Accuracy analysis of different higher-order Laplacian models of incompressible SPH method

2019 ◽  
Vol 37 (1) ◽  
pp. 181-202 ◽  
Author(s):  
Zohreh Heydari ◽  
Gholamreza Shobeyri ◽  
Seyed Hossein Ghoreishi Najafabadi
Keyword(s):  
Least Squares Method ◽  
Computational Cost ◽  
Higher Order ◽  
Computational Domain ◽  
Content Type ◽  
Incompressible Sph ◽  
Proposed Model ◽  
Particle Hydrodynamics ◽  
Moving Least Squares Method ◽  
Smoothed Particle

Purpose This paper aims to examine the accuracy of several higher-order incompressible smoothed particle hydrodynamics (ISPH) Laplacian models and compared with the classic model (Shao and Lo, 2003). Design/methodology/approach The numerical errors in solving two-dimensional elliptic partial differential equations using the Laplacian models are investigated for regular and highly irregular node distributions over a unit square computational domain. Findings The numerical results show that one of the Laplacian models, which is newly developed by one of the authors (Shobeyri, 2019) can get the smallest errors for various used node distributions. Originality/value The newly proposed model is formulated by the hybrid of the standard ISPH Laplacian model combined with Taylor expansion and moving least squares method. The superiority of the proposed model is significant when multi-resolution irregular node distributions commonly seen in adaptive refinement strategies used to save computational cost are applied.

Modeling of multi-phase flows and natural convection in a square cavity using an incompressible smoothed particle hydrodynamics

2015 ◽  
Vol 25 (3) ◽  
pp. 513-533 ◽  
Author(s):  
Abdelraheem Mahmoud Aly
Keyword(s):  
Natural Convection ◽  
Taylor Instability ◽  
Three Dimensions ◽  
Square Cavity ◽  
Content Type ◽  
Incompressible Sph ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Rayleigh Taylor Instability ◽  
Multi Phase

Purpose – Modeling of multi-phase flows for Rayleigh-Taylor instability and natural convection in a square cavity has been investigated using an incompressible smoothed particle hydrodynamics (ISPH) technique. In this technique, incompressibility is enforced by using SPH projection method and a stabilized incompressible SPH method by relaxing the density invariance condition is applied. The paper aims to discuss these issues. Design/methodology/approach – The Rayleigh-Taylor instability is introduced in two and three phases by using ISPH method. The author simulated natural convection in a square/cubic cavity using ISPH method in two and three dimensions. The solutions represented in temperature, vertical velocity and horizontal velocity have been studied with different values of Rayleigh number Ra parameter (103=Ra=105). In addition, characteristic based scheme in Finite Element Method is introduced for modeling the natural convection in a square cavity. Findings – The results for Rayleigh-Taylor instability and natural convection flow had been compared with the previous researches. Originality/value – Modeling of multi-phase flows for Rayleigh-Taylor instability and natural convection in a square cavity has been investigated using an ISPH technique. In ISPH method, incompressibility is enforced by using SPH projection method and a stabilized incompressible SPH method by relaxing the density invariance condition is introduced. The Rayleigh-Taylor instability is introduced in two and three phases by using ISPH method. The author simulated natural convection in a square/cubic cavity using ISPH method in two and three dimensions.

Incompressible smoothed particle hydrodynamics for MHD double-diffusive natural convection of a nanofluid in a cavity containing an oscillating pipe

2019 ◽  
Vol 30 (2) ◽  
pp. 882-917 ◽  
Author(s):  
Abdelraheem M. Aly
Keyword(s):  
Natural Convection ◽  
Smoothed Particle Hydrodynamics ◽  
Cavity Wall ◽  
Lagrangian Description ◽  
Content Type ◽  
Wide Range ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Incompressible Smoothed Particle Hydrodynamics ◽  
Double Diffusive

