CHARACTERISTICS OF SURFACE WAVES WITH DEPTH-SCALE AMPLITUDE IN SHALLOW WATER UNDER SPARCELY ARRANGED STRIP ROUGHNESS

Abstract

 Turbulent open channel flow with strip roughness is one of the fundamental flows representing rough wall turbulence. This phenomenon and the relation between roughness spacing and flow resistance of relatively large water depth have been discussed so far. However, surface flow features under shallow water conditions have not been investigated in detail especially in the case of large roughness spacing. In this research, three dimensional water surface profile was quantified stereoscopically by visualizing water surface with fine sawdust. It was found that water surface shape changes complicatedly depending on hydraulic conditions. It was also found that in some cases, stationary wave patterns are generated where sharp wave peaks are arranged in a staggered manner. These stationary wave patterns have an amplitude of the same order as the water depth. Such water surface features have a similarity to those of triangular waves observed in anti-dune condition.