# Divergence in calculation: water-emulsion-injection

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 October 8, 2018, 11:30 Divergence in calculation: water-emulsion-injection #1 New Member   Dennis Niemann Join Date: Oct 2018 Location: Germany Posts: 4 Rep Power: 7 Hello, I am simulating a water-emulsion-injection in an 4 stroke gas engine. The Mesh was build with Fame Engine Plus. srokes: - 315°-526°: exhaust valves open - 526-534°: valve overlapping - 534°-772: intake valves open - 772°-1035: all valves open The problem is, that my calculation diverges around 360°CA (exhaust valves not full open). The false report are such as: - Problem diverges: TKE equation, variable: TKE, material: 1 or - Problem diverges: continuity equation, variable: Pressure correction, material: 1 The following modules are activatated: Species Transport, Combustion, Spray, Wallfilm, Thin Walls. When the modules Spray, Wallfilm and Thin Walls are deactivated, the problem are the same. So I think the problem is an incorrect setting in the solver control. I have decreased the underrelaxation factors (pressure: 0.1, Momentum: 0.6, TKE: 0.3, Turb. diss. rate: 0.3. I also have tried to change the linear solver of continuity (GSTB/AMG and variated th max iterations), but the problem was still the same. Here are other settings, which I used: - Convergence Criteria Pressure: 0.01 - Boundary Condition Inlet: total pressure 1.5bar - BC outlet: static pressure 1.07bar It is possible, that the problem for the divergence is the mesh itself? I use high refinements in valve seats and valve heads. I am thankful for every recommendation. Best regards

 October 9, 2018, 03:30 #2 New Member   Stephan Werner Join Date: Sep 2018 Posts: 6 Rep Power: 7 Hello, did You do a dummy run after meshing with FE+? What were the results? Also a refinement of cells might be necessary, when the valves are almost closed.

 October 9, 2018, 05:24 #3 New Member   Dennis Niemann Join Date: Oct 2018 Location: Germany Posts: 4 Rep Power: 7 The result of the dummy run were 2 twisted faces. 5°CA after the valves opened and before the valves will close I have used a refinement level 3 at valve heads and the valve seats. My settings of the refinements are a recommendation of an example case in AVL Fire (case 920)