A new concept we’re learning in Fluids is the deformation of fluid particles as they move along a streamline. As a refresher, a streamline is a path traced out by lines tangent to the particles velocity at any given time. Therefore, if the velocity is constant, we can say that the streamline also traces out the particles path.
The four types of changes can be divided into two categories: linear and angular.
The specific equations are pretty complicated to derive, so I won’t go into the details. But think about a fluid particle moving through a river – it’s easy to see how it’s shape wouldn’t remain constant.
But why learn this stuff? This subject leads into another important concept – measuring the the amount of fluid that passes through a certain area, AKA flux. This can be used to measure how much waste is being dumped into a river, etc.