Ahmad Shakibaeinia

• Ph.D., P.Eng.
• Professor at Polytechnique Montréal

Channel confluence is one of the important features of each river system and some hydraulic structures. The features that can dominantly control flow characteristics in a confluence are confluence angle, discharge, width ratios, and Froude number of flow. Several research studies have been conducted however a comprehensive three-dimensional (3-D) n...

Discharge of sand into water can be modeled as the multiphase flow of a non-Newtonian and a Newtonian fluid by treating the granular material as a continuum. The numerical modeling of this article is on the basis of the latest generation of computational methods, the mesh-free Lagrangian (particle) methods. In these methods, the solution domain is...

By treating the multiphase system as a multi-density multi-viscosity fluid, a straightforward model has been proposed in this paper based on the Moving Particle Semi-implicit (MPS) mesh-free particle method for incompressible multiphase flow. The weakly-compressible MPS (WC-MPS) formulation (developed by the authors) is used to solve a single set o...

A mesh-free particle method, based on the moving particle semi-implicit (MPS) interaction model, has been developed for the simulation of two-dimensional open-boundary free-surface flows. The incompressibility model in the original MPS has been replaced with a weakly incompressible model. The effect of this replacement on the efficiency and accurac...

As a Lagrangian particle method, the moving particle semi-implicit (MPS) method has demonstrated distinct advantages in addressing problems involving large deformations of free surfaces and interfaces. This paper comprehensively reviews the MPS method, including its development, advancements, and applications within ocean engineering. The article f...

The interaction of water flow, ice, and structures is common in fluvial ice processes, particularly around Ice Control Structures (ICSs) that are used to manage and prevent ice jam floods. To evaluate the effectiveness of ICSs, it is essential to understand the complex interaction between water flow, ice and the structure. Numerical modeling is a v...

Landslides, which are the sources of most catastrophic natural disasters, can be subaerial (dry), submerged (underwater), or semi‐submerged (transitional). Semi‐submerged or transitional landslides occur when a subaerial landslide enters water and turns to submerged condition. Predicting the behavior of such a highly dynamic multi‐phase granular fl...

Fully Lagrangian methods such as the moving particle semi-implicit (MPS) have proven better performance over the traditional mesh-based methods in handling highly dynamic flows with large deformations such as those witnessed at the occurrence of tailings dam breaches. Nevertheless, their applications to large-scale simulations are rare. Among the l...

Over the past decades, a variety of ice control structures (ICSs) have been designed and built, but to date, there has been no systematic evaluation of the effectiveness of these structures. To achieve this objective, first an understanding of the interaction between different ice processes and the ICSs must be established. For this purpose, a tota...

Over the past decades, several Computational Fluid Dynamics (CFD) models have been developed to simulate the interaction of ice with structures. The applicability of these models remained very limited due to the computational time and the difficulty of simulating such dynamic physical phenomena. In recent years several advancements in computing cap...

Granular dynamics driven by fluid flow is ubiquitous in many industrial and natural processes, such as fluvial and coastal sediment transport. Yet, their complex multiphysics and multi- cale nature challenge numerical models’ accuracy and efficiency. Here, we develop a new multi-resolution mesh-free particle method, based on an enhanced weakly-comp...

Rapid advances in computational power and numerical techniques in recent years have provided us with the opportunity to solve challenging problems in many science and engineering fields [...]

Ice jams in the cold region rivers can alter the river hydrodynamics, cause flood events, damage the fluvial infrastructures, and thus, affect the ecosystems. The complex multiphysics interaction of ice floes with water flows, hydraulic structures, and the morphologic characteristics of the watercourse challenge the prediction of such phenomena. Th...

Vortex formation under unsteady flow conditions in a draining reservoir is studied. Considering the capabilities of mesh-free Lagrangian numerical methods in the simulation of highly deformed free surfaces, the smoothed-particle hydrodynamics approach is employed. The results of this numerical model are validated with the experimental data of the c...

