FLUTTER CALCULATION BASED ON GVT-RESULTS AND THEORETICAL MASS MODEL

摘要

Da?numiniai bandymai ?em?je yra tipinis informacijos ?altinis flaterio skai?iavimui. ?iame straipsnyje pateikiamas paprastas ir pigus flateriornskai?iavimo metodas. ?iame metode naudojamos l?ktuvo i?matuot? da?numini? mod? formos ir teorinis l?ktuvo masi? modelis.rnNaudojant teorin? masi? model? galima apskai?iuoti apibendrintas mod? mases ir masi? ry?ius tarp j?. Normalini? mod? masi? ry?ys turi būti lygusrnnuliui. Ortogonalizavimu koreguojamos mod? formos, siekiant ry?ius suma?inti iki nulio. Galimi ortogonalizavimo metodai pateikti antrame skyriuje.rnRemiantis l?ktuvo laisv?j? svyravimo modomis, gautomis da?numini? bandym? ?em?je metu, galima nustatyti kitokio masi? pasiskirstymo ?tak?rnlaisv?j? svyravim? modoms. Procedūroje, pateiktoje tre?iame skyriuje, manoma, kad geometrin?s ir standumo savyb?s nesikei?ia.rn?i metodologija buvo panaudota savoje programin?je ?rangoje flateriui skai?iuoti, kuri? galima naudoti lengv? l?ktuv? ir sklandytuv? flateriornskai?iavimui.%Ground vibration tests (GVT) are a typical source of data for flutter prediction. In this paper, a simple, low-cost method to calculate flutter is presented. In this method, measured frequencies, mode shapes of an airplane are used and, additionally, the theoretical mass model of it.rnIf the theoretical mass model is used, it is possible to calculate generalized masses of modes and cross mass couplings between them. The mass couplings of normal modes should be zero. Orthogonalization is correction of the mode shapes to lead the couplings to zero. The possible orthogonalization methods are presented in chapter 2. Based on eigenmodes of airplane configuration during GVT, it is possible to determine the eigenmodes of the same free airplane after a relatively small mass change, i.e. for another mass distribution that was not investigated by GVT. In the procedure presented in chapter 3, it is assumed that geometric and stiffness properties do not change. The methodology was used in the own flutter calculation software that is useful for flutter prediction of light airplanes and sailplanes.