|
[Sponsors] |
June 20, 2004, 21:37 |
turbulent intensity
|
#1 |
Guest
Posts: n/a
|
Hello,
I am wonderring how to get intensity values from kinetic energy and dissipation values in Fluent 6.1. Because I got unreasonable turbulent intensity at some points, even though correct turbulent kinetic energy and dissipation values at these points. Could anybody help me and give me some hightlights? Thank you very much. Best regards, Zwdi |
|
June 23, 2004, 08:07 |
Re: turbulent intensity
|
#2 |
Guest
Posts: n/a
|
You might want to check what the reference value that the calculation of the intensity is based upon is.
|
|
June 23, 2004, 10:46 |
Re: turbulent intensity
|
#3 |
Guest
Posts: n/a
|
Turbulent Intensity is the ratio of the magnitude of the RMS turbulent fluctuations to the reference velocity:
I = (SQR(2/3*k))/vref where k is the turbulence kinetic energy and vref is the reference velocity specified in the Reference Values panel. The reference value specified should be the mean velocity magnitude for the flow. |
|
June 23, 2004, 20:44 |
Re: turbulent intensity
|
#4 |
Guest
Posts: n/a
|
Thank you vey much, guys. I didn't realize this is relative with the reference values. Thank you for your hightlights.
I have another question related with kinetic energy and disspation rate at the boundaries. I set UDF function of dissipation rate and kinetic energy at inlet boundary. After I initialize the calculation from inlet boundary(only initialize,0 iteration), I check my boundary condition to see if they are defined correcly. But from report of the value of one specified point at the inlet boundary, I found disspation rate(epsilon value) changed a lot. The value is largely different from what I set in UDF(20 times), while kinetic energy,intensity and velocity are resonable. I checked a lot and could not image what is the reason. For calculating epsilon, Fluent must use length scale at specified cell. Do you know how Fluent deal with length scale to get the epsilon values? Could you please give me a little bit highlights on this? Thank you very much. Best regards, Zwdi |
|
June 24, 2004, 05:57 |
Re: turbulent intensity
|
#5 |
Guest
Posts: n/a
|
Hello, In some complex flow problems it is impossible to distiguish where is layer flow, where is turbulant flow. Can we always use turbulance model to calculate layer flow problems ? In theorey, it sounds reasonable, but I am wondering if it works or not.
In FLUENT, I simulated flows in micropump, using layer flow model and K-e model, respectively, I got different results. The flow patterns are similar, the velocity is smaller using K-e model than using layer model. Do you have any ideal ??? Thanks |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
How to calculate Turbulent Intensity? | prem | FLUENT | 10 | September 29, 2018 10:46 |
k-epsilon: Defining turbulent intensity and length scale? | klausb | OpenFOAM | 0 | January 23, 2011 08:28 |
Turbulent intensity for pressure Outlet Boundary condition | Mohsin | FLUENT | 1 | April 30, 2010 11:36 |
Turbulent intensity | swe704 | Main CFD Forum | 0 | November 13, 2009 04:42 |
setting value of turbulent intensity and turbulent viscosity ratio in wind tunnel | nuimlabib | Main CFD Forum | 0 | August 4, 2009 01:05 |