The strong-jet/weak-jet coupling is basic to a new generation of ultra-low-NOx burners that are diffusion type and rely on lower flame temperatures through controlled mixing of the air, the fuel, and recirculated combustion products. Further, to developing a theory on the isolated jet pair in a previous publication, where the jet trajectories were predicted and compared with experimental data with good agreement, new experimental results of cold modeling by using flow visualization and laser Doppler velocimetry (LDV) are reported in this paper. Mathematical modeling by using a commercial computational fluid dynamics code (CFD) was employed to predict the how field. CFD is also used to predict a mixing progress variable, R-12 for the three stream mixing of air, fuel, and combustion products for the first time. Flow visualization reveals very interesting behavior of large scale structures and engulfment as the fuel and combustion air interact and mix. The measured mean and root-mean-squared velocities on the plane of bilateral symmetry are compared with the CFD predictions. The profiles across the jet cross-sections and the behavior along the air jet axis closely follow the experimental results. however, the fuel jet trajectory is poorly predicted. Constraints in the model due to the assumption of normal or well-developed turbulence spectrum in concentration fluctuations are highlighted. (C) 2001 by The Combustion Institute.