Validation of a Time Dependent Physio-Chemical Model for Thrombus Formation and Growth

2016 ◽  
Author(s):  
Hamid Hosseinzadegan ◽  
Danesh K. Tafti
Keyword(s):  
Growth Rate ◽  
Continuum Model ◽  
Thrombus Formation ◽  
Three Dimensional ◽  
Large Species ◽  
Flow Conditions ◽  
Numerical Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Acceptable Agreement ◽  
Three Dimensional Simulations

In this study, a shear-dependent continuum model for platelet activation, adhesion and aggregation is validated using computational fluid dynamics (CFD). To take the presence of red cells into account, a combination of excess-platelet boundary layer and enhanced mass diffusivity of platelets and large species is used to mimic this behavior. The model has been validated under three different shear conditions and two different heparin levels. Also three-dimensional simulations were carried out to evaluate the model’s prediction of thrombus growth rate for stenosed tubes under various flow conditions and stenosis degrees. For these cases, also the effect of change in platelet diffusivity has been investigated by using an empirical correlation for enhanced diffusivity of platelets. For all 3D simulations, results for thrombus growth rate as a function of local wall shear rate were compared to those of experiments and numerical studies in the literature and an acceptable agreement was achieved.

scholarly journals Numerical Studies on Temperature and Material Flow During Friction Stir Welding using Different Tool Pin Profiles

2021 ◽  
Vol 83 (1) ◽  
pp. 91-104
Author(s):  
M. D. Bindu ◽  
P. S. Tide ◽  
A. B. Bhasi
Keyword(s):  
Friction Stir Welding ◽  
Temperature Distribution ◽  
Material Flow ◽  
Three Dimensional ◽  
Friction Stir ◽  
Specific Strength ◽  
Numerical Studies ◽  
Computational Fluid Dynamics Cfd ◽  
Tool Pin ◽  
Metal Hardness

A three dimensional computational fluid dynamics (CFD) model has been developed to study the effect of tool pin profile on the material flow and temperature development in friction stir welding (FSW) of high specific strength AA 7068 alloy. Numerical simulations were carried out using a RNG k-e turbulence model. Three tool pin profiles, viz. cylindrical, conical and straight cylindrical threaded were considered for the simulation. The temperature distribution and material flow pattern obtained from the simulation were compared for different pin profiles. Simulation results predicted Temperature distribution and material maxing was better in straight cylindrical tapered thread pin welds. Weld joints were fabricated using the straight cylindrical threaded pin with the same parametric combinations as in the simulation. Peak temperature measured in the experiment was less than that obtained by simulation. Hardness measurements taken at different weld regions has showed that about 71% of that of the base metal hardness is obtained with the threaded tool pin. The microstructure study revealed a defect free weld joint. Precipitates distributed in the microstructure indicate sufficient heat input to join the material without dissolving precipitates. The developed numerical model is helpful in optimising FSW process parameters.

scholarly journals Experimental and numerical studies of sound generated by cavities

2019 ◽  
Vol 137 ◽  
pp. 01011
Author(s):  
Sebastian Rulik ◽  
Włodzimierz Wrόblewski ◽  
Mirosław Majkut ◽  
Michał Strozik ◽  
Krzysztof Rusin
Keyword(s):  
High Frequency ◽  
Measurement Techniques ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
High Amplitude ◽  
Noise Generation ◽  
Flow Conditions ◽  
Numerical Studies ◽  
Wide Range ◽  
Specific Frequency

Cavities and gaps are an important element in the construction of many devices and machines, including energy sector applications. This type of flow is usually coupled with strong pressure fluctuations inside the cavity, which are emitted into the far field in the form of a sound wave responsible for the noise generation. This applies to both subsonic and supersonic flows. Pressure fluctuations often have the character of single tones of a specific frequency and high amplitude and their generation is associated with a vortex shedding formed directly above the inlet and its interaction with the walls of the cavity. The presented work include description of developed test stand and applied measurement techniques dedicated to the analysis of high frequency phenomena. In addition, the adopted numerical model will be described, including conducted two-dimensional and three-dimensional analysis. The developed models will be validated based on experimental measurements concerning wide range of flow conditions.

