Nicholas N. Gibbons, Tristan Vanyai, Vincent Wheatley
DOI Number XXX-YYY-ZZZ
Conference Number HiSST-2022-115
A numerical study of compressible turbulent transition behind a multiport injector array (MPIA) is conducted. The flow domain corresponds to an axisymmetric inlet recently tested at The University of
Queensland that used an MPIA to trip the boundary layer, by injecting a small amount of nitrogen close
to the wall. A single row of four 0.2mm porthole injectors is simulated using Wall-Modelled Large Eddy
Simulation (LES), at an experimental condition corresponding to Mach 7.6 flight at a dynamic pressure
of 50kPa. The LES simulations reveal that the MPIA injection results in immediate large scale instabilities reminiscent of near-wall turbulence. The main feature of interest is a family of dominant frequencies
superimposed on the turbulent wavestructure, with a base wavelength of ≈ 5mm. The source of this
regularity appears to be periodic oscillation of the final fuel jet, which in turn is dynamically coupled to the
upstream jets in an complex and interesting manner which has not been described before. The turbulent
flow behind the MPIA results in an increase in wall heat transfer that counteracts any film cooling that
may be present from the injectors. The LES prediction of the heat transfer rates compare favourably to
experimental measurements, and RANS simulations using the Spalart-Allmaras and Menter SST models are found to underpredict wall heat transfer throughout the domain.