Thank Rob.nI can't extend the domain, because the object is the flue pipe of the coal-fired power plant, which has been completed.nHow can I could to know why it's happening and then work out it ?nIf I move my injections' location near the inlet, whether the warning will be disappear ?(Best don't move the injections' location, because my aim is the know the distribution of particles after injecting at that location.)nMaybe I could used the other model, like DEM ? or just continue calculating?.