Consideration of Far Infrared Cameras for Measuring Surface Flow Velocity in Night Time.

---

Sanghyuk Kim, Kwonkyu Yu, Byungman Yoon, Inhyuk Bae, Byungnam Yu

Thursday 2 july 2015

16:15 - 16:30h at Africa (level 0)

Themes: (T) Special session, (ST) Acoustic monitoring of flow, turbulence and river discharge

Parallel session: 13F. Special session: Acoustic monitoring of flow, turbulence and river discharge

---

Large Scale Particle Image Velocimetry (LSPIV) method has shown a great deal of potentials to seamlessly measure streamflow discharge particularly in flood. The LSPIV utilized a pair of consecutive images recorded from cameras to estimate surface velocity. Its non-intrusive nature of measurements could be more advantageous especially in flood season when other intrusive instrumentations became difficult to apply due to dangerous field conditions. However, low quality of images usually recorded during night time affected the reliability of flow measurements using LSPIV, thus that this limitation has blocked the LSPIV method to be adapted as real-time discharge measurement system for national monitoring agencies. So far, extra light or near infrared camera have been attempted for resolving this issue, but the outputs were highly dependent on field conditions due to illumination and lack of tracers, respectively, and thereby limited to consistently provide reliable discharge measurements in night time. In this research, we adapted far infrared camera that provided remarkably visible images even better in night time. Flow movements interestingly generated different water surface temperatures, and they could be explicitly identified by far infrared cameras. The far infrared images obtained in a straight river channel during night time were analyzed using conventional LSPIV method and the results were in comparison with velocity measurements with respect to concurrent measurements by both propeller meter and ADCP. In addition, the results using normal and near infrared camera were also compared to differentiate their performance regarded with far infrared camera. The comparison results indicated that the velocity derived from LSPIV with far infrared camera matched well with those from propeller meter and ADCP. Therefore, it can be concluded that the capacity of LSPIV operation in night time were considerably enhanced when far infrared cameras were used.