The linear stability of the spiral motion induced between concentric cylinders by an axial pressure gradient and independent cylinder rotation is studied numerically and experimentally for a wide-gap geometry. A three-dimensional disturbance is considered. Linear stability limits in the form of Taylor numbers TaL are computed for the rotation ratios μ, = 0, 0·2, and -0·5 and for values of the axial Reynolds number Re up to 100. Depending on the values of μ and Re, the disturbance which corresponds to TaL can have a toroidal vortex structure or a spiral form. Aluminium-flake flow visualization is used to determine conditions for the onset of a secondary motion and its structure at finite amplitude. The experimental results agree with the predicted values of TaL for μ [ges ] 0, and low Reynolds number. For other cases in which agreement is only fair, apparatus length is shown to be a contributing influence. The comparison between experimental and predicted wave forms shows good agreement in overall trends.

Heat transfer characteristics were measured for two-dimensional arrays of jets impinging on a surface parallel to the jet orifice plate. The impinging flow was constrained to exit in a single direction along the channel formed by the jet plate and the heat transfer surface. Both mean Nusselt numbers and streamwise Nusselt number profiles are presented as a function of Reynolds number and geometric parameters. The results show that significant periodic variations occur in the streamwise Nusselt number profiles, persisting downstream for at least ten rows of jet holes. Both channel height and hole spacing can have a significant effect on the streamwise profiles, smoothed across the periodic variations. Where significant differences exist, inline hole patterns provide better heat transfer than staggered ones, particularly downstream. These and other effects of the geometric parameters are presented and discussed.

The paper presents experimental results for performance of full-coverage film cooled surfaces. Effectiveness and heat transfer are measured on plane surfaces with discrete injection through the surface at an array of points into a turbulent mainstream boundary layer. The injection is normal to the surface, through circular holes arranged in both in-line and staggered patterns with 4.8 hole diameters used for both the row-to-row spacing and the hole-to-hole spacing within a single row. Both the film and mainstream fluids are air, and property differences are kept small throughout the study. Uniform injection over the entire array at film-to-mainstream velocity ratios of 0.1 and 0.2 with a uniform wall temperature boundary condition are covered. Results are compared with predictions using superposition of available single hole local effectiveness values.

Results are presented from experimental measurements of heat-transfer rates on surfaces which are cooled by injection through one to four rows of evenly spaced, flush, normal injection holes arranged in staggered and in-line patterns with hole spacings of 4.8 dia. Film cooling performanc is evaluated in both the injection and downstream recovery regions from transient tests which provide a uniform wall temperature boundary condition. Both the film and mainstream fluids are air, and film-to-mainstream mass velocity ratios of 0.1, 0.2, 0.3, and 0.5 are covered.

The energy stability limit is calculated for flow in a curved channel due to a pressure gradient acting around the channel. The energy limit is found among transverse disturbances and is of the same order for all channel radius ratios. The difference between the previously available linear limit and the energy limit increases dramatically as the instability mechanism changes, with radius ratio, from centrifugal force to viscosity in the limiting plane Poiseuille flow case.