scholarly journals Wave-riding and wave-passing by ducklings in formation swimming

2021 ◽  
Vol 928 ◽  
Author(s):  
Zhi-Ming Yuan ◽  
Minglu Chen ◽  
Laibing Jia ◽  
Chunyan Ji ◽  
Atilla Incecik
Keyword(s):  
Dynamic Equilibrium ◽  
Wave Drag ◽  
Line Formation ◽  
Interference Phenomenon ◽  
The Third ◽  
Wave Interference ◽  
Single File ◽  
Mechanisms Of Formation ◽  
Wave Drag Reduction ◽  
The Waves

It has been commonly observed on open waters that ducklings/goslings follow their mothers in a highly organized formation. The questions arise: (1) why are they swimming in formation? (2) what is the best swimming formation? (3) how much energy can be preserved by each individual in formation swimming? To address these questions, we established a simplified mathematical and numerical model and calculated the wave drag on a group of waterfowl in a swimming formation. We observed two new and interesting findings: wave-riding and wave-passing. By riding the waves generated by a mother duck, a trailing duckling can obtain a significant wave-drag reduction. When a duckling swims at the ‘sweet point’ behind its mother, a destructive wave interference phenomenon occurs and the wave drag of the duckling turns positive, pushing the duckling forward. More interestingly, this wave-riding benefit could be sustained by the rest of the ducklings in a single-file line formation. Starting from the third one in a queue, the wave drag of individuals gradually tended towards zero, and a delicate dynamic equilibrium was achieved. Each individual under that equilibrium acted as a wave passer, passing the waves’ energy to its trailing one without any energy losses. Wave-riding and wave-passing are probably the principal reasons for the evolution of swimming formation by waterfowl. This study is the first to reveal the reasons why the formation movement of waterfowl can preserve individuals’ energy expenditure. Our calculations provide new insights into the mechanisms of formation swimming.

DYNAMICS OF COUNTER-FLOW INJECTION FOR WAVE DRAG REDUCTION

2018 ◽  
Author(s):  
Vishnu Prakash K ◽  
Siddesh Desai ◽  
Hrishikesh Gadgil ◽  
Vinayak Kulkarni
Keyword(s):  
Drag Reduction ◽  
Flow Injection ◽  
Wave Drag ◽  
Counter Flow ◽  
Wave Drag Reduction

Blunt-body wave drag reduction using focused energy deposition

AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 460-467 ◽  
Author(s):  
David Riggins ◽  
H. F. Nelson ◽  
Eric Johnson
Keyword(s):  
Drag Reduction ◽  
Energy Deposition ◽  
Blunt Body ◽  
Body Wave ◽  
Wave Drag ◽  
Wave Drag Reduction

A numerical study on the single pulsed energy addition based unsteady wave drag reduction at varied hypersonic flow regimes

2020 ◽  
pp. 095441002097313
Author(s):  
Dathi SNV Rajasekhar Rao ◽  
Bibin John
Keyword(s):  
Steady State ◽  
Mach Number ◽  
Drag Reduction ◽  
Shock Layer ◽  
Blunt Body ◽  
Wave Drag ◽  
Flow Features ◽  
Energy Pulse ◽  
Energy Addition ◽  
Wave Drag Reduction

In this study, unsteady wave drag reduction in hypersonic flowfield using pulsed energy addition is numerically investigated. A single energy pulse is considered to analyze the time-averaged drag reduction/pulse. The blast wave creation, translation and its interaction with shock layer are studied. As the wave drag depends only on the inviscid aspects of the flowfield, Euler part of a well-established compressible flow Navier-Stokes solver USHAS (Unstructured Solver for Hypersonic Aerothermodynamics) is employed for the present study. To explore the feasibility of pulsed energy addition in reducing the wave drag at different flight conditions, flight Mach numbers of 5.75, 6.9 and 8.0 are chosen for the study. An [Formula: see text] apex angle blunt cone model is considered to be placed in such hypersonic streams, and steady-state drag and unsteady drag reductions are computed. The simulation results indicate that drag of the blunt-body can be reduced below the steady-state drag for a significant period of energy bubble-shock layer interaction, and the corresponding propulsive energy savings can be up to 9%. For energy pulse of magnitude 100mJ deposited to a spherical region of 2 mm radius, located 50 mm upstream of the blunt-body offered a maximum percentage of wave drag reduction in the case of Mach 8.0 flowfield. Two different flow features are found to be responsible for the drag reduction, one is the low-density core of the blast wave and the second one is the baroclinic vortex created due to the plasma energy bubble-shock layer interaction. For the same freestream stagnation conditions, these two flow features are noted to be very predominant in the case of high Mach number flow in comparison to Mach 5.75 and 6.9 cases. However, the ratio of energy saved to the energy consumed is noted as a maximum for the lower Mach number case.

MEDIA FAKES IN THE INFORMATION SPACE OF THE CORONAVIRUS PANDEMIC

2021 ◽  
pp. 67-74
Author(s):  
A.G. Gurochkina ◽  
◽  
D.A. Makurova ◽  
Keyword(s):  
Social Media ◽  
Mass Media ◽  
Information Space ◽  
Fake News ◽  
Media Communication ◽  
Information Distortion ◽  
The Third ◽  
Mechanisms Of Formation

The paper explores the grave issue for modern-day research of mass media communication - fake news. The study aims at identifying cognitive bases and mechanisms of formation of media fakes about coronavirus. The first part of the article defines fake news and delineates salient characteristics of fake news. The second part of the article reveals some common semantic macrostructures of media fakes about the virus based on the analysis of social media posts and news articles. The third part of the article presents and describes the key strategies and tactics of manipulation and information distortion typical of fake news about the virus. The analysis reveals essential cognitive and pragmalinguistic components of coronavirus media fakes. The results of the undertaken research are relevant to further exploring other features of fake news and can be implemented as a guide for identifying fake news in order to reduce the mass addressee’s susceptibility to fakes.

