scholarly journals Naut Your Everyday Jellyfish Model: Exploring How Tentacles and Oral Arms Impact Locomotion

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 169 ◽  
Author(s):  
Jason G. Miles ◽  
Nicholas A. Battista
Keyword(s):  
Immersed Boundary Method ◽  
Energy Efficient ◽  
Swimming Performance ◽  
Vortex Formation ◽  
Fluid Mixing ◽  
Immersed Boundary ◽  
Number Density ◽  
Cost Of Transport ◽  
Fully Coupled ◽  
Interaction Problem

Jellyfish are majestic, energy-efficient, and one of the oldest species that inhabit the oceans. It is perhaps the second item, their efficiency, that has captivated scientists for decades into investigating their locomotive behavior. Yet, no one has specifically explored the role that their tentacles and oral arms may have on their potential swimming performance. We perform comparative in silico experiments to study how tentacle/oral arm number, length, placement, and density affect forward swimming speeds, cost of transport, and fluid mixing. An open source implementation of the immersed boundary method was used (IB2d) to solve the fully coupled fluid–structure interaction problem of an idealized flexible jellyfish bell with poroelastic tentacles/oral arms in a viscous, incompressible fluid. Overall tentacles/oral arms inhibit forward swimming speeds, by appearing to suppress vortex formation. Nonlinear relationships between length and fluid scale (Reynolds Number) as well as tentacle/oral arm number, density, and placement are observed, illustrating that small changes in morphology could result in significant decreases in swimming speeds, in some cases by upwards of 80–90% between cases with or without tentacles/oral arms.

scholarly journals Swimming Through Parameter Subspaces of a Simple Anguilliform Swimmer

2020 ◽  
Vol 60 (5) ◽  
pp. 1221-1235 ◽  
Author(s):  
Nicholas A Battista
Keyword(s):  
Immersed Boundary Method ◽  
Swimming Performance ◽  
Immersed Boundary ◽  
Cost Of Transport ◽  
Structure Interaction ◽  
Numerous Model ◽  
Robust Parameter ◽  
And Performance ◽  
The Cost ◽  
Fluid Interaction

Synopsis Computational scientists have investigated swimming performance across a multitude of different systems for decades. Most models depend on numerous model input parameters and performance is sensitive to those parameters. In this article, parameter subspaces are qualitatively identified in which there exists enhanced swimming performance for an idealized, simple swimming model that resembles a Caenorhabditis elegans, an organism that exhibits an anguilliform mode of locomotion. The computational model uses the immersed boundary method to solve the fluid-interaction system. The 1D swimmer propagates itself forward by dynamically changing its preferred body curvature. Observations indicate that the swimmer’s performance appears more sensitive to fluid scale and stroke frequency, rather than variations in the velocity and acceleration of either its upstroke or downstroke as a whole. Pareto-like optimal fronts were also identified within the data for the cost of transport and swimming speed. While this methodology allows one to locate robust parameter subspaces for desired performance in a straight-forward manner, it comes at the cost of simulating orders of magnitude more simulations than traditional fluid–structure interaction studies.

Pump or coast: the role of resonance and passive energy recapture in medusan swimming performance

2019 ◽  
Vol 863 ◽  
pp. 1031-1061 ◽  
Author(s):  
Alexander P. Hoover ◽  
Antonio J. Porras ◽  
Laura A. Miller
Keyword(s):  
Immersed Boundary Method ◽  
Significant Contribution ◽  
Swimming Performance ◽  
Three Dimensional ◽  
Vortex Rings ◽  
Immersed Boundary ◽  
Cost Of Transport ◽  
The Cost ◽  
Inertial Regime

Diverse organisms that swim and fly in the inertial regime use the flapping or pumping of flexible appendages and cavities to propel themselves through a fluid. It has long been postulated that the speed and efficiency of locomotion are optimized by oscillating these appendages at their frequency of free vibration. In jellyfish swimming, a significant contribution to locomotory efficiency has been attributed to the effects passive energy recapture, whereby the bell is passively propelled through the fluid through its interaction with stopping vortex rings formed during each expansion of the bell. In this paper, we investigate the interplay between resonance and passive energy recapture using a three-dimensional implementation of the immersed boundary method to solve the fluid–structure interaction of an elastic oblate jellyfish bell propelling itself through a viscous fluid. The motion is generated through a fixed duration application of active tension to the bell margin, which mimics the action of the coronal swimming muscles. The pulsing frequency is then varied by altering the length of time between the application of applied tension. We find that the swimming speed is maximized when the bell is driven at its resonant frequency. However, the cost of transport is maximized by driving the bell at lower frequencies whereby the jellyfish passively coasts between active contractions through its interaction with the stopping vortex ring. Furthermore, the thrust generated by passive energy recapture was found to be dependent on the elastic properties of the jellyfish bell.

