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1
Content available A two-stage model of an arteriovenous fistula maturation process
Jodko Daniel M., Obidowski Damian S., Reorowicz Piotr, Jóźwik Krzysztof
Acta of Bioengineering and Biomechanics
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2020
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Vol. 22, no. 2
139--153
EN
Purpose: An arteriovenous fistula has been a widely accepted vascular access for hemodialysis, however, a fistula maturation process is still not fully understood. In the short period of time, right after vein and artery shunting, the physical and biological changes take place mainly in the venous wall. A two-stage modeling method of arteriovenous fistula maturation process was proposed and presented. Methods: The first stage of the maturation was modeled with two-way coupled fluid structure interaction computer simulations. Whereas for the second, biological stage, a model was based on the change in the elasticity of the venous wall due to wall shear stress (WSS) modifications. Results: The relation between stress and radial and circumferential strain, based on Lame’s theory, makes possible to introduce a mathematical model defining modulus of elasticity, averaged WSS, and venous diameter as time functions. The presented model enables one to predict changes in the monitored parameters in the arteriovenous fistula taking place in the time longer than 90 days. Conclusions: We found that probably the majority of fistulas can be assessed to be mature too early, when the adequate blood flow rate is achieved but mean WSS still remains at the non-physiological level (>10 Pa).
2
Content available Simulations of safety vales for fluid power systems
Domagała Mariusz, Momeni Hassan, Fabiś-Domagała Joanna, Filo Grzegorz, Lempa Paweł
System Safety : Human - Technical Facility - Environment
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2019
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Vol. 1, nr 1
670--677
EN
Hydraulic power systems are widely used in heavy machinery. Safety of such a systems have a major importance due to the fact that any failure may cause environmental contamination or serious injury. One of the component which protects hydraulic drive systems against excessive rising of working pressure is a safety valve which aim is to maintain pressure in the systems below acceptable level. Pressure control valves which plays important role in a hydraulic systems may have very simple or complex structure. Even in case of the simplest structure of such valve modeling is not an easy task. The new quality in designing hydraulic valves bring CFD method and FSI (Fluid Structure Interaction) methods.
3
Content available remote Reducing aeration and cavitation effect in shock absorbers using uid-structure interaction simulation
Czop P., Gniłka J.
Computer Assisted Methods in Engineering and Science
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2016
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Vol. 23, no. 4
171--189
EN
This paper presents a fluid-structure interaction simulation applicable for evaluating and optimizing hydraulic valve designs. A special emphasis is placed on shim stack valve commonly used in automotive and railway shock absorbers. For simplicity, the problem was effectively reduced to a two-dimensional (2D) problem. This was accomplished by introducing section-lines along which the pressure profile was computed to find and evaluate the global minimum. The global minimum was then treated as the design ranking measure. This ranking function provided a means to choose an optimal design from a set of available design variants. In the presented results, the ranking is problem-specific as it identifies and localizes low pressure zones that are the root causes of both aeration and cavitation effects. The damping force performance was experimentally evaluated for both the baseline and optimized valve design using a shock absorber level test on a servo-hydraulic test rig.
4
Content available Fluid-Structure Interaction Modeling of Aortic Valve Stenosis at Different Heart Rates
Bahraseman H. G., Languri E. M., Yahyapourjalaly N., Espino D. M.
Acta of Bioengineering and Biomechanics
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2016
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Vol. 18, no. 3
11--20
EN
Purpose: This paper proposes a model to measure the cardiac output and stroke volume at different aortic stenosis severities using a fluid–structure interaction (FSI) simulation at rest and during exercise. Methods: The geometry of the aortic valve is generated using echocardiographic imaging. An Arbitrary Lagrangian–Eulerian mesh was generated in order to perform the FSI simulations. Pressure loads on ventricular and aortic sides were applied as boundary conditions. Results: FSI modeling results for the increment rate of cardiac output and stroke volume to heart rate, were about 58.6% and –14%, respectively, at each different stenosis severity. The mean gradient of curves of cardiac output and stroke volume to stenosis severity were reduced by 57% and 48%, respectively, when stenosis severity varied from healthy to critical stenosis. Conclusions: Results of this paper confirm the promising potential of computational modeling capabilities for clinical diagnosis and measurements to predict stenosed aortic valve parameters including cardiac output and stroke volume at different heart rates.
