scholarly journals Hemodynamics and coil distribution with changing coil stiffness and length in intracranial aneurysms

2017 ◽  
Vol 10 (8) ◽  
pp. 797-801 ◽  
Author(s):  
Soichiro Fujimura ◽  
Hiroyuki Takao ◽  
Takashi Suzuki ◽  
Chihebeddine Dahmani ◽  
Toshihiro Ishibashi ◽  
...  
Keyword(s):  
Side Wall ◽  
Neck Region ◽  
Outer Side ◽  
The Finite Element Method ◽  
Effective Velocity ◽  
Velocity Reduction ◽  
Embolization Coil ◽  
Blood Inflow ◽  
Computational Fluid Dynamics Cfd ◽  
Embolic Coils

PurposeThe purpose of this study was to investigate hemodynamics and coil distribution with changing coil stiffness and length using the finite element method (FEM) and computational fluid dynamics (CFD) analysis.MethodsBasic side-wall and bifurcation type aneurysm models were used. Six types of coil models were generated by changing the coil stiffness and length, based on commercially available embolic coils. Coil embolization was simulated using FEM. CFD was performed to characterize the hemodynamics in the aneurysms after embolization. Coil distribution and velocity reduction in the aneurysms were evaluated.ResultsThe median value of radial coil distribution was shifted from the center to the outer side of the aneurysmal dome by changing coil stiffness: harder coils entered the outer side of the aneurysmal dome more easily. Short coils were more distributed at the neck region, since their small size made it easy for them to enter the tighter area. CFD results also indicated that velocity in the aneurysm was effectively reduced when the coils were more distributed at the neck region and the outer side of the aneurysmal dome because of the disturbance in blood inflow.ConclusionsIt is easier for coils to enter the outer side of the aneurysmal sphere when they are harder. If coils are short, they can enter tighter areas more easily. In addition, high coil density at the outer side of the aneurysmal dome and at the neck region is important to achieve effective velocity reduction.

Comparative research on the air pollutant prevention and thermal comfort for different types of ventilation

2020 ◽  
pp. 1420326X2092552
Author(s):  
Yang Zhang ◽  
Wenxuan Yu ◽  
Youli Li ◽  
Han Li
Keyword(s):  
Thermal Comfort ◽  
Cfd Simulation ◽  
Thermal Sensation ◽  
Side Wall ◽  
Air Pollutant ◽  
Indoor Thermal Comfort ◽  
Subjective Experiment ◽  
Different Types ◽  
Computational Fluid Dynamics Cfd ◽  
Indoor Comfort

In this article, a comparative study on the outdoor air pollutant prevention and indoor thermal comfort for different types of ventilation was carried out. Both objective experiment, subjective experiment and computational fluid dynamics (CFD) simulation were conducted to investigate the differences in air pollutant prevention and thermal comfort between four common ventilation methods, namely supplying on the ceiling and returning on the ceiling (SC-RC), supplying on the ceiling and returning on the side wall (SC-RSW), supplying on the side wall and returning on the ceiling (SSW-RC), and supplying on the side wall and returning on the side wall (SSW-RSW). Results show that SSW-RSW can provide the highest indoor air quality according to the indoor average PM2.5 concentration. Overall thermal sensation was introduced to evaluate the indoor comfort under the four ventilation methods. The voting results show that the indoor thermal comfort can be enhanced by 29–36% under SSW-RSW and SSW-RC. Therefore, SSW-RSW is more suitable for providing a healthy and comfortable indoor environment.

