Microbubble Drag Reduction Demonstration

"Specifically, we plan to use designs and hardware we have already developed for polymer ejectors to conduct a series of detailed experiments. From the perspective of prudence, we plan to reduce the risk and uncertainty in interpreting at-sea tests by firstconducting a set of experiments in the 12-inch ARL/PSU water tunnel. We plan a set of detailed measurements that will allow discrimination between effects that are not discernable in the ocean environment. The experiments entail making precise measurementin the near-wall region, which is not possible at sea, but for which we are well equipped in the water tunnel. The results from these experiments will enhance the probability of success during the at-sea test and provide insight to evaluate the datacollected at sea.We plan to use the fully funded HYSWAC lifting body to accomplish at-sea objectives. The vehicle is already designed with an interchangeable leading edge, so we can construct and install the ejector section at any time during the program. We have alsorequested that the body be equipped with removable panels on both top and bottom, so we can instrument replacement panels with microbalances and B.L. taps to measure local drag and gas concentration.BENEFITS: The implementation of MBDR will have the same benefits as polymer drag reduction without the cost associated with the expenditure of polymer. Specifically, these are the reduction of fuel costs, an increase in endurance or range, and thereduction in wake-related signatures. An alternative to reducing fuel costs is to increase speed for the same installed power.An analysis of the reduction in powering requirements for expected DD-X designs ranged from 30 to 35 percent, and for high-speed littoral craft, up to 50 percent. For warships, this equated to about a 30-percent reduction in fuel costs and nearly a50-percent increase in range for the same fuel load. For a high-speed transoceanic transport, operating at nearly 40 knots, the fuel costs would be reduced by over $3,000 per hour. If increased speed is the objective f