[FLASH-USERS] extreme "sod"

[Alan Calder]

John-

First question- is the problem relativistic?

A quick look at the results you sent suggests to me that
your initial time step needs to be smaller. The time
step from the hydro routine is listed as 1.04255E-12,
while the time step it took was 1.0000E-10. Suggest
you try cranking the initial time step down to something like
1e-15.

You can do that with the line

dtinit                  = 1.e-15

in the flash.par file. But that is pretty small.



Alan Calder

On Mon, 25 Apr 2011, John Wohlbier wrote:

> I'm trying to solve a 1-d planar "sod" problem with a very large pressure 
> jump (motivated by the desire to do Sedov where the initial pressure grows 
> without bound with decreasing grid size), but I'm getting a non convergence 
> of the Riemann solver. I was wondering if anyone wanted to try their hand at 
> a "Sod" problem with:
>
> gamma = 1.66667
> pL = 1e19
> pR = 1e-8
> rhoL = rhoR = 1.0
>
>
> Below is some of my output. Something has obviously gone wonky in the initial 
> step. I would like to know if this is user error. If anyone wants input 
> files, etc. let me know. I based this off the Sod that comes with the code, 
> but changed the initialization for 1d.
>
> jgw
>
>
> Initial dt verified
> *** Wrote checkpoint file to sod_hdf5_chk_0000 ****
> *** Wrote plotfile to sod_hdf5_plt_cnt_0000 ****
> Initial plotfile written
> Driver init all done
>       n          t         dt |  dt_Hydro
>       1 2.1404E-13 1.0000E-10 |  1.04255E-12
> *** Wrote checkpoint file to sod_hdf5_chk_0001 ****
>       2 2.0021E-10 1.0000E-10 |  6.68035E-37
> *** Wrote checkpoint file to sod_hdf5_chk_0002 ****
>
> Nonconvergence in subroutine rieman
>
> Zone index       =           53
> Zone center      =   0.48499999999999999
> Iterations tried =           12
> Pressure error   =   2.50736728133274093E-005
> rieman_tol       =   1.00000000000000008E-005
>
> pL       =   1.00000000000000004E-010  pR       =  1.69945124795326129E+0
> uL       =  -8.55361906563791716E+020  uR       = -2.95619597114146315E+0
> cL       =   1.29112354172635239E-010  cR       =   53225794783526600.
> gamma_eL =    1.6670000000000000       gamma_eR =   1.6670000000000000
> gamma_cL =    1.6670000000000000       gamma_cR =   1.6670000000000000
>
> Iteration history:
>
>   n                    p*
>   1    0.381681833473E+23
>   2    0.666931951757E+39
>   3    0.849680290662E+47
>   4    0.490680234160E+51
>   5    0.383003596149E+53
>   6    0.367516282470E+54
>   7    0.125015589879E+55
>   8    0.226538136461E+55
>   9    0.279461332702E+55
>  10    0.290630268330E+55
>  11    0.291332257483E+55
>  12    0.291339562436E+55
>
>
>
>

-- 

Alan C. Calder
Department of Physics and Astronomy
State University of New York at Stony Brook
Stony Brook, NY 11794-3800

email: acalder at mail.astro.sunysb.edu
office: ESS 438
phone:  (631) 632-1176
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web: http://www.astro.sunysb.edu/acalder