Effect of bed roughness on flow field around spur dyke in a rigid bed meandering channel

Effect of bed roughness on flow field and turbulence characteristics due to spur dyke in rigid bed meandering channel is presented in this study. This is an extension of authors’ earlier work. In the experiments, cement mortar, sand particles on cement mortar and small aggregates on the cement mortar surfaces are used to generate different bed roughness. 3-D velocity measurements are obtained with Acoustic Doppler Velocimeter (ADV). In a rigid bed meandering channel without spur dyke, flow concentrates near the convex bank up to inflection point in the downstream of Apex. Inflection point moves towards the upstream with increase in the roughness of the channel. The water surface slope along the center line increases with increase in bed roughness. In presence of spur dyke, the maximum velocity in the channel decreases with increase in bed roughness. When the spur dyke is located on the convex bank of Apex, the length and width of separation zone decrease with increase in bed roughness. The magnitude of turbulence intensities decreases with increase in roughness.