Investigation of Saccadic Eye Movement Effects on the Fluid Dynamic in the Anterior Chamber

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Omid Abouali ◽  
Amirreza Modareszadeh ◽  
Alireza Ghaffarieh ◽  
Jiyuan Tu
Keyword(s):  
Shear Stress ◽  
Flow Field ◽  
Anterior Chamber ◽  
Fluid Dynamic ◽  
Analytic Solutions ◽  
Navier Stokes ◽  
Corneal Endothelial Cells ◽  
Saccadic Movement ◽  
Energy Equations ◽  
Mesh Technique

The aqueous humor (AH) flow in the anterior chamber (AC) due to saccadic movements is investigated in this research. The continuity, Navier-Stokes and energy equations in 3D and unsteady forms are solved numerically and the saccadic motion was modeled by the dynamic mesh technique. Firstly, the numerical model was validated for the saccadic movement of a spherical cavity with analytic solutions and experimental data where excellent agreement was observed. Then, two types of periodic and realistic saccadic motions of the AC are simulated, whereby the flow field is computed for various saccade amplitudes and the results are reported for different times. The results show that the acting shear stress on the corneal endothelial cells from AH due to saccadic movements is much higher than that due to normal AH flow by buoyancy induced due to temperature gradient. This shear stress is higher on the central region of the cornea. The results also depict that eye saccade imposes a 3D complicated flow field in the AC consist of various vortex structures. Finally, the enchantment of heat transfer in the AC by AH mixing as a result of saccadic motion is investigated.

CFD in the Loop: Ensemble Kalman Filtering With Underwater Mobile Sensor Networks

2014 ◽  
Author(s):  
Axel Hackbarth ◽  
Edwin Kreuzer ◽  
Thorben Schröder
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Navier Stokes ◽  
Mobile Sensor ◽  
Dynamic Simulations ◽  
Navier Stokes Equations ◽  
Time Flow ◽  
Strong Current ◽  
Predictive Controller

In marine environments, sparse in-situ measurements can be used for the estimation of the fluid dynamic field. To make best use of a mobile sensor network in an environment whose dynamics can be described by the Navier-Stokes equations, we developed a framework for data assimilation with motion-constrained underwater vehicles, that takes the physical field properties into account while sampling. Our algorithm uses an ensemble Kalman filter that propagates hundreds of slightly varied coarse fluid dynamic simulations through time. Flow and scalar measurements from the mobile sensors are integrated into all ensemble members. We implemented a model predictive controller to calculate covariance minimizing paths from the estimated flow field and motion primitives of the vehicles, which are affected by a strong current. Thereby, we were able to indirectly track dynamically changing wall temperatures through measurements of flow field variables.

scholarly journals Numerical and Analytical Study of Fluid Dynamic Forces in Seals and Bearings

1988 ◽  
Vol 110 (3) ◽  
pp. 315-325 ◽  
Author(s):  
L. T. Tam ◽  
A. J. Przekwas ◽  
A. Muszynska ◽  
R. C. Hendricks ◽  
M. J. Braun ◽  
...  
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Circumferential Velocity ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Lumped Model ◽  
Destabilizing Factors ◽  
Recirculation Zones

A numerical model based on a transformed, conservative form of the three-dimensional Navier-Stokes equations and an analytical model based on “lumped” fluid parameters are presented and compared with studies of modeled rotor/bearing/seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a descrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three-dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity, while injection or preswirl in the direction of rotation significantly weakened these zones. A decrease in average circumferential velocity was related to an increase in the strength of the recirculation zones and thereby promoted stability. The influence of the axial flow was analyzed. The lumped model of fluid dynamic force based on the average circumferential velocity ratio (as opposed to the bearing/seal coefficient model) well described the obtained results for relatively large but limited ranges of parameters. This lumped model is extremely useful in rotor/bearing/seal system dynamic analysis and should be widely recommended. Fluid dynamic forces and leakage rates were calculated and compared with seal data where the working fluid was bromotrifluoromethane (CBrF3). The radial and tangential force predictions were in reasonable agreement with selected experimental data. Nonsynchronous perturbation provided meaningful information for system lumped parameter identification from numerical experiment data.

