Fluid Interface 2D Shear Stress Flexible Sensor Under High Reynolds Coefficient

Shear stress in the fluid boundary layer is an important parameter reflecting the motion characteristics of the fluid.In the high Reynolds number boundary layer,the fluid flows in the form of micro-vortex,which causes the high-value two-dimensional(2D)shear stress to be present at the micro vortex junction.The existing sensors cannot measure the magnitude and direction of the shear stress in the high Reynolds number boundary layer of the fluid simultaneously.To solve this problem,this thesis presents a fluid interface 2D shear stress flexible sensor under high reynolds coefficient.The sensor is based on a Polymide(PI)substrate and four Nickel(Ni)thermal elements.These four Nickel thermal elements are arrayed in a fully symmetrical structure.And this sensor can measure the magnitude and direction of the 2D shear stress in the high Reynolds number boundary layer simultaneously.Specific research includes:(1)The mathematical models of fluid interface 2D shear stress flexible sensor under high reynolds coefficient are built.The 2D thermal shear stress sensor designed in this thesis can measure 2D shear stress in real-time.The 2D shear stress(F)can be decomposed into X-direction shear stress(_xF)and Y-direction shear stress(_yF).If the output voltage of sensor is U.This thesis will study the sensor structure to decouple F by using U.In other words,the function is solved:F=f(U).Specifically,the 2D shear stress decoupling model of the sensor is bulit and the equation is solved according to the experimental data.(2)The simulation model of fluid interface 2D shear stress flexible sensor under high reynolds coefficient are built based on the fluid simulation software FLUENT.In order to determine the optimal structure and size of the sensor,this thesis established the simulation model of fluid interface 2D shear stress flexible sensor under high reynolds coefficient based on the fluid simulation software FLUENT.The effects of the aspect ratio of the thermal element,the thickness of the substrate and the spacing on the sensor performance were analyzed.Finally,we fabricated a sensor sample based on the MEMS.(3)The response characteristics of fluid interface 2D shear stress flexible sensor under high reynolds coefficient.The traditional shear stress calibration experiment needs wind tunnel and shear stress measuring instrument.This method is not only costly,and the experimental environment is difficult to complete.For example,the thermal shear stress sensors made by HIT and Shanghai Jiaotong University did not complete the sensor calibration experiments.Therefore,we need to find a simple method to study the sensor response characteristics.In addition,we also studied the application of the 2D thermal shear stress sensor in the wind speed measurement,and analyzed the static response characteristics of the sensor.The 2D thermal shear stress sensor designed in this thesis can measure the shear stress in the range of 50mPa~340mPa and distinguish the direction of the shear stress.The TCR of the sensor is 0.002559/°C.The sensor output linearity(50mPa<?160mPa)is 2.8%.The sensor output linearity(160mPa<?340mPa)is 3.3%.The maximum measurement error of the sensor is 5.9mPa.The sensor can be used for microfluidic and aircraft design and other fields,to promote the progress and development of the industry is of great significance.