Learning Forum

[Saad Sultan]

Hello Everyone,

I do a lot of modal analysis of an impeller. 

I use the following commands

ANTYPE,MODAL

MXPAND,nmodes (nmodes=500)

PSTRES,ON

MODOPT,LANB,nmodes,0,2000

Using the above commands the maximum load step the solver goes is 9. Is there any particular reason it is fixed till 9 even if I changes nmodes=250 only the substeps changes and not the load steps. The same I see in ANSYS Workbench. I can changes the number of modes but the loadsteps still is limited to maximum 9. Can someone tell me where or what can is needed to change this maximum lpadstep value ?

thanks in advance.

 

 

 

 

[Saad Sultan]

Hello Everyone, 

After going through some ANSYS documentations, my question was irrelevant as I had not provided any details.

According to my understanding in ANSYS cyclic periodic modal analysis, the Loadsteps are actually Harmonic Index which are nothing but Nodal Diameters.

Secondly my impeller had 16 blades so the maximum number of Nodal Diameters shall be no more than 8. Moreover ANSYS APDL sorts the loadstep counting starting from 1 rather than from zero which is the case in ANSYS Workbench. 

Please do correct me if I misunderstood or the information is missing. I thought it would be better to share the info rather than just closing the post.

[dlooman]

Yes, you answered your own question!  For a 1/16th sector there are 9 harmonic indices, 0 to 8.  Each of these are solved separately producing the 9 load steps you see.  We don't have a load step 0, so as you say, they are numbered 1 to 9.