UM Rosenstiel School | NSF Experiments
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NSF Experiments

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During June, we used the ASIST tank to finish the instrument cross-calibration of turbulence measurement by studying the classic grid turbulence. This is the first step of the NSF sponsored project on temporal and spatial scaling of dissipation under non-breaking surface waves- a collaborative effort with Texas A&M, Corpus Christi’s (TAMUCC’s) Darek Bogucki.

The Vectrino, VMP and OTS ready to collect some data.

The Vectrino, VMP and OTS ready to collect some data.

A heater and downstream grid were introduced to generate temperature gradients and homogeneous turbulence in a steady mean water flow. We used an IFA 300 hot-film anemometer and VMP200 shear probe to measure the turbulence velocity at different distances from the grid, during these measurements the hot-film was sampled at 10KHz. Its mean velocity was calibrated using a Nortek Vectrino. Additionally, Darek’s Optical Turbulence Sensor (OTS) and a FLIR infrared camera were used to measure the surface and vertical temperature profile at one distance from the turbulence-generating grid.

Water surface temperature, as measured by the FLIR camera.

Water surface temperature, as measured by the FLIR camera.

When all these calibrations were done, we made use of a Dantec Dynamics particle image velocimeter to map the turbulence structure in front the OTS, which could help the evaluation of the eddies propagating through the OTS sample volume. From these measurements, we plan to cross-calibrate our instrumentation and estimate the in-water turbulent kinetic energy dissipation.

Overall, it was interesting and challenging to use such disparate and advanced instruments in the measurement of turbulence. It is our hope that this will help us to discover some of the more realistic details of the phenomenon.

The OTS positioned in its tank expansion chamber.

The OTS positioned in its tank expansion chamber.

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