Energetic motions in turbulent partially filled pipe flow

Turbulent partially filled pipe flow was investigated using stereoscopic particle imaging velocimetry in the cross-stream plane for a range of depths at nominally constant Reynolds number 30 000 (based on bulk velocity and hydraulic diameter). Unlike full flow, which is axisymmetric, turbulent kinetic energy exhibits significant azimuthal (and radial) variation. Proper orthogonal decomposition (POD) fluctuating field indicates that leading-order POD modes occupy “corners” where free surface meets wall these modes, are closely linked to instantaneous cellular structure, contribute nearly quarter overall energy. Spatial distributions large- very-large-scale motions (LSMs/VLSMs) estimated from pseudo-instantaneous three-dimensional fields reveal preference sides (in close proximity surface) bottom quadrant pipe. That LSMs VLSMs shown populate region spanning width surface, as well corners, strongly suggests there dynamical connection between LSMs/VLSMs structures can explain spatial redistribution