This paper proposes and validates two new particle regularization techniques for the Smoothed Particle Hydrodynamics (SPH) numerical method to improve its stability and accuracy for free surface flow simulations. We introduce a general form of the Dynamic pair-wise Particle Collision (DPC) regularization technique that we recently proposed in the c...

Granular dynamics driven by fluid flow is ubiquitous in many industrial and natural processes, such as fluvial and coastal sediment transport. Yet, their complex multiphysics nature challenges the accuracy and efficiency of numerical models. Here, we study the dynamics of rapid fluid-driven granular erosion through a mesh-free particle method based...

Within the present work, the dam break flow over dry and wet beds are investigated experimentally, aiming to provide up-to-date data set and deeper insight into the morphology and hydrodynamics of the dam-break flood wave. The experiments are performed in a smooth prismatic channel with a rectangular cross-section. The wave profile and the downstre...

Sub-aerial (dry) and submerged dense granular collapses are studied by means of a three-phase unresolved computational fluid dynamics-discrete element method (CFD-DEM) numerical model. Physical experiments are also performed to provide data for validation and further analysis. Validations show good compatibility between the numerical and experiment...

This paper proposes and validates two new particle regularization techniques for the Smoothed Particle Hydrodynamics (SPH) numerical method to improve its stability and accuracy for free surface flow simulations. We introduce a general form of the Dynamic pair-wise Particle Collision (DPC) regularization technique that we recently proposed in the c...

Continuum-based particle methods, like SPH and MPS, employ particle regularization techniques to improve the non-uniform particle distribution and therefore enhance stability and accuracy. The Particle Shifting (PS) algorithm is one of the most adopted particle regularization techniques. Recently, we [1] proposed an alternative technique, called th...

We develop and validate a three-dimensional particle method based on an Enhanced Weakly- Compressible MPS approach for modeling immersed dense granular flows. For this purpose, we adopt a unified and generalized rheological model, using a regularized visco-inertial rheology, for all regimes of multiphase granular flow. Moreover, we propose a new co...

A movie of the 3D water dam break against a rigid obstacle simulated with the Enhanced WC-MPS method. The Dynamic pair-wise Particle Collision method acts as the particle regularization technique for ensuring numerical stability of the violent flow.

This paper develops and evaluates a novel 3D fully-Lagrangian (particle-based) numerical model, based on the hybrid discrete element method (DEM) and moving particle semi-implicit (MPS) mesh-free techniques, for modeling the highly-dynamic ice-wave interactions. Both MPS and DEM belong to mesh-free Lagrangian (particle) techniques. The model consid...

This paper develops and evaluates a novel three-dimensional fully-Lagrangian (particle-based) numerical model, based on the hybrid discrete element method (DEM) and moving particle semi-implicit (MPS) mesh-free techniques, for modeling the highly-dynamic ice-wave interactions. Both MPS and DEM belong to mesh-free Lagrangian (particle) techniques. T...

The main objective of the current work is to enhance consistency and capabilities of Moving Particle Semi-implicit (MPS) method for simulating a wide range of free-surface flows and convection heat transfer. For this purpose, two novel high-order gradient and Laplacian operators are derived from the Taylor series expansion and are applied for the d...

This paper develops a consistent particle method for capturing the highly non-linear behavior of violent free-surface flows, based on an Enhanced Weakly Compressible Moving Particle Semi-implicit (EWC-MPS) method. It pays special attention to the evaluation and improvement of two particle regularization techniques, namely, pairwise particle collisi...

This paper develops a consistent particle method for capturing the highly non-linear behavior of violent free-surface flows, based on an Enhanced Weakly Compressible Moving Particle Semi-implicit (EWC-MPS) method. It pays special attention to the evaluation and improvement of two particle regularization techniques, namely, pairwise particle collisi...

In this work, we develop an enhanced particle shifting strategy in the framework of weakly compressible δ+-SPH method. This technique can be considered as an extension of the so-called improved particle shifting technology (IPST) proposed by Wang et al. (2019). We introduce a new parameter named “ϕ” to the particle shifting formulation, on the one...

