Showing 9 results for hadidi
Amin hadidi, Mohammadreza Ansari,
Volume 12, Issue 1 (4-2012)
Abstract
In this study, a single bubble behavior in dielectric viscous fluid under the uniform magnetic field has been simulated numerically by using a level set method in two-phase bubbly flow. The two-phase bubbly flow considered to be laminar and homogenous. Deformation of the bubble was considered due to buoyancy and magnetic forces induced from the external applied magnetic field. A computer code was developed to solve the problem with flow field, interface of two-phases, and the magnetic field. The Finite Volume method was applied using SIMPLE algorithm to differentiate the governing equations. Using this algorithm enables us to calculate the pressure parameter which was eliminated by previous researchers due to complexity of the two-phase flow. The Finite Difference method was used to solve the magnetic field equation. The results outlined in the present study well agree with the existing experimental data and numerical results. The results show that the magnetic field affects and controls the shape, size, velocity and location of the bubble.
Seyed Farhad Hosseini, Behnam Moetakef-Imani, Saeid hadidi Moud,
Volume 14, Issue 13 (First Special Issue 2015)
Abstract
The need for complex surfaces in CAD motivates researchers for methods which can produce smooth and visually pleasing surfaces. In this research, a new method is presented for creating compatible cross-sectional curves for surface fitting to certain sections or lofting. In this method, the distribution of sections' data points along with basis knot vectors are improved in order to reach a desired smooth surface. In compatibility process, the section curves' degrees and their knot vectors must be set equal before implementing lofting process. Based on proposed algorithm, in this research, the constructed smooth and faired surfaces can be used in many engineering applications such as reverse engineering, biomedical engineering, quality control, etc. The main focus of the method is improvement of data points' distributions and their assigned parameters in a way that by a few iterations, data points' distribution are improved in order to reach a common knot vector for all cross-sectional curves. The method is implemented on some benchmarking examples and its efficiency are confirmed. In addition, the amount of final data points' deviation from the initial section curve is analyzed using the vigorous Hausdorff method. It is worth mentioning that the quality of obtained final surface is visually pleasing. In order to quantitatively confirm that the proposed method will result in smooth and fair surfaces, MVS is used. Finally the application of the method in modeling the root joint zone of a wind turbine blade is presented.
Mehran Kadkhodayan, Ali Galehdari, Saied hadidi Moud,
Volume 14, Issue 16 (Forth Special Issue 2015)
Abstract
Given the significance of energy absorption in various industries, light shock absorbers such as honeycomb structure under in-plane and out of plane loads are in the core of attention. In this research an analytical equation for plateau stress is represented, taking power hardening model into consideration. The equation of specific absorbed of graded honeycomb structure with the locking strain and strain energy equation is represented. The structure made from five aluminum grades is simulated in ABAQUS/CAE for elastic-perfectly plastic and power hardening model, according to the results; numerical value of absorbed energy is compared to that of analytical method. A drop weight test on a graded honeycomb structure was performed. Based on the numerical simulation results, the experimental and numerical results showed good agreement. Based on the conducted comparisons, the numerical and analytical results are more congruent for power hardening model rather than elastic-perfectly plastic one. In the first step of optimization, by applying SQP method and genetic algorithm, the ratio of structure mass to the absorbed energy is minimized. In the second step, regarding the optimum value of parameters obtained in the first step, the material property of each row is changed. According to the optimization results, while keeping the mass of structure as constant, the structure capacity of absorbing energy is increased by 18% in the first step and 264% in the second model, compared to the primary model.
Amin hadidi, Davood Jalali Vahid,
Volume 15, Issue 11 (1-2016)
Abstract
The encounter between bubble pairs can be happened in the bubble flows and may result in coalescence, which is one of the most important elementary physical processes occurring in liquid columns. Sufficient knowledge of the coalescence process of two bubbles can lead to a better description of the bubbly flow’s behavior. Effects of uniform magnetic fields on the interactions and coalescence of dielectric bubbles were not studied up to now; therefore in this research, interactions and coalescence of two bubbles in a viscous stagnant liquid has been simulated numerically. Considered bubbles are spherical and fluids are stagnant, initially. Both liquid and gas phases considered being incompressible and dielectric where applied magnetic field is uniform. In the numerical simulation of the problem, the Finite Volume method was applied using the SIMPLE algorithm to discretizing the governing equations while the finite difference method was used for discretizing of the magnetic field equation. For simulating the interface of two phases, the level set method has been incorporated. The results outlined in the present study well agree with the existing experimental and numerical results. Obtained results show that applied uniform magnetic field affects shape, dynamics and also interactions and coalescence of bubble pairs. Applied magnetic field enhances coalescence between in-line rising bubbles. Therefore, the external uniform magnetic field could be used for contactless control of the coalescence process between bubbles.
Mahmoud Shariati, Hamid Zabihi Ferezqi, Saeid hadidi Moud,
Volume 16, Issue 8 (10-2016)
Abstract
The Assessment of strain accumulation due to nonlinear events like creep, plasticity or ratcheting phenomenon has gained importance, since it causes an increase in creep and fatigue damage of materials. Some factors like the magnitude of loading, constitutive equations or the elastic regions around the nonlinear events have effect on the rate of strain accumulation. The elastic follow-up can explain the mechanism of strain accumulation. This phenomenon may occur when a mechanical structure with elastic manner is connected to non-linear events and they are subjected to a displacement load. In these cases, the high rigidity portion of elastic region of mechanical structure may enhance the force to the regions with low rigidity. So in the local non-linear portion, the strain is accumulated. This phenomenon is proposed as an important instruction in mechanical assessment codes. In this study, the effects of Elastic Follow-up phenomenon on strain accumulation due to elastic-plastic and local creep are investigated. So the Elastic Follow-up parameter is defined by the methods which are described in high temperature assessment procedures (R5). The results revealed that the strain accumulation depends on the elastic region in structures which is described by the Elastic Follow-up phenomenon.
