a property of fluid ability of a fluid to flow freely relates applied stress to

A property of fluid ability of a fluid to flow freely

This preview shows page 50 - 56 out of 229 pages.

a property of fluid : ability of a fluid to flow freely, relates applied stress to the resulting strain rate U h y x no-slip condition ( ) y u y U h = linear profile ( ) yx yx f τ = general relations will be considered later! For simple fluids such as water, oil, or gases relationship is linear Or Newtonian 2 yx yx U du h dy τ µ µ µ = = ∈ = μ: (coef. of) viscosity [N s /m 2 = Pa.s] , μ= μ(T,p) different for liquids & gases ( ) yx yx f τ = is not linear, the fluid is non-newtonian
Image of page 50
time rate of deformation, Є inviscid flow (ideal fluid) du/dy 0 τ shear stress ideal bingham plastic Pseudoplastic – shear thinning μ as τ↑ Polimer solutions , toothpaste dilatant – shear tickening, suspensions, starch, sand Newtonian , μ=constant yield stress Rigid body 2 n yx yx K τ Power-law approx. n=1 Newtonian K=μ n<1 pseudoplastic n>1 dilatant (kaboran) K, n : material parameters Power-Law: 0 1 T n n T yx yx yx ke τ = (rheological models of blood)
Image of page 51