COMPUTATIONAL DETERMINATION OF THE DETACHMENT TIME OF THE LEUKOCYTE UNDER DIFFERENT KINETIC DISSOCIATION RATE PARAMETERS

2015 ◽  
Vol 23 (03) ◽  
pp. 457-469 ◽  
Author(s):  
HAJAR HASSANI-ARDEKANI ◽  
HANIEH NIROOMAND-OSCUII ◽  
DAMIR KHISMATULLIN
Keyword(s):  
Parametric Design ◽  
Three Dimensional ◽  
Geometrical Model ◽  
Dissociation Rate ◽  
Structural Equations ◽  
Navier Stokes ◽  
Kinetic Properties ◽  
Time Step ◽  
Flow Solver ◽  
Detachment Time

Three-dimensional simulation of the leukocyte detachment subjected to blood flow is presented. The initially captured leukocyte is modeled as a sphere adhered to the bottom wall of a cylindrical vessel via receptor/ligand bonds (P-selectin/PSGL-1). Ansys Parametric Design Language is used to create the geometrical model and couple the Navier–Stokes flow solver with structural equations and the Monte Carlo equation to define the stochastic breakage of the bonds. The assumption of equal forces on bonds has been ignored and the force on each bond is obtained from the balance between hydrodynamic forces and cellular viscoelasticity at every time step. In this model, catch-slip behavior of the P-selectin/PSGL-1 is considered by using the two-pathway dissociation model instead of the Bell model to define the rate of dissociation of each bond. Detachment time of the leukocyte is the time elapsed until all the bonds break. The effects of various values of blood inlet velocities, bond stiffness and kinetic properties of the catch bonds on the detachment time of the leukocyte are studied.

Numerical Solution of Incompressible Unsteady Flows in Turbomachinery

2000 ◽  
Vol 123 (3) ◽  
pp. 680-685 ◽  
Author(s):  
L. He ◽  
K. Sato
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Unsteady Flows ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Time Stepping ◽  
Incompressible Viscous Flow ◽  
Dual Time Stepping

A three-dimensional incompressible viscous flow solver of the thin-layer Navier-Stokes equations was developed for the unsteady turbomachinery flow computations. The solution algorithm for the unsteady flows combines the dual time stepping technique with the artificial compressibility approach for solving the incompressible unsteady flow governing equations. For time accurate calculations, subiterations are introduced by marching the equations in the pseudo-time to fully recover the incompressible continuity equation at each real time step, accelerated with a multi-grid technique. Computations of test cases show satisfactory agreements with corresponding theoretical and experimental results, demonstrating the validity and applicability of the present method to unsteady incompressible turbomachinery flows.

Prediction of VIV Response of a Flexible Pipe by Coupling a Viscous Flow Solver and a Beam Finite Element Solver

2009 ◽  
Author(s):  
Juan P. Pontaza ◽  
Raghu G. Menon
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flexible Pipe ◽  
Time Step ◽  
Flow Solver ◽  
Instantaneous Flow ◽  
Numerical Predictions ◽  
Instantaneous Flow Field ◽  
Euler Bernoulli Beam

The paper describes a fluid-structure interaction (FSI) modeling approach to predict the VIV response of a flexible pipe by coupling a three-dimensional viscous incompressible Navier-Stokes solver with a beam finite element solver – in time domain. The flexible pipe is modeled as an Euler-Bernoulli beam subject to instantaneous flow-induced forces and solved using C1 conforming finite element basis functions in space and an unconditionally stable Newmark-type discretization scheme in time. At each time step the instantaneous incremental displacement is fed back to the fluid flow solver, where the position of the pipe is updated to compute the resulting instantaneous flow field and associated flow-induced forces. Numerical predictions from the FSI model are compared to experimental measurements of a flexible pipe subject to uniform free-stream currents.

Prediction of Vortex-Induced Vibration Response of a Pipeline Span by Coupling a Viscous Flow Solver and a Beam Finite Element Solver

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Juan P. Pontaza ◽  
Raghu G. Menon
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Vibration Response ◽  
Navier Stokes ◽  
Time Step ◽  
Vortex Induced Vibration ◽  
Flow Solver ◽  
Instantaneous Flow ◽  
Numerical Predictions ◽  
Instantaneous Flow Field

This paper describes a fluid-structure interaction (FSI) modeling approach to predict the vortex-induced vibration response of a pipeline span by coupling a three-dimensional viscous incompressible Navier–Stokes solver with a beam finite element solver in time domain. The pipeline span is modeled as an Euler–Bernoulli beam subject to instantaneous flow-induced forces and solved using finite element basis functions in space and an unconditionally stable Newmark-type discretization scheme in time. At each time step, the instantaneous incremental displacement is fed back to the fluid flow solver, where the position of the pipeline is updated to compute the resulting instantaneous flow field and associated flow-induced forces. Numerical predictions from the FSI model are compared to current tank experimental measurements of a pipeline span subject to uniform free-stream currents.

