A computational framework for the multiphysics simulation of microbubble-mediated sonothrombolysis using a forward-viewing intravascular transducer
- Authors: Tan, Zhi , Ooi, Ean Hin , Chiew, Yeong , Foo, Ji , Ng, Eddie , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: Ultrasonics Vol. 131, no. (2023), p.
- Full Text: false
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- Description: Sonothrombolysis is a technique that utilises ultrasound waves to excite microbubbles surrounding a clot. Clot lysis is achieved through mechanical damage induced by acoustic cavitation and through local clot displacement induced by acoustic radiation force (ARF). Despite the potential of microbubble-mediated sonothrombolysis, the selection of the optimal ultrasound and microbubble parameters remains a challenge. Existing experimental studies are not able to provide a complete picture of how ultrasound and microbubble characteristics influence the outcome of sonothrombolysis. Likewise, computational studies have not been applied in detail in the context of sonothrombolysis. Hence, the effect of interaction between the bubble dynamics and acoustic propagation on the acoustic streaming and clot deformation remains unclear. In the present study, we report for the first time the computational framework that couples the bubble dynamic phenomena with the acoustic propagation in a bubbly medium to simulate microbubble-mediated sonothrombolysis using a forward-viewing transducer. The computational framework was used to investigate the effects of ultrasound properties (pressure and frequency) and microbubble characteristics (radius and concentration) on the outcome of sonothrombolysis. Four major findings were obtained from the simulation results: (i) ultrasound pressure plays the most dominant role over all the other parameters in affecting the bubble dynamics, acoustic attenuation, ARF, acoustic streaming, and clot displacement, (ii) smaller microbubbles could contribute to a more violent oscillation and improve the ARF simultaneously when they are stimulated at higher ultrasound pressure, (iii) higher microbubbles concentration increases the ARF, and (iv) the effect of ultrasound frequency on acoustic attenuation is dependent on the ultrasound pressure. These results may provide fundamental insight that is crucial in bringing sonothrombolysis closer to clinical implementation. © 2023 Elsevier B.V.
A mesoscale modelling approach coupling SBFEM, continuous damage phase-field model and discrete cohesive crack model for concrete fracture
- Authors: Yu, Kelai , Yang, Zhenjun , Li, Hui , Ooi, Ean Tat , Li, Shangming , Liu, GuoHua
- Date: 2023
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 278, no. (2023), p.
- Full Text: false
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- Description: This study develops an innovative numerical approach for simulating complex mesoscale fracture in concrete. In this approach, the concrete meso-structures are generated using a random aggregate generation and packing algorithm. Each aggregate is modelled by a single scaled boundary finite element method (SBFEM) based polygon with the boundary discretized only. The damage and fracture in the mortar is simulated by the continuous damage phase-field regularized cohesive zone model (PF-CZM), and the aggregate-mortar interfaces are modelled by zero-thickness cohesive interface elements (CIEs) with nonlinear softening separation-traction laws. This new approach thus takes full advantages of different methods, including the semi-analytical accuracy and high flexibility in mesh generation and transition of SBFEM, the mesh and length-scale independence of PF-CZM, and the ease-of-use of CIEs in modelling discrete interfacial fracture. These advantages are demonstrated by successful simulations of a few 2D and 3D benchmark examples in mode-I and mixed-mode fracture. © 2022 Elsevier Ltd
Adaptive phase-field modelling of fracture propagation in poroelastic media using the scaled boundary finite element method
- Authors: Wijesinghe, Dakshith , Natarajan, Sundararajan , You, Greg , Khandelwal, Manoj , Dyson, Ashley , Song, Chongmin , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: Computer Methods in Applied Mechanics and Engineering Vol. 411, no. (2023), p.
