Civil and Environmental Engineering 2224 Lecture Notes - Lecture 5: Fluid Mechanics, Dependent And Independent Variables, Junkers J 1
4 Dec 2018
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This allows us to organize physical variables into dimensionless pi groups. Work out how the force on the car varies based upon the other 4 independent variables/ The reduction factor, j, allows me to work out "if i have n variables to start out with, how many groups can i reduce that to?" The reduction factor helps us figure out how we go from n variables to groups. They don"t have to occur in all the same term. They don"t have to appear in all 5 parameters. They just have to be represented somewhere in the variables. I should be able to reduce those 5 variables down to 2 dimensionless pi groups. J = 2 if two of mass, length or time appears. Three parameters that we"re going to use in order. Start with the dependent variable, in this case fd. You typically pick a velocity, a length scale and a fluid property.