The Development of an Aerodynamic Performance Prediction Tool for Modern Axial Flow Compressor Profiles

2006 ◽  
Author(s):  
Dario Bruna ◽  
Carlo Cravero ◽  
Mark G. Turner
Keyword(s):  
Performance Prediction ◽  
Parametric Design ◽  
Flow Analysis ◽  
Axial Flow ◽  
Navier Stokes ◽  
Flow Angle ◽  
Flow Solver ◽  
Aerodynamic Loss ◽  
Axial Flow Compressor ◽  
Flow Compressor

The development of a computational tool (MP-LOS) for the aerodynamic loss modeling and prediction for axial-flow compressor blade sections is presented in this paper. A state-of-the-art quasi 3-D flow solver, MISES, has been used for the flow analysis on existing airfoil geometries in many working conditions. Different values of inlet flow angle, inlet Mach number, AVDR, Reynolds number and solidity have been chosen to investigate a possible working range. The target is a loss prediction formulation that will be introduced into throughflow or axisymmetric Navier-Stokes codes for the performance prediction of multistage axial flow compressors. The loss coefficient has been correlated to the flow parameters that have shown an influence on the profile loss for the blades under study. The proposed correlation, using the described computational approach, can be extended to any profile family with the aid of any code for the parametric design of blade profiles.

scholarly journals Development of a Three-Dimensional Geometry Optimization Method for Turbomachinery Applications

2004 ◽  
Vol 10 (5) ◽  
pp. 373-385
Author(s):  
Steffen Kämmerer ◽  
Jürgen F. Mayer ◽  
Heinz Stetter ◽  
Meinhard Paffrath ◽  
Utz Wever ◽  
...  
Keyword(s):  
Optimization Problem ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Optimization Techniques ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Flow Solver ◽  
Flow Simulations ◽  
Sensitivity Equations

This article describes the development of a method for optimization of the geometry of three-dimensional turbine blades within a stage configuration. The method is based on flow simulations and gradient-based optimization techniques. This approach uses the fully parameterized blade geometry as variables for the optimization problem. Physical parameters such as stagger angle, stacking line, and chord length are part of the model. Constraints guarantee the requirements for cooling, casting, and machining of the blades.The fluid physics of the turbomachine and hence the objective function of the optimization problem are calculated by means of a three-dimensional Navier-Stokes solver especially designed for turbomachinery applications. The gradients required for the optimization algorithm are computed by numerically solving the sensitivity equations. Therefore, the explicitly differentiated Navier-Stokes equations are incorporated into the numerical method of the flow solver, enabling the computation of the sensitivity equations with the same numerical scheme as used for the flow field solution.This article introduces the components of the fully automated optimization loop and their interactions. Furthermore, the sensitivity equation method is discussed and several aspects of the implementation into a flow solver are presented. Flow simulations and sensitivity calculations are presented for different test cases and parameters. The validation of the computed sensitivities is performed by means of finite differences.

scholarly journals Vibration Performance of a Flow Energy Converter behind Two Side-by-Side Cylinders

2019 ◽  
Vol 7 (12) ◽  
pp. 435
Author(s):  
Mohammad Rasidi Rasani ◽  
Hazim Moria ◽  
Michael Beer ◽  
Ahmad Kamal Ariffin
Keyword(s):  
Three Dimensional ◽  
Reynold Number ◽  
Mean Amplitude ◽  
Navier Stokes ◽  
Cantilever Plate ◽  
Arbitrary Lagrangian Eulerian ◽  
Flow Solver ◽  
Energy Harvesters ◽  
Flow Energy ◽  
Flexible Plates

Flow-induced vibrations of a flexible cantilever plate, placed in various positions behind two side-by-side cylinders, were computationally investigated to determine optimal location for wake-excited energy harvesters. In the present study, the cylinders of equal diameter D were fixed at center-to-center gap ratio of T / D = 1 . 7 and immersed in sub-critical flow of Reynold number R e D = 10 , 000 . A three-dimensional Navier–Stokes flow solver in an Arbitrary Lagrangian–Eulerian (ALE) description was closely coupled to a non-linear finite element structural solver that was used to model the dynamics of a composite piezoelectric plate. The cantilever plate was fixed at several positions between 0 . 5 < x / D < 1 . 5 and - 0 . 85 < y / D < 0 . 85 measured from the center gap between cylinders, and their flow-induced oscillations were compiled and analyzed. The results indicate that flexible plates located at the centerline between the cylinder pairs experience the lowest mean amplitude of oscillation. Maximum overall amplitude in oscillation is predicted when flexible plates are located in the intermediate off-center region downstream of both cylinders. Present findings indicate potential to further maximize wake-induced energy harvesting plates by exploiting their favorable positioning in the wake region behind two side-by-side cylinders.

