The deceleration effect of the deployable aerodynamic decelerator is not as good as a parachute in the subsonic region. This paper proposes a novel concept of using a parachute-like configuration (PLC) to enhance the deceleration performance of the mechanically deployable aerodynamic decelerator (MDAD) through structural transformation. The MDAD turned into the PLC from the sphere cone configuration (SCC) at Ma 0.8. The aerodynamic characteristics of the two configurations are analysed deeply. Compared to the SCC, the results show that the drag coefficient increases effectively, and the maximum increases is about 10% in the PLC. The airflow is altered by the MDAD configuration, which can affect the surface pressure and temperature. During the transformation process, the axial and normal force coefficients tend to stabilise. However, the static stability of the PLC deteriorates sharply compared to the SCC when the angle-of-attack exceeds 45°.

The energetic costs of animal movement change with body condition, although the consequences of this for foraging efficiency are rarely considered. We deployed externally attached devices to Magellanic penguins (Spheniscus magellanicus), known to increase the costs of swimming via increased drag in a consistent manner, and noted, however, that foraging behaviour and efficiency varied dramatically between years. We used our results to construct an energetics-based model and found that small increases in drag due to the attachment of externally attached tags predicted accelerating harm as prey availability decreased, which accorded with our observations. This explains earlier observations of differential breeding success in tagged versus untagged penguins in particular years, highlights the importance of understanding how animal body condition may affect population processes in general and advocates caution in interpretations of tag-derived data over variable environmental conditions.

The addition of wedge-like fairings onto the side of missiles and space launch vehicles, to shield devices such as cameras and reaction jet nozzles, creates additional drag, particularly when in supersonic and hypersonic freestream flow. An experimental and computational study was performed to obtain aerodynamic data on simple representative configurations to test the accuracy of simple theories for the drag increment due to these types of fairings. A semi-empirical method to estimate drag on wedge-shaped projections is presented, which may be used by missile designers to provide predictions of the drag increment due to wedge-like fairings. The method is shown to be valid where the wedge width is much smaller than body diameter, and across the Mach number range 4–8.2 but is likely to be valid for higher Mach numbers. Drag coefficient is found to increase with increasing wedge angle and reducing wedge slenderness, although increasing slenderness tends to increase skin friction drag.

Icing on aircraft can drastically reduce aerodynamic performance and lead to serious accidents. Therefore, prediction of the accreted ice shape and area and its effects on aerodynamic performance is crucial during the design phase of an aircraft. However, numerical simulations based on conventional grid-based methods such as the finite volume method cannot accurately reproduce the complex ice shapes, which involve horn growth, feather growth, air voids, and severe surface roughness. In the present study, instead of the grid-based method, a hybrid grid- and particle-based method was newly proposed and applied to the icing problem on a NACA0012 airfoil. The explicit moving particle semi-implicit method was employed as the particle-based method due to its short computing time. The numerical simulations effectively reproduced feather-shaped ice, air voids, and surface roughness. Finally, by computing the flow around the iced airfoil, it was confirmed that flow separation around the leading edge occurred due to the ice layer, which resulted in a thicker boundary layer and wake and an increase in the drag coefficient of approximately 70% after a residence time of only 60 seconds.

This article presents drag performance as a queer method of critique in the field of IR, which contributes to a longstanding move in IR to engage with aesthetics, and a more recent move to engage with performance art. The article discusses the author’s making of a performance piece that revisited the EU’s response to Hamas’s success in the 2006 Palestinian legislative elections. Soft, camp, feminine, and childlike voices; a female body in men’s clothing; and the translocation of bodies in spaces are used in the performance piece to disrupt the coherency of normalised diplomacy. Queer IR theory emphasises the imperative to dismantle logics of normality that prevent creativity in response to political issues. Performative drag practices disrupt anxious attachments to a ritualised discourse of strategic interests that shapes political initiatives. This article comments on other drag moments in politics, such as the anxiety around Jeremy Corbyn’s dress, Barack Obama’s anger translator, and Janelle Monáe’s androgynous articulation of community. The form that research dissemination takes implicates the kind of knowledge that is produced. This article reviews three methodological provocations of drag, an alternative departure point of the ‘what if’, performing a politics of refusal, and a Brechtian technique of estrangement.

