And then the change got modelled... well, kind of...

Preparing for Aircraft Commerce MRO-Operations conference in Bangkok on 18/19 October, I have spent some time doing turbo machinery modelling using GasTurb 14, developed by Dr Joachim Kurzke and his team of predominantly former MTU GMBH designers.

There are fundamental constraints on the design of fluid flow systems, the maths is well established, and generally works well. In modelling the flight performance that has been observed, we can actually get that to be represented by the turbo machinery software, however, the software alters an additional value in order to achieve the same outcome... and that then gives some thoughts as to how it is possible to do the Sun Tzu like thing of "be where you are not" kind of thing. When doing the analysis longhand, (well, using a turbo machinery mathcad code the flight performance gets modelled by a single variable that is related to the change that is made), the answer is close to the observed performance. These two different analytical outcomes suggest that there is a pretty outrageous workaround of expected physics happening, and thankfully, there is some peer reviewed published work that happens to give more than a hint as to how a "limit" can become side stepped.

Will be presenting at the Aircraft Commerce MRO-Operations London conference as well, in November, and at both of these, the means to avoid a limit in flow will be presented. The flow dynamics around the bit that we modify is the simple bit, relatively, although it is also still remarkable. How the turbo fan engine still accommodates the change and works given the constraints that must be imposed to fluid flows has caused considerable anguish. Finding a simple, single image that happens to show how it is possible makes for a good day.

To engineers out there, the question is, "how do you avoid the limitations of mach one M1 (or M^2) in a duct without going crazy?". What appears to work is pretty neat. How to make the impossible work without breaking the maths has been a question begging an answer.