9360095 Keefe Drag due to turbulent skin friction substantially penalizes the performance and economics of oil and gas pipelines. Using two new control ideas originating from research in nonlinear dynamical systems, Nielsen Engineering and Research (NEAR) has recently used numerical simulations to demonstrate the possibility of 50-60% drag reductions at constant massflux in rectangular channel flow, and proposes to apply these same ideas to drag reduction in circular pipes. In rectangular channel flow a key ingredient for the successful application of these controls has been the use of low-drag, nonlinear flow states as goal dynamics. While these finite amplitude states in channels and boundary layers have been know for a number of years, their existence in pipe flow has not yet been demonstrated. In the proposed research Nielsen Engineering intends to demonstrate the existence of nonlinear neutral states in pipe flow, and calculate their form. One part of the research will make use of intriguing new theoretical results that suggest some of these finite amplitude states may not be spatially periodic. The other will use established linear and nonlinear stability techniques on the related problem of elliptical pipe flow, with the intent of demonstrating a connection between the nonlinear states of this flow and pipe flow as ellipticity decreases.
