抄録
Temperature-sensitive liquid crystals are used to visualize an instantaneous temperature field close to the wall associated with the organized motions in a flat plate turbulent boundary layer without pressure gradient. A very thin liquid crystal membrane has been attached on the wall surface, which is heated with a constant heat flux in a low-speed water channel. By virtue of the color change of liquid crystals with the simultaneous hydrogen-bubble flow visualization, the existence of high- and low-temperature streaks near the wall is revealed. The high-temperature streaks are mostly associated with the so-called low-speed streaks, and the low-temperature streaks with the high-speed streaks. The measured spanwise spacing of high-temperature streaks is 81υ/u*, while the streamwise length is confirmed to be more than 1000υ/u*. These observations provide new evidence regarding the turbulent heat transfer mechanism in the wall region of turbulent boundary layers.
