Dynamics of Biological Cells in Shear Flows Using an Implicit Fluid-Structure Interaction Method Based on the ALE Approach

2009 ◽  
Author(s):  
Choengryul Choi ◽  
Chang Nyung Kim
Keyword(s):  
Shear Flows ◽  
Fluid Structure Interaction ◽  
Dynamic Mesh ◽  
Governing Equations ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Rigid Particles ◽  
Multiple Particles ◽  
Mesh Method ◽  
Fluid Particle Suspension

We develop a fluid-structure interaction (FSI) method based on the ALE method and a dynamic mesh method with an ultimate aim which is to simulate the complicated dynamics of rigid particles in shear flow and to investigate the rheological behavior of the suspension. Because the motion of the fluid and particles in fluid-particle suspension problems is strongly linked, the governing equations are sequentially solved in each solver and the computation is iterated until the solutions converge in a two-way coupling fashion. The mesh system initially designed is deformed or re-meshed in accordance with the moving particles by a dynamic mesh method. Numerical simulation is entirely implemented by our FSI code in the framework of FLUENT. The present simulations have demonstrated the capability of the developed FSI method in simulating the dynamics of single and multiple particles with different arbitrary shapes in shear flows.

scholarly journals Mesh moving techniques in fluid-structure interaction: robustness, accumulated distortion and computational efficiency

2020 ◽  
Author(s):  
Alexander Shamanskiy ◽  
Bernd Simeon
Keyword(s):  
Fluid Structure Interaction ◽  
Continuation Methods ◽  
Moving Mesh Method ◽  
Important Ingredient ◽  
Fluid Structure ◽  
Harmonic Extension ◽  
Structure Interaction ◽  
Computational Mesh ◽  
Mesh Method ◽  
Moving Fluid

AbstractAn important ingredient of any moving-mesh method for fluid-structure interaction (FSI) problems is the mesh moving technique (MMT) used to adapt the computational mesh in the moving fluid domain. An ideal MMT is computationally inexpensive, can handle large mesh motions without inverting mesh elements and can sustain an FSI simulation for extensive periods of time without irreversibly distorting the mesh. Here we compare several commonly used MMTs which are based on the solution of elliptic partial differential equations, including harmonic extension, bi-harmonic extension and techniques based on the equations of linear elasticity. Moreover, we propose a novel MMT which utilizes ideas from continuation methods to efficiently solve the equations of nonlinear elasticity and proves to be robust even when the mesh undergoes extreme motions. In addition to that, we study how each MMT behaves when combined with the mesh-Jacobian-based stiffening. Finally, we evaluate the performance of different MMTs on a popular two-dimensional FSI benchmark reproduced by using an isogeometric partitioned solver with strong coupling.

Modelling vortex-induced fluid–structure interaction

2007 ◽  
Vol 366 (1868) ◽  
pp. 1231-1274 ◽  
Author(s):  
Haym Benaroya ◽  
Rene D Gabbai
Keyword(s):  
Variational Approach ◽  
Equations Of Motion ◽  
Fluid Structure Interaction ◽  
Oscillator Model ◽  
List Type ◽  
Governing Equations ◽  
Fluid Structure ◽  
Reduced Order ◽  
Structure Interaction ◽  
Oscillator Models

The principal goal of this research is developing physics-based, reduced-order, analytical models of nonlinear fluid–structure interactions associated with offshore structures. Our primary focus is to generalize the Hamilton's variational framework so that systems of flow-oscillator equations can be derived from first principles. This is an extension of earlier work that led to a single energy equation describing the fluid–structure interaction. It is demonstrated here that flow-oscillator models are a subclass of the general, physical-based framework. A flow-oscillator model is a reduced-order mechanical model, generally comprising two mechanical oscillators, one modelling the structural oscillation and the other a nonlinear oscillator representing the fluid behaviour coupled to the structural motion. Reduced-order analytical model development continues to be carried out using a Hamilton's principle-based variational approach. This provides flexibility in the long run for generalizing the modelling paradigm to complex, three-dimensional problems with multiple degrees of freedom, although such extension is very difficult. As both experimental and analytical capabilities advance, the critical research path to developing and implementing fluid–structure interaction models entails formulating generalized equations of motion, as a superset of the flow-oscillator models; and developing experimentally derived, semi-analytical functions to describe key terms in the governing equations of motion. The developed variational approach yields a system of governing equations. This will allow modelling of multiple d.f. systems. The extensions derived generalize the Hamilton's variational formulation for such problems. The Navier–Stokes equations are derived and coupled to the structural oscillator. This general model has been shown to be a superset of the flow-oscillator model. Based on different assumptions, one can derive a variety of flow-oscillator models.

scholarly journals A Mathematical Simulation of the Ureter: Effects of the Model Parameters on Ureteral Pressure/Flow Relations

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Bahman Vahidi ◽  
Nasser Fatouraee ◽  
Ali Imanparast ◽  
Abbas Nasiraei Moghadam
Keyword(s):  
Shear Stress ◽  
Fluid Structure Interaction ◽  
Model Parameters ◽  
Maximum Height ◽  
Governing Equations ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Ale Formulation ◽  
Compliant Wall ◽  
Contraction Wave

