[FLASH-USERS] Internal energy is not reaching statistical steady state in StirTurb (homogeneous isotropic turbulence) problem

[Reyes, Adam]

Hi Shadab,

The stirring is injecting kinetic energy into the simulation constantly throughout the simulation. This gets dissipated to internal energy through viscosity and has nowhere to go with a periodic box. 
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Adam Reyes


Code Group Leader, Flash Center for Computational Science  
Research Scientist, Dept. of Physics and Astronomy
University of Rochester
River Campus: Bausch and Lomb Hall, 369  
500 Wilson Blvd. PO Box 270171, Rochester, NY 14627
Email adam.reyes at rochester.edu
Web https://flash.rochester.edu
 (he / him / his)


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> On May 10, 2024, at 12:42 PM, Alam Shadab TU Ilmenau <shadab.alam at tu-ilmenau.de> wrote:
> 
> Hi,
> I am simulating homogeneous isotropic turbulence with stir forcing. I am facing a challenge that the internal energy is not reaching to statistical steady state no matter how small the energy supply rate is. On the other hand, the kinetic energy has reached steady state. Following are the plots of these quantities:
> <int_energy.png>
> <kinetic_energy.png>
> input parameters for this run are: 
> energy input - 1e-4 per mode (around 100 modes are stirred)
> kinematic viscosity: 0.1
> diffusivity: 0.1
> grid: 128^3
> 
> I simulated the Stirturb problem for many other input parameters using split and unsplit methods, but I am getting the similar trend for the energies.
> 
> What am I missing because of which the internal energy is keep on increasing? Could anyone please help me with this?
> 
> Best regards,
> Shadab
> Technische Universität Ilmenau, Germany
> 
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