Effect of Roughness on Conveyance of Channel
- August 13, 2018
- Posted by: RSIS
- Categories: Civil Engineering, Mathematics
International Journal of Research and Scientific Innovation (IJRSI) | Volume V, Issue VIII, August 2018 | ISSN 2321–2705
Effect of Roughness on Conveyance of Channel
Dr. Birendra Kumar Singh
Civil Engineering Department, Birla Institute of Technology, Mesra, Ranchi-835215 (Jharkhand), India
Abstract: – The effect of surface roughness (i.e. Manning’s roughness coefficient, Darcy Weisbach resistance coefficient) is studied on conveyance or channel carrying capacity of channel. Also the effect of roughness due to size of the roughness material is seen on conveyance on channel. Velocity is much reduced with respect to Darcy Weisbach resistance coefficient as compared to Manning’s roughness coefficient.
Keywords: Surface roughness; Size of the roughness material; Mean depth of flow; Conveyance; Mean velocity of flow Flume.
I. INTRODUCTION
Darcy Weisbach resistance coefficient is found from f= 8gRs/V2 and n=1.49R2/3S1/2/V.
f = Darcy Weisbach resistance coefficient, g=Acceleration due to gravity into account because depth of flow increases due to roughness. R= Hydraulic radius to be taken into account because roughness is more effective in lesser depth of flow and hydraulic radius is lesser than mean depth of flow. S= Channel slope. V=Mean Velocity of flow in m/sec. n=Manning’s roughness coefficient. There is much reduction in mean velocity of flow for Darcy Weisbach resistance coefficient. Mean depth of flow depends upon mean velocity of flow hence mean depth of flow is less and discharge of flow is less. Hence, conveyance is lesser for Darcy Weisbach resistance coefficient as compared to conveyance of a channel found with respect to Manning’s roughness coefficient.
II. EXPERIMENTAL SETUP & PROCEDURES
Data were obtained for 0.75-inch roughness bed.
Flume – The flume is open and 1.168m wide and 9.54m long. Roughness bed was constructed by smearing masonite boards with fiberglass resin. The boards were then screwed to the bed of the flume.
Experimental Procedure – Five to seven flows were measured for three different slopes (2, 5 and 8%). At each flow, depth was gaged at a single cross section, so that mean flow and channel properties could be calculated.
