The effect of molecular weight distribution of polyacrylamide (PAAm) on drag reduction was studied in two flow geometries. Commercial PAAm with different weight averaged molecular weights (M_w = 5 × 10⁵ to 1.8 × 10⁷ g/mol) were investigated in turbulent pipe and rotational flows. Comparison of PAAm with different molecular weight distributions showed that drag reduction is not only a function of the averaged molecular weight. Broader polymer molecular weight distributions provided increased drag reduction over polymers of same average molecular weight but with a more narrow distribution. The role of distribution widths is of significance as polymer degradation in turbulent flows causes narrowing of the molecular weight distributions. Multiple linear regression was employed to connect weight fractions of polyacrylamide with drag reduction. Multiple linear regression was successfully applied to describe drag reduction in turbulent pipe and rotational flows indicating that drag reduction can be quantitatively derived from the molecular weight distribution of PAAm.

在两种流动几何形状中研究了聚丙烯酰胺 (PAAm) 的分子量分布对减阻的影响。 在湍流管和旋转流中研究了具有不同重均分子量（M _w  = 5 × 10 ⁵至 1.8 × 10 ^{7 g/mol）的商业 PAAm。}不同分子量分布的 PAAm 的比较表明，减阻不仅是平均分子量的函数。与平均分子量相同但分布更窄的聚合物相比，更宽的聚合物分子量分布提供了更高的减阻效果。分布宽度的作用非常重要，因为湍流中的聚合物降解会导致分子量分布变窄。采用多元线性回归将聚丙烯酰胺的重量分数与减阻联系起来。多元线性回归成功地应用于描述湍流管道和旋转流中的减阻，表明减阻可以从 PAAm 的分子量分布中定量得出。