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A boundary element method for investigation of sloshing in complex 3D containers
, Article 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Waikiki, HI, 23 April 2007 through 26 April 2007 ; Volume 8 , 2007 , Pages 8288-8292 ; 02734508 (ISSN); 1563478927 (ISBN); 9781563478925 (ISBN) ; Haddadpour, H ; Ghasemi, M ; Sharif University of Technology
2007
Abstract
This paper presents a matrix form model for determination of sloshing frequencies and modes in 3D liquid tanks. The governing equations of the incompressible inviscid potential flow are used to derive the governing boundary integral equation and then the boundary element method along with the collocation method is applied to obtain a matrix form standard eigenvalue problem. The sloshing mass and stiffness matrices are computed using analytical formulas which are given for quadratic boundary elements. Two typical examples are used to validate the introduced model and very good results are achieved in comparison with the exact results in the literature
Reduced-order aerodynamic model for aeroelastic analysis of complex configurations in incompressible flow
, Article Journal of Aircraft ; Volume 44, Issue 3 , 2007 , Pages 1015-1019 ; 00218669 (ISSN) ; Behbahani Nejad, M ; Firouz Abadi, R. D ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2007
Abstract
A general reduced-order aeroelastic model for 3-D complex geometries in subsonic incompressible flow regimes in the continuous-time domain was developed. A boundary element method (BEM) based fluid eigenanalysis solver was integrated with a finite element method (FEM) based modal technique of structural modeling. A body assumed to be a closed surface with known solid boundaries submerged in a potential flow is considered. The wake is considered to be thin and no aerodynamic loads will be supported by it. domain. The modal formulation of the aerodynamic system must be modified with a static correction method to include at least the quasi-static contribution of the higher truncated modes. The...
Dynamics, Stability, and Aero-servo-elasticity of Airships with Flexible Body and Fins
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
In this research, the dynamics, aero-elasticity, and control of an airship with a flexible body hull and fins are investigated. The flexible airship is modeled as a combination of several beams with specific boundary conditions. So that the dynamics and vibration of its body hull and fins can be taken into account regarding the aerodynamic, gravity, aerostatic, and control input forces. The governing equations of motion of the system are derived by using the velocity of an arbitrary point on each component and integration over the component and substituting them into the Euler-Lagrange equations in a body frame. Afterward, the added mass acting on the hull is calculated. Then, a perturbation...
Pressure effects on electroosmotic flow of power-law fluids in rectangular microchannels
, Article Theoretical and Computational Fluid Dynamics ; Vol. 28, issue. 4 , 2014 , pp. 409-426 ; ISSN: 09354964 ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Abstract
In this paper, the fully developed electroosmotic flow of power-law fluids in rectangular microchannels in the presence of pressure gradient is analyzed. The electrical potential and momentum equations are numerically solved through a finite difference procedure for a non-uniform grid. A complete parametric study reveals that the pressure effects are more pronounced at higher values of the channel aspect ratio and smaller values of the flow behavior index. The Poiseuille number is found to be an increasing function of the channel aspect ratio for pressure assisted flow and a decreasing function of this parameter for pressure opposed flow. It is also observed that the Poiseuille number is...
Dynamic response of a flat plate subjected to compression force during vertical and oblique impacts with calm water
, Article Engineering Structures ; Volume 176 , 2018 , Pages 697-706 ; 01410296 (ISSN) ; Rahbar Ranji, A ; Haddadpour, H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
An existing hydroelastic model is extended for a flat plate subjected to a compression force with spiral spring boundary conditions during water entry. Both vertical and oblique impacts of the plate into calm water are investigated. A longitudinal strip of the plate is analyzed by fully coupling hydrodynamic pressure with elastic responses. Hydrodynamic pressure is determined by potential flow theory and plate deflections are expressed in terms of dry normal modes. The plate deflections are validated through comparison with available asymptotic models, semi-analytical and experimental results. The effect of compression force on the plate deflection is investigated at the midpoint considering...
