reveals that using the<br />rough element can reduce the hydraulic jump as much as the block elements do, and the rough<br />element can not cause separation of flow which might be subject to cavitations. https://jhyd.iha.ir/article_85472_18e89ec0564005f80165c79f0a1cb9d5.pdf