Accurate velocity measurements of boundary-layer flows using Doppler optical coherence tomography
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Pulsed ultrasound Doppler velocimetry and nuclear magnetic resonance imaging are popular non-invasive measurement methods for flows of opaque fluids. The spatial and temporal resolution of these methods, however, is quite limited, and they lack accuracy, especially close to solid boundaries. In this paper, we show that solution to these problems is achieved by using Doppler optical coherence tomography (DOCT). DOCT provides simultaneous information about the fluid structure and velocity with very high spatial and temporal resolution. For benchmarking of the method we use water as the reference fluid. We show how DOCT gives a very good agreement with theory for the velocity profile, skin friction and viscosity directly from the measurement signal. The velocity profile extends from the turbulent region to viscous sublayer, and viscosity of the fluid can be calculated also from a turbulent flow with a good accuracy. Overall, DOCT is seen to be very well suited for providing new insight into boundary-layer flows, rheology and skin friction.
KeywordsVelocity Profile Optical Coherence Tomography Wall Shear Stress Skin Friction Scanning Frequency
Doppler optical coherence tomography
Pulsed ultrasound Doppler velocimetry
Nuclear magnetic resonance imaging
We gratefully acknowledge valuable cooperation network of COST ACTION FP 1005 (Fibre Suspension Flow Modelling) and ERCOFTAG SIG 43 (Fibre Suspension Flows). Academy of Finland (project Rheological Properties of Complex Fluids) is gratefully acknowledged for supporting this work. Professor Pentti Saarenrinne from Tampere University of Technology, Department of Mechanical Engineering and Industrial Systems, is acknowledged for valuable discussion.
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