Error propagation in non-iterative EIT block method
, Article ISSPIT 2007 - 2007 IEEE International Symposium on Signal Processing and Information Technology, Cairo, 15 December 2007 through 18 December 2007 ; 2007 , Pages 678-681 ; 9781424418350 (ISBN) ; Pashakhanlou, F ; Vosoughi Vahdat, B ; Sharif University of Technology
2007
Abstract
The Block method approach to solve EIT problem leads to an exact solution if the measurements are done without error. Non-iterative method is a feasible approach on solving 3D EIT forward problem. However, the effect of the measurement error has not been considered in this method yet. In this article, the 3D model of EIT with block method has been considered. The required equations to solve the forward problem are then generated. To solve the forward problem, non-iterative method has been employed. Effect of the measurement error on forward problem for a 3D model of EIT are generated. It has been shown that for a sample 3D model, measurement error can propagate exponentially. ©2007 IEEE
A hybrid model for simulation of fluid-structure interaction in water entry problems
, Article Physics of Fluids ; Volume 33, Issue 1 , 2021 ; 10706631 (ISSN) ; Rahbar Ranji, A ; Haddadpour, H ; Moghadas, H ; Sharif University of Technology
American Institute of Physics Inc
2021
Abstract
A hydroelastic hybrid model is developed to simulate the fluid-structure interaction in water entry problems using the partitioned approach. The interactions between a flat plate and the water are modeled by a hydroelastic model using explicit and implicit couplings. Both couplings are unstable due to numerical instability associated with the fluid added mass. To overcome the instability, an extended Wagner's model is combined with the hydroelastic model, and a hybrid model is developed. The extended Wagner's model is the extension of the classical Wagner's model that is used to estimate the fluid inertial, damping, and restoring forces of a flexible plate within the potential flow theory....
A modal approach to second-order analysis of sloshing using boundary element method
, Article Ocean Engineering ; Volume 38, Issue 1 , Volume 38, Issue 1 , 2011 , Pages 11-21 ; 00298018 (ISSN) ; Ghasemi, M ; Haddadpour, H ; Sharif University of Technology
Abstract
This paper aims at developing a modal approach for the non-linear analysis of sloshing in an arbitrary-shape tank under both horizontal and vertical excitations. For this purpose, the perturbation technique is employed and the potential flow is adopted as the liquid sloshing model. The first- and second-order kinematic and dynamic boundary conditions of the liquid-free surface are used along with a boundary element model which is formulated in terms of the velocity potential of the liquid-free surface. The boundary element model is used to determine the natural mode shapes of sloshing and their corresponding frequencies. Using the modal analysis technique, a non-linear model is presented for...
Hydro-aerodynamic mathematical model and multi-objective optimization of wing-in-ground effect craft in take-off
, Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 232, Issue 4 , 2018 , Pages 421-433 ; 14750902 (ISSN) ; Seif, M. S ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
Hydro-aerodynamic mathematical model and multi-objective optimization of a popular wing-in-ground effect craft are presented in this research using a hydro-aerodynamic practical method and the genetic algorithm. The primary components of the wing-in-ground effect craft configuration include a compound wing, catamaran hull form and a power-augmented ram platform. The hydro-aerodynamic practical method with low computational time and high accuracy is performed by coupling hydrodynamic and aerodynamic considerations using the potential flow theory in ground effect and the semi-empirical equations proposed for high-speed marine vehicles. The trade-off between hydrodynamic and aerodynamic...
Hydroelastic analysis of two degree of freedom hydrofoil using a reduced-order hydrodynamic model considering unsteady partial sheet cavity flows
, Article Journal of Fluids and Structures ; Volume 81 , 2018 , Pages 116-130 ; 08899746 (ISSN) ; Haddadpour, H ; Dehghani Firouz Abadi, R ; Sharif University of Technology
Academic Press
2018
Abstract
In the present study a new, fast, precise algorithm for studying hydroelastic stability of a typical section with two degrees of freedom (2DOF) is proposed based on the finite element method (FEM), while the partial sheet cavitation effects are considered. For this means, the steady cavity boundary is calculated by some conventional iterative procedures, developed based on the potential flow simulation. Thereafter, assuming that the amplitude and the frequency of the body oscillations are altered so that the cavity length in unsteady flow remains unchanged, the simulation of the unsteady hydrodynamic flow is performed by imposing some velocity fluctuations over the rigid cavity boundary. For...
