3.4.4Effect of pipe roughness
Considerable confusion exists regarding the effect of the pipe wall rough-ness
on the value of friction factor in the turbulent flow region, though the effect is
qualitatively similar to that for Newtonian fluids [Slatter, 1997]. Thus,
Torrance [1963] and Szilas et al. [1981] have incorporated a small correction to
account for pipe roughness in their expressions for the turbulent flow of powerlaw
and Bingham plastic fluids; under fully turbulent conditions, it is assumed
that the value of the friction factor is determined only by pipe rough-ness and
rheological properties, and is independent of the Reynolds number. However,
in view of the fact that laminar sub-layers tend to be somewhat thicker for non-
Newtonian fluids than that for Newtonian liquids, the effect of pipe roughness
is likely to be smaller for time-independent fluids [Bowen, 1961; W´ojs, 1993].
Despite this, Govier and Aziz [1982] recommend the use of the same function
of relative roughness for time-independent fluids as for Newtonian systems. In
. any case, this will yield conservative estimates
3.4.5Velocity profiles in turbulent flow of power-law fluids
No exact mathematical analysis of turbulent flow has yet been developed for
power-law fluids, though a number of semi-theoretical modifications of the
expressions for the shear stress in Newtonian fluids at the walls of a pipe have
.been proposed
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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