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- Description: A scaled boundary finite element-based phase field formulation is proposed to model two-dimensional fracture in saturated poroelastic media. The mechanical response of the poroelastic media is simulated following Biot's theory, and the fracture surface evolution is modelled according to the phase field formulation. To avoid the application of fine uniform meshes that are constrained by the element size requirement when adopting phase field models, an adaptive refinement strategy based on quadtree meshes is adopted. The unique advantage of the scaled boundary finite element method is conducive to the application of quadtree adaptivity, as it can be directly formulated on quadtree meshes without the need for any special treatment of hanging nodes. Efficient computation is achieved by exploiting the unique patterns of the quadtree cells. An appropriate scaling is applied to the relevant matrices and vectors according the physical size of the cells in the mesh during the simulations. This avoids repetitive calculations of cells with the same configurations. The proposed model is validated using a benchmark with a known analytical solution. Numerical examples of hydraulic fractures driven by the injected fluid in cracks are modelled to illustrate the capabilities of the proposed model in handling crack propagation problems involving complex geometries. © 2023 The Author(s)
An in silico assessment on the potential of using saline infusion to overcome non-confluent coagulation zone during two-probe, no-touch bipolar radiofrequency ablation of liver cancer
- Authors: Yip, Wai , Kho, Antony , Ooi, Ean , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: Medical Engineering and Physics Vol. 112, no. (2023), p.
- Full Text: false
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- Description: No-touch bipolar radiofrequency ablation (bRFA) is known to produce incomplete tumour ablation with a ‘butterfly-shaped’ coagulation zone when the interelectrode distance exceeds a certain threshold. Although non-confluent coagulation zone can be avoided by not implementing the no-touch mode, doing so exposes the patient to the risk of tumour track seeding. The present study investigates if prior infusion of saline into the tissue can overcome the issues of non-confluent or butterfly-shaped coagulation. A computational modelling approach based on the finite element method was carried out. A two-compartment model comprising the tumour that is surrounded by healthy liver tissue was developed. Three cases were considered; i) saline infusion into the tumour centre; ii) one-sided saline infusion outside the tumour; and iii) two-sided saline infusion outside the tumour. For each case, three different saline volumes were considered, i.e. 6, 14 and 22 ml. Saline concentration was set to 15% w/v. Numerical results showed that saline infusion into the tumour centre can overcome the butterfly-shaped coagulation only if the infusion volume is sufficient. On the other hand, one-sided infusion outside the tumour did not overcome this. Two-sided infusion outside the tumour produced confluent coagulation zone with the largest volume. Results obtained from the present study suggest that saline infusion, when carried out correctly, can be used to effectively eradicate liver cancer. This presents a practical solution to address non-confluent coagulation zone typical of that during two-probe bRFA treatment. © 2023 IPEM
Construction of generalized shape functions over arbitrary polytopes based on scaled boundary finite element method's solution of Poisson's equation
- Authors: Xiao, B. , Natarajan, Sundararajan , Birk, Carolin , Ooi, Ean Hin , Song, Chongmin , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: International Journal for Numerical Methods in Engineering Vol. 124, no. 17 (2023), p. 3603-3636
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- Description: A general technique to develop arbitrary-sided polygonal elements based on the scaled boundary finite element method is presented. Shape functions are derived from the solution of the Poisson's equation in contrast to the well-known Laplace shape functions that are only linearly complete. The application of the Poisson shape functions can be complete up to any specific order. The shape functions retain the advantage of the scaled boundary finite element method allowing direct formulation on polygons with arbitrary number of sides and quadtree meshes. The resulting formulation is similar to the finite element method where each field variable is interpolated by the same set of shape functions in parametric space and differs only in the integration of the stiffness and mass matrices. Well-established finite element procedures can be applied with the developed shape functions, to solve a variety of engineering problems including, for example, coupled field problems, phase field fracture, and addressing volumetric locking in the near-incompressibility limit by adopting a mixed formulation. Application of the formulation is demonstrated in several engineering problems. Optimal convergence rates are observed. © 2023 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.
Image based probabilistic slope stability analysis of soil layer interface fluctuations with Brownian bridges
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Ooi, Ean Tat
- Date: 2023
- Type: Text , Journal article
- Relation: Engineering Failure Analysis Vol. 148, no. (2023), p.