The present work introduces a modified Incompressible Smoothed Particle Hydrodynamics (ISPH) model for simulation of free-surface flows and convection heat transfer. First, two new gradient and Laplacian models are proposed based on the Taylor series expansion and then used for discretization of the diffusion terms, Pressure Poisson's equation (PPE...

A novel Kernel Derivative-Free (KDF) Weakly-Compressible Smoothed Particle Hydrodynamics (WCSPH) model is developed for simulation of free-surface flows and convection heat transfer. A high-order Laplacian operator is developed and then applied for the approximation of the diffusion terms (e.g., viscous term, thermal diffusion, and newly additional...

Similar to other particle methods, the Weakly-Compressible MPS (WC-MPS) is known to suffer from numerical instabilities and unphysical pressure fluctuations. Here we develop, adapt and evaluate a series of enhancement techniques to improve the stability and accuracy of this numerical approach. This includes a new conservative pressure gradient form...

Tailings dams, used for containing the residue of mining processes, are very important elements of the Alberta oil-sands industry in Canada. Potential breach of any of these dams can have catastrophic impact on the environment, economy and human health and safety. Therefore, understanding the after-breach processes is a crucial step in hazard analy...

The slide of granular material in nature and engineering can happen under air (subaerial), under a liquidlike water (submerged), or a transition between these two regimes, where a subaerial slide enters a liquid and becomes submerged. Here, we experimentally investigate these three slide regimes (i.e., subaerial, submerged, and transitional) in two...

Recent tailings dam disasters in Brazil have increased the public concern on the risk and potential environmental damages of the existing tailings dams. The prediction of tailings slurry flow due to the dam failures is of great importance for incident prevention and mitigation. This study aims to develop a numerical model in order to predict potent...

Fluvial/coastal sediment transport, debris flows, and landslides are a few examples of sediment dynamic problems. Modelling and predicting the mechanical behaviours of these so-called multiphase granular flows are crucial for optimum engineering designs and hazard management. The mesh-free particle approaches, with an inherent ability to deal with...

This paper presents a three-dimensional fully Lagrangian numerical model, based on the hybrid discrete element method (DEM) and moving particle semi-implicit (MPS) mesh-free techniques, for modelling the dynamics of river ice floes. The model considers the ice-water dynamics as a multiphase discrete-continuum system. The DEM uses a Hertzian contact...

Sediment scouring is a common example of highly dynamic sediment transport. Considering its complexities, the accurate prediction of such a highly dynamic multiphase granular flow system is a challenge for the traditional numerical techniques that rely on a mesh system. The mesh-free particle methods are a newer generation of numerical techniques w...

Within the Oil-Sands industry in Alberta, Canada, tailings ponds are used as water recycling and tailings storage facilities (TSF) for mining activities. However, there could be possible circumstances under which a sudden breach of an embankment confining one of the TSFs may occur. Such a tailings pond breach would result in a sudden release of a h...

A novel multiphase mesh-free particle numerical model is developed and applied for modeling of sub-aerial (dry) and submerged (underwater) landslides. The model is based on the weakly-compressible moving particle semi-implicit method (WC–MPS), and treats the multiphase system of water and granular materials as a multi-density multi-viscosity contin...

The potential effects of climate change on the hydrodynamic and sediment transport regime of the lower Athabasca River (LAR) in Alberta, Canada, is investigated. Future climate projections for the region suggest a potential increase in mean air temperature and precipitation by about 2.8–7.1 °C and 8–25%, respectively, by the end of this century. Im...

We develop and fully characterize a meshfree Lagrangian (particle) model for continuum-based numerical modeling of dry and submerged granular flows. The multiphase system of the granular material and the ambient fluid is treated as a multi-density multi-viscosity system in which the viscous behaviour of the granular phase is predicted using a regul...

We develop and fully characterize a meshfree Lagrangian (particle) model for continuum-based numerical modeling of dry and submerged granular flows. The multiphase system of the granular material and the ambient fluid is treated as a multi-density multi-viscosity system in which the viscous behaviour of the granular phase is predicted using a regul...

Purpose The transport of fine sediments and associated chemical constituents originating from potential anthropogenic and natural sources is becoming an issue of increasing importance in the Lower Athabasca River (LAR) ecosystem in northern Alberta, Canada. This study aims to (1) establish an integrated numerical modelling framework to investigate...

