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Isothermal, incompressible jets of air issuing from sharp-edged isosceles triangular orifices with apex angles of 10°, 20°, 30°, 70° and 160° into still surrounding air, were used to study the effects of apex angle variation on flow development in the jets. Some measurements were made in two round jets issuing from a sharp-edged orifice and from a contoured nozzle. The mean streamwise centreline velocity decay, mass entrainment and spreading results show that the 160° jet, which originates from the orifice with the longest perimeter, has the highest mixing rate in the near flow field. The results also suggest that the 10° jet, which originates from the orifice with the second longest perimeter, has the highest mixing rate in the far field. The results demonstrate that all the triangular jets have higher mixing rates than the round jets, throughout the flow region investigated.

Prior research in the field of boundary layer turbulence has identified streamwise-elongated large-scale turbulence structures in both low speed compressible and high speed (M=2.0) flow. No experimental work has been done in any flow of M> or =3 in an attempt to identify the presence or quantify the behavior of these structures, nor has any study of favorable pressure gradient or surface roughness element effects on these structures been conducted. This research used high-resolution Particle Imaging Velocimetry in a M = 4.9 blow-down wind tunnel accompanied by a series of data analysis in order to identify the existence of streamwise-elongated large-scale turbulence structures in a hypersonic boundary layer. Furthermore, this study identified physical and statistical behavior which suggests that increasing favorable pressure gradient had a substantial impact on both the structural coherence and relative intensity of these turbulent structures at all boundary layer heights tested. This experiment also identified similar effects on these structures in the lower half of the boundary layer as a result of the introduction of surface roughness elements. Finally, several trends were identified between the averaged turbulence statistics and the behavior of the large-scale streamwise-elongated turbulence structures present in this study.

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