Can someone help me understand this residual plot?
 

Hi everyone,
after working on my model for few days I finally got the implicit unsteady solver to work and it looks it's converging to me. However, the SDR does not look right to me because there are alot of random oscillation. Also, the energy is converging very slow and I'm not sure if it's normal or not. Can someone enlight me what I should do to get rid of the oscillation on the SDR curve? I appreciate for any help.https://imgur.com/dtkOw7G