Unsteady pressure mapping in forced response of a turbomachinery

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  • Last Post 19 April 2019
Tayyip posted this 15 November 2018

Hi,

I am currently studying on mode superposition harmonic analysis of a fan blade. An early discussion I mentioned that I am applying unsteady pressure mapping (by APDL commands) on fan blade which comes from CFX transient analysis by .csv file. 

Although I apply mapping on blades, there is no change in total deformation or max. equivalent stress comparing to regular pre-structural results. 

Do I apply something wrong or the values are so small that doesn't even effect decimal digits of results?

Thanks,

Tayyip

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ricardooliv22 posted this 04 April 2019

Dear Tayyip,

I am currently doing a similar analysis and I have been struggling to do the pressure mapping using APDL commands.

Could you provide me some information regarding this?

My main issue right now is related to the type of elements used I believe:

 

The error is:

"The target surface does not have SURF154 elements on its surface for   
 applying the mapped pressure loads.  Please leave /MAP (FINISH), add   
 them (ESURF command, in PREP7), and try again.  "

 

Best regards,

Ricardo Oliveira                   

jpasquerell posted this 05 April 2019

To me the message is indicating that in order to do the pressure mapping there must be SURF154 elements on the surface.  I suspect that the TARGET command causes the error and in the notes for the TARGET command it states"The surface must be meshed (ESURF command) with SURF154 elements prior to issuing this command."  If not, indicate what command led to the error.  Use the ET command to create the element type and before the ESURF.

Tayyip posted this 19 April 2019

Hi Ricardo,

Sorry for the late reply. I couldnt handle the problem with the tutorial. A bunch of APDL commands which I dont know exhausted me . So, I figured it out by using external data module. I advice you to do the same.

First you should define harmonic forces response output data into CFX usteady frozen rotor analysis. After the analysis you will take the excel data which includes coordinates of each nodes and their corresponding real and imaginary pressure values.

Then, you should reorganize the columns such as x,y,z,pressure real,pressure imaginary. After you should upload it to external data. Then link it to the Ansys Mechanical Harmonic Response Analysis (full harmonic analysis).

I also tried mode-superposition but it didnt work with the external data module. So, I didnt take into account the pre-stress effects . Because I thought they have minor effect on my problem. 

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