• 한국가시화정보학회지
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• 제4권2호
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• pp.44-50
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• 2006

A visualization study on the boundary layer and near-wake of an NACA 0012 airfoil was con-ducted in order to investigate the influence of boundary layer behavior on the near-wake at low Reynolds numbers. The present study is investigated at static angles of attack ${\alpha}=0^{\circ},\;3^{\circ},\;6^{\circ}$ and $Re=2.3{\times}10^4,\;3.3{\times}10^4,\;4.8{\times}10^4$ by using a smoke-wire technique. The results of this study show that the laminar boundary layer on the airfoil surface is attached to the surface at ${\alpha}=0^{\circ}$, and that laminar separation of boundary layer on the airfoil surface occurs at ${\alpha}=3^{\circ}$. Furthermore, reattachment of the boundary layer occurs in the case of ${\alpha}=6^{\circ}$. In the current study, the location of the laminar separation point moves upstream as the Reynolds number and the angle of attack increase.

• 한국항공운항학회지
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• 제14권4호
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• pp.24-30
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• 2006

An experimental study was carried out in order to investigate the influence of boundary layer behavior on the near-wake at low Reynolds numbers. An X-type hot-film probe(55R51) was used to measure the near-wake of an NACA 0012 airfoil at static angles of attack ${\alpha}=0^{\circ}$, $3^{\circ}$, and $6^{\circ}$, and the Reynolds numbers Re=2.3${\times}10^4$, 3.3${\times}10^4$, and 4.8${\times}10^4$. The results of the study show that the characteristics of the boundary layer on the airfoil surface have a close relationship with the mean velocity and turbulence intensity profiles of a near-wake. Therefore, the development of the boundary layer, the position of the separation point, and the existence and non-existence of reattachment on the airfoil surface were represented by the differences in mean velocity and turbulence intensity profiles of the near-wake.

• 한국대기환경학회지
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• 제12권4호
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• pp.459-472
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• 1996

An experimental investigation on the wind flow over smooth bell-shaped two-dimensional hills with hill slopes (the ratio of height to half width) of 0.3 and 0.5 is performed in an atmospheric boundary-layer wind tunnel. Two categories of the models are used in the present investigation; six two-dimensional single-hills, and four continuous double-hills. The measurements of the flow field and surface static-pressure distribution are carried out over the Reynolds number (based on the hill height) of 1.9 $\times 10^4, 3.3 \times 10^4, and 5.6 \times 10^4$. The velocity profiles and turbulence characteristics are measured by the pitot-tube and X-type hot-wire anemometer, respectively. The undisturbed boundary-layer profile on the bottom surface of the wind tunnel is reasonably consistent with the power-law profile with $\alpha = 7.0 (1/\alpha$ is the power-law exponent) and shows good spanwise uniformities. The profiles of turbulent intensity are found to be consistent along the centerline of the wind tunnel. The measured non-dimensional speed-up profiles at the hill crest show good agreements with the predictions of Jackson and Hunt's linear theory. The flow separation occurs in the hill slope of 0.5, and the oil-ink dot method is used to find the reattachment points in the leeside of the hill. The measured reattachment points are compared with the numerical predictions. Comparisons of the mean velocity profiles and surface pressure distributions between the numerical predictions and the experimental results show good agreements.

• Structural Engineering and Mechanics
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• 제40권1호
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• pp.29-48
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• 2011

Under large storm loads sections of a long pipeline on the seabed can be uplifted. Numerically this loss of contact is extremely difficult to simulate, but accounting for uplift and any subsequent recontact behaviour is a critical component in pipeline on-bottom stability analysis. A simple method numerically accounting for this uplift and reattachment, while utilising efficient force-resultant models, is provided in this paper. While force-resultant models use a plasticity framework to directly relate the resultant forces on a segment of pipe to the corresponding displacement, their historical development has concentrated on precisely modelling increasing capacity with penetration. In this paper, the emphasis is placed on the description of loss of penetration during uplifting, modelled by 'strain-softening' of the force-resultant yield surface. The proposed method employs uplift and reattachment criteria to determine the pipe uplift and recontact. The pipe node is allowed to become free, and therefore, the resistance to the applied hydrodynamic loads to be redistributed along the pipeline. Without these criteria, a localised failure will be produced and the numerical program will terminate due to singular stiffness matrix. The proposed approach is verified with geotechnical centrifuge results. To further demonstrate the practicability of the proposed method, a computational example of a 1245 m long pipeline subjected to a large storm in conditions typical of offshore North-West Australia is discussed.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.766-774
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• 2017