Extensive Validation of HAWT Unsteady Modelling Using BEM and CFD

2020 ◽  
Author(s):  
Raffaele Peraro ◽  
Luca Menegozzo ◽  
Andrea Dal Monte ◽  
Ernesto Benini
Keyword(s):  
Wind Turbines ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Dynamic Stall ◽  
Flow Conditions ◽  
Machine Performance ◽  
Horizontal Axis Wind Turbines ◽  
Computational Fluid Dynamics Cfd ◽  
Nrel Phase Vi ◽  
Blade Element

Abstract The present work aims to present two different approaches to model the unsteady aerodynamics of horizontal-axis wind turbines (HAWTs). A complete and extensive comparison has been established between the results obtained using a low-fidelity calculation tool, as the Blade Element Momentum (BEM), and a high-fidelity technique, as the Computational Fluid Dynamics (CFD). Regarding the first calculation strategy, an accurate revision in polar diagrams calculation and the implementation of yaw and dynamic stall routines have endowed the BEM code to predict the machine performance under unsteady flow conditions. In order to achieve an accurate validation, the proposed BEM solver has been tested on AOC 15/50 and NREL Phase VI wind turbines. Referring to CFD techniques, a three-dimensional unsteady model has been improved to study the aerodynamic behaviour of the machine in case of yawed incoming wind.

Determination of the Pressure Field Using Three-Dimensional, Volumetric Velocity Measurements

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Hansheng Pan ◽  
Sheila H. Williams ◽  
Paul S. Krueger
Keyword(s):  
Poisson Equation ◽  
Temporal Resolution ◽  
Pressure Field ◽  
Three Dimensional ◽  
Vortical Flow ◽  
Flow Conditions ◽  
Velocity Measurements ◽  
Pressure Poisson Equation ◽  
Computational Fluid Dynamics Cfd

Methods to determine the pressure field of vortical flow from three-dimensional (3D) volumetric velocity measurements (e.g., from a TSI V3VTM system) are discussed. The boundary pressure was determined where necessary using the unsteady Bernoulli equation for both line integration and pressure Poisson equation methods. Error analysis using computational fluid dynamics (CFD) data was conducted to investigate the effects of spatial resolution, temporal resolution, and velocity error levels. The line integration method was more sensitive to temporal resolution, while the pressure Poisson equation method was more sensitive to boundary flow conditions. The latter was generally more suitable for V3VTM velocity measurements.

Investigations on CFD Simulations for Predicting Windage Power Losses in Spur Gears

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Y. Marchesse ◽  
C. Changenet ◽  
F. Ville ◽  
P. Velex
Keyword(s):  
Three Dimensional ◽  
Volumetric Flow Rate ◽  
Spur Gears ◽  
Power Losses ◽  
Test Rig ◽  
Cfd Simulations ◽  
Specific Test ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Method ◽  
Three Dimensional Simulations

In this paper, a computational fluid dynamics (CFD) code is applied to two- and three-dimensional simulations of windage power loss generated by spur gears rotating in air. Emphasis is placed on the various meshes associated with the finite volume method and on the choice of turbulence model. Comparing CFD predictions with the power losses measured on a specific test rig, it is shown that the fluid ejection in the radial direction must be included in order to reproduce the experimental evidence. The relative importance of the losses generated by the gear front and rear faces along with those due to the teeth is discussed. The volumetric flow rate expelled by the teeth is analyzed and the influence of flanges is highlighted.

Design considerations for the volutes of centrifugal fans and compressors

1999 ◽  
Vol 213 (4) ◽  
pp. 401-410 ◽  
Author(s):  
D Pan ◽  
A Whitfield ◽  
M Wilson
Keyword(s):  
Three Dimensional ◽  
Flow Distribution ◽  
Internal Flow ◽  
Area Ratio ◽  
Design Flow ◽  
Centrifugal Fan ◽  
Flow Conditions ◽  
Design Considerations ◽  
Centrifugal Fans ◽  
Computational Fluid Dynamics Cfd

The initial conceptual design of centrifugal fan and compressor volutes is considered and extended to accommodate overhung volute designs often used in process and turbocharger compressors. The initial passage design is then developed through the application of a commercial computational fluid dynamics (CFD) code.’ Based on the experimental data of a turbocharger compressor volute, three-dimensional, compressible, steady flow computations were carried out for alternative volute designs. Detailed internal flow data in both a conventional and a modified volute design, at both design and off-design flow conditions, are presented. The design investigation showed that enlarging the flow passage area near the tongue region, but without changing the exit-inlet area ratio of the volute, led to an improvement in the internal flow distribution at off-design flow conditions.

scholarly journals Computational Modeling of Protective Clothing

2003 ◽  
Vol os-12 (3) ◽  
pp. 1558925003os-12
Author(s):  
James J. Barry ◽  
Principal Engineer ◽  
Roger W. Hill
Keyword(s):  
Emergency Response ◽  
Protective Clothing ◽  
Three Dimensional ◽  
Convective Transport ◽  
Variable Properties ◽  
Computational Fluid Dynamics Cfd ◽  
Garment Design ◽  
Protective Garment ◽  
Good Agreement ◽  
Three Dimensional Simulations

