Quarterly Performance/Technical Report of the National Marrow Donor Program

Abstract

Background: This effort accompanied the DARPA Friction Drag Reduction Program (ATOITTO) effort at the University of Michigan funded under contract HR-001 1-04-1-001 "High Reynolds Number Micro-bubble and Polymer Drag Reduction Experiments" for flows over smooth surfaces. The details of that effort can be found in the final technical report for that project. The purpose of the additional investigation was to examine the physics and engineering of friction drag reduction methods for turbulent boundary layers (TBL) found in hydrodynamic flows over rough surfaces. Two methods of friction drag reduction (FDR) were examined: & Polymer Drag Reduction-solutions containing extensible, long-chain molecules are injected into a TBL. The polymer molecules interact with the underlying turbulent flow and lead to a reduction of the correlated velocity fluctuations and, hence, a reduction of the turbulent transport of momentum across the TBL. This leads to local drag reduction of up to --70% for TBL flows over smooth surfaces compared to a flow without polymer injection. 0Air Layer Drag Reduction-air is injected into the TBL with the aim of creating a stable gas layer of very high void fraction (> 80% void fraction), separating the liquid flow from the solid surface. This results in friction drag reductions of over 80% compared to the friction drag without air layers.Reduction of drag on marine transportation systems can reduce fuel cost and increase ship performance, including maximum speed, range between refueling, and increased payload. Currently, reduction in fuel cost is the primary driving force behind dragreduction research efforts because the world's non-military fleet consumed nearly 280 million tons of fuel as of 2006 and, as of 2005, the U.S. military was the world's largest consumer of diesel fuel.