Development of measurement techniques for studying propeller erosion damage in severe wake fields

Preliminary propeller erosion tests have been conducted at the Naval Surface Warfare Center Carderock Division 24 inch variable pressure water tunnel (VPWT), shown in Figure 1, to establish testing procedures for evaluating various coatings to minimize cavitation erosion damage to marine propellers. A severe wake field was produced using a two dimensional, thick foil ahead of a downstream driven propeller model. This approach was derived from similar tests conducted by Miller [11]. Conventional cavitation viewing was performed with cameras viewing through the tunnel side window. Images were acquired using high speed (up to 6000 fps) and high resolution (2K x 2K) cameras. In addition, a waterproof camera was mounted inside the foil looking directly downstream at the suction face of the blade. Two propellers were tested, a 16 inch (0.406 m) diameter propeller 5388 and a 12 inch (0.305 m) diameter propeller 4119 [8]. The foil wake field was measured with LDV surveys. Accelerometers were mounted in the water tunnel test section to measure acoustic emissions of cavitation activity. Cavitation erosion was observed at the tip of the 16 inch diameter propeller due to excessive tip vortex, and complicated vortex collapse. Moderate erosion was also observed at the inner radii, where leading edge sheet cavitation collapsed. Scanning techniques for quantifying propeller erosion damage were evaluated. These studies will transition to the 36-inch VPWT where a number of geosym propellers of different materials and coating will be assessed in a similar wake field.http://deepblue.lib.umich.edu/bitstream/2027.42/84210/1/CAV2009-final156.pd

Autonomous Microbial Sampler (AMS), a device for the uncontaminated collection of multiple microbial samples from submarine hydrothermal vents and other aquatic environments

Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 53 (2006): 894-916, doi:10.1016/j.dsr.2006.01.009.An Autonomous Microbial Sampler (AMS) is described that will obtain uncontaminated and exogenous DNA-free microbial samples from most marine, fresh water and hydrothermal ecosystems. Sampling with the AMS may be conducted using manned submersibles, Remotely Operated Vehicles (ROVs), Autonomous Underwater Vehicles (AUVs), or when tethered to a hydrowire during hydrocast operations on research vessels. The modular device consists of a titanium nozzle for sampling in potentially hot environments (>350°C) and fluid-handling components for the collection of six independent filtered or unfiltered samples. An onboard microcomputer permits sampling to be controlled by the investigator, by external devices (e.g., AUV computer), or by internal programming. Temperature, volume pumped and other parameters are recorded during sampling. Complete protection of samples from microbial contamination was observed in tests simulating deployment of the AMS in coastal seawater, where the sampling nozzle was exposed to seawater containing 1x106 cells ml-1 of a red pigmented tracer organism, Serratia marinorubra. Field testing of the AMS at a hydrothermal vent field was successfully undertaken in 2000. Results of DNA destruction studies have revealed that exposure of samples of the Eukaryote Euglena and the bacterium S. marinorubra to 0.5 N sulfuric acid at 23°C for 1 hour was sufficient to remove Polymerase Chain Reaction (PCR) amplifiable DNA. Studies assessing the suitability of hydrogen peroxide as a sterilizing and DNA-destroying agent showed that 20 or 30% hydrogen peroxide sterilized samples of Serratia in 1 hr and destroyed the DNA of Serratia, in 3 hrs, but not 1 or 2 hrs. DNA AWAY™ killed Serratia and destroyed the DNA of both Serratia and the vent microbe (GB-D) of the genus Pyrococcus in 1 hour.This work was supported by a DOC/NOAA Small Business Innovative Research Award, Contract No. 50-DKNA-9-90116 awarded to McLane Research Laboratories, Inc. and (via subcontract) to the Woods Hole Oceanographic Institution. Some of the microbial testing work was also supported by the National Science Foundation, Grant No. IBN-0131557 and the Woods Hole Oceanographic Inst. Deep Ocean Exploration Institute Grant No. 25051131