Model making clipart

Similitude is the theory and art of predicting prototype (original object) performance from scale model observations. The main requirement of similitude is all dimensionless quantities must be equal for both the scaled model and the prototype under the conditions the modeler desires to make observations. Dimensionless quantities are generally referred to as Pi terms, or π terms. In many fields the π terms are well established. For example, in fluid dynamics, a well known dimensionless number called the Reynolds number comes up frequently in scale model tests with fluid in motion relative to a stationary surface. Thus, for a scale model test to be reliable, the Reynolds number, as well as all other important dimensionless quantities, must be equal for both scale model and prototype under the conditions that the modeler wants to observe.