IMPROVEMENT OF THERMAL COMFORT INSIDE A MOSQUE BUILDING

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
Fawaz Ghaleb Noman ◽  
Nazri Kamsah ◽  
Haslinda Mohamed Kamar
Keyword(s):  
Thermal Comfort ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Side Wall ◽  
The West ◽  
Cfd Simulations ◽  
Interior Space ◽  
Flow Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

A combined natural ventilation and mechanical fans are commonly used to cool the interior space inside the mosques in Malaysia. This article presents a study on thermal comfort in the Al-Jawahir Mosque, located in Johor Bahru, Malaysia. The objective is to assess the thermal comfort inside the mosque under the present ventilation system by determining the Predicted Mean Vote (PMV) and the Predicted Percentage of Dissatisfied (PPD). These values were then compared to the limits stated in the ASHRAE Standard-55. It was found that the PMV varies from 1.68 to 2.26 while the PPD varies from 61% to 87%. These show that the condition inside the mosque is quite warm. Computational fluid dynamics (CFD) method was used to carry out flow simulations, to identify a suitable strategy to improve the thermal comfort inside the mosque. Results of CFD simulations show that installing four exhaust fans above the windows on the west-side wall of the mosque is the most effective strategy to improve the thermal comfort inside the mosque. Both the PMV and PPD values can potentially be reduced by more than 60%.

scholarly journals Research of the Design Feasibility of a 3-Wheel Electric Vehicle with a Simplified Control System

2020 ◽  
Vol 14 (1) ◽  
pp. 32-35
Author(s):  
Srđan Medić ◽  
Veljko Kondić ◽  
Tihomir Mihalić ◽  
Vedran Runje
Keyword(s):  
Control System ◽  
Electric Vehicle ◽  
Fem Analysis ◽  
Steering Wheel ◽  
Circular Path ◽  
Main Concern ◽  
The Finite Element Method ◽  
Vehicle Aerodynamics ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

The need for a simple, customised electric vehicle (EV) has inspired the research of the possibility to build a simple EV tailored for the specific needs of the buyer. This paper is focused on the concept of an EV with no conventional control mechanism. In this paper, a research of user needs, vehicle dynamics, vehicle aerodynamics, type of drive and batteries was carried out. EV aerodynamics characteristics were simulated by using the Computational Fluid Dynamics (CFD) software. The control system was designed in correlations with the maximal safe velocity and the radius of EV turning on a circular path. The stability of the EV, concerning the vehicle turning over and wheels slipping while driving in the curves, was the main concern of this paper. The steering wheel and brake pad were replaced with a control stick. Using the Finite Element Method (FEM) analysis, key parts of the construction were constructed.

Flow Physics Leading to System Instability in a Centrifugal Pump

1994 ◽  
Vol 116 (4) ◽  
pp. 612-620 ◽  
Author(s):  
A. M. Wo ◽  
J. P. Bons
Keyword(s):  
Centrifugal Pump ◽  
Flow Separation ◽  
Side Wall ◽  
Outer Side ◽  
Pump Operation ◽  
Design Performance ◽  
Flow Recirculation ◽  
Pumping System ◽  
Region Flow ◽  
Flow Features

The off-design performance in a centrifugal pump is investigated experimentally. The objective is to identify flow features that lead to the onset of surge as the fundamental pumping system instability. Results show that there are primarily two reasons for the onset of surge as the flow is reduced in the pump studied: (a) adverse flow in the tongue region, and (b) destabilizing effect of the pipe diffuser. The former is due to premature diffusion of the flow entering the tongue region, which is manifested by increased flow recirculation through the tongue/impeller gap and flow separation on the volute outer side-wall opposite the tongue. These effects in the tongue region flow coupled with the destabilizing behavior of the pipe diffuser lead to the eventual unstable pump operation.

