Measurement Of Fluctuating Pressure In Turbulent Boundary Layer Based On Optical Fiber Sensor

During the navigation of underwater vehicle,a turbulent boundary layer will form on its surface,and the vortex interaction in the turbulent boundary layer will generate fluctuating pressure.The fluctuating pressure not only stimulates the structural vibration of the underwater vehicle to generate noise,but also acts as a sound source to emit flow noise that spreads outward,seriously damaging the concealment of the underwater vehicle.Therefore,the measurement and research of fluctuating pressure are of great significance.In order to measure the fluctuating pressure in the turbulent boundary layer and realize the measurement of high wavenumber range,this paper makes a fluctuating pressure sensor array based on the sensing principle of fiber F-P interferometer,and applies it to the experimental pipeline system for measurement.Combined with fluid simulation,the fluctuating pressure in the turbulent boundary layer is analyzed.Firstly,geometric modeling is conducted for the experimental pipeline,and the relative positions between each sensing unit in the sensing array and the installation position of the array in the experimental pipeline are determined.Monitoring points are set at the corresponding positions;The large eddy simulation method is used to carry out fluid mechanics simulation calculation on the pressure data of monitoring points under different flow velocity conditions,convert the calculated fluctuating pressure space-time data into wavenumber-frequency spectrum,and analyze the wavenumber frequency spectrum under different combination of monitoring point arrays and different flow velocity conditions.Secondly,the solid mechanics simulation method is used to calculate the influence of the relevant parameters of the sensing unit on the sensitivity and natural frequency of the sensing unit,determine the parameters of the sensing unit,and calculate the influence of the spacing between adjacent sensing units on each other’s crosstalk;According to the parameters determined by solid mechanics simulation and the arrangement of monitoring points in fluid mechanics calculation,the fluctuating pressure sensor array is made,and the sensor array is calibrated.Finally,the experimental pipeline was installed in a low noise experimental pipeline system,and the fluctuating pressure sensing array was installed flush inside the experimental pipeline.A sensing array demodulation system was established to measure the fluctuating pressure at the wall of the experimental pipeline.Through the measurement of fluctuating pressure under different conditions,the wavenumber-frequency spectrum corresponding to the sensor array is calculated,which verifies the conclusions obtained from fluid mechanics simulation calculation under the same conditions,and explains the practicability of the fluctuating pressure sensor array made in this article.In this article,based on the principle of optical fiber sensing,a fluctuating pressure sensing array is made to ensure high sensitivity of the sensing array and reduce the size of the sensing unit compared with the electrical sensor,so as to achieve high spatial resolution measurement of the fluctuating pressure in the turbulent boundary layer.