Question

Reynolds Number.Typical values of the Reynolds number for various animalsmoving through air or water are listed below. For which cases is inertia of the fluid important? For which cases do viscous effects dominate? For which cases would the flow be laminar; turbulent? Explain.

Animal Speed Re
(a) large whale 10m/s 300,000,000
(b) tlying duck 20m/s 300,000
(c) large dragonfly 7m/s 30,000
(d) invertebrate larva 1mm/s 0.3
(e) bacterium 0.01mm/s 0.00003

Answer 1

i) Cases with Important Inertia

Large whale ( a ) , Flying duck ( b ) , Large dragonfly ( c )

ii) Cases where viscous effects dominate

Invertebrate larva ( d ) , bacterium ( e )

iii) Cases where flow is Laminar ( cases where Re is < 2,100 )

Invertebrate larva ( d ), bacterium ( e )

iv) Cases where flow is turbulent ( case Re is > 2,100 )

Large whale (a) , Flying duck (b), Large dragonfly ( c ),

Step-by-step explanation:

Reynolds number is the the ratio of Initial forces to viscous forces, hence cases with Large Reynolds number ( > 2100 ) have their inertial forces greater than viscous forces, therefore we can say the Inertia is more important , while cases with smaller Reynolds number ( < 2100 ) have the viscous forces greater than the inertial forces therefore in such case the viscous effect is more important

i) Cases with Important Inertia

Large whale ( a ) , Flying duck ( b ) , Large dragonfly ( c )

ii) Cases where viscous effects dominate

Invertebrate larva ( d ) , bacterium ( e )

iii) Cases where flow is Laminar ( cases where Re is < 2,100 )

Invertebrate larva ( d ), bacterium ( e )

iv) Cases where flow is turbulent ( case Re is > 2,100 )

Large whale (a) , Flying duck (b), Large dragonfly ( c ),