Experimental and theoretical analyses of two-dimensional flows upstream of broad-crested weirs

2008 ◽  
Vol 35 (9) ◽  
pp. 975-986 ◽  
Author(s):  
M. Salih Kirkgoz ◽  
M. Sami Akoz ◽  
A. Alper Oner
Keyword(s):  
Cfd Simulation ◽  
Turbulence Models ◽  
Free Surface Flows ◽  
Velocity Fields ◽  
Numerical Results ◽  
Cfd Modeling ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd

Using the particle image velocimetry (PIV) technique, the laboratory experiments are conducted to measure the velocity fields of two-dimensional turbulent free surface flows upstream of rectangular and triangular broad-crested weirs. The experimental flow cases are analyzed theoretically by a computational fluid dynamics (CFD) modeling in which the finite element method is used to solve the governing equations. In the CFD simulation, the volume of fluid (VOF) method is used to compute the free surfaces of the flows. Using the standard k–ε and standard k–ω turbulence models, the numerical results for the velocity fields and flow profiles are compared with the experimental results for validation purposes. The computed results using k–ω turbulence model on compressed mesh systems are found in good agreement with measured data. The flow cases are also analyzed theoretically using the potential flow (PF) approach, and the numerical results for the velocity fields are compared with measurements.

Baroclinic waves in a rotating fluid subject to internal heating

1970 ◽  
Vol 268 (1186) ◽  
pp. 201-232 ◽  
Keyword(s):  
Axisymmetric Flow ◽  
Side Wall ◽  
The Body ◽  
Radial Dependence ◽  
Outer Side ◽  
Rotating Fluid ◽  
Baroclinic Waves ◽  
Heating And Cooling ◽  
Side Walls ◽  
Periodic Fluctuations

Free thermal convection in a vertical rotating fluid annulus subject to axisymmetric heating and cooling applied at the side-walls has been the subject of extensive previous studies, one of the principal findings of which is that four distinct types of flow are possible, each characteristic of definite ranges of impressed experimental conditions. Three of these flow types are characterized by departures from axial symmetry and arise when the basic axisymmetric flow is ‘ baroclinically unstable ’; they comprise ‘ baroclinic waves ’ of varying degrees of complexity (steady waves, waves subject to periodic fluctuations in form, amplitude and/or wavenumber (‘vacillation’) and waves subject to irregular non-periodic fluctuations). The present paper reports an experimental and theoretical study of effects associated with the introduction of heat throughout the body of the fluid (rather than via one of the side-walls) and removal via the inner side-wall, the outer side-wall, or both side-walls simultaneously. The experiments show that the principal characteristics of the flow are fairly insensitive to the radial dependence of heating and cooling (upon which, for example, the horizontal shear of the basic axisymmetric flow depends), thereby strengthening the basis of the application to large-scale geophysical and astrophysical systems of theoretical ideas stemming from the laboratory work. Just as previous experiments have shown that the presence of an inner wall does not preclude the occurrence of irregular baroclinic waves, one of the present experiments shows that the absence of an inner wall does not preclude the occurrence of steady baroclinic waves (thus refuting a certain conjecture which seems to have gained widespread acceptance among meteorologists). Determinations have been made of the general form of the flow pattern, top-surface flow velocities, total heat transfer and the transition between axisymmetric flow and baroclinic waves, and the results interpreted, where possible, in terms of theoretical ideas. The experiments provide striking support for a simple theoretical model that treats the jet stream associated with the baroclinic waves as a quasigeostrophic detached thermal boundary layer.

