Thank you. Yes, the displayed results are after initialization. Please note that in Figure 4, I have not shown the selected surfaces. In fact, for illustrations, I have selected all items in the surfaces list. nThe model is with double precision. I used boundary distance donor priority method but still the background mesh is not visible. nLet’s have a look to the orphan cells. There are 170292 overset orphan cells in the overset interface and that is the same with both donor priority methods.nFigure 5 (below) shows orphan cells by the command define/overset-interfaces/mark-cells then writing orphan then the command define/overset-interface/display-cells. The figure is the same with both donor priority methods. We see that a row of orphan cells is formed in the outer layer of the component mesh. Sounds interesting. nnFigure 5. A zoomed-in view showing orphan cells in red colour.nI guess the background mesh is actually removed by the solver and I think the reason is related to the fact that a physical boundary of the background is surrounded by a wall of the component mesh (see figure 3), which as a result, a physical boundary is forced to remove. If that is the case (?) I do not know based on which rule Fluent makes this decision.n