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Finite element analysis of 2D turbulent flows using the logarithmic form of the k-ε model
Hiroshi Hasebe,Takashi Nomura 한국풍공학회 2009 Wind and Structures, An International Journal (WAS Vol.12 No.1
The logarithmic form for turbulent flow analysis guarantees the positivity of the turbulence variables as k and ε of the k-ε model by using the natural logarithm of these variables. In the present study, the logarithmic form is incorporated into the finite element solution procedure for the unsteady turbulent flow analysis. A backward facing step flow using the standard k-ε model and a flow around a 2D square cylinder using the modified k-ε model (the Kato-Launder model) are simulated. These results show that the logarithmic form effectively keeps adequate balance of turbulence variables and makes the analysis stable during transient or unsteady processes.
Finite element analysis of 2D turbulent flows using the logarithmic form of the κ-ε model
Hasebe, Hiroshi,Nomura, Takashi Techno-Press 2009 Wind and Structures, An International Journal (WAS Vol.12 No.1
The logarithmic form for turbulent flow analysis guarantees the positivity of the turbulence variables as ${\kappa}$ and ${\varepsilon}$ of the ${\kappa}-{\varepsilon}$ model by using the natural logarithm of these variables. In the present study, the logarithmic form is incorporated into the finite element solution procedure for the unsteady turbulent flow analysis. A backward facing step flow using the standard ${\kappa}-{\varepsilon}$ model and a flow around a 2D square cylinder using the modified ${\kappa}-{\varepsilon}$ model (the Kato-Launder model) are simulated. These results show that the logarithmic form effectively keeps adequate balance of turbulence variables and makes the analysis stable during transient or unsteady processes.
Takuji Yamagami,Rika Yoshimatsu,Hiroshi Miura,Tomohiro Matsumoto,Terumitsu Hasebe 대한영상의학회 2013 Korean Journal of Radiology Vol.14 No.3
Objective: To determine the safety and usefulness of a two-tiered approach to balloon-occluded retrograde transvenous obliteration (B-RTO) as a treatment for large gastric varices after portal hypertension. Materials and Methods: 50 patients were studied who underwent B-RTO for gastric varices between October 2004 and October 2011 in our institution. The B-RTO procedure was performed from the right femoral vein and the B-RTO catheter was retained until the following morning. Distribution of sclerotic agents in the gastric varices on fluoroscopy was evaluated in all patients on days 1 and 2. When distribution of sclerotic agents in the gastric varices on day 1 had been none or very scanty even though the volume of the sclerotic agent infused was above the acceptable level, a second infusion was administered on day 2. When distribution was satisfactory, the B-RTO catheter was removed. Results: In 8 (16%) patients, little or no sclerotic agent infused on day 1 was distributed in the gastric varices. However, on day 2, sclerotic agents were distributed in all gastric varices. Mean volume of ethanolamine oleate-iopamidol infused on day 1 was 24.6 mL and was 19.4 mL on day 2. Gastric varices were well obliterated with no recurrence. Complications caused by the sclerotic agent such as pulmonary edema or renal insufficiencies were not seen. Conclusion: When gastric varices are very large, a strategy involving thrombosis of only the drainage vein on the first day followed by infusing the sclerotic agent on the following day might be effective and feasible.