- Full Text: false
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- Description: Accurate interpretation of stratigraphic profiles, the phreatic surface and the spatial variability of geomaterials are essential to produce representative behaviour of geomechanical systems through numerical simulations. When considering slope stability, variations in soil layer boundaries and the phreatic surface may result in misleading metrics such as the Factor of Safety (FoS) and the Probability of Failure (PoF). This paper presents an image-based technique for generating continuous stratigraphic profiles, including random fluctuations based on Brownian motion. Brownian bridges are used to produce random walks between known points on both soil layer boundaries and the phreatic level that overlap with the slope profile image. Quadtree decomposition is used to discretise the stratigraphy and the phreatic level through an automatic process using generated digital images for mesh generation while also integrating material properties. The Scaled Boundary Finite Element (SBFEM) is used to analyse the slope stability problem. Images based on random walks along an unknown stratigraphic material boundary and the phreatic surface are randomly generated and have many random possibilities, which are used to undertake probabilistic analysis to obtain PoF. This process is complex when using numerical methods, such as the Finite Element Method, as it requires mesh generation from different slope profiles with alternating material interfaces at each probabilistic instance. When the Scaled Boundary Finite Element Method is applied, probabilistic numerical analyses can be fully automated for randomly generated material interfaces. The feasibility of the proposed method is illustrated through several cases of a slope with multiple material layers, in addition to a slope incorporating a Brownian bridge phreatic surface formulation. © 2023 Elsevier Ltd
Modeling cyclic crack propagation in concrete using the scaled boundary finite element method coupled with the cumulative damage-plasticity constitutive law
- Authors: Alrayes, Omar , Könke, Carsten , Ooi, Ean Tat , Hamdia, Khader
- Date: 2023
- Type: Text , Journal article
- Relation: Materials Vol. 16, no. 2 (2023), p.
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- Description: Many concrete structures, such as bridges and wind turbine towers, fail mostly due to the fatigue rapture and bending, where the cracks are initiated and propagate under cyclic loading. Modeling the fracture process zone (FPZ) is essential to understanding the cracking behavior of heterogeneous, quasi-brittle materials such as concrete under monotonic and cyclic actions. The paper aims to present a numerical modeling approach for simulating crack growth using a scaled boundary finite element model (SBFEM). The cohesive traction law is explored to model the stress field under monotonic and cyclic loading conditions. In doing so, a new constitutive law is applied within the cohesive response. The cyclic damage accumulation during loading and unloading is formulated within the thermodynamic framework of the constitutive concrete model. We consider two common problems of three-point bending of a single-edge-notched concrete beam subjected to different loading conditions to validate the developed method. The simulation results show good agreement with experimental test measurements from the literature. The presented analysis can provide a further understanding of crack growth and damage accumulation within the cohesive response, and the SBFEM makes it possible to identify the fracture behavior of cyclic crack propagation in concrete members. © 2023 by the authors.
Transient thermoelastic fracture analysis of functionally graded materials using the scaled boundary finite element method
- Authors: Iqbal, M. , Birk, Carolin , Ooi, Ean Tat , Natarajan, Sundararajan , Gravenkamp, Hauke
- Date: 2023
- Type: Text , Journal article
- Relation: Theoretical and Applied Fracture Mechanics Vol. 127, no. (2023), p.
- Full Text: false
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- Description: To model fracture in functionally graded materials (FGMs), the scaled boundary finite element method (SBFEM) is extended to examine the effects of fully coupled transient thermoelasticity. Previously developed SBFEM supplementary shape functions are utilized to model thermal stresses. The spatial variation of thermal and mechanical properties of FGMs are approximated by polynomial functions facilitating the semi-analytical evaluation of coefficient matrices. The dynamic stress intensity factors (SIFs) are also evaluated semi-analytically from their definitions without the need for additional post-processing. Scaled boundary polygon elements are employed to facilitate the meshing of complex crack geometries. Both isotropic and orthotropic materials with different material gradation functions are considered. To study the transient effects of thermoelasticity on fracture parameters, several numerical examples with different crack configurations and boundary conditions are considered. The current approach is validated by comparing the results of dynamic SIFs with available reference solutions. © 2023 Elsevier Ltd
A computational framework to simulate the thermochemical process during thermochemical ablation of biological tissues
- Authors: Mak, Nguoy , Ooi, Ean H. , Lau, Ee , Ooi, Ean Tat , Pamidi, N. , Foo, Ji , Mohd Ali, Ahmad
- Date: 2022
- Type: Text , Journal article
- Relation: Computers in Biology and Medicine Vol. 145, no. (2022), p.