Ureteral peristaltic mechanism facilitates urine transport from the kidney to the bladder. Numerical analysis of the peristaltic flow in the ureter aims to further our understanding of the reflux phenomenon and other ureteral abnormalities. Fluid-structure interaction (FSI) plays an important role in accuracy of this approach and the arbitrary Lagrangian–Eulerian (ALE) formulation is a strong method to analyze the coupled fluid-structure interaction between the compliant wall and the surrounding fluid. This formulation, however, was not used in previous studies of peristalsis in living organisms. In the present investigation, a numerical simulation is introduced and solved through ALE formulation to perform the ureteral flow and stress analysis. The incompressible Navier–Stokes equations are used as the governing equations for the fluid, and a linear elastic model is utilized for the compliant wall. The wall stimulation is modeled by nonlinear contact analysis using a rigid contact surface since an appropriate model for simulation of ureteral peristalsis needs to contain cell-to-cell wall stimulation. In contrast to previous studies, the wall displacements are not predetermined in the presented model of this finite-length compliant tube, neither the peristalsis needs to be periodic. Moreover, the temporal changes of ureteral wall intraluminal shear stress during peristalsis are included in our study. Iterative computing of two-way coupling is used to solve the governing equations. Two phases of nonperistaltic and peristaltic transport of urine in the ureter are discussed. Results are obtained following an analysis of the effects of the ureteral wall compliance, the pressure difference between the ureteral inlet and outlet, the maximum height of the contraction wave, the contraction wave velocity, and the number of contraction waves on the ureteral outlet flow. The results indicate that the proximal part of the ureter is prone to a higher shear stress during peristalsis compared with its middle and distal parts. It is also shown that the peristalsis is more efficient as the maximum height of the contraction wave increases. Finally, it is concluded that improper function of ureteropelvic junction results in the passage of part of urine back flow even in the case of slow start-up of the peristaltic contraction wave.

Modelling of Hydrodynamic Forces on a Whirling Mixing Vessel Stirrer Including Fluid-Structure Interaction

2009 ◽  
Author(s):  
Khaled M. Mohamed ◽  
Andrew G. Gerber ◽  
Gordon A. L. Holloway
Keyword(s):  
Fluid Structure Interaction ◽  
Time Integration ◽  
Rotor System ◽  
Implicit Time ◽  
Arbitrary Lagrangian Eulerian ◽  
Governing Equations ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Rotordynamic Coefficients ◽  
Reported Data

In this paper, a modeling approach for strongly coupled Fluid-Structure Interaction (FSI) simulations of a mixing vessel stirrer is presented and discussed. A finite-volume Computational Fluid Dynamics (CFD) model is used to calculate the mixer flow field while the structural dynamics of the stirrer is based on a 2-DOF damped spring-mass oscillator system. The time integration of the stirrer response is carried out using the Newmark method, and is applied in conjunction with the implicit time integration of the fluid governing equations. The solution methodology employs a transient rotorstator interface to handle frame change between the rotor system and the baffles. Furthermore, mesh adaption around the rotor system is applied using an Arbitrary Lagrangian Eulerian (ALE) treatment of the fluid governing equations. The fluid forces acting on the impeller are analyzed and a method is proposed for extracting the added mass, damping, and stiffness coefficients, which are of significance in rotordynamic analysis. The computational results for the average stirrer deflections are in close agreement with experimental data, and the trends in the extracted rotordynamic coefficients align with other previously reported data for turbomachinery.

A Strongly Coupled Fluid Structure Interaction Solution for Transient Soft Elastohydrodynamic Lubrication Problems in Reciprocating Rod Seals Based on a Combined Moving Mesh Method

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Haiping Gao ◽  
Baoren Li ◽  
Xiaoyun Fu ◽  
Gang Yang
Keyword(s):  
Fluid Structure Interaction ◽  
Elastohydrodynamic Lubrication ◽  
Moving Mesh ◽  
Moving Mesh Method ◽  
Fluid Structure ◽  
Strongly Coupled ◽  
Structure Interaction ◽  
Fluid Field ◽  
Mesh Method ◽  
Rod Seals

Soft elastohydrodynamic lubrication (EHL) problems widely exist in hydraulic reciprocating rod seals and pose great challenges because of high nonlinearity and strong coupling effects, especially when the EHL problems are of high dimensions. In this paper, a strongly coupled fluid structure interaction (FSI) model is proposed to solve the transient soft EHL problems in U-cup hydraulic reciprocating rod seals. The Navier–Stokes equations, rather than the Reynolds equation, are employed to govern the whole fluid field in the soft EHL problems, with the nonlinearity of the solid taken into consideration. The governing equations of the fluid and solid fields are combined into one equation system and solved monolithically. To determine the displacements of nodes of the fluid field, a new moving mesh method based on the combination of the Laplace equation and the leader–follower methods is put forward. At last, the proposed FSI model runs successfully with the moving mesh method, and the boundaries of the hydrodynamic lubrication zones and the hydrostatic zones are formed automatically and change dynamically during the coupling process. The results are as follows: The soft EHL problems show typical characteristics, like the constriction effects of the lubricating films, and the law of dynamic development of the lubricating films and the fluid pressures is revealed. The minimum stroke lengths needed to generate complete lubricating films vary with the rod speeds and movement directions, so the design of the rod seals should be paid close attention to, in particular the rod seals of short stroke lengths. Furthermore, along with the dynamic development processes of the fluid pressures during the instroke of U-cup seals, the lubricating film humps expand and locate between the fluid pressure abrupt points and the outlet zones. After the U-cup seals reach the steady-states, the fluid abrupt points disappear and no changes of the film humps are observed. Theoretically, the proposed method can be popularized to solve similar soft EHL problems.

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