Thomas Szirtes Thomas Szirtes and Associates Inc. Toronto, Ont.,
Canada  Equations and graphs are the building blocks of most
product design. Engineers who work with them need to know the
relationship between a dependent variable and often several
independent variables. Graphs are a helpful way to convey these
relationships, especially when dealing with just two or three
variables. But as the number of variables increases, plotting
the function becomes more and more tedious. Getting useful
information from the plots is no easy matter either. Try
plugging six values into each variable of a five-variable
function and you’ll end up with 216 curves on 36 separate
charts. Dimensionless variables can reduce these figures
drastically.  A dimensionless variable (DV) is a unitless value
produced by (maybe repeatedly) multiplying and dividing
combinations of physical variables, parameters, and constants.
In design engineering, dimensionless variables are useful for
graphing multivariable relations, performing dimension