Three-dimensional Fluid-structure Interaction Models Research Articles

A new approach of using organ-on-a-chip and fluid-structure interaction modeling to investigate biomechanical characteristics in tissue-engineered blood vessels.

The tissue-engineered blood vessel (TEBV) has been developed and used in cardiovascular disease modeling, preclinical drug screening, and for replacement of native diseased arteries. Increasing attention has been paid to biomechanical cues in TEBV and other tissue-engineered organs to better recapitulate the functional properties of the native organs. Currently, computational fluid dynamics models were employed to reveal the hydrodynamics in TEBV-on-a-chip. However, the biomechanical wall stress/strain conditions in the TEBV wall have never been investigated. In this paper, a straight cylindrical TEBV was placed into a polydimethylsiloxane-made microfluidic device to construct the TEBV-on-a-chip. The chip was then perfused with cell culture media flow driven by a peristaltic pump. A three-dimensional fluid-structure interaction (FSI) model was generated to simulate the biomechanical conditions in TEBV and mimic both the dynamic TEBV movement and pulsatile fluid flow. The material stiffness of the TEBV wall was determined by uniaxial tensile testing, while the viscosity of cell culture media was measured using a rheometer. Comparison analysis between the perfusion experiment and FSI model results showed that the average relative error in diameter expansion of TEBV from both approaches was 10.0% in one period. For fluid flow, the average flow velocity over a period was 2.52cm/s from the FSI model, 10.5% higher than the average velocity of the observed cell clusters (2.28mm/s) in the experiment. These results demonstrated the facility to apply the FSI modeling approach in TEBV to obtain more comprehensive biomechanical results for investigating mechanical mechanisms of cardiovascular disease development.

A 3-D FSI simulation for the performance prediction and valve dynamic analysis of a hermetic reciprocating compressor

Hermetic reciprocating compressors consume the most electricity, and an improvement in compressor performance has a direct impact on compressor efficiency. Valve motion and pressure pulsation should be precisely predicted to assess the thermodynamic performance. In this paper, a three-dimensional fluid-structure interaction model validated by experiments is developed to investigate the oscillation motion of the suction and discharge reed valves, compression power, and mass flow rate of a hermetic reciprocating compressor operating under ASHRAE (54.4 °C/-23.3 °C) at the speed of 2100 rpm and additional specific refrigerator operating conditions such as (25 °C/-20 °C) and (40 °C/-25 °C) at the speeds of 1300 and 1600 rpms, respectively. Different from the others, no prior study has explored the whole compression cycle, including all four essential phases by showing the compressor's pV and valve oscillation diagrams under these operating conditions. In addition, the advanced mesh refinement method is computationally straightforward and has excellent numerical stability. Using this method as the third one in the literature, the mesh structure of complex geometries is generated without additional time or effort. Thus, the development of the model and the solution takes significantly less time than with other methods. When the obtained numerical outputs using the RNG k-ε turbulence model and experimental data are compared, the turbulence model is found to be reliable in the prediction of thermodynamic performance and valve lift. The deviations between experimental and numerical outcomes are 1.79%, -0.6%, and 3.44% for compression power and -1.28%, 0.6%, and 2.44% for mass flow rate regarding ASHRAE and additional operating conditions.

An efficient three-dimensional multiphase fluid structure interaction model on GPU for water impact of a moving body with complex geometries

This paper presents an efficient three-dimensional (3D) multiphase fluid structure interaction (FSI) model to simulate water impact of complex moving bodies in ocean engineering. This numerical model adopts an improved ghost cell method (GCM) to enforce the boundary conditions on the moving boundaries and the gradient augmented level set (GALS) method to capture the nonlinear free surfaces. An improved iso-surface representation method is highlighted to track arbitrary moving bodies such as sharp or concave shapes. Also, a GPU-CUDA parallel framework is incorporated to greatly accelerate the computational performance. The accuracy and capability of the present model is validated by simulating 3D water entry of arbitrary free-falling bodies (a sphere, a wedge, a wedge with side plates, and a catamaran). Excellent acceleration performance of the present GPU model is demonstrated. The present results including the slamming coefficient, the acceleration, and the local pressure agree satisfactorily with the experimental data. The complex flow evolutions are well captured such as long cavity wall, the pinch-off of the cavity, and the air entrapment. Also, the air entrapment and 3D effects are confirmed to be nonnegligible for the water impact of complex bodies with enclosed sections, which can be well predicted by the present model.

