{"title":"Variation of Streamwise and Vertical Turbulence Intensity in a Smooth and Rough Bed Open Channel Flow","authors":"Md Abdullah Al Faruque, Ram Balachandar","country":null,"institution":"","volume":108,"journal":"International Journal of Aerospace and Mechanical Engineering","pagesStart":2047,"pagesEnd":2051,"ISSN":"1307-6892","URL":"https:\/\/publications.waset.org\/pdf\/10002636","abstract":"An experimental study with four different types of bed\r\nconditions was carried out to understand the effect of roughness in\r\nopen channel flow at two different Reynolds numbers. The bed\r\nconditions include a smooth surface and three different roughness\r\nconditions, which were generated using sand grains with a median\r\ndiameter of 2.46 mm. The three rough conditions include a surface\r\nwith distributed roughness, a surface with continuously distributed\r\nroughness and a sand bed with a permeable interface. A commercial\r\ntwo-component fibre-optic LDA system was used to conduct the\r\nvelocity measurements. The variables of interest include the mean\r\nvelocity, turbulence intensity, correlation between the streamwise and\r\nthe wall normal turbulence, Reynolds shear stress and velocity triple\r\nproducts. Quadrant decomposition was used to extract the magnitude\r\nof the Reynolds shear stress of the turbulent bursting events. The\r\neffect of roughness was evident throughout the flow depth. The\r\nresults show that distributed roughness has the greatest roughness\r\neffect followed by the sand bed and the continuous roughness.\r\nCompared to the smooth bed, the streamwise turbulence intensity\r\nreduces but the vertical turbulence intensity increases at a location\r\nvery close to the bed due to the introduction of roughness. Although\r\nthe same sand grain is used to create the three different rough bed\r\nconditions, the difference in the turbulence intensity is an indication\r\nthat the specific geometry of the roughness has an influence on\r\nturbulence structure.","references":null,"publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 108, 2015"}