Mhamed Souli - Academia.edu (original) (raw)
Papers by Mhamed Souli
Buildings
The paper presents the sound absorption coefficient of acoustic absorbers fabricated from natural... more The paper presents the sound absorption coefficient of acoustic absorbers fabricated from natural durian husk fibers, which are currently still considered as agricultural wastes, especially in Malaysia. Samples were fabricated with different fiber densities and thicknesses and the sound absorption performance was measured using the impedance tube method. The results reveal that the durian husk fibers can have absorption coefficient of more than 0.5 above 1 kHz for a minimum thick sample of 20 mm and with minimum density of 160 kg/m3. The optimised macroscopic parameters for various densities were calculated using the inverse method employing the well-known Johnson-Champoux-Allard (JCA) model for porous material.
Polymers, 2021
Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation indu... more Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation industry, both for military and civilian applications. The materials used so far in the manufacture of UAVs are wood, plastic, aluminum and carbon fiber. In this regard, a new family of high-density polyethylene (HDPE) nanocomposites reinforced with polymethylsilsesquioxane nanoparticles (PMSQ), with mechanical performances significantly superior to those of pure HPDE, has been prepared by a fusion-combination process. Their viscoelastic properties were determined by oscillatory shear tests and their viscoelastic behavior characterized by the Lodge integral model. Then, the Lagrangian formulation and the membrane theory assumption were used in the explicit implementation of the dynamic finite element formulation. For the forming phase, we considered the thermodynamic approach to express the external work in terms of closed volume. In terms of von Mises stress distribution and thickness in th...
ASME. PVP (American Society of Mechanical Engineers. Pressure Vessels and Piping Div.), 1997
Journal of Heat Transfer, 2022
This paper concerns the joint application of the B-spline method and the Kirchhoff transformation... more This paper concerns the joint application of the B-spline method and the Kirchhoff transformation to solve the nonlinear problem of thermal conduction with radiation type boundary conditions. The proposed method requires few iterations, sometimes none, for solids subjected to prescribed temperature boundary conditions. This method can be deployed by other numerical approaches (boundary element method, finite element method, finite element method, etc.) for the resolution of the heat conduction equation (linear or nonlinear), in terms of the Kirchhoff transformation θ. For numerical implementation, the steady-state finite element method is considered. The numerical validation was performed for a hollow aluminum cylinder whose outer surface is subjected to radiation. Three types of thermal conductivities are considered: (i) constant, (ii) linear, and (iii) nonlinear. As an application, we studied the thermal response of an aluminum reactor, in the form of an annular disk with cooling ...
This book comprises of the proceedings of the ASME/JSME Pressure Vessels and Piping Conference, J... more This book comprises of the proceedings of the ASME/JSME Pressure Vessels and Piping Conference, July 25-29, 2004, San Diego, California. Proceedings of 8th international symposium, volume 2, consisting of 25 papers. The topics covered include: dynamics of explosive detonation, materials and structures; and advances in materials and structures. It is part of a two volume set written by W. Cheng and S. Itoh.
Sloshing has been one of the major concerns for engineers in the design of liquid cylindrical tan... more Sloshing has been one of the major concerns for engineers in the design of liquid cylindrical tanks. During many past major earthquakes; failure of cylindrical liquid storage tanks due to sloshing has been led to fire, explosions, disrupt production, serious environmental hazards and large amounts of financial loss. On the other hand, destructive effects of sloshing phenomenon can be suppressed in a passive manner by introducing additional sub-structures called baffles into tanks. The main purpose of constructing these sub-structures is to alter period of sloshing action beneficially and to increase hydrodynamic damping ratio. There are numerous experimental and numerical studies in the literature, where the effect of geometric parameters of baffles, such as configurations, widths, thicknesses, and locations, on hydrodynamic damping ratio and sloshing frequency has been investigated. However, the influence of the flexibility of baffles on the hydrodynamic damping ratio in large tank...
