Experimental Measurement Of Bulk Viscosity Of Water Based On Stimulated Brillouin Scattering

Stimulated Brillouin scattering(SBS) is one of the important research direction ofnon-linear optics, and has particular advantage in hydrological monitoring. Therelationship among the line width of SBS，shear viscosity, bulk viscosity and relaxation.On the basis of theoretical analysis, the bulk viscosities of fresh water and simulatedseawater with different salinities have been measured respectively.Bulk viscosity is an important parameter of hydrology information. This paperpresents a new method for measuring bulk viscosity based on stimulated Brillouinscattering. The relationships among shear viscosity, bulk viscosity, thermal capacity,and the line-width were deduced theoretically, and the relation between SBS line widthand bulk viscosity has been found. The signal-noise-ratio (SNR) of scattering light hasbeen improved by using the singal receiving system that consisted of cylinder lens, F-Petalon and ICCD.In order to measure the line-width of SBS under different tempertures,the lasers was focused into a sink with constant temperature. The experimental resultsshow that the measurement precision by using SBS method has been improved oneorder of magnitude compared with that of spontaneous Brillouin scattering.The linewidth of SBS and bulk viscosity decrease fleetly with the increase of temperatureincreases when the temperature is below25℃, after which it slows down. On the basisof theoretical research and experiental measurement,the measurement errors have beenanalyzed, the results show that, compared with the measurements of spontaneousbrillouin scattering, SBS has unique advantages in improving the SNR, reducing errorsand feasibility, and is an accurate method for measuring the bulk viscosity of watert.