Supersonic Bi-Directional Flying Wing Wave Drag Optimization Based on Alternative Form of CST Method

2013 ◽  
Vol 477-478 ◽  
pp. 240-245
Author(s):  
Xiaohui Guan
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Wave Drag ◽  
Alternative Form ◽  
Shape Transformation ◽  
Flat Bottom ◽  
Symmetric Configuration ◽  
Shape Parameterization ◽  
Wave Drag Reduction ◽  
Sufficient Precision

Bi-directional Flying Wing (BFW) is a new supersonic civil transport shape concept that aims to meet the conflict requirements of high speed cruise and low speed take-off/landing missions. In this paper the Class-Shape-Transformation (CST) shape parameterization method is modified to represent the BFW shape, and new basis functions suitable for the BFW airfoil representation are constructed. The Far-field Composite Element (FCE) wave drag optimization is performed on both the flat bottom and symmetric BFW configurations, and the drag reduction effects and result precision are surveyed. It is suggested that significant wave drag reduction can be achieved by the FCE optimization for both the flat bottom and the symmetric BFW configurations. The wave drag coefficients with sufficient precision can be obtained in the FCE optimization of the symmetric configuration; while the FCE optimization results of the flat bottom one are not accurate enough.

Dispersion relations of dust lattice waves in two-dimensional honeycomb configuration

2013 ◽  
Vol 79 (5) ◽  
pp. 629-633
Author(s):  
B. FAROKHI
Keyword(s):  
Dispersion Relation ◽  
Group Velocity ◽  
Hexagonal Lattice ◽  
Dispersion Relations ◽  
Two Dimensional ◽  
The Third ◽  
Lattice Waves ◽  
The Waves

AbstractThe linear dust lattice waves propagating in a two-dimensional honeycomb configuration is investigated. The interaction between particles is considered up to distance 2a, i.e. the third-neighbor interactions. Longitudinal and transverse (in-plane) dispersion relations are derived for waves in arbitrary directions. The study of dispersion relations with more neighbor interactions shows that in some cases the results change physically. Also, the dispersion relation in the different direction displays anisotropy of the group velocity in the lattice. The results are compared with dispersion relations of the waves in the hexagonal lattice.

Application of Ship-Wave Theory to the Hydrofoil of Finite Span

1957 ◽  
Vol 1 (02) ◽  
pp. 27-55
Author(s):  
John P. Breslin
Keyword(s):  
Wave Theory ◽  
Wave Pattern ◽  
Wave Drag ◽  
Test Results ◽  
Dimensional Theory ◽  
Ship Hydrodynamics ◽  
Finite Span ◽  
Induced Drag ◽  
Load Distributions ◽  
The Waves

It is demonstrated in this paper2 that the deepwater wave drag of a hydrofoil of finite span can be found directly from the theory developed largely for ship hydrodynamics by Havelock and others. The wave drag is then studied at high Froude numbers and from the observed behavior the induced drag of the hydrofoil can be deduced from existing aerodynamic formulas. Evaluation of the resulting formulas is effected for two arbitrary load distributions and a comparison with some model test results is made. A practical approximation which gives the influence of gravity over a range of high Froude numbers is found and from this one can deduce a Froude number beyond which the effects of gravity may be ignored. It is also shown that an expression for the waves at some distance aft of the hydrofoil can be deduced from the general formulas developed for ship hydrodynamics. A discussion of the wave pattern is given with particular emphasis on the centerline profile at high Froude numbers and a contrast is pointed out in regard to the results of the two-dimensional theory for the hydrofoil waves and wave resistance.

Wave drag reduction by means of aerospikes on transonic wings

Shock Waves ◽  
2009 ◽  
pp. 1309-1313 ◽  
Author(s):  
M. Rein ◽  
H. Rosemann ◽  
E. Schülein
Keyword(s):  
Drag Reduction ◽  
Wave Drag ◽  
Wave Drag Reduction

A Parting of the Waves

Worldview ◽  
1982 ◽  
Vol 25 (7) ◽  
pp. 11-12
Author(s):  
Ved P. Nanda
Keyword(s):  
The United States ◽  
Law Of The Sea ◽  
Manganese Nodules ◽  
Best Interest ◽  
Roll Call Vote ◽  
The Third ◽  
The Law ◽  
The Third World ◽  
The Waves ◽  
The U.S

When, on April 30. the United States rejected the Law of the Sea Convention, it dealt a blow to its own best interest: the orderly development of rules to govern navigation and exploitation of the oceans.During the last days of an eight-week session of the third United Nations conference on the Law of the Sea, the Third World majority had made a last-ditch effort to obtain U.S. approval of the treaty. The U.S. delegate, James Malone acknowledged that their concessions offered “modest improvements” but also that they failed to satisfy U.S. demands on the mining of highly valued manganese nodules. Whatever hope remained for a consensus on the draft treaty was shattered when the U.S. pressed for a forrnai roll call vote on the final day. Disappointment, frustration, and even shock was registered by many of the assembled delegates.

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