A three-dimensional fluid-structure interaction model based on SPH and lattice-spring method for simulating complex hydroelastic problems

The present work revolves around the development of a 3D particle-based Fluid-Structure Interaction (FSI) solver to simulate hydroelastic problems that involve free surface. The three-dimensional Volume-Compensated Particle Method (VCPM) for modelling deformable solid bodies is developed within the open-source SPH software package DualSPHysics. Complex 3D FSI problems are readily simulated within a reasonable time frame thanks to the parallel scalability of DualSPHysics on both CPU and GPU. The Sequential Staggered (SS) scheme paired with a multiple time-stepping procedure is implemented in DualSPHysics for coupling the SPH and VCPM models. It is found that the SPH-VCPM method is computationally more efficient than the previously reported SPH-TLSPH method. Extensive validations have been performed based on some very recent 3D experimental setups that involve violent free surface and complex structural dynamics. Findings from this research highlight the capability of the 3D SPH-VCPM model to reproduce some of the physical observations that were not captured by previous 2D studies. Some preliminary 3D FSI results involving solid fracture are also demonstrated.

Mechanical behaviors of pipeline inspection gauge (pig) in launching process based on Coupled Eulerian-Lagrangian (CEL) method

Successful launching of the pig is the premise for ensuring the efficiency and accuracy of the pigging operation. This study investigates the effect of the flow field on pig launching by the three-dimensional (3D) fluid-structure interaction (FSI) model based on the Coupled Eulerian-Lagrangian (CEL) method for the first time. Besides, the flow field experiment and the dragging experiment are conducted to verify the reliability of the simulation results. Four parameters as friction force, mandrel flip angle, pig velocity, cup deformation are selected to describe the mechanical behaviors of the pig. Research results indicate that the flow field has a significant effect on contact behaviors between the pig and the pipeline in the pig running-in stage but less effect on that in the steady stage, which presents the necessity of the FSI simulation for investigating the pig launching process.

FSI simulation of the suction valve on the piston for reciprocating compressors

The suction valve is an essential one-way valve inside the reciprocating compressor controlling the suction gas flow. It is usually installed on the cylinder head of the compressor. However, the suction valve in oil-free mini compressors was preferred to be installed on the piston to cool down the bearing inside the piston by the suction flow. In this case, the motion of the piston will act varying accelerated speed on the valve plate. During its opening process, the valve plate would be pushed by resultant force of the inertia force generated by the accelerated speed and the flow thrust together. It would result in too high valve lift and deformation, and decrease the reliability of the valve plate extremely. For this reason, the stiffness of the valve on the piston should be greater than that on the cylinder head. However, stiffness strengthened valve plate moving with the piston would behaves oscillation motion during its opening and closing process. In this paper, a three-dimensional fluid-structure interaction (FSI) model validated by experiments was established using ADINA to study the oscillation motion of the valve installed on the piston. Obtained results showed that the lift integral of the valve on the piston was 4.5% less than that of the valve on the cylinder head, and the impact speed on the valve seat of the valve on the piston was smaller than that of the valve on the cylinder head, which indicated that the suction valve installed on the piston had higher reliability.

Simulation and Experiment Study on Dynamic Characteristic of Reed Valve of Reciprocating Compressor Based on Fluid-Structure Interaction Model

The working process of the suction valve with complex shape called “boqi” and the discharge valve with four arms were simulated by the three-dimensional fluid-structure interaction method in this paper. By setting the gap boundary condition between the valve and the valve plate, hanged the connection between the valve and the valve plate in the model, and the problem of flow area connectivity caused by the opening and closing of the valve was solved. It solved the mesh overlapped and distorted problem caused by the valve motion. According to the simulation, the results of valve’s dynamic characteristic and gas pressure were obtained. A valve displacement test bench of reciprocating compressor was built, and the valve motions under different rotational speed and different pressure ratio was tested. Comparing the simulation results with the experimental results, it shows that the three-dimensional fluid-structure interaction model can be used to simulate the interaction between the valve with complex shape and the compressor fluid field. From the simulation results, the pressure cloud map of the valve under different conditions was extracted. Finally, the method proposed in this paper was used to analyze the valve’s displacement, speed and stress.

Does Blast Exposure to the Torso Cause a Blood Surge to the Brain?

