Numerical Study in Wing Tip Vortex for a Modified Commercial Boeing Aircraft

Recent studies have shown that the use of winglets in aircrafts wing tips have been able to reduce fuel consumption by reducing the lift-induced drag caused by wing tip vortex. This paper presents a 3-D numerical study to analyze the drag and lift forces, and the behavior of the vortexes generated in the wing tips from a modified commercial Boeing aircraft 767-300/ER. This type of aircraft does not contain winglets to control the wing tip vortex, therefore, the aerodynamic effects were analyzed adding two models of winglets to the wing tip. The first one is the vortex diffuser winglet and the second one is the tip fence winglet. The analyses were made for steady state and compressible flow, for a constant Mach number. The results show that the vortex diffuser winglet gives the best results, reducing the core velocity of the wing tip vortex up to 19%, the total drag force of the aircraft up to 3.6% and it leads to a lift increase of up to 2.4% with respect to the original aircraft without winglets.

Anomalous width variation for rarefactive ion acoustic solitary waves in the presence of warm multi-ions

A previous analysis of anomalous width variation for a single-ion rarefactive solitary wave [S. S. Ghosh and A. N. Sekar Iyengar, Phys. Plasmas, 4, 3204 (1997)] has been extended to a multi-ion species, and shows that the corresponding width–amplitude characteristics depend crucially on the respective ion concentrations; for example, with increasing light-ion concentration, an ‘increasing- width’ rarefactive solitary wave transforms to a ‘decreasing-width’ one for a constant Mach number exhibiting an overall U-shaped variation profile. The influence of the second ion species generally decreases with increasing amplitude, being maximum for the single to multi-ion transition. However, in the neighbourhood of double-layer-like solutions, the influence again becomes prominent, which may be associated with the corresponding energy–amplitude relations for both the ions.

Ideal magnetohydrodynamic equilibria with helical symmetry and incompressible flows

A recent study on axisymmetric ideal magnetohydrodynamic equilibria with incompressible flows [H. Tasso and G. N. Throumoulopoulos, Phys. Plasmas5, 2378 (1998)] is extended to the generic case of helically symmetric equilibria with incompressible flows. It is shown that the equilibrium states of the system under consideration are governed by an elliptic partial differential equation for the helical magnetic flux function containing five surface quantities along with a relation for the pressure. The above-mentioned equation can be transformed to one possessing a differential part identical in form to the corresponding static equilibrium equation, which is amenable to several classes of analytical solutions. In particular, equilibria with electric fields perpendicular to the magnetic surfaces and non-constant-Mach-number flows are constructed. Unlike the case in axisymmetric equilibria with isothermal magnetic surfaces, helically symmetric T = T(ψ) equilibria are overdetermined, i.e. in this case the equilibrium equations reduce to a set of eight ordinary differential equations with seven surface quantities. In addition, the non-existence is proved of incompressible helically symmetric equilibria with (a) purely helical flows and (b) non-parallel flows with isothermal magnetic surfaces and with the magnetic field modulus a surface quantity (omnigenous equilibria).

The Use of Tandem Ejector Pumps in an Intermittent Blowdown Tunnel

A tandem ejector pumping system has been applied to an intermittent blowdown tunnel for cascade testing to achieve sub-atmospheric exit pressures and extend the operating range substantially. The ejectors are run from the same supply as the tunnel itself, but because they are only used at low Reynolds numbers when the cascade mass flow is small the overall running costs are kept low. A conventional one-dimensional ejector theory is developed in a new way for such an application as this, where the driving mass flow needs to be known for constant Mach number of the driven stream (the cascade exit Mach number). Several ejector geometries were tested in various configurations in a one-tenth scale model before the prototype ejectors were developed. It is demonstrated that by suitable grouping of terms it is possible to correlate both model and prototype ejector performance, and that this performance can be predicted sufficiently accurately by the theoretical model to justify its use as a design tool. The method of operating two ejectors in tandem depends on the interaction of the exit stream of the first (forming the driven stream of the second) and the driver stream of the second. This is not immediately obvious, and is discussed fully in the light of the achieved performance.

The Development of Programs for Minimum-time Tracks

This paper outlines the phase of the flight planning operation in which airlines calculate minimum-time tracks for the purpose of advising oceanic control centres of their needs prior to the definition of the Organised Track System (OTS). The results are based on 12- and 24-hour forecasts for a level of 250 mb and aircraft assumed to fly at a constant Mach number of 0·82. The problem is defined in terms of a network in which the domestic route structure on each side of the North Atlantic is represented.