The name of Sir Henry Tizard always induces in me feelings of humility: I have succeeded him in an office to which he lent distinction for ten years, but I can never hope to emulate his drive and efficiency, nor compete with his almost legendary chairmanship. I remember that in 1964, soon after I was appointed to the Chair of the Aeronautical Research Council, Dover Publications decided to reprint Goldstein's “Modern Developments in Fluid Dynamics“, and I was invited to contribute a Preface. I got out my set of the earlier edition, to be reminded that the first Preface bore the signature H. T. Tizard: somehow, it seemed almost indecent that I, or anyone, should have to write a new Preface. Such are my feelings about Tizard's name and fame: I daresay many of my generation feel as I do.

This is the Age of Space Flight. Satellites orbiting the earth are the heralds of more spectacular demonstrations to come. “Man in earth orbit” is the prologue to manned missions in the alien environment of lunar space.

Basically, the objectives of the US space programme are to:

• 1. Expand human knowledge of atmosphere and space.

• 2. Improve the use, speed, performance, safety and efficiency of aeronautical and space vehicles.

• 3. Develop and operate vehicles capable of carrying instruments, equipment, supplies and living organisms through space.

• 4. Study the potential benefits of space activities for peaceful and scientific purposes.

• 5. Preserve the role of the US as a leader in aeronautical and space science and technology, and in the application thereof to peaceful activities.

I am deeply conscious of the honour to the New Zealand gliding movement and to myself as its representative to be asked to deliver the First George Bolt Aviation Memorial Lecture. George Bolt was one of the first New Zealanders to construct and fly his own glider in the early years of this century, and for the remainder of his life he retained an intense interest in gliding, even when deeply involved in increasingly complex powered aircraft. He agreed to become the first Chairman of the Technical Committee of the New Zealand Gliding Association, and as such helped the movement in its struggles to get back into the air after the Second World War. It is thanks to him that the Association was established on a sound technical basis, as the first post-war Director of Civil Aviation made it clear that the New Zealand Gliding Association would not be recognised until a competent Technical Committee was formed.

Using Glauert's analysis and taking into account the restraint due to the surface of the sea, lifting line theory is applied to calculate the distribution of loading, downwash velocity and vortex drag of a “Finn” dinghy's sail when upright. It appears that the loading can probably be represented with sufficient accuracy by

I=I0(sin θ+sin 2θ)

where k is largely dependent on the apparent twist in the sail and has a value generally of the order of 0-5, that the apparent twist may not be twist at all in the aerodynamic sense, and that the vortex drag is considerably greater than it would be if it were possible to make a sail to give elliptic loading.

The pattern of flow at low Reynolds Numbers about an aerofoil in a cascade has been illustrated by the hydrogen-bubble flow-visualisation technique. The method has also been adapted tor the accurate experimental determination of the position of boundary-layer separation. Results of the investigation are presented graphically together with photographs showing the general behaviour of the flow in the wake.

In the analysis of cooled gas turbine cycles, the quantity of heat removed by the coolant is termed as “cooling loss”. In the literature, these cooling losses are accounted for by the use of either

(a) Cooling Loss Factor, or

(b) Cooling Number.

Brown defines Cooling Loss Factor (CLF) as a ratio of heat removed by coolant per unit time divided by the total turbine output per unit time.

Traupel defines the Cooling Number (CN) as the ratio of heat loss to isentropic enthalpy drop.

Cohen and Martin use the CLF in their analyses and May uses the CN.

It is the purpose of this note to give a simple correlation of the two and to suggest a new definition to account for these losses.

For a simple undamped vibrator driven by a force whose frequency varies linearly with time, simple algebraic expressions are derived which give values for the maximum amplitude performed by the vibrator and for the frequency of the driving force where the maximum displacement occurs. Driving forces of both increasing and decreasing frequencies are considered.

Measurements of cylinder drag in two-dimensional flow are readily available. In contrast, drag data for other cylinder configurations in which the flow is not strictly two-dimensional, for example free-ended cylinders or cylinders joined to a plane wall, is less plentiful. Some results for the former case have been given by Wiesels-berger and others, obtained at Gottingen and NPL, have been presented by Goldstein.