Vortex Generation in Two Intracranial Aneurysms

2014 ◽  
Author(s):  
Hafez Asgharzadeh ◽  
Iman Borazjani ◽  
Jianping Xiang ◽  
Hui Meng
Keyword(s):  
Immersed Boundary Method ◽  
Time Scale ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Immersed Boundary ◽  
Parent Artery ◽  
Aneurysm Neck ◽  
Vortex Formation Time ◽  
Previous Hypothesis ◽  
Aneurysm Shape

Three-dimensional numerical simulations, using the sharp-interface immersed boundary method, are carried out to investigate the effect of aneurysm shape on the hemodynamics of intracranial aneurysm. In our previous work [1] only a single geometry of an aneurysm was tested, but here two three-dimensional geometries are tested by reconstruction from three-dimensional rotational angiography of a human subject [2]. The results support our previous hypothesis [1], i.e., when the vortex formation time scale at the parent artery is smaller than the transportation time scale across the aneurysm neck, the flow aneurysm dome is dominated by a dynamic, unsteady vortex formation.

scholarly journals Numerical Simulations of Particle Sedimentation Using the Immersed Boundary Method

2015 ◽  
Vol 18 (2) ◽  
pp. 380-416 ◽  
Author(s):  
Sudeshna Ghosh ◽  
John M. Stockie
Keyword(s):  
Immersed Boundary Method ◽  
Mass Density ◽  
Boussinesq Approximation ◽  
Solid Particles ◽  
Immersed Boundary ◽  
Particle Sedimentation ◽  
Numerical Studies ◽  
Boundary Method ◽  
Circular Particle ◽  
Interaction Problem

AbstractWe study the settling of solid particles in a viscous incompressible fluid contained within a two-dimensional channel, where the mass density of the particles is greater than that of the fluid. The fluid-structure interaction problem is simulated numerically using the immersed boundary method, where the added mass is incorporated using a Boussinesq approximation. Simulations are performed with a single circular particle, and also with two particles in various initial configurations. The terminal particle settling velocity and drag coefficient correspond closely with other theoretical, experimental and numerical results, and the particle trajectories reproduce the expected behavior qualitatively. In particular, simulations of a pair of interacting particles similar drafting-kissing-tumbling dynamics to that observed in other experimental and numerical studies.

Fully Coupled Large Eddy Simulation-Conjugate Heat Transfer Analysis of a Ribbed Cooling Passage Using the Immersed Boundary Method

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Tae Kyung Oh ◽  
Danesh K. Tafti ◽  
Krishnamurthy Nagendra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Conduction ◽  
Immersed Boundary Method ◽  
Conjugate Heat Transfer ◽  
Immersed Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Passage ◽  
Fully Coupled

Abstract The study focuses on evaluating fully coupled conjugate heat transfer (CHT) simulation in a ribbed cooling passage with a fully developed flow assumption using large eddy simulation (LES) with the immersed boundary method (IBM-LES-CHT). The IBM-LES and the IBM-CHT frameworks are validated by simulating purely convective heat transfer in the ribbed duct, and a laminar boundary layer flow over a 2D flat plate with heat conduction, respectively. For the main conjugate simulations, a ribbed duct geometry with a blockage ratio of 0.3 is simulated at a bulk Reynolds number of 10,000 with a conjugate boundary condition applied to the rib surface. The nominal Biot number is kept at 1, which is similar to the comparative experiment. It is shown that the time scale disparity between turbulent fluid flow and heat conduction in solid can be overcome by using an artificially high solid thermal diffusivity. While the diffusivity impacts the instantaneous fluctuations in temperature and heat transfer, it has an insignificant effect on the predicted Nusselt number. Comparison between IBM-LES-CHT and iso-flux heat transfer simulations shows that the iso-flux case predicts higher local Nusselt numbers at the back face of the rib. Furthermore, the local Nusselt number augmentation ratio (EF) predicted by IBM-LES-CHT is compared with experiment and another LES conjugate simulation. The present LES calculations predict higher EFs on the leading face of the rib and show a different trend at the trailing face when CHT is activated.

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