scholarly journals A model for tear film dynamics during a realistic blink

2019 ◽  
Vol 2 (3) ◽  
pp. 21-27
Author(s):  
Kara Lee Maki ◽  
William Henshaw ◽  
Alex McManus ◽  
Richard Braun ◽  
Dylan Chapp ◽  
...  
Keyword(s):  
Ocular Surface ◽  
Tear Film ◽  
Grid Method ◽  
Theoretical Studies ◽  
Overset Grid ◽  
Overset Grid Method

Each time one blinks, a stable tear film (TF) must reestablish itself on the ocular surface to ensure the function and health of the eye. Although the formation of the TF has been extensively studied both experimentally and theoretically, the influence of the lid dynamics on the TF formation is still not fully understood. Experimental instrumentation does not yet have the capability to estimate the TF thickness in vivo over the entire front of the eye, especially near the lids during a blink, where the eyelashes obstruct the view of the ocular surface. Additionally, a realistic blinking eyeshaped domain presents challenges in approximating themotion of the TF in theoretical studies. In thiswork,we overcome these theoretical challenges by implementing a moving overset grid method to study the influence of the lid motion on the formation of TF.

Numerical simulation of an X-wing flapping wing MAV by means of a deforming overset grid method

2015 ◽  
Author(s):  
Shuanghou Deng ◽  
Tianhang Xiao ◽  
Mustafa Percin ◽  
Bas van Oudheusden ◽  
Hester Bijl ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Grid Method ◽  
Flapping Wing ◽  
Overset Grid ◽  
Overset Grid Method

Prediction of Slamming Loads on Catamaran Wetdeck Using CFD

2015 ◽  
Author(s):  
Ahmed Swidan ◽  
Giles Thomas ◽  
Dev Ranmuthugala ◽  
Irene Penesis ◽  
Walid Amin ◽  
...  
Keyword(s):  
Model Simulation ◽  
Three Dimensional ◽  
Grid Method ◽  
Computationally Efficient ◽  
Overset Grid ◽  
Force Magnitude ◽  
Overset Grid Method ◽  
Drop Tests ◽  
Transient Velocity ◽  
Transient Velocity Profile

Wetdeck slamming is one of the principal hydrodynamic loads acting on catamarans. CFD techniques are shown to successfully characterise wetdeck slamming loads, as validated through a series of controlled-speed drop tests on a three-dimensional catamaran hullform model. Simulation of water entry at constant speed by applying a fixed grid method was found to be more computationally efficient than applying an overset grid. However, the overset grid method for implementing the exact transient velocity profile resulted in better prediction of slam force magnitude. In addition the splitting force concurrent with wetdeck slam event was quantified to be 21% of the vertical slamming force.

An overset grid method for large eddy simulation of turbomachinery stages

2014 ◽  
Vol 274 ◽  
pp. 333-355 ◽  
Author(s):  
Gaofeng Wang ◽  
Florent Duchaine ◽  
Dimitrios Papadogiannis ◽  
Ignacio Duran ◽  
Stéphane Moreau ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Grid Method ◽  
Overset Grid ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Overset Grid Method

Utilization of Cold-Flow Numerical Simulation With Overset Grid Method in Development Process of Aeroengine Combustor

2010 ◽  
Author(s):  
Mitsumasa Makida ◽  
Naoki Nakamura ◽  
Osamu Nozaki
Keyword(s):  
Numerical Simulation ◽  
Development Process ◽  
Grid Method ◽  
Simulation Method ◽  
Simulation Methods ◽  
Overset Grid ◽  
Simulation Code ◽  
Screening Process ◽  
Cold Flow ◽  
Overset Grid Method

In the TechCLEAN project of JAXA, a combustor for a small aircraft engine has been developed. The combustor was tuned to show the behavior of the Rich-Lean combustion through combustion tests under atmospheric and practical conditions. In the development process of the combustor, numerical simulation methods were also utilized as analysis tools to accelerate the development of the combustor. To use in the screening process of the combustor design, we focused on cost-effective simulation methods and adopted the cold-flow RANS simulation code UPACS which has been developed in JAXA. And to simplify the treatment of calculation grids of the combustor with complicated configuration, we also utilized combination of the overset grid method with the attached multi-block grid method. This simulation method was applied to three phases in the combustor development process; first to the analysis of the combustor configuration to adjust the overall pressure loss, secondly to the analysis of flame stability, and thirdly to the tuning of air flow ratio to optimize emission characteristics of full annular combustors. Finally, the full annular combustor was successively tuned to reduce NOx emissions to 38.1% of the ICAO CAEP4 standard under ICAO LTO cycles, also sustaining basic performances as an aircraft combustor.

scholarly journals Role of ion channels in the functional response of conjunctival goblet cells to dry eye

2018 ◽  
Vol 315 (2) ◽  
pp. C236-C246 ◽  
Author(s):  
Donald G. Puro
Keyword(s):  
Ion Channels ◽  
Dry Eye ◽  
Ocular Surface ◽  
Adaptive Response ◽  
Tear Film ◽  
Goblet Cells ◽  
Cation Conductance ◽  
Conjunctival Goblet Cells

Optimal vision requires an ocular surface with a stable tear film whose many critical tasks include providing >70% of the eye’s refractive power. However, for millions, tear film instability produces uncomfortable sight-impairing dry eye. Despite the multitude of etiologies for dry eye, a universal hallmark is hyperosmolarity of the tear film. Presently, knowledge of how the ocular surface responds to hyperosmolarity remains incomplete with little understood about the role of ion channels. This bioelectric analysis focused on conjunctival goblet cells whose release of tear-stabilizing mucin is a key adaptive response to dry eye. In freshly excised rat conjunctiva, perforated-patch recordings demonstrated that a ≥10% rise in osmolarity triggers goblet cells to rapidly generate a ~15-mV hyperpolarization due to the oxidant-dependent activation of ATP-sensitive K+ (KATP) channels. High-resolution membrane capacitance measurements used to monitor exocytosis revealed that this hyperpolarization results in an approximately fourfold boost in exocytotic activity evoked by cholinergic input, which in vivo occurs via a neural reflex and depends chiefly on calcium influxing down its electro-gradient. We discovered that this adaptive response is transient. During 30–80 min of hyperosmolarity, development of a depolarizing nonspecific cation conductance fully counterbalances the KATP-driven hyperpolarization and thereby eliminates the exocytotic boost. We conclude that hyperosmotic-induced hyperpolarization is a previously unappreciated mechanism by which goblet cells respond to transient ocular dryness. Loss of this voltage increase during long-term dryness/hyperosmolarity may account for the clinical conundrum that goblet cells in chronically dry eyes can remain filled with mucin even though the tear film is hyperosmotic and mucin-deficient.

711 Assessment of Overset Grid Method for Flow around a Solid Body

2006 ◽  
Vol 2006.81 (0) ◽  
pp. _7-11_
Author(s):  
Kohei NOMURA ◽  
Takeo KAJISHIMA ◽  
Takashi OHTA
Keyword(s):  
Solid Body ◽  
Grid Method ◽  
Overset Grid ◽  
Overset Grid Method
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