- Full Text: false
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- Description: Thermochemical ablation (TCA) is a thermal ablation therapy that utilises heat released from acid-base neutralisation reaction to destroy tumours. This procedure is a promising low-cost solution to existing thermal ablation treatments such as radiofrequency ablation (RFA) and microwave ablation (MWA). Studies have demonstrated that TCA can produce thermal damage that is on par with RFA and MWA when employed properly. Nevertheless, TCA remains a concept that is tested only in a few animal trials due to the risks involved as the result of uncontrolled infusion and incomplete acid-base reaction. In this study, a computational framework that simulates the thermochemical process of TCA is developed. The proposed framework consists of three physics, namely chemical flow, neutralisation reaction and heat transfer. An important parameter in the TCA framework is the neutralisation reaction rate constant, which has values in the order of 108 m3/(mol
Adaptive modelling of dynamic brittle fracture - a combined phase field regularized cohesive zone model and scaled boundary finite element approach
- Authors: Natarajan, Sundararajan , Ooi, Ean Tat , Birk, Carolin , Song, Chongmin
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal of Fracture Vol. 236, no. 1 (2022), p. 87-108
- Full Text: false
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- Description: Based on the error indicator computed from the scaled boundary equations, a quadtree based adaptive phase-field method is proposed for dynamic brittle fracture problems in isotropic material using the scaled boundary finite element method (SBFEM). The use of SBFEM alleviates the need for additional: (a) constraints to handle hanging nodes resulting from adaptive refinement and (b) post-processing techniques. Three representative examples are solved to demonstrate the efficiency of the proposed approach. From the numerical study, it is opined that the proposed approach requires an order of magnitude fewer degrees of freedom when compared to uniform refinement and can capture the crack morphology under dynamic loading conditions without compromising accuracy. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
An in silico derived dosage and administration guide for effective thermochemical ablation of biological tissues with simultaneous injection of acid and base
- Authors: Mak, Nguoy , Ooi, Ean , Lau, Ee , Ooi, Ean Tat , Pamidi, Narendra , Foo, Ji , Mohd Ali, Ahmad
- Date: 2022
- Type: Text , Journal article
- Relation: Computer Methods and Programs in Biomedicine Vol. 227, no. (2022), p.
- Full Text: false
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- Description: Background and objectives: Thermochemical ablation (TCA) is a thermal ablation technique involving the injection of acid and base, either sequentially or simultaneously, into the target tissue. TCA remains at the conceptual stage with existing studies unable to provide recommendations on the optimum injection rate, and reagent concentration and volume. Limitations in current experimental methodology have prevented proper elucidation of the thermochemical processes inside the tissue during TCA. Nevertheless, the computational TCA framework developed recently by Mak et al. [Mak et al., Computers in Biology and Medicine, 2022, 145:105494] has opened new avenues in the development of TCA. Specifically, a recommended safe dosage is imperative in driving TCA research beyond the conceptual stage. Methods: The aforesaid computational TCA framework for sequential injection was applied and adapted to simulate TCA with simultaneous injection of acid and base at equimolar and equivolume. The developed framework, which describes the flow of acid and base, their neutralisation, the rise in tissue temperature and the formation of thermal damage, was solved numerically using the finite element method. The framework will be used to investigate the effects of injection rate, reagent concentration, volume and type (weak/strong acid-base combination) on temperature rise and thermal coagulation formation. Results: A higher injection rate resulted in higher temperature rise and larger thermal coagulation. Reagent concentration of 7500 mol/m3 was found to be optimum in producing considerable thermal coagulation without the risk of tissue overheating. Thermal coagulation volume was found to be consistently larger than the total volume of acid and base injected into the tissue, which is beneficial as it reduces the risk of chemical burn injury. Three multivariate second-order polynomials that express the targeted coagulation volume as functions of injection rate and reagent volume, for the weak-weak, weak-strong and strong-strong acid-base combinations were also derived based on the simulated data. Conclusions: A guideline for a safe and effective implementation of TCA with simultaneous injection of acid and base was recommended based on the numerical results of the computational model developed. The guideline correlates the coagulation volume with the reagent volume and injection rate, and may be used by clinicians in determining the safe dosage of reagents and optimum injection rate to achieve a desired thermal coagulation volume during TCA. © 2022 Elsevier B.V.
