Which assumption in simple fluid dynamics refers to the lack of internal friction between fluid layers?

The assumption of zero viscosity in fluid dynamics indicates that there is no internal friction between fluid layers. This means that the fluid flows without any resistance caused by the interaction of its molecules, allowing it to move in an ideal manner. In real-world fluids, viscosity represents the internal friction that affects how layers of fluid interact with one another as they move. By assuming zero viscosity, the analysis simplifies the equations of motion for fluids, making it easier to study their behavior under ideal conditions.

The concept of zero viscosity is crucial in developing fundamental fluid dynamics models, such as the inviscid flow assumption used in Bernoulli's principle. This approximation allows for the analysis of flow patterns and simplifies the study of fluid motion without considering the complexities introduced by viscous forces. This assumption facilitates the exploration of phenomena such as potential flow, where fluid has no viscosity and moves in a more predictable manner, contributing to a clearer understanding of fluid behavior under specific conditions.