Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X24: Fluid Structure InteractionsLive
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Sponsoring Units: DFD Chair: Emilie Dressaire, University of California, Santa Barbara |
Friday, March 19, 2021 8:00AM - 8:12AM Live |
X24.00001: Flow past a confined array of rigid hairs Emilie Dressaire, Nathan Jones, Sri Savya Tanikella A variety of aquatic organisms use appendages covered with arrays of hairs to capture food, smell, and move the fluid around them. At the hair level, the flow is characterized by a low Reynolds number (Re), whose value controls the transport through the array. The array acts either as a rake forcing the fluid around at low Re or small hair spacing or as a sieve letting the fluid through at higher Re or large hair spacing. To develop sensors inspired by those biological systems, we study the influence of confinement on the flow regimes through the porous structure. We investigate the flow past an array of hairs in a rectangular channel, with a developed Poiseuille flow field. Through numerical simulations, we vary the geometry of the array, the flow rate through the channel, and the confinement. We show that the transition between the rake and sieve regimes depends on the geometry of the system. |
Friday, March 19, 2021 8:12AM - 8:24AM Live |
X24.00002: A lattice Boltzmann based reference map technique for fluid–structure interaction Yue Sun, Christopher Rycroft The lattice Boltzmann (LB) method is a widely-used simulation approach for fluids that uses a mesoscopic probabilistic view of particle motion to reassemble macroscopic fluid quantities. The LB method uses a fixed Eulerian grid, and is particularly effective for simulating fluid flows in complex geometries. Here we present an extension to the LB method to model fluid–structure interaction problems involving solids undergoing large deformation. We use the reference map technique to model the large solid deformation on the same fixed Eulerian grid used in LB, thereby providing a unified discretization scheme that greatly simplifies the coupling between the two phases. Examples of incompressible neo-Hookean solids immersed within a quasi-incompressible Navier–Stokes fluid show this method is flexible and robust in handling a range of fluid–structure interactions. The method is a favorable candidate for simulations of soft colloidal mixtures, eroding sediments, or interacting microswimmers. |
Friday, March 19, 2021 8:24AM - 8:36AM Live |
X24.00003: Airflow dynamics induced by insect-inspired anisotropic flapping wings Romeo Antier, Benjamin Thiria, Ramiro Godoy-Diana In this work, we address the problem of inhomegeneous deformable flapping wings as observed, for instance, in insects where the veins fix the elasticity of the wings and their anisotropy. The wing is modeled as a very thin membrane supported by two stiffening main axes: the first at the leading edge, hence modulating the bending of the wing, and a second transversal one that modulates the torsion of the wing. The deformation of the flapping wings is observed using high-speed video recording. Both flexural and torsional stiffnesses are varied independently by varying the angle alpha between the main stiffening axes. We show that the optimization of the coupling between bending and torsion modes in terms of aerodynamic force generation seems to be consistent with the quadrature modes coupling found in the literature. Additionally, we use PIV measurements of the flow around and behind wings to understand the underlying mechanisms responsible for the benefits of quadrature modes coupling. The role of the leading edge vortices and their formation dynamics are also highlighted. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X24.00004: Drag of the Insect-inspired Axisymmetric Body with the Small Length-to Diameter Ratio Svetlana V. Poroseva, Peter V Vorobieff
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Friday, March 19, 2021 8:48AM - 9:00AM Live |
X24.00005: Surface deformation and friction properties of free surface flows over a train of cylindrical ribs Francisco Martinez Carreaux, Matias Medina, Dayanna Parra We report experimental measures about the surface deformation and the friction factor of turbulent, subcritical & quasi-uniform flows facing an array of half-cylinders at the bottom of a horizontal flume. A train of undular jumps appears on the free surface, whose relative amplitude depends on both, the Froude (Fr) and Reynolds (Re) number. From this relationship, an interesting decreasing scaling emerges between this amplitude and the relative depth of the flow, involving a characteristic length-scale. This length scale suggests that the amplitude of the jumps is the result of a competition between the inertial and viscous forces of the flow. Surprisingly, the wavelength of this train of jumps does not depend on Re, nor the Fr number. The friction factor resulting from this study, follows a form similar to the classical Nikuradse's law. This coefficient it is also related with the amplitude of these jumps, suggesting that the deformations at the surface seems to contribute to the overall friction of the flow. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X24.00006: Elastic sheets in shear flows, from single sheet behavior to exfoliation process: an experimental study. Hugo PERRIN, Lorenzo Botto Graphene has attracted much attention as a candidate material for applications in a variety fields. However, the fabrication of graphene at industrial scale remains a challenge. One of the most promising techniques is so-called liquid-phase exfoliation: graphite is sheared in a liquid until layers of graphene detach. |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X24.00007: Fluid-structure interactions in a soft-walled Hele-Shaw cell Callum Cuttle, Satyajit Pramanik, Jian Hui Guan, Christopher W. MacMinn The interaction of viscous and interfacial flows with soft materials has recently attracted substantial interest from a variety of different perspectives. Here, we study these interactions in the context of a model problem: Flow in a deformable Hele-Shaw cell, where one wall is rigid and the other is soft. Combining experiments with mathematical modelling, we consider the coupling of flow and deformation as viscous fluid is injected into an initially empty cell. We then discuss the implications of these results for hydrodynamic instabilities such as viscous fingering. |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X24.00008: A Comparison of Unimorph and Bimorph Circular Piezoceramic Discs For Synthetic Jet Actuator Performance Baris Gungordu, Mark Jabbal, Atanas Popov Synthetic jet actuators have certain advantages for the full-scale implementation as a new generation active flow control device. They are compact in size and self-containing with no requirement for piping. Even though further research is required, they can potentially achieve high enough jet velocity to have full-scale application in the aerospace industry. Relatively low jet velocity is a limiting factor for a potential industrial application thus, the jet velocity should be increased to match the flight conditions and to provide effective flow control. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X24.00009: Body pitching and bobbing shape the aerodynamic force, power, and stability of wild silkmoths Usama Bin Sikandar, Brett R Aiello, Simon Sponberg Quasi-steady models of insect flight often prescribe constant body dynamics during a wingstroke. However, many insects experience large fluctuations in body kinematics even during a single wingstroke. Silkmoths use larger, slower wingstrokes more akin to some flapping robot designs than their cousin hawkmoths, which are common models for insect flight dynamics. Here, we test whether silkmoth's body pitch and vertical oscillations (time-periodic body angle, stroke-plane angle and body velocity) impact aerodynamic force production, power requirements, and flight stability. An analysis of digitized wing shapes and forward flight 3D kinematics from nine silkmoth species shows that body oscillation magnitude is strongly associated with flapping frequency and wing loading (p<0.05). We also find that body oscillations directly impact the wing angle of attack within a wingstroke. Incorporating body oscillations into a quasi-steady blade element model of silkmoth flight significantly impacts the wingstroke-averaged aerodynamic forces, reduces profile power, and increases body pitch stability. These results might have strong implications for the design of flapping-wing micro air vehicles (FW-MAVs) that require high stability and low power requirements all while maintaining agility. |
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