Aerodynamic Drag Force: Laminar Flow & Turbulent Flow

One of the most important aerodynamic effects on energy consumption required to keep a body moving through a fluid is the aerodynamic drag force. The drag must be overcome by the thrust of a propulsion mechanism, which in turn is consuming energy. Everything else being equal, the higher the drag, the more energy is consumed. Therefore, for energy efficiency, bodies moving through a fluid should be low drag bodies. To understand how to obtain low drag, we have to first understand the nature of drag, and what really causes it. (more…)

Aerodynamic Force Sources: Pressure & Shear Stress

The next time you hear an airplane flying overhead, look up, and pause for a moment. What you see is a machine that is heavier than air, but which is somehow being sustained in the air. This is due to the airflow over the airplane. This airflow exerts a lift force which counteracts the weight of the airplane and sustains it in the air—a good thing. The airflow also exerts a aerodynamic drag force on the airplane which retards its motion—a bad thing. The drag must be counteracted by the thrust of the engine in order to keep the airplane going. The production of thrust by the engine consumes energy. Hence, the energy efficiency of the airplane is intimately related to aerodynamic drag. This is just one of many examples where the disciplines of aerodynamics and energy interact. (more…)