A DEM approach for simulating flexible beam elements with the Project Chrono core module in DualSPHysics

This work presents a novel approach for simulating elastic beam elements in DualSPHysics leveraging functions made available by the coupling with the Project Chrono library. Such numerical frameworks, belonging to the Meshfree Particle Methods family, stand out for several features, like complex multiphase phenomena, moving boundaries, and high deformations which are handled with relative ease and reasonable numerical stability and reliability. Based on a co-rotating rigid element structure and lumped elasticity, a cogent mathematical formulation, relying on the Euler–Bernoulli beam theory for the structural discretization, is presented and applied to simulating two-dimensional flexible beams with the discrete elements method (DEM) formulation. Three test cases are presented to validate the smoothed particle hydrodynamics-based (SPH) structure model in both accuracy and stability, starting from an equilibrium test, to the dynamic response, and closing with a fluid–structure interaction simulation. This work proves that the developed theory can be used within a Lagrangian framework, using the features provided by a DEM solver, overtaking the initial limitations, and hence applying the results of static theories to complex dynamic problems.Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia, Innovación y Universidades | Ref. IJCI-2017-32592Agencia Estatal de Investigación | Ref. PID2020-113245RB-I0

Regular wave seakeeping analysis of a planing hull by smoothed particle hydrodynamics: a comprehensive validation

In this work, the dynamics of a planing hull in regular head waves was investigated using the Smoothed Particle Hydrodynamics (SPH) meshfree method. The simulation of the interaction of such vessels with wave trains features several challenging characteristics, from the complex physical interaction, due to large dynamic responses, to the likewise heavy numerical workload. A novel numerical wave flume implemented within the SPH-based code DualSPHysics fulfills both demands, guaranteeing comparable accuracy with an established proprietary Computational Fluid Dynamics (CFD) solver without sharpening the computational load. The numerical wave flume uses ad hoc open-boundary conditions to reproduce the flow characteristics encountered by the hull during its motion, combining the current and waves while adjusting their properties with respect to the vessel’s experimental towing speed. It follows a relatively small three-dimensional domain, where the potentiality of the SPH method in modeling free-surface flows interacting with moving structures is unleashed. The results in different wave conditions show the feasibility of this novel approach, considering the overall good agreement with the experiments; hence, an interesting alternative procedure to simulate the seakeeping test in several marine conditions with bearable effort and satisfying accuracy is established.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RBI00Xunta de Galicia | Ref. ED431C 2021/44Ministerio de Ciencia e Innovación | Ref. TED2021-129479AI00Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia e Innovación | Ref. RYC2020-030197-

Coupling an SPH-based solver with an FEA structural solver to simulate free surface flows interacting with flexible structures

This work proposes a two-way coupling between a Smoothed Particle Hydrodynamics (SPH) model-based named DualSPHysics and a Finite Element Analysis (FEA) method to solve fluid–structure interaction (FSI). Aiming at having a computationally efficient solution via spatial adjustable resolutions for the two phases, the SPH-FEA coupling herein presented implements the Euler–Bernoulli beam model, based on a simplified model that incorporates axial and flexural deformations, to introduce a solid solver in the DualSPHysics framework. This approach is particularly functional and very precise for slender beam elements undergoing large displacements, and large deformations can also be experienced by the structural elements due to the non-linear FEA implementation via a co-rotational formulation. In this two-way coupling, the structure is discretised in the SPH domain using boundary particles on which the forces exerted by fluid phases are computed. Such forces are passed over to the FEA structural solver that updates the beam shape and, finally, the particle positions are subsequently reshuffled to represent the deformed shape at each time step. The SPH-FEA coupling is validated against four reference cases, which prove the model to be as accurate as other approaches presented in literature.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Ministerio de Ciencia e Innovación | Ref. TED2021-129479A-I00Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Universidade de Vigo/CISU

