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SummaryExperiments have been made to find the effect of the ratio of sting to base diameter on the base pressure of an axially symmetric body at zero incidence in a supersonic stream. The Mach number of the flow was 1·994 and the model boundary layer was turbulent. The model used was a one inch diameter circular cylinder without boat-tailing. It passed through and was supported upstream of the nozzle throat. This method of support allowed measurements to be made in the important (and hitherto unexplored) case of zero sting diameter.As the sting to base diameter ratio was increased from 0 to 0·85, the base pressure decreased. The minimum value reached was approximately 0·8 of the value it would have at the base of a two-dimensional body with a similar ratio of boundary layer thickness to base height. The base pressure coefficient rose rapidly to zero as the ratio was further increased to unity.Under the conditions of the experiments, with a sting to base diameter ratio of 0·4 the base pressure coefficient differed from that without a sting by approximately ten per cent. With the more modest ratio of 0·2, the difference was approximately three per cent.

SummaryThe paper discusses convection in a vertical tube closed at both ends in which the temperature of the walls is arranged to increase linearly with depth. For the purposes of the theory, the convective flow is assumed to be radially symmetrical about the axis of the tube.The temperature and velocity distributions in the pipe are found to be dependent on a non-dimensional modified Rayleigh number H. Experiments conducted at values of H between 90 and 30 000 agree with theoretical predictions for values of H below 300 and above 3000. Negative temperature gradients occurring along the axis for values of H between 700 and 950 indicate that in this range the flow cannot be radially symmetric. This non-symmetric flow would develop first, as H is increased from zero, and it is suggested that the agreement between the experimental and theoretical results for H <300 shows that the critical value of H for the non-symmetrical flow does not differ greatly from the value (142) obtained theoretically for the symmetric regime. Presumably it is at values of H of 3000 and above that the flow takes an axially symmetric form. This higher range is appropriate to bores in the New Zealand thermal regions.

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