freezing out, adsorption and absorption. After concentrating, separation is achieved by classical methods such as gas chranatography (GC) or high pressure liquid chranatography (HPLC). Identification is based mainly on mass spectrometry, infra-red spectrometry and chrcmatographic data. 3. RESULTS The primary goal of these methods is to concentrate all volatile com­ pounds, mainly volatile organic compounds or VOCs, present. This mixture of VOCs, containing odorous ccmpcunds, next to a large majority of unodo-rous substance, then is analysed. This chemical analysis is based on the separation of these hundreds of compounds by gas chranatography, is hampe­ red by large amounts of water, which is always present in air, and which is also freezed out or adsorbed. The only way to escape more or less this difficulty is to use a rather apolar adsorbant, in casu Tenax GC or similar materials (e.g. Chranosorb 102) (5). A second limitation is the fact that no material will ever be capable of adsorbing all odorous com­ pounds completely, and permit to desorb then afterwards completely. For compounds with very low boiling point, e.g. hydrogen sulphide, strong ad-sorbants are necessary, while for odorants with high boiling point, e.g. skatol or the sesquiterpenes, thermal desorption is difficult with strong adsorbant s. So a compromise has to be accepted, or several complementa­ ry adsorbants have to be used. At this moment this compromise for concen­ trating all odorous substances is found in the adsorbant mentioned, kno­ wing that the most volatile compounds might escape partly. Many systems have been described and even carenercialised, but we use a home-built sy­ stem, which is schematically represented in figure 1 (6). On an outer side wall of the gas chromatograph (GC) an oven in which the Tenax-adsorp-tion-sampling tubes fit is constructed. Connections with pressurized he­ lium (transfer gas) is provided and their is a connection with a high tem­ perature resistant sixway valve, which replaces the normal GC-injector. During thermal desorption (position 1 in figure 1) the transfer gas, car­ rying desorbed volatiles, passes the sixway valve, a cold trap (stainless steel loop cold with liquid air) and enters the ambient air. The helium carrier gas is connected to the GC-column via the sixway valve. After the desorption stage which usually takes about 45 minutes, with a desorption oven temperature of 220°C for 30 minutes at least, the sixway valve is switched (position 2 in figure 1). At that moment transfer gas flows through the sixway valve directly into the ambient whereas the carrier gas passes the cold trap before entering the GC-column. The liquid air is removed from the cold trap and the latter is quickly heated by a high in­ tensity fload light. In this way condensed compounds are flash-evaporated and injected into the GC-system. Concentrating odorants by adsorption-desorption techniques produces a terribly complex mixture of VOCs, which is separated by gas chranato­ graphy. Fortunately this technique allows formidable separation power, but still then the result is not always sufficient far a clear-cut odour analysis. In figure 2 the GC-analysis is shown of an air sample in the neighbourhood of a rendering plant, showing a great number of VOCs; however almost all of them are hydrocarbons produced by cars and heating systems and sane other products, which do not contribute to the odour. Very small peaks of odorants are detected, which shows the difficult task of odour ana­ lysis with a general concentrating technique. Of course this analysis is far more relevant if emission gases are examined as is demonstrated in fi­ gure 3 (7). Part of these difficulties can be overcane if the odorants can

1986 ◽  
pp. 169-169
Keyword(s):  
Thermal Desorption ◽  
Boiling Point ◽  
Complex Mixture ◽  
Side Wall ◽  
Ambient Air ◽  
Cold Trap ◽  
Outer Side ◽  
Carrier Gas ◽  
Clear Cut ◽  
Almost All

SOFC Modeling at the Cell Scale Including Hydrogen and Carbon Monoxide as Electrochemically Active Fuels

2012 ◽  
Author(s):  
Martin Andersson ◽  
Maria Navasa ◽  
Jinliang Yuan ◽  
Bengt Sundén
Keyword(s):  
Carbon Monoxide ◽  
Current Density ◽  
Two Dimensions ◽  
The Finite Element Method ◽  
Internal Reforming ◽  
Electrochemically Active ◽  
Electrode Interface ◽  
Computational Fluid Dynamics Cfd ◽  
Ion Current Density ◽  
Fully Coupled

Fuel cells are promising for future energy systems, because they are energy efficient and able to use renewable fuels. A fully coupled computational fluid dynamics (CFD) approach based on the finite element method (with the software COMSOL Multiphysics) in two-dimensions is developed to describe an intermediate temperature solid oxide fuel cell (SOFC) single cell. Governing equations covering heat, gas-phase species, momentum, ion and electron transport are implemented and coupled to kinetics describing internal reforming and electrochemical reactions. Both hydrogen and carbon monoxide are considered as electrochemically active fuels within the anode. The activation polarization in the electrodes and the ohmic polarization due to ion transport in the YSZ material are found to be the major part of the potential losses. The activation polarization is the most significant and it is smaller within the cathode compared to the anode for this study. The ion current density and the activation polarization are the highest at the electrolyte-electrode interface and decrease rapidly within the electrodes as the distance from the interface increases. However, the ohmic polarization by ion transfer increases for the positions away from the interface. The addition of the electrochemical reaction with CO as fuel increases the current density. It is concluded that the temperature and current density are strongly integrated and when any of them is changed, the other follows, and the change is accelerated.