Purpose This paper aims to adopt incompressible smoothed particle hydrodynamics (ISPH) method to simulate MHD double-diffusive natural convection in a cavity containing an oscillating pipe and filled with nanofluid. Design/methodology/approach The Lagrangian description of the governing partial differential equations are solved numerically using improved ISPH method. The inner oscillating pipe is divided into two different pipes as an open and a closed pipe. The sidewalls of the cavity are cooled with a lower concentration C_c and the horizontal walls are adiabatic. The inner pipe is heated with higher concentration C_h. The analysis has been conducted for the two different cases of inner oscillating pipes under the effects of wide range of governing parameters. Findings It is found that a suitable oscillating pipe makes a well convective transport inside a cavity. Presence of the oscillating pipe has effects on the heat and mass transfer and fluid intensity inside a cavity. Hartman parameter suppresses the velocity and weakens the maximum values of the stream function. An increase on Hartman, Lewis and solid volume fraction parameters leads to an increase on average Nusselt number on an oscillating pipe and left cavity wall. Average Sherwood number on an oscillating pipe and left cavity wall decreases as Hartman parameter increases. Originality/value The main objective of this work is to study the MHD double-diffusive natural convection of a nanofluid in a square cavity containing an oscillating pipe using improved ISPH method.

Numerical investigation of anguilliform locomotion by the SPH method

2019 ◽  
Vol 30 (1) ◽  
pp. 328-346 ◽  
Author(s):  
Amin Rahmat ◽  
Hossein Nasiri ◽  
Marjan Goodarzi ◽  
Ehsan Heidaryan
Keyword(s):  
Drag Coefficient ◽  
Numerical Investigation ◽  
Sph Method ◽  
Content Type ◽  
Aquatic Locomotion ◽  
Wide Range ◽  
Particle Hydrodynamics ◽  
Dummy Particles ◽  
Smoothed Particle ◽  
Sph Algorithm

Purpose This paper aims to introduce a numerical investigation of aquatic locomotion using the smoothed particle hydrodynamics (SPH) method. Design/methodology/approach To model this problem, a simple improved SPH algorithm is presented that can handle complex geometries using updatable dummy particles. The computational code is validated by solving the flow over a two-dimensional cylinder and comparing its drag coefficient for two different Reynolds numbers with those in the literature. Findings Additionally, the drag coefficient and vortices created behind the aquatic swimmer are quantitatively and qualitatively compared with available credential data. Afterward, the flow over an aquatic swimmer is simulated for a wide range of Reynolds and Strouhal numbers, as well as for the amplitude envelope. Moreover, comprehensive discussions on drag coefficient and vorticity patterns behind the aquatic are made. Originality/value It is found that by increasing both Reynolds and Strouhal numbers separately, the anguilliform motion approaches the self-propulsion condition; however, the vortices show different pattern with these increments.

Modeling Hypervelocity Impacts Using Smoothed Particle Hydrodynamics

2018 ◽  
Author(s):  
M. Ganser ◽  
B. van der Linden ◽  
C. G. Giannopapa
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Large Deformations ◽  
Hypervelocity Impact ◽  
Density Fluctuations ◽  
Computational Domain ◽  
Simulation Tool ◽  
Hypervelocity Impacts ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact

Hypervelocity impacts occur in outer space where debris and micrometeorites with a velocity of 2 km/s endanger spacecraft and satellites. A proper shield design, e.g. a laminated structure, is necessary to increase the protection capabilities. High velocities result in massive damages. The resulting large deformations can hardly be tackled with mesh based discretization methods. Smoothed Particle Hydrodynamics (SPH), a Lagrangian meshless scheme, can resolve large topological changes whereas it still follows the continuous formulation. Derived by variational principles, SPH is able to capture large density fluctuations associated with hypervelocity impacts correctly. Although the impact region is locally limited, a much bigger domain has to be discretized because of strong outgoing pressure waves. A truncation of the computational domain is preferable to save computational power, but this leads to artificial reflections which influence the real physics. In this paper, hypervelocity impact (HVI) is modelled by means of basic conservation assumptions leading to the Euler equations of fluid dynamics accompanied by the Mie-Grueneisen equation of state. The newly developed simulation tool SPHlab presented in this work utilizes the discretization method smoothed particle hydrodynamics (SPH) to capture large deformations. The model is validated through a number of test cases. Different approaches are presented for non-reflecting boundaries in order to tackle artificial reflections on a computational truncated domain. To simulate an HVI, the leading continuous equations are derived and the simulation tool SPHlab is developed. The method of characteristics allows to define proper boundary fluxes by removing the inwards travelling information. One- and two-dimensional model problems are examined which show excellent absorption behaviour. An hypervelocity impact into a laminated shield is simulated and analysed and a simple damage model is introduced to model a spallation failure mode.

