scholarly journals A Computational Model for Tail Undulation and Fluid Transport in the Giant Larvacean

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 88
Author(s):  
Alexander P. Hoover ◽  
Joost Daniels ◽  
Janna C. Nawroth ◽  
Kakani Katija
Keyword(s):  
Computational Model ◽  
Material Properties ◽  
Deep Sea ◽  
Muscle Activation ◽  
Fluid Transport ◽  
Power Input ◽  
Flow Speed ◽  
Mesopelagic Zone ◽  
Integrative Study ◽  
Downstream Flow

Flexible propulsors are ubiquitous in aquatic and flying organisms and are of great interest for bioinspired engineering. However, many animal models, especially those found in the deep sea, remain inaccessible to direct observation in the laboratory. We address this challenge by conducting an integrative study of the giant larvacean, an invertebrate swimmer and “fluid pump” of the mesopelagic zone. We demonstrate a workflow involving deep sea robots, advanced imaging tools, and numerical modeling to assess the kinematics and resulting fluid transport of the larvacean’s beating tail. A computational model of the tail was developed to simulate the local fluid environment and the tail kinematics using embedded passive (elastic) and active (muscular) material properties. The model examines how varying the extent of muscular activation affects the resulting kinematics and fluid transport rates. We find that muscle activation in two-thirds of the tail’s length, which corresponds to the observed kinematics in giant larvaceans, generates a greater average downstream flow speed than other designs with the same power input. Our results suggest that the active and passive material properties of the larvacean tail are tuned to produce efficient fluid transport for swimming and feeding, as well as provide new insight into the role of flexibility in biological propulsors.

The estimation of metabolism in the mesopelagic zone: Disentangling deep-sea zooplankton respiration

2019 ◽  
Vol 178 ◽  
pp. 102163 ◽  
Author(s):  
Santiago Hernández-León ◽  
Susana Calles ◽  
María Luz Fernández de Puelles
Keyword(s):  
Deep Sea ◽  
Mesopelagic Zone

Numerical Simulation of Heat Transfer in a 3D Cavity-Receiver

2015 ◽  
Author(s):  
Parthasarathy Pandi ◽  
Patrick Le Clercq
Keyword(s):  
Material Properties ◽  
Measurement Data ◽  
Power Input ◽  
Momentum Equation ◽  
Process Models ◽  
Conductive Heat ◽  
Recirculating Flow ◽  
Radiative Power ◽  
Ceria Reduction ◽  
Energy Equations

The unsteady 3D fluid flow coupled to radiative, convective, and conductive heat transfers are computed within a cavity-receiver that was successfully tested experimentally. A Monte-Carlo radiation model is used in the fluid regions of the reactor with source terms outside the cavity’s window to account for the concentrated radiative power input. Darcy’s law for the viscous regime and the Forchheimer’s term for the inertial regime are used in the momentum equation to account for the pressure drop within the porous region (RPC). Two separate energy equations for the solid and for the fluid regions of the porous domain are solved in order to capture the non-equilibrium effects in that region. Rosseland diffusion approximation is used in the solid regions of the RPC domain. The material properties and boundary conditions were taken from published experimental measurements. The simulation results are compared to the measurement data collected during the pre-heating and the ceria reduction phases, which sum up to four different radiative power inputs. Results of the comparison are very good and constitute the verification that the numerical methods, physical sub-process models and material properties are adequately selected and implemented. An analysis regarding the heat balance, the recirculating flow and, the effect of dual-scale porosity is also presented.

