The Aerodynamics - Assignment Example

Question 3 At high angles of attack when applying slender delta wings, the vortex breakdown is asymmetric. Leading-edge asymmetric vortices are not generated at symmetric flow conditions on a sharp-edged delta wing. Rounded leading edges with thick delta wings have apex geometry that resembles fore body, which is slender and is normally subjected to vortex asymmetry at ∅=β=0. For an 800 delta wing, there is a progression downstream of vortex lift off from the apex and a roll damping that occurs when the angle of attack is greater than 200. Oscillations results depicts that if the attack angle is large enough the wing oscillates until a critical angle is exceeded beyond,which the lee-side wing will experience vortex lift off caused by asymmetric flow conditions (Lewis, pp.145-213). Large undamping causes a rapid build-up of wing-rock amplitude until a damping action is caused by the vortex breakdown on the windward wing, which lowers the net damping until it reaches zeroIt limits the cycle oscillations observed and predicted by lattice vortex methods. Bearing friction is overcome without the undamping generated from vortex lift off due to the increased wing area that increases the vortex-induced rolling moment. Predictions of unsteady induced drag are important in flexible aircraft dynamics and flapping applications in which the aerodynamics forces plays a crucial role. The suction force due to the leading edge balances the steady case components of pressure force in a free-stream direction. Moreover, within an unsteady case thrust or drag might develop depending on the details provided in the case. Vortex-lattice method requires inclusion of singularities and resolves the average aerodynamic surface for the unsteady force component given in Bernoullis equation Question 4 The VLM attempts to predict the behavior of various components of the plane to the data obtained in a wind tunnel. This method produces data that is in agreement with the data for the neutral point location, lift and moment curve slopes at Mach 0.2. When studying the effects of canard using VLM it when the canard is above the wing then the neutral point is independent of the canard height. Moreover, when the canard is below the wing then neutral point varies with the canard height. The effects of the number of panels range from 120 to 240 panels and ought to be provided in order to obtain converged results.VLM has the best results when many span-wise stations are employed in conjunction with a relatively low number of chord-wise panels. The use of VLM in geometric models with wing-body stipulates that specify the platform of the configuration as a flat lifting surfaces that are constituted of straight-line segments (Lewis, pp.145-213). Question 5 Slender sharp-edge wings are nonlinear due to their aerodynamic characteristics. Vortex breakdown alters the surface pressure field and reduces the lift curve slope at it approaches the wing. As it approaches the apex of the wing then, the maximum lift coefficient is reached. The wing stall occurs when the leeward flow separates the wing completely. Vortex-lattice method has tried to explain these phenomena, but there are other theories that try to explain it, but none is widely accepted. Most of the vortex breakdown comes from tests and experiments that are conducted in isolated vortex developed inside tubes. At an angle of attack for slender wings, only bubble and spiral types of breakdown are determined which only represents a fraction of the continuum of breakdowns. Pressure distribution on a slender wing surface at an angle of attack is not properly defined. In other incidences, evidence of secondary suction peaks is identified in the vortex flows. When a breakdown appears the suction peak but, on the other hand, the vortex will act over a wider region. Pressure gradient that acts on the vortex axis is essential for delaying the vortex breakdown. Over the top of a delta wing, the pressure rise occurs developed by obstacles that are downstream but closer to vortex wake (Lewis, pp.145-213). The theories developed do not sufficiently address pressure gradient. Moreover, vortex-lattice method also does not explain the theory clearly. There are several theories that explain in details the occurrence of pressure gradients.Variables are an inclusive of external factors like angle of attack or sweep angle along the field of flow in order to establish what interactions occur near the vortex breakdown if any. Question 6 Vortex separated flows lead to a couple of scenarios that might lead to spins or stalls on the aircraft. It is utilized within in aircraft design and provides insights into interactions between lifting surfaces. Moreover, it offers the knowledge for configuration of the neutral point during the design stages and in learning the effects of wing placement and canard. Locating the induced drag developed from the span load with a combination of far field methods enables appropriate design of the vortex. Subsequence to the recognition of the stall, the pilot of the co-pilot ought to take control of the plane by making a series of actions. First, the angle of attack ought to be decreased in order to improve the airspeed and flow over the wings. The power is subsequently applied thereby minimizing the loss of altitude whilst instantly increasing the air speed. Coordinated flight is then maintained by adjusting the power to the required limits. Spins are also very common occurrence but in the recent years, anti-spin technologies are applicable on the aircrafts (Lewis, pp.145-213). The recovery to a spin is undertaken manually through engagement of the throttle into idle mode and neutralizing ailerons at the same time. In this scenario, it is essential to determine the direction of spin or rotation this will help in applying full rudder in the counter direction. The elevator is applied to the neutral position thus reducing the rotation, which halt a neutralize rudder thus preventing the start of spinning of the aircraft in the opposite direction. Conclusion Slender wings normally have very low attached flow lift curve slopes and not consisting of additional vortex lift which are only analysed by Vortex-lattice method. The high angles of attack at which the maximum lift occurs with a very slight loss of maximum lift are also determined through the analysis developed in VLM. The wake positions and rollups that are determined as part of the process of analysing the vortex flows. This theory has enhanced the predictions that can be made on the leading edge suction on slender and delta wings. In the unsteady flow, extension for the cases of assumed flat wakes the extension to harmonically oscillating surfaces is studied. The doublet-lattice method is employed for subsonic flutter calculations. Work cited Lewis, R I. Vortex Element Methods for Fluid Dynamic Analysis of Engineering Systems. Cambridge: Cambridge University Press, 2005. Print. Read More