The program VICONOPT is used to find the optimum (least mass) dimensions of a range of stiffened wing panels which are subject to buckling and material strength constraints and are loaded in axial compression with a sinusoidal manufacturing imperfection. Design plots are presented to show the effects that various rib spacings and stiffener types have on optimum design mass. A simplified model of a complete wing box is used to illustrate the design of a full wing panel and plots of optimum values of design variables at various stations along the wing have been obtained. The results were chosen to illustrate the practicality of optimisation with reference to manufacture of a full wing panel and to show the effect of changing the sophistication of modelling and theory used for the range of panels considered. The important aspects of the choice of design variables and design concepts are highlighted and percentage savings in mass, compared with an optimum metal panel design, are given for the various (global) optima found along with some examples of (rejected) local optima.

Although mini-tufts are considered generally to show the surface flow direction on windswept surfaces, there is some uncertainty about their correct interpretation, particularly as three-dimensional flows approach separation. This note provides some guidance on this controversial question, based on experience with mini-tufts on wings, fins and canards in the DRA 13 ft x 9 ft low speed wind-tunnel at Bedford.

An illustration of the value of the technique is given. Mini-tuft photographs are used to identify the trailing edge condition which relates to the classification of the steady and fluctuation pressure distributions observed a swept wing with a conical, separated flow.

This note presents the results of the application of a momentum control surface analysis to the estimation of the drag of bodies and surfaces placed in the test section of a windtunnel. The assumptions of the method are stated and accuracy of the method considered with particular reference to the drag of riblet surfaces at high subsonic speeds, the drag of two-dimensional cavities at both high subsonic and low supersonic speeds, and the drag of manipulators at high subsonic speeds.

An experimental investigation has been made into the effects of riblets on the drag in a rectangular duct of aspect ratio 10. It has been found that a maximum drag reduction of approximately 10% occurs in fully developed turbulent flow. This figure is larger than the 6–8% drag reduction usually found for external flow. The maximum drag reduction occurred when the height of the riblets was between 7 and 13 wall units. Analysis of the developing region of the flow has shown a maximum drag reduction of approximately 8% at a wall unit value of 13, consistent with results in external flows. The effects of riblets on transition has also been investigated. It was found that riblets delayed transition by 2–4% in critical Re as measured by peak flatness, and caused some extension in the length of the transition process, so that the completion of transition was delayed by between 4–8%, with the stronger effect at the lower Reynolds numbers.

Vortex breakdown phenomenon remains a challenging aspect of the flow over delta wings at high angle of attack. The observations of vortex breakdown and related interpretations for vortex tube experiments and delta wings are summarised in several review articles. The theoretical models of the phenomena are described in detail in References 1, 2, 3 and 7. These theoretical models are not complete enough to predict breakdown location over delta wings. The purpose of this note is to review several existing criteria and correlations for vortex breakdown over delta wings using a large database. The earliest criteria for delta wings was suggested by Lambourne and Bryer.