What makes users willing or hesitant to use Fintech?: the moderating effect of user type

2018 ◽  
Vol 118 (3) ◽  
pp. 541-569 ◽  
Author(s):  
Hyun-Sun Ryu
Keyword(s):  
Least Squares Method ◽  
Original Data ◽  
The Novel ◽  
Continuance Intention ◽  
Content Type ◽  
Factors Affecting ◽  
Proposed Model ◽  
Negative Effect ◽  
Partial Least Squares Method ◽  
Benefit And Risk

Purpose The purpose of this paper is to better understand why people are willing or hesitant to use Financial technology (Fintech) as well as to determine whether the effect of perceived benefits and risks of continuance intention differs depending on user types. Design/methodology/approach Original data were collected via a survey of 243 participants with Fintech usage experience. The partial least squares method was used to test the proposed model. Findings The results reveal that legal risk had the most negative effect on the Fintech continuance intention, while convenience had the strongest positive effect. Differences in specific benefit and risk impacts are found between early and late adopters. Originality/value This empirical study contributes to the novel understanding of the benefit and risk factors affecting the Fintech continuance intention.

Natural convection from heated fin shapes in a nanofluid-filled porous cavity using incompressible smoothed particle hydrodynamics

2019 ◽  
Vol 29 (12) ◽  
pp. 4569-4597 ◽  
Author(s):  
Abdelraheem M. Aly ◽  
Zehba Raizah ◽  
Mitsuteru Asai
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Smoothed Particle Hydrodynamics ◽  
Fluid Flows ◽  
Content Type ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Incompressible Smoothed Particle Hydrodynamics ◽  
Darcy Parameter

Purpose This study aims to focus on the numerical simulation of natural convection from heated novel fin shapes in a cavity filled with nanofluid and saturated with a partial layer of porous medium using improved incompressible smoothed particle hydrodynamics (ISPH) method. Design/methodology/approach The dimensionless of Lagrangian description for the governing equations were numerically solved using improved ISPH method. The current ISPH method was improved in term of wall boundary treatment by using renormalization kernel function. The effects of different novel heated (Tree, T, H, V, and Z) fin shapes, Rayleigh number Ra(103 – 106 ), porous height Hp (0.2-0.6), Darcy parameter Da(10−5 − 10−1 ) and solid volume fraction ϕ(0.0-0.05) on the heat transfer of nanofluid have been investigated. Findings The results showed that the variation on the heated novel fin shapes gives a suitable choice for enhancement heat transfer inside multi-layer porous cavity. Among all fin shapes, the H-fin shape causes the maximum stream function and Z-fin shape causes the highest value of average Nusselt number. The concentrations of the fluid flows in the nanofluid region depend on the Rayleigh and Darcy parameters. In addition, the penetrations of the fluid flows through porous layers are affected by porous heights and Darcy parameter. Originality/value Natural convection from novel heated fins in a cavity filled with nanofluid and saturated with a partial layer of porous medium have been investigated numerically using improved ISPH method.

scholarly journals A MULTI-NODE APPROACH TO SIMULATE THIN COASTAL STRUCTURES IN THE SPH CONTEXT

