Frictional drag measurements of large-scale plates in an enhanced plane channel flowcell

Abstract

This paper describes the design of an enhanced, plane channel, flowcell and its use for testing large-scale coated plates (0.6 m × 0.22 m) in fully developed flow, over a wide range of Reynolds numbers, with low uncertainty. Two identical, hydraulically smooth plates were experimentally tested. Uniform biofilms were grown on clean surfaces to test skin friction changes resulting from different biofilm thickness and densities. A velocity survey of the flowcell measurement section, using laser Doppler anemometry, showed a consistent velocity profile and low turbulence intensity in the central flow channel. The skin friction coefficient was experimentally determined using a pressure drop method. Results correlate closely to previously published regression data, particularly at higher speeds. Repeated measurements indicated very low uncertainty. This study demonstrates this flowcell’s applicability for representing consistent frictional drag of ship hull surfaces, enabling comparability of hydrodynamic drag caused by surface roughness to the reference surface measurements.

Keywords:

• Hydrodynamic drag
• flowcell
• turbulent flow channel
• calibration
• skin friction curves
• biofouling

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

The work was supported by the European Union Seventh Framework Programme (FP7-OCEAN-2013) project SEAFRONT under grant No: 614034 (MA and ASC) and the US Office of Naval Research under grant N00014-16-1-2988 (ASC and JAF).