Research in Plant Biology, 2011
The incidence of the disease seems very important on young trees and tends to bemoderate with the... more The incidence of the disease seems very important on young trees and tends to bemoderate with the aging of the tree. In fact, olive trees have a shallow root system and arestill vulnerable to pathogens especially the irrigated varieties. Chemical and biological control against Fusarium solani , Fusarium oxysporum , Rhizoctonia solani and Verticillium dahliae have revealed that the application in vitro of Prodazim and of Methyl-thiophanatehave showed a very good efficacy up to 100%. Ridomil and Tachigaren have indicated aregular efficiency, while the two bio-fungicides Fungstop and the compost juice havedemonstrated a low efficiency. The two bio-control agents Trichoderma harzianum and Gliocladium virens have showed a relatively high effectiveness in vitro . In vivo , obtainedresults have revealed that the nature of the product, the doses applied and the condition ofthe olive trees are highly correlated factors. The treatment doesn’t appear to have apositive effect on the beginning...
Cmes-computer Modeling in Engineering & Sciences, 2011
A mechanical computer aided design and engineering system can be used to reduce the design-to-man... more A mechanical computer aided design and engineering system can be used to reduce the design-to-manufacture cycle time in metal forming process. Such a system could be built upon a solid modeling geometry engine and an efficient finite element (FE) solver. The maintenance of a high-quality mesh throughout the analysis is an essential feature of an efficient finite element simulation of large strain metal forming problems. In this paper, a mesh adaptation technique employing the Arbitrary Lagrangian-Eulerian formulation (ALE) is applied to some industrial metal forming problems. An ACIS boundary representation of the solid model is employed. This type of representation provides the necessary data for adaptive meshing techniques. To take care of large deformations, the Lagrangian types of mesh adaptation zones are used. The new mesh, which is updated at a given frequency, is found by iterating on the adaptation zones. During this process, mesh nodes are moved to new positions in order t...
Cmes-computer Modeling in Engineering & Sciences, 2013
To simulate accurately a pressure wave propagation problem, a fine mesh is required in order to c... more To simulate accurately a pressure wave propagation problem, a fine mesh is required in order to capture peak pressures accurately. This may require a very large size problem with several millions of elements. To reduce CPU time and prevent high mesh distortion, a two-dimensional problem for blast ignition and pressure propagation is performed first on a fixed Eulerian mesh. When the pressure wave gets closer to the structure, a three dimensional ALE simulation follows, where the fluid mesh and structure mesh at the fluid structure interface are coincident. The three dimensional problem is performed after mapping history variables from the two-dimensional to the three dimensional mesh. In this paper an ALE multi-material formulation is used for both explosive and air materials, and a classical Lagrangian formulation for the structure. The method has been implemented successfully in LSDYNA code and validated with different applications. To validate the method, this technique is used f...
Multiphysics Simulations in Automotive and Aerospace Applications, 2021
Abstract Manufacturing industries including the automotive industries continue to refine their pr... more Abstract Manufacturing industries including the automotive industries continue to refine their products toward adopting green materials as an effort to reduce the environmental impact and at the same time, company branding. One of the applications is natural acoustic materials for noise control. Characterization of the materials is important to obtain the acoustical properties required as the parametric input in simulation at the design state, for example, in statistical energy analysis to determine the performance of sound absorption and sound insulation in a car cabin, which directly affects the flow of acoustic and vibration energy. In this chapter, the methodology of measuring and modeling the sound absorption coefficient of natural material is presented. Here the natural kenaf fibers are used as the test material, and the presented methodology is applicable for other natural fibers. The modeling employs the inverse method using Johsnon–Champoux–Allard model, where five acoustical parameters are obtained from an optimization process from the experimental data of sound absorption coefficient. It is demonstrated that the method can be used as a fast and practical solution for acoustic characterization of new materials.
