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Effect of Crosswind on Derailment of Railway Vehicles Running on Curved Track at Low Speed
Hosoi, Takahiro,Tanifuji, Katsuya The Korean Society for Railway 2012 International Journal of Railway Vol.5 No.2
Owing to the lightening of railway vehicles and increased operation speeds, the reduction of running safety in the presence of crosswind is becoming an important problem. In particular, the running safety tends to decrease when vehicles run on curved track. When a crosswind acts on a vehicle negotiating a curve from the outer side, flange climbing can occur. In this study, a full-vehicle model was constructed using the multi-body simulation software SIMPACK, and a simulation of a bogie vehicle with two-axle trucks negotiating a curve was carried out to examine the running safety under the condition where a crosswind acts on the vehicle from the outer side of the curve. As a result, it was verified that the derailment coefficient of the first wheelset becomes large in the exit transition curve and the coefficient of the third wheelset does in the entrance transition curve, and this trend becomes pronounced at low operation speeds in the presence of a stronger crosswind. It was also shown that the critical derailment coefficients obtained by modified Nadal's formula considering the effect of attack angle become close to the actual derailment coefficients at the timing that flange climbing occurs.
Effect of Crosswind on Derailment of Railway Vehicles Running on Curved Track at Low Speed
Takahiro Hosoi,Katsuya Tanifuji 한국철도학회 2012 International Journal of Railway Vol.5 No.2
Owing to the lightening of railway vehicles and increased operation speeds, the reduction of running safety in the presence of crosswind is becoming an important problem. In particular, the running safety tends to decrease when vehicles run on curved track. When a crosswind acts on a vehicle negotiating a curve from the outer side, flange climbing can occur. In this study, a full-vehicle model was constructed using the multi-body simulation software SIMPACK, and a simulation of a bogie vehicle with two-axle trucks negotiating a curve was carried out to examine the running safety under the condition where a crosswind acts on the vehicle from the outer side of the curve. As a result, it was verified that the derailment coefficient of the first wheelset becomes large in the exit transition curve and the coefficient of the third wheelset does in the entrance transition curve, and this trend becomes pronounced at low operation speeds in the presence of a stronger crosswind. It was also shown that the critical derailment coefficients obtained by modified Nadal’s formula considering the effect of attack angle become close to the actual derailment coefficients at the timing that flange climbing occurs.
Takahiro Ishida,Keisuke Ohira,Rio Hosoi,Naoko Tokugawa,Takahiro Tsukahara 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.4
Extensive research to establish an index of roughness that causes abrupt turbulent transition downstream of the roughness and affect natural laminar flow is performed. This study investigates turbulent transitions dominated by the roughness-induced crossflow instability on a swept wing and a swept flat plate. Direct numerical simulations (DNS) are performed considering the swept wing to determine the critical roughness height that induces abrupt turbulent transition. Compared to its no-roughness counterpart, the roughness increases both the pressure drag and skin-friction drag and decreases the lift owing to the onset of upstream turbulence. The wind tunnel tests are performed considering a swept flat-plate boundary-layer model. The development of turbulent regions due to the roughness is investigated. The results reveal the occurrence of a laminar-to-turbulent transition and relaminarization, along the boundary between laminar and localized turbulent regions. Moreover, the DNS results reveal the generation of traveling crossflow vortices from the localized turbulent region.
Takamasa Takahashi,Yuji Kaneoka,Atsuyuki Maeda,Yuichi Takayama,Hiroki Aoyama,Takahiro Hosoi,Kazuaki Seita 대한내시경로봇외과학회 2023 Journal of Minimally Invasive Surgery Vol.26 No.2
Purpose: In minimally invasive esophagectomy (MIE), it is important to reduce the rate of anastomotic leakage to ensure its safety. At our institute, the double-ligation method (DLM) has been introduced to insert and fix the anvil of the circular stapler for intracorporeal circular esophagojejunostomy in gastric surgery. We adopted this method for intrathoracic anastomosis (IA) in MIE. The aim of this study was to investigate the safety of IA with DLM in MIE. Methods: In this study, 48 patients diagnosed with primary middle or lower third segment thoracic esophageal carcinoma with clinical stage I, II, III or IV disease were retrospectively evaluated. Postoperative outcomes were assessed. Results: Among the 48 patients, 42 patients underwent laparo-thoracoscopic esophagectomy and IA using a circular stapler with the DLM. The average total operation time and thoracoscopic operation time were 433 and 229 minutes, respectively. The average pursestring suturing time was 4.7 minutes. The rates of anastomotic leakage and stenosis were 2.4% and 14.3%, respectively. The overall incidence of postoperative complications (Clavien- Dindo grade of ≥III) was 16.7%. The average postoperative stay was 16 days. Conclusion: The procedure of IA using a circular stapler with the DLM in MIE was safe and provided a low rate of anastomotic leakage.