Noninvasive In Vivo Characterization of Pediatric Human Spine: 3-D Finite Element Study

2011 ◽  
Author(s):  
Elizabeth S. Doughty ◽  
Nesrin Sarigul-Klijn
Keyword(s):  
Finite Element ◽  
Computational Model ◽  
Muscle Activation ◽  
Computational Models ◽  
Three Dimensional ◽  
Pediatric Spine ◽  
Element Analysis ◽  
Spine Stabilization ◽  
Surgical Tool

There are no full three-dimensional computational models of the pediatric spine to study the many diseases and disorders that afflict the immature spine using finite element analysis. To fully characterize the pediatric spine, we created a pediatric specific computational model of C1-L5 using noninvasive in vivo techniques to incorporate the differences between the adult and pediatric spines: un-fused vertebrae, lax ligaments, and higher water content in the intervertebral discs. Muscle follower loads were included in the model to simulate muscle activation for five muscles involved in spine stabilization. This paper is the first pediatric three-dimensional model developed to date. Due to a lack of experimental pediatric spinal studies, this 3-D computational model has the potential to become a surgical tool to ensure that the most appropriate technique is chosen for treating pediatric spinal dysfunctions such as congenital abnormalities, idiopathic scoliosis, and vertebral fractures.

A parametric survey of the first critical Mach number for a fast MHD shock

1984 ◽  
Vol 32 (3) ◽  
pp. 429-441 ◽  
Author(s):  
J. P. Edmiston ◽  
C. F. Kennel
Keyword(s):  
Mach Number ◽  
Flow Speed ◽  
Interplanetary Shocks ◽  
Plasma Parameters ◽  
Energetic Ions ◽  
Critical Mach Number ◽  
Specific Heats ◽  
Solar Wind Parameters ◽  
The One ◽  
Downstream Flow

The first critical fast Mach number is rigorously defined to be the one at which the downstream flow speed in the shock frame equals the ordinary downstream sound speed. Above the first critical Mach number, resistivity alone is unable to provide all the dissipation needed for the required Rankine-Hugoniot shock jump. A survey of the dependence of the first critical Mach number upon upstream plasma parameters is needed to guide studies of the structure of collisionless shocks in space. We vary the upstream plasma beta, the upstream shock normal angle, and the ratio of specific heats for the plasma. The first critical Mach number depends sensitively upon upstream plasma parameters, and is between 1 and 2 for typical solar wind parameters, rather than the often quoted value of 2·7, which is valid for perpendicular shocks propagating into a cold plasma. We introduce the suggestion that the flux of superthermal and energetic ions upstream at quasi-parallel shocks might increase suddenly at the first critical Mach number. Our parametric survey indicates that this hypothesis might be most conveniently tested using interplanetary shocks.

scholarly journals Retinal Morphology and Visual Specializations in Three Species of Chimaeras, the Deep-Sea R. pacifica and C. lignaria, and the Vertical Migrator C. milii (Holocephali)

2018 ◽  
Vol 92 (1-2) ◽  
pp. 47-62 ◽  
Author(s):  
Eduardo Garza-Gisholt ◽  
Nathan S. Hart ◽  
Shaun P. Collin
Keyword(s):  
Color Vision ◽  
Deep Sea ◽  
Visual Information ◽  
Ganglion Cells ◽  
Deep Ocean ◽  
Visual Sensitivity ◽  
Segment Length ◽  
Lower Sensitivity ◽  
Elephant Shark ◽  
Mesopelagic Zone

The majority of holocephalans live in the mesopelagic zone of the deep ocean, where there is little or no sunlight, but some species migrate to brightly lit shallow waters to reproduce. This study compares the retinal morphology of two species of deep-sea chimaeras, the Pacific spookfish (Rhinochimaera pacifica) and the Carpenter’s chimaera (Chimaera lignaria), with the elephant shark (Callorhinchus milii), a vertical migrator that lives in the mesopelagic zone but migrates to shallow water to reproduce. The two deep-sea chimaera species possess pure rod retinae with long photoreceptor outer segments that might serve to increase visual sensitivity. In contrast, the retina of the elephant shark possesses rods, with an outer-segment length significantly shorter (a mean of 34 µm) than in the deep-sea species, and cones, and therefore the potential for color vision. The retinal ganglion cell distribution closely follows that of the photoreceptor populations in all three species, but there is a lower peak density of these cells in both deep-sea species (215–275 cells/mm2 vs. 769 cells/mm2 in the elephant shark), which represents a significant increase in the convergence of visual information (summation ratio) from photoreceptors to ganglion cells. It is evident that the eyes of deep-sea chimaeras have increased sensitivity to detect objects under low levels of light, but at the expense of both resolution and the capacity for color vision. In contrast, the elephant shark has a lower sensitivity, but the potential for color discrimination and a higher visual acuity.

