Problem with VEL_PART

[Hosein Sadeghi]

Hello,

I am trying to define velocity for ejecting solid particles from a burner, with VEL_PART, but it seems it does not work. I have also tested VEL_PART =0 and HRRPUA= 0, but the particles still move upwards. So the ejection velocity of particles seems to be not following HRRPUA and VEL_PART. I wonder if you would please help me to find the reason. Please see the input file attached. Thank you.

Regards,

Hosein

[dr_jfloyd]

VEL_PART is the velocity the instant the particles are inserted. They will then be subject to drag forces from the local flow field. You have TMP_FRONT=300 for your burner so even with HRRPUA = 0 there will be a plume forming due to bouyancy. Your particles have a 15 micron radius. Compute the terminal velocity of these particles and compare it to the velocities in the domain.

[Hosein Sadeghi]

Thank you for your reply. If I want to decouple particle movement from the gas flow, is it correct to set a very small value for DRAG_COEFFICIENT (for example  0.001) and a desired value for VEL_PART?

from technical user guide I can see that the minimum DRAG_COEFFICIENT for spherical particles is 0.44 (Re> 1000).

Hosein

[dr_jfloyd]

Setting a small drag coefficent will decouple particles from the gas flow, but in that case not sure why you would bother adding such small particles that just move in straight line and only slowing down due to gravity.