Types of fluids:-
Newtonian
Non- newtonian
Newtonian fluids:- the fluids that follow the newtons criteria are called newtonian fluids. Shear force= Ux/y where Ux is velocity in x direction. And y is the distance from the layer of minimum velocity.
The variation in velocity is only for certain thinkness after which the velocity is constant ,It is called boundary layer thickness.
boundary layer exists for every fluid. the part of liquid where resistance to flow exists is called boundary layer.
Fluids do not sustain shear stress , they are deformed under the action of external force and eventually flows.
In general when we plot a hydraulic gradient to velocity graph for newtonian fluids we get 3 regions , first for laminar flow, then for transient flow and the last one for the turbulant flow.
The region of transient flow is never the same for every time the experiment is repeated.
Eddies current:- for laminar flow such internal currents are generated.
Non- newtonian fluids:- that dont follow the newtonian criteria
properties:- apparent velocity depends upon the rate of shear and the previous shear history.
properties of both liquid and solid.
elasticity
heat and mass transfer coefficient are considerably affected by the behavior of the fluid.
2 types of non-newtonian fluids :-shear dependent , time dependent
For some fluids
Shear increases –> μa decreses –>shear thinning
shear increases –> μa increses –> shear thickening
Bingham plastic:- these need a minimum stress level to flow till that is achieved they behave like solids after that they behave like liquids.
Ry= μ( dUx/dy)^1-n this is power model
n=0 newtonian
n>1 shear thickening
n<1 shear thinning
newtonian fluids
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