Investigation of helical strut attached vena cava filter hemodynamic performanc

Hemodynamic performance of the Celect Platinum vena cava filter and the revised forms of it with helical flow inducer strut were studied with computational fluid dynamic software Ansys Fluent 18. The central velocity and shear stress increased but overall flow disturbance has been observed minimal level. Central velocity increases to 9.72% with Celect filter, by the single helical flow inducer strut the rate reaches to 14.69%, and with doubled form it reaches to 19.73%. The filter surface shear rate increases to 8.29% with the single helical flow inducer strut and increases 13.31% with doubled attachment. Increased velocity and shear stress on the filter may eliminate short term thrombus build-up problems by breaking the big size particulates with the high shearing forces. The new struts may also contribute to the ability of the filter to capture smaller clots, as well as to dissolve them from being bigger. Shear stress in the vein wall increases approximately 6.63% with the filter placement. It raises to 8.06% and 9.45% with single and double helical flow inducer strut attachment. Increased vein wall shear may reduce the recirculation and clotting in the vein wall and it may prevent the accumulation of clots. The increased shear stress on the filter may cause the migration problem, design improvements can minimize this risk. Helical flow inducer strut attachment can cause efficacy increase, and the flow are normalized.

Numerical simulation of a fuel nozzle's spray

The aim of this thesis is to examine the boundary conditions that must be input into the computational fluid dynamic software, FLUENT in order to model spray. This can then be used to advance the current computational fluid dynamic models used to model an engine's combustor. This will save the industry time and money, in the design development stages. The parameters that were studied in this thesis included, changing the angle the spray is injected at and the Rosin-Rammler parameters: number of droplet diameters contained within the spray and the droplet diameters spread, determining the uniformity of the spread. The results found that it was possible to predict the Rosin-Rammler plot with a minor change of the Rosin-Rammler parameter, spread, q. It was also found that the initial assessments of the spray parameters provide reasonable trends in the axial and radial velocities.

Numerical simulation of a fuel nozzle's spray

The aim of this thesis is to examine the boundary conditions that must be input into the computational fluid dynamic software, FLUENT in order to model spray. This can then be used to advance the current computational fluid dynamic models used to model an engine's combustor. This will save the industry time and money, in the design development stages. The parameters that were studied in this thesis included, changing the angle the spray is injected at and the Rosin-Rammler parameters: number of droplet diameters contained within the spray and the droplet diameters spread, determining the uniformity of the spread. The results found that it was possible to predict the Rosin-Rammler plot with a minor change of the Rosin-Rammler parameter, spread, q. It was also found that the initial assessments of the spray parameters provide reasonable trends in the axial and radial velocities.

Assessment of Cascading Accidents of Frostbite, Fire, and Explosion Caused by Liquefied Natural Gas Leakage

Liquefied natural gas (LNG) leaks often lead to cascading accident disasters, including vapor cloud release, explosion, fire, and toxic gas release. The origin and evolution of each accidental disaster must be considered when assessing safety. This paper discusses the safety assessment project of an LNG gas storage station in Xuzhou, China. Multiple conceivable disasters due to the leakage of LNG storage tanks are simulated and analyzed using the computational fluid dynamic software FLACS. We studied different wind speeds interacting with the flammable vapor cloud area and creating frostbite in areas of low temperature. Diffusion simulations of vapor cloud explosion (VCE), thermal radiation, and the distribution of toxic substances were performed. The overpressure-impulse criterion was used to calculate the influence range of VCE. Heat flux, heat dose, and heat flux-heat dose criteria were used to calculate the safe distance for personnel in the event of fire. Based on the calculation results of the three latter criteria, this paper recommends using the heat flux criterion to evaluate fire accidents. The danger zone of each accident was compared. VCE accidents yielded the largest area.

