A choked nozzle installation suitable tor the absolute calibration of air flowmeters over a limited flow range is described. An entry package is prescribed to ensure that near ideal flow conditions are presented to the nozzle. This package should remove swirl and flow distortions from most entry flows.

Provided that the instructions given in this note are followed meticulously then the quoted discharge coefficients for the nozzle may be guaranteed to better than ±0-25% at Reynolds numbers greater than 106. The overall accuracy of flow calibrations are then dependent only on the accuracy with which the mean gas thermodynamic properties and condition of state at the nozzle entry can be determined.

The flow in a two-dimensional curved wall jet with different initial gaps between the nozzle exit and the leading edge of the wall was probed at various stations along the jet. The jet slot thickness, the jet exit velocity and the radius of the wall were kept constant. It was found that the region close to the leading edge of the wall behaved like a settling zone. In this zone the type of flow changed from a free jet to a curved wall jet. The length required for settling depended on gap size and was less than that of the plane wall jet. Gap effects on surface pressure distribution and angular position of separation were examined. The hysteresis phenomenon associated with gaps was investigated.

Two probes which have been developed at the University of Toronto's Institute for Aerospace Studies for the purpose of determining the complete velocity vector in subsonic flow are described. That is, both probes provide the magnitude of the velocity at a point plus the two angles which determine the vector's orientation. The first probe, which also measures static pressure, was developed by K. Dau to determine wake properties behind a blowing wing. It uses a multiple pressure-hole technique. The second probe was originated by K. Dau and D. Surry and experimentally developed by M. McLeod. It is basically a spinning hot-wire probe whose periodic waveform uniquely defines the complete velocity vector.

The description of the LUMINA element in T.N. 11 is followed by another three-dimensional interpolation element, called HERMES 8, available in the ASKA language and briefly mentioned in ref. 1. Just as the LUMINA set, the HERMES element represents a general hexahedronal element with curved faces and has proved a most useful component block for three-dimensional analysis of complex bodies. The cardinal idea underlying the HERMES development aims at combining the advantages of the Lagrangian and Hermitian interpolation techniques.

Pressure recovery measurements in a straight pipe with crossflow-generated entry velocity distributions suggested substantial effects of inflow distortion on the pressure recovery downstream of a sudden enlargement in area. This note reports results of actual measurements in the same pipe equipped with entry sections of various reduced diameters providing sudden area enlargement ratios of 1.33, 1.71, 2.04, and 3.52. The results have practical bearing on the performance of settling pipes located at diffuser exits where, in general, velocity distributions are significantly non-uniform. In addition, the results provide information on the momentum content of the crossflow-generated velocity distribution.

Tables of equilibrium thermodynamic properties of the ionized gas formed behind strong shock waves in Helium are presented, in the Mach number range 10 to 30, for initial pressures of 0-1, 0-5, 1, 5, 10, 50, 100 torr. The effect of the inclusion of the full partition function series is demonstrated in the Mach number range 20 to 30.

A numerical solution has been developed such that the only experimental quantities required for its use are the shock Mach number and the pre-shock conditions.

It is generally accepted that the displacement patterns chosen to represent the deformation of a finite element should be such that there is complete compatibility with adjacent elements. Although some writers have doubted the necessity for the complete satisfaction of compatibility away from the reference nodes, provided the displacement pattern is capable of assuming certain uniform strain states, the desirability of complete compatibility is not in question. The displacement fields suggested in this note satisfy complete compatibility.

A novel technique of dealing with differential eigenvalue problems has recently been introduced by Wadsworth and Wilde . The differential equation is expressed as a set of simultaneous first-order differential equations, the eigenvalue λ being regarded as an additional variable by adding the equation to the basic set. The differential eigenvalue problem is thus reduced to a set of non-linear first-order differential equations with two-point boundary conditions. This treatment of the problem, although novel, suffers from two serious disadvantages. First, it introduces non-linearity into an otherwise linear set of equations. Thus, the solution can no longer be obtained by linear combinations of independent particular solutions. One method of solving the non-linear systems is by assigning arbitrary starting values at one boundary and performing a step-by-step integration to the other boundary where in general the boundary conditions are not satisfied. The problem can be solved by adjustment of the initial assigned arbitrary values until the given conditions at the other boundary are satisfied. A second method and the one used by Wadsworth and Wilde is to estimate the unknown boundary values at both boundaries and integrate inwards to a meeting point. Changes can then be made to the unknown boundary values to make the two branches of the curve fit together.

In the theory of small vibrations the motion of a system can be characterised in terms of either geometrically compatible displacements or dynamically admis-sable impulses (1,2,3). However, the number of generalised displacements required to describe the motion of a system need not be the same as the number of generalised impulses required for the same purpose. The reason for this difference is that in either or both formulations certain zero frequency modes may be present. If the co-ordinates which describe such modes are eliminated then the number of displacement and impulse co-ordinates required to describe the oscillatory modes will be equal and one can then transform one formulation to the other by means of Legendre's transformation(4).

In their paper in the February 1967 Journal, Iyengar and Srinivasan have presented a solution to the problem of uniformly loaded clamped skew plates by employing characteristic functions for the modes of vibration of clamped-clamped beams. They compared their theoretical results with those obtained by Morley and Kennedy.

The writer has recently extended the 3-parameter solution by assuming a deflection function in the form:

The basic theory for the new TUBA family of plate elements has been presented in ref. 1, but lack of space did not allow the inclusion of all relevant developments. This refers, in particular, to the kinematically consistent load matrices, the so-called initial loads due to initial strains, and the geometrical stiffness for the analysis of buckling phenomena. In view of numerous requests by readers of the JOURNAL, we complete in this sequel the presentation with a brief account of the information omitted in ref. 1. At the same time we reproduce a small number of examples which show the great power of the new elements. To facilitate the reader's task the numbering of the current sections, equations and figures follow on consecutively from ref. 1.

The investigation of Daum focused attention on the problem of condensation in hypersonic wind tunnels. In such tunnels there is often a conflict between the desire to obtain the maximum Reynolds number and the necessity of operating with a sufficiently high stagnation temperature to avoid liquefaction of the working gas. The hypersonic gun tunnel, in which the present tests were made, is capable of running at relatively high Reynolds numbers and to define the operating limits of the RARDE gun tunnel, Bowman made measurements similar to those of Daum, but using nitrogen as the working gas. It will be recalled that Daum made measurements of static and pitot pressures at varying temperatures. He deduced from these measurements that below a certain working section pressure significant degrees of supersaturation could be tolerated before breakdown to the condensed state. Thus three regions can be defined; in order of increasing temperature these are:

(i) condensing flow;

(ii) supersaturated uncondensed flow; and

(iii)unsaturated flow (see Fig. 1).