Kites are currently used in a number of applications (anemometry, aerial platform, traction), but very little information is available for the systematic design of kite systems. An experimental technique based on an instrumented tether for single-line kites is described. This was used to measure the performance of a variety of single-line kites. The analysis techniques are briefly outlined, and incorporate allowances for kite unsteadiness, the displacement of the kite from the anemometers, extrapolation of the line tension from the tether to the kite, and the kite’s velocity relative to the ground. The results are correlated with aspects of kite design, and specific recommendations for kite applications are made.

In 1954, Preston introduced a new concept of skin friction measurement in turbulent flows by using a surface pitot tube. Since then considerable controversy has risen in the use of Preston tubes for skin friction measurements. However, Head and Rechenberg investigated Preston tubes extensively and confirmed the validity of the Preston tube method. Recently Rajaratnam has given a theoretical calibration curve for the Preston tube using logarithmic velocity distribution for the boundary layer velocity profile.

Since some aspect of fluid dynamics is involved in the design or operation of many items of plant in the electrical supply industry, this survey is confined to those items which are peculiar to the industry and whose performances are directly related to their aerodynamic behaviour. Three main problems will be discussed namely, the internal flows in boilers and natural draught cooling towers and the aerodynamic behaviour of overhead lines. In addition, the aerodynamic aspects of current and recently initiated field experiments will be considered.

As this is a wide subject area with many specialised fields, a broad review from a systems viewpoint would appear to serve the purposes of this Symposium best. Also, such a review may help to show that the importance of range instrumentation in upper atmosphere research is rather more fundamental and widespread than generally appreciated.

A problem, commonly met in scientific and engineering experiments, is the determination of the damping of a system, given a recorded trace (such as that from a uv recorder) of the free damped oscillation following a disturbance. The simplest and most tedious method is to plot the logarithm of the peak amplitude at each half cycle against cycle number. Other methods have been given by Hogley and Gimmestad, Bratt and Wilcox and Crawford. However, the problem is so common, and the experiments and methods of recording the results so diverse, it is felt that a further method could find a place in the range of those available.

An Euler correction method is developed for unsteady, transonic inviscid flows. The strategy of this method is to treat the flow-field behind the shock as rotational flow and elsewhere as irrotational flow. The solution for the irrotational flow is obtained by solving the unsteady full-potential equation using Jameson's rotated time-marching finite-difference scheme. Clebsch's representation of velocity is followed for rotational flow. In this representation the velocities are decomposed into a potential part and a rotational part written in terms of scalar functions. The potential part is computed from the unsteady full potential equation with appropriate modification based on Clebsch's representation of velocity. The rotational part is obtained analytically from the unsteady momentum equation written in terms of Clebsch variables. This method is applied to compute the unsteady flow-field characteristics for an oscillating NACA 64A010 aerofoil. The results of the present calculation are found to be in good agreement with both Euler solution and experimental results.

It is a great honour to be invited to present a survey of the aeronautical research in the Netherlands to this distinguished audience and I wish to express my thanks to the Council of the Royal Aeronautical Society for giving me the opportunity to deliver this lecture. The more I appreciate it in view of the friendship between our two countries, between the Society and its Dutch counterpart and the personal friendship with so many present on this occasion.

It is my intention to give a survey of some of the work performed in the Netherlands in the post-war period and to describe briefly the main installations which are now available or under construction. I hope that I will be able to give you an impression of the scope and the nature of the aeronautical research activities in the Netherlands. These activities are being directed in the first place by the immediate needs of the industry and the aircraft operators; and in the second place by the desire to contribute to the general development of the art, thereby also supporting the exchange of results on an international basis, even more essential than before, considering the rapidly growing importance of aviation in its broadest sense.

Before entering into more technical matters it may be worthwhile to give very briefly an outline of the present organisation of aeronautical research and development in the Netherlands.

This paper defines Internal Aerodynamics and via similarity generalises the concept to include internal flows of fluids other than air.

Variable area ducted flows are considered distinguishing one, two and three-dimensional treatments and the difference between accelerating and diffusing flows is stressed. The design of variable area ducts using ideal inviscid fluid theory, ideal fluid plus boundary layer theory and inviscid but rotational fluid theory is discussed. The success and limitations of these theories with reference to contractions and diffusers is surveyed The particular difficulty of a diffusing flow as affected by entry velocity profile and turbulence is considered.

From the problem of simulating entry velocity profiles arises the need for the generation of required velocity profiles in duct systems. Examples of methods of generation and difficulties are discussed.

Next follows a series of examples of internal flow problems.

The radial flow diffuser is considered as an example of the interaction of viscous and inertia effects. An approximate theoretical treatment is given and the real flow, with the occurrence of reverse transition, is described.

