| Author | Zubery, Shamim Ahsan |
| Call Number | AIT Thesis no.ST-95-4 |
| Subject(s) | Damping (Mechanics)
|
| Note | A thesis submitted in partial fulfilment of the requirement for the degree of Master of Engineering. |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. ST-95-4 |
| Abstract | An analytical model of liquid sloshing is developed to describe the sloshing characteristics of liquid in an annular-shape tank when subjected to horizontal vibration. A new approach based on the concept of generalized coordinates and velocity potential has been used in the formulation. The fo1mulation is limited to the case of sloshing in its fundamental antisymmetric mode, which is the most effective mode to be used in damper applications, and with small sloshing amplitude. By the use of Lagrange's energy approach, the governing equations of motion can be obtained in the form of linear, second order differential equation. The free surface, sloshing force, velocity and pressure distribution of sloshing fluid at any point can be described by the model. Extensive experiments have been conducted on a scaled annular TLD on shaking table to confirm the validity of the proposed analytical model. Tests have been conducted both with and without screens. The natural frequency and damping have been observed from free oscillation test; the frequency response of sloshing force, free surface elevation and phase difference between sloshing force and excitation have been measured from forced oscillation tests. Fairly good agreement has been found between experiment and the proposed model. Also a couple of experiments have been carried out to find out the effects due to long time immersion of screens, pa11icularly on damping ratio and frequency. It was found that the inherent damping of water is too low as compared to the optimal damping r~quired for real damper application. For this reason it is necessary to add flowdampen devices to increase damping. From experiment it is found that wire mesh is a suitable dampening device. It is necessary to predict analytically the additional damping from the resistance characteristics of the flow-dampen device, because for some real application damping prediction may not be possible by experiment (which is the best way to find damping). An analytical solution to predict the additional damping due to screen has been formulated using Morison's formula regarding the forces on a obstacle in a flow path together with energy-ratio concept. The drag coefficient of screen is necessary in the prediction of damping from the above formulation. A number of simple flow resistance tests have been conducted to find the drag coefficient of screen. It has also been tried in the model to predict damping due to baffles (frame) with the same concept. With these fo1mulations damping due to flow-dampen devices can be predicted to some extent. This study is believed to provide some very important information regarding the practical design of an annular TLD and also some necessary steps for a more professional and careful way of a experimental investigation. |
| Year | 1995 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. ST-95-4 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai |
| Examination Committee(s) | Worsak Kanok-Nukulchai;Wijeyewickrema, Anil Christopher |
| Scholarship Donor(s) | Asian Institute of Technology Partial |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1995 |