Computational fluid dynamics (CFD) simulation analysis on retinal gas cover rates using computational eye models

AbstractWe investigated the change in the retinal gas cover rates due to intraocular gas volume and positions using computational eye models and demonstrated the appropriate position after pars plana vitrectomy (PPV) with gas tamponade for rhegmatogenous retinal detachments (RRDs). Computational fluid dynamic (CFD) software was used to calculate the retinal wall wettability of a computational pseudophakic eye models using fluid analysis. The model utilized different gas volumes from 10 to 90%, in increments of 10% to the vitreous cavity in the supine, sitting, lateral, prone with closed eyes, and prone positions. Then, the gas cover rates of the retina were measured in each quadrant. When breaks are limited to the inferior retina anterior to the equator or multiple breaks are observed in two or more quadrants anterior to the equator, supine position maintained 100% gas cover rates in all breaks for the longest duration compared with other positions. When breaks are limited to either superior, nasal, or temporal retina, sitting, lower temporal, and lower nasal position were maintained at 100% gas cover rates for the longest duration, respectively. Our results may contribute to better surgical outcomes of RRDs and a reduction in the duration of the postoperative prone position.

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CFD Simulation of Airflow Organization in the Ship Accommodation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.711.91 ◽

2014 ◽

Vol 711 ◽

pp. 91-95

Author(s):

Kun Zhang ◽

Hai Xu Li ◽

Jin Ling Wang

Keyword(s):

Air Conditioning ◽

High Performance ◽

Cfd Simulation ◽

Simulation Analysis ◽

Fluid Dynamic ◽

Temperature Fields ◽

Design Stage ◽

Air Conditioning System ◽

Design And Optimization ◽

Airflow Distribution

Efficient ventilation and sound air current are significant to improve indoor air quality (IAQ) and control the contamination concentration. Healthy and comfort air conditioning will provide a strong guarantee for high-performance work. While limited by lots of conditions, the airflow distribution in room is very difficult to be revealed, so numerical simulation and analysis for airflow organization become more and more important during the design stage of ventilation and air conditioning system. In the paper a ship accommodation is taken as a model to do simulation analysis on the effect of different airflow organizations. On the basis of computational fluid dynamic (CFD) theory and methodology, the temperature fields, velocity fields and air age fields under different airflow organizations are gotten by means of Airpak3.1. All these search works will be helpful for the further design and optimization for the ventilation and air conditioning system of the ship accommodation.

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Numerical Investigation of Rotational Speed on Pump as Turbine for Microhydro Applications

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.833.11 ◽

2016 ◽

Vol 833 ◽

pp. 11-18

Author(s):

Mohd Azlan Ismail ◽

Al Khalid Othman ◽

Hushairi Zen

Keyword(s):

Flow Rate ◽

Rural Areas ◽

Rotational Speed ◽

Computer Aided Design ◽

Cfd Simulation ◽

Simulation Analysis ◽

Fluid Dynamic ◽

Pressure Head ◽

Performance Curve ◽

Convergence Criteria

Pump as Turbine (PAT) always has been a favourable solution to generate electricity in rural areas when there is a potential microhydro site. Such systems have lower capital cost, and they are easier to maintain than commercially-available microhydro turbines. Normally, PAT is designed to run at a rated rotational speed so it can directly couple with an induction generator in order to match the synchronous speed. In an actual scenario, the PAT’s rotational speed changes and fluctuates with respect to flow rate due to the absence of a hydraulic control mechanism. It is essential to understand how the PAT behaves under different rotational speeds in order to design good microhydro systems. The aim of this study was to conduct simulation analysis of the effect of rotational speed on PAT’s performance curve over a range of flow rates. ANSYS CFX software was used as the Computational Fluid Dynamic (CFD) simulation tool in this study. Three distinct flow domains was modelled by Computer Aided Design (CAD) software and assembled as the computational fluid domains. Mesh independence analysis and convergence criteria were set to ensure the accuracy of the model. The torque generated by the impeller was collected from the simulation data and presented in the PAT performance curve. It was observed that the pressure head and torque generated increased at higher rotational speeds, thus maintaining the efficiency value. The results showed that the efficiency of the PAT was maintained around 76.5% for rotational speeds between 1350 to 1650 RPM, but the best efficiency point shifted to lower flow rate for lower rotational speed. The outcomes of this study will be useful for turbomachinery researchers, microhydro users, and project engineers for predicting the PAT performance for designing microhydro systems.

