The article details a numerical investigation of methane pyrolysis inside a shock wave reformer using a quasi-2dimensional (Q2D) Reynolds-Averaged Navier–Stokes (RANS) CFD model. This work is in support of the New Wave Hydrogen, Inc. (NWH2) proprietary technology development. To take account of the characteristics of the flow in the presence of shock waves, a simplified approach is proposed that captures the gas dynamics during partial opening with a lower computational cost suitable for the wave reformer design. The model is based on the three-dimensional, compressible, and unsteady Navier-Stokes equation coupled with k −ω - SST turbulence closure. Boundary conditions are implemented through a cell-centered approach with fictitious cells outside of the domain boundaries. The numerical results are compared with solutions from a quasi-one-dimensional (Q1D) unsteady model reported in literature. The simulations show a good agreement between the two different modelling approaches in terms of spatial distribution of the pressure gradient for one complete cycle. It is observed from the Q2D results that the entrance for each passage, especially upon opening of the high-pressure driver gas port, is a location of particular interest in the formation of the shock. The resulting acute pressure gradients induce loss inside the channel, decreasing the maximum temperature during a complete wave cycle by 15%, and consequently, reducing the methane pyrolysis process.