[ahmad95]

Originally Posted by Lance

Load the .trn file that is the last time step in the cardiac cycle. It will contain data that is time-averaged over one heart beat. But I guess you will need to run several cycles to get rid of initial value effects? Then delay the start of the averaging.

Hello.
How can I delay time to start?
All off my Runs done by TRANSIENT STATISTICS checked with out any thing about time off starting.
I have 8 cycle and I wanna to calculate OSI in last cycle and done all of runs with out any start time. Can I set an expression which do it:
WSS(8.24s)]-WSS(7.58)

[Lance]

Originally Posted by ahmad95

Hello.
How can I delay time to start?
All off my Runs done by TRANSIENT STATISTICS checked with out any thing about time off starting.
I have 8 cycle and I wanna to calculate OSI in last cycle and done all of runs with out any start time. Can I set an expression which do it:
WSS(8.24s)]-WSS(7.58)

You need to set the start/stop iteration for transient statistics in cfx-pre. It is right there in the trn stats tab. As far as I know there is no way to to time-averaging in post.

[yuqian]

Sorry, I can not appreciate the expression on your denominator of the equation. Can you explain it more?

Originally Posted by Alfamaniac

Exactly!When i'm changing the time step in CFD-Post the value of OSI is changing too. But now i can understand that it's happening because we are looking on a different .trn file as you mentioned above.How it would be possible to calculate OSI for one single heart beat?Should I do anything differently in CFX-Pre or should I define there any expressions?The expression that i'm using for the OSI (in CFD-Post) is

0.5*(1-((abs((Wall Shear X.Trnavg)+(Wall Shear Y.Trnavg)+(Wall Shear Z.Trnavg)))/((abs(Wall Shear X.Trnavg))+(abs(Wall Shear Y.Trnavg))+(abs( Wall Shear Z.Trnavg))))).

[RAN123]

I am trying to calculate the TAWSS over a particular surface . i have 1800 points all over the surface. so it is not possible manually to calaculate TAWSS ans OSI for each and individual points. is there any way by which i can find out the TAWSS & OSI for the entire surface and its graphical variation as obtained in other parameters like pressure velocity and others?

[carlos11194]

Originally Posted by Alfamaniac

Exactly!When i'm changing the time step in CFD-Post the value of OSI is changing too. But now i can understand that it's happening because we are looking on a different .trn file as you mentioned above.How it would be possible to calculate OSI for one single heart beat?Should I do anything differently in CFX-Pre or should I define there any expressions?The expression that i'm using for the OSI (in CFD-Post) is

0.5*(1-((abs((Wall Shear X.Trnavg)+(Wall Shear Y.Trnavg)+(Wall Shear Z.Trnavg)))/((abs(Wall Shear X.Trnavg))+(abs(Wall Shear Y.Trnavg))+(abs( Wall Shear Z.Trnavg))))).

Hello could you help me, how can I get the values ​​of Wall Shear X.Trnavg, etc.

[Lance]

Originally Posted by carlos11194

Hello could you help me, how can I get the values ​​of Wall Shear X.Trnavg, etc.

Transient averages can be defined in CFX-pre. See the manual?

[dewey]

Hi, I try this equation but with out success


0.5*(1-((abs((Wall Shear X.Trnavg)+(Wall Shear Y.Trnavg)+(Wall Shear Z.Trnavg)))/((abs(Wall Shear X.Trnavg))+(abs(Wall Shear Y.Trnavg))+(abs( Wall Shear Z.Trnavg))))).


0.5 * (1 - (((Wall Shear X.Trnavg) ^ 2 + (Wall Shear Y.Trnavg) ^ 2 + (Wall Shear Z.Trnavg)^ 2) ^ 0.5) / (((Wall Shear X) ^ 2 + (Wall Shear Y) ^ 2 + (Wall Shear Z) ^ 2) ^ 0.5))


some one could tell me wich is the OSI equation for CFX please?

[mep20108@tezu.ac.in]

while typing expression of OSI it shows errror as the following unrecognised name was referenced: trans_statistic.

Can anyone help me regarding this. I am using Ansys version 2022R1.

[Opaque]

who introduced the "trans_statistic( )" function? where did you get that expression from?

[mep20108@tezu.ac.in]

I get it from the link

Oscillatory Shear Index Calculation

[mep20108@tezu.ac.in]

I get it from the link

Oscillatory Shear Index Calculation

[mep20108@tezu.ac.in]

while typing expression in cfd post provided above shows errror as the following unrecognised name was referenced: trans_statistic.

Can anyone help me regarding this. I am using Ansys version 2022R1.

[Gert-Jan]

Above in this thread and in the link you provided it is explained. The term trans_statistic does not exist in Post. It is an reference to Transient average variables. This can be a simple number average, or rms values, or whatever you defined.

You first need to calculate these variables in a transient calculation. Therefore you should open CFX-Pre and define the type of Transient average variable ou want (in Output Control).
Then after the run, you can open the results in Post, and you obtain additional variables like WSS.Trnavg.
This is the Transient Average of WSS. Then in you expression you should replace the trans_statistic by WSS.Trnavg

It is all already explained above.

[mep20108@tezu.ac.in]

Thanks for detail explanation.
But I am using Fluent. So that method not works for me.Can you suggest how to do same in Fluent.

[Gert-Jan]

Ask your question in the Fluent-forum, not the CFX-forum.

Alternatively, start using CFX. I can highly recommend this piece of software, especially for transient calculations. For multiple reasons, too many to list them here.

[mep20108@tezu.ac.in]

Thanks Gert-Jan for your valuable suggestion.

[a4oft]

MARK AND LEARN thanks

[Yanlu]

Originally Posted by dewey

Hi, I try this equation but with out success


0.5*(1-((abs((Wall Shear X.Trnavg)+(Wall Shear Y.Trnavg)+(Wall Shear Z.Trnavg)))/((abs(Wall Shear X.Trnavg))+(abs(Wall Shear Y.Trnavg))+(abs( Wall Shear Z.Trnavg))))).


0.5 * (1 - (((Wall Shear X.Trnavg) ^ 2 + (Wall Shear Y.Trnavg) ^ 2 + (Wall Shear Z.Trnavg)^ 2) ^ 0.5) / (((Wall Shear X) ^ 2 + (Wall Shear Y) ^ 2 + (Wall Shear Z) ^ 2) ^ 0.5))


some one could tell me wich is the OSI equation for CFX please?

Hello, I encountered the same problem as you. I believe your formula is correct. However, the reason it cannot be successfully solved in CFX is that the denominator might be zero. Did you manage to solve this problem in the end?

[ghorrocks]

If the denominator is zero then put in an if() statement or use a min() function.

Note that with the if() statement both the negative and positive cases are evaluated, so if one evaluates to a divide by zero error but the if() statement should go to the other one it will still return an error.

For instance, C=if(abs(B)>0.01,A/B,A/0.01) will return an error if B=0; but this function will work with B=0:
Denominator = max(B,0.01)
C = A/Denominator

[Yanlu]

Originally Posted by ghorrocks

If the denominator is zero then put in an if() statement or use a min() function.

Note that with the if() statement both the negative and positive cases are evaluated, so if one evaluates to a divide by zero error but the if() statement should go to the other one it will still return an error.

For instance, C=if(abs(B)>0.01,A/B,A/0.01) will return an error if B=0; but this function will work with B=0:
Denominator = max(B,0.01)
C = A/Denominator

Your response was accurate and effectively resolved my issue. I greatly appreciate your assistance.