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CFD investigation on the flatback airfoil effect of 10 MW wind turbine blade
정재호,김수현 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.5
The flatback airfoil effect on the inboard region of a large wind turbine blade was investigated by numerical analysis. Complicated flow phenomena in wind turbine blade with flatback and non-flatback airfoil were captured by Reynolds-averaged Navier–Stokes flow simulation with shear stress transport turbulence model. Although both airfoil blades were designed using blade element momentum theory to produce identical shaft power, results of three-dimensional computational fluid dynamics (CFD) flow analysis indicated that at a specific location of the root area, the flatback airfoil improved the inboard force by approximately 6 % compared with the non-flatback airfoil. We were also able to confirm that by using the flatback airfoil, the overall shaft power throughout the blade increased by 1 %, thereby restraining the bending moment exerted by the thrust force on the hub by 0.5 %. Moreover, numerical analysis results indicated that the flatback airfoil blade reduced the size of the secondary vortex around the blade root area and its progress in the secondary direction in comparison with the non-flatback airfoil blade. The shape of the flatback airfoil on the trailing edge weakened the adverse pressure gradient migrating from the lower to the upper surface. Regardless of the flatback airfoils, the tip vortex core of the outboard region formed on the suction surface leading edge and strongly rolled up by the pressure surface boundary layers due to the large pressure difference between the suction and pressure surfaces in the blade tip region. This remarkable strong tip vortex developed downstream and raked up the boundary layer of the blade trailing edge with low energy.
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정재호,유희진,황나현,김덕우,윤을식 대한두개안면성형외과학회 2016 Archives of Craniofacial Surgery Vol.17 No.3
Background: Conventional correction of malunioned zygoma requires complete regional exposure through a bicoronal flap combined with a lower eyelid incision and an upper buccal sulcus incision. However, there are many potential complications following bicoronal incisions, such as infection, hematoma, alopecia, scarring and nerve injury. We have adopted a zygomaticofrontal suture osteotomy technique using transconjunctival incision with lateral paracanthal extension. We performed a retrospective review of clinical cases underwent correction of malunioned zygoma with the approach to evaluate outcomes following this method. Methods: Between June 2009 and September 2015, corrective osteotomies were performed in 14 patients with malunioned zygoma by a single surgeon. All 14 patients received both upper gingivobuccal and transconjunctival incisions with lateral paracanthal extension. The mean interval from injury to operation was 16 months (range, 12 months to 4 years), and the mean follow-up was 1 year (range, 4 months to 3 years). Results: Our surgical approach technique allowed excellent access to the infraorbital rim, orbital floor, zygomaticofrontal suture and anterior surface of the maxilla. Of the 14 patients, only 1 patient suffered a complication—oral wound dehiscence. Among the 6 patients who received infraorbital nerve decompression, numbness was gradually relieved in 4 patients. Two patients continued to experience persistent numbness. Conclusion: Transconjunctival incision with lateral paracanthal extension combined with upper gingivobuccal sulcus incision offers excellent exposure of the zygoma-orbit complex, and could be a valid alternative to the bicoronal approach for osteotomy of malunioned zygoma.
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사람 귀 연골 세포주와 조직공학술을 이용한 신생 연골의 재생
정재호,김승업,박병윤,박명철,임현이,이명애,홍현석 대한성형외과학회 2003 Archives of Plastic Surgery Vol.30 No.5
The purpose of these studies was an establishment of human auricular chondrocyte cell line using retrovirus mediated v-myc transfer, characterizing the human auricular chondrocyte cell line by type II collagen mRNA expression and transplantation of human auricular cell line into immunological incompetent nude mice to establish neocartilage formation. Also, I evaluated the growth rate of chondrocyte cell line to measure the cellular proliferative potency. I have established the human auricular chondrocyte cell line integrated v-myc and confirmed by v-myc transduced Myc protein expression by immunohistochemistry and immunoblotting study. And, growth rate of established human auricular chondrocyte cell line increased 4 folds times faster than primarily cultured human auricular chondrocyte. The established human auricular chondrocyte had type II collagen mRNA upto 8 months in monolayer culture. And we observed formation of neocartilage on the back of nude mice using chondrocyte cell line/fibrin glue polymer at 12 weeks transplantation.
