Abstract: The coupled oscillations of liquid in arectanqular tank with elastic spacer is investigated.Two different velocity potential functions corresponding respectively to the liquid above and belowthe elastic spacer are assumed. Complicated boundary conditions corresponding to two velocity popen- tial functions and oscillations of elastic spacer aregiven. Using the method of energy, the equation ofcoupled frequency is obtained. Through numericalcomputation the natrual frequency changes according to the location a...