[AshinDaisy]

Hello there,

in my masters I studied the flow around an AUV and compared experimental / numerical results. Managed to get 20% error within the wake for turbulent characteristics using LES + VOF (Open Channel Flow to set a free-surface) and multibox meshing

Atm in my PhD I'm trying to model the same AUV with superhydrophobic surface. Air is to injected within AUV to create an air film to reduce the skin friction.

The AUV I'm working on is a bare hull without appandages. It is 0.2 im length and 0.04 m in diameter

here is the AUV profile

I'm using FLUENT 2020 R2 and ANSYS workbench defaults (geometry designer and mesher) for domain creation and meshing.

Problems:

I'll carry out PIV measurements within the year, using 8-12 micron superhydrophobic solution applied to the AUV surface

however I cannot set wall roughness using LES. Only RANS and SAS are open up the wall roughness settings from the boundary section.



Questions

1- Can the auto generated roughness (under wall boundary condition settings) maintain air film like manually generated roughness?

2- Considering my 3-D geometry, should I generate 8-12 micron roguhness in a random or orderly manner around the AUV surface? Would it be viable considering the size of the AUV? If so, how would I do it?