Lecture 2 Flashcards
types of flow
steady vs unsteady
viscous vs inviscid
laminar vs turbulent
1d flow
velocity depends on one space parameter
2d flow
velocity changes across the cross section
real system
must have a no slip boundary condition at a solid wall
no relative velocity between the wall and the fluid
uniform flow
flow variable remains constant over specified cross section ie 1d flow
flow variable is combination of
temperature pressure and density
steady state flow
flow variable will be constant with time (is averaged over few seconds, will vary if chose two separate points)
incompressible fluids
change of density with respect to time is zero
how to tell if fluid is incompressable
will have mach number less than 0.3 where Ma = velocity of source relative to medium, intertial force (u) / compressibility force, speed of sound in medium (a)
flow exterior to a body maybe treated as
inviscid (external flows) viscous effects confined to a thin boundary layer
turbulent fluid
immediate mixing of neighbouring fluids (high velocity)
laminar flow
no significant mixing of neighbouring fluid particles (low velocity)
reynolds number
density * speed * diameter / dynamic viscosity
critical reynolds number
2000 (may have to go to lower velocity to return to laminar)
critical reynolds number changes based on
different geometries
open or closed flow
surface roughness
ideal flow assumptions
inviscid steady state 1D incompressible (isothermal flow DONT NEED TO STATE)
continuity equation
volume flow rate = C1A1 = C2A2