Amin hadidi, Majid Eshagh Nimvari, Mohamadreza Ansari,
Volume 18, Issue 2 (4-2018)
Abstract
In this research, interaction and oblique coalescence of bubbles under buoyancy force was simulated, numerically. The governing equations are continuity and momentum equations which have been discretized using the finite volume method and the SIMPLE algorithm. For simulating the interface of two phases, the level set method has been incorporated. Level Set method suffers from poor mass conservation of dispersed phase especially in the case of severe deformation of interface. In order to control of mass conservation of the level set method, re-initialization equations and a geometric mass control loop are used which this loop is implemented in the level set method for the first time in this research. Using proposed geometric mass control loop, mass dissipation drawback of the level set method is handled in simulation of bubbles’ coalescence. The results outlined in the present study well agree with the existing experimental results. Also results of investigation of mass dissipation of the proposed scheme to simulation of oblique coalescence problem show that the maximum amount of this mass dissipation was less than 4%. Therefore, the level set method with proposed geometric mass control loop could be used properly for simulation of oblique interactions and coalescence of bubbles in multiphase flows.
Volume 19, Issue 2 (7-2019)
Abstract
In this paper, due to the role of the catenary action of the structural members in large deformations and transfer of additional loads due to the middle column removal is important to prevent the catastrophic event of progressive collapse, a simulation method is introduced using 3D numerical finite element method (FEM). This method is simple, reliable and very suitable for predicting the response of RC members to the failure level. For verification of numerical model, two series of specimens tested experimentally by previous researchers have been used. The first series include the beam-column subassemblages under a middle column removal senario for comparing and displaying the numerical modeling capabilities in the prediction of three levels of performance including flexural, compressive arc and catenary action and the second series include a set of concrete beams rienforced with hybrid combinations of steel and fiber Reinforced polymer (FRP) bars. Comparisons between the load-displacement curves obtained from experimental data and numerical results of both series of specimens reveal the high accuracy of the proposed simulation method. In the following of research, based on validated numerical models, the effect of FRP bars in combination with steel reinforcement on the performance of beam-column subassemblages under progressive collapse and the effect of mechanical properties and their arrangement in concrete beams section on the strength and ductility and catenary action are investigated.
A. hadidi, M.r. Ansari,
Volume 19, Issue 12 (December 2019)
Abstract
In this research, the behaviour of a single droplet of the dielectric field under the effect of the applied external uniform magnetic field has been investigated. Previously, it was thought that no force is applied to the dielectric fluids when exposed to the uniform magnetic field. A stagnant droplet in a quiescent fluid column was considered in order to determination of the net effect of the applied uniform magnetic field. Considering that the droplet behaviour has been investigated in the horizontal plane, the net effect of the gravity on the droplet and the surrounding fluid is also zero. Therefore, any change in the condition of the considered droplet will be due to the effect of the applied magnetic field. Numerical analysis has been used to perform this research. The governing equations of the problem are the continuity, momentum, level set equations for interface simulation, re-initialization and re-construction equations of the level set equations to control the mass dissipation of this method. The governing equations have been discretized and solved by developing code in the Fortran programming environment. The behaviour of the considered droplet in various regimes has been investigated under the different magnitudes of the applied magnetic field. The results of the research in various cases show that stagnant droplet deforms under the effect of the applied magnetic field and starts to vibrate which also induces the motion in the surrounding quiescent fluid.
Volume 19, Issue 131 (January 2022)
Abstract
Nowadays, the development of reduced calorie non-dairy products is of great importance. Therefore, in the current study, the effect of adding 1% w/w tragacanth gum and replacing sucrose with stevia sweetener at 45% w/w on properties such as pH, total soluble solids, firmness, viscosity, color, syneresis and sensory properties of almond milk-based non-dairy dessert was evaluated during a 21 day of cold storage. The results revealed that the pH and syneresis of the dessert containing tragacanth gum and stevia at the end of storage period were 2.76 and 58.61% lower than the control sample, respectively. However, the total soluble solids, firmness and viscosity increased significantly (p<0.05) with the addition of tragacanth gum and stevia during cold storage period. On the first day of storage, a 6.04% reduction for lightness (L*) and an increase of 441.18% and 38.38% for redness-greenness (a*) and yellowness-blueness (b*) was observed for the samples containing tragacanth gum and stevia, respectively. The results of sensory evaluation showed that almond milk-based non-dairy dessert containing tragacanth gum and stevia had higher sensory scores than the control sample during the cold storage period, although this difference was not significant for color, taste and flavor characteristics (p>0.05). Finally, it can be concluded that tragacanth gum can be used as a thickener in the formulation of almond milk-based non-dairy dessert. In addition, partial replacement of sucrose by stevia does not have an adverse effect on the properties of the final product, so it can be used to produce a reduced calorie non-dairy dessert.