The interaction of explosion-induced blast waves with the torso is suspected to contribute to brain injury. In this indirect mechanism, the wave-torso interaction is assumed to generate a blood surge, which ultimately reaches and damages the brain. However, this hypothesis has not been comprehensively and systematically investigated, and the potential role, if any, of the indirect mechanism in causing brain injury remains unclear. In this interdisciplinary study, we performed experiments and developed mathematical models to address this knowledge gap. First, we conducted blast-wave exposures of Sprague-Dawley rats in a shock tube at incident overpressures of 70 and 130 kPa, where we measured carotid-artery and brain pressures while limiting exposure to the torso. Then, we developed three-dimensional (3-D) fluid-structure interaction (FSI) models of the neck and cerebral vasculature and, using the measured carotid-artery pressures, performed simulations to predict mass flow rates and wall shear stresses in the cerebral vasculature. Finally, we developed a 3-D finite element (FE) model of the brain and used the FSI-computed vasculature pressures to drive the FE model to quantify the blast-exposure effects in the brain tissue. The measurements from the torso-only exposure experiments revealed marginal increases in the peak carotid-artery overpressures (from 13.1 to 28.9 kPa). Yet, relative to the blast-free, normotensive condition, the FSI simulations for the blast exposures predicted increases in the peak mass flow rate of up to 255% at the base of the brain and increases in the wall shear stress of up to 289% on the cerebral vasculature. In contrast, our simulations suggest that the effect of the indirect mechanism on the brain-tissue-strain response is negligible (<1%). In summary, our analyses show that the indirect mechanism causes a sudden and abundant stream of blood to rapidly propagate from the torso through the neck to the cerebral vasculature. This blood surge causes a considerable increase in the wall shear stresses in the brain vasculature network, which may lead to functional and structural effects on the cerebral veins and arteries, ultimately leading to vascular pathology. In contrast, our findings do not support the notion of strain-induced brain-tissue damage due to the indirect mechanism.

3D FSI FEA SIMULATION AND ANALYSES OF THE DYNAMIC CHARACTERISTICS OF A DISPLACEMENT-SENSITIVE LIQUID DAMPER

A three-dimensional fluid-structure interaction (FSI) model with arbitrary Lagrangian-Eulerian(ALE) liquid-structure coupling and sliding-mesh fluid-fluid coupling of a displacement-sensitive (DS) liquid damper with cylinder-wall grooves was constructed. The synchronous-iterative FSI method combined with the moving mesh control method was utilized to calculate the dynamic responses of the damper system under dynamic excitations. The results were partially verified by experiments. Several important problems were analyzed, including the damping characteristics under a high-speed and shock input, effects of the piston’s initial position offset and the grooves’ structural variation on the damping characteristics. The results show that the offset of the piston’s initial position along the direction of the compression stroke was favorable, but the initial piston offset along the direction of the extension stroke was unfavorable. The damper with cylinder-wall grooves could reduce the instantaneous peak of damping force under a shock condition. The damping characteristics of the damper with multi-grooves showed to be an approximate superposition of the effect of each groove. The damping ratio was increased when the piston velocity amplitude decreased. The damping force fluctuation occurred when the groove paths were opened and closed under higher speed conditions, but it could be improved by extending the end section. These results are helpful for the design of the passive controlled damping characteristics of this kind of liquid dampers.

A detrending-extracting-zooming-based speed measurement method for hermetic reciprocating compressor

The rotational speed is an important parameter of hermetic compressor, which has a great significance on refrigeration capacity, power consumption, and coefficient of performance. However, the change of load condition causes the moving parts of compressor and the refrigerant to operate unsteadily, which leads to large deviation when the traditional speed measurement method is used. To solve this issue, this work proposes a Detrending-Extracting-Zoming (DEZ) method to measure the rotational speed of hermetic reciprocating compressor. A three-dimensional fluid structure interaction (FSI) model is set up to reveal the influence law of pressure pulsation at different operating speeds. On this basis, it can be found that the trend component and harmonic components of pressure pulsation affect the calculation of rotational frequency. Based on the above mechanism, the DEZ first eliminates the trend component of pressure pulsation, then extracts the feature component, and finally calculates the exact rotational frequency by spectrum zooming. The results of simulation and experiment show that the proposed measurement method is reliable under different load conditions, and the maximum error is smaller than ±1 rpm at 2 s sampling time. The key scientific contribution of this paper is providing a rotational frequency calculation method for unstable pressure signal, which can offer universal references to the operating state detection in hermetic reciprocating machines, such as fuel engines and air compressors.

