Study On The Problems Of Liquid Sloshing In The Tank With Elastic Wing Bulkheads

Liquid sloshing is of great engineering significance with regard to the safety of the transportation systems. The sloshing problem is associated with any moving vehicles partially filled with liquid. Violent sloshing can be expected if the tank motion contains energy in the vicinity of the lowest natural frequency for the fluid inside the tank. Large amplitude fluid movements could create highly localized impact pressure on the bulkhead, which may cause structural failure, or even produce enough bending moment to make it instability. Liquid sloshing is a very complex phenomenon of fluid motion, which is highly nonlinear. Because of the complexity of the problem, its theoretical analysis is not perfect so far, and it has been the hot research topic in the field of aerospace, shipbuilding, etc all the time.The image acquisition and analysis technology is further developed in the sloshing test. The real-time data of the free surface variation in the tank is obtained, and the non-contact measurement for the strongly nonlinear free surface flow is realized. Through the pressure acquisition system, the sloshing pressure acting on the elastic wall is measured. By the fiber bragg grating sensor demodulation instrument, the strain data with high precision and stability is obtained. The lowest order natural frequency of the liquid in the tank is determined through the sweep test.The model test has been conducted to study the liquid sloshing in the elastic tank under the horizontal harmonic excitation. Different liquid depths, excitation frequencies and amplitudes are considered. The hydrodynamic behaviors of the free surface elevation and the sloshing pressure in the ealstic tank are analyzed. The results are compared with the experimental results and the theoretical calculations in the rigid tank. The analysis finds that, the free surface elevation at each measuring point in the elastic tank and that in the rigid tank are close to each other. While the peak values of the sloshing pressure acting on the elastic tank at the location below the static liquid level are smaller than that on the rigid tank by8-16%.The structural dynamic response of the elastic tank is analyzed. The wave shape in the elastic tank under the finite depth is described, and the variational characteristics of the structral strain are analyzed from the time and the frequency domain. The time variation and the space distribution characteristics of the structural train are further dissected. The research shows that, the double-peak characteristic is presented obviously in time history of the strain. In the resonant case, on the tank roof, the larger strains are more likely to happen in the corner; and on the bulkhead, the maximum tensile and compressive strain are appeared in the location of the static liquid level and under the static liquid level respectively. The Morlet continuous wavelet transform is adopt to do the nonlinear analysis of the free surface elevation and the sloshing pressure in the elastic tank. The time-frequency variations of the wavelet energy spectrum at different measuring points in the elastic tank are discussed. Results show that, the main wavelet energy of the sloshing pressure are distributed in locations of the excitation frequency or double-times frequency; while in the area that the frequency is greater than three-times or four-times frequency, the energy distribution of the wavelet energy spectrum shows the impulse characteristics obviously.