This lesson covers the process of determining primary unknowns at the cell centers using Ansys Fluent. It explains how Ansys Fluent® fluid simulation software solves for the velocity components and pressures at the cell centers and how other quantities can be calculated from these values. For instance, the lesson demonstrates how to calculate the drag and lift coefficients, which are derived from the pressure values in the solution. It also discusses the importance of specifying reference values, including density, area, and freestream velocity. The lesson further delves into the iterative process of solving the mathematical model, emphasizing the need to reduce the linearization error and set initial guess values for the primary unknowns in each cell.