[FLASH-USERS] Question about near-surface temperature dropping below initial value in LaserSlab run

[yinru Wang]

Hi FLASH users，

I’m writing to ask for guidance on a behavior I’m seeing in a LaserSlab
simulation.

*Setup (summary):*

   -

   Code: FLASH (LaserSlab)
   -

   Initial target surface temperature: *900 K*
   -

   Ambient gas temperature: *room temperature*
   -

   Laser incidence: *45°* from the lower-right side
   -

   Laser fluence (energy density): *21.9 J/cm²*
   -

   I will attach screenshots (initial state and subsequent time steps) and
   my flash.par for full details of the run configuration.

*Observed behavior:*
Right after the simulation starts, a narrow row of cells immediately above
the target surface shows a temperature drop. As the run proceeds, the
near-surface temperature continues to decrease and stays around *400–700 K*,
i.e., *below the initial 900 K*, despite the ongoing laser irradiation.

*Questions:*

   1.

   Is such an initial cooling band near the surface expected in LaserSlab
   under certain settings ?
   2.

   Are there recommended parameters to avoid non-physical cooling below the
   initial surface temperature?

*Attachments:*

   -

   initial_state.jpg – initial condition (surface set to 900 K).[electron
   temperature]
   -

   temp_evolution_1.jpg, temp_evolution_2.jpg, temp_evolution_3.jpg –
   showing progressive decrease of near-surface temperature during the
   run.[electron temperature]
   -

   flash.par – full configuration file.

Any pointers or examples would be greatly appreciated. Thank you for your
time and support.

WANG YINRU
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