4 Replies Latest reply on Aug 24, 2009 6:09 PM by Joe Galliera

    Flow simulation on a very small scale

    Gary Gilmartin

      Hello

       

      Does anyone have experience using flow simulation software on very small parts, e.g. 1 micron?

       

      Does the software give accurate results at this scale?

       

      Thanks in advance

       

       

      Gary

        • Re: Flow simulation on a very small scale
          Mauricio Martinez-Saez

          2993 wrote:

           

          Hello

           

          Does anyone have experience using flow simulation software on very small parts, e.g. 1 micron?

           

          Does the software give accurate results at this scale?

           

          Thanks in advance

           

           

          Gary

           

          I believe that will do the same accuracy (on % error) that on bigger models, unless the solver have some limitation on number of decimals... but you need to define a very fine mesh.  Can you do the flow simulation at a bigger scale?
          • Re: Flow simulation on a very small scale
            Joe Galliera

            I have this in my notes from the developers:


            Flow Simulation is a computational fluid dynamics  (CFD) program which solves the Navier-Stokes equations. The Navier-Stokes  equation assumes the fluid particles are a continuum. At very small channel  thicknesses this assumption may no longer be valid. The accuracy of the  Navier-Stokes equations can be defined with the Knudsen number Kn=L/D (L- free  path of gas molecules, D - typical diameter size) less than 0.01. At Kn<=0.01  the hypothesis of continuous flow is correct, this case could be calculated with  our program. At Kn>10 the gas rarefaction is too much and the hypothesis of  continuous flow is not correct. A free path of gas molecules can be estimated  with the following relation: L~1.225*Vis*k^0.5/(Ro*a). Here Vis – dynamic  viscosity; k – adiabatic power; Ro – density; a – speed of sound.