Computational assessment of non-axisymmetric separate-jet exhausts on test rig configurations

The next generation of civil turbofan engines are likely to have increased bypass ratios and lower fan pressure ratios to improve propulsive efficiency and to reduce specific fuel consumption. However, the larger size of these engines may result in increased overall aircraft drag partially that could offset the fuel consumption benefits. Non-axisymmetric exhaust configurations can contribute to the mitigation of these effects through an improved alignment of the thrust vector relative to the drag axis. However, there is a lack of knowledge on how to experimentally test non-axisymmetric exhaust designs. To address this, the study develops a non-axisymmetric configuration of the Dual Stream-Flow Reference Nozzle (DSFRN) and assesses it with computational fluid dynamics in various configurations and conditions. The objective is to establish a baseline approach for testing non-axisymmetric exhausts. Overall, it is recommended to test non-axisymmetric exhausts with the ambient wind-on effects included and to evaluate the three-dimensional exhaust characteristics using thrust vector angles, in addition to overall velocity and discharge coefficients. Moreover, the interaction between a swept wing and the non-axisymmetric exhaust was found not to have a notable impact on the exhaust characteristics.