# Acusolve - Exhaust Manifold Simulation

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Hello Forum,

I am a student and am learning how to use acusolve, I would like to know how to make a simulation of an exhaust manifold. I want to know what I have to define so I can have inlet conditions that change by time, do I only need to modify boundary conditions?

Thanks,

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You would need

Global

-  Auto Solution Strategy- Transient.

- Multiplier Function

Model-

- Inflow boundary condition with a multiplier function. This multiplier function defined above

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You would need

Global

-  Auto Solution Strategy- Transient.

- Multiplier Function

Model-

- Inflow boundary condition with a multiplier function. This multiplier function defined above

Do you have a tutorial on how to use the multiplier function?

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multiplier_function_AcuSolve_v3.pdf

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Now I get this error message as I run Acusolve, any tip?

acuSolve: ---------------------- Begin Time Step ----------------------

acuSolve: Time-Step=    1 ; timeInc= 1.000000e+010 ; time= 0.000000e+000

acuSolve: *** ASSERTION in Function <fElm3TwfVelSp>

acuSolve: *** no convergence

acuSolve: *** ASSERTION in Function <fElm3TwfVelSp>

acuSolve: *** no convergence

acuSolve: *** ASSERTION in Function <fElm3TwfVelSp>

acuSolve: *** no convergence

acuRun: *** ERROR: error occurred executing acuSolve"

acuRun: Tue Apr 21 09:03:15 2015

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Could you upload the .ACS file?

It seems you are using the same time step as for steady state. Time Inc = 100000000?

If you are running transient, also select a realistic time increment.

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what would be a more realistic time step? (I can not upload the file, the forum says I am not permitted to upload that kind of file)

Thanks,

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Time step 0.1 sec might be a good starting point.

Please upload .inp and .Log file. If necessary, rename the extension to .txt.

cfh likes this

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Time step 0.1 sec might be a good starting point.

Please upload .inp and .Log file. If necessary, rename the extension to .txt.

Here it is.

COMPARTIR.zip

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It does not helped the 0.1 seconds, I still have the same error

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The problem was the Time  was supposed to be Piecewise Linear.

With that one change it runs. Input file attached.

BTW, you would need to makes considerable changes to get useful results. Mesh is too coarse to get any accurate results. Also Nodal Output would be have to be changed to lesser value (e.g. 1 or 10), instead of current default 1000.

If you have not attended any training, I would recommend to visit an AcuSolve training at the nearest Altair location.

cureve_fit_time.inp.txt

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The problem was the Time  was supposed to be Piecewise Linear.

With that one change it runs. Input file attached.

BTW, you would need to makes considerable changes to get useful results. Mesh is too coarse to get any accurate results. Also Nodal Output would be have to be changed to lesser value (e.g. 1 or 10), instead of current default 1000.

If you have not attended any training, I would recommend to visit an AcuSolve training at the nearest Altair location.

Thanks,  the Time should be change only in the multiplier function or where else did you put Piecewise Linear

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# +----------------------------------------------------------------------+
# | Multiplier Function                                                  |
# +----------------------------------------------------------------------+

MULTIPLIER_FUNCTION( "time" ) {
type                                = piecewise_linear
curve_fit_values                    = { 0.0, 900.0;
5.0, 900.0;
7.5, 0.0;
10.0, 0.0;
12.5, 900.0; }
curve_fit_variable                  = time
evaluation                          = once_per_time_step
filter                              = none
}

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