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Mechanical Properties Of Fluids

Question
CBSEENPH11020015

(a) What is the largest average velocity of blood flow in an artery of radius 2 × 10–3 m if the flow must remain laminar? (b) What is the corresponding flow rate? (Take viscosity of blood to be 2.084 × 10–3 Pa s).

Solution
Given,
Radius of the artery, r = 2 × 10–3 
Diameter of the artery, d = 2 × 2 × 10–3 m = 4 × 10– 3 
Viscosity of blood, η = 2.084 X 10-3 Pa s 
Density of blood, ρ = 1.06 × 103 kg/m

Reynolds’ number for laminar flow, NR = 2000
Average space velocity space of space blood space is space given space by space the space relation comma space

straight v subscript avg space equals space fraction numerator straight N subscript straight R straight eta over denominator ρd end fraction

space space space space space space space equals space fraction numerator 2000 space cross times space 2.084 space cross times space 10 to the power of negative 3 end exponent over denominator left parenthesis 1.06 space cross times space 10 to the power of 3 space end exponent cross times space 4 space cross times space 10 to the power of negative 3 end exponent right parenthesis end fraction
space
space space space space space space space equals space 0.983 space straight m divided by straight s
b) Flow rate is given by the relation, 

straight R space equals space πr squared straight v subscript avg

space space space equals space 3.14 space cross times space left parenthesis 2 space cross times space 10 to the power of negative 3 end exponent right parenthesis squared space cross times space 0.983

space space space equals space 1.235 space cross times space 10 to the power of negative 5 end exponent space straight m cubed straight s to the power of negative 1 end exponent space comma space is space the space corresponding
space rate space of space flow.