The influence of the elastic modulus of the plaque in carotid artery on the computed results of FFRCT

To study the effect of carotid plaque elastic modulus on hemodynamic parameters such as fractional flow reserve derived from computed tomography angiography (FFRCT), so as to provide a more accurate modeling method for the calculation of FFRCT of the carotid artery stenosis, three clinical cases with different ages were used to establish the three-dimensional fluid-structure interaction (FSI) model with different elastic modulus of the vessel wall and the plaque according to their age. Hemodynamic parameters were obtained by numerical simulations of the FSI models. Comparing the results from the three patients, there is little difference in hemodynamic parameters such as FFRCT between models with the same elastic modulus of the vessel wall but different elastic modulus of the plaque, and there is no distinct differences in the distribution of flow field and stress field. Therefore, for the FSI modeling of the carotid artery stenosis, the elastic modulus of carotid artery plaque can be approximately set as the elastic modulus of vessel wall in the numerical simulation when using FFRCT for assessing carotid artery stenosis of high-risk age patients.

A three-dimensional fluid-structure interaction (FSI) model for estimating the heart energy consumption of blood flow through the aortic valve

A three-dimensional fluid-structure interaction (FSI) model for estimating the heart energy consumption of blood flow through the aortic valve

A novel method for describing biomechanical properties of the aortic wall based on the three-dimensional fluid-structure interaction model.

Our goal was to present a novel non-invasive approach for assessment of aortic wall displacement to describe its biomechanical properties during the cardiac cycle. The fluid-structure interaction (FSI) technique was used to reconstruct aortic wall displacement based on computed tomography angiography and 2-dimensional speckle-tracking technique (2DSTT) data collected from 20 patients [10 with healthy aortas (AA) and 10 with abdominal aortic aneurysms (AAAs)]. The mechanical properties of the wall of the aorta were described by the Yeoh hyperelastic materials model with α and β parameters, and wall displacement was determined with 2DSTT. The mechanical parameters of the wall of the aorta in the FSI model were automatically updated in the calculation loop until the calculated and clinically measured wall movements were the same. Results showed 98% accuracy of FSI compared to 2DSTT for AA and AAA (P > 0.05). The mean wall deformation for AA was 2.45 ± 0.12 mm and 2.49 ± 0.10 mm for FSI and 2DSTT, respectively (P = 0.40), whereas that for AAA was 2.84 ± 0.44 mm and 2.88 ± 0.45 mm, respectively (P = 0.83). The FSI analysis indicated that the α and β parameters for AA were equal to 14.35 ± 1.30 N⋅cm-2 and 9.33 ± 1.08 N⋅cm-2, respectively; and for AAA, α was 11.00 ± 0.49 N⋅cm-2 and β was 79.46 ± 4.32 N⋅cm-2. The FSI technique may be successfully applied to assess the mechanical parameters of patient-specific aortic walls using computed tomography angiographic and 2DSTT measurements.

Investigation on the delayed closure of the suction valve in the refrigerator compressor by FSI modeling

The backflow through valve due to the delayed closure, is quite difficult to predict as the effective flow area of valve is highly dependent upon the interaction between the fluid flow and the valve's motion. To solve this issue, this paper presents the simulation of the complete compression cycle of a refrigerator compressor by a three-dimensional fluid structure interaction (FSI) model. This proposed FSI model was validated by experiments, which showed that the FSI method was able to detailedly analyze the thermodynamic process during the compression cycle. Based on the FSI model, the effects of compressor rotation speed and valve parameters on the oscillation and delayed closure of the valve were investigated. The characteristic rotation speed for a reed valve was found and defined, at which the maximal delayed closure and backflow occurred. According to the simulation results, an empirical correlation to predict the characteristic rotation speed was obtained.

Investigation on the variation of pressure in the cylinder of the refrigerator compressor based on FSI model

The performance of refrigerator compressor has a significant influence on the coefficient of performance of the refrigerator. In order to find out the main cause for the variation of the performance, this paper presents a three-dimensional fluid structure interaction (FSI) model of the refrigerator compressor and an experimental investigation to verify the model. To record the p-V indicator diagram, a refrigerator compressor was modified and the pressure sensor was installed. Based on the FSI model, the variation of pressure in the cylinder that influenced the performance of compressor was identified by varying working condition, rotating speed and refrigerant. The FSI model and result could provide useful information for both performance testing and optimization of compressor performance.

