I am by no means an experienced Fluent user but I have had residuals look similar to yours, so I'll try to explain what I learned so far.nFirst, looking for convergence by only residuals is not always the best practice. Try and also plot mass flow rate flux and/or other parameters you know are important for your case. If these plots remain flat it's also an indication that the simulation is converged. Residuals aren't the be all end all of finding convergence, it's just an easy way for the program to measure convergence.nOscillating residuals can hint at your case being of transient nature. You haven't specified if you are simulating steady-state or transient, however, it could be an indication. nK-omega SST is one of the harder viscous models to converge, especially continuity. It needs accurate ''first guess'' inputs to successfully converge in a timely manner. Try using the K-epsilon model to find those first guesses more accurately.nDo you have any test data available to check your simulation against? If so, check your simulation against that data to see if you're getting comparable results. If results are comparable, you've done a good job whether or not your residuals make you think otherwise.nK-omega SST also requires pretty dense meshing and a correct Y+ (first layer height) value.nn