Multiphysics Simulations in Automotive and Aerospace Applications, 2021
Abstract Simulation of airbag and membrane deployment under pressurized gas problems becomes more... more Abstract Simulation of airbag and membrane deployment under pressurized gas problems becomes more and more the focus of computational engineering, where finite element methods (FEMs) for structural mechanics and finite volume for computational fluid dynamics are dominant. New formulations have been developed for fluid structure interaction (FSI) applications using mesh free methods as smooth particle hydrodynamic (SPH) method. Up to these days very little has been done to compare different methods and assess which one would be more suitable. For small deformation, FEM Lagrangian formulation can solve structure interface and material boundary accurately, the main limitation of the formulation is high mesh distortion for large deformation and moving structure. One of the commonly used approaches to solve these problems is the arbitrary Lagrangian Eulerian (ALE) formulation which has been used with success in the simulation of FSI with large structure motion such as sloshing fuel tank in automotive industry and bird impact in aeronautic industry. For some applications, including bird impact and high velocity impact problems, engineers have switched from ALE to SPH method to reduce central processing unit (CPU) time and save memory allocation. Both ALE and SPH methods are described and compared here using similar mesh size, each ALE element is replaced by an SPH particle at the element center. From different simulation, it has been observed that for the SPH method to provide similar results as ALE or Lagrangian formulations, the SPH meshing needs to be finer than the ALE mesh. A contact algorithm is performed at the FSI for both SPH and ALE formulations. A simulation of airbag membrane deployment generated by high pressurized gas is performed.
The International Journal of Multiphysics, 2021
When a train is running on a railway track, its wheel-rail's dynamic and static forces exerts a v... more When a train is running on a railway track, its wheel-rail's dynamic and static forces exerts a vertical, longitudinal, and lateral load on the ground. A railroad track has two main parts which are superstructure which includes fastening systems, tie, and rail and substructure which includes fill material, bottom ballast, top ballast, subgrade, and sub ballast. Rail tracks that are ballasted get deformed with time in both lateral and vertical directions that lead to, in case of persistent traffic loading, deviations from the intended geometry. This study will develop a simulation of a complicated three-dimensional finite element model so that the ballast can detect the railway's life cycle. The simulation is created so that the railway track's cycle can be determined.
The International Journal of Multiphysics, 2018
The International Journal of Multiphysics, 2019
Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 2, Dynamics of Explosive Detonation, Materials and Structures, Structural Mechanics and Design, 2004
Computational and Mathematical Methods in Medicine, 2017
The aim of this study is to present a reliable computational scheme to serve in pulse wave veloci... more The aim of this study is to present a reliable computational scheme to serve in pulse wave velocity (PWV) assessment in large arteries. Clinicians considered it as an indication of human blood vessels’ stiffness. The simulation of PWV was conducted using a 3D elastic tube representing an artery. The constitutive material model specific for vascular applications was applied to the tube material. The fluid was defined with an equation of state representing the blood material. The onset of a velocity pulse was applied at the tube inlet to produce wave propagation. The Coupled Eulerian-Lagrangian (CEL) modeling technique with fluid structure interaction (FSI) was implemented. The scaling of sound speed and its effect on results and computing time is discussed and concluded that a value of 60 m/s was suitable for simulating vascular biomechanical problems. Two methods were used: foot-to-foot measurement of velocity waveforms and slope of the regression line of the wall radial deflection ...
Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology, 2016
When ice floes collide against marine structures, pronounced hydrodynamic loads are induced by th... more When ice floes collide against marine structures, pronounced hydrodynamic loads are induced by the water-ice-structure interaction. With today’s highly competitive structural design market, it is nearly impossible to ignore the advances that have been made in the computer analysis of fluid-structure interaction (FSI) problems. FSI methods can provide accurate representation of hydrodynamic effects. A number of commercial programs have been developed, and their applications in structural design increases rapidly. For instance, Arbitrary Lagrangian-Eulerian (ALE) formulations have been used to solve underwater explosions problems in ocean engineering, and soil-structure interaction problems in civil engineering. Application to fluid-ice-structure interaction problems is more recent and growing. This paper represents a contribution in assessing the capabilities of the ALE formulation for fluid-ice-structure collision problems. The ALE and coupling algorithms have been successfully vali...
Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 1, Fluid Dynamics and Fluid Structure Interactions, 2004
The Arbitrary Lagrangian-Eulerian (ALE) method is a method that contains both pure Lagrangian and... more The Arbitrary Lagrangian-Eulerian (ALE) method is a method that contains both pure Lagrangian and pure Eulerian formulations. It is assumed to be capable to control mesh geometry independently from material geometry. However for transient problems involving pressure wave, this method will not allow to maintain a fine mesh in the vicinity of the shock wave for accurate solution. A new mesh relaxation method for explicit multi-material arbitrary Lagrangian Eulerian finite element simulations has been developed to keep an as “Lagrange like” fluid mesh as possible as in the vicinity of shock fronts, while at the same time keeping the mesh distortions on an acceptable level. However, the relaxation parameter must be defined for general applications of high pressures, it is the objective of this work. In this paper we present numerical results of three shock waves problems. For every application, numerical results will be compared with the experimental results in order to improve to under...
Engineering Failure Analysis, 2015
There have been increasing reports of annoyance, fatigue, and even neck and back pain during prol... more There have been increasing reports of annoyance, fatigue, and even neck and back pain during prolonged operation of troop propeller aircraft, where persistent multi-axis vibration occurs at higher frequencies. A claim from failure of the 2024-T3 aluminum tube used as a seat support tube (SST) for troop seat-wall style-construction. A failure occurs after about 85 flight hours. A numerical static analysis model for the tube with its holders shows that it is safe, even with impact loading. In the present work, a random vibration analysis is conducted to calculate the lifetime of the SST. First, a static analysis is performed using a pressure load on part of the tube that represents the seating location, followed by random vibration analysis. A contact algorithm is added in order to transfer the support's movement to the tube. Dirlik method is used for the analysis of lifetime as it is proven to provide accurate results for large number of applications, both in automotive and aerospace industry. The predicted service life is in a good agreement with the real actual life.
Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 1, Fluid Dynamics and Fluid Structure Interactions, 2004
Fluid-structure interactions play an important role in many different types of real-world situati... more Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions and it can, through an Eulerian-Lagrangian coupling algorithm, be combined with a Lagrangian description of motion for parts of the model. The Eulerian formulation is not free from numerical problems. There are dissipation and dispersion problems associated with the flux of mass between elements. In addition, many elements might be needed for the Eulerian mesh to enclose the whole sp...
Buildings
The paper presents the sound absorption coefficient of acoustic absorbers fabricated from natural... more The paper presents the sound absorption coefficient of acoustic absorbers fabricated from natural durian husk fibers, which are currently still considered as agricultural wastes, especially in Malaysia. Samples were fabricated with different fiber densities and thicknesses and the sound absorption performance was measured using the impedance tube method. The results reveal that the durian husk fibers can have absorption coefficient of more than 0.5 above 1 kHz for a minimum thick sample of 20 mm and with minimum density of 160 kg/m3. The optimised macroscopic parameters for various densities were calculated using the inverse method employing the well-known Johnson-Champoux-Allard (JCA) model for porous material.
Polymers, 2021
Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation indu... more Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation industry, both for military and civilian applications. The materials used so far in the manufacture of UAVs are wood, plastic, aluminum and carbon fiber. In this regard, a new family of high-density polyethylene (HDPE) nanocomposites reinforced with polymethylsilsesquioxane nanoparticles (PMSQ), with mechanical performances significantly superior to those of pure HPDE, has been prepared by a fusion-combination process. Their viscoelastic properties were determined by oscillatory shear tests and their viscoelastic behavior characterized by the Lodge integral model. Then, the Lagrangian formulation and the membrane theory assumption were used in the explicit implementation of the dynamic finite element formulation. For the forming phase, we considered the thermodynamic approach to express the external work in terms of closed volume. In terms of von Mises stress distribution and thickness in th...
ASME. PVP (American Society of Mechanical Engineers. Pressure Vessels and Piping Div.), 1997
Journal of Heat Transfer, 2022
This paper concerns the joint application of the B-spline method and the Kirchhoff transformation... more This paper concerns the joint application of the B-spline method and the Kirchhoff transformation to solve the nonlinear problem of thermal conduction with radiation type boundary conditions. The proposed method requires few iterations, sometimes none, for solids subjected to prescribed temperature boundary conditions. This method can be deployed by other numerical approaches (boundary element method, finite element method, finite element method, etc.) for the resolution of the heat conduction equation (linear or nonlinear), in terms of the Kirchhoff transformation θ. For numerical implementation, the steady-state finite element method is considered. The numerical validation was performed for a hollow aluminum cylinder whose outer surface is subjected to radiation. Three types of thermal conductivities are considered: (i) constant, (ii) linear, and (iii) nonlinear. As an application, we studied the thermal response of an aluminum reactor, in the form of an annular disk with cooling ...