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The Influence of Wind Effects on Architectural Buildings Heights in Iraqi Residential Buildings Based on Computational Fluid Dynamics Simulations

Journal of Construction in Developing Countries ◽

10.21315/jcdc2021.26.1.4 ◽

2021 ◽

Vol 26 (1) ◽

pp. 63-87

Author(s):

Ali Hussein Khan ◽

◽

Siti Sarah Herman ◽

Mohamad Fakri Zaky Jaafar ◽

◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Architectural Design ◽

Cfd Simulation ◽

Simulation Analysis ◽

Residential Buildings ◽

Wind Effects ◽

Computational Fluid Dynamics Simulations ◽

Computational Fluid Dynamics Cfd ◽

Dynamics Simulations

The gradient of height in buildings is the most common way to prepare a comfortable environment and to increase wind forces around the buildings. This study assessed various design choices that enable architectural buildings to have different heights using computational fluid dynamics (CFD) simulation to analyse wind conditions. Nonetheless, wind effects may create uncomfortable zones around high buildings and may be hazardous for pedestrians in open spaces. As such, this study looked into pedestrian level wind (PLW) to enhance the wind environment of buildings in Iraqi climate. Wind characteristics may create a range of disturbance levels that affect pedestrian areas. Iraqi residential buildings were taken as case study to quantitatively analyse the outdoor buildings at PLW, so as to generate some ideas and solutions between CFD simulation analysis and architectural design to yield an optimal model.

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Impeller Optimization in Crossflow Hydraulic Turbines

Water ◽

10.3390/w13030313 ◽

2021 ◽

Vol 13 (3) ◽

pp. 313

Author(s):

Marco Sinagra ◽

Calogero Picone ◽

Costanza Aricò ◽

Antonio Pantano ◽

Tullio Tucciarelli ◽

...

Keyword(s):

Cfd Simulation ◽

Fluid Dynamic ◽

Structural Safety ◽

3D Fem ◽

Good Efficiency ◽

Standard Material ◽

Variable Head ◽

Hydraulic Turbines ◽

Constructive Simplicity ◽

Mechanical Optimization

Crossflow turbines represent a valuable choice for energy recovery in aqueducts, due to their constructive simplicity and good efficiency under variable head jump conditions. Several experimental and numerical studies concerning the optimal design of crossflow hydraulic turbines have already been proposed, but all of them assume that structural safety is fully compatible with the sought after geometry. We show first, with reference to a specific study case, that the geometry of the most efficient impeller would lead shortly, using blades with a traditional circular profile made with standard material, to their mechanical failure. A methodology for fully coupled fluid dynamic and mechanical optimization of the blade cross-section is then proposed. The methodology assumes a linear variation of the curvature of the blade external surface, along with an iterative use of two-dimensional (2D) computational fluid dynamic (CFD) and 3D structural finite element method (FEM) simulations. The proposed methodology was applied to the design of a power recovery system (PRS) turbine already installed in an operating water transport network and was finally validated with a fully 3D CFD simulation coupled with a 3D FEM structural analysis of the entire impeller.

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Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

Applied Sciences ◽

10.3390/app11010032 ◽

2020 ◽

Vol 11 (1) ◽

pp. 32

Author(s):

Ciro Caliendo ◽

Gianluca Genovese ◽

Isidoro Russo

Keyword(s):

Natural Ventilation ◽

Fluid Dynamic ◽

Movement Time ◽

Radiant Heat ◽

Heat Fluxes ◽

Maximum Heat ◽

Road Tunnels ◽

Maximum Heat Release ◽

Computational Fluid Dynamics Cfd ◽

Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

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CFD Simulation of Solid Suspension for a Liquid–Solid Industrial Stirred Reactor

Applied Sciences ◽

10.3390/app11125705 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5705

Author(s):

Adrian Stuparu ◽

Romeo Susan-Resiga ◽

Alin Bosioc

Keyword(s):

Chemical Reaction ◽

Cfd Simulation ◽

Simulation Analysis ◽

Solid Phase ◽

Initial Conditions ◽

Chemical Reactor ◽

Liquid Mixtures ◽

Multiphase Model ◽

Chemical Product ◽

Two Phase

The present study examines the possibility of using an industrial stirred chemical reactor, originally employed for liquid–liquid mixtures, for operating with two-phase liquid–solid suspensions. It is critical when obtaining a high-quality chemical product that the solid phase remains suspended in the liquid phase long enough that the chemical reaction takes place. The impeller was designed for the preparation of a chemical product with a prescribed composition. The present study aims at finding, using a numerical simulation analysis, if the performance of the original impeller is suitable for obtaining a new chemical product with a different composition. The Eulerian multiphase model was employed along with the renormalization (RNG) k-ε turbulence model to simulate liquid–solid flow with a free surface in a stirred tank. A sliding-mesh approach was used to model the impeller rotation with the commercial CFD code, FLUENT. The results obtained underline that 25% to 40% of the solid phase is sedimented on the lower part of the reactor, depending on the initial conditions. It results that the impeller does not perform as needed; hence, the suspension time of the solid phase is not long enough for the chemical reaction to be properly completed.

