The GlobalMode5 Vortex Coil. Fluid Flow in Spiral Vortex Structures

Essai Scientifique , 2023 , 22 Pages

Ingénierie - Généralités

This scientific article discusses the globalMode 5 Vortex Coil, more specifically the fluid flow in spiral vortex structures.

Fluid-mechanical vortex coils arise as spirally arranged coherent vortex filaments. One can assign physical properties to fluid-mechanical vortex coils, but formally there is no generally valid theory about spiral vortex formations in fluid mechanics. Theoretical key statements about vortex filaments have been known for a long time; the most important are from Helmholtz. A common feature of some modern theoretical approaches to ordered vortex configurations is that they designate coherent vortex formations as connected domains of dominant vortex strength.

For the phenomenology of "multiple (n) fluid-mechanical vortex coils" (global mode n vortex coil) presented here, Helmholtz's vortex filament theory, which is considered to be reliable, is first applied to Lagrangian coherent structures and expanded by an approach to the inner milieu of the vortex filaments. Structures of this kind form systems that are capable of momentum induction, which in turn organizes the field at rest. For the presence of well-grouped vortex filaments, there is a conjecture about the self-organization (autopoiesis) of vortex filaments in a flow field.

Table Of content

Spiral shape

Soaring bird in the wind tunnel

Corridor model

Communicating vortex filaments

Conclusion

Attachments

Spiral shape

The multiple, fluid-mechanical vortex coil remains a synthetic construct. Vortex coils are fluidic compositions of coherent vortex filaments with ascribed properties. The physical properties of the vortex filaments derive from their well- defined internal milieu. Spiral vortex formations occur in nature, but they are "made"! They are synthetic in the sense that generating systems exist that generate fluid-mechanical vortex coils.

So far, Lagrangian coherent vortex systems have not had a universal definition in fluid mechanics. This also applies to spiral systems. The first formulations of spiral rotationally coherent vortex systems came from observations of particular fingering of the wing tips of land-soaring birds. The descriptions of multiple vortex coil systems had no relation to the natural habitats of the birds, but were only arranged laboratory experiments in the wind tunnel; it was as if the decoding of bird flight had begun in a hall in the mid-1980s. At least that's how it was seen at the Department of Bionics and Evolutionary Technology at the Technical University of Berlin. Later, technical airfoil models were examined in the wind tunnel and their suitability for generating spiral vortex systems.

illustration not visible in this excerpt

Fig.1: Conditioning of the segmented tip contour of a model wing. Lift L and drag W were measured. After only 27 variation and selection campaigns, the synthetic wing resembles its biological model: the plumage of the land-soaring bird¹.

At the beginning of the investigations by Nachtigall (Saarbrücken) and Rechenberg (Berlin), little was known about the very special fluid mechanics of the vortex coil structures and the theory required for this. In Berlin, the first technical laboratory model of the fingered bird's wing was a splitted edge curve contour of a formerly compact model wing that was now slotted at the end of the wing. At that time, all experimenters in Berlin worked primarily with sheet metal (Fig.1), because lead surfaces offered certain creative freedom when constructing fingered model wings.

With an optimization strategy tailored to wind tunnel tests, the glide ratio (cL/cW)²of a slotted and fingered lead wing was improved by about 10% at the TU Berlin in the 1990s compared to its compact initial geometry. Only the preparation of the stork's wing behaved cheaper in the wind tunnel; with its exorbitantly low drag coefficient.

In the case of the lead wing model (Fig. 1), the partial wings or wing tips of the feather fingers form a curved chain of source points. For a long time, this arc­shaped arrangement of the source points was considered less productive for wake flow and momentum exchange there. In fact, the geometry of the vortex­generating system (ellipse or arc) has a great impact on the quality of the vortex­spiral system.

In the 1980s, winglets³entered the stage of research institutes and a short time later of the development departments of the aviation industry. Winglets are fixed partial wings on aircraft wings.

Let's briefly discuss which research questions and research results in the 1990s and 2000s advanced the development of aerodynamically approved wings that could actually be used commercially in civil aviation.

