Improved quantification of the drag reduction phenomenon through turbulence reduction parameters

Abstract

In this article we compare the use of the usual drag and heat transfer reduction parameters with that of turbulence reduction parameters. The latter quantify the relative degree of turbulent effects reduction or `laminarization' exhibited by the drag-reducing fluid, rather than the `absolute' friction or heat transfer reductions as with the former. We show that the use of these turbulence reduction parameters is more appropriate in many cases. For example, the turbulence reduction parameters are independent of the Reynolds number over wide ranges of parameters in contrast to the classic parameters. The turbulence reduction parameters also show clearly that the drag reduction in curved pipes is, in fact, not dramatically lower than in straight ones as was previously believed to be the case. Finally the use of these parameters is also advantageous in that it leads to an approximately constant ratio between heat and drag reductions over a wide range of Reynolds numbers.