scholarly journals Surgical Experiences of Pediatric Cervical Bronchogenic Cysts: A Case Series of 6 Patients

2021 ◽  
pp. 014556132098219
Author(s):  
Yanzhen Li ◽  
Shengcai Wang ◽  
Jun Tai ◽  
Jie Zhang ◽  
Lejian He ◽  
...  
Keyword(s):  
Pediatric Patients ◽  
Bronchogenic Cyst ◽  
Case Series ◽  
Side Wall ◽  
Neck Region ◽  
Surgical Excision ◽  
Complete Resection ◽  
Congenital Disease ◽  
Surgical Experience ◽  
Bronchogenic Cysts

Objectives: Bronchogenic cyst is a rare congenital disease which occurs especially in the neck region. This report presents 6 cases of bronchogenic cysts and discusses the diagnosis and surgical experience of this anomaly. Methods: A retrospective study of 6 pediatric patients with cervical bronchogenic cysts treated in our hospital during 2016 to 2019 was performed. We recorded and analyzed the clinical data of the patients, including age, symptoms, imaging findings, surgical procedure, and complications. Results: All patients underwent surgical excision. The chondroid tissues were found at the base of cysts which clung to the trachea in 5 patients and completely removed by surgery without recurrence. One patient showed recurrence due to residual cartilage after the first surgery, and the second surgery was required to resect the remaining cartilage. During the surgery, the recurrent laryngeal nerve (RLN) detector was used, which confirmed that all the RLNs clung to the side wall of cysts. All cases were cured without complications. Conclusions: Although rare, bronchogenic cysts should be considered in the differential diagnosis of peritracheal masses in children. Complete resection of the bronchogenic cysts, including the cartilages at the base, is vital in preventing recurrence. The RLN must be protected during the surgery.

Drag Reduction of TVS Scooty using a Windshield for the Rider Comfort Improvement

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Sudhir Kumar Singh ◽  
B.P. Agrawal ◽  
Brahma Nand Agrawal ◽  
Kaushalendra Kumar Dubey ◽  
Sanjeev Kumar Sharma ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Neck Region ◽  
Vehicle Speed ◽  
Baseline Model ◽  
Wind Noise ◽  
Pressure Drag ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability ◽  
Two Wheeler ◽  
Rider Comfort

Rider comfort and safety has become an essential theme in the design of two-wheeler vehicles. Comfort incorporates wind noise, air pressure on the rider, visibility and the stability of the Scooty handle. Rider comfort and the potential aerodynamics concern have encouraged the current authors to carry out the Computational Fluid Dynamics (CFD) analysis of TVS pep+ Scooty. Numerical computations were carried out using the standard k-ε turbulence model to examine the aerodynamic force coefficients, pressure distribution, velocity vector and streamlines around the Scooty and rider. Simulations were done for a range of speed on an existing and redesigned model of Scooty with a different windshield height. The simulation result shows that there is a reduction in the coefficient of drag (Cd) from 1.58 (baseline model) to 0.95 (model 3) at a speed of 60kmph. The pressure contour reveals the inclusion of the windshield of height 130mm in the baseline model has diminished the pressure drag on the rider. Visual of velocity contour depicts that the velocity of the air decrease above the neck region with in-creasing windshield height at a vehicle speed 120kmph. This study reinforces the need of windshield height of 150mm in the baseline model to avoid unwanted aerodynamic benefits on the rider.

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