[aja1345]

Hi dear friends,

I am simulating a turbine. And here, I have some question:

Turbine is as follow:

Due to the circumferential symmetry, only one sixth of the annulus has been computed, imposing periodic boundary conditions in the tangential direction. According to the following figure, the computational domain has been restricted in the axial direction to six chord lengths upstream and ten chord lengths downstream of the blade in order to provide fully unrestricted flow around the aerofoil section.

Inlet boundary is inlet velocity and outlet boundary is outlet pressure. I have used K-e model.

My first question is about turbulence of boundary condition that I don’t know that what do I select? K and Epsilon? Intensity and Length Scale? Intensity and Viscosity Ratio? Intensity and Hydraulic Diameter?


Now, after selecting, I don't know values of these parameters. I am grateful that guide me about values of these parameters.

My second question is about operating condition. In fact, I want to know that how to set this for my case? I don’t any have changed this my first simulation. Is this work correct?

I am grateful that guide me and if it is possible, please place useful links about these problems.


Thanks,



Best,



Aja

[CeesH]

Hi,

Regarding inlet turbulence, please reference this page in the solution manual: https://www.sharcnet.ca/Software/Flu...ug/node217.htm

Based on your inlet velocity, you can estimate the inlet reynolds number. As a first guess, you can just take the duct approximation I think. Then, I would go for the hydraulic diameter as second parameter, and do the same.

Anyway, your solution probably will not depend very much on these parameters, since the influence of the impeller will be much bigger. But it may depend a bit on the problem you are considering.

[aja1345]

Originally Posted by CeesH

Hi,

Regarding inlet turbulence, please reference this page in the solution manual: https://www.sharcnet.ca/Software/Flu...ug/node217.htm

Based on your inlet velocity, you can estimate the inlet reynolds number. As a first guess, you can just take the duct approximation I think. Then, I would go for the hydraulic diameter as second parameter, and do the same.

Anyway, your solution probably will not depend very much on these parameters, since the influence of the impeller will be much bigger. But it may depend a bit on the problem you are considering.

Thanks,

Do you have any opinion about the second question?

Best,

[CeesH]

operating condition should be the pressure that exists on the boundary of your domain. I would guess this is atmospheric, but it depends on what you are simulating of course.

[aja1345]

Originally Posted by CeesH

operating condition should be the pressure that exists on the boundary of your domain. I would guess this is atmospheric, but it depends on what you are simulating of course.

Thanks,

The pressure is atmospheric(101325 pa=default) and I have set "Reference Pressure Location" in center of turbine hub. Location of center of hub is out of computational domain and its coordinates is (0,0,0). Is there no problem?

Best regards,

aja

[ghost82]

The reference pressure point should be a point in your computational domain.

[aja1345]

Originally Posted by ghost82

The reference pressure point should be a point in your computational domain.

Why? I am grateful that guide me about this.

For the boundary conditions, the inlet velocity and static
pressure are imposed on the inflow and outflow boundaries,respectively, which are normal to the axis of turbine, But According the following link,
what is the exact meaning of following sentences? that is, I should not change the default values of reference pressure location and Operating pressure? correct?


"If pressure boundaries are involved, the adjustment is not needed and the reference pressure location is ignored."

https://www.sharcnet.ca/Software/Flu...#sec-ref-press

Thanks,

Best

aja

[ghost82]

I didn't know. I always set that point at coordinates where I know what is pressure, inside computational domain.