Help in Fluent DPM .....
 

Help in Fluent DPM……

I am simulating nanofluid flow over a circular cylinder in a rectangular domain.


The diameter of the hot circular cylinder is 1mm, length of the flow domain is 100mm and the height is 60mm. The cylinder is maintained at 310K while the inlet fluid temperature is 300K. I am using Fluent DPM and hence, the thickness of the domain is taken as 30nm which is equal to the diameter of the nanoparticle. The flow is steady at Re = 10 (velocity = 0.146m/s) and steady particle tracking is used. Group injection (10000 parcels) with constant particle diameter (30 nm) is used.

I am having doubts in determining the mass flow rate to be entered in Injection > point properties. I have tried two methods to calculate the mass flow rate

Method 1
Volume fraction = (number of nanoparticles x volume of a single nanoparticle) / Volume of domain
i.e Volume fraction = Total volume of all nanoparticles / volume of domain
In our case
0.05 (5% volume fraction) = Total volume of all nanoparticles / 100mm x 60 mm x 30nm
Which gives volume of nanoparticles = 9 x 10-12m3
Mass flow rate = 9 x 10-12 x 3690 (Density of nanoparticle) = 3.321 x 10-8 kg/s
As there are 10000 parcels, mass flow rate of a single parcel = 3.321 x 10-8 / 10000 = 3.321x10-12 kg/s
Method 2
Volume flow rate at the inlet = velocity x cross sectional area = 0.146 (velocity) x 60 x 10-3 x 30 x 10-9 = 2.628 x 10-10mm3/s
5 % of the volume flow rate = 0.05 x 2.628 x 10-10 = 1.314 x 10-11 m3/s
Corresponding mass flow rate = 1.314 x 10-11 x 3690 (density)
Mass flow rate of single parcel = (1.314 x 10-11 x 3690) / 10000 = 4.8486x10-12kg/s
While following both the methods, I am able to get reasonable particle tracks. But, when I plot contours > Discrete phase variables > DPM volume fraction. I am getting unreasonable values in the order of 1e-10 which is actually expected to be in the range of 0.05.
Moreover, there is no change in mean Nusselt number. It is same as that observed for pure fluid (air). I am unable to solve this issue.
It will be a big help for me if someone can help me in solving this issue.

I am also struggling with the same problem. How can one determine the number of particles injected and mass flow rate. In my case I am using a surface injection from the inlet.

Dear frends,

The number of particle you can plot in particlr varialbe- particle number in parcels,

graph- particle track-particle varaible-particle number in parcel

further you can also calculate it


I have the same problem with the plot reading about DPM property. can you guys share your solution.

thanks

I am also struggling with the same problem. I got the results too, there is no change in mean Nusselt number. It is same as that observed for pure fluid.