[Turbofan]

Dear all,

I am quite new to using FloEFD and for that reason I would need some support. I am trying to characterize a small radial DC blower, in the sense of calculating the characteristic curve through a CFD software and comparing it with the one provided by the datasheet.

”Geometry.png

To do this my intention is to run an internal Simulation, setting an Environmental Pressure Inlet and a Volume Flow Rate Outlet as BC. However, until now I have not been able to find decent results, both because sometimes I underpredict results and because other times I get a reverse flow.

For all these reasons I would like to ask some questions and maybe have other suggestions to solve my problem:

1- Rotating Region

What is the correct form of the RR in this case? I know it must be an axis-symmetrical volume that must contain the impeller. As for the Blade to Blade plan you can see here how I created my RR, to which I gave a radius that is intermediate between that of the impeller and that of the narrowest point of the cochlea.

”Blade_to_Blade_Plane.png

It is correct?

As for the other dimension I have some doubts, because it is not clear to me if it should intersect the upper and lower shells or if the RR should follow the geometry of the impeller. Below is a cross section in the meridional plane of blower.

”Through_flow_Plane.png

2- Average or Sliding rotating region?

Since I would like to start with a steady state simulation it is not clear to me if, in this case, the Local rotating region (Averaging) approach is correct or if it is appropriate to launch a transient simulation and use the sliding approach. I did a bit of research online but the opinions are sometimes conflicting, so I want to clarify this point.

3- Mesh

From your experience, do you have any suggestions for me regarding the computational grid in this case? Should I also use the adaptive approach?

4- BC and measurements

In the simulations I conducted I used both an inlet duct (5x inlet diameter) and an outlet duct (10x outlet diameter) and, as I anticipated, I set an ambient pressure condition at the inlet and the volume flow rate at the outlet. This is because I would like to move on the pQ curve of the blower by varying the flow rate, calculating the pressure increase as the difference between the average static pressure calculated at the outlet and the ambient pressure. Is the approach I am using correct?

I apologize for the length of the thread but it is very important for me to clarify all concepts. If you have any other suggestions on aspects that I have not reported, you are welcome.

I thank in advance who will help me.

Turbofan

[Sai Krishna]

Originally Posted by Turbofan

Dear all,

I am quite new to using FloEFD and for that reason I would need some support. I am trying to characterize a small radial DC blower, in the sense of calculating the characteristic curve through a CFD software and comparing it with the one provided by the datasheet.

Attachment 89546

To do this my intention is to run an internal Simulation, setting an Environmental Pressure Inlet and a Volume Flow Rate Outlet as BC. However, until now I have not been able to find decent results, both because sometimes I underpredict results and because other times I get a reverse flow.

For all these reasons I would like to ask some questions and maybe have other suggestions to solve my problem:

1- Rotating Region

What is the correct form of the RR in this case? I know it must be an axis-symmetrical volume that must contain the impeller. As for the Blade to Blade plan you can see here how I created my RR, to which I gave a radius that is intermediate between that of the impeller and that of the narrowest point of the cochlea.

Attachment 89545

It is correct?

As for the other dimension I have some doubts, because it is not clear to me if it should intersect the upper and lower shells or if the RR should follow the geometry of the impeller. Below is a cross section in the meridional plane of blower.

Attachment 89547

2- Average or Sliding rotating region?

Since I would like to start with a steady state simulation it is not clear to me if, in this case, the Local rotating region (Averaging) approach is correct or if it is appropriate to launch a transient simulation and use the sliding approach. I did a bit of research online but the opinions are sometimes conflicting, so I want to clarify this point.

3- Mesh

From your experience, do you have any suggestions for me regarding the computational grid in this case? Should I also use the adaptive approach?

4- BC and measurements

In the simulations I conducted I used both an inlet duct (5x inlet diameter) and an outlet duct (10x outlet diameter) and, as I anticipated, I set an ambient pressure condition at the inlet and the volume flow rate at the outlet. This is because I would like to move on the pQ curve of the blower by varying the flow rate, calculating the pressure increase as the difference between the average static pressure calculated at the outlet and the ambient pressure. Is the approach I am using correct?

I apologize for the length of the thread but it is very important for me to clarify all concepts. If you have any other suggestions on aspects that I have not reported, you are welcome.

I thank in advance who will help me.

Turbofan

I know its old post, but I thought it might help others.
The rotating region can intersect others, provided if it revolves with the same speed as that of the rotating domain. If not we can give stator walls to the parts lying inside the domain other than moving parts. This what I understood from CPU tutorial of Floefd.