© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Due to its excellent insulation capability, usage of silica-phenolic charring ablator as nozzle liner is a common practice in solid rocket motor industry. During the design of a solid rocket motor employing silica-phenolic as nozzle liner, it is desired to conduct an accurate analysis yielding in-depth thermal response and recession characteristics. As the interior ballistics and nozzle recession rate mutually interact, best practice is to perform a coupled solution to both. Commonly used one-dimensional analysis tools with empirical approaches for estimation of convective heat transfer rate and blowing effect generally lack sought accuracy, and do not model the transient shape-change phenomena, which affects the nozzle performance. This work provides governing equations for charring, including pyrolysis gas injection and surface energy balance for melting ablation, along with a boundary condition governed by interior ballistics, and implements all these numerically into the commercial CFD solver FLUENT. Also, results from a static firing test conducted with a small scale ballistic evaluation motor employing a silica-phenolic nozzle insert are provided. Results from both investigations are compared and discussed. It is demonstrated that the implementation captures all the relevant physical phenomena.