Flow separation occurs when a fluid, such as air or water, detaches from the surface of an object, like an airplane wing or a car body. This phenomenon typically happens when the fluid encounters an adverse pressure gradient, causing it to lose its smooth, attached flow. As a result, the fluid creates a turbulent wake behind the object, which can lead to increased drag and reduced lift. In engineering and aerodynamics, understanding flow separation is crucial for optimizing designs. For instance, aerodynamicists study flow separation to improve the performance of aircraft and automobiles, ensuring they are more efficient and stable during operation.