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Ax & Dx

Thu, 09/17/2009 - 5:24am — Michaela
Hi, I don't understand the following error: when I choose AX=DX=1 (=Default) the preprocessor displays the error Longitudinal eddy diffusivity [DX= 1.000] 10x > DX-theory= 0.0351 for waterbody 1:Model may be unstable Longitudinal eddy viscosity [AX= 1.000] 10x > AX-theory= 0.0351 for waterbody 1:Model may be unstable when I choose AX=DX=0.0351 the preprocessor displays the error Longitudinal eddy viscosity [AX=0.035] < 0.1 or > 100 for waterbody 1 Longitudinal eddy diffusivity [DX=0.035] < 0.1 or > 100 for waterbody 1 so I chose AX=DX=0.1 an no error appears now. But I don't understand the first error report. What means DX-theory = 0.0351? And why I mustn't choose 1 if the array is 0.1 - 100? Thanks for any explanation. Many regards, Michi
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Hydrodynamics
Mon, 09/21/2009 - 1:54pm — chris

Hi Michaela, This was a mistake - the preprocessor should have given a warning not an error. There's a newly uploaded preprocessor (9/2009) at http://www.ce.pdx.edu/w2/ that corrects the mistake. Keep in mind this is just a theoretical calculation of DX/AX meant to assist the user. Also, the limits of the warning for AX or DX have been extended to < 0.01 and not 0.1 m2/s in the latest release of the preprocessor. Chris