Models based on computational fluid dynamics (CFD) have been developed to predict the performance of chemical and steam/fire protective clothing. The software computes the diffusive and convective transport of heat and gases/vapors; capillary transport of liquids; vapor and liquid sorption phenomena and phase change; and the variable properties of the various clothing layers. It can also model the effects of sweating and humidity transport to help assess the thermal stress imposed on the wearer of the clothing. Specialized geometry/grid representations of clothed humans have been created for performing two- and three-dimensional simulations. Comparisons with experimental data show good agreement in predicting the effects of fiber swell due to transients in humidity, and the models have been used to predict the sensitivity of clothing performance to material properties such as permeability under varying environmental conditions. Applications of the models include analysis of chemical protective garment design for military and emergency response personnel, comparisons of thermally protective materials for steam or fire protection, and evaluation of clothing test data.

The influence of imperfections on the flow structure of steady vortex breakdown bubbles

2007 ◽  
Vol 578 ◽  
pp. 453-466 ◽  
Author(s):  
MORTEN BRØNS ◽  
WEN ZHONG SHEN ◽  
JENS NØRKÆR SØRENSEN ◽  
WEI JUN ZHU
Keyword(s):  
Flow Structure ◽  
Vortex Breakdown ◽  
Three Dimensional ◽  
Flow Structures ◽  
Experimental Uncertainty ◽  
Apparent Paradox ◽  
Numerical Studies ◽  
Highly Sensitive ◽  
Bubble Structure ◽  
Three Dimensional Simulations

Vortex breakdown bubbles in the flow in a closed cylinder with a rotating end-cover have previously been successfully simulated by axisymmetric codes in the steady range. However, high-resolution experiments indicate a complicated open bubble structure incompatible with axisymmetry. Numerical studies with generic imperfections in the flow have revealed that the axisymmetric bubble is highly sensitive to imperfections, and that this may resolve the apparent paradox. However, little is known about the influence of specific, physical perturbations on the flow structure. We perform fully three-dimensional simulations of the flow with two independent perturbations: an inclination of the fixed cover and a displacement of the rotating cover. We show that perturbations below a realistic experimental uncertainty may give rise to flow structures resembling those obtained in experiments, that the two perturbations may interact and annihilate their effects, and that the fractal dimension associated with the emptying of the bubble can quantitatively be linked to the visual bubble structure.

scholarly journals Three-Dimensional Simulations of Scour around Pipelines of Finite Lengths

2022 ◽  
Vol 10 (1) ◽  
pp. 106
Author(s):  
Dongfang Liang ◽  
Jie Huang ◽  
Jingxin Zhang ◽  
Shujing Shi ◽  
Nichenggong Zhu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Ansys Fluent ◽  
Offshore Pipelines ◽  
Flow Solver ◽  
Bed Elevation ◽  
Numerical Studies ◽  
Computational Mesh ◽  
Equilibrium Scour Depth ◽  
Three Dimensional Simulations

In the past few decades, there have been many numerical studies on the scour around offshore pipelines, most of which concern two-dimensional setups, with the pipeline infinitely long and the flow perpendicular to the pipeline. Based on the Ansys FLUENT flow solver, this study establishes a numerical tool to study the three-dimensional scour around pipelines of finite lengths. The user-defined functions are written to calculate the sediment transport rate, update the bed elevation, and adapt the computational mesh to the new boundary. The correctness of the model has been verified against the measurements of the conventional two-dimensional scour around a long pipe and the three-dimensional scour around a sphere. A series of computations are subsequently carried out to discover how the scour hole is dependent on the pipeline length. It is found that the equilibrium scour depth increases with the pipeline length until the pipeline length exceeds four times the pipe diameter.

Fluid Dynamic Loading on Curved Riser Pipes

2003 ◽  
Vol 125 (3) ◽  
pp. 176-182 ◽  
Author(s):  
Anthi Miliou ◽  
Spencer J. Sherwin ◽  
J. Michael R. Graham
Keyword(s):  
Dynamic Loading ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Imperial College ◽  
Computational Results ◽  
Flow Conditions ◽  
Towing Tank ◽  
Riser Pipe ◽  
Flow Directions ◽  
Three Dimensional Simulations

In order to gain a preliminary understanding of the fluid dynamics developed past a curved riser pipe, a numerical investigation into the flow past curved cylinders at a Reynolds number of 100 has been performed. To approximate the flow conditions on curved riser pipes, different velocity profiles and flow directions were applied and the corresponding results compared. In addition, the fluid dynamic loading and the wake structures for curved cylinder flows were investigated. The fully three-dimensional simulations were computed with a spectral/hp element method. The computational results were compared with experiments undertaken in the towing tank facility of the Department of Aeronautics of Imperial College.

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