FLOW FIELD AND TOPOLOGICAL ANALYSIS OF HEMISPHERICAL PARACHUTE IN LOW ANGLES OF ATTACK

2010 ◽  
Vol 24 (15) ◽  
pp. 1707-1725 ◽  
Author(s):  
YIHUA CAO ◽  
QIANFU SONG ◽  
ZHUO WU ◽  
JOHN SHERIDAN
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Flow Field ◽  
Topological Structure ◽  
Topological Analysis ◽  
Fluid Simulation ◽  
Navier Stokes ◽  
Structure Interaction ◽  
Simplec Algorithm ◽  
Stable Shape

For analyzing the flow field and topological structure of hemispherical parachute in low angles of attack, a fluid-structure interaction (FSI) simulation technique is established to decide the shape of the hemispherical parachute during terminal descent. In the fluid simulation, the semi-implicit method for pressure-linked equations consistent (SIMPLEC) algorithm is introduced to solve shear stress transport (SST) k–ω turbulence Navier–Stokes (N–S) Equations. This method is proved to be efficient and stable by the experiment and corresponding numerical simulation. After obtaining the stable shape of the canopy, the parachute in different angles and velocities are considered.

CFD Analysis of Nano-Drug Transport in Vitreous Cavity due to Saccadic Eye Movements

2011 ◽  
Author(s):  
Amirreza Modareszadeh ◽  
Omid Abouali ◽  
Alireza Ghaffariyeh
Keyword(s):  
Drug Transport ◽  
Saccadic Eye Movements ◽  
Analytic Solutions ◽  
Vitreous Cavity ◽  
Navier Stokes ◽  
Human Eye ◽  
Real Model ◽  
Eye Motion ◽  
And Diffusion ◽  
Mesh Technique

In the present research, the motion of the nano-drug in the vitreous chamber of human eye due to saccadic movements in post-vitrectomy eyes is investigated. The average radius of the vitreous cavity in human eye is equal to 12 mm. This cavity is filled with a liquid in post-vitrectomy eyes. A dynamic mesh technique was performed to model the eye motion. The unsteady 3-D forms of continuity, Navier-Stokes and concentrations of nano-drug equations were solved numerically. The numerical model was validated comparing the results of the flow field with available analytic solutions and experimental data for a sphere as an ideal model of vitreous chamber which a very close agreement was achieved. Then, the numerical simulation was performed to a real model of vitreous cavity filled with BSS (Balanced salt solution). The convection and diffusion of nano-drug in the filling fluids of post-vitrectomy eyes is computed and the results are compared with the diffusion of the nano-drug in the stagnant vitreous. The comparison depicts that the saccade movements of human eye accelerate the drug motion one to two orders of magnitude higher than that due to diffusion in stagnant vitreous chamber.

Computational Prediction of Hemolysis by Blade Flow Field of Micro-Axial Blood Pump

2006 ◽  
Author(s):  
Xin Chen ◽  
Jianping Tan
Keyword(s):  
Blood Flow ◽  
Flow Field ◽  
Fluid Dynamic ◽  
Computational Prediction ◽  
Blood Pump ◽  
Navier Stokes ◽  
Initial Attempt ◽  
Navier Stokes Equation ◽  
Blood Damage ◽  
Blood Pumps

By analyzing fluid dynamics of blood in an artificial blood pump and simulating the flow field structure and the flow performance of blood, the blood flow and the damages in the designed blood pump would be better understood. This paper describes computational fluid dynamic (CFD) used in predicting numerically the hemolysis of blade in micro-axial blood pumps. A numerical hydrodynamical model, based on the Navier-Stokes equation, was used to obtain the flow in a micro-axial blood pump. A time-dependent stress acting on blood particle is solved in this paper to explore the blood flow and damages in the micro-axial blood pump. An initial attempt is also made to predict the blood damage from these simulations.

scholarly journals Multiple Solutions in Fluid Dynamics

2009 ◽  
Vol 14 (2) ◽  
pp. 263-279
Author(s):  
L.-S. Yao
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Reynolds Number ◽  
Flow Field ◽  
Multiple Solutions ◽  
Fluid Flows ◽  
Critical Value ◽  
Navier Stokes ◽  
Energy Equations

The principle of multiple solutions of the Navier-Stokes and energy equations discussed in this paper is not directed at any particular problems in fluid dynamics and heat transfer, or at any specific applications. The non-uniqueness principle states that the Reynolds number, above its critical value, is insufficient to uniquely determine a flow field for a given geometry, or for similar geometries. It is a generic principle for all fluid flows and its transportation properties, but is not well known. It compliments the current popular bifurcation theories by the fact that multiple solutions can exist on each stable bifurcation branch.

