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I CAN hardly say how much I appreciate the honour your Council has conferred on me in asking me to deliver the James Forrest lecture this year. I realise fully the…
I CAN hardly say how much I appreciate the honour your Council has conferred on me in asking me to deliver the James Forrest lecture this year. I realise fully the difficulty of the task that has been set me, for it is no easy matter to follow in the footsteps of the illustrious men who have previously addressed you on aeronautical subjects. I will, however, do the best I can to give you some idea of the development of aircraft since Professor R. V. Southwell delivered his excellent review in 1930†, and in doing so, I will not fail to bear in mind the “leit motif” of this series of lectures, which is to trace, wherever possible, the interdependence of abstract science and engineering. My lecture is, in fact, arranged with that object mainly in view, for I shall endeavour to point out the advances that have been made in the technique of research methods, and the nature of the new knowledge of aerodynamic phenomena which has resulted from them, and to show, as far as I can, how this new knowledge has reacted on the practical design of aircraft.
THERE have been two previous James Forrest Lectures dealing with aeronautics. In 1912, Mr. Mallock addressed this Institution on “Aerial Flight,” and in 1914, Dr…
THERE have been two previous James Forrest Lectures dealing with aeronautics. In 1912, Mr. Mallock addressed this Institution on “Aerial Flight,” and in 1914, Dr. Lanchcster took as his subject “The Flying‐Machine from an Engineering Standpoint.”
The purpose of this study is to develop a new method of lines for one-dimensional (1D) advection-reaction-diffusion (ADR) equations that is conservative and provides…
The purpose of this study is to develop a new method of lines for one-dimensional (1D) advection-reaction-diffusion (ADR) equations that is conservative and provides piecewise analytical solutions in space, compare it with other finite-difference discretizations and assess the effects of advection and reaction on both 1D and two-dimensional (2D) problems.
A conservative method of lines based on the piecewise analytical integration of the two-point boundary value problems that result from the local solution of the advection-diffusion operator subject to the continuity of the dependent variables and their fluxes at the control volume boundaries is presented. The method results in nonlinear first-order, ordinary differential equations in time for the nodal values of the dependent variables at three adjacent grid points and triangular mass and source matrices, reduces to the well-known exponentially fitted techniques for constant coefficients and equally spaced grids and provides continuous solutions in space.
The conservative method of lines presented here results in three-point finite difference equations for the nodal values, implicitly treats the advection and diffusion terms and is unconditionally stable if the reaction terms are implicitly treated. The method is shown to be more accurate than other three-point, exponentially fitted methods for nonlinear problems with interior and/or boundary layers and/or source/reaction terms. The effects of linear advection in 1D reacting flow problems indicates that the wave front steepens as it approaches the downstream boundary, whereas its back corresponds to a translation of the initial conditions; for nonlinear advection, the wave front exhibits steepening but the wave back shows a linear dependence on space. For a system of two nonlinearly coupled, 2D ADR equations, it is shown that a counter-clockwise rotating vortical field stretches the spiral whose tip drifts about the center of the domain, whereas a clock-wise rotating one compresses the wave and thickens its arms.
A new, conservative method of lines that implicitly treats the advection and diffusion terms and provides piecewise-exponential solutions in space is presented and applied to some 1D and 2D advection reactions.
THIS PAPER presents a study of the performance characteristics of finite width stationary externally pressurized rectangular bearings. Two types of bearings are…
THIS PAPER presents a study of the performance characteristics of finite width stationary externally pressurized rectangular bearings. Two types of bearings are considered, namely, the plain and initially tilted pad bearings. The bearings were lubricated by using incompressible fluid. The study includes:
Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics and publications of other similar research bodies as issued
WITHIN the limits set by practical considerations, stresses in engineering materials entail almost exactly proportionate strains. But in bodies of elongated shape, such as…
WITHIN the limits set by practical considerations, stresses in engineering materials entail almost exactly proportionate strains. But in bodies of elongated shape, such as rods or thin sheets, displacements are not necessarily proportionate to the strains of which they are the integrated result, and hence, for such bodies, Hooke's law may hold in respect of some types of displacement but not of others. Applying end thrust to a long straight rod (or strut), and measuring the consequent approach of the ends, we find that this increases faster than in proportion to the thrust; under a load which would have been quite safe applied as tension, the strut bows largely and ceases to have value as a compression member.
THE MAIN objective of this work is to reveal the performance characteristics of sliding externally pressurized rectangular bearings and to get an adequate understanding of…
THE MAIN objective of this work is to reveal the performance characteristics of sliding externally pressurized rectangular bearings and to get an adequate understanding of the behaviour of such bearings.
The aeronautical engineer is all the time struggling to improve aircraft performance. His problem is essentially the attainment of maximum economy—to get the maximum duty out of the material at his disposal. In the field of aerodynamics his progress depends upon the progress of his knowledge of the behaviour of air in a variety of circumstances. In the field of structures it depends upon the exactness of his knowledge of the distribution of stress and strain. In the field of oscillations, where the influences of aerodynamics, structures and inertia combine, he needs the support of the theory of vibration.
This is a textbook on a subject that has been developed almost entirely within the last decade. It deals with a method of solving problems by successive approximations that have wide applications in engineering and physics.
THE stiffness of an aeroplane wing is usually considered in terms of its torsional and llexural stiffnesses as measured at the “mid‐aileron” and “equivalent tip”…
THE stiffness of an aeroplane wing is usually considered in terms of its torsional and llexural stiffnesses as measured at the “mid‐aileron” and “equivalent tip” sections(1), (2). It appears at present that the stiffness in torsion is more significant than that in flexure, partly because high torsional stiffness is necessary to prevent not only flutter but also reversal of aileron control and divergence(1), (2), both of which are independent of llexural stiff‐ness ; and partly because it is found in practice that when a wing is designed to meet minimum existing strength requirements alone, its torsional stiffness may be inadequate whereas its llexural stiffness is commonly sufficient. The more important of the two torsional stiff‐nesses (“mid‐aileron” and “equivalent‐tip”) is that at the “mid‐aileron” section. The present paper examines the effect of the various parameters on the torsional stiffness of a tapered rectangular tube of proportions representative of an aeroplane wing under a con‐centrated torque applied at a section equivalent to the average “mid‐aileron” section. The analysis of the problem is based on the stress distribution in an axially constrained tapered tube given by Williams in R. & M. 1761(3), and the stiffness obtained is compared with that for a tube with the simple shear stress distribution of the Bredt‐Batho type for a tube with free ends. The similar problem for a uniform tube has already been solved from the equations of reference (3) in R. & M. 1790(4).