The application of a heated thin metallic film to the measurement of mean skin friction in laminar and turbulent flow on a flat plate, circular cylinder and in an annular tunnel is described. The manner in which transition and separation are detected with this instrument is illustrated by reference to tests on a circular cylinder. The influence of the ambient air temperature and the gauge temperature on the behaviour of the instrument is analysed and it is shown that a reliable element can be constructed, capable of being moved from one location to another, while retaining its calibration. An element, calibrated on an oscillating flat plate, is used to obtain the spectral density of skin friction in a turbulent boundary layer.

The effect of the interaction of the wake from a nozzle guide vane with the rotor may be simulated in part by means of a stationary rotor and a moving wake system. This technique is applied to a transonic rotor blade cascade, and the unsteady measurements of surface pressure and heat transfer rate are compared with baseline data obtained without the wake interaction. The wake-rotor interaction results in a change in inlet incidence angle and this effect is also examined in the steady-state case. It is found that the shock waves from the moving wake system have a major effect on the instantaneous heat transfer rates.

The design and construction of a new experiment, to investigate the steady and unsteady heat transfer and aerodynamic behaviour of a rotating turbine in a transient facility, is described. The need for this experiment is discussed in the context of previous rotating bar wake and shock simulation work carried out in the Oxford transient cascade facility, and research elsewhere on the effects of rotating and three-dimensional flowfields on turbine aerodynamics and heat transfer. The outline concept and mode of operation of the turbine module are given before novel features of the design are presented in detail. Reference is made to a parallel paper also presented at this conference[18] which gives full details of the developments that have been necessary to allow the measurement of steady and unsteady heat transfer in this facility. Finally, the future work programme and possible plans for further facility improvements are given.

Heat transfer measurements have been made on a transonic turbine blade undergoing natural transition and with a simulation of the effect of NGV wake interactions. The use of wide bandwidth heat transfer instrumentation permits the tracking of individual unsteady events that were identified as being due to either the impinging wakes or to the turbulent spots occurring within the transition process. Trajectories of these events as seen by the blade surface instrumentation have been measured. Numerical models have been developed for the effects of both types of turbulent activity. The convection of the wake through the passage is predicted, allowing for estimations of the expected times for which the boundary layer is disturbed by the wake fluid. The new model for the random generation and subsequent growth and convection of the turbulent spots produces a time-resolved prediction of the intermittent heat transfer signals by use of a time-marching procedure. By superimposing the two numerical models it is possible to simulate the measured instantaneous heat transfer characteristics.