A second order analysis has been made of the aerodynamic growth of sinuous waves on parallel sided inviscid liquid sheets and equations have been derived which describe the characteristics of the fundamental mode and the first harmonic. A solution has been obtained for the case where the wavelengths are relatively long compared with the sheet thickness and it is found that thinning of the sheet is caused by the growth of the harmonic wave, maximum thinning and subsequent rupture occurring at positions corresponding to 3/8 and 7/8 of the length of the fundamental wave. The solutions have been utilized to calculate the break-up lengths of attenuating sheets and the results are compared with measured values.

A new aerodynamic open-circuit test rig for studying boundary layer ingestion (BLI) propulsion has been developed by National Research Council of Canada. The purpose is to demonstrate the advantages of BLI in reducing the power required for a given thrust and to validate the performance of BLI fan concepts. The rig consists of a boundary layer generator to simulate boundary layer development over an aircraft fuselage. The boundary layer generator can be used to create a natural boundary layer due to skin friction but also comprises an array of perforated plates through which pressurised air can be blown to manipulate the boundary layer thickness. The size of the boundary layer thickness can be controlled upstream of the fan blades. Parametric studies of boundary layer thickness were then feasible. The test calibration was conducted to validate the concept.

A study has been made of the flow and disintegration of thin liquid sheets in combustion gases up to temperatures of 950°C. It is found that below 300°C sheet breakdown occurs through the growth of antisymmetric Kelvin–Helmholtz waves. Above this temperature high frequency symmetric waves and localized disturbances are superimposed on the sheet and disintegration then occurs by the combined action of aerodynamic waves and perforations, the contribution of the latter predominating with increasing temperature. It is demonstrated that the new wave system is electrohydrodynamic in origin, the electric field being generated by the charged species present in the gas. The drop size is found to be critically dependent upon the nature of the disintegration process.

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