nav.shirur
Subscriber

What is your set residual criteria? Also, how many iterations per time-step are you running? Are you converging every time-step?


Ans: Residual is absolute 1e-5 for X, Y Z, Continuity and Energy. Initially i started with only one time step and 5000 iterations to know where solution would converge. Solution reaches 1e-4 at approximately 2000 iterations and they goes straight. In this case i do not understand if i have to belive results or not. Could u please let me know how to monitor physical property by plotting against iteration and how to judge conservation (mass and energy?)


 


If you feel you are not getting the desired convergence you require, you might want to check your mesh quality. What is your min orthogonal quality and max skewness values?


From theory i understood acceptable results would be 1e-5 residuals,but is there a way to decide what should be residual value for a specific problem?Mesh quality is as follows,


Max Skewness: 0.797


Orthogonal Quality minimum: 0.2022


Max Aspect Ratio: 9.57


Cell size: 0.7mm


 


Please elaborate a little more on your model. Why are you using a pressure inlet boundary condition as opposed to mass flow rate inlet?


Since it is a problem of flow from high pressure container, i used pressure inlet and pressure outlet with compressible flow.  Moreover, i used transient phenomena so thought pressure is easy.


 


You might also want to think about slowly ramping up your pressure in small increments. Since you are solving a transient problem, you might want to be careful. But perhaps, you might want to start at a lower inlet pressure and let your simulation run to a steady state. Then without re-initializing, you might want to increase your pressure to a slightly higher value and again let the simulation run to a steady state. You continue this process until you get to the pressure condition you want to investigate. This method is extremely useful for steady state simulations, but when employed to transient, it would stretch your overall simulation time.


I don't know to how simulate using ramp concept and how to solve without reinitializing. Could u please throw somw light on this?