Hi Yushu,
What is the frequency of operation?
You may assign mesh operations to get a denser mesh in the areas might not a good mesh. Select the object, right click and go Assign mesh operations.. You may read about mesh opeartions and what they do in online help.
Also, It is likely that classic mesh would be better for this case. Right click on the Mesh in the Project manager, go to Initial Mesh. In the General Tab on the top, Select the Mesh Method to Classic.
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