Laboratory experimental results on the turbulent flow characteristics, measured by an
acoustic Doppler velocimeter, over loose rough boundaries at the near-threshold of motion
are reported. The primary endeavor was to investigate the response of the turbulent flow
field, having zero-pressure gradient, to the uniform gravel beds at the near-threshold of
motion with reasonably wide range of relative roughness ε∕ h (0.02< ε∕ h< 0.15; where ε=
Nikuradse's equivalent roughness and h= flow depth). Five uniform gravel sizes, ranging …

Laboratory experimental results on the turbulent flow characteristics, measured by an
acoustic Doppler velocimeter, over loose rough boundaries at the near-threshold of motion
are reported. The primary endeavor was to investigate the response of the turbulent flow
field, having zero-pressure gradient, to the uniform gravel beds at the near-threshold of
motion with reasonably wide range of relative roughness ε/h (0.02< ε/h< 0.15; where ε=
Nikuradse's equivalent roughness and h= flow depth). Five uniform gravel sizes, ranging …