The deliberate production of a reversed flow regime for flame stabilisation is described with reference to a marine boiler register Aspects of pressure drop and stability are considered.

Secondary flow is defined and the origin in the distortion of the upstream vorticity field is described. The case of a strut wall junction is given with details of the downstream flow where the secondary flow produces apparent multiple wakes from a single strut.

Air flow excited vibration of heat exchanger tubes is described. Different mechanisms resulting in transverse or streamwise oscillations and the coupled modes of tube rows are discussed.

Finally the paper emphasises the large available body of information in internal aerodynamics, largely of aeronautical origin, and considers its usefulness and limitations for the problems discussed.

A detailed survey of a delta wing of 70° sweep has been performed at M = 2.5. The measurements include upper- and lower-surface pressure distributions, schlieren photographs, vapour-screen photographs and surface oil-flow visualisation. The results have been compared with thin-shock-layer theory and various other predictions.

A probe is described which will detect contamination, by driver gas, of the test section flow in a shock tunnel. It is a continuously sampling device, which responds to the difference between the ambient speed of sound in the driver gas and the test gas. The probe is compact, easy to construct, and can be used for detection of driver gas in routine testing. The theory of the probe is explained, and experiments are reported which confirm its effectiveness.

The responses of systems, whose equations of motion are linear, to arbitrary applied forces are conveniently calculable by the use of impulsive or indicial admittances. Expressions for these admittances are here given explicity for some simple dynamical chains and the procedure for their calculation in chains with more degrees of freedom is outlined. Some general characteristics of the dynamical chains are also examined.

Curves are presented which, together with a knowledge of the intake performance, enable ram-jet thrust coefficients and specific consumption figures to be obtained quickly and accurately in the range M = 1·0 to 3·0.

As pointed out in previous work, in the method of collocation the functions used usually need not be orthogonal or integrable in closed form. Therefore function of different types may be mixed together in representing unknown quantities. Such function may be aptly called hybrid functions. Also, it has been found that usually it is better to represent unknown quantities by similarly looking functions instead of by a series involving higher harmonics. The idea is that by using similar looking functions it is possible to avoid poor regions for collocation, such as near nodal points, and so on, and closer fit in certain regions is assured. Thus if one knows approximately what the function sought looks like, one should try to find a set of function all of which resemble this desired shape, instead of taking an arbitrary set of harmonics when using the method of collocation. Simple examples below illustrate this approach and indicate the good results that can be expected in general.

A sequence of high Reynolds number two-dimensional entry flow problems is considered by varying the form of the entry profile from one representing uniform shear to one representing different parts of a Poiseuille profile. The detailed development of the entry flow is illustrated in a few cases. The entry length, pressure drop, and pressure loss in the entry region are given in each case.

The ability to operate when runways are flooded or slush-covered to some degree, must be demonstrated during the certification programme of any new civil transport aircraft. Failure to meet the requirements laid down will result in operating restrictions which may jeopardise the sales prospects of the aircraft. Most other types of aircraft will also have to operate occasionally in these adverse conditions.

The main problems result from the spray generated at the wheels, and are engine malfunction due to spray ingestion and damage due to its impingement on the airframe. An associated problem is the packing of slush into ducts, flap cavities, undercarriage bays, etc, with the attendant risks of damage to internal systems and jamming of mechanical parts. There is also a large additional drag load on the aircraft, due to the displacement of fluid by wheels and to spray impact on the airframe: this increases roughly in proportion to the depth and effectively limits the slush depth that can be tolerated on the runway. For many aircraft this limit is little more than one centimetre.

One of the great challenges of our time lies in the exploration of space. Part of this challenge has already been fulfilled but, up to this date, the transport of men and materials has been accomplished by means of expendable booster systems. In order to meet this challenge effectively, a new, fully reusable transportation system has been conceived which will be dramatically lower in overall cost than present-day launch systems. The proposed space shuttle is a fully reusable spacecraft consisting of a booster and an orbiter. A key factor in the design of the space shuttle is the selection and development of materials. Many current materials which have been widely and successfully used in space vehicles were developed for the most part with only a single short-time use requirement. The reusable, long-life requirements of the shuttle vehicle necessitates re-evaluation of the suitability of existing materials for this distinctly more demanding task for materials.

Kinetic heating, which is associated with supersonic flight, is probably the greatest challenge which has confronted the structural engineer, since the design and analysis of affected structures requires a radical extension of current practice. For example, the laws of heat transfer and the effects of high temperature on structural materials become important factors in structural analysis. To obtain a clear appreciation of the situation it is therefore necessary for the designers of the structure to become familiar with these factors, together with certain aspects of boundary layer theory.