Air Plane Aerodynamics example essay topic
The investigation of the flow behind on oscillating airfoil has shown that two waves of convected vortices can be distinguished: One wave convected at, roughly, the outside uniform velocity; and an inner wave in the core of the wake originating at the trailing edge which is convected at a much lower speed. At a certain distance behind the airfoil there is a partially destructive interference, which depends on the reduced frequency. For the flow above a circle-cylinder it is shown that giving small symmetric displacements from its equilibrium position to a vortex pair positioned near the circle-cylinder, periodic oscillations set in. Expressions for closed orbits and their periods are obtained.
For the large amplitude case the vortex trajectories are calculated numerically. For a circle-cylinder with strakes the vortex motions may be periodic, quasi-periodic or the vortices may be swept away, depending on the initial conditions. From the equations of motion of flexible slender bodies with constant cross sections immersed in a uniform axial flow, expressions have been derived for the divergence speed and for the flutter speed. The analytical results are compared with the classical waving flag solution and with results from wind-tunnel experiments.
The classical propeller theory of Theodor sen provides a rational estimate of the highest attainable efficiency. However, it yields a too high static pressure in the slipstream. A modification, incorporating rolling-up vortex sheets in the slipstream, proves to be a good remedy for this deficiency. The entire theory is affected by the modification, leading to simpler expressions for thrust, power and efficiency. The engine / propeller combination is balanced right on the aircraft, in a flight ready state. A small vibration sensor (accelerometer) is attached to the engine in a location where vibration due to mass imbalance is maximum.
A small tach pickup (photo-tach) is also mounted to the cowl or engine to produce a propeller tach signal. The engine is operated and the vibration and tach signals are processed by the electronic balancer. The balancer produces a vibration level (magnitude) which corresponds to the amount of mass imbalance which exists. The balancer also provides a "phase angle" which corresponds to the location of the mass imbalance on the propeller disk. The vibration level and phase angle are used to compute a balance solution (weight amount and location). The balance solution is added to the propeller and the measurement is repeated until the vibration level is found to be acceptable.
As an alternative to the theory of vortex sound the generation of sound has been formulated as a potential-flow problem, in which a convected wave equation is solved for the velocity potential. This formulation is applied to the sound generated by a dipole moving across the edge of a half-plane, which is generic for the problem of the sound generated by a turbulent eddy crossing the trailing edge of a wing. The elementary problem of the diffraction of a spherical sound pulse on a half plane can be solved by a method using Fourier transforms. The generalization of the 3 dimensional Lap lace solutions to a pulse solution of the wave equation is straightforward. The solution for the diffracted field inside the spindle front around the edge is analyzed. It is shown that in this region the 3 dimensional character of the solution attains 2 dimensional similarities.
The proper modeling of separation from smooth surfaces is of great value for the prediction of the aerodynamic characteristics of configurations utilizing vortex lift. Tangential separation is studied by implementing appropriate boundary conditions in a numerical code based on the finite-volume discretization of the Euler equations. The numerical results are compared with results from non-linear conical flow theory. Recently a model for tangential separation based on conical stagnation point solutions has been proposed and will be validated. A numerical simulation tool has been developed to investigate high-temperature effects in high-enthalpy flows. A quasi 1 D Nozzle simulation with finite-rate chemistry and ionization has been developed.
(ENO-van Leer's schemes). The extension regarding two-dimensional flows is implemented and is in the process of validation. (L. Wal pot) In conclusion aerodynamics is a very interesting subject. Aerodynamics has to deal with lots of thing like cars, aircrafts, spacecrafts and lots of other things. "Aerodynamics" spacecraft aerodynamics "Aerodynamics" Research Topics" aerodynamics: research. "Low Speed Aerodynamics" Aerodynamics: research "Air and the Importance of Basic Aerodynamics" Air Plane Aerodynamics "THEORY: Propeller and Rotor Balancing" propeller theory.