scholarly journals Force and torque on spherical particles in micro-channel flows using computational fluid dynamics

2016 ◽  
Vol 3 (7) ◽  
pp. 160298 ◽  
Author(s):  
Jin Suo ◽  
Erin E. Edwards ◽  
Ananyaveena Anilkumar ◽  
Todd Sulchek ◽  
Don P. Giddens ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cell Adhesion ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Spherical Particles ◽  
Microfluidic Channels ◽  
Cfd Modelling ◽  
Cfd Simulations ◽  
Hemodynamic Force

To delineate the influence of hemodynamic force on cell adhesion processes, model in vitro fluidic assays that mimic physiological conditions are commonly employed. Herein, we offer a framework for solution of the three-dimensional Navier–Stokes equations using computational fluid dynamics (CFD) to estimate the forces resulting from fluid flow near a plane acting on a sphere that is either stationary or in free flow, and we compare these results to a widely used theoretical model that assumes Stokes flow with a constant shear rate. We find that while the full three-dimensional solutions using a parabolic velocity profile in CFD simulations yield similar translational velocities to those predicted by the theoretical method, the CFD approach results in approximately 50% larger rotational velocities over the wall shear stress range of 0.1–5.0 dynes cm −2 . This leads to an approximately 25% difference in force and torque calculations between the two methods. When compared with experimental measurements of translational and rotational velocities of microspheres or cells perfused in microfluidic channels, the CFD simulations yield significantly less error. We propose that CFD modelling can provide better estimations of hemodynamic force levels acting on perfused microspheres and cells in flow fields through microfluidic devices used for cell adhesion dynamics analysis.

Characterisation of Cell Adhesion to Substrate Materials and the Resistance to Enzymatic and Mechanical Cell-Removal

2008 ◽  
Vol 1097 ◽  
Author(s):  
Helen Jane Griffiths ◽  
John G Harvey ◽  
James Dean ◽  
James A Curran ◽  
Athina E Markaki ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cell Adhesion ◽  
Liquid Flow ◽  
Adhesive Strength ◽  
Cell Detachment ◽  
Shear Forces ◽  
Cfd Modelling ◽  
Computational Fluid Dynamics Cfd

AbstractCell-implant adhesive strength is important for prostheses. In this paper, an investigation is described into the adhesion of bovine chondrocytes to Ti6Al4V-based substrates with different surface roughnesses and compositions. Cells were cultured for 2 or 5 days, to promote adhesion. The ease of cell removal was characterised, using both biochemical (trypsin) and mechanical (accelerated buoyancy and liquid flow) methods. Computational fluid dynamics (CFD) modelling has been used to estimate the shear forces applied to the cells by the liquid flow. A comparison is presented between the ease of cell detachment indicated using these methods, for the three surfaces investigated.

Extent, capacity and possibilities of computational fluid dynamics as a design tool for pump intakes: a review

2018 ◽  
Vol 18 (5) ◽  
pp. 1518-1530 ◽  
Author(s):  
Jie Zhang ◽  
Tien Yee
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Design Tool ◽  
Cfd Modeling ◽  
Cfd Simulations ◽  
Pump Station ◽  
Computational Fluid Dynamics Cfd ◽  
Future Direction ◽  
Computational Resources

Abstract Flow near pump intakes is three-dimensional in nature, and is affected by many factors such as the geometry of the intake bay, uniformity of approach flow, critical submergence, placements and operation combinations of pumps and so on. In the last three decades, advancement of numerical techniques coupled with the increase in computational resources made it possible to conduct computational fluid dynamics (CFD) simulations on pump intakes. This article reviews different aspects involved in CFD modeling of pump station intakes, outlines the challenges faced by current CFD modelers, and provides an attempt to forecast future direction of CFD modeling of pump intakes.

Investigation of an innovative non-free vortex aerodynamic procedure to design a single-stage transonic compressor

2017 ◽  
Vol 232 (11) ◽  
pp. 2132-2143 ◽  
Author(s):  
A Shahsavari ◽  
M Nili-Ahmadabadi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Design Method ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Meridional Plane ◽  
Transonic Compressor ◽  
Performance Map

This paper presents an innovative design method for a transonic compressor based on the radial equilibrium theory by means of increasing blade loading. Firstly, the rotor blade of a transonic compressor is redesigned based on the constant spanwise de-Haller number and diffusion. The design method leads to an unconventional increased axial velocity distribution in tip section, which originates from non-uniform enthalpy distribution assumption. A code is applied to extract the compressor meridional plane and blade-to-blade geometry containing rotor and stator in order to design the blade three-dimensional view. A structured grid is generated for the numerical domain of fluid. Finer grids are used for the regions near walls to capture the boundary layer effects and behavior. Reynolds-averaged Navier–Stokes equations are solved by finite volume method for rotating zones (rotor) and stationary zones (stator). The experimental data, available for the performance map of NASA Rotor67, is used to validate the results of the current simulations. Then, the capability of the design method is validated by computational fluid dynamics that is capable of predicting the performance map. The numerical results of the new geometry by representing 11% improvement in efficiency and 19% in total pressure ratio verify the new method advantages. The computational fluid dynamics results also show that the newly designed rotor blades due to a higher velocity in the tip section have a special capacity to increase the loading without any separation. The mass flow reduction is observed in the new geometry, which could be easily improved by changing stagger angle.

