Study of Maximum Relative Amplitude Formation Due To Vortex Shedding Of Submerged Obstacles

In open channels, when water flows through obstacles, boundary layer on upstream and the separation of streamlines on downstream of the obstacles and therefore vortex shedding will occur. The overlap of vortex wave reflecting from the walls of channels may produce surface waves which are perpendicular to the direction of the flow. When the vortex frequency of obstacles and flow natural frequency become equal, resonance will occur. The purpose of current study was to determine the relative amplitude of transverse waves in submerged flow while resonance occurs. The submerge processing started from 0% into max percent while the waves are visible. This research included 71 tests in different prism obstacles with two style of water strike toward edge and face of the obstacles and in two different inline and staggered arrangements in two modes of transverse waves. The obstacle distances were 120 millimeters from each other. The maximum relative amplitude of the flow depth was 0.2 for mode one and 0.14 for the second modes of transverse wave. By using software and statistical analysis, a formula was suggested for determining the maximum relative amplitude of the flow depth. Finally, the data determined by suggested formula were compared with the laboratory data.