The chemical oxygen–iodine laser(COIL)is the shortest-wavelength high-power chemical laser that has been demonstrated.The characteristics,such as good atmospheric propagation,short wavelength and excellent transmission through optical fibers,make the COIL a good candidate for high-power laser application.To model the complete COIL lasing interaction,a three-dimensional formulation of the fluid dynamics,species continuity and radiation transport equations is necessary.The computational effort to calculate the flow field over the entire nozzle bank with a grid fine enough to resolve the injection holes is so large as to preclude doing the calculation.The approach to modeling chemical lasers then has been to reduce the complexity of the model to correspond to the available computational capability,adding details as computing power increased.The modeling of lasing in the COIL medium is proposed,which is coupling with the effects induced by transverse injection of secondary gases,non-equilibrium chemical reactions,nozzle tail flow and boundary layer.The coupled steady solutions of the fluid dynamics and optics in a COIL complex three-dimensional cavity flow field are obtained following the proposal.The modeling results show that these effects have some influence on the lasing properties.A feasible methodology and a theoretical tool are offered to predict the beam quality for large-scale COIL devices. The chemical oxygen-iodine laser (COIL) is the shortest-wavelength high-power chemical laser that has been demonstrated. These characteristics, such as good atmospheric propagation, short wavelength and excellent transmission through optical fibers, make the COIL a good candidate for high -power laser application. To model the complete COIL lasing interaction, a three-dimensional formulation of the fluid dynamics, species continuity and radiation transport equations is necessary. computational effort to calculate the flow field over the entire nozzle bank with a grid fine enough to resolve the injection holes is so large as to preclude doing the calculation. approach to modeling chemical lasers then has been to reduce the complexity of the model to correspond to the available computational capability, adding details as computing power increased. The modeling of lasing in the COIL medium is proposed, which is coupled with the effects induced by transverse injection of secondary gases, non-equi librium chemical reactions, nozzle tail flow and boundary layer. the steady steady solutions of the fluid dynamics and optics in a COIL complex three-dimensional cavity flow field are obtained the the following. the modeling results show that these effects have some influence on the lasing properties.A feasible methodology and a theoretical tool are offered to predict the beam quality for large-scale COIL devices.