topic Re: Inlet Geometry not allowing crossover to main fluid volume HELP for industry in CFD Forum

Inlet Geometry not allowing crossover to main fluid volume HELP for industry

Anonymous — Wed, 18 Oct 2017 05:20:55 GMT

Dear Autodesk,

I have now built a model which is able to run, I have set up all the boundary conditions similar to the other topics that have been presented. I am having a problem modelling the scalar inlets:

It Appears that the scalar value diffuses through the first part of the extrusion (the part that hangs outside the model), and then stops at the block that appears at the crossover of this inlet into the model, not reaching the internal part of the volume.

I have tried different ways to extrude these inlets (I am modelling using inventor), But none of which seem to allow the fluid to cross over into the second, third and then obviously into the main volume. Do these mass flow rate inlets need a pressure of 0? could that be changing the result?

I noticed in the model for another person doing a similar study had 3 different blocks as the inlet, all of which were put as the volume-mixture.

Am i meant to somehow do a negative extrude through the side walls of the model and then extrude a single solid that doesn't cross any boundary (thus creating in reality 3 separate blocks that need to be made into the variable volume. this is very confusing as I have followed all the relevant material up to this point. Attached is a plane view of what I am trying to describe, as well as my inventor file and design study.

I am also wondering, as stated by the previous user doing a carpark model - I have changed my scalar values to be divided by 500, subsequently increasing all my mass flowrates by 500%, the scalar result that I have, Should that be (result x 1000 000ppm) *500, or is the result simply just (result x 1000 000ppm)? In other words does the result need to be converted back.

For your knowledge I am new to inventor and CFD for a new position I am in.

Kind Regards and thank you in advance

Jack H

Re: Inlet Geometry not allowing crossover to main fluid volume HELP for industry

Jon.Wilde — Wed, 18 Oct 2017 06:54:26 GMT

Hi Jack,

I would tend to cut a hole in the wall where you have the flow going in (a sketch and an extrude within the wall part) and then just add a single extruded block as a new part to each inlet/outlet. So you basically just have the main air volume and then one additional for each inlet.

My guess is that right now you have a solid part between the air and internal.

The extrusions are really short too, make them something like 5x their width in length.

Leave your mass flow rates to whatever they are in reality. Am I reading it right that you multiplied them by 500?

It doesnt matter in the end whether you divide up the scalar values, just that you keep consistent. What value are you trying to model at the inlets?

We cannot open a cfdst file, you would need to save out a CFZ for us to open it 🙂

Thanks,

Jon

Re: Inlet Geometry not allowing crossover to main fluid volume HELP for industry

Anonymous — Wed, 18 Oct 2017 21:49:08 GMT

Dear John,

I am Just about to update my models,

I am trying to make these holes in my Inventor model, this is proving to be quite difficult as any negative extrude I do just cancells out my inlet geometry, and making a new sketch and tracing out the outlet geometry isn't working as I cant select these to make a hole

Re: Inlet Geometry not allowing crossover to main fluid volume HELP for industry

Anonymous — Wed, 18 Oct 2017 22:45:01 GMT

Sorry ignore the query about the extrusions, I am working on a work-around now. Wasn't sure how to delete the post. Will upload updated when I am finished.

In regards to x 500, I am doing that based on the thread started by rpadovani who said that his solution was diverging due to the difference in mass flow rate velocity and relief/supply flow rates

Total amount of carbon monoxide into the carpark is 8732 g/h. so at the BC I had this value as (8732 x 500), and then 0.002 as the scalar property, maybe the difference in flows might not be as critical for this model?

Cheers for the help 🙂

Re: Inlet Geometry not allowing crossover to main fluid volume HELP for industry

Jon.Wilde — Thu, 19 Oct 2017 07:04:32 GMT

I would stick to the normal flow rate, better than moving away from reality.

Check out the post I made on your thread with the CFZ file here.