Showing 7 results for Sloshing
Naser Khaji, Mohammad Hossein Arab,
Volume 12, Issue 2 (6-2012)
Abstract
Nowadays, fluid storage tanks are as important as fluids in urban life. The dynamic behavior of this important structure is different from common structures. Baffles as a passive control device can reduce the effects of sloshing which reduces the structural response to seismic excitation. In this study, the effect of baffles on seismic response of cylindrical vertical liquid storage tanks is investigated. The considered baffle is an annular plate with constant level from the base and constant inner diameter fixed on wall of the tank. Considering Laplace equation as the governing equation of fluid domain, and using boundary element method, a rigid tank is analyzed in the frequency and time domains. Afterwards, the baffle effects on natural frequency (in the frequency domain), and on base shear and overturning moment (in the time domain) due to El Centro and Erzincan earthquakes are investigated. Based on the results of mentioned analyses, it is observed that when the baffle is installed, the natural frequency of liquid domain reduces. Moreover, by installing the baffle, the base shear slightly increases whereas overturning moment remarkably reduces.
Volume 14, Issue 8 (11-2014)
Abstract
This study is investigated vibration analysis of a FG rectangular plate partially contacting with a bounded fluid. Wet dynamic transverse displacement of the plates is approximated by a set of admissible trial functions which is required to satisfy the clamped (CL) and simply supported moveable (SSM) and simply supported immoveable (SSI) geometric boundary conditions. The oscillatory behavior of fluid is obtained by solving the Laplace equation and satisfies the boundary conditions. The natural frequencies and mode shapes of the plate coupled with sloshing fluid modes are calculated by using the Rayleigh–Ritz method based on minimizing the Rayleigh quotient. The proposed method is validated with available data in the literature. In the numerical results, the effects of volume fraction coefficient, thickness ratios and aspect ratios of the FG plates and depth of the fluid, width of the tank, and boundary conditions on the wet natural frequencies are examined and discussed in detail.
Volume 19, Issue 6 (6-2019)
Abstract
Sloshing phenomenon is one of the complex problems in free surface flow phenomena. Numerical methods as a new method can be used to solve this problem. In these methods, the lack of a mesh and complex elements the domain of problems due to the change in geometry of the solution over time provides a lot of flexibility in solving numerical problems. In the previous researches, the sloshing problem reservoirs , using the Laplace equation with respect to the velocity potential, but the solution to this problem with pressure equations has not much considered; therefore, using the pressure equations and a suitable time algorithm, generalized exponential basis function method has been developed for dynamic stimulation reservoirs. The approximation is solved, using a meshless method of generalized exponential basis functions and the entire domain of problem will discrete to a number of nodes and then with appropriate boundary conditions, the unknowns are approximated. In this study, linear and nonlinear examples have been solved under harmonic stimulation, in two-dimensional form of rectangular cube tanks, and the results of them have been compared with the analysis solving methods, other numerical methods, and experimental data. The results show that the present method in two-dimensional mode is very noticeable compared with other available methods because of accuracy in solving problem and spending time.
Volume 19, Issue 8 (8-2019)
Abstract
The aim of this article is to present the methodology for modeling and simulation of start effects in spacecraft or satellite's propulsion system on the fuel sloshing in the tank by pendulum model in microgravity conditions. In other words, the main aim of this paper is pure sloshing study of fuel and ullage gas relative movement, neglecting the role of Propellant Management Device (PMD). To this end, fuel sloshing in tank is performed by utilizing the Fluent software based on pendulum model. Firstly, algorithm inputs are determined (exiting input, fuel and ullage gas volume, loading, dimensional specifications, etc.); then, tank is modeled and designed and, finally, fuel sloshing simulation in micro-gravity conditions is developed. Fuel sloshing modeling and simulation outputs include determining the sloshing damping rate and its value in the simulation at 20 sec, velocity variation contour, velocity direction contour in the tank, and also ullage gas and fuel relative location in 0.2, 0.4, and 1 sec. The accuracy of the obtained results has been evaluated with the similar experimental results.
Volume 19, Issue 9 (9-2019)
Abstract
Fuel sloshing is one of the most important factors in disturb attitude of the spacecraft from desire in orbital maneuver. So, controlling this phenomenon is a critical problem in attitude control. There are active and passive control methods to control fuel sloshing. Active method has better responses to control fuel sloshing and its effect on attitude of the spacecraft in the same time; so, mostly this method is used. For this aim, it is necessary to model slosh dynamic. In this paper, slosh dynamic is modeled by a multi-pendulum model, and, then, coupled equations of the spacecraft and fuel slosh dynamic are derived. In the presented model, pendulums can move freely in 3D atmosphere, and this matter makes presented model closer to real. Coupled equations of the spacecraft and fuel slosh dynamic are nonlinear. Therefore, nonlinear control methods should be used to attitude control in more realistic mode. In this paper, two candidate Lyapunov functions are proposed; then, using these functions, controllers are obtained. The effectiveness of these controllers on attitude of the spacecraft and pendulums is described by a simulation. Although, there are some little differences in time responses based on two controllers, results of simulation illustrate good responsibility of controllers to control aims.
Volume 20, Issue 2 (1-2020)
Abstract
The motion of the liquid free surface in a container (sloshing phenomenon) inserts a momentum on the container walls. This makes a great disorder in the movement of the carrier vehicle or inserts a large force and momentum on the container walls. The reason for this phenomenon is the establishment of destructive waves and hydrodynamic forces. The side effects of this phenomenon in various industries, such as ship industries carrying liquid fuels, liquid fuel rocket industries, fuel tanks or water tanks, increase the importance of predictions of the behaviors of this phenomenon. One way of controlling is to use baffles or plates in the transverse direction of the tank. In this study, the governing equations on this phenomenon have been solved using the OpenFOAM software. This software solves partial differential equations using the finite volume method, which by default considers geometry to be three dimensional. In order to solve the two-phase flow, a modified volume of the fluid model (VOF) is applied and the moving mesh model is used for the movement of the container body. In the VOF method, the phases are expressed as a fraction of one (volume fraction). To determine this parameter, based on the continuity equation, a differential equation is regulated and solved. For the turbulent flow model, a modified k-e model is used by considering the effects of free-surface flows. Also, an experimental model of a real moving liquid container has been used for validation of the predictions of the presented simulation. The results show that the experimental and numerical results are in good accordance. In addition, the results show that using vertical baffles up to 50% can reduce the fluctuations caused by this phenomenon.
Volume 21, Issue 9 (9-2021)
Abstract
Roll motion is one of the most important and dangerous motions of the ship and can even result in capsizing of the vessel. Therefore, its control has been always of interest for marine industry researchers. Among the various methods and equipment for controlling the roll motion, the use of free surface anti-roll tanks has been one of the most important methods and which used in many cases due to its simplicity in construction and design. The high efficiency of these tanks at all speeds and even without speed is another strength of these tanks. This study investigates the effect of the free surface anti-roll tank on the roll motion numerically and experimentally. In the numerical simulation, a CFD sloshing solver, based on the “Open source Field Operation And Manipulation”, known in short as Open-FOAM, and assuming 2D laminar flow conditions, is customized to calculate the sloshing loads from the tank. The predicted roll damping and moments due to the anti-roll tank are validated against experimental results. This simulator could be used as a sloshing simulator to couple with seakeeping solvers.
