Dynamic surface heat transfer and re-attachment flow measurement using luminescent molecular sensors

Abstract

Luminescent molecular sensors, which can be used as Temperature Sensitive Paint (TSP) or Pressure Sensitive Paint (PSP) in respective temperature or pressure measurements, has been proved to be one promising surface quantity measurement technology in recent years. It is advantageous in the experiments with complicated surface and is able to give flow field information such as surface flux and wall shear-stress. The current study is focused on the dynamic heat transfer measurement of a backward-facing step model, using luminescent molecular sensors as temperature probe. The effects of flow separation and re-attachment after a back-step model were experimentally discussed in wind tunnel tests. The experimental system was consisted of a molecular sensor calibration system, a dynamic data recording system and a data processing system. It is found that the reattachment process will form a low temperature region, which then gives the clear temperature field of the flow. Dynamic temperature field data show a re-attachment position around x/h = 5.7, which agrees well with oil-flow measurements as well as previous experiments. The dynamic temperature fluctuation data is discussed with the vibrations of flow and transient heat transfer behaviors after the backward step, which then is used in the analysis of surface wall shear-stress variations. It is concluded that the current luminescent molecular sensor method is capable of quantitative measurement for surface heat transfer and fluid flows.