Automatic mesoscopic fracture modelling of concrete based on enriched SBFEM space and quad-tree mesh
- Authors: Jiang, Shouyan , Sun, Liguo , Ooi, Ean Tat , Ghaemian, Mohsen , Du, Chengbin
- Date: 2022
- Type: Text , Journal article
- Relation: Construction and Building Materials Vol. 350, no. (2022), p.
- Full Text: false
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- Description: A novel approach for mesoscale modelling of concrete composites is proposed by combining enriched scaled boundary finite element methods with quad-tree mesh. The concrete meso-structures are comprised of randomly distributed aggregates, mortar matrix, and interface transition zone. An improved random aggregate generation technique is developed to construct digital images of mesoscale concrete models. Based on the quadtree decomposition algorithm, meshes can be generated automatically from the digital images of concrete mesostructure. The whole mesh generation process is highly efficient without any artificial interference and eliminates the issue of hanging nodes faced by standard finite elements. Additionally, local remeshing is unnecessary as crack propagates. Three numerical examples are modelled to demonstrate the performance of the proposed approach, and the effects of aggregate area fraction on the mechanical properties of concrete composites are also discussed. © 2022 Elsevier Ltd
Communication-a-fast and accurate numerical technique for impedance spectroscopy of microstructures
- Authors: Swaminathan, Narasimhan , Natarajan, Sundararajan , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: Journal of the Electrochemical Society Vol. 169, no. 2 (2022), p.
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- Description: The polygonal finite element method (PFEM) is proposed as a fast and accurate technique to simulate the impedance spectroscopy (IS) of polycrystalline materials. While conventional finite element method (FEM) requires explicit meshing of the grains and grain boundaries, in PFEM each region can be treated as an element. We demonstrate that the number of degrees of freedom in PFEM can be lower by a factor of 30 when compared to FEM, thus speeding up simulations by a factor of 3.5. A simple example demonstrates the use of PFEM to generate IS on samples with various grain boundary widths. © 2022 The Author(s).
Development of the scaled boundary finite element method for image-based slope stability analysis
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Song, Chongmin , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: Computers and Geotechnics Vol. 143, no. (2022), p.
- Full Text: false
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- Description: This paper presents a numerical technique for geotechnical slope stability analysis, integrating digital image meshing with the scaled boundary finite element method, allowing site conditions such as complex stratigraphies, surface and internal geometry evolution to be simulated in a robust and straightforward procedure. The quadtree decomposition technique is used to automatically discretise the geometry directly from digital images using pixel information to accurately capture boundaries with fine-scale elements. The process allows complex numerical models to be generated from cross-section images of slopes, capitalising on the combination of the scaled boundary finite element method and quadtree meshing. The spatial distribution of the soil material properties can be represented by the colour of each pixel. A mapping technique is developed to integrate these parameters into the computational mesh. The feasibility of the proposed method is presented through case study simulations of an active large Australian open-pit mine, considering various aspects of complex features such as geometry, stratigraphy and material behaviour. © 2021
Fracture analysis of cracked magneto-electro-elastic functionally graded materials using scaled boundary finite element method
- Authors: Nguyen, Duc , Javidan, Fatemeh , Attar, Mohammadmahdi , Natarajan, Sundararajan , Yang, Zhenjun , Ooi, Ean Hin , Song, Chongmin , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: Theoretical and Applied Fracture Mechanics Vol. 118, no. (2022), p.