Flows and transport of sediment and associated chemical constituents within the lower reaches of the Athabasca River between Fort McMurray and Embarrass Airport are investigated using a two-dimensional (2D) numerical model called Environmental Fluid Dynamics Code (EFDC). The river reach is characterized by complex geometry, including vegetated isla...

There is a great deal of interest to determine the state and variations of water quality parameters in the lower Athabasca River (LAR) ecosystem, northern Alberta, Canada, clue to industrial developments in the region. As a cold region river, the annual cycle of ice cover formation and breakup play a key role in water quality transformation and tra...

There is a great deal of interest to determine the state and variations of water quality parameters in the lower Athabasca River (LAR) ecosystem, northern Alberta, Canada, due to industrial developments in the region. As a cold region river, the annual cycle of ice cover formation and breakup play a key role in water quality transformation and tran...

A meshless particle numerical model based on the Smoothed Particle Hydrodynamics (SPH) is developed and evaluated for two-dimensional simulation of free-surface flows passing through an orifice and over a sharp crested weir. A practical technique is introduced making the model capable of handling the inlet and outlet boundaries. This technique is a...

Confluences are common features of natural and man-made channel systems where convergence of joining flows creates a complex flow and sediment transport pattern producing strong flow circulations and rapid changing in bed morphology. By the means of laboratory experiments on several mobile-bed channel confluences, this study (1) investigates and fo...

A two-phase mesh-free Lagrangian model, based on the Smoothed Particle Hydrodynamics (SPH) method, is developed and evaluated for the continuum-based study of sediment-water system (a dense submerged granular flow system). The case studies are (a) sediment scouring downstream of a wall-jet, and (b) reservoir sediment flushing, both of great interes...

A meshless Lagrangian (particle) method based on the weakly compressible moving particle semiimplicit formulation (WC-MPS) is developed and analysed for simulation of flow over spillways. To improve the accuracy of the model for pressure and velocity calculation, some modifications are proposed and evaluated for the inflow and wall boundary conditi...

Confluences are common features of natural and man-made channel systems where convergence of joining flows creates a complex flow and sediment transport pattern producing strong flow circulations and rapid changing in bed morphology. By the means of laboratory experiments on several mobile-bed channel confluences, this study (1) investigates and fo...

Confluences are common features of natural and man-made channel systems where convergence of joining flows creates a complex flow and sediment transport pattern producing strong flow circulations and rapid changing in bed morphology. By the means of laboratory experiments on several mobile-bed channel confluences, this study (1) investigates and fo...

In this study, the deposition of solid particles in natural convection flow in a square cavity (heat exchanger) filled with air is investigated numerically using an Eulerian-Lagrangian hybrid method. Walls of the enclosure are insulated and several pairs of heater and cooler (HACs) with isothermal walls of Th and Tc (Th> Tc) are placed inside the c...

Mesh-free particle (Lagrangian) methods have been used in a wide variety of applications in fluids studies in recent decades. A big advantage of these methods is the ability to model the deformations and spray generation in boundaries and interfaces, which are common problems with jets and jumps and may be difficult using Eulerian methods. Weakly c...

Dealing with large deformation and fragmentation of geometries and interfaces (e.g., free surfaces), the regular mesh-based Eulerian methods, such as finite-element and finite-difference methods, have difficulties in fluid-flow modeling. Recently, studies have focused on a new generation of numerical methods called mesh-free particle (Lagrangian) m...

A particular flow structure and the behaviour of free surface complicate flow modelling over sills, especially if the free surface is highly deformed and made up of spray. Mesh-free particle methods have recently been developed to increase the flexibility and accuracy of numerical methods to deal with these boundaries and interfaces. This research...

River channel confluence is one of the features of each river system. The point, at which two channels meet, is marked by highly complex three-dimensional pattern of flow, sediment transport and bed changes. Complex flow characteristics within a confluence is dominated by distinctive secondary currents, flow deflection, flow separation, flow contra...