Computational Analysis of Two-Phase Mixing Inside a Twin-Fluid, Fuel-Flexible Atomizer

2017 ◽  
Author(s):  
Nathan J. Vardaman ◽  
Ajay K. Agrawal
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Fuel Injector ◽  
Cfd Model ◽  
Two Phase ◽  
Phase Mixing ◽  
Phase Mixture

We have developed a twin-fluid atomizer for combustion that creates a two-phase mixture of fuel and atomizing air upstream of the injector exit where a high-pressure region is established. The static pressure decreases rapidly as the fuel-air mixture exits from the injector, which causes air bubbles in the mixture to expand and breakup the surrounding liquid. This type of fuel injector can effectively atomize various biofuels including highly viscous straight vegetable oil and glycerol. While the combustion benefits have been demonstrated in our prior studies, an understanding of the underlying flow field and mechanism of the two-phase mixture formation process within the injector remains elusive. In this study, a computational fluid dynamic (CFD) model is developed to investigate the two-phase mixing and how it is affected by the operating conditions, particularly the atomizing air to liquid ratio (ALR) by mass. The axisymmetric isothermal CFD model, based on the mixture model for two-phase flows and Reynolds averaged Navier-Stokes equations, utilizes air and water as the working fluids. Both fluids are treated as incompressible, with constant fluid properties. The analysis reveals the flow field within the injector and successfully replicates the upstream penetration of the atomizing air into the liquid supply tube observed experimentally. The penetration depth increases with increase in the ALR, which again agrees with the experimental results.

scholarly journals Numerical and Experimental Study of the Flow Field Structure Evolution in the Circular Recess of Oil Cavity

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Feng Shen ◽  
Conglian Chen ◽  
Zhaomiao Liu
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Great Influence ◽  
Flow Region ◽  
Field Structure ◽  
Numerical Control ◽  
Navier Stokes ◽  
Structure Evolution ◽  
Finite Volume Approach

The laminar radial flow in the oil cavity of heavy-duty computer numerical control (CNC) machines is very complicated and has not been fully explored. Navier-Stokes equations have been applied through the whole flow region using finite volume approach to explore this complicated flow phenomenon, including the influences of the clearance height (h), inlet nozzle Reynolds number (Re), and geometrical aspect ratio (e) on flow behaviors. A fluid dynamic experiment has been conducted to study the flow structure by using particle image velocimetry (PIV). Numerical simulation results have been compared with the experimental results, finding a good agreement with the studied cases. The results suggest that there are complex vortices in the oil cavity. Flow field structure of the oil cavity largely depends onh, Re, ande. Re andehave a great influence on the size and amount of vortices, andhhas slight effects on the size of the vortices. The lengths of primary, secondary, and tertiary isolated vortices have a linear relationship withh. The lengths of the primary and secondary isolated vortices increase linearly with ascendingeaseis small. But when Re andeare large enough, the size of the three vortices decreases.

Numerical Investigation of Flow Field and Heat Transfer in Cross-Corrugated Ducts

1999 ◽  
Vol 121 (2) ◽  
pp. 314-321 ◽  
Author(s):  
H. Blomerius ◽  
C. Ho¨lsken ◽  
N. K. Mitra
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Critical Reynolds Number ◽  
Wave Length ◽  
Reynolds Numbers ◽  
Sine Wave ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Flow Oscillations ◽  
Energy Equations

Flow field and heat transfer in sine-wave crossed-corrugated ducts have been investigated by numerical solution of the Navier-Stokes and energy equations in the laminar and transitional flow regime between Re = 170 and 2000. The ratio of the corrugation wave length λ* to amplitude a* has been varied between 7 and 10. The angle of the corrugation of the neighboring plates has been kept fixed at 45 deg. Results show that the critical Reynolds number for self-sustained flow oscillations is about 240. For Reynolds numbers larger than 1000, the Nusselt number and the friction factor are nearly independent of the dimensionless wavelength. Computational results compare well with available experimental results.

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