[aiden_1995]

Hi friends
i'm doing a simulation of blood flow with fsi modelling
i want to do the simulation in 5 cycles.
the question is: how should i enter the number of time step to have several cycles? and where?
i thought for 1 seconds of simulation and time step of 0.01 i should enter the number of time step 500(5 cycles) and time step in fluent and end time and time step in coupling and the same in transient structural but at the end the solution goes for 1 cycle only and all the numbers were changed in fluent section.

can anybody point the problem and the way of solving? it would be so appreciated.

here is a picture of 3th cycle to help you realize what I'm saying better :

[AlexanderZ]

for 1 seconds of simulation and time step of 0.01 i should enter the number of time step 500(5 cycles)

that is correct, you probably have problems with boundary conditions

[aiden_1995]

Originally Posted by AlexanderZ

that is correct, you probably have problems with boundary conditions

thanks for your replay alexander,but i ustill don't realize
I'm using udfs for inlet and outlet velocity and pressure
how come? how does it affect the time step?
i don't want the fluent section to change,how can i fix this?
now i also tried to do it in another way but it's still changing

[AlexanderZ]

solution goes for 1 cycle only and all the numbers were changed in fluent section.

so most likely, problem is in your UDF, where you didn't repeat profile correctly
show your UDF
when you are saying "all the numbers were changed" it's not clear what exactly you are talking about. The Graph you showed is not readable ( at least show first cycle (which is correct according to what you've said) and second (which is incorrect))
as you are using FSI - the shape of geometry suppose to change which should lead to change in flow,s o may be change you are talking about is normal. check it

[aiden_1995]

Originally Posted by AlexanderZ

so most likely, problem is in your UDF, where you didn't repeat profile correctly
show your UDF
when you are saying "all the numbers were changed" it's not clear what exactly you are talking about. The Graph you showed is not readable ( at least show first cycle (which is correct according to what you've said) and second (which is incorrect))
as you are using FSI - the shape of geometry suppose to change which should lead to change in flow,s o may be change you are talking about is normal. check it

ok

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i know that it makes only 1 graph per 1 solution running
the reason why I'm using more cycles is for the sake of "convergence"
i think they should repeat 5 times during the solution not be ready at first in the udf.am i right?

[aiden_1995]

Originally Posted by AlexanderZ

so most likely, problem is in your UDF, where you didn't repeat profile correctly
show your UDF
when you are saying "all the numbers were changed" it's not clear what exactly you are talking about. The Graph you showed is not readable ( at least show first cycle (which is correct according to what you've said) and second (which is incorrect))
as you are using FSI - the shape of geometry suppose to change which should lead to change in flow,s o may be change you are talking about is normal. check it

_________________________________
about the time step you were right-let me make it more clear by explaining on a picture:

this is my Fluent's time step setup after ending the solution:
"the number of time steps which i entered and was 500(100*5cycles)has changed to 1 and the time step which was 0.01 turned to 0.0099999..."
----------------------------------------------------------------------


----------------------------------------------------------------------

and i filled the rest of it for coupling and transient structural like what i mentioned before

[AlexanderZ]

as your simulation is transient it doesn't make sense to simulate several cycles to get converged simulation
increase number of iterations per time step, if you are not sure
check mass balance convergence (difference between in\out mass flow rates) for each iteration -> in perfect case it should converge for each timestep

however, if you want to simulate several cycles
add t = t%1; into your code for both profiles

real t = CURRENT_TIME;
t = t%1;
begin_f_loop(f, thread)