scholarly journals Effects of airway tree asymmetry on the emergence and spatial persistence of ventilation defects

2014 ◽  
Vol 117 (4) ◽  
pp. 353-362 ◽  
Author(s):  
D. Leary ◽  
T. Winkler ◽  
A. Braune ◽  
G. N. Maksym
Keyword(s):  
Computational Model ◽  
Muscle Activation ◽  
Bronchial Tree ◽  
Ventilation Distribution ◽  
Self Organized ◽  
Positron Emission ◽  
Airway Tree ◽  
Poor Ventilation ◽  
Different Levels ◽  
Symmetric Tree

Asymmetry and heterogeneity in the branching of the human bronchial tree are well documented, but their effects on bronchoconstriction and ventilation distribution in asthma are unclear. In a series of seminal studies, Venegas et al. have shown that bronchoconstriction may lead to self-organized patterns of patchy ventilation in a computational model that could explain areas of poor ventilation [ventilation defects (VDefs)] observed in positron emission tomography images during induced bronchoconstriction. To investigate effects of anatomic asymmetry on the emergence of VDefs we used the symmetric tree computational model that Venegas and Winkler developed using different trees, including an anatomic human airway tree provided by M. Tawhai (University of Auckland), a symmetric tree, and three trees with intermediate asymmetry (Venegas JG, Winkler T, Musch G, Vidal Melo MF, Layfield D, Tgavalekos N, Fischman AJ, Callahan RJ, Bellani G, Harris RS. Nature 434: 777–782, 2005 and Winkler T, Venegas JG. J Appl Physiol 103: 655–663, 2007). Ventilation patterns, lung resistance (RL), lung elastance (EL), and the entropy of the ventilation distribution were compared at different levels of airway smooth muscle activation. We found VDefs emerging in both symmetric and asymmetric trees, but VDef locations were largely persistent in asymmetric trees, and bronchoconstriction reached steady state sooner than in a symmetric tree. Interestingly, bronchoconstriction in the asymmetric tree resulted in lower RL (∼%50) and greater EL (∼%25). We found that VDefs were universally caused by airway instability, but asymmetry in airway branching led to local triggers for the self-organized patchiness in ventilation and resulted in persistent locations of VDefs. These findings help to explain the emergence and the persistence in location of VDefs found in imaging studies.

scholarly journals Effects of deep diving on the trachea of the leatherback turtle

2010 ◽  
pp. 119-124
Author(s):  
Colm Murphy
Keyword(s):  
Material Properties ◽  
Deep Sea ◽  
Complete Understanding ◽  
Leatherback Turtles ◽  
Leatherback Turtle ◽  
Deep Dive ◽  
Deep Diving ◽  
Leading Role ◽  
Term Objective

This work is concerned with the effects of deep sea diving on the trachea (airway passage) of the leatherback turtle. Leatherback turtles are capable of diving to depths greater than 1,200 meters. Humans, in comparison, may only reach depths of around 30 meters unaided. It is believed that the response of the trachea along with its material properties plays a leading role in determining the depth that can be attained during a dive. The long term objective of this research is to investigate the response of the trachea of the leatherback turtle during deep dives (300-1250m). Questions remain as to the material properties from which the trachea is composed of and how exactly does the trachea respond as it undergoes a deep dive. Answering these questions will help not only to build a complete understanding of the leatherback’s ability to dive to depths greater than 1,000m, but will also inform ...

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