Coupling of an SPH-based solver with a multiphysics library

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGA two-way coupling between the Smoothed Particle Hydrodynamics-based (SPH) code with a multiphysics library to solve complex fluid-solid interaction problems is proposed. This work provides full access to the package for the use of this coupling by releasing the source code, completed with guidelines for its compilation and utilization, and self-contained template setups for practical uses of the novel implemented features, is provided here. The presented coupling expands the applicability of two different solvers allowing to simulate fluids, multibody systems, collisions with frictional contacts using either non-smooth contact (NSC) or smooth contact (SMC) methods, all integrated under the same framework. The fluid solver is the open-source code DualSPHysics, highly optimised for simulating free-surface phenomena and structure interactions, uniquely positioned as a general-purpose Computational Fluid Dynamics (CFD) software with a GPU-accelerated solver. Mechanical systems that comprise collision detection and/or multibody dynamics are solved by the multiphysics library Project Chrono, which uses a Discrete Element Method (DEM). Therefore, this SPH-DEM coupling approach can manage interactions between fluid and complex multibody systems with relative constraints, springs, or mechanical joints.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/337Ministerio de Ciencia e Innovación, Xunta de Galicia con fondos de la Unión Europea NextGenerationEU y el Fondo Europeo Marítimo y de Pesca | Ref. PRTR-C17.I

DualSPHysics modelling to analyse the response of Tetrapods against solitary wave

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe stability of Tetrapod armour units against solitary waves using Smoothed Particle Hydrodynamics (SPH) method is analysed in this work. To this purpose, the SPH-based DualSPHysics code was coupled with the multiphysics library Project Chrono. Tetrapod units are placed above a submerged mound. DualSPHysics solves the fluid-solid interaction, while Project Chrono solves the Tetrapod-mound interactions based on the contact and material properties of the block surface. The motion of the units during the simulation was compared with the physical model experiments where Tetrapods are made of mortar, and the mound is in PVC. The numerical results expressed as displacements of Tetrapods and damage ratio under different solitary waves are in reasonable agreement with the experiments, proving the capability of the DualSPHysics code to simulate challenging environments under the same numerical framework. The validated tool is then applied to study the stability for different coefficients of friction between mound and Tetrapods aiming at simulating the effects of different materials and surface roughness.Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Ministerio de Ciencia e Innovación | Ref. TED2021-129479A-I00Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2021/ 33

DualSPHysics: from fluid dynamics to multiphysics problems

DualSPHysics is a weakly compressible smoothed particle hydrodynamics (SPH) Navier–Stokes solver initially conceived to deal with coastal engineering problems, especially those related to wave impact with coastal structures. Since the first release back in 2011, DualSPHysics has shown to be robust and accurate for simulating extreme wave events along with a continuous improvement in efficiency thanks to the exploitation of hardware such as graphics processing units for scientific computing or the coupling with wave propagating models such as SWASH and OceanWave3D. Numerous additional functionalities have also been included in the DualSPHysics package over the last few years which allow the simulation of fluid-driven objects. The use of the discrete element method has allowed the solver to simulate the interaction among different bodies (sliding rocks, for example), which provides a unique tool to analyse debris flows. In addition, the recent coupling with other solvers like Project Chrono or MoorDyn has been a milestone in the development of the solver. Project Chrono allows the simulation of articulated structures with joints, hinges, sliders and springs and MoorDyn allows simulating moored structures. Both functionalities make DualSPHysics especially suited for the simulation of offshore energy harvesting devices. Lately, the present state of maturity of the solver goes beyond single-phase simulations, allowing multi-phase simulations with gas–liquid and a combination of Newtonian and non-Newtonian models expanding further the capabilities and range of applications for the DualSPHysics solver. These advances and functionalities make DualSPHysics an advanced meshless solver with emphasis on free-surface flow modelling.Ministerio de Ciencia, Innovación y Universidades | Ref. IJCI-2017-32592Ministerio de Economía, Industria y Competitividad | Ref. ENE2016-75074-C2-1-RXunta de Galicia | Ref. ED431C 2017/6

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research