Prof. Koji OKAMOTO
Topic: Progress and Future of High-speed Quantitative Visualization
Quality of high-speed camera had been improved dramatically in this decade. Complicated phenomena under extremely severe environment can be visualized and quantized very easily. Nowadays, 100kHz sampling images with enough image resolutions are widely used. The sensitivity of the image capturing devise, e.g., C-MOS, is also improved drastically. Several applications on the high-speed imaging with quantitative evaluation will be discussed.
Particle Image Velocimetry (PIV) technique is now widely used just combining high-speed camera and CW laser sheet. Also, using the oversampled images, individual tracer trajectories have been detected with higher accuracy. Temporal oversampling may reduce the error for particle tracking, resulting in the accurate measurements.
PIV coupled with Temperature Sensitive Paint (TSP) will reveal the temperature and velocity distributions simultaneously. The functional tracer particle may also improve the techniques.
Reviewing the previous quantitative technique, the future of Quantitative Visualization will be discussed.
Prof. Choongsik BAE
Topic: Diagnostics on spray and combustion process of alternative fuels in optical engines
The depletion of conventional fossil fuels and concern of harmful pollutants have forced automobile industry to seek alternative fuels for internal combustion engines. The utilization of alternative fuels for instance liquid petroleum gas (LPG), jet propellant 8 (JP-8) and biodiesel fuels for internal combustion engines is being considered in many countries. However, component manufacturers design fuel injectors for conventional petroleum based fuels, which have different fuel properties with alternative fuels. The injector effectiveness is greatly influenced by the different fuel properties such as density, viscosity and surface tension. Furthermore, the combustion processes in spark-ignition (SI) engine and compression ignition (CI) engine are greatly affected by fuel atomization and air-fuel mixing process. Thus, there is a need to understand the effect of fuel properties on spray and combustion. In this study, spray and flame characteristics of alternative fuels were investigated based on high-speed imaging. The LPG was introduced as an alternative fuel for SI engine, meanwhile, JP-8, biodiesel and gasoline fuels were introduced as alternative fuels for CI engine. At first, spray characteristics of alternative fuels were investigated in a constant volume chamber (CVCC). The macroscopic spray process was characterized from Mie-scattering and shadowgraph images in terms of spray tip penetration length, and spray angle. For a detailed study of the spray formation in the near-nozzle region, a long-distance microscopy (LDM) was also performed. A series of engine test with alternative fuels was carried out in optically accessible engines. The engine performance and emission characteristics were compared with base fuels. Finally, flame characteristics of alternative fuels were studied based on direct high-speed imaging in optical engines.
Prof. Irina ZNAMENSKAYA
Topic: Digital Imaging in Flow Visualization and CFD simulation
Progress (revolution) in digital imaging in recent years launched the process of mutual influence of CFD and experimental flow visualization and image processing. The opportunities presented by the use of comparison of the experimental flow visualization, image processing and CFD visualization are discussed. Examples of comparison of numerical and experimental flow visualization, obtained by different imaging techniques are shown: PIV images, schlieren, BOS, thermography, discharge visualization, high speed shadowgraphy of shock waves, etc. Comparison of numerical and experimental patterns may be successfully used for CFD validation, physical process model correction, experiment improving. Digital convergence of experimental and computational visualization provides an opportunity to apply new methods of image processing to experimental data with purpose to define flow structures and to trace them with high accuracy. Application of image processing methods and CFD visualization can be also useful for elimination of experimental artifacts in results. Digital numerical and experimental flow fields visualization matching is shown to be an effective tool for the analysis of hydrodynamic processes in complex 2D and 3D non-stationary flows.
Prof. Gennaro CARDONE
Topic: Thermo-fluid-dynamic analysis by infrared thermography: a review
Infrared thermography (IRT) has been used for many years in many fields and for many different purposes. This because of its many advantages over contact transducers. In particular, it has proved its capability to deal with thermo-fluid-dynamic problems also in presence of complex fluid flow configurations. In fact, IRT is non-intrusive, has high sensitivity (down to 10mK) and fast response (up to 3kHz), is fully two-dimensional allowing for a better evaluation of errors due to radiation and tangential conduction within the heat flux sensors. By appropriate choice of the device, IRT can be exploited to resolve convective heat fluxes within both steady and transient conditions. This work would be an overview on the use of infrared thermography in thermo-fluid-dynamics. It includes: a background to the radiation theory, an overview of the main IR cameras features, a description of the pertinent heat flux sensors and an analysis of the IR image processing methods. At last, some examples of convective heat transfer measurements in also complex fluid flows, involving either very low (natural convection), or very high (hypersonic regime) speeds, are described.
Prof. Tai-Wen HSU
Topic: Application of BIV and PIV Techniques to Breaking Wave-Induced Flow Fields over Artificial Reef
This thesis use Particle Image Velocimetry (PIV) and Bubble Image Velocimetry (BIV) to measure the various complex flow phenomena surrounding an artificial reef owing to its interaction with an oncoming wave. Based on the experimental results, the wave height of progressive wave decreases gradually with the increase of the distance of artificial reef. When wave breaking, the wave take the air into water and have air bubble. The air bubble velocity constantly decrease by the bubble impact in front of water. In breaking wave, surround of waterline’s field, the velocity is more faster than surround of structure. And the scope of this phenomenon increase gradually with the increase of the distance of artificial reef.