November 25, 2019 at 11:09 amAbdelrahman92Subscriber
I am tracking particles falling in stagnant fluid using DPM. I am interested in particle velocity as a function of time (and terminal velocity). I have two questions:
(1) In the attached d picture, the x axis (time), is it the solver calculation time or the actual time that the particle spend in the column ?
(2) As I said I want to see the change of the velocity with time (as the particle settle down the column), the trend should start with unsteady velocity and finally reach steady state terminal velocity.
My Q: Should I use unsteady tracking ? I tried using steady uncoupled tracking (attached picture)
November 25, 2019 at 11:09 am
November 25, 2019 at 11:19 amRobAnsys Employee
Can you post an image of the Particle tracking panel? From memory the default is particle residence time but hard to know without looking at what you set.
November 25, 2019 at 11:22 am
November 25, 2019 at 11:32 amRobAnsys Employee
Assuming the model is steady that's probably particle residence time, and it looks to accelerate up very quickly from the injection. Try plotting velocity against path length.
November 25, 2019 at 1:00 pmAbdelrahman92SubscriberThanks for you answer.
Could you explain to me what is exactly the difference between steady and unsteady tracking?. I have read this section from the manual, but it is still confusing. For DPM, fluent solves the ODE (particle motion equation), which is by nature time dependent (dv/dt). So steady state tracking should give the v(t).
What would you suggest for my case, steady or unsteady ? (Remember I am interested in the change of the velocity with time
November 25, 2019 at 4:44 pmRobAnsys Employee
Steady should work as the particles are travelling though the domain and not altering the flow.
November 25, 2019 at 5:39 pmAbdelrahman92Subscriber
Many thanks for your help.
I expect to get two distinguished regions for the velocity profile (steady and unsteady) as the attached picture. However, what I got (previous pictures) is a sudden increase in the velocity to a constant value (most probably the terminal).
This case is very simple: I am using uncoupled tracking with no interaction with the continuous phase. The geometry is 2D cylinder has only inlet (zero velocity specified for the inlet continues phase) and the rest is wall. Recently I tried a geometry with only walls. In both case I initialized & patch the domain with zero velocity since the fluid Is stagnant
Could let me know what is most probably casing the issue with my results ??
Your effort is appreciated. Thanks
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