Developing three dimensional potential solver for investigation of propulsion performance of rigid and flexible oscillating foils
, Article Ocean Engineering ; Volume 147 , 2018 , Pages 121-131 ; 00298018 (ISSN) ; Najafi, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Heave and pitch motion of an oscillating airfoil in uniform flow will cause generation of forwarding thrust. Applying a combination of these two motions on flexible foil, one can increase thrust and therefore the efficiency. This is the way that most fishes and other flying animals uses to consume less energy. In this paper, hydrodynamic forces and efficiency of an oscillating airfoil is investigated. A code is developed based on potential flow formulation in combination with Time Stepping Method (TSM) with nonlinear free shear layer dynamic approach to predict the wake behind the lifting bodies. A linear Morino type Kutta condition has been implemented on panels adjacent to trailing edge....
Impact of trim on added resistance of KRISO container ship (KCS) in head waves: An experimental and numerical study
, Article Ocean Engineering ; Volume 211 , 2020 ; Khorasanchi, M ; Day, S ; Turan, O ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study, added resistance and motion responses of KRISO Container Ship (KCS) were evaluated experimentally and numerically in six different trim angles. A series of towing tank experiments were performed for six different trim angles at design speed in calm water and regular head waves. The ship motions and added resistance were measured for several wavelength conditions considering short and long wave ranges with wave steepness of 1/60. Next, computations of the towed model in calm water and waves were performed using Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD and 3-D potential methods. Effects of trim angles on added resistance were analysed and results concerning the...
An efficient system identification approach to estimate unsteady loads on cavitator plates
, Article Ocean Engineering ; Volume 207 , 2020 ; Dehghani Firouz Abadi, R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
A new and efficient model for calculation of the unsteady hydrodynamic loads on an oscillating plate in two-dimensional flow is proposed. In order to compute the hydrodynamic loads, an unsteady hydrodynamic model is derived using the boundary-element method along with the potential flow assumption. To this aim, the steady boundary of cavity is determined by a full-nonlinear iterative procedure. Thereafter, assuming that amplitude and frequency of oscillations are so that the length of cavity in unsteady flow remains intact, simulation of the unsteady hydrodynamic flow is performed by imposing some velocity perturbations over the steady cavity solutions. Consequently, based on this...
New mathematical model to analysis fluid sloshing in 3D tanks with slotted middle baffle
, Article Ocean Engineering ; Volume 262 , 2022 ; 00298018 (ISSN) ; Firouz Abadi, R. D ; Amirzadegan, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
This work studies the natural frequencies and modes of liquid sloshing in a rectangular 3D tank with the slotted baffles in middle. A new vibrational model incorporating the pressure difference between the two sides of the baffle, using a transmission function in Laplace space is presented. To this end, a part of the baffle that includes the wall and the slot is modeled in Fluent software, to express this pressure difference as a function of the fluid velocity passing through the baffle. Then, using the boundary element method, and boundary conditions, the equations of the fluid domain are developed. In this research, the rigid baffle is surrounded by a three-dimensional irrotational...
A fluid-structure interaction model for stability analysis of shells conveying fluid
, Article Journal of Fluids and Structures ; Volume 26, Issue 5 , July , 2010 , Pages 747-763 ; 08899746 (ISSN) ; Noorian, M. A ; Haddadpour, H ; Sharif University of Technology
2010
Abstract
In this paper, a fluid-structure interaction model for stability analysis of shells conveying fluid is developed. This model is developed for shells of arbitrary geometry and structure and is based on incompressible potential flow. The boundary element method is applied to model the potential flow. The fluid dynamics model is derived by using an inflow/outflow model along with the impermeability condition at the fluid-shell interface. This model is applied to obtain the flow modes and eigenvalues, which are used for the modal representation of the flow field in the shell. Based on the mode shapes and natural frequencies of the shell obtained from an FEM model, the modal analysis technique is...
Comparing sloshing phenomena in a rectangular container with and without a porous medium using explicit nonlinear 2-D BEM-FDM
, Article Scientia Iranica ; Volume 17, Issue 2 B , 2010 , Pages 93-101 ; 10263098 (ISSN) ; Ghodsi Hassanabad, M ; Sharif University of Technology
2010
Abstract
The sloshing phenomena in a partially filled tank can affect its stability. Modifications of tank instability due to the movement of the tank carrier, are key design points for the stability of a carrier. Even though the sloshing phenomenon has already been investigated using the BEM-FDM technique, the research in this paper covers this phenomenon in a porous media, which is new in 2-D coordinates. For this purpose, a Laplace equation has been used for potential flow, and kinematic and dynamic boundary conditions have been applied to the free surface. Also, a formulation has been developed for a free surface in porous media. BEM has been used for solving the governing equation and FDM...