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Computational fluid dynamics (CFD) simulation of flow in the rotary drum for pyrite bio-preoxidization

Chemical Engineering and Processing - Process Intensification ◽

10.1016/j.cep.2007.03.011 ◽

2008 ◽

Vol 47 (5) ◽

pp. 971-978 ◽

Cited By ~ 5

Author(s):

T. Liu ◽

X. Qi ◽

G. Su ◽

J. Jin ◽

W. Cong

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Cfd Simulation ◽

Computational Fluid Dynamics Cfd ◽

Rotary Drum

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Simulation of Hydraulic Cylinder Cushioning

Sustainability ◽

10.3390/su13020494 ◽

2021 ◽

Vol 13 (2) ◽

pp. 494

Author(s):

Antonio Algar ◽

Javier Freire ◽

Robert Castilla ◽

Esteban Codina

Keyword(s):

Dynamic Model ◽

Cfd Simulation ◽

Fluid Dynamic ◽

Computational Fluid Dynamic Simulation ◽

Hydraulic Cylinder ◽

Outlet Port ◽

Optimal Behavior ◽

Radial Movement ◽

Mechanical Shocks ◽

Radial Gap

The internal cushioning systems of hydraulic linear actuators avoid mechanical shocks at the end of their stroke. The design where the piston with perimeter grooves regulates the flow by standing in front of the outlet port has been investigated. First, a bond graph dynamic model has been developed, including the flow throughout the internal cushion design, characterized in detail by computational fluid-dynamic simulation. Following this, the radial movement of the piston and the fluid-dynamic coefficients, experimentally validated, are integrated into the dynamic model. The registered radial movement is in coherence with the significant drag force estimated in the CFD simulation, generated by the flow through the grooves, where the laminar flow regime predominates. Ultimately, the model aims to predict the behavior of the cushioning during the movement of the arm of an excavator. The analytical model developed predicts the performance of the cushioning system, in coherence with empirical results. There is an optimal behavior, highly influenced by the mechanical stress conditions of the system, subject to a compromise between an increasing section of the grooves and an optimization of the radial gap.

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Numerical Investigation for the Resin Filling Behavior during Ultraviolet Nanoimprint Lithography of Subwavelength Moth-Eye Nanostructure

Coatings ◽

10.3390/coatings11070799 ◽

2021 ◽

Vol 11 (7) ◽

pp. 799

Author(s):

Yuanchi Cui ◽

Xuewen Wang ◽

Chengpeng Zhang ◽

Jilai Wang ◽

Zhenyu Shi

Keyword(s):

Simulation Model ◽

Nanoimprint Lithography ◽

Cfd Simulation ◽

Boundary Slip ◽

Accurate Analysis ◽

Inlet Velocity ◽

Filling Height ◽

Proposed Model ◽

Good Consistency ◽

Computational Fluid Dynamics Cfd

Accurate analysis of the resin filling process into the mold cavity is necessary for the high-precision fabrication of moth-eye nanostructure using the ultraviolet nanoimprint lithography (UV-NIL) technique. In this research, a computational fluid dynamics (CFD) simulation model was proposed to reveal resin filling behavior, in which the effect of boundary slip was considered. By comparison with the experimental results, a good consistency was found, indicating that the simulation model could be used to analyze the resin filling behavior. Based on the proposed model, the effects of process parameters on resin filling behavior were analyzed, including resin viscosity, inlet velocity and resin thickness. It was found that the inlet velocity showed a more significant effect on filling height than the resin viscosity and thickness. Besides, the effects of boundary conditions on resin filling behavior were investigated, and it was found the boundary slip had a significant influence on resin filling behavior, and excellent filling results were obtained with a larger slip velocity on the mold side. This research could provide guidance for a more comprehensive understanding of the resin filling behavior during UV-NIL of subwavelength moth-eye nanostructure.

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