- Full Text: false
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- Description: This paper develops the scaled boundary finite element method to analyse fracture of functionally graded magneto-electro-elastic materials. Polygon meshes are employed to discretize the domain. No asymptotic solution, local mesh refinement or other special treatments around a crack tip are required to calculate the intensity factors. When the material gradients of the coefficients in the constitutive matrix are expressed as a series of power functions of the scaled boundary coordinates, the stiffness matrices can be integrated analytically. The formulation enables the generalized intensity factors of stress, electric displacement and magnetic induction fields along the radial direction to be represented analytically. This permits the calculation of the generalized intensity factors directly from the scaled boundary finite element solution of the singular stress, electric displacement and magnetic induction fields by following the standard stress recovery procedures in the finite element method. Several numerical benchmarks are presented to validate the proposed technique with the results reported in the literature. © 2022 Elsevier Ltd
Simultaneous slope design optimisation and stability assessment using a genetic algorithm and a fully automatic image-based analysis
- Authors: Wijesinghe, Dakshith , Dyson, Ashley , You, Greg , Khandelwal, Manoj , Song, Chongmin , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal for Numerical and Analytical Methods in Geomechanics Vol. 46, no. 15 (2022), p. 2868-2892
- Full Text: false
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- Description: Mine slope design is a complex task that requires consideration of geotechnical analysis, structural stability, economics and the environment. Economic factors usually drive mine slope design, particularly in the case of open-pit designs, where the process of steepening slope walls by several degrees can have profound financial implications. Due to the risks associated with catastrophic slope collapse, slope stability analysis is an integral component of open-pit engineering projects. However, initial design concepts and geotechnical assessments are often considered separately. In this study, a technique is developed that combines the scaled boundary finite element method (SBFEM) with genetic algorithms (GAs) to simultaneously perform slope stability analysis and optimise the slope profile. The iterative design approach optimises characteristics of the slope profile such as the slope height, width, angle and number of benches while ensuring the factor of safety (FoS) remains above a threshold value. A salient feature of the technique is the ability to automatically address the modifications to the geometry of the slope by updating the digital images used in the analysis to assess the stability of each instance in the optimisation process and determine the optimum slope geometry. The results highlight the application of the developed technique to determine appropriate slope excavation designs as well as slope backfilling scenarios. The method is exemplified in several cases where complex stratigraphies and spatially variable materials are considered. As such, the GA-driven slope design process conveys an optimised, automated tool, combining mine slope design and slope stability analysis. © 2022 John Wiley & Sons Ltd.
The effects of vaporisation, condensation and diffusion of water inside the tissue during saline-infused radiofrequency ablation of the liver: A computational study
- Authors: Kho, Antony , Ooi, Ean , Foo, Ji , Ooi, Ean Tat
- Date: 2022
- Type: Text , Journal article
- Relation: International journal of heat and mass transfer Vol. 194, no. (2022), p. 123062
- Full Text: false
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- Description: •Effect of vaporisation, condensation & diffusion on saline-infused RFA was studied.•Condensation significantly affects the prediction of the RFA treatment outcome.•Water diffusion is insignificant when compared to condensation.•The model serves as benchmark for the accurate modelling of saline-infused RFA. [Display omitted] Saline-infused radiofrequency ablation (RFA) is a thermal ablation technique that combines saline infusion and Joule heating to destroy cancer tissues. During treatment, the intense heat generated can cause water from the infused saline and inside the tissue to vaporise. Conventionally, the effects of vaporisation have been modelled by adopting the apparent heat capacity method. However, this approach does not account for the loss of water content during vaporisation, which raises questions on its accuracy, primarily because of the large water content present during saline-infused RFA. To address this, the present study proposes an alternative approach to model vaporisation effects during saline-infused RFA. The approach adopts and modifies the water fraction method to account for the effects of vaporisation, condensation and diffusion of water inside the tissue during saline-infused RFA. The framework was compared against the commonly used apparent heat capacity method through numerical simulations carried out on 3D finite element models of the liver. Results indicated that unlike condensation, the role of diffusion of water during saline-infused RFA was not as significant as condensation, where the latter was found to affect the ablation process. With the water fraction method, there was a trend of exponential decrease in tissue electrical conductivity with time, which ultimately led to the prediction of smaller coagulation volume than that of the apparent heat capacity method.
