How to set an engine plane as an outlet?
 

Good night,


I am working on an uni project and I decided to show - using Ansys - the NASA's prototype STARC-ABL and how the boundary layer thickness is affected by the rear engine. I simulated a normal plane with similar dimensions at 222,22 m/s on the inlet surface and 0 Pa on the outlet surface, then I got its boundary layer.

But now, I have no idea how to simulate the NASA's prototype. Should I set the third engine as an outlet surface too? But when I do it, it requires the 'Gauge Pressure', but the only infos I have about its engine are: fan power, fan rpm and thrust.



My objective is showing that the rear engine fan can speed up that air layer around the fuselage and as consequence, the boudary layer thickness would be reduced partially, so I could compare it to the normal plane.

I attached a picture of the NASA's concept, if I haven't been clear about the issues I'm having.


Thanks for your attention.


(Image is from NASA's article.)


Attachment 76686

Thrust
 

If the thrust is known, you can calculate the mass flow rate since there is always a specific thrust for every engine, which is defined as thrust per unit mass flow rate. Using these two, you can determine mass flow rate and apply that. For your setup, you might be using ideal gas for air density. In that case, it is recommended to work with absolute pressure and not gauge pressure, i.e., you should set the operating pressure and operating density in the Operating Conditions panel to 0. Consequently, there should not be any boundary with 0 Pa as its condition. Labels at the boundary condition will still show it as gauge pressure but with operating pressure set to 0, it behaves exactly like absolute and expects absolute values as input. Velocity boundary condition in your scenario is incorrect.

Vinerm,

Thank you for your reply, it cleared me about some points.

I’m having some issues with my computer, but as soon as I get to do the simulations as you instructed me, I’ll update this thread with results.

Best regards!

Are you modelling the bypass duct of the engine. Or modelling only the inlet and exit of the engine as boundary conditions. This is little tricky and needs some iteration. To start with assume typical fan pressure ratio of the engine and estimate mass flow rate of the bypass nozzle for choked condition.

I was just setting the inlet and outlet.
Considering that the rear engine is an electric one, I decided to use a fan inside a engine duct with similar dimensions determined by NASA in their article. But before doing all this, I download a fan and tried some simulations in Fluent following some steps from youtube and this forum, fortunately I'm succeding.


Thanks for your help,
Best regards!