Inferring thermal turbulent structures properties in the wake of an array cylindrical obstacles

¹ Al-Mustensiriyah University, Civil Engineering Department, Baghdad, Iraq
² Cardiff University, Cardiff School of Engineering, Hydro-environmental Research Centre, Cardiff, UK

^* Corresponding author: irrigation_2010@yahoo.com

Abstract

In this study a thermal camera was used to inferring the properties of thermal turbulent structures at the water surface of an array of emergent vertical cylindrical obstacles located in staggered fashion at one side of an open channel flow. Three different diameters (D = 1.25 cm, 2.5 cm and 5.0 cm) were tested. A thermal camera SC640 was used to record a series of snapshots of the water surface temperature distribution in the wake of the cylinders at section where the flow was uniform and fully developed. The selection was made after watching a video to locate the most suitable areas for eddies and turbulence development. For the selected location, temperature values were extracted for each sequence at five selection points in the wake region using Matlab software. Time series of temperature for the snapshots of the five selected points in the area of eddy formation were drawn. The energy of the eddies were extracted using Fourier transforms. The results showed successive peaks with a slope of - 5/3. Evaluation of the eddies in the wake of the cylindrical rods showed that the energy of the eddies is small at high frequency and large eddies were observed at low frequencies.