Kalyan Goparaju
Ansys Employee

Hello Ullas,


The source surface should enclose the noise sources of your problem. In your case, I would start with creating an interior surface that surrounds the bubble. This might require you to change the mesh and create multiple fluid volumes. Please check guidelines in the link below. 


https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v201/en/flu_ug/flu_ug_sec_use_aeronoise_use.html?q=fwh


Thanks, 


Kalyan