An investigation into inviscid theory applied to manoeuvring bodies in fluid

Hatam, A

Abstract

This thesis focuses on the appropriateness of the inviscid potential flow model for determining
the manoeuvring characteristics of a body moving through fluid. This model is
widespread in many key applications for ships, submarines, aircraft, rockets, missiles, as
well as for the swimming of marine animals and the flying of birds. Despite the widespread
use, there are important anomalies in the theory, in particular relating to the lift induced
by shed vorticity. These anomalies have been identified in the recent publication by Chadwick
which states that the lift has been calculated incorrectly, and apparent agreement
in wing theory is fortuitous due to "two wrongs" in the theory giving the right answer.
In this thesis, the inviscid flow is further investigated, and the work of Chadwick is
extended and developed further.
In the first two chapters, careful description of the basic fluid concepts and then derivation
of the fluid equations is given. In chapter four, the lift and drag on a wing are considered.
The lift evaluation comes out to be half that expected and this is in agreement and
essentially repeats the analysis in Chadwick's recent paper [1]. However, the analysis is
extended to evaluate the drag, and surprisingly the drag is determined to be infinite.
In chapter five, further investigation into the lift on a thin wing is undertaken, and it is
seen that there is uncalculated jump in the lift at the trailing edge. This is calculated
from the pressure integral across the trailing edge.
Finally, in chapter six, inviscid flow slender body theory is investigated. A complete near
field expansion is given for a singularity distribution of sources over an infinite line by
using the Fourier transform method. In this thesis, this result is extended for the finite
line by using the integral splitting technique. By taking the ends to infinity, the result for
the infinite line is recovered and the two methods shown to be equivalent for this specific
case. The method presented here relies upon allowing a singular wake to exist behind the
body. This introduces non-uniqueness in the matching and the implications of this are
discussed.
Appropriate references to other researchers are given in individual introductions for each
chapter.

Citation

Hatam, A. An investigation into inviscid theory applied to manoeuvring bodies in fluid. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Publicly Available Date: Oct 3, 2012
• Award Date: Jan 1, 2005