Final answer:
Inviscid flow assumes no viscosity, but practical considerations of fluid dynamics near the surface of a rotating cylinder can lead to the generation of lift. D'Alembert's paradox highlights the discrepancies between theoretical and real-world observations. Viscous drag is a resistance force in fluids that depends on the flow regime and increases with speed.
Step-by-step explanation:
The concept described from J.D. Anderson's Aerodynamics book touches on both inviscid flow and the interaction of a fluid with a surface, specifically over a rotating cylinder. Inviscid flow by definition suggests an ideal fluid with no viscosity and thus no friction. However, in practical scenarios, even in the study of inviscid flow, we consider the effects of the boundary layer where the fluid interacts with the surface, despite the viscosity being negligible. This explains the generation of lift due to the fluid near the rotating cylinder surface being dragged along, creating a vortex and circulation around the cylinder.
The mention of D'Alembert's paradox refers to the theoretical result where an inviscid and incompressible flow around a cylinder predicts zero drag, which contradicts real-life observations. This paradox underscores the complexities and limitations of theoretical models, which omit factors such as viscosity and separation that are crucial for accurately predicting drag and lift in real fluids.
When it comes to viscous drag, as described in the information provided, this is a resistance force that increases with the object's speed when moving through a fluid. For laminar flow conditions, the drag force is directly proportional to velocity, whereas for turbulent conditions, it becomes proportional to the velocity squared. This understanding is critical for various applications, including bicycle racing and the study of terminal speeds in falling objects through fluids.