Bob’s Research Corner: Grid Def – More Twist

In this article, I will focus on the improved twisting utilizing the unfolding folded faces (UFF) algorithm discussed in the last BRC post. The new twisting limits for both the Onera M6 wing and the F-18C vertical tail will be shown. See “Bob’s Research Corner: Grid Def – Twist” for the previous twist limits.

onera-all-threeWithout the UFF algorithm, the maximum tip twist I could reach on the Onera M6 wing was 10.5 degrees. With the algorithm active, I can twist the wing tip 28 degrees before folding faces that can’t be unfolded. The image to the left shows the original grid (red), previous maximum twist (blue) and new maximum twist (green). That is almost a tripling of the previous maximum wing tip twist. The animation below shows the twisting of the wing over 25 time-steps. A comparison of the original (red) and deformed grid (green) at several zoom levels is presented in the slide-show below the animation.

For the F-18C vertical tail, the maximum tip twist without the UFF algorithm was only 1.15 degrees. Now I can twist the tail 40 degrees at the tip. I’d say that is much more than any real world simulation would require!! The image immediately below shows the original grid (red), original deformation (blue) and new maximum deflection (green). An animation of the vertical tail twisting over 25 time-steps is show below the imagse followed by a slide-show comparing the grids (original in red; deformed in green).f18-bend-v2-all

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Bob Tomaro

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