In the present paper an experimental investigation of drag reduction on in-line tubebundles with a configuration of seven by seven with a pitch ratio of 1.44 has beenperformed. Two longitudinal grooves are placed on the external surface of the circularcylinders as a passive control. The experiment is carried out using a subsonic windtunnel. The pressure distributions for various azimuthal angles along the tubes aremeasured using a multi-channel differential pressure. Drag forces are also determinedusing a combined wire-strain gauge balance. The pressure drops are deduced from theresulting drag forces. The results obtained show an unexpected reduction in the pressuredrop for the tube bundles. A reduction of 36.5% in the pressure drop for a Reynolds numberof 1.33 × 104 is found compared to the configuration without grooves. Somecorrelations for the pressure drop are proposed.

We consider the effect of surface roughness on solid-solid contact in a Stokes flow.Various models for the roughness are considered, and a unified methodology is given toderive the corresponding asymptotics of the drag force in the close-contact limit. In thisway, we recover and clarify the various expressions that can be found in previousstudies.

Cet article traite du contrôle des décollements aérodynamiques pour réduire la consommation et les émissions de gaz à effet de serre des futurs véhicules automobiles. Après avoir passé en revue les moyens de contrôle passif, des exemples de contrôle actif par aspiration, soufflage ou par jet synthétique sont successivement présentés. Les résultats montrent le fort potentiel des solutions présentées. Des réductions de traînée proches de 20 % sont ainsi déjà envisagées sans que soit nécessaire de contraindre les géométries actuelles en termes d'habitabilité et de confort. Les coefficients de traînée aérodynamique des futurs véhicules automobiles destinés aux liaisons extra urbaines pourraient alors très prochainement tendre vers des valeurs voisines de 0,24. Cette évolution permettrait alors de réduire de 1,6 l sur 100 km la consommation moyenne d'un véhicule de moyenne gamme se déplaçant sur autoroute à la vitesse de 130 km.h-1. La réduction des émissions de gaz carbonique serait au moins de l'ordre de 7 g.km-1 suivant le cycle NEDC (New European Driving Cycle).

In this paper, the drag force on a sphere moving constantly along the centerline of a circular pipe filled with viscous fluid (the falling-sphere problem) under low Reynolds number condition is investigated via numerical calculation. The incompressible Navier-Stokes equations are formulated in a pseudocompressibility form. The numerical scheme makes use of finite-volume method and the numerical flux terms are evaluated using the Total-Variation Diminishing (TVD) strategy commonly applied to the compressible flow. Steady solution is obtained by marching (iterating) in time until the artificial time derivative of pressure term in the continuity equation drops to zero.

In the calculation, six different Reynolds number (Re) ranging from 0.1 to 1 and seven different pipe-to-sphere diameter ratios (D/d) ranging from 5 to 40 are selected to study the pipe-wall effect. In each case, the drag force on the sphere is evaluated and the results are compared with the existing approximate theoretical values derived from correcting the Stokes' formula. Both results agree in trend, but with noticeable deviation in values, particularly for cases with large pipe-to-sphere diameter ratios. The deviation is due to the fact that theoretical values were based on the solution to the linearized Navier-Stokes equations (Stokes' creeping-flow equations), while the fully nonlinear form of the Navier-Stokes equations are adopted in the present calculations. Finally, a least-square regression technique is applied to collapse the calculated results into a single expression exhibiting the functional relationship between the drag force, Reynolds number (Re), and the pipe-to-sphere diameter ratio (D/d).

L'objectif de cette étude est de minimiser, par rotationsinusoïdale, le coefficient de traînée moyen d'un cylindrecirculaire en régime laminaire. Une procédure d'optimisationcouplant modèle réduit par POD et méthode à région de confiance(TRPOD) est utilisée. Cette approche conduit à une réduction ducoefficient de traînée de 30 % pour un coût de calcul limité.

Some features of the dynamics of particles affected by drag, in the field of the Sun and planets, are presented here. In particular mean motion and secular resonances are investigated. When dust particles are considered as a whole in the zodiacal cloud, a simple secular theory can explain much of its geometry. Dynamics of particles near an inner planet is mostly dispersive, but an average behavior can be deduced from some analytical and numerical considerations.