Experimental and numerical investigations of ultimate upstream penetration of developed counter flow jet formed as result of impingement of multiple round jets radially injected into a high-temperature confined crossflow have been performed. These investigations aimed to reveal an influence of strength of the developed counter flow jet on mixing intensity of jets in crossflow of cylindrical duct. Based on analysis of experimental data, the analytical dependence between dimensionless parameter of upstream penetration depth of counter flow jet and the square root of jets-to-mainstream momentum-flux ratio J has been established. The dependence proved to consist of linear region as well as nonlinear and asymptotic ones. For a given geometry an ultimate upstream penetration depth of the counter flow jet has been estimated to be approximately 2.1-2.3 diameter of the cylindrical duct. The corresponding value obtained on the base of numerical simulation turned out to be 1.8-2.0 diameter of the cylindrical duct. The dimensionless parameter h/D of radial jet penetration depth proved to be an appropriate to describe adequately an empirical character of upstream penetration of the counter flow jet within the linear region. Based on results of numerical simulation, axial velocity, temperature and pressure profiles as well as centerline turbulent kinetic energy contours have been obtained. It has been has also shown that an increase of the momentum-flux ratio promotes mixing in upstream recirculation flow zone and improves overall mixing performance as well. (C) 2017 Elsevier Ltd. All rights reserved.