Numerical Study of Viscous Fluid Flows in a Kenics Static Mixer

Since many years static mixers find usage in chemical, food, cosmetic and pharmaceutical industry. One of the most commonly used is the Kenics type static mixer. In a framework of the current work the CFD simulation for Kenics static mixer were performed. In food or cosmetic industry one must deal very often with non-Newtonian fluids. Therefore this work concerns the numerical study of non-Newtonian fluid flux in a kenics km static mixer with laminar flow using the Navier-Stocks equation governing the phenomenon and the pressure loss equation. This simulation was made using the computational fluid dynamic software (CFX 12.0). In this paper we studied the influence of the Reynolds number, the viscosity of the fluid, aspect ratio and the number of helical elements fixed on the pressure drop. It was found that the CFD results of pressure drop for non-Newtonian power law was similar to literature data (the correlation of C.D.GRACE 1971 and the numerical simulation of E.SAATDJIAN 2012).

Hydraulic Performance for Combined Weir-Gate Structure

Combined hydraulic structure play an important role in controlling flow in open channels. This study was based on experimental and numerical modeling investigations for combined hydraulic structure. For this purpose three physical models of combined sharp crested trapezoidal weir with bottom opening and one physical model of sharp crested trapezoidal weir separately were used and tested by running eight different flow rates over each model. In which three configurations of bottom opening were tested; the first configuration is a rectangular gate while other two configuration were trapezoidal with two different side slopes of (1V:4H) and (1V:2H). The water surface profiles passing through weir-gate system were measured for all thirty two runs of all models which show uniform flow at 2.11h from the upstream of weir. The commercial computational fluid dynamic software ANSYS CFX was used to simulate flow numerically. The verification of the numerical model was based on water surface profiles and discharge which showed acceptable agreement. Also, the results showed that discharge coefficient Cd varies from (0.52-0.58). Furthermore, it was shown that both models with trapezoidal gate pass a higher discharge of flow than the model with rectangular gate with average percentage increase of discharge (40.78% and 19.40%) for trapezoidal side slopes (1H:2V and 1H:4V) respectively. In addition, the combined system with milder trapezoidal side slopes of bottom opening had a better performance for discharging weir flow which is about 40% as compared with traditional one. Finally, the empirical equations for stage-discharge relationship were estimated for all models and discharge coefficients were estimated for all runs.

Computational Investigations in Rectangular Convergent and Divergent Ribbed Channels

Computational investigations on the rib turbulated flow inside a convergent and divergent rectangular channel with square ribs of different rib heights and different Reynolds numbers (Re=20,000, 40,000 and 60,000). The ribs were arranged in a staggered fashion between the upper and lower surfaces of the test section. Computational investigations are carried out using computational fluid dynamic software ANSYS Fluent 14.0. Suitable solver settings like turbulence models were identified from the literature and the boundary conditions for the simulations on a solution of independent grid. Computations were carried out for both convergent and divergent channels with 0 (smooth duct), 1.5, 3, 6, 9 and 12 mm rib heights, to identify the ribbed channel with optimal performance, assessed using a thermo hydraulic performance parameter. The convergent and divergent rectangular channels show higher Nu values than the standard correlation values.

Computational Fluid Dynamic Predictions on Effects of Screw Number on Performance of Single Blade Archimedes Screw Turbine

One of the alternative solutions to reduce the impact of electricity crisis in Aceh and other isolated areas in Indonesia is by the construction of small-scale hydro power plants that can work efficiently on the heads lower than 10 meters. One suitable type of turbine applied to the head below 10 meters is the Archimedes screw turbine. Due to the lack of information about the application of low head power plants, resulting in applications of this type of turbine is still less in Indonesia. This paper examined the appropriate turbine model. Before experimental turbine testing, turbines were designed theoretically first and then analyzed numerically. The flow velocity and pressure patterns within the turbine were analyzed using ANSYS CFD (Computational Fluid Dynamic) software under design conditions for 7, 9 and 11 screw numbers for single blade turbine. Based on the results of pressure analysis, speed and turbulent kinetic energy, it found that turbine performance using 11 blades is better among the three turbines. However, the highest average speed was obtained on the turbine using 7 screws, which maximum pressure obtained on a turbine 7 screws of 1406 Pa, on 9 screws on plane 1301 Pa and at 11 screws of 1175 Pa. Based on the results of the analysis, it showed that the smaller the distance between the channel and turbine blades, the results were more efficient due to the absence of wasted streams. Therefore, the flow pressure in the inlet position all directly leaded to the tip off the blade to produce a momentum.