scholarly journals Investigation of Coherent Vortices in Partly Vegetated Open-channel Flows with a Particle-Image Velocimetry

1998 ◽  
Vol 1 ◽  
pp. 719-728
Author(s):  
Iehisa NEZU ◽  
Kouki ONITSUKA ◽  
Hideki JOHMEN ◽  
Yuki SAGARA ◽  
Kazuya IKETANI
Keyword(s):  
Particle Image Velocimetry ◽  
Open Channel ◽  
Particle Image ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Image Velocimetry ◽  
Coherent Vortices

scholarly journals Visualization of Coherent Vortices Generated behind Dune in Unsteady Open-Channel Flows

1997 ◽  
Vol 41 ◽  
pp. 663-668
Author(s):  
Iehisa NEZU ◽  
Akihiro KADOTA ◽  
Hideki SHINBASHI ◽  
Masa-aki KURATA
Keyword(s):  
Open Channel ◽  
Channel Flows ◽  
Open Channel Flows ◽  
Coherent Vortices

PIV Analysis of the Flow Pattern Around an Ablation Catheter to Observe the Flow Effect on the Electrode

2013 ◽  
Author(s):  
Kaihong Yu ◽  
Tetsui Yamashita ◽  
Shigeaki Shingyochi ◽  
Kazuo Matsumoto ◽  
Makoto Ohta
Keyword(s):  
Blood Flow ◽  
Particle Image Velocimetry ◽  
Catheter Ablation ◽  
Flow Pattern ◽  
Open Channel ◽  
Particle Image ◽  
Circulation System ◽  
Convection Flow ◽  
Image Velocimetry ◽  
Catheter Tip

Radiofrequency (RF) catheter ablation is a highly effective treatment for many cardiac arrhythmias, especially for tachyarrhythmia. RF energy is introduced through the catheter onto the endocardial surface to destroy the abnormal heart tissue causing the heart rhythm disorder. Many parameters relate to myocardial temperature, such as RF power, tissue contact, and blood flow. Blood flow is an important factor that has a cooling effect on myocardium and affects the final lesion size. Many previous studies have shown that under temperature control, lesion sizes are larger and tissue temperatures rise faster with a high flow rate. If the flow causes a decrease in the temperature of the catheter tip, the generator will increase the power output to maintain the tip at a constant temperature. However, few studies of RF catheter ablation have investigated how ablation affects blood flow. Observation of the flow pattern around the catheter can help to determine the mechanism of the flow effects on the temperature of the catheter tip. The purpose of this study is to observe the flow pattern during ablation using an in-vitro circulation system developed for Particle Image Velocimetry (PIV). We developed an open-channel circulation system to simulate blood flow. The mold for the open-channel was built with acrylic boards for transparency. The working fluid was 0.9% saline, which was used at room temperature (20°C). Instead of animal myocardium, we used a poly (vinyl alcohol) hydrogel (PVA-H), which has mechanical characteristics that approximate those of biological soft tissue, and contact with the PVA-H surface by the catheter is similar to that with myocardium. A 7 Fr catheter with a 4-mm ablation electrode tip was set perpendicular to the PVA-H surface, and the contact weight between the electrode of the catheter and the PVA-H surface was 2.2 gf. To measure the temperature profile in the PVA-H, a K-type thermocouple with the diameter of 0.5 mm was placed at the depth of 2 mm from the surface. The thermocouple tip was always placed on the catheter axis. The flow pattern at the location where the catheter was held was observed by a high speed camera, and the resulting images were analyzed by particle image velocimetry (PIV). The results showed that in the absence of applied flow, convection flow from the electrode is observed in the areas around the catheter. However, under a 1.6 L/min flow rate, convection flow disappears. In conclusion, blood flow could decrease the catheter tip temperature, and the influence of ablation in the flow around the catheter disappeared.

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