Laboratory Verification of the Optical Turbulence Sensor (OTS): Particulate Volume Scattering Function and Turbulence Properties of the Flow
ROSENSTIEL SCHOOL OF MARINE AND ATMOSPHERIC SCIENCE MIAMI FL
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Our goal is an extensive tank validation of the Optical Turbulence Sensor OTS. This sensor uses a Hartman optical wavefront sensor to determine turbulence characteristics and to characterize the particulate field. The OTS has recently undergone successful field testing. The ocean trials indicate that the OTS surpasses in many ways current microstructure based instruments to quantify turbulence. Furthermore, it is able to measure particles. As is natural for a novel measurement, a number of questions have arisen with respect to both turbulence measurements and the particle characterization that we address in our effort. We have two-fold objectives Particle field characterization We plan to develop new methods to fully exploit the raw OTS images, including the projection flow velocity and the near-forward Volume Scattering Function VSF of particles that cross the light path. From the measured VSF Volume Scattering Function at small angles we can recover the particle size distribution from the field data for larger particles 100 microns. The simultaneous measurement of the particle size distribution and the flow velocity, using a single instrument, allows for unprecedented determination of particle volume transport on very small scales and turbulence particle interaction. Turbulence characterization In this part of the effort we plan to compare independent and highly accurate thermistor and Particle Imaging Velocimetry PIV measurements of the Turbulent Kinetic Energy dissipation rate and the temperature dissipation rate with concurrent OTS measurements of the same variables. The studies will be performed in well-controlled tank experiments in the lab. The comparisons will allow detailed characterization of the OTS, including its sensitivity and the applicability of the assumptions of isotropy and homogeneity used in the data processing.
- Physical and Dynamic Oceanography
- Test Facilities, Equipment and Methods
- Optical Detection and Detectors