|
Shear rate is the rate at which a progressive shearing deformation is applied to some material. ==Simple Shear== The shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other one stationary (Couette flow), is defined by : where: * is the shear rate, measured in reciprocal seconds; * is the velocity of the moving plate, measured in meters per second; * is the distance between the two parallel plates, measured in meters. Or: : For the simple shear case, it is just a gradient of velocity in a flowing material. The SI unit of measurement for shear rate is s−1, expressed as "reciprocal seconds" or "inverse seconds". The shear rate at the inner wall of a Newtonian fluid flowing within a pipe〔Ron Darby, ''Chemical engineering fluid mechanics'', 2nd ed. CRC Press, 2001, (p. 64 )〕 is : where: * is the shear rate, measured in reciprocal seconds; * is the linear fluid velocity; * is the inside diameter of the pipe. The linear fluid velocity ''v'' is related to the volumetric flow rate ''Q'' by : where ''A'' is the cross-sectional area of the pipe, which for an inside pipe radius of ''r'' is given by : thus producing : Substituting the above into the earlier equation for the shear rate of a Newtonian fluid flowing within a pipe, and noting (in the denominator) that ''d'' = 2''r'': : which simplifies to the following equivalent form for wall shear rate in terms of volumetric flow rate ''Q'' and inner pipe radius ''r'': : For a Newtonian fluid wall, shear stress () can be related to shear rate by , where is the dynamic viscosity of the fluid. For non-Newtonian fluids, there are different constitutive laws depending on the fluid, which relates the stress tensor to the shear rate tensor. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「shear rate」の詳細全文を読む スポンサード リンク
|