کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
670698 | 1459036 | 2014 | 14 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Cessation of viscoplastic Poiseuille flow with wall slip
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
جریان سیال و فرایندهای انتقال
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چکیده انگلیسی
We solve numerically the cessation of axisymmetric Poiseuille flow of a Herschel-Bulkley fluid under the assumption that slip occurs along the wall. The Papanastasiou regularization of the constitutive equation is employed. As for the slip equation, a power-law expression is used to relate the wall shear stress to the slip velocity, assuming that slip occurs only above a critical wall shear stress, known as the slip yield stress. It is shown that, when the latter is zero, the fluid slips at all times, the velocity becomes and remains uniform before complete cessation, and the stopping time is finite only when the slip exponent s < 1. In the case of Navier slip (s = 1), the stopping time is infinite for any non-zero Bingham number and the volumetric flow rate decays exponentially. When s > 1, the decay is much slower. Analytical expressions of the decay of the flat velocity for any value of s and of the stopping time for s < 1 are also derived. Using a discontinuous slip equation with slip yield stress poses numerical difficulties even in one dimensional time-dependent flows, since the transition times from slip to no-slip and vice versa are not known a priori. This difficulty is overcome by regularizing the slip equation. The numerical results showed that when the slip yield stress is non-zero, slip ceases at a finite critical time, the velocity becomes flat only in complete cessation, and the stopping times are finite, in agreement with theoretical estimates.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Non-Newtonian Fluid Mechanics - Volume 203, January 2014, Pages 24-37
Journal: Journal of Non-Newtonian Fluid Mechanics - Volume 203, January 2014, Pages 24-37
نویسندگان
Yiolanda Damianou, Maria Philippou, George Kaoullas, Georgios C. Georgiou,