Lec_2_Wk_2_Fluid_properties_Compatibility_Mode_

Lec_2_Wk_2_Fluid_pro - Do you still remember Fluid Mechanics Fluid dynamics Fluid statics Stress tensile compressive shear Shear force shear strain

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1 Do you still remember? • Fluid • Mechanics • Fluid dynamics • Fluid statics • Stress – tensile, compressive, shear • Shear force, shear strain • Newton’s law of viscosity [email protected] • Ability to resist deformation? If YES let’s move on………. Lecture 2 Week 1 Fluid Properties [email protected] Viscosity & kinematic viscosity Density, Specific volume, Specific weight, Specific gravity Surface tension, Pressure
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2 Viscosity Property that determines the amount of resistance to shear force. Due primarily to interaction between fluid molecules F y U V Fluid [email protected] Fluid is filled between plate To keep plate moving at constant velocity, U a constant force, F must be applied Viscosity [email protected] y AU F α dy dV A F α dy dV α τ
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3 Viscosity dy dV μ = τ Coefficient of viscosity [email protected] viscosity (dynamic viscosity) Viscosity d dV μ τ = Newton’s law of viscosity Shear stress is linearly proportional to the velocity gradient dy = [email protected] dy dV μ = f (types of fluid, time and T)
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4 Types of fluids Newtonian fluids Fluids that obey Newton’s law of viscosity Non-Newtonian fluids Fluids that do not obey Newton’s law of viscosity [email protected] Fluids that do not obey Newton s law of viscosity μ varies with types of fluid Newtonian fluids τ is proportional to dV/dy All gases All liquids having simple chemical formula – E.g: H 2 O, CH 3 OH, C 6 H 6 Most dilute solution of simple molecules in water or [email protected] simple molecules in water or organic solvents – Metal ion solution, sugar in water
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5 Newtonian fluids Straight line through origin [email protected] Non-Newtonian fluids μ varies with types of fluid • Shear stress is a function of the velocity gradient. (viscosity is not a constant) [email protected]
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6 Bingham fluids • Resist small shear stress. • Flow easily under larger μ varies with types of fluid shear stress (Force must be given in order to move the fluid) [email protected] • Pseudoplastic fluids • Shear thinning fluids μ varies with types of fluid viscosity decreases with increasing rate of shear stress μ o as dV/dy m [email protected] A shear thinning fluid decreases in viscosity with increasing shear rate
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7 Dilatant fluids • Shear thickening fluids μ varies with types of fluid μ m as dV/dy m • E.g. Starch suspension, printing ink [email protected] μ varies with time Viscosity is time independent All Newtonian fluids are time independent [email protected] Most of non-Newtonian fluids are time dependent
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