Dendrite stability

[matt_hughes]

Hi Micress forums,

I have ran a simulation for set thermal conditions for 30 seconds. I then ran lots of simulations in which i have restarted this simulation but changed the thermal gradient or solidification front velocity independently to induce a change in the dendrites. When I increase the velocity or the thermal gradient to a certain value i get expected results of new dendrites forming from the interdendritic regions, however, when i decrease the thermal gradient or solidification front velocity I do not see any change in the dendrite array. I have reduced the thermal gradient and velocity to as low as 1% of the initial values but still i see no change. Images of the initial dendrite array, dendrite array after changing thermal gradient, and dendrite array after changing velocity are attached.

Do you have any suggestions as to what could be changed to get a dendrite to fall back from my initial simulation?

Details of the thermal parameters are the following for the images attached:

Initial simulation ran for 30 seconds => T_grad = 40 K/cm and Cooling Rate = -1.4 K/s

Reducing thermal gradient => T_grad = 0.4 K/cm and Cooling Rate = -0.014 K/s

Reducing solidification front velocity => T_grad = 40 K/cm and Cooling Rate = -0.014 K/s


Looking forward to your response

Many thanks,
Matthew

[Bernd]

Dear Matthew,

From the images you attached it does not seem as if you had reduced the velocity. Perhaps, the system takes quite long until it adapts to the new conditions. Did you check whether the intended velocities were really reached? You can use the .TabL output and plot the front position or front temperature over time to see whether you have reached steady-state.

Bernd