Gasification in supercritical water is a very promising technology to process wet biomass into a valuable gas. Providing insight of the process behavior is therefore very important. In this research a computational fluid dynamic model is developed to investigate glycerol gasification in supercritical water, which takes place in a cylindrical reactor with a tee junction. The performance of the developed model is validated against experiment, and it shows that the model is able to describe the process very well. The experimental validation shows that the model slightly overestimates the outlet temperature on average by 6% and underestimates the carbon gasification efficiency on average by 16%. The flow behavior in the supercritical water gasification process is successfully described and a sensitivity analysis is conducted. It is revealed that the flow pattern of the process is heavily influenced by gravitational forces which significantly influences mixing and heat transfer.