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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >On the application of a supercontinuum white light laser for simultaneous measurements of temperature and velocity fields using thermochromic liquid crystals
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On the application of a supercontinuum white light laser for simultaneous measurements of temperature and velocity fields using thermochromic liquid crystals

机译：超连续素白光激光器在使用热致铬液晶的同时测量温度和速度场的应用

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Simultaneous velocity and temperature measurements using thermochromic liquid crystals (TLC) as tracer particles are discussed, with regard to measuring range uncertainty and spatial resolution. For the first time, a supercontinuum laser is used to illuminate these particles, which shall later be used for the characterization o the momentum and heat transfer in Rayleigh-Benard cells with high aspect ratio using particle image velocimetry (PIV) and particle image thermometry (PIT). Light scattered from the TLCs is analyzed by spectrometer measurements, revealing its general scattering characteristics depending on the angle between the light shee plane and the viewing axis. It is shown that white light sources with continuous spectral characteristic and a slightly higher fraction of light in the red wavelength range perform well, thereby the supercontinuum white light laser can be used, even though it has a cut-in wavelength of about 475 nm. The numerical aperture of the detection optics and chromatic aberrations of the laser light significantly affect the temperature sensitivity and dynamic range of the color of the TLCs. This may cause an effective temperature sensitivity range of about one-tenth of their nominal range, particularly at large angles between light sheet plane and viewing axis, a usually applied in PIV. A simultaneous velocity and temperature measurement in a Rayleigh-Benard cell experimentally validates that the use of the supercontinuum laser allows for reliable simultaneous PIV and PIT measurements with high spatial resolution of less than 500 mu m in out-of-plane direction, on condition that an appropriate two-dimensional calibration is applied.
机译：关于测量范围不确定性和空间分辨率，讨论了使用热致变色液晶（TLC）作为示踪剂颗粒的同时速度和温度测量。首次使用超强突发激光器来照亮这些颗粒，其后来应该用于使用粒子图像速度（PIV）和颗粒图像温度（PIV）和粒子图像温度（坑）。通过光谱仪测量分析从TLC散射的光，揭示其一般散射特性，这取决于光厚平面和观察轴之间的角度。结果表明，具有连续光谱特性的白光源和红色波长范围内的光略高，从而可以使用超连续的白光激光，即使它具有约475nm的切割波长。激光的检测光学和色差的数值孔径显着影响TLC颜色的温度灵敏度和动态范围。这可能导致其标称范围的约十分之一的有效温度敏感度范围，特别是在光板平面和观察轴之间的大角度，通常在PIV中应用。在瑞利百合电池中的同时速度和温度测量实验验证，超连续激光器的使用允许具有高于平面外方向小于500μm的高空间分辨率的可靠同时PIV和坑测量值施加适当的二维校准。

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