This book comprises of the proceedings of the ASME/JSME Pressure Vessels and Piping Conference, J... more This book comprises of the proceedings of the ASME/JSME Pressure Vessels and Piping Conference, July 25-29, 2004, San Diego, California. Proceedings of 8th international symposium, volume 2, consisting of 25 papers. The topics covered include: dynamics of explosive detonation, materials and structures; and advances in materials and structures. It is part of a two volume set written by W. Cheng and S. Itoh.
Sloshing has been one of the major concerns for engineers in the design of liquid cylindrical tan... more Sloshing has been one of the major concerns for engineers in the design of liquid cylindrical tanks. During many past major earthquakes; failure of cylindrical liquid storage tanks due to sloshing has been led to fire, explosions, disrupt production, serious environmental hazards and large amounts of financial loss. On the other hand, destructive effects of sloshing phenomenon can be suppressed in a passive manner by introducing additional sub-structures called baffles into tanks. The main purpose of constructing these sub-structures is to alter period of sloshing action beneficially and to increase hydrodynamic damping ratio. There are numerous experimental and numerical studies in the literature, where the effect of geometric parameters of baffles, such as configurations, widths, thicknesses, and locations, on hydrodynamic damping ratio and sloshing frequency has been investigated. However, the influence of the flexibility of baffles on the hydrodynamic damping ratio in large tank...
Research in Plant Biology, 2011
The incidence of the disease seems very important on young trees and tends to bemoderate with the... more The incidence of the disease seems very important on young trees and tends to bemoderate with the aging of the tree. In fact, olive trees have a shallow root system and arestill vulnerable to pathogens especially the irrigated varieties. Chemical and biological control against Fusarium solani , Fusarium oxysporum , Rhizoctonia solani and Verticillium dahliae have revealed that the application in vitro of Prodazim and of Methyl-thiophanatehave showed a very good efficacy up to 100%. Ridomil and Tachigaren have indicated aregular efficiency, while the two bio-fungicides Fungstop and the compost juice havedemonstrated a low efficiency. The two bio-control agents Trichoderma harzianum and Gliocladium virens have showed a relatively high effectiveness in vitro . In vivo , obtainedresults have revealed that the nature of the product, the doses applied and the condition ofthe olive trees are highly correlated factors. The treatment doesn’t appear to have apositive effect on the beginning...
Cmes-computer Modeling in Engineering & Sciences, 2011
A mechanical computer aided design and engineering system can be used to reduce the design-to-man... more A mechanical computer aided design and engineering system can be used to reduce the design-to-manufacture cycle time in metal forming process. Such a system could be built upon a solid modeling geometry engine and an efficient finite element (FE) solver. The maintenance of a high-quality mesh throughout the analysis is an essential feature of an efficient finite element simulation of large strain metal forming problems. In this paper, a mesh adaptation technique employing the Arbitrary Lagrangian-Eulerian formulation (ALE) is applied to some industrial metal forming problems. An ACIS boundary representation of the solid model is employed. This type of representation provides the necessary data for adaptive meshing techniques. To take care of large deformations, the Lagrangian types of mesh adaptation zones are used. The new mesh, which is updated at a given frequency, is found by iterating on the adaptation zones. During this process, mesh nodes are moved to new positions in order t...
Cmes-computer Modeling in Engineering & Sciences, 2013
To simulate accurately a pressure wave propagation problem, a fine mesh is required in order to c... more To simulate accurately a pressure wave propagation problem, a fine mesh is required in order to capture peak pressures accurately. This may require a very large size problem with several millions of elements. To reduce CPU time and prevent high mesh distortion, a two-dimensional problem for blast ignition and pressure propagation is performed first on a fixed Eulerian mesh. When the pressure wave gets closer to the structure, a three dimensional ALE simulation follows, where the fluid mesh and structure mesh at the fluid structure interface are coincident. The three dimensional problem is performed after mapping history variables from the two-dimensional to the three dimensional mesh. In this paper an ALE multi-material formulation is used for both explosive and air materials, and a classical Lagrangian formulation for the structure. The method has been implemented successfully in LSDYNA code and validated with different applications. To validate the method, this technique is used f...
