basic equation that must be remembered

Question 1

Re ( raynor’s number )

Answer 1

U(velocity) D(gap)/V(kinetic viscosity)

Question 2

kinetic viscositymomentum difufusivity

Answer 2

v=miu/rou ( cm^2/s) or stokes

Question 3

viscosity

Answer 3

miu: (poise: g/cm.s) 1Pa.s=10 poise

Question 4

what is incompressibility

Answer 4

delta.u =0 ( u is the volume flux the mass continuity equation simplied to volume continuity equation since incompressibility )

Question 5

Ns equation

Answer 5

rou( eu/et+u.(delta u) )=-delta P + miu(delta^2 u)+ rou(g)

Question 6

what is the continuity equation?

Answer 6

e rou/et+ delta. (rou u)=0 in any steady state process, the rate at which mass enters a system is equal to the rate at which mass leaves the system

Question 7

when does the fluid compressible ?

Answer 7

when mach number ( V/Vsound) is large

Question 8

Preserve dynamic similarity

Answer 8

Re1=Re2 Fr1=Fr2

Question 9

what is Fr ?

Answer 9

Froude number U^2( velocity square)/[L( width of the tank) g ]