Comparisons of Magnetic Resonance Imaging Velocimetry With Computational Fluid Dynamics

1997 ◽  
Vol 119 (1) ◽  
pp. 103-109 ◽  
Author(s):  
B. Newling ◽  
S. J. Gibbs ◽  
J. A. Derbyshire ◽  
D. Xing ◽  
L. D. Hall ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Magnetic Resonance ◽  
Flow Field ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Resonance Imaging ◽  
Pipe System

The flow of Newtonian liquids through a pipe system comprising of a series of abrupt expansions and contractions has been studied using several magnetic resonance imaging (MRI) techniques, and also by computational fluid dynamics. Agreement between those results validates the assumptions inherent to the computational calculation and gives confidence to extend the work to more complex geometries and more complex fluids, wherein the advantages of MRI (utility in opaque fluids and noninvasiveness) are unique. The fluid in the expansion-contraction system exhibits a broad distribution of velocities and, therefore, presents peculiar challenges to the measurement technique. The MRI protocols employed were a two-dimensional tagging technique, for rapid flow field visualisation, and three-dimensional echo-planar and gradient-echo techniques, for flow field quantification (velocimetry). The Computational work was performed using the FIDAP package to solve the Navier-Stokes equations. The particular choice of parameters for both MRI and computational fluid dynamics, which affect the results and their agreement, have been addressed.

Microscale Computational Fluid Dynamics Simulation for Wind Mapping Over Complex Topographic Terrains

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Ashkan Rasouli ◽  
Horia Hangan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Spatial Resolution ◽  
Three Dimensional ◽  
Dynamics Simulation ◽  
Scale Model ◽  
Cfd Model ◽  
Cfd Simulations ◽  
Wide Range ◽  
Wind Mapping

Wind mapping is of utmost importance in various wind energy and wind engineering applications. The available wind atlases usually provide wind data with low spatial resolution relative to the wind turbine height and usually neglect the effect of topographic features with relatively large or sudden changes in elevation. Two benchmark cases are studied for computational fluid dynamics (CFD) model evaluation on smooth two-dimensional (2D) and three-dimensional (3D) hills. Thereafter, a procedure is introduced to build CFD model of a complex terrain with high terrain roughness heights (dense urban area with skyscrapers) starting from existing topography maps in order to properly extend the wind atlas data over complex terrains. CFD simulations are carried out on a 1:3000 scale model of complex topographic area using Reynolds averaged Navier–Stokes (RANS) equations along with shear stress transport (SST) k-ω turbulence model and the results are compared with the wind tunnel measurements on the same model. The study shows that CFD simulations can be successfully used in qualifying and quantifying the flow over complex topography consisting of a wide range of roughness heights, enabling to map the flow structure with very high spatial resolution.

Characterization of Stiffness and Damping in Textured Sector Pad Micro Thrust Bearings Using Computational Fluid Dynamics

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Christos I. Papadopoulos ◽  
Pantelis G. Nikolakopoulos ◽  
Lambros Kaiktsis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Dynamic Performance ◽  
Surface Texturing ◽  
Geometrical Parameters ◽  
Cfd Simulations ◽  
Thrust Bearings ◽  
Bearing Stiffness ◽  
Stiffness And Damping

In the present paper, a study of stiffness and damping in sector-pad micro thrust bearings with artificial surface texturing is presented, based on computational fluid dynamics (CFD) simulations. The bearing pads are modeled as consecutive three-dimensional independent microchannels, each consisting of a smooth rotating wall (rotor) and a partially textured stationary wall (stator). CFD simulations are performed, consisting in the numerical solution of the Navier–Stokes equations for incompressible isothermal flow. The goal of the present study is to characterize the dynamic behavior of favorable designs, identified in previous optimization studies, comprising parallel and convergent thrust bearings with rectangular texture patterns. To this end, a translational degree of freedom (DOF) along the thrust direction and a rotational (tilting) DOF of the rotor are considered. By implementing appropriate small perturbations around the equilibrium (steady-state) position and processing the simulation results, the stiffness and damping coefficients of the bearing are obtained for each DOF. The computed dynamic coefficients of textured thrust bearings are compared to those of conventional (smooth slider) designs. It is found that the dependence of bearing stiffness and damping on geometrical parameters exhibits the same trends for both DOFs. Both stiffness and damping are found to increase with bearing width. In general, increasing the bearing convergence ratio results in increased bearing stiffness and decreased damping. Finally, the present results demonstrate that properly textured parallel sliders are characterized by an overall dynamic performance that is superior to that of smooth converging sliders.