Multiphysics Simulations in Automotive and Aerospace Applications, 2021
Abstract Manufacturing industries including the automotive industries continue to refine their pr... more Abstract Manufacturing industries including the automotive industries continue to refine their products toward adopting green materials as an effort to reduce the environmental impact and at the same time, company branding. One of the applications is natural acoustic materials for noise control. Characterization of the materials is important to obtain the acoustical properties required as the parametric input in simulation at the design state, for example, in statistical energy analysis to determine the performance of sound absorption and sound insulation in a car cabin, which directly affects the flow of acoustic and vibration energy. In this chapter, the methodology of measuring and modeling the sound absorption coefficient of natural material is presented. Here the natural kenaf fibers are used as the test material, and the presented methodology is applicable for other natural fibers. The modeling employs the inverse method using Johsnon–Champoux–Allard model, where five acoustical parameters are obtained from an optimization process from the experimental data of sound absorption coefficient. It is demonstrated that the method can be used as a fast and practical solution for acoustic characterization of new materials.
Multiphysics Simulations in Automotive and Aerospace Applications, 2021
Abstract Simulation of airbag and membrane deployment under pressurized gas problems becomes more... more Abstract Simulation of airbag and membrane deployment under pressurized gas problems becomes more and more the focus of computational engineering, where finite element methods (FEMs) for structural mechanics and finite volume for computational fluid dynamics are dominant. New formulations have been developed for fluid structure interaction (FSI) applications using mesh free methods as smooth particle hydrodynamic (SPH) method. Up to these days very little has been done to compare different methods and assess which one would be more suitable. For small deformation, FEM Lagrangian formulation can solve structure interface and material boundary accurately, the main limitation of the formulation is high mesh distortion for large deformation and moving structure. One of the commonly used approaches to solve these problems is the arbitrary Lagrangian Eulerian (ALE) formulation which has been used with success in the simulation of FSI with large structure motion such as sloshing fuel tank in automotive industry and bird impact in aeronautic industry. For some applications, including bird impact and high velocity impact problems, engineers have switched from ALE to SPH method to reduce central processing unit (CPU) time and save memory allocation. Both ALE and SPH methods are described and compared here using similar mesh size, each ALE element is replaced by an SPH particle at the element center. From different simulation, it has been observed that for the SPH method to provide similar results as ALE or Lagrangian formulations, the SPH meshing needs to be finer than the ALE mesh. A contact algorithm is performed at the FSI for both SPH and ALE formulations. A simulation of airbag membrane deployment generated by high pressurized gas is performed.
The International Journal of Multiphysics, 2021
When a train is running on a railway track, its wheel-rail's dynamic and static forces exerts a v... more When a train is running on a railway track, its wheel-rail's dynamic and static forces exerts a vertical, longitudinal, and lateral load on the ground. A railroad track has two main parts which are superstructure which includes fastening systems, tie, and rail and substructure which includes fill material, bottom ballast, top ballast, subgrade, and sub ballast. Rail tracks that are ballasted get deformed with time in both lateral and vertical directions that lead to, in case of persistent traffic loading, deviations from the intended geometry. This study will develop a simulation of a complicated three-dimensional finite element model so that the ballast can detect the railway's life cycle. The simulation is created so that the railway track's cycle can be determined.
