Flow Description, Streamline, Pathline, Streakline and Timeline
Streamline, pathline, streakline and timeline form convenient tools to describe a flow and visualise it. They are defined below. Figure 3.5 : Streamlines Figure 3.6: Streamline definition A streamline is one that…
Definition of Streamlines
An important concept in the study of aerodynamics concerns the idea of streamlines. A streamline is a path traced out by a massless particle as it moves with the flow. It is…
Conservation of Energy
The conservation of energy is a fundamental concept of physics along with the conservation of mass and the conservation of momentum. Within some problem domain, the amount of energy remains constant and energy…
Excess Thrust
The propulsion system of an aircraft must perform two important roles: During cruise, the engine must provide enough thrust, to balance the aircraft drag while using as little fuel as possible.During takeoff and maneuvers, the engine must provide additional thrust…
What is Thrust?
Thrust is the force which moves an aircraft through the air. Thrust is used to overcome the drag of an airplane, and to overcome the weight of a rocket. Thrust is generated by the engines of the aircraft…
Aerodynamic Force and Moment
the quantities that characterize the effect of a gaseous medium on a body—such as an airplane—that is moving in it. The forces of pressure and friction acting on the surface of the body can be reduced to a resultant R of these forces, called the aerodynamic force, and a pair of forces having a moment M, which is called the aerodynamic moment. The aerodynamic force is resolved into components in a rectangular coordinate system (Figure 1) which is associated with either the vector Figure 1. Resolution of the aerodynamic force into components in the flow coordinate system X, Y, Z and in the correlated system T, N, Z; the Z axis is not shown since it is perpendicular to the plane of the drawing velocity v of the body (flow or velocity coordinate system) or with the body itself (correlated system). In the flow system the force directed along the axis of flow in a direction opposite to the direction of the body’s motion is called the aerodynamic drag X, the force perpendicular to it and lying in a vertical plane is called the lift Y, and the force perpendicular to both of these is called the side, or lateral, force Z. In the correlated coordinate system the first two forces are, by analogy, the tangential T and normal N forces. The aerodynamic moment plays an important part in the aerodynamic design of aircraft and in determining their stability and controllability, and it is usually given in the form of three components, which are the projections on the coordinate axes associated with the body (Figure 2): L (rolling moment), N (yawing moment), and M (pitching moment). The values are positive when they tend to turn the body from the y-axis to the z-axis, from the z-axis to the jt-axis, and from the x-axis to the y-axis. Figure 2. Projections of the aerodynamic moment on the coordinate axes: L is the rolling moment, N is the yawing moment, and M is the pitching moment The aerodynamic forces and moments depend on the shape and dimensions of a body, the speed of its translational motion, its orientation to the direction of the velocity, the properties and the state of the medium in which the motion takes place, and in some cases on the angular rotational velocities and the acceleration of the body’s motion. The determination of aerodynamic forces and moments for bodies of different shapes under all possible flight modes is one of the principal problems of aerodynamics and of aerodynamic experiments.
High-speed Flight
Compressibility High-speed flight is flight near, but below the speed of sound. Below high-speed—what is regarded as slow-speed flight—the movement of air around an aircraft during flight does not involve compression…
Dutch Roll
The term Dutch roll refers to a tendency for an aircraft to roll whenever there is yaw. Swept wing aircraft are particularly susceptible, and many are equipped with yaw damper, which…
Wing Design
Laminar and conventional airfoils Two types of airfoils commonly used are the laminar and conventional airfoils; as a rule, the laminar foil is faster, but the cost is more adverse stalling characteristics. …
Lift and Drag Concepts
Factors that affect lift and drag can be expressed in the following formulas: Lift = CL × ½ pV2 × S Drag = CD × ½ pV2 × S …