5
Content available remote Analysis of fluid-structure interaction of a torus subjected to wind loads
Padewska A., Szczepaniak P., Wawrzynek A.
Computer Assisted Methods in Engineering and Science
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2014
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Vol. 21, no. 2
151--167
EN
In the paper the aerodynamic forces acting on a part of a water slide or other object with curved, tubular shape, depending on the section of a torus and value of the wind velocity, were obtained. This was done by means of finite element method (FEM) and finite volume method (FVM) computer simulations, using modules: computational fluid dynamics (CFD) and fluid-structure interaction (FSI) and taking into account the Eurocode EN 1991-1-4.
6
Content available Numerical-Experimental Investigation of Squared-Based Metal Pyramids Loaded with A Blast Wave From A Small Explosives Charge
Panowicz R., Barnat W., Niezgoda T., Szymańczyk L., Grzymkowski J.
Acta Mechanica et Automatica
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2012
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Vol. 6, no. 1
49-52
EN
The paper presents the results of computer simulation and experimental investigation of blast wave action arising from a small explosive charge on a metal pyramid with a square base. This explicit finite element has been used to perform numerical analyses. This method is included in the Ls-Dyna software for modelling the behaviour of the pyramid exposed to the action of a pressure wave arising from the detonation of an explosive charge. The detonation process was described in programming bubble structure interaction was used to describe an influence of a blast wave on the structure.
7
Content available Numerical and Experimental Comparison of Combined Multilayer Protective Panels
Barnat W., Panowicz R., Niezgoda T.
Acta Mechanica et Automatica
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2012
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Vol. 6, no. 1
148-153
EN
The paper presents numerical and experimental analysis of combined multilayer protective panels. The developed structures are prospective solutions for enhancing protection of military vehicles and crucial elements of pipelines especially in places like river crossings.
8
Content available remote Flutter analysis of IV standard configuration cascades, direct integration method
Rządkowski R., Kubitz L.
Mechanics and Mechanical Engineering
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2011
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Vol. 15, nr 3
333-341
EN
A three-dimensional nonlinear time-marching method and numerical analysis for aeroelastic behaviour of oscillating blade row has been presented. The approach is based on the solution of the coupled fluid-structure problem in which the aerodynamic and structural equations are integrated simultaneously in time. Thus providing the correct formulation of a coupled problem, as the interblade phase angle at which a stability (or instability) would occur, is a part of the solution.
9
Content available Modeling of pulsating flow in a collapsible wall
Veshkina N., Zbiciński I., Obidowski D.
Inżynieria i Aparatura Chemiczna
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2010
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Nr 1
117-118
EN
The paper presents the methodology for verification of Fluid Structure Interaction (FS1) model for silicone pipe reflecting pulsating blood vessel in human body. The 3-term Yeoh model for strain energy density function was used in order to describe nonlinear behavior of siliconc material. To dctcr-:. mine the boundary conditions for CFD simulations our own experimental set-up was designed. A good agreement between simulation and experiment was achieved.
PL
W artykule przedstawiono metodę weryfikacji modelu (FSI) dla silikonowej rurki odzwierciedlającej zachowanie pulsującego naczynia krwionośnego z przepływającą wewnątrz krwią. Przy pomocy trój członowego modelu Yeoha funkcji gęstości energii naprężenia rozważono nieliniowe zachowanie materiału silikonowego. Aby uzyskać warunki brzegowe do symulacji CFD przeprowadzono badania na specjalnie do tego celu zbudowanej aparaturze. Otrzymano dobre dopasowanie danych z symulacji do eksperymentu.
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