Zero Inlet Condition

Rajkamal B

Hi,

I am a Acusolve user and I cannot simulate flow starting from 0 lpm to 10 lpm.

Is it possible to get the Nodal Initial Condition for this kind of simulation.

For Example: Let lets consider a nozzle. If i want to simulate a flow with increasing flow rate of 5lpm to 10 lpm. i need to generate a steady state flow with 5lp as inlet velocity and get the NIC file and feed it to the transient model as instructed in ACU-t:3101 Transient Conjugate Heat Transfer is a Mixing Elbow tutorial.

What i should do if i need to simulate for 0lpm to 10lpm flow rate. 

Thank you in advance,

Regards,

Rajkamal

Jagan Adithya Elango

Go to boundaries > profiled > volumetric flow.
Click the drop down adjacent to volumetric Flow rate and select create new.

In the specify the type as Piecewise Linear. There you can feed the time vs flow rate values. And also make sure you are consistent with the units. If you are following MKS you should specify volumetric flow rate in terms of m^3/s.

Rajkamal B

Hi Jagan,

Thanks for the reply. This helps a lot. 

But before this we need steady state results. In that model if i give inlet condition as 0lpm the results the pressure values are coming in negative. Even the value is around -101506 Pa

Thanks in advance.

Jagan Adithya Elango

Rajkamal B said:

Hi Jagan,

Thanks for the reply. This helps a lot. 

But before this we need steady state results. In that model if i give inlet condition as 0lpm the results the pressure values are coming in negative. Even the value is around -101506 Pa

Thanks in advance.

I don't understand why you are trying to solve for 0 lpm.  And what is your outlet boundary condition?

Rajkamal B

Jagan_21383 said:

I don't understand why you are trying to solve for 0 lpm.  And what is your outlet boundary condition?

if we are trying to create a transient solution we need to Nodal Initial condition for that right?

That's Why i am trying to solve for 0lpm.

And my Output Boundary condition is set to atmospheric pressure

Bill Calver_22424

Hi Rajkamal,

Running a steady state simulation prior to a transient simulation is not always necessary.

In general, a steady state solution might be computed first:

1. if largely different time scales are involved, or,
2. in order to bypass any "start-up" effects that a pure transient run might need to overcome in order to get to a point of being able to produce statistically relevant data. 

The second scenario is often used when calculating transient drag with external aerodynamics, for example.

In ACU-T: 3101, the first scenario applies because the small time scales of a transient flow field are not as important as the larger time scales of the transient thermal field.

For your case of ramping the inlet flow from 0 lps to 10 lps you can just initialize your model to zero flow and run with a multiplier on the inlet flow as Jagan wrote above.

Rajkamal B

Hi,

Thanks for the reply this gives a better understanding.

Thank  you all for the answers.

Rajkamal B

Hi,

Can anyone explain me why at the starting of the run pressure decreases

Rajkamal B

Also How to plot Velocity vs Pressure Curve. In AcuProbe we can plot velocity vs timestep and Pressure vs timestep but we cannot cross plot it. 

Also How to filter those curve in AcuProbe or by anyother means.

acupro

Rajkamal B said:

Also How to plot Velocity vs Pressure Curve. In AcuProbe we can plot velocity vs timestep and Pressure vs timestep but we cannot cross plot it. 

Also How to filter those curve in AcuProbe or by anyother means.

You'll likely need to bring the data you want to cross-plot, filter, etc into a different plotting tool for those other functions.