Evaluation and Performance Enhancement of a Pressure Transducer under Flows, Waves, and a Combination of Flows and Waves

Abstract

The performance of a pressure transducer, with its inlet attached to differing hydromechanical front ends, has been evaluated in flow flume and wave flume experiments in which laminar and turbulent flows, and regular progressive gravity waves and combinations of flows and waves, were generated. For steady laminar flows, and for waves propagating on quiescent waters, the transducer?s performance improved when the inlet was at the center and flush with a large, thin, and smooth circular horizontal end plate. This enhancement is likely to have been achieved because of the isolation of the pressure inlet from the separated flows and vortices generated by the transducer housing. Flow disturbances, generated by nearby solid structures, deteriorated the performance of the pressure transducer. However, its performance could be significantly improved by protecting the pressure inlet by a sturdy, curved perforated shield. The dynamic pressure error in this case was 2 mb at 100 cm s?1, compared to 8 mb in the absence of the shield. For turbulent flows less than 100 cm s?1, a pair of thin, circular, parallel plates, with a diameter three to four times that of the transducer housing and separation equal to the housing diameter, led to a much improved horizontal azimuthal response. At this speed the spread in the dynamic pressure, ?P, was less than 1 mb compared to 6 mb without a plate. Beyond this speed the transducer?s horizontal azimuthal response deteriorated faster. For combinations of waves and flows a relatively small ?P was found. This result is of special significance to tidal measurements of coastal waters, in which waves propagate on tidal currents.