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정재호 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
This paper elucidates three-dimensional flow phenomena that induce aero-acoustic noise at certain frequencies. Three-dimensional separated and vortical flow fields in an air conditioning system are investigated by Experimental fluid dynamics (EFD) analysis using an unsteady wall pressure measurement system with 30 high-respond pressure transducers and by Computational fluid dynamics (CFD) analysis using a Reynolds-averaged Navier-Stokes (RANS) simulation with a k-ε turbulence model. The EFD investigation revealed that the regions with high wall pressure fluctuation are located near the scroll tongue and on the bottom of the diffuser casing wall. A wall pressure fluctuation of 0.056 Blade passing frequency (BPF) was observed at sensor A near the scroll tongue, and a wall pressure fluctuation of 0.173 BPF was observed on part of the evaporator casing wall. The CFD investigation revealed that the reverse flow is generated by interaction between the scroll tongue and multi-blade fan. The reverse flow develops strongly over a wide range in the multi-blade fan near the scroll tongue. Furthermore, there is also a longitudinally separated vortex near the bottom of the diffuser casing. The reverse flow and longitudinally separated vortex interact with the wall casing. For this reason, the scroll tongue and the bottom of the diffuser casing had high pressure fluctuations in the EFD investigation. By considering aero-acoustic factors, an aerodynamic sound of 0.056 BPF can be explained by Helmholtz resonance phenomenon, which is generated by high pressure fluctuation due to the reverse flow near the scroll tongue. An aerodynamic sound of 0.173 BPF can be explained by the standing wave phenomenon, which is generated by high pressure fluctuation due to the longitudinally separated vortex on the bottom of the diffuser casing wall.
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정재호,황용재,정승필,박승하,윤을식 한국유방암학회 2021 Journal of breast cancer Vol.24 No.3
Purpose: Women with large and/or ptotic breasts are generally not considered candidates for nipple-sparing mastectomy because of concerns regarding the high incidence of postoperative complications including ischemic complications. Therefore, we adopted a vertical skin resection technique for nipple-sparing mastectomy, and obtained satisfactory results following immediate autologous breast reconstruction. In this study, we aimed to describe our operative technique and review its outcomes. Methods: Between January 2010 and March 2017, immediate autologous breast reconstructions were performed in 28 patients with moderate or large ptotic breasts after nipple-sparing mastectomy using the vertical reduction pattern. Grade II ptosis was observed in 12 patients, and 16 patients were classified as having grade III ptosis. Results: Of the 28 patients, 21 received abdominal free flap reconstruction. In the remaining 7 patients, extended latissimus dorsi flaps were used in conjunction with anatomic implants. The mean weight of the excised breast tissue in the 2 groups was 575 g and 482 g, respectively. Satisfactory esthetic outcomes without major complications were achieved in all patients. Similar vertical reductions or mastopexies in the contralateral breast allowed better postoperative adjustment for symmetry. There was only 1 case of complete nipple necrosis; however, the problem was solved with “skin banking.” No local recurrences or distant metastases were detected at follow-up (mean 18 months, range 4 months to 6 years). Conclusion: To enhance cosmetic outcomes in patients with large and/or ptotic breasts, the vertical skin resection pattern for nipple-sparing mastectomy can be used to achieve better breast shape while preserving the nipple-areola complex. Moreover, it can improve the esthetic outcome without compromising oncologic safety.
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안면골 골절에서 상하악 치열궁 복원을 위한 양측 대구치간 철사견 인술의 유용성
정재호,김용하,이준호,신승규 대한성형외과학회 2009 Archives of Plastic Surgery Vol.36 No.1
Purpose: Palatal fracture and mandible fracture result in instability of dental arch. Because they divide the maxillary and mandibular alveolus sagittally and / or transversely and comminute the dentition, they permit rotation of dental alveolar segments and significantly increase the potential for fracture malalignment, complicating fracture treatment. Previous treatment of palatal fracture consisted of palatal splint application and rigid palatal vault stabilization. This procedure result in patient’s oral discomfort and removal of palate and screw. Mandible fracture often results in malocclusion due to widening of posterior aspect of dental arch. So we introduce simpler method using intermolar traction wiring, which can protect the widening of dental arch and rotation of dental alveolar segment. Methods: Arch bar and intermolar traction wiring with wire 1-0, or 2-0 was applied. After exposure of fracture line, neutroclusion was maintained with intermaxillary fixation. And then open reduction & internal fixation on maxillary fracture line, commonly maxillary buttress, alveolar ridge, pyriform aperture except palatal vault or mandibular fracture line. After 1 week, intermolar traction wiring was removed. We checked occlusion and postoperative radiologic finding. Results: From June 2007 to October 2007, 10 patient, who have maxillary fracture with palatal fracture and mandible fracture, underwent open reduction & internal fixation with intermolar traction wiring. All have satisfactory occlusion and there were no complication, like gingiva disease, mouth opening impairment and nonunion. Conclusion: The intermolar traction wiring accompany open reduction and internal fixation can be an alternative method for restoration of dental arch in facial bone fracture.
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