Thermoelastic fracture analysis of functionally graded materials using the scaled boundary finite element method
- Authors: Iqbal, M. , Birk, Carolin , Ooi, Ean Tat , Pramod, Aladurthi , Natarajan, Sundararajan , Gravenkamp, Hauke , Song, Chongmin
- Date: 2022
- Type: Text , Journal article
- Relation: Engineering Fracture Mechanics Vol. 264, no. (2022), p.
- Full Text: false
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- Description: The scaled boundary finite element method is extended to model fracture in functionally graded materials (FGM) under coupled thermo-mechanical loads. The governing equations of coupled thermo-mechanical equilibrium are discretized using scaled boundary shape functions enriched with the thermal load terms. The material gradient is modeled as a series of power functions, and the stiffness matrix is calculated semi-analytically. Stress intensity factors and T−stress are directly calculated from their definition without any need for additional post-processing techniques. Arbitrary-sided polygon elements are employed for flexible mesh generation. Several numerical examples for isotropic and orthotropic FGMs are presented to validate the proposed technique. © 2022 Elsevier Ltd
A comparative study of numerical approaches for the computation of effective properties of micro‐heterogeneous materials
- Authors: Assaf, Rama , Scheunemann, Lisa , Birk, Carolin , Schröder, Jörg , Ooi, Ean Tat
- Date: 2021
- Type: Text , Journal article
- Relation: Proceedings in applied mathematics and mechanics Vol. 20, no. 1 (2021), p. n/a
- Full Text: false
- Reviewed:
- Description: The paper presents a comparative study of the finite element method (FEM) and the scaled boundary finite element method (SBFEM) for the numerical evaluation of the volume‐averaged stress of composites. Two‐dimensional meso‐scale models of concrete represented by digital images and discretized using an automatic mesh generation algorithm are considered. The different computational approaches are discussed and compared with respect to accuracy and efficiency for both scenarios.
A direct time-domain procedure for the seismic analysis of dam–foundation–reservoir systems using the scaled boundary finite element method
- Authors: Qu, Yanling , Chen, Denghong , Liu, Lei , Ooi, Ean Tat , Eisenträger, Sascha , Song, Chongmin
- Date: 2021
- Type: Text , Journal article
- Relation: Computers and Geotechnics Vol. 138, no. (2021), p.
- Full Text: false
- Reviewed:
- Description: In this paper, a direct time-domain procedure for the seismic analysis of dam–reservoir–foundation interactions is presented based on the scaled boundary finite element method (SBFEM). The SBFEM is a semi-analytical method and requires the discretization of boundary only. The geometric complexity in the bounded dam–reservoir–foundation system is easily handled in the SBFEM using quadtree meshes where each structural component can be discretized independently. The elastic wave fields in the unbounded foundation are rigorously captured through SBFE solutions in terms of displacement unit-impulse response functions, while the acoustic wave propagation in the semi-infinite reservoir is modelled by the SBFE-based doubly asymptotic open boundary. The input of seismic excitations is addressed by incorporating the Domain Reduction Method (DRM) into the SBFEM. Cracks are modelled efficiently and accurately by combining the SBFEM and quadtree meshes. The accuracy and efficiency of the proposed methodology is investigated by studying several benchmarks, Pine Flat dam and Jin'anqiao dam. © 2021 Elsevier Ltd