Hi Venkata,

Boundary conditions (BCs) have a strong influence on natural frequencies of a structure. Once the BCs are applied, we use modal analysis to determine natural frequencies of the model. Next, we employ harmonic response analysis (once again, after the BCs are imposed and modal anaysis performed) to investigate the response of the model under a harmonic load.

I recommend you check the courses below where you can find several examples:

Modal Analysis in Ansys Mechanical | Ansys Courses

Harmonic Response Analysis in Ansys Mechanical - ANSYS Innovation Courses