Immersed solids + Compressible flow + transient solution in recent versions of CFX??
 

Dear all,

I am in my final stage of my PhD working on Stirling engines and the "novelty" of my work would be examining if 2 Wankel type rotors could replace the reciprocating pistons in an alpha-type solar dish-Stirling engine.

I've been using Fluent for my work so far, using the dynamic mesh capabilities etc but there is a significant issue which greatly affects my results.

The problem:

As you may already know, the dynamic mesh tool in Fluent requires that the deforming volume domain is not split; this means, for my case, that there should be no seals between the rotors tips and their casing. This results in significant pressure loss and consequently little power (if any at all..)

There are 2 possible "remedies" to this:
1. Learn CFX and try the immersed solids approach, or
2. Create subroutines in Fluent to mark cells and specify a momentum source.

Since the latter seems to me as difficult or time consuming as learning CFX from scratch, I read some stuff about immersed solids, including some posts here, all suggesting that immersed solids with compressible flow in transient mode is not possible or reliable.
I noticed however that most of these posts were from '09-'10.

So has there been any fix to that in more recent versions of CFX (13, 14) ?
I would love to share pics and sketches but at this stage the engine layout should remain somehow "confidential".

Thank you very much.

Best regards,
Thanos Alexakis

The CFX Modelling guide has a list of the many restrictions on immersed solid modelling. Immersed solids works fine in transient, but it does not support heat transfer or compressible flow. They did a lot of work in immersed solids in recent releases (V14 added turbulent boundary layer modelling to immersed solids for instance) and I suspect a number of these limitations will be addressed in future releases.

Thank you very much.

Best regards,
Thanos Alexakis