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sajeesh March 4, 2013 06:58

problem in particle injection in discrete phase modelling
i am trying to simulate the transient particle tracking in a fluid flow through a square channel.i want to study the transient behavior of a single i can inject one partilce in to the flow stream...
Even i am managed to give group injection and when i am running the code it is showing particle deleted during some iterations..and also in plot particle tracking result tracking of particle have been done...any body can help me

diamondx March 4, 2013 12:27

have you check unsteady ??? if yes look at your stop time in injection, it should be of a large value so injection never stops.

sajeesh March 4, 2013 12:43

thank you sir.

Sir i am doing unsteady..but sir in ansys user guide i saw if we put start time and stop time as zero..injection will be onlly in the starting of calculation...sir exactly i need one particle in the flow....

My problem defnition is
initially i have no particle so i apply mass flow rate as inlet condition and preesure as outlet boundary condition..after simulation i will get inlet pressure the total preesure drop i can found out\
I need all the above things when a solid sphere is moving unsteadily in the fluid.the present condition is as follows.initially solid sphere is placed in the is taken by the drag force acting on it.later this sphere will modify the flow as two way coupling..after that steady state reached...

sir in this model how i get one particle instead of one stream of particle

Sir i am not sure my approach is correct..pls g

diamondx March 4, 2013 12:45

in your injection, how many particle are you giving ??

sajeesh March 4, 2013 13:01

i have no answer for that...i dont know to calculate that also....i given the inlet condition as single
x y and z velocity as zero
mass flow rate of particle a low value as 8e-14 kg/sec to make the particle as one per minute....

but during the calculation in console

'particle trapped one ' it is showing after some iteration' particle escaped one ' showing ...even we stop iteration before escping particle ..i search for the result as follows
the plot and animation
particle tracking

particle ID''

no result is showing as a result

now i have doubt in setiing the particle time step and fluid time step i should set up that.i didnt understand these things from user guide

A CFD free user March 4, 2013 15:30

I had such problem before. I think you need to have a deep look at the fluent user guide concerning simulation setup and setting parameters model for step time, step size and etc. Maybe you better to start a steady state and after get enough experience change to unsteady. I don't know how I solved the problem now but I can recommend you that the key to solve the problem lies in step time and size.

sajeesh March 4, 2013 21:52

i tried but its not r right sir...the key area is the time step....actually how the iteration is done...iterating the fluid in a certain number.then injecting the particle ..the particle advancing time period how we can determined..when the DPM iteration is happening...i have no idea from the guide....pls help me sir...regarding the iteration procedure

A CFD free user March 5, 2013 12:51

You need to get a converged solution without DPM model, then inject the particles. There are several types of particle injecting. You can inject only one particle or a group of particles or other types described in user guide. You can even adjust Rosin-Ramler parametrs and use this method. Hope it help.

sajeesh March 5, 2013 23:18

sir one more doubt..if i want one particle to i put one particle in one stream..option single in injection means that single stream.that is not one particle.sir what value i should give to the mass flow rate for one particle.and initially i want to place the particle not with one velocity at the injection point.can i set a velocity of zero for a stationary particle at the inlet.

sorry sir if it is blunder

thank a lot for your reply

A CFD free user March 6, 2013 12:34

I think what you need is injecting massless particle. In this case you don't need to set velocity value or even mass flow rate. The only thing would be required is the position of the injected particle. Actually, in this method of injecting the particles move along the stream lines.
Good Luck

A CFD free user March 6, 2013 12:48

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