Structural Config Studies Question 1

[VN1981]

Hi,
I am looking for some pointers on how to get started estimating preliminary structural aspects while doing configuration studies. Without giving out too much about the project, we will be doing some config studies on a Flying Wing.

The aero folks will be playing around with Aspect Ratio, Airfoil shape etc. What I want is to determine is the impact of changes on weight, CG, Moment of Intertia and some prelim strength & deflection analysis (low fidelity values only i.e. no FEM usage or anything). Mostly the changes would be around Wing region.

Before I start off on my research, just wanted to post here to get some pointers. Are there any dedicated software programs available to carry out the above?

Also I would appreciate if experienced members could provide pointers on good reference materials & books. Thought I will start off with Roskam & Niu (Conceptual design book) but if there are better & more specific materials, it would be awesome.

Thanks...

 

[VEBill]

It sounds like you're embarking on a 'Parametric Design' study exercise.

 

[rb1957]

have you googled "flying wing design" ? There seem to be relevant youtube videos.

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

This might be useful...

OpenVSP (Vehicle Sketch Pad) is a geometry modeling tool for conceptual aircraft design. The software rapidly models aircraft configurations without expending the expertise required for traditional Computer Aided Design (CAD) packages. Further development of OpenVSP software will stimulate economic opportunity in aviation and aerospace.

An aircraft shape is the natural starting point for multidisciplinary analysis and optimization (MDAO). The outer mold lines and structural layout are the drivers for and interface between aerodynamics, structures, mass properties, and all the physics that impact a vehicle's performance. Parameterization facilitates design and optimization by reducing the problem dimensionality and improving descriptive expressiveness. The aerospace industry and designers in particular have long described aircraft geometry parametrically; familiar quantities such as aspect ratio, taper ratio, sweep angle, and thickness to chord construct a common vocabulary for aircraft shape. Vehicle Sketch Pad (VSP) is an aircraft geometry tool for rapid evaluation of advanced design concepts which was developed by NASA and is available to industry at large. A useful parametric geometry tool must not only depict the geometry, but it must translate the familiar description of an aircraft into a model which can be useful for engineering purposes such as CFD or FEA analysis.

OpenVSP example image

https://software.nasa.gov/featuredsoftware/openvsp

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[VN1981]

WKTaylor,
Recently, I came across OpenVSP software and although I am yet to dig deeper in to it, prelim investigation looked like it was falling short in some of our needs. Will take another stab at it again.

RB, we already have a base Flying Wing design ready and we need some methodology or tools to provide rapid estimate of the impact on structural aspects due to changes in AR, foil shape etc.

Thanks for the replies...will dig deeper in to Raymer and also Roskam.

 

[VN1981]

Folks,
From a structures POV, for a component like Wing, during parametric design study is it reasonable to assume that important metrics are wing deflection & stresses due to air loads bending does not exceed yield? Any other criterion that should be included during a very initial stages of config studies?

 

[rb1957]

"does not need to exceed yield" is an odd way to express "limiting stresses to yield". But this is still not the correct limit.

Under ultimate load stress can exceed yield. Under limit load there should be no "significant" permanent deformation … generally taken as limit stresses should not exceed yiled.

But these are static limits, you also have fatigue limits which are much less easy to define.

And then composite structures behave differently.

And you need practical manufacturing limits.

And, if you have fuel in the wings, lightning strike.

Many, many limits.

another day in paradise, or is paradise one day closer ?

 

[Sparweb]

I design by analysis, parametrically, from time to time. I've seen some structures designed by guessing that have overweight components attached to underweight components. It looks bad. Proportions of an aircraft are much the same. Make it "look" right first, then start checking with analysis to find the direction of the optimization trend.

My go-to software is Mathcad. Put in the measurements, dimensions, equations of flight and performance, offer a parameter a range of values, see where the results trend to. Plot it on graphs. You can make your preliminary analysis look a professional report.
If you can't afford that, try Smath Studio. If you have a budget, and keen grads from the right university, do it in MatLab.

Using your words, the "very initial stages of config studies" should be expressed in very direct and simple terms. Nuances lead the analysis astray. Details that are not shown in the references given above (like Niu's and Roskam's books) are not needed at that early stage.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[VEBill]

"...Mathcad. ...Plot it on graphs."

That's the 'Parametric Design' approach that I've see described decades ago. The outputs are functions of the inputs, obviously, but in very complicated relationships that flow through the auto-generated conceptual design.

Taken to extremes, when you're happy with the design you then click print. It actually works for trivially simple products such as custom cables (ref Pasternack & their auto-generated drawings and price quotes).

 

[WKTaylor]

Can we assume that You have the 'fundamental textbooks, papers, articles' library for design of tailless aircraft, like these...

Tailless Aircraft in Theory & Practice

http://rcadvisor.com/tailless-aircraft-theory-practice-book-review

https://www.aiaa.org/publications

lists MANY texts, documents/papers and articles regarding just about every aspect of 'Tailless' aircraft design/analysis



Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]