Szymon Szyszko asked 4 years ago
Hi Andre,
As you probably noticed, I have been using flow5 quite a lot in the past few weeks. As much as I love your software, I have found some things that could work slightly different. Recently I have noticed I could not set up angular rate for any of the analyses as an input variable. I assume angular rates are applied under the hood in the stability analysis, however, this is not available to the user to manipulate. Do you think it would be possible to add it to all the analyses as something optional for the user to tweak?
Also, as mentioned in some of my previous posts, I’m having quite a lot of problems with control analysis itself. I find wake defined for every angle of attack separately difficult to work with, using flat-panel wake (wake-mesh intersections). Do you think it would be possible to be able to set “fixed” wake for AoA selected by the user in the mentioned module? Control analysis is a great tool, allowing you to check few things, and is currently the only place you can change Beta angle, but has its limitations. As I try to avoid VPW wake (expensive in terms of calculational time), control analysis becomes unusable, when working with fuselages. I know that fixed flat panel wake is a simplification and results are not perfect, but letting users decide what they want to use would be a great feature!
Thanks in advance for your consideration!
Szymon
techwinder Staff answered 4 years ago
Hi Szymon,
About angular rates: they are not an input parameter in Etkin and Reid’s theory of flight dynamics. They are instead a resulting variable that can be plotted in flow5 in the time reponse graphs.
Initial rates can be set when selecting the option “Initial conditions response” for these graphs.
André
PS. I’ll open a new thread to answer the questions about T6 analyses and wakes since this is a bit tricky and also the answer may be of interest to other users.
Szymon Szyszko answered 4 years ago
Hi Andre,
Thank you for your reply. Just to clarify, I aim to be able to get all of the coefficients out from normal analysis. Absolutely perfect scenario for me would be to be able to analyse T2 case with Beta != 0 and angular rates also set either to 0 or to the value selected by the user. Even better, if I could select alpha range, alpha step, beta range, beta step, angular rate range and angular rates step, where angular rates and beta steps would probably be equal to range, as no more than one oppoint would be needed, at least in my usecase. Also, if that would be possible with simple flat panel wake it would mean I can run the simulation in no time, which is important in optimization exercise I’m currently performing. I know that this might diverge slightly from your concept, but this could be a great feature. This approach would open up some of the calculations to the users, allowing them to test the software with greater detail, helping gain confidence in the output values! Do you think this would be possible to implement somehow? Even if mixed ranges thing would be tricky, having the static parameter to tweak would be a very helpful feature!
Thanks,
Szymon
techwinder Staff answered 4 years ago
T12 with non-zero beta is technically possible using Mark Drela’s method implemented in AVL. I’ve had it on the todo list for some time but it didn’t feel like a priority in the beta phase. I’ll give it some thought in the coming weeks.
Angular rates in input are also technically possible – the uniform velocity field is replaced by a velocity field corresponding to a solid body rotation. This is the way angular derivatives are calculated in stability analyses. However this would be a custom development requiring significant work, and as far as I can see it wouldn’t be of much use to the majority of users, so I don’t know. In fact I don’t really understand how you intend to use the results.
André
Szymon Szyszko answered 4 years ago
Thanks for your consideration.
The use case is such that I can run 1 sweep analysis for ranges of parameters (alphas, betas, angular rates etc). This way I can obtain all information necessary to assess performance and stability of the aircraft. I have written a stability module in python, which I can easily used when I pass all necessary coefficients. As mentioned before, I try to minimize time per iteration of calculations, so running 1 analysis instead of 2 would be adventageus. Perhaps another take on this could be a performance-stability analysis? Analysis that could output aerodynamic coefficients for range of alpha angles and eigenvalues for each alpha would also be great! Possibly this could be a less niche feature request?
Cheers,
Szymon
techwinder Staff answered 4 years ago
Running T12 analyses for a set of velocity fields defined by aoa, sideslip and rotation rates is technically possible but requires some development work. I’ll probably implement the feature, but I can’t commit to a date because there are other things I need to improve before in flow5. It will probably be a matter of weeks, unless I run into some unforeseen technical difficulty.
I’ll post back when I have news.
André