Mechanism Curved Plate Wave Measurement Of Liquid Density

Density reflects the physical characteristics of the materials. In many fields of industrial production and social life, the accurate measurement of the liquid density is needed. In some special occasions, such as oilfield exploration, biomedical, lightwork brewing industry, the density of the liquid inside the equipment is need to measure through a small aperture. Density of the liquid in the wells is a very important parameter in the field of oil well logging. The oil density parameter is detected in real time by drilling, which can determine the value of the oil well. The measurement of the liquid density is one of the methods for logging outputs sectional measurement. Based on the basis of existing methods, combined with actual production needs of oil well logging, the bending vibration of thin circular plate is used to measure the liquid density in this paper. The method can resolve the problems of the traditional densitometer, such as the low measurement accuracy of output profile logging density distribution, the small measuring range and the large repeatability errors.The main research work of this paper is as follows:(1) Based on the theory of flexural vibration of the thin circular plate, the numerical simulation model of the bending vibration of the thin circular plate in the liquid is setup, and the equation of the liquid’s density measured by the bending vibration of a thin plate in liquid is deduced. That is:(2) The1-6mode flexural vibration frequency of thin circular plate in the air and unilateral or bilateral water are computed. The effects of the thin circular plate’s radius, thickness, material and fluid density on the flexural vibration characteristics of thin plate are analysed. The simulation results show that:the vibration frequency of the vibration system is the highest in the air, then in the unilateral water, the last in the bilateral water. The larger the radius of thin plate is, the lower the frequency of vibration is. The greater the thickness of thin circular plate is, the higher the frequency is.(3) Using the finite element methed, the vibration characteristics of thin circular plate is analysed. The1～6mode flexural vibration frequency of the radiation pattern of thin circular plate unilateral or bilateral water are calculated. By compare the simulation results with theoretical results,we verified the theoretical results. According to the simulation results, we conclude that the rule of the1～6mode of flexural vibration frequency of thin circular plate in the air is:f�'�>f铝>f镍>f铜,the rule of the vibration frequency in unilateral or bilateral water is:f�'�>f镍>f铜>f铝,the changed rule of resonance frequency difference is:△f铝>△f�'�>△f镍>△f铜·(4) According to the result of finite element simulation, seven thin circular plates with different sizes and materials are made. The bending vibration frequency in atmosphere and liquid of thin circular plates are measured experimentally. According to the results, the liquid density using the relationship between thin circular plate’s blending vibration frequency and liquid density are calculated,. The theoretical modal and the result of finite element simulation are verified. The method of testing liquid density using blending vibration of thin plate is proved by our study. This research will provide the basis for acoustic methods on applying liquid density testing. This also proved the method of using curved plate’s wave to test liquid density is available.