An autonomous Moored Reciprocating Vertical Profiler (MRVP) has been developed and tested for measuring ocean turbulence. The MRVP is designed to combine the advantages of long-term moored measurements at specified depths with those of short-term ship-supported continuous profiling performed at high vertical resolution. The profiler is programmed to repeat vertical motions autonomously along the mooring cable based on a buoyancy-driven mechanism. A sea trial has been conducted in the South China Sea to evaluate the performance of the profiler. The shear probe data are unreliable when the flow past sensors is not sufficiently greater than an estimate of turbulent velocity. For 65% of the dataset, turbulence measurements are of high quality and the magnitude of dissipation rates is up to O(10⁻¹⁰) W kg⁻¹. To minimize the contamination induced by instrument vibration and improve the estimation of turbulent kinetic energy terms, an advanced cross-spectrum algorithm is implemented to the measured shear data. The corrected spectra agreed well with the empirical Nasmyth spectrum, and dissipation rates had averagely decreased a factor of 2 and 8 times lower than the raw spectra. The autonomous MRVP is proven to be a stable platform, and the novel upward measurement provides a new perspective for measuring long-term time series of turbulence mixing.

Flow characteristics of falling film around a horizontal elliptical tube under column flow were numerically investigated with the volume of fluid method. The three-dimensional film thickness distributions for elliptical tubes with three ellipticities and two arrangements (the major axis oriented vertically and the major axis oriented horizontally) were captured. This investigation also considered the effects of spray Reynolds number and contact angle on film thickness distribution. A comparison between elliptical tube and circular tube was also performed under typical spray Reynolds number of 258 and tube spacing of 20 mm. The results show that the tube shape has a great influence on the film thickness and flow behaviors: The liquid film formed outside the elliptical tube with the major axis oriented vertically is thinner and more uniform than that of the circular tube. Conversely, the film on the elliptical tube with the major axis oriented horizontally is thicker and more non-uniform than that of the circular tube. The increasing of Reynolds number generally increases film thickness, particularly in the crest region. Under incompletely wetted condition, the increasing of ellipticity decreases the liquid film coverage rate around the tube. In addition, a correlation for predicting the film thickness around elliptical tubes was proposed.