In low-speed external flow over a bluff object, vortices are shed from the object. The vortex shedding produced by a particular object is to be studied in a water tunnel at a LaTeX: \frac{1}{4}1 4 scale model (model 1/4 the size of the prototype). After a dimensional study, it is found that the Pi terms of this phenomenon are the Reynolds number and the Strouhal number: