CE 2200 Chapter : Lect 15
Document Summary
Common dimensionless numbers (common (cid:16)groups: the primary dimensions of the dependent variables in a general flow are, total 10 variables, involving 3 basic dimensions. [l, m, t], resulted in 7 common (cid:16)groups (dimensionless numbers): (cid:1) 3 dependent (cid:8)groups (cid:1) 4 independent (cid:8)groups. The general functional form for all (cid:8)groups : all (cid:8)groups : Numbers ( (cid:16) groups: all dimensionless groups can be explained by the ratio of inertia (kinetic) to some force, reynolds number: re= lv/7 = inertial force/viscous force (also re=lv/ ). It is generally of importance in all types of fluid mechanics problems. (cid:2: froude number: = inertial force/gravitational (cid:3)(cid:4) (cid:1)(cid:1) force. It is important in flow with a free surface: mach number: ma=v/c = inertia force/compressibility force=flow speed/speed of sound. Numbers ( (cid:16) groups: weber number: = inertial force/surface (cid:5)(cid:6) = tension force. 2(cid:1)(cid:2) (cid:2) problems in which surface tension is important.
