Roughness Height Measurement of Open Channel Bed Surfaces Using Structure from Motion Technology

Roughness height affects the variations in turbulent characteristics and the stress distribution within water flow.Accurate measurement of the roughness height of an open channel bed plays an important role in safeguarding benthos diversity and forecasting intermittent sediment transport occurrences.The existing techniques,such as light wave interference and laser scanning,exhibit limited anti-interference ability and involve complex operational procedures.To enhance the efficiency and accuracy of roughness height measurement and calculation,the pebble-covered bed surface within an open-channel flow experiment was considered the research object.The Structure from Motion technology was employed to reconstruct the rough bed surface terrain and calculate the roughness height.Additionally,the elevation distribution pattern and time-averaged flow velocity variation characteristics of the rough bed surface were analyzed.The results show that the pebble bed elevation follows a normal distribution pattern.Furthermore,velocity distribution conforms to the logarithmic rate calculated through this algorithm post-adjustment for the roughness height.Importantly,the utilization of this algorithm for roughness height calculation can be extended to encompass both experimental endeavors and practical engineering applications.