Learning Forum

[cs_zy]

when I use DPM model,how to compute Total flow rate ,when setting Point Properties for Surface Injections in 2D model?

The Al2O3 volume concentration is 0.5vol% and density is 3970. The diameter of Al2O3 is 30 nm.Water idensity is 996.3.

And what any other parameters need I know?

Really appreciate if you could help me.

[Karthik Remella]

Hello Which flow rate are you interested in? The flow rate of the fluid or the rate at which the particles are being released? Or are you looking to estimate the number of particles?
Karthik

[cs_zy]

The particles are being released and this blank is just called the Total flow rate.
Sir,really appreciate if you could help me.

[Rob]

By default Fluent assumes the 2d domain is 1m thick. At 30nm (ie tiny) the particles are pretty much doing to follow the flow.

[cs_zy]

Do you mean to calculate it like this way? But the other two Division are too small. Does it matter. Really Appreciate again´╝ü´╝ü´╝ü

[Rob]

You have a volume flow from the liquid: velocity*area. From that you can get the particle volume flow (5% of fluid), and then the mass using the particle density.

[cs_zy]

Is it mean value of time when the inlet velocity change with time? And My case is transient. Is the Total flow rate related to the integral time step of flow field or other parameters?

[Rob]

The total flow is how much mass per second you're adding through that injection.

[cs_zy]

Thank you!
YesÒÇÇ´╝® know .I mean if my inlet velocity is changing with time and how should I compute? Using time average velocity instead of transient velocity?

[Rob]

Ah, time varying injection properties would need the DEFINE_DPM_INJECTION_INIT macro, which is covered in the manual. An easier approach would be to use multiple injections which turn on/off at certain times or ignore the transient part and use an average.

[cs_zy]

Thank you!
Yes.I have used DEFINE_DPM_INJECTION_INIT.
How do I compute Total Flow Rate after using DEFINE_DPM_INJECTION_INIT. Can I use time Average Velocity to flii the Blank.

[cs_zy]

Hello, Rob .
Can I realize Total Flow Rate changing with time if use UDF like this? And How do I compute Total Flow Rate changing with time(what do I fill the blank)
Really appreciate!!!!

[Rob]

I suspect it's PP_FLOW_RATE(p) from reading https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v212/en/flu_udf/flu_udf_sec_define_dpm_injection_init.html Try it and see what happens.

[cs_zy]

Thank you.I will try.For Total Flow Rate(kg/s) this blank,what should I fill in. It can be only filled with a constant but not a UDF. Can I fill this Blank by using Time Average Velocity*Area*Mass concentration after using PP_FLOW_RATE(p)

[Rob]

Read how to hook up the DEFINE_DPM_INJECTION_INIT UDF. It's not the same as setting a boundary via DEFINE_PROFILE

[cs_zy]

Thank you Sir.
I have used DEFINE_DPM_INJECTION_INIT UDF. But how can I use UDF instead of a constant in the line of Total Flow Rate.It's like that this blank can only be filled with a constant.
Really appreciate it.

[cs_zy]