3.8.1Sudden enlargement
When the cross-section of a pipe enlarges gradually, the streamlines follow
closely the contours of the duct and virtually no extra frictional losses are
incurred. On the other hand, whenever the change is sudden, additional losses
arise due to the eddies formed as the fluid enters the enlarged cross-section.
The resulting head loss for laminar flow can be evaluated by applying the
mechanical energy balance in conjunction with the integral momentum
balance. Consider the flow configuration shown in Figure 3.23 in which the
section ‘2’ is located immediately after the end of the smaller pipe. By suitable
choice of plane ‘1’, the frictional pressure loss may be assumed to be negligible
between planes ‘1’ and ‘2’ and hence p1 p2; the latter acts over the whole
cross-section (R2
2). Also, immediately following the expansion at section ‘2’,
the streamlines will be nearly parallel to the axis and the velocity profile at
section ‘2’ will be similar to the fully developed profile at section ‘1’. If section
‘3’ is sufficiently far down-stream, the velocity profile again be fully
established. On applying the integral momentum balance over the control
:volume as shown in Figure 3.23
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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