2017 ◽  
pp. 1
Author(s):  
Francesco Aristodemo ◽  
Domenico Davide Meringolo ◽  
Paolo Veltri
Keyword(s):  
Computational Cost ◽  
Variable Parameter ◽  
The Body ◽  
Solid Particles ◽  
Solid Boundary ◽  
Ghost Particle ◽  
Weakly Compressible ◽  
Boundary Treatment ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

We propose an improvement in modeling solid boundary conditions for 2D weakly-compressible Smoothed Particle Hydrodynamics (SPH) simulations for cases in which the thickness of the body is small compared to the desired particle size and the fluid surrounds the body from more than one side. Specifically, the fixed ghost particles technique developed by Marrone et al. (2011), based on interpolation nodes located within the fluid domain, is here extended to a multi-node approach. The fluid domain is thus divided into various sub-areas and an interpolation node for the considered solid particle is associated to every sub-area. Consequently, the solid particles present an array of values interpolated at different sub-areas for the same physical quantity. When a fluid particle located in a specific region interacts with a multi-node fixed ghost particle, the last assumes the field values interpolated in the reference area through the associated node. The present modeling allows to adopt a coarser spatial resolution to model the same physical problem, resulting in a reduction of the computational cost. The proposed solid boundary treatment is applied to horizontal decks and perforated wall-caisson breakwaters subjected to regular waves. In this context, an automatic hybrid diffusive formulation is introduced in order to prevent shock waves during water impacts and preserve the hydrostatic pressure. The formulation is obtained by defining a variable parameter detecting the occurrence of relevant density gradients induced by fluid impacts, resulting in an automatic switch between the two formulations.

scholarly journals A flash-based thermal simulation of scanning paths in LPBF additive manufacturing

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kamel Ettaieb ◽  
Sylvain Lavernhe ◽  
Christophe Tournier
Keyword(s):  
High Performance ◽  
Laser Scanning ◽  
Thermal Field ◽  
Computational Cost ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Content Type ◽  
Proposed Model ◽  
Scanning Path

Purpose This paper aims to propose an analytical thermal three-dimensional model that allows an efficient evaluation of the thermal effect of the laser-scanning path. During manufacturing by laser powder bed fusion (LPBF), the laser-scanning path influences the thermo-mechanical behavior of parts. Therefore, it is necessary to validate the path generation considering the thermal behavior induced by this process to improve the quality of parts. Design/methodology/approach The proposed model, based on the effect of successive thermal flashes along the scanning path, is calibrated and validated by comparison with thermal results obtained by FEM software and experimental measurements. A numerical investigation is performed to compare different scanning path strategies on the Ti6Al4V material with different stimulation parameters. Findings The simulation results confirm the effectiveness of the approach to simulate the thermal field to validate the scanning strategy. It suggests a change in the scale of simulation thanks to high-performance computing resources. Originality/value The flash-based approach is designed to ensure the quality of the simulated thermal field while minimizing the computational cost.

scholarly journals A solution to the overdamping problem when simulating dust–gas mixtures with smoothed particle hydrodynamics

2020 ◽  
Vol 495 (4) ◽  
pp. 3929-3934 ◽  
Author(s):  
Daniel J Price ◽  
Guillaume Laibe
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Computational Cost ◽  
Gas Mixtures ◽  
Strongly Coupled ◽  
Particle Pairs ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Spurious Oscillations ◽  
Slope Limiters ◽  
Additional Memory

ABSTRACT We present a fix to the overdamping problem found by Laibe & Price when simulating strongly coupled dust–gas mixtures using two different sets of particles using smoothed particle hydrodynamics. Our solution is to compute the drag at the barycentre between gas and dust particle pairs when computing the drag force by reconstructing the velocity field, similar to the procedure in Godunov-type solvers. This fixes the overdamping problem at negligible computational cost, but with additional memory required to store velocity derivatives. We employ slope limiters to avoid spurious oscillations at shocks, finding the van Leer Monotonized Central limiter most effective.

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