Studies of Blood Flow in Arterial Bifurcations Using Computational Fluid Dynamics

1994 ◽  
Vol 208 (3) ◽  
pp. 163-175 ◽  
Author(s):  
X Y Xu ◽  
M W Collins
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Flow Separation ◽  
Stokes Equations ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Newtonian Viscosity ◽  
Numerical Predictions

The local blood flow in arteries, especially at bends and bifurcations, is correlated with the distribution of atherosclerotic lesions. The flow is three-dimensional, unsteady and difficult to measure in vivo. In this paper a numerical treatment of blood flow in general three-dimensional arterial bifurcations is presented. The flow is assumed to be laminar and incompressible, the blood non-Newtonian and the vessel wall rigid. The three-dimensional time-dependent Navier-Stokes equations are employed to describe the flow, and a newly developed computational fluid dynamics (CFD) code AST EC based on finite volume methods is used to solve the equations. A comprehensive range of code validations has been carried out. Good agreement between numerical predictions and in vitro model data is demonstrated, but the correlation with in vivo measurements is less satisfactory. Effects of the non-Newtonian viscosity have also been investigated. It is demonstrated that differences between Newtonian and non-Newtonian flows occur mainly in regions of flow separation. With the non-Newtonian fluid, the duration of flow separation is shorter and the reverse flow is weaker. Nevertheless, it does not have significant effects on the basic features of the flow field. As for the magnitude of wall shear stress, the effect of non-Newtonian viscosity might not be negligible.

Characterization of Stiffness and Damping in Textured Sector-Pad Micro- Thrust Bearings Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
C. I. Papadopoulos ◽  
P. G. Nikolakopoulos ◽  
L. Kaiktsis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Dynamic Performance ◽  
Geometrical Parameters ◽  
Cfd Simulations ◽  
Thrust Bearings ◽  
Micro Channels ◽  
Bearing Stiffness ◽  
Stiffness And Damping

In the present paper, a study of stiffness and damping in sector-pad micro-thrust bearings with artificial surface texturing is presented, based on Computational Fluid Dynamics (CFD) simulations. The bearing pads are modeled as consecutive three-dimensional independent micro-channels, each consisting of a smooth rotating wall (rotor) and a partially textured stationary wall (stator). CFD simulations are performed, consisting in the numerical solution of the Navier-Stokes equations for incompressible isothermal flow. The goal of the present study is to characterize the dynamic behavior of favorable designs, identified in previous optimization studies, comprising parallel and convergent thrust bearings with rectangular texture patterns. To this end, a translational degree of freedom (DOF) along the thrust direction and a rotational (tilting) DOF of the rotor are considered. By implementing appropriate small perturbations around the equilibrium (steady-state) position and processing the simulation results, the stiffness and damping coefficients of the bearing are obtained for each DOF. The computed dynamic coefficients of textured thrust bearings are compared to those of conventional (smooth slider) designs. It is found that the dependence of bearing stiffness and damping on geometrical parameters exhibits the same trends for both DOFs. Both stiffness and damping are found to increase with bearing width. In general, increasing the bearing convergence ratio results in increased bearing stiffness and decreased damping. Finally, the present results demonstrate that properly textured parallel sliders are characterized by an overall dynamic performance which is superior to that of smooth converging sliders.

scholarly journals The Computational fluid dynamics Performance Analysis of Horizontal Axis Wind Turbine

2019 ◽  
Vol 10 (2) ◽  
pp. 1072 ◽  
Author(s):  
Naji Abdullah Mezaal ◽  
Osintsev K. V. ◽  
Alyukov S.V.
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Theoretical Calculations ◽  
Three Dimensional ◽  
Cylindrical Shape ◽  
Horizontal Axis Wind Turbine ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Cornell University ◽  
Blade Tip

<span lang="EN-US">Computational fluid dynamics (CFD) simulations were performed in the present study using ANSYS Fluent 18.0, a commercially available CFD package, to characterize the behaviour of the new HAWT. Static three-dimensional CFD simulations were conducted. The static torque characteristics of the turbine and the simplicity of design highlight its suitability for the GE 1.5xle turbine. The major factor for generating the power through the HAWT is the velocity of air and the position of the blade angle in the HAWT blade assembly. The study presents the effect of The blade is 43.2 meters long and starts with a cylindrical shape at the root and then transitions to the airfoils S818, S825 and S826 for the root, body and tip, respectively. This blade also has pitch to vary as a function of radius, giving it a twist and the pitch angle at the blade tip is 4 degrees. This blade was created to be similar in size to a GE 1.5xle turbine by Cornell University [1]. In addition, note that to represent the blade being connected to a hub, the blade root is offset from the axis of rotation by 1 meter. The hub is not included in our model. The experimental analysis of GE 1.5xle turbine, so that possible the result of CFD analysis can be compared with theoretical calculations. CFD workbench of ANSYS is used to carry out the virtue simulation and testing. The software generated test results are validated through the experimental readings. Through this obtainable result will be in the means of maximum constant power generation from HAWT.</span>

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