Hi nek users,<div><br></div><div>I'm getting an error I don't understand, perhaps someone can help. I'm simulating the Boussinesq equations in a 2D box of aspect ratio 2 with periodic side BC, stress-free velocity and fixed-flux temperature on the top and bottom, and at a Rayleigh number of 10^8. My time step is 2^-6; and longer and there are CFL problems. The part of the logfile where the error first appears is below. Any idea?</div>
<div><br></div><div>Thanks a lot,</div><div><br></div><div>David </div><div><br></div><div><br></div><div><div> 321 Hmholtz VELX: 1 1.8722E-04 9.4841E-04 3.0177E-02</div><div> 321 5.5836E+03 3.0971E-03 1.8028E+06 16 alph1x</div>
<div> 321 halpha 16 9.1147E+00 1.6433E-01 1.6202E-03 1.5295E-03 3.2457E-04 9.6963E-05 5.3573E-05 2.3766E-05 1.5049E-05 1.1283E-05</div><div><br></div><div> 321 Hmholtz VELY: 1 4.5111E-04 3.0971E-03 3.0177E-02</div>
<div> 321 16 alpha: 4.3959E-02 1.3360E-03 1.2680E-04 6.4401E-06 -3.8972E-06 3.2052E-06 7.4030E-06 3.4569E-06 2.8993E-06 1.4221E-06</div><div> 321 16 3.5585E-04 1.2617E-07 2.8203E+03 alph12</div><div> 321 U-Pres gmres: 3 2.6567E-09 4.1491E-09 1.2617E-07 1.5726E-03 2.5913E-03</div>
<div> 321 DNORM, DIVEX 7.71505530689053011E-6 2.65666629955944499E-9</div><div> 321 6.4200E-04 6.4809E-03 Fluid done</div><div> 321 6.420000E-04 7.911223E-01 1.711772E+00 umax</div><div> 321 0.6420E-03 t_av= 0.5000E+00 Ek= 0.1953E+00 Nu= 0.1000E+01</div>
<div>Step 322, t= 6.4400000E-04, DT= 2.0000000E-06, C= 0.000 5.4661E+00 9.7695E-03</div><div> Solving for heat</div><div> Solving for fluid</div><div> 322 Hmholtz TEMP: 1 9.9844E-03 6.0396E-01 2.4836E-02</div>
<div> 322 6.4400E-04 1.0539E-03 Heat done</div><div> 322 2.0339E+03 5.8756E-03 3.4616E+05 17 alph1x</div><div> 322 halpha 17 3.3193E+00 1.0787E-01 5.3974E-04 9.8243E-04 3.7291E-04 2.3705E-04 5.1605E-05 3.4660E-05 1.1899E-05 1.1993E-05</div>
<div><br></div><div> 322 Hmholtz VELX: 1 1.2039E-03 5.8756E-03 3.0705E-02</div><div> 322 5.6870E+03 NaN NaN 17 alph1x</div><div> 322 halpha 17 9.2834E+00 1.7756E-01 1.8590E-03 1.7684E-03 3.7603E-04 1.1302E-04 6.3138E-05 2.9137E-05 1.9115E-05 1.5046E-05</div>
<div><br></div><div> 322 5000 **ERROR**: Failed in HMHOLTZ: VELY NaN NaN 3.0705E-02</div><div> 322 17 alpha: NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN</div>
<div> 322 17 NaN NaN NaN alph12</div><div> 322 U-Pres gmres: 100 NaN 4.1491E-09 NaN 5.2696E-02 8.8512E-02</div><div> 322 DNORM, DIVEX NaN NaN</div><div> 322 6.4400E-04 6.0996E-01 Fluid done</div>
<div> 322 6.440000E-04 -9.900000E+21 -9.900000E+21 umax</div><div> 322 0.6440E-03 t_av= 0.5000E+00 Ek= NaN Nu= NaN</div><div>Step 323, t= 6.4600000E-04, DT= 2.0000000E-06, C= 0.000 6.0793E+00 6.1319E-01</div>
<div> Solving for heat</div><div> Solving for fluid</div><div> 323 5000 **ERROR**: Failed in HMHOLTZ: TEMP NaN NaN 2.4836E-02</div><div> 323 6.4600E-04 5.2047E-01 Heat done</div>
<div> 323 NaN NaN NaN 18 alph1x</div><div> 323 halpha 18 NaN NaN NaN NaN NaN </div></div>