Fluent Scaled Residuals: Explained

The Basics: When using FLUENT to simulate fluid flow and heat transfer, it is important to understand the concept of scaled residuals. Scaled residuals are essentially a way to measure convergence of the solution within FLUENT. These residuals compare the difference between the values computed by the solver at the current iteration to the values calculated in previous iterations. The residuals are scaled by the mesh cell size, so that they are all on a comparable scale regardless of the mesh size.

The Importance: Now that we understand what scaled residuals are, it is important to understand why they are significant. Essentially, the scaled residuals are indicators of the accuracy of the solution. They provide a way to monitor the progression of a solution, and indicate when it has converged (i.e. when the residual values have reached a certain threshold). Without using scaled residuals, it can be difficult to determine whether or not a simulation has sufficiently converged.

The Curves: FLUENT provides a set of curves that represent the scaled residuals of various variables, such as velocity or temperature. These curves, when properly analyzed, can provide insight into the progression of the simulation. Typically, as the simulation progresses, the residual values initially decrease rapidly as the solver tries to converge to a solution. However, eventually the rate of decrease slows, and the values may begin to fluctuate or even increase. This can indicate that the simulation has not fully converged, and may require additional iterations or adjustments to the simulation parameters.

Overall, understanding scaled residuals is a crucial component to using FLUENT effectively. By monitoring the scaled residuals and analyzing their curves, you can gain insight into the accuracy and progression of your simulation.