Low Reynolds Number Turbulent Flow in Large Aspect Ratio Rectangular Ducts

Abstract

Experiments are reported on fully developed turbulent flows at low Reynolds numbers in rectangular ducts of large aspect ratio. Six ducts, with aspect ratios between 15.5:1 and 35.0:1, were employed for the investigation, covering a Reynolds number range from 5,000 to 27,000. A friction factor, Reynolds number relation expressed as f = 0.507 R−0.30 was found to be an excellent representation of the experimental data when the equivalent diameter was used as the characteristic length dimension. The Blasius and Prandtl circular tube friction factor relations, generalized by use of the equivalent diameter, gave results within 5 percent or better of the aforementioned correlation over the Reynolds number range of this investigation.