The work of Tucker (1993)⁴is fundamental to the study of the biological system. The ellipse configuration of biological fingers is not recognized here. The model investigations are carried out with geometries according to the arch configuration. Smith and Komerath⁵et al. publish 2001 results from wind tunnel tests in which the vortex cores of the multiple winglets form a chain (arc configuration). Entz and Correa⁶et al. find an improvement in lift/drag performance of 12% to 14% for the three-finger case over the closed tip arch on a model wing (arch configuration). A numerical analysis of the triple configuration is described by Thimmegowda⁷et al. Likewise, arc configurations are investigated by Sevillano⁸et al. for very small flight aggregates. The vortex system behind winglet configurations is studied by Zang, Wanng and Fu⁹. Executed constructions are examined by Ning and Kroo¹⁰and Merryisha and Rajendran¹¹, as well as by Scholz¹²for comparison. An experimental comparison between a single and a multi-winglet is made by Balagurumurugan et al¹³. A numerical model (Fluent) of a mono-winglet is described by Abdelghany et al¹⁴. Bird wing-inspired winglets (arc configuration) investigate Hossain, Rahman et al¹⁵. Also executed constructions examined Putro and Pitoyo, et al¹⁶. The last publication of an arc configuration from the Berlin department of bionics and evolutionary technology comes from Stache (2006)¹⁷. It therefore seems permissible to clarify the state of international science in the late 2010s with the arc configuration of the generator system. Recently, a study on biology-inspired multi-winglets by Yussof et al¹⁸. (2022) with a 7-fold fingering on the edge arch of a model wing, also in arch configuration.

To date, we only know the impulse effectiveness of spiral arrangements from the few vortex structures that have been experimentally investigated and measured in wind tunnels with precisely this question in mind. Also, we do not know whether the fluid mechanical effects are scalable or not. It can be observed that the impulse induction of Lagrangian coherent vortices in the flow field is cumulative and thus appears to be a conservative phenomenon. Compensations often occur in cumulative processes: physical effects cancel each other out. In this way, an inducing system can couple momentum into the field at the body-fixed, Lagrangen level without this production becoming visible at the Euler level.

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¹Based on illustrations from the pool of the department of bionics and evolutionary technology at the Technical University of Berlin; see also: Stache, M.: Evolutionsstrategisches Design von Tragflügelspitzen. DGLR- Jahrbuch, DGLR-2006-200, 2006, pp. 1131-1138

²Gleitzahl eines Tragflügels, Kennwert aus der Aeromechanik (Lilienthal-Beiwert) und berechnet aus gemessenem oder berechneten Widerstandskoeffizienten cW und dem Koeffizienten des fluiddynamischen Auftriebs CL (Lift). Im Falle des antriebslosen Gleitflugs eines Vogels oder eines (Flug-) Modells entspricht die Gleitzahl zugleich dem Verhältnis aus zurückgelegter Wegstrecke und Höhenverlust.

³Winglets (wörtlich: englisch Flügelchen) bzw. Sharklets (Bezeichnung für Winglets bei Airbus), deutsch Flügelohren[1], sind meistens nach oben und seltener nach oben und unten verlängerte Außenflügel an den Enden der Tragflächen von Luftfahrzeugen. Sie sorgen für eine bessere Seitenstabilität, verringern den induzierten Luftwiderstand und verbessern so den Gleitwinkel sowie die Steigzahl bei niedriger Geschwindigkeit. https://de.wikipedia.org/wiki/Winglet

⁴VANCE A. TUCKER (1993) GLIDING BIRDS: REDUCTION OF INDUCED DRAG BY WING

TIP SLOTS BETWEEN THE PRIMARY FEATHERS. J. exp. Biol. 180, 285-310 (1993)

⁵M. J. Smith·, N. Komerath+, R. Ames-, O. Wong-, (2001) PERFORMANCE ANALYSIS OF A WING WITH MULTIPLE WINGLETS; School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia and J. Pearson, Star Technology and Research, Inc., Mount Pleasant, South Carolina.