A preliminary investigation of the growth of an aneurysm with a multiscale monolithic Fluid-Structure interaction solver

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more.

Fluid–structure interaction model of dynamic behavior of the discharge valve in a rotary compressor

A three-dimensional fluid–structure interaction model is proposed for the discharge valve movement in a rotary compressor. The compression chamber pressure measured by the experiment confirmed that the fluid–structure interaction model is able to predict the valve dynamic behavior precisely. To demonstrate that the fact of the discharge port being covered partly by the cylinder and the roller cannot be ignored in the valve model, another fluid–structure interaction model in which the discharge port is not covered and the cylinder shape is simplified to be cylindrical is also specially presented. In this simplified fluid–structure interaction model, the flow energy loss through the discharge valve is 68.8% of that in the fluid–structure interaction model, and the impact velocity of the valve reed impacting on the retainer is 2.9 m/s higher than that in the FSI model. It is found that the valve reed is obviously inclined because the discharge port is covered partly by the cylinder.

Digital image correlation for full-field time-resolved assessment of arterial stiffness

Pulse wave velocity (PWV) of the arterial system is a very important parameter to evaluate cardiovascular health. Currently, however, there is no golden standard for PWV measurement. Digital image correlation (DIC) was used for full-field time-resolved assessment of displacement, velocity, acceleration, and strains of the skin in the neck directly above the common carotid artery. By assessing these parameters, propagation of the pulse wave could be tracked, leading to a new method for PWV detection based on DIC. The method was tested on five healthy subjects. As a means of validation, PWV was measured with ultrasound (US) as well. Measured PWV values were between 3.68 and 5.19 m/s as measured with DIC and between 5.14 and 6.58 m/s as measured with US, with a maximum absolute difference of 2.78 m/s between the two methods. DIC measurements of the neck region can serve as a test base for determining a robust strategy for PWV detection, they can serve as reference for three-dimensional fluid-structure interaction models, or they may even evolve into a screening method of their own. Moreover, full-field, time-resolved DIC can be adapted for other applications in biomechanics.

On the continuity of mean total normal stress in geometrical multiscale cardiovascular problems

In this work an iterative strategy to implicitly couple dimensionally-heterogeneous blood flow models accounting for the continuity of mean total normal stress at interface boundaries is developed. Conservation of mean total normal stress in the coupling of heterogeneous models is mandatory to satisfy energetic consistency between them. Nevertheless, existing methodologies are based on modifications of the Navier–Stokes variational formulation, which are undesired when dealing with fluid–structure interaction or black box codes. The proposed methodology makes possible to couple one-dimensional and three-dimensional fluid–structure interaction models, enforcing the continuity of mean total normal stress while just imposing flow rate data or even the classical Neumann boundary data to the models. This is accomplished by modifying an existing iterative algorithm, which is also able to account for the continuity of the vessel area, when required. Comparisons are performed to assess differences in the convergence properties of the algorithms when considering the continuity of mean normal stress and the continuity of mean total normal stress for a wide range of flow regimes. Finally, examples in the physiological regime are shown to evaluate the importance, or not, of considering the continuity of mean total normal stress in hemodynamics simulations.

Numerical Comparison and Calibration of Geometrical Multiscale Models for the Simulation of Arterial Flows

Arterial tree hemodynamics can be simulated by means of several models of different level of complexity, depending on the outputs of interest and the desired degree of accuracy. In this work, several numerical comparisons of geometrical multiscale models are presented with the aim of evaluating the benefits of such complex dimensionally-heterogeneous models compared to other simplified simulations. More precisely, we present flow rate and pressure wave form comparisons between three-dimensional patient-specific geometries implicitly coupled with one-dimensional arterial tree networks and (i) a full one-dimensional arterial tree model and (ii) stand-alone three-dimensional fluid–structure interaction models with boundary data taken from precomputed full one-dimensional network simulations. On a slightly different context, we also focus on the set up and calibration of cardiovascular simulations. In particular, we perform sensitivity analyses of the main quantities of interest (flow rate, pressure, and solid wall displacement) with respect to the parameters accounting for the elastic and viscoelastic responses of the tissues surrounding the external wall of the arteries. Finally, we also compare the results of geometrical multiscale models in which the boundary solid rings of the three-dimensional geometries are fixed, with respect to those where the boundary interfaces are scaled to enforce the continuity of the vessels size with the surrounding one-dimensional arteries.