This Letter tackles the issue of non-contact detection of ultrasonic fields by utilizing a novel optical method based on the parametric indirect microscopic imaging(PIMI) technique. A general theoretical model describ...This Letter tackles the issue of non-contact detection of ultrasonic fields by utilizing a novel optical method based on the parametric indirect microscopic imaging(PIMI) technique. A general theoretical model describing the three-dimensional anisotropic photoelastic effect in solid was developed. The mechanism of polarization status variations of light passing through the stress and strain fields was analyzed. Non-contact measurements of the ultrasonic field propagating in an isotropic quartz glass have been fulfilled by the PIMI technique under different ultrasonic excitation conditions. PIMI parameters such as sin δ, Φ, and the Stokes parameters have been found to be sensitive to ultrasonic fields.展开更多
This paper repotts an experimental investigation of the flow field inside a low aspect ratio dump combustor.The length of the combustor studied was less than the reattachment length for the separated flow.The exit of ...This paper repotts an experimental investigation of the flow field inside a low aspect ratio dump combustor.The length of the combustor studied was less than the reattachment length for the separated flow.The exit of the combustor is tapered which supports the flow reversal from the exit section.The flow field behaviour in the combustor is evaluated from pressure and velocity measurement studies.The velocity,stream function and pressure distribution inside the combustor are used to elucidate the presence of recircu lation and flow reversal from the exit section of the combustor for different Reynolds numbers.A small variation in Ums velocity was observed in axial direction while in the radial direction it was quite high.Two recirculation zones are recognized and the strength of the recirculation was seen to increase with flow Reynolds number.The turbulence intensity in the recirculation and shear layer zone was seen to be higher than the potential core.展开更多
基金supported by the National Key Research and Development Program of China(No.2017YFF0107100)the National Natural Science Foundation of China(NSFC)(Nos.61501239 and 51805268)+3 种基金the NSFC International Young Scientist Research Fund(No.61750110520)China Postdoctoral Science Foundation(No.2017M621745)Overseas Expertise Introduction Project for Discipline Innovation(111 Project)Zijin Professor Project of Nanjing University of Science and Technology
文摘This Letter tackles the issue of non-contact detection of ultrasonic fields by utilizing a novel optical method based on the parametric indirect microscopic imaging(PIMI) technique. A general theoretical model describing the three-dimensional anisotropic photoelastic effect in solid was developed. The mechanism of polarization status variations of light passing through the stress and strain fields was analyzed. Non-contact measurements of the ultrasonic field propagating in an isotropic quartz glass have been fulfilled by the PIMI technique under different ultrasonic excitation conditions. PIMI parameters such as sin δ, Φ, and the Stokes parameters have been found to be sensitive to ultrasonic fields.
基金This project is sponsored by ISRO and Space Technology Cell at Indian Institute of Technology,Kanpur.Mr.N.K.Gupta of LPSC is the project coordinator at ISRO。
文摘This paper repotts an experimental investigation of the flow field inside a low aspect ratio dump combustor.The length of the combustor studied was less than the reattachment length for the separated flow.The exit of the combustor is tapered which supports the flow reversal from the exit section.The flow field behaviour in the combustor is evaluated from pressure and velocity measurement studies.The velocity,stream function and pressure distribution inside the combustor are used to elucidate the presence of recircu lation and flow reversal from the exit section of the combustor for different Reynolds numbers.A small variation in Ums velocity was observed in axial direction while in the radial direction it was quite high.Two recirculation zones are recognized and the strength of the recirculation was seen to increase with flow Reynolds number.The turbulence intensity in the recirculation and shear layer zone was seen to be higher than the potential core.
