Sharif Digital Repository

A numerical model based on the boundary element method is proposed for the sloshing of a flowing liquid in a three-dimensional tank. Assuming a mean flow in the tank in addition to a perturbation flow, the nonlinear boundary conditions of the liquid free-surface are linearized. Using the boundary element method along with the modal analysis technique a reduced order model is obtained which is used to calculate the fundamental sloshing frequencies and modes in the tank with an inlet and outlet. The obtained results for a test case are compared with the literature data to validate the proposed model. The results are in a very good agreement with analytical results and show an acceptable... 

This study presents a method to determine an equivalent mechanical model (EMM) for multi-baffled containers with arbitrary geometries. The method is implemented for 2D and axisymmetric containers. The Laplace equation and Green's theorem are used to develop the fluid model and the boundary element method (BEM) is used to solve the fluid field governing equation. Moreover, a zoning method is utilized to model arbitrary arrangements of baffles in multi-baffled containers and a reduced order model is developed to model the free-surface sloshing. The exerted hydrodynamic pressure distribution, forces and moments on the walls of the container are determined based on the Bernoulli equation and a... 

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  

In order to study the interaction of sloshing and structural vibrations of baffled tanks, a reduced order model based on modal analysis of structure model and boundary element method for fluids motion is developed. For this purpose, the governing equations of elastic structure and incompressible flow are used to derive simple models to simulate both fields. Using the modal analysis technique, the structural motions are applied to the fluid model and on the other hand by using boundary element method, the fluid loads are applied to the structural model. Based on this formulation, a code is developed which is applicable to an arbitrary elastic tank with arbitrary arrangement of baffles. The... 

The sloshing behavior of systems is influenced by different factors related to the liquid level and tank specifications. Different approaches are applicable for the assessment of sloshing behavior in a tank. In this paper, a new numerical model based on the differential quadrature method and boundary element approaches is adopted to investigate the sloshing behavior of a tank with an elastic thin-walled beam. The model is developed based on small slope considerations of the free surface. The main assumption of fluid modeling is homogeneity, isotropy, inviscid, and only limited compressibility of the liquid. Indeed, the formulation is represented based on the reduced-order method and then is... 

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 numerical model is developed for investigation of coupled dynamics of fuel contained elastic launch vehicles in planar atmospheric flight. Finite element method along with the linear quasi-steady piston aerodynamic theory is used for developing an aeroelastic model. A reduced order boundary element model is used for modeling the liquid sloshing in tanks. The interaction of sloshing and aeroelasticity is studied using stability analysis of the coupled system. Results show that the slosh-aeroelastic coupling in an elastic launch vehicle occurs for low tank filling ratios and may lead to decreasing the system damping. Due to more interactions between the slosh and rigid body modes, larger... 

This paper presents the application of reduced order modeling technique for investigation of liquid sloshing in three-dimensional tanks. The governing equations of sloshing are written using a boundary element formulation for incompressible potential flow. Then, the governing equations are reduced to a more efficient form that is represented only in terms of the velocity potential on the liquid free surface. This particular form is employed for eigen-analysis of fluid motion and the sloshing frequencies and mode shapes are determined. Then, the sloshing frequencies and the corresponding right- and left-eigenvectors are used along the modal analysis technique to find a reduced order model... 

Due to significance of high-accuracy attitude control, the fuel sloshing effects on the satellite attitude should be considered, more precisely. This work deals with the attitude control of a liquid propellant-filled satellite considering the incompressible fuel sloshing in the planar maneuver. The satellite consists of a rigid body, a partially-filled tank and a flexible diaphragm. Hamilton's principle is employed to derive nonlinear coupled PDEs-ODEs governing the coupled satellite-diaphragm propellant tank system. Afterwards, to dispense with the spillover instability, a PDE-based controller is designed to realize the satellite attitude control while tracking a desired pitch angle and... 

Sloshing, or liquid free surface oscillation, in containers has many important applications in a variety of engineering fields. The modal method can be used to solve linear sloshing problems and is the most efficient reduced order method that has been used during the previous decade. In the present article, the modal method is used to solve a nonlinear sloshing problem. The method is based on a potential flow solution that implements a two-phase analysis on sloshing in a rectangular container. According to this method, the solution to the mass conservation equation, with a nonpenetration condition at the tank walls, results in velocity potential expansion; this is similar to the mode shapes...