The above theory in a way is correct, but it does not explain correctly how airflow over the wing produces lift. ( NOTE: Circles = time intervals of airflow over the airfoil. Thus, airflow on the lower surface has a higher pressure, and slower velocity.īecause airflow over the top surface is faster, it produces greater force than the bottom, thus creating our " Lift " force perpendicular to the airflow. As air flows over the top surface of the airfoil, which has a longer distance than the lower surface, it has a lower pressure, thus a faster velocity or speed. In this diagram, "streamline" is the air which goes over the wing (aka airfoil from a side-view). This theory ignores friction over surfaces, which is easier to understand, but is not completely accurate. Lift is generated in accordance with the fundamental principles of physics, such as: Newton's Laws of Motion, Bernoulli's Principle, Conservation of Mass, and Balance of Momentum (similar to Newton's 2nd law). It is opposite of the drag force (explained later), which is parallel to the flow field. Lift is a force, which is perpendicular to the flow field direction. By defining a control volute around the flow field, equations for the conservation of mass, momentum, and energy can be defined and used to solve for the properties. Typical properties calculated for a flow field include: velocity, pressure, density, and temperature. Understanding the motion of air (aka " flow field ") around an object enables the calculation of forces and moments acting on the object. Aerodynamics is often used synonymously with fluid and gas dynamics, with the difference being fluid dynamics is applied to liquids, and gas dynamics to gases. (Discuss the basics of aerodynamics, and what makes an airplane fly)Ģ.1) Bernoulli's Theory of Lift (incorrect theory)Ģ.2) Real Theories on Lift (correct theory)Īerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object.
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