Effect of upstream developing length on the flow field of twin pipe jets

It is well known that initial conditions significantly affect the flow field and the evolution characteristics of the jets. In the present study, experiments on twin pipe jets were performed to understand the effect of developing length on the twin-jet characteristics. The developing length was varied in the range of 4 < L/D < 9, and hot-wire data were acquired up to a downstream distance of 40D. Twin jets combine at farther downstream axial distance with an increase in the developing length due to delayed mixing brought about by relatively less intense vortex action. The range of the energy-containing eddies decreases, resulting in a decrease in the spread rates of the twin jet. © IMechE 2008.