Numerical integration of the three-dimensional Navier-Stokes equations for incompressible flow

1969 ◽  
Vol 37 (4) ◽  
pp. 727-750 ◽  
Author(s):  
Gareth P. Williams
Keyword(s):  
Poisson Equation ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Wave Flow ◽  
Trigonometric Interpolation ◽  
Time Step ◽  
Navier Stokes Equations ◽  
The Poisson Equation

A method of numerically integrating the Navier-Stokes equations for certain three-dimensional incompressible flows is described. The technique is presented through application to the particular problem of describing thermal convection in a rotating annulus. The equations, in cylindrical polar co-ordinate form, are integrated with respect to time by a marching process, together with the solving of a Poisson equation for the pressure. A suitable form of the finite difference equations gives a computationally-stable long-term integration with reasonably faithful representation of the spatial and temporal characteristics of the flow.Trigonometric interpolation techniques provide accurate (discretely exact) solutions to the Poisson equation. By using an auxiliary algorithm for rapid evaluation of trigonometric transforms, the proportion of computation needed to solve the Poisson equation can be reduced to less than 25% of the total time needed to’ advance one time step. Computing on a UNIVAC 1108 machine, the flow can be advanced one time-step in 2 sec for a 14 × 14 × 14 grid upward to 96 sec for a 60 × 34 × 34 grid.As an example of the method, some features of a solution for steady wave flow in annulus convection are presented. The resemblance of this flow to the classical Eady wave is noted.

scholarly journals Three-Dimensional Simulation of Fluid–Structure Interaction Problems Using Monolithic Semi-Implicit Algorithm

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 94 ◽  
Author(s):  
Cornel Marius Murea
Keyword(s):  
Stokes Equations ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Time Step ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Dimensional Simulation ◽  
Updated Lagrangian

A monolithic semi-implicit method is presented for three-dimensional simulation of fluid–structure interaction problems. The updated Lagrangian framework is used for the structure modeled by linear elasticity equation and, for the fluid governed by the Navier–Stokes equations, we employ the Arbitrary Lagrangian Eulerian method. We use a global mesh for the fluid–structure domain where the fluid–structure interface is an interior boundary. The continuity of velocity at the interface is automatically satisfied by using globally continuous finite element for the velocity in the fluid–structure mesh. The method is fast because we solve only a linear system at each time step. Three-dimensional numerical tests are presented.

Capture, Deformation, Rolling and Detachment of a Cell on an Adhesive Surface in a Shear Flow

2008 ◽  
Author(s):  
Vijay Pappu ◽  
Prosenjit Bagchi
Keyword(s):  
Shear Flow ◽  
Bond Strength ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Adherent Cell ◽  
Membrane Mechanics ◽  
Flow Solver ◽  
Front Tracking Method ◽  
Adhesive Surface ◽  
Computational Modeling And Simulation

Three-dimensional computational modeling and simulation using front tracking method are presented on the motion of a deformable cell over an adhesive surface in a shear flow. The numerical method couples a Navier-Stokes flow solver with cell membrane mechanics, and a Monte Carlo simulation to capture stochastic formation and breakage of receptor/ligand bonds. The entire range of events during cell adhesion, namely, initial arrest of a free-flowing cell, slow rolling of an adherent cell, and detachment off the surface is simulated. Simulations are conducted to signify the role of hydrodynamic lift force that exists for a deformable particle in a wall-bounded flow. Three sets of numerical experiments are presented. In the first set, we consider the initial arrest of the cell, and show that the time needed for the cell to arrest increases with increasing Ca, but rapidly drops and saturates for higher bond strength. In the second set, we consider quasi-steady rolling motion of the cell, and predict the experimentally observed “stop and go” motion of the rolling leukocytes which is characterized by intermittent pauses and sudden jumps in cell velocity. In the third set we consider the detachment of the cell from the surface upon breakage of bonds. The bond strength needed to prevent the detachment of an adherent cell is computed and shown to be maximum for an intermediate Ca.

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