Improved quantification of the drag reduction phenomenon through turbulence reduction parameters

In this article we compare the use of the usual drag and heat transfer redu ction parameters with that of turbulence reduction parameters. The latter q uantify the relative degree of turbulent effects reduction or 'laminarizati on' exhibited by the drag-reducing fluid, rather than the 'absolute' fricti on or heat transfer reductions as with the former. We show that the use of these turbulence reduction parameters is more appropriate in many cases. Fo r example, the turbulence reduction parameters are independent of the Reyno lds number over wide ranges of parameters in contrast to the classic parame ters. The turbulence reduction parameters also show clearly that the drag r eduction in curved pipes is, in fact, not dramatically lower than in straig ht 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 const ant ratio between heat and drag reductions over a wide range of Reynolds nu mbers. (C) 1999 Elsevier Science B.V. All rights reserved.