File:XCPA portance linéaire du fuselage,Darling.png
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Summary[edit]
DescriptionXCPA portance linéaire du fuselage,Darling.png |
Français : Position du Centre de Portance Aérodynamique( ou XCPA) d'un corps ogivo-cylindrique (tête plate, hémisphérique, gothique tangente) |
Date | |
Source | HANDBOOK OF BLUNT-BODY AERODYNAMICS VOL. I, STATIC STABILITY, by J. A. Darling, AD-776-586, Naval Ordinance Laboratory, Silver Spring, MD, DEC 73, http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD776586&Location=U2&doc=GetTRDoc.pdf |
Author | J. A. Darling |
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https://creativecommons.org/publicdomain/mark/1.0/PDMCreative Commons Public Domain Mark 1.0falsefalse
Annotations InfoField | This image is annotated: View the annotations at Commons |
Il est facile de démontrer que le point d'application des forces de pression sur un hémisphère se situe au centre géométrique de cet hémisphère (qui est aussi le centre de la sphère complète). Cependant ce dernier calcul ne prend pas en compte :
--> un éventuel report de la portance de l'hémisphère sur la partie cylindrique qui le suit (un exemple d'un tel report est donné par le Xcp de la tête plate) ;
--> l'effet du jeu de pression sur le culot du corps ogivo-cylindrique.
De fait, comme on l'observe sur ce graphe, l'abscisse du point d'application de la portance normale de l'ogive hémisphérique vaut 0,40 (et non 0,5) pour les longueurs totales 1,5 et 3 calibres.
La pente générale des deux courbes peut être comprise comme l'influence de la longueur de la partie cylindrique sur le à 0° d'incidence.
D'après Darling, la rapide chute du entre les élancements 2 et 3 est due à la présence d'une bulle de séparation sur la surface supérieure (ou extrados) du cylindre en incidence.
La position du Centre de pression est ici comptée négativement en arrière de la pointe de l'ogive. Les positifs représentent donc des Centres de pression en avant de la pointe de l'ogive (cela n'arrive que pour l'ogive en tête plate).
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current | 11:48, 25 January 2021 | 906 × 564 (227 KB) | Bernard de Go Mars (talk | contribs) | Couleur de la marque orange dans la nomenclature. | |
21:13, 23 January 2021 | 906 × 564 (217 KB) | Bernard de Go Mars (talk | contribs) | Uploaded a work by J. A. Darling from HANDBOOK OF BLUNT-BODY AERODYNAMICS VOL. I, STATIC STABILITY, by J. A. Darling, AD-776-586, Naval Ordinance Laboratory, Silver Spring, MD, DEC 73, http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD776586&Location=U2&doc=GetTRDoc.pdf with UploadWizard |
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Vertical resolution | 37.78 dpc |