Filtering by
- All Subjects: engineering
- All Subjects: Aircrafts
- All Subjects: Supersonic
The objective of this thesis is to conduct a case study into the Bell X-2, an early supersonic research aircraft utilizing a modern perspective and computational tools. The Bell X-2 was the second in a series of supersonic research aircraft created by Bell Aviation Corporation, designed to help engineers to explore this new region of flight. The goal of the X-2 was to gather data on high Mach Number and high-altitude flight as well as aerodynamic heating. The X-2 had poor lateral stability resulting in it being unstable at high Mach Numbers and moderate angles of attack. The program was full of new and unforeseen technical challenges resulting in many delays and tragedies. The program ended when stability problems resulted in a fatal crash destroying the aircraft and killing the test pilot. This case study addresses the historical background of the program, human influence, the stability problems encountered and conducting a stability analysis of the aircraft. To conduct the stability analysis, the potential flow solver, VORLAX, was used to gather aerodynamic coefficient data of the X-2 and determine if these stability problems could be determined from the data obtained. By comparing the results from VORLAX to a wind tunnel study, I determined that the poor lateral directional stability and control coupling issues were foreseeable in the initial design.
Add in the complexities of supersonic flow and the challenge increases exponentially.
One possible, and often common, pathway for this design is to jump straight into detailed
volume grid computational fluid dynamics (CFD), in which the physics of supersonic
flow are modeled directly but at a high computational cost and thus an incredibly long
design process. Classical aerodynamics experts have published work describing a process
which can be followed which might bypass the need for detailed CFD altogether.
This work outlines how successfully a simple vortex lattice panel method CFDcode can be used in the design process for a Mach 1.3 cruise speed airline wing concept.
Specifically, the success of the wing design is measured in its ability to operate subcritically (i.e. free of shock waves) even in a free stream flow which is faster than the
speed of sound. By using a modified version of Simple Sweep Theory, design goals are
described almost entirely based on defined critical pressure coefficients and critical Mach
numbers. The marks of a well-designed wing are discussed in depth and how these traits
will naturally lend themselves to a well-suited supersonic wing.
Unfortunately, inconsistencies with the published work are revealed by detailedCFD validation runs to be extensive and large in magnitude. These inconsistencies likely
have roots in several concepts related to supersonic compressible flow which are
explored in detail. The conclusion is made that the theory referenced in this work by the
classical aerodynamicists is incorrect and/or incomplete. The true explanation for the
perplexing shock wave phenomenon observed certainly lies in some convolution of the
factors discussed in this thesis. Much work can still be performed in the way of creating
an empirical model for shock wave formation across a highly swept wing with blunt
leading-edge airfoils.