Effects of Surface Roughness on Turbulent Pipe Flow

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ABSTRACTPROPOSAL NO.: CTS-0306691PRINCIPAL INVESTIGATORS: ALEXANDER J. SMITSINSTITUTION: PRINCETON UNIVERSITYTHE EFFECTS OF SURFACE ROUGHNESS ON TURBULENT PIPE FLOWThe purpose of the research program is to use the Princeton University Superpipe, a unique experimental facility capable of generating Reynolds numbers from 31,000 to 35 million, to study the effects of surface roughness on fully developed turbulent pipe flow and resolve questions about the validity of the law of the wall and the behavior of flows over rough surfaces. Given the capabilities of the Superpipe facility, it will be possible, to study the effects of roughness from the hydraulically smooth regime to the fully rough regime. Detailed mean and turbulence measurements will be taken. The intellectual merit of the proposed activity will lead to: (a) A clearer understanding of the law of the wall, which is of fundamental importance to the field of fluid mechanics; (b) an improved understanding of flows over surfaces with small relative roughness; (c) a possible similarity relationship between high Reynolds number turbulence and rough-wall turbulence; and (d) a better description of roughness that correlates the effects of roughness with characteristic features of the roughness itself (rather than, for example, using "equivalent sand-grain roughness "approaches). The broader impacts resulting from the proposed are as follows. There are two primary technological impacts. First, the re-evaluation of the Moody chart, a set of universally accepted engineering curves widely used in design of piping systems and calculation of pumping power requirements since 1944. This chart is the basis for many engineering design calculations. The research will result in a revised version of the Moody chart based on new data. The impact on the design of piping systems is expected to be important, and of lasting value. Secondly, improved turbulence models for fully rough flows, and for high Reynolds number flows. Furthermore the PI has demonstrated a commitment to educating members underrepresented groups and widely disseminating data via an extensive website.