Evaluation of Flush Mounted Hot-Film Sensors for Skin Friction ReductionMeasurements in Viscoelastic Polymer Solutions

摘要

The performance of flush mounted hot-film sensors for mean wall shear stressmeasurement in turbulent flows of dilute drag reducing polymer solution is evaluated. A series of pipe flow experiments were conducted to compare the level of skin friction reduction measured by hot-film sensors with values determined from the pipe pressure drop. Water calibrated hot-film sensors consistently underestimate the wall shear stress in the dilute polymer flows. For the range of flows tested, hot-film determined percent drag reductions are low but generally within 15 percent of the correct value. Like drag reduction, heat transfer reduction results from the elastic properties of polymer solutions. These two phenomena are distinct and their differences suggest that Reynolds' analogy is not valid in the dilute polymer flows.