Image thresholding process for combining photometry with intrusive flow instruments

ABSTRACT

A novel photometric thresholding process for the study of opaque, sediment-laden flows is presented. The method has been developed to allow photometry and visually intrusive, conventional flow measurement instruments to be used simultaneously. Sediment-laden gravity currents of varying densities were released in a lock-exchange flume containing intrusive ultrasonic Doppler velocity profiling (UVP) probes, siphon tubes and a basal obstacle. A new approach to flume illumination and development of a binary noise-reducing algorithm suited to turbidity currents are presented. Additionally, a standard deviation filtering procedure is introduced. The combined process improves the visibility of opaque currents and optimizes current front recognition around visual obstructions. This offers a key advancement to previous photometric techniques and provides a practical way forward for laboratory experiments on sediment-laden flows.

Keywords:

• Buoyancy
• obstacle
• sediment-laden flow
• turbidity
• visualization

Acknowledgements

The authors would like to thank the laboratory technicians Trevor Patrick, Geoff Kirby and Jim Luo for their help in constructing and installing required experimental components.

ORCID

Richard I. Wilson http://orcid.org/0000-0001-6613-3760

Craig Stevens http://orcid.org/0000-0002-4730-6985