The International Journal of Multiphysics, 2018
The International Journal of Multiphysics, 2019
Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 2, Dynamics of Explosive Detonation, Materials and Structures, Structural Mechanics and Design, 2004
Computational and Mathematical Methods in Medicine, 2017
The aim of this study is to present a reliable computational scheme to serve in pulse wave veloci... more The aim of this study is to present a reliable computational scheme to serve in pulse wave velocity (PWV) assessment in large arteries. Clinicians considered it as an indication of human blood vessels’ stiffness. The simulation of PWV was conducted using a 3D elastic tube representing an artery. The constitutive material model specific for vascular applications was applied to the tube material. The fluid was defined with an equation of state representing the blood material. The onset of a velocity pulse was applied at the tube inlet to produce wave propagation. The Coupled Eulerian-Lagrangian (CEL) modeling technique with fluid structure interaction (FSI) was implemented. The scaling of sound speed and its effect on results and computing time is discussed and concluded that a value of 60 m/s was suitable for simulating vascular biomechanical problems. Two methods were used: foot-to-foot measurement of velocity waveforms and slope of the regression line of the wall radial deflection ...
Volume 8: Polar and Arctic Sciences and Technology; Petroleum Technology, 2016
When ice floes collide against marine structures, pronounced hydrodynamic loads are induced by th... more When ice floes collide against marine structures, pronounced hydrodynamic loads are induced by the water-ice-structure interaction. With today’s highly competitive structural design market, it is nearly impossible to ignore the advances that have been made in the computer analysis of fluid-structure interaction (FSI) problems. FSI methods can provide accurate representation of hydrodynamic effects. A number of commercial programs have been developed, and their applications in structural design increases rapidly. For instance, Arbitrary Lagrangian-Eulerian (ALE) formulations have been used to solve underwater explosions problems in ocean engineering, and soil-structure interaction problems in civil engineering. Application to fluid-ice-structure interaction problems is more recent and growing. This paper represents a contribution in assessing the capabilities of the ALE formulation for fluid-ice-structure collision problems. The ALE and coupling algorithms have been successfully vali...
Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 1, Fluid Dynamics and Fluid Structure Interactions, 2004
The Arbitrary Lagrangian-Eulerian (ALE) method is a method that contains both pure Lagrangian and... more The Arbitrary Lagrangian-Eulerian (ALE) method is a method that contains both pure Lagrangian and pure Eulerian formulations. It is assumed to be capable to control mesh geometry independently from material geometry. However for transient problems involving pressure wave, this method will not allow to maintain a fine mesh in the vicinity of the shock wave for accurate solution. A new mesh relaxation method for explicit multi-material arbitrary Lagrangian Eulerian finite element simulations has been developed to keep an as “Lagrange like” fluid mesh as possible as in the vicinity of shock fronts, while at the same time keeping the mesh distortions on an acceptable level. However, the relaxation parameter must be defined for general applications of high pressures, it is the objective of this work. In this paper we present numerical results of three shock waves problems. For every application, numerical results will be compared with the experimental results in order to improve to under...
Engineering Failure Analysis, 2015
There have been increasing reports of annoyance, fatigue, and even neck and back pain during prol... more There have been increasing reports of annoyance, fatigue, and even neck and back pain during prolonged operation of troop propeller aircraft, where persistent multi-axis vibration occurs at higher frequencies. A claim from failure of the 2024-T3 aluminum tube used as a seat support tube (SST) for troop seat-wall style-construction. A failure occurs after about 85 flight hours. A numerical static analysis model for the tube with its holders shows that it is safe, even with impact loading. In the present work, a random vibration analysis is conducted to calculate the lifetime of the SST. First, a static analysis is performed using a pressure load on part of the tube that represents the seating location, followed by random vibration analysis. A contact algorithm is added in order to transfer the support's movement to the tube. Dirlik method is used for the analysis of lifetime as it is proven to provide accurate results for large number of applications, both in automotive and aerospace industry. The predicted service life is in a good agreement with the real actual life.
Emerging Technology in Fluids, Structures, and Fluid Structure Interactions: Volume 1, Fluid Dynamics and Fluid Structure Interactions, 2004
Fluid-structure interactions play an important role in many different types of real-world situati... more Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions and it can, through an Eulerian-Lagrangian coupling algorithm, be combined with a Lagrangian description of motion for parts of the model. The Eulerian formulation is not free from numerical problems. There are dissipation and dispersion problems associated with the flux of mass between elements. In addition, many elements might be needed for the Eulerian mesh to enclose the whole sp...