EFFECTS OF APEX ANGLE VARIATION ON FLOW DEVELOPMENT IN JETS ISSUING FROM DIFFERENT ISOSCELES TRIANGULAR ORIFICES

Abstract

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.