SimScale CAE Forum

Setting up a row of simulations of historic aircraft and selecting the best boundary conditions


#1

Hi everyone,

some time ago I had an idea for an interesting project, using the Simscale platform. CFD is an important and powerful tool for the development of modern aircraft, but wouldn’t it also be interesting to analyze historic aircraft?

For example I think about Dornier’s RS1, the “Wal” and the “DO-X”. Also an
analysis of Junkers planes, especially concerning the effects which are caused
by the waved surface of the wings would be interesting.

When enough aircrafts are analyzed
this could be a great database for other projects, of course I would like them
to be public so everyone can use them.

I began with an old flying wing, the H IX, because I found several good drawings as base of the CAD-design. The H IX is very interesting because, there are some reports on a difference between the calculated lift and the observed lift, especially in the aircrafts center, the effect caused the wings extension at the center, known as “Horten-tail”.

Now I am wondering about the boundary conditions of the simulation. If you take a look on the H IX you see, that the
engines are included in the wing and the exhaust stream influences a big part of the upper side of the wing. To simulate the engines influence, the boundary conditions have to represent the engines influence. The engines are called Jumo 004, but there isn’t any information on its influence on the fluid especially concerning the impact on the turbulence.

Do you have an idea how the engines influence could be simulated best and which are the best boundary conditions?

And what do you in general think about the project? Do you have some additional ideas or would you suggest a
special aircraft which should be included?


#2

Hi Niklas,

I like your idea. I think it will be a great effort but absolutely worth it. And it would be very interesting to see why some of those old designs are not used anymore.

Regarding H IX, you are indeed right that engine’s exhaust affects flow over the wings. While the problem could get quite complex, it should be possible to start simple and still get some good results. For example, for the exhaust, I would start with a velocity inlet, to the domain, and take turbulence parameters based on exhaust diameter and exhaust velocity, close to sonic velocity since it was a turbojet. This data should be available. Studying lift and other flight parameters should be done after this is settled.

I’m interested to see how your setup works. Keep us updated. It would be nice gather your work and present it as a collection.