An Elementary Analysis for Predicting the Momentum- and Heat- Transfer Characteristics of a Hydraulically Rough Surface

A simple model is presented which approximates the turbulent shear flow over a well-defined rough surface as a series of attached and separated flow regions. An elementary analysis applied to the model provides values for the well-known momentum- and heat-transfer roughness functions R(h+) and g(h+, Pr), respectively. In order to use the calculation method the exact shape and distribution of the roughness elements are required together with a form drag coefficient and a characteristic separation length. These may be found in the literature for many roughness shapes of interest.