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Various methods have been employed in the aeronautics field to evaluate aircrafts in the engineering capacity. Computational analysis and experimental testing are the two main techniques used for the aircraft engineering evaluation. The two methods are different in that the computation method is more machine and software oriented while the Experimental technique is more practical oriented with involvement of physical checkups and tests by flight check pilots and engineers. Each method has its own specific pros and cons as discussed here.

Potential flow method.

The computational methods incorporate various geometric and physical modeling fidelity. The main computational technique applied is the potential flow method. This method represents powerful and strong aerodynamic flow when they are applicable. Assumptions involved in reducing governing fluid equations to a potential flow are in viscid flow, imitational flow and incompressible flow. Time dependency in unstable potential flows is arrested by the time dependent vortex come into an awake mode and unstable Bernoulli equation which is used in pressure computation. Although there might be suspect factor in the applicability of these methods, they provide good approximation of the trends found Potential flow methods represent a Powerful approximation of aerodynamic flows when they are applicable.

The assumptions which are involved in reducing the governing fluid equations to a potential flow are (1) rotational flow, (2) in viscid flow, and (3) incompressible flow. The time dependence in unsteady potentialflows is captured by the time dependent vortex wake history and the unsteady Bernoulli equation which is used to compute the pressure. As such, steady potential flow methods are relatively easily extended to model unsteady flows by implementing approaches to handle time varying wakes. Potential flow modeling is routinely used in the aeronautical industry for approximating high Reynoldsnumber flows with limited viscous effects (thin boundary layers with little to no flow separation).

Since potential flow methods are typically much simpler to discredited and solve, they present an attractive alternative to high fidelity simulations. In our current research into efficient flapping flight, potential flow methods play an important role in design space exploration and preliminary evaluation of candidate flapping geometries. Although the applicability of these methods may be suspect in some cases, the methods can provide a good approximation of the trends encountered, and solutions often provide indications of possible failures in modeling assumptions.

Wake only method: Hall opt

The other computational method is the wake only method: Hall opt for predicting optimal wake vertical distribution in flapping flight provide powerful approximations of how flight forces are efficiently generated. In this method forces are efficiently generated whereby in this method a given periodic wake shape is represented using a vortex – lattice discretization and the unknown optimal vortices distribution is determined by minimizing in the flight power expression subject to the period – average flight force constraints.

To sum up the computation techniques working principles involving computational fluid dynamics tools for fluid flow analysis to enhance security and efficiency assurance of the aircraft being checked in the virtual environment where computerized aeronautic checkups are done.Assisatant professor Kryszt Fidkowski of the university of Michigan has been deeply involved in this field and has even worked on the research and employment of a triangular cut cell adaptive method to allow high – order discretizations of the compressible Navier Stroke equations.

Computation methods involve predicative possibilities in complex systems. The computer aided analysis are routinely used to stimulate and predict component and subsystem performances allowing for the dramatic reduction in the cost of hiring staff for the costly and time intensive physical real time testing. Computational analysis method above being cost effective and less involving and also have a high accuracy percentage and fewer flaws are likely to arise.

High Fidelity Methods

The methods described thus far are accurate for flows in which viscous effects and flow separation are minimal. Unfortunately flapping flight presents a design space in which separation can easily occur (due to the large relative motions which are possible). Although viscous corrections and predictions can be applied in potential flow, modeling viscous effects such as large regions of separation or regions of re-circulating flow, requires higher fidelity physics solvers based on the full Navier-Stokes equations. Several options exist for modeling the unsteady, morphing geometry Navier-Stokes equations. Of these methods, several approaches have found success in flapping foil and wing applications. The first approach is the family of immersed boundary methods and the second approach is the Arbitrary-Lagrangian-Eulerian (ALE) approaches. In the computational framework considered, a high order, discontinuous Galerkin ALE approach is being pursued.

Discontinuous Galerkin Arbitrary-Lagrangian-Eulerian (ALE) Navier-Stokes: 3DG Our high fidelity simulation tool is a high-order accurate solver based on the discontinuous Galerkin methodand the CDG scheme for viscous terms. It solves the Navier-Stokes equations efficiently for a wide range of Reynolds numbers and Mach numbers and it uses an ALE formulation based on mapping which achieves arbitrary high orders of accuracy in space and time the computational domain is discredited with unstructuredsimplex meshes which allows for complex geometries and local adaptation. The code has alsobeen integrated with structural models, for fully coupled fluid-structure interaction simulations.

Experimental testing techniques

When it comes to experimental testing techniques, this may involve real time vehicle practical testing or an alternative simulation (in flight or ground based) of the real task or a simulation of the task in it real nature.

One method is performance measurement; the method is also referred to as atmospheric model and true airspeed model and provides info about the environment of the flight. Since the standard atmospheric used is a referee model modification must be done to take into account conditions which are not standard during daytime.

The airspeed measurement is another method in which a pilot – static tube which takes into account the differences between state and total pressure. Depending on the airplanes, the airplanes, the airspeed reading from such measurement can be equivalent airspeed or calibrated airspeed. For airplanes with lower speed such as the piston engine type, the airspeed while in contrast, higher speed crafts such as then commercial jet transports, the airspeed readings have the calibrated airspeed format.

The third method is the takeoff and climb thrust model maximum thrust that on aircraft may use during takeoff and climb modes operations are defined as the maximum takeoff thrust (MTOT) and maximum climb thrust (MCLT) comparison of measured thrust data to the thrust values predicted at varying flight conditions confirming. The quadratic model provisions of a proper and appropriate fit within the considered flight envelop.

The fourth method is the DOC method which is widely used and endorsed by various organizations and bodies. The Method incorporates many systematic parameters. The method incorporates many systematic parameters. The DOC calculate single figurement,eliminate subjectively weighed criteria follow in close quarter the well known and acknowledged DOC approach and also ensure simultaneous optimization of aircraft DOC.

Other experimental methods involve combination of the pilot and either the real vehicle or a simulation of the same.Usualy there are two data outputs of experimental methods – performance measurement and pilot evaluation. The pilot’s task performance and workload control in achieving the performance is done. Pilot evaluation whereby there is subjective assessment of the aircraft handling qualities

The evaluation data mostly consists of two parts namely. one, pilots comments on the oberservation he made and two, the ratings he assigns these being the two most important data on the closed – loop pilot-airplane combination which the engineer has.

Conclusion

In a nutshell, both computation analysis methods and experimental testing techniques in aircraft engineering evaluation are important and vital methods of aircraft evaluation depending on the Specific case and situation and also the aircraft model.

All in all communication breakdown between the pilot and the aircraft engineer who carries out these tests could be a potential barrier to efficient evaluation and this should be avoided at all costs to avoid fatal accidents and losses. The two professionals should adopt a side by side working mode during check analysis and flight checks just as the Wright brothers did back in the day. The pilot from his complete system viewpoint and the engineer with his aircraft response view should be harmonized to bring comprehensive analyses. Although high end research is being done in these two areas there still exists various limiting capacities here and there hindering a smooth flow of evaluation of aircrafts.