This note discusses some preliminary drag measurements made for turbulent flow about circular cylinders which were joined to plane parallel walls at each end. Such configurations appear repeatedly in practice. The justification for applying the classical free-ended cylinder data to this problem is slight since, in this case, flow may occur round the ends of the cylinder from the high pressure region upstream to the low pressure wake.

The solution of a problem in plane elasticity can be associated with a minimum energy principle, involving the minimisation of a double integral subject to certain boundary conditions. In 1933, Kantorovich proposed a method which reduced this problem to that of finding the minimum of a single integral. He chose part of the solution a priori (in accordance with the character of the problem) which left only one undetermined function in one of the variables. This unknown function could then be found through the solution to an ordinary differential equation. He then constructed a second approximation by introducing two unknown functions which led to the solution of two simultaneous differential equations. Again the accuracy of the solution was dependent on the initial choice for part of the function; so also was the rate of convergence.

An investigation has been made into the stability of compressor blade flutter in separating flow in the presence of external perturbations. The fluttering blade is an example of a hysteretic system governed by a non-linear difference-differential equation for which an analytical approach is not possible and for which the authors originally proposed this new treatment. For design purposes a digital computer has been used to produce stability diagrams under specified conditions including blade torsion. The solution for the response is also available if required. The method involves forming the non-linear feedback analogue to the blade system and which has behaviour governed by the same equation as that studied. The stability is then studied on a digital computer in the presence of small external perturbations by means of a dual input describing function applied to the analogous feedback system with consideration given to the aerodynamic phase lag involved and initially small blade torsional motion.

In ref. 1 an analytical solution was given for the one-dimensional distribution of temperature in a web of an idealised, symmetric, multi-cell wing structure when symmetrically heated. It was assumed that the convective heat transfer coefficient, h, was constant, but the adiabatic wall temperature variation was assumed to be either an instantaneous or a linear function of time.

The purpose of the present paper is to indicate the application of an alternative, approximate method of heat flow analysis due to Biot and to show thereby how the usefulness of the results in ref. 1 can be extended by eliminating the assumption therein that the skin temperature was uniform at any given time. The notation of ref. 1 is used with additions as defined in the paper.

Submerged intakes are widely used on aircraft as a means of supplying internal flow systems with ambient air. It is the purpose of this note to show by analysis of existing experimental data that the boundary layer at the location of the submerged intake can have an appreciable effect on its performance.

Information here relates to the NACA type of divergent submerged intake with a ramp angle, a, of 7° and an aspect ratio, w/d, of 4 because this particular combination of planform and geometry is now almost universally used.

In the vibration of isotropic rectangular plates, the phenomenon of the simultaneous excitation of two separate modes having equal frequencies is well known. Wallerobserved complex nodal patterns on isotropic rectangular plates, and she stated that such combinations were possible because of the internal damping of the plates, which reduced the sharpness of resonance.

Warburton considered the existence of modes m/n±n/m for a clamped plate and showed that when a plate is square, for the mode 4/2 + 2/4, the nodal lines do not lie parallel to the edges of the plate. Furthermore, it was proved that for a square clamped plate, the modes m/n±n/m have discrete frequencies.

The aim of this note is to compare the plane turbulent free jet diffusing in an infinite stagnant ambient environment with the corresponding plane turbulent wall jet on a smooth boundary regarding the three important characteristics, namely the velocity distribution and the variation of the velocity and length scales, in the region of developed flow.

In an earlier note Case reported direct measurements of entrainment on a rotating disc. More comprehensive measurements, made subsequently to those of Case and using essentially the same technique, are reported here. Two different sizes of drum were used in the present investigation, the flow within the drum in each case being smoothed by the use of a honeycomb and screens as well as a baffle at entry (see Fig. 1).

The entrainment was also deduced from yawmeter and total pressure traverses through the boundary layer on the disc in free air, the integrated crossflow component of the velocity distribution through the layer evidently representing the entrainment up to the radius at which the traverses were performed. A typical measured crossflow profile is shown in Fig. 2.