⁶Cosin, R. , Catalano, F.M. , Correa, L.G.N. , Entz, R.M.U. (2010) AERODYNAMIC ANALYSIS OF MULTI-WINGLETS FOR LOW SPEED AIRCRAFT Engineering School of Sao Carlos - University of Sao Paulo.

⁷Hariprasad Thimmegowda (2016) Computational and Experimental Analysis of Multi-Winglet at Low Subsonic Speed Conference Paper · August 2016

⁸A. A. Rodríguez Sevillano *, R. Bardera Mora **, M.A. Barcala Montejano*, E. Barroso Barderas ** and I. Díez Arancibia *. (2019) Design of Multiple Winglets for Enhancing Aerodynamics in a Micro Air Vehicle. 8TH EUROPEAN CONFERENCE FOR AERONAUTICS AND SPACE SCIENCES (EUCASS)

⁹Zang, Wang und Fu (2019) GENERATION MECHANISM AND REDUCTION METHOD OF INDUCED DRAG PRODUCED BY INTERACTING WINGTIP VORTEX SYSTEM. School of Aerospace Engineering Tsinghua University, Beijing, China

¹⁰Andrew Ning, Ilan Kroo (2010) Multidisciplinary Considerations in the Design of Wings and Wing Tip Devices. Brigham Young University - Provo, and Stanford University

¹¹Samuel Merryisha1, Parvathy Rajendran (2019) Review of Winglets on Tip Vortex, Drag and Airfoil Geometry School of Aerospace Engineering, Universiti Sains Malaysia, Engineering Campus. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 63, Issue 2 (2019) 218-237

¹²Scholz, D. (2018) Definition and discussion of the intrinsic efficiency of winglets, Aircraft Design and Systems Group (AERO), Hamburg University of Applied Sciences; Aerospace Europe CEAS 2017 Conference, 16th-20th October 2017, Palace of the Parliament, Bucharest, Romania, Technical session Aircraft and Spacecraft Design

¹³R. Balagurumurugan, A.Yadav, A. Ahmed R, S. Narayanan S (2016) Experimental study of single and multi­winglets. Article in Advances and Applications in Fluid Mechanics · April 2016.

¹⁴E. S. Abdelghany , E. E. Khalil, O. E. Abdellatif and G. ElHarriri (2016) WINGLET CANT AND SWEEP ANGLES EFFECT ON AIRCRAFT WING PERFORMANCE in Proceedings of the 17 MP 258 th Int. AMME Conference, 19-21 April, 2016

¹⁵Altab Hossain, Ataur Rahman, A.K.M. P. Iqbal, M. Ariffin, and M. Mazian (2011) Drag Analysis of an Aircraft Wing Model with and without Bird Feather like Winglet, World Academy of Science, Engineering and Technology, International Journal of Aerospace and Mechanical Engineering. Vol:5, No:9, 2011

¹⁶S H S Putro, B J Pitoyo, N Pambudiyatno, Sutardi, and W A Widodo (2020) Comparison of the winglet aerodynamic performance in unmanned aerial vehicle at low Reynolds number. IOP Conf. Series: Materials Science and Engineering 1173 (2021) 012002 2

¹⁷Stache, M.(2006): Evolutionsstrategisches Design von Tragflügelspitzen. DGLR- Jahrbuch, DGLR-2006-200, 2006, pp. 1131-1138.

¹⁸Hamid Yusoff, Koay Mei Hyie,*, Halim Ghaffar, Aliff Farhan Mohd Yamin, Muhammad Ridzwan Ramli, Wan Mazlina Wan Mohamed, Siti Nur Amalina Mohd Halidi (2022): The Evolution of Induced Drag of Multi-Winglets for Aerodynamic Performance of NACA23015, Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 93, Issue 2 (2022) 100-110.

• Auteur: Michel Felgenhauer (Auteur)
• Année de publication: 2023
• Pages: 22
• N° de catalogue: V1356563
• ISBN (PDF): 9783346874764
• ISBN (Livre): 9783346874771
• Langue: anglais
• mots-clé: globalmode5, vortex, coil, fluid, flow, spiral, structures