There are a couple things you can try for a quick fix.
- Set the Initialization Type = LinearInitializationMethod. This will calculate the first iteration of flows and pressures assuming a linear relationship. All subsequent iterations will be nonlinear. A better initial guess will improve you're chances of convergence.
- Adjust the Convergence Acceleration Limit field. The solver uses a "Steffenson like" algorithm to reduce oscillations when steps in pressure are too large. One of the downfalls of Newtonian solvers is that they can fall outside of their radius of convergence when step sizes are large, so the E+ solver uses a kind of damper on the Newton step in an attempt to prevent this. However, it only applies the damper when the ratio of pressure corrections for the current iteration to the previous iteration is less than a critical value. This critical value is the Convergence Acceleration Limit. This field also controls the amount of damping in the Newton direction. A value between -1 and 0 will reduce the step size , and a value between 0 and 1 will increase the step size. Since you are trying to improve convergence, a value of Convergence Acceleration Limit = 0 will be the most conservative choice. You'll also see an increase in computation time. To my knowledge, no one has actually proven that this method improves the chances for convergence, so this may not work for you, but it's worth a shot.
