Thermographic study of turbulent water pulsations in nonisothermal mixing

Abstract

The possibilities of using thermography for quantitative studies of the frequency characteristics of the nonisothermal water pulsations near the vessel walls transparent to infrared radiation are analyzed. Thermographic studies of the temperature dynamics in the contact zone of a nonisothermal liquid with the wall were performed using simple models. Frequencies of temperature fluctuations at the inner surface of the vessel through the wall transparent to infrared radiation were measured using a thermal imager with accurate focusing of the lens. Spectral curves of the fluctuations were constructed with the use of a Fourier transform. It is shown that Kolmogorov spectra (−5/3 law) are present in the nonisothermal flow in a T-junction channel, allowing the process to be characterized as developed turbulence of the water flow in the region of the boundary layer adjacent to the window.

Thermographic Analysis of a Turbulent Nonisothermal Water Boundary Layer

“…The water flow rate through each nozzle varied from 10 to 55 ml/s. The average flow velocity was up to 1,3 m/s, which corresponded to the flow Reynolds number of approximately 1,7x10 4 . In all the experiments the time-evolving temperature maps of the water mixing processes were recorded by a calibrated, mid-wave (3,7-4,8 μm) infrared camera (FLIR Systems SC7700).…”

“…A vast variety of techniques and methods, both numerical and experimental, has been used to address the different aspects of turbulence and turbulent flows. Recently, a new research technique has been proposed to study non-isothermal pulsations of turbulent water boundary layers based on highspeed thermographic measurements through IR-transparent windows [3,4]. Since a thin layer of liquid water absorbs almost all the IR-radiation, the time-evolving temperature maps of near-wall boundary layers can be recorded by using IR-transparent vessel walls.…”

Measuring the Temperature and Stress-Strain States of a Tube Sample under the Local Stochastic Temperature Pulsations

“…Особый интерес в последние годы представляют термопульсации, сопровождающие процессы смешения рабочих сред водоохлаждаемых реакторных установок (РУ). В открытой печати встречается большое количество публикаций, посвященных исследованию смешения потоков теплоносителя в Т-образном [2][3][4][5][6] и других тройниковых соединениях различных конструкций [7][8]. В большинстве своем эти работы объединяет применение бесконтактных методов измерения полей температуры и скорости таких, как инфракрасная термография, цифровая трассерная визуализация (английская аббревиатура PIV) и др.…”