What is turbulence flux relating to EBC's?

Peter Parrish_22382
Peter Parrish_22382 Altair Community Member
edited June 14 in Community Q&A

Hi,

I am trying to prescribe an inlet turbulence intensity for flow past a square cylinder. I believe that This can be accomplished using an essential boundary condition; however, I need to know more details. 

How is turbulence diffusion flux defined in AcuSolve? It would be great to get a detailed understanding of this option.

Here it's used in hwcfd,

image

Here is what I was able to find in the documentation for hwcfd

image

Thanks,

Peter Parrish

Tagged:

Best Answer

  • acupro
    acupro
    Altair Employee
    edited June 14 Answer ✓
    Peter Parrish_22382 said:

    Thanks for your help. I believe everyone may benefit from a better understanding of turbulence flux. I'm guessing it is the same as percent turbulence intensity as seen in the constant inlet condition menus.

    The reason I would like to use EBC is to possibly change the turbulence intensity depending on its position along a given special dimension.

    It is definitely not the same as percent turbulent intensity.  The units of turbulence flux are kg/sec^2, where turbulence intensity is unitless.  (Turbulence_flux is generally type = free, meaning it falls out of the solution based on the other settings/values.)  I don't see any method to specify a profile of turbulence intensity on a single surface.  Probably the best you could do is split the inlet surface into a series of sections, on each of which you could specify a different turbulence intensity.  It will be stair-stepped instead of a smooth profile, but not constant.

Answers

  • ydigit
    ydigit
    Altair Employee
    edited June 6

    I would suggest using the option of intenstiy from the HM-CFD interface, unless you are absolutely sure about going the EBC way. 

    I will try to find out exact definition of turbulence_flux.

    image

  • acupro
    acupro
    Altair Employee
    edited June 11
    ydigit_21275 said:

    I would suggest using the option of intenstiy from the HM-CFD interface, unless you are absolutely sure about going the EBC way. 

    I will try to find out exact definition of turbulence_flux.

    image

    As ydigit shows, with the turbulence tab in the BCs for a Constant velocity inlet, you can define the turbulence intensity and length scale.  Those are not available when using the Profiled options for the inlet.

  • Peter Parrish_22382
    Peter Parrish_22382 Altair Community Member
    edited June 13

    Thanks for your help. I believe everyone may benefit from a better understanding of turbulence flux. I'm guessing it is the same as percent turbulence intensity as seen in the constant inlet condition menus.

    The reason I would like to use EBC is to possibly change the turbulence intensity depending on its position along a given special dimension.

  • acupro
    acupro
    Altair Employee
    edited June 14 Answer ✓
    Peter Parrish_22382 said:

    Thanks for your help. I believe everyone may benefit from a better understanding of turbulence flux. I'm guessing it is the same as percent turbulence intensity as seen in the constant inlet condition menus.

    The reason I would like to use EBC is to possibly change the turbulence intensity depending on its position along a given special dimension.

    It is definitely not the same as percent turbulent intensity.  The units of turbulence flux are kg/sec^2, where turbulence intensity is unitless.  (Turbulence_flux is generally type = free, meaning it falls out of the solution based on the other settings/values.)  I don't see any method to specify a profile of turbulence intensity on a single surface.  Probably the best you could do is split the inlet surface into a series of sections, on each of which you could specify a different turbulence intensity.  It will be stair-stepped instead of a smooth profile, but not constant.

Categories