流体力学名词解释 完整版完整版724532736.pdfVIP

CBE6333,R.Levicky1

ReviewofFluidMechanicsTerminology

TheContinuumHypothesis:

continuumapproximationwillbeappropriate.However,therearesituationswhen

apply.

Fluid

howsmallthestressmaybe.

ShearStress

2στ

Shearstressunits:Force/Area,ex.N/m.Usualsymbols:,(i≠j).

ijij

Example1:shearstressbetweenablockandasurface:

flowingliquid.Thetoplayermovesrelativetothebottomonebyavelocity∆V,and

Notethattheshearstressactsparalleltothesurfaceonwhichitisexerted.

CBE6333,R.Levicky2

NormalStress:

Pressureisanormalstress.

2στ

Normalstressunits:Force/Area,ex.N/m.Usualsymbols:,.

iiii

Pressure:

quantitythatisnot

specificdirection.

2

Pressureunits:Force/Area,ex.N/m.Usualsymbol:p.

ShearStrainRate(VelocityGradient):Imaginethatwehaveavelocityv(y)asshown

x

below.Thentheshearstrainrateisgivenby

movingplate

V

y

v(y)

xx

dv

stationaryplatex

ShearStrainRate=

dy

Shearstrainrateunits:1/Time,ex.1/s.

Usualsymbolsforvelocityx-component:v,u;y-component:v,v;z-compon