A Jet Exhaust Model for Soot Dispersion and Visibility

This study describes the development of a numerical model to investigate soot dispersion and visibility in the exhaust of a jet aircraft. Equations for momentum, thermal energy, and mass transport are described and numerically solved for compressible, turbulent flow in an axi-symmetric jet. In addition, mass transport equations for particulate soot are developed by applying the conventional method of moments and using the six lowest generalized moments. An algorithm for moment inversion, providing a particulate spectral distribution, is described and applied to the generalized moments. Furthermore, we show that the extinction and transmission coefficients for Mie scattering can be written as integral properties of the particulate spectra. Finally, we apply the numerical model to the configuration of a common transport aircraft. We present results for five test cases of particulate soot loading at the exit plane, by showing the downstream effects of soot dispersion on exhaust visibility. Briefly, we describe ongoing efforts to couple vapor and particle transport equations in order to model the effects of condensation growth on plume visibility