Turbulent Flow Patterns on Surfaces with Different Roughness Heights Using CFD for Fixed Discharge

Understanding turbulent flow patterns over surfaces with varying roughness heights is crucial for numerous engineering and environmental applications. Numerical studies have been performed to investigate how bed roughness elements influence characteristics of turbulent flow in an open channel. Experiments are performed with various types of bed roughness elements with different roughness height to examine their impact on the velocity profile downstream of these elements under fixed water flow discharge. The numerical analysis utilized Computational Fluid Dynamics (CFD) methods. Hexahedral meshing techniques were employed to discretize the computational domain, with mesh sizes of 0.01 m and 0.05 m investigated for comparison. Validation of the CFD model against experimental data was conducted for fixed water depth and flow discharge. Findings revealed a strong correlation between the velocity distribution profiles from the numerical simulations and from experimental results downstream of the bed roughness elements. A 3D ADV (Acoustic Doppler Velocimeter) is used for finding turbulence characteristics of flow in non-uniform open-channel. In comparison to sand roughness’s, Chopan sand bed (with less roughness height) exhibits the strongest turbulence intensities in streamwise direction just next to the bed when away from the channel boundary. This study contributes to a better understanding of turbulent flow behavior over rough surfaces and provides valuable data for hydraulic engineering design and analysis.