알루미늄과 같은 금속분말을 연료로 사용하는 추진체의 연료공급장치에 있어, 원통형 공급관 내부를 이동하는 분말이 연소기로 진입하면서 발생되는 분말의 급확대부 영역에서의 확산현상을 해석하기 위해 컴퓨터 소프트웨어를 개발하였다. 플러그 유동형태의 입자집단운동을 기술하기 위해서 일종의 Lagrangian기법이며 난류속도변동 조건을 만족하는 개별입자추적법을 도입하였다. 여기에 재순환 영역에서 유체의 방향전환을 증진시키기 위해 기하학적 유동 구조에 입각한 반경방향 속도성분을 추가시켰다. 속도 추가성분의 유무에 따른 급확대부 재부착점 부근에서의 입자 속도분포 수치해석 결과를 기존의 실험결과와 비교하였다.

• Journal of Microbiology and Biotechnology
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• 제21권11호
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• pp.1199-1202
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• 2011

Infection of surgical wounds is a severe problem. Conventional tissue reattachment methods have limits of incomplete sealing and high susceptibility to infection. Medical adhesives have several advantages over traditional tissue reattachment techniques, but still have drawbacks, such as the probability of infection, low adhesive strength, and high cytotoxicity. Recently, a new medical adhesive (new-adhesive) with high adhesive strength and low cytotoxicity, composed of aldehyded dextran and ${\varepsilon}$-poly(L-lysine), was developed. The antimicrobial activity of the new-adhesive was assayed using agar media and porcine skin. In the agar diffusion method, inoculated microorganisms that contacted the new-adhesive were inactivated, but this was not dependent on the amount of new-adhesive. Similar to the agar media results, the topical antimicrobial effect of new-adhesive was confirmed using a porcine skin antimicrobial assay, and the effect was not due to physical blocking based on comparison with the group whose wounds were wrapped.

• Archives of Plastic Surgery
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• 제36권5호
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• pp.660-662
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• 2009

Purpose: There are several modalities to reattach the amputated auricle. Microvascular replantation can achieve the best outcome, but technically difficult. Conventional composite graft is technically easy, but uniformly unsuccessful. Our successful experience of reattachment using postauricular subcutaneous pocket is presented. Methods: The amputated tissue was placed in its anatomical position with buried sutures. The amputated part is dermabraded to remove the epidermis and outer layer of dermis(Fig. 1, Center, left). Postauricular skin flap was then raised and the reattached dermabraded ear was buried beneath the flap(Fig. 1, Center, right). Two weeks after the original surgery, the buried ear was removed from its pocket (Fig. 1, Below, left). Results: The ear was reepithelialized spontaneously in 7 days. At 3 months, the reattached ear has satisfactory appearance without contour deformity(Fig. 1, Below, right). Conclusion: This technique provides increase in contact surface between the amputated segment and the surrounding tissues which supply blood, serum, oxygen and nutrients, maximizing the probability of "take". Minimally injured dermis can be healed from spontaneous reepithelialization and provides minimal contour deformity. We have used this non-microsurgical technique with very satisfying outcome.

• Archives of Reconstructive Microsurgery
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• 제14권2호
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• pp.112-116
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• 2005

The auricle is easy to be amputated in the face due to its protruding position. When facial parts are amputated, the mechanism of injury usually involves some form of avulsion, which damages these fragile vessels over a distance and renders them unsuitable for anastomosis. Replantation of the ear remains a challenging problem because of the tiny vessels and the paucity of adequate veins for anastomosis. Reattachment as a composite graft of the total or subtotal amputated ear is unreliable. Microsurgical replantation can be performed in a minority of cases because of technical difficulties and long operation time. In this article, the authors report two case of a successful ear replantation of completely amputated auricle. Only one artery and one vein were anastomosed in first case. In the other case one artery was anastomosed without vein. Instead of venous repair, multiple incision was done with leech application therapy. and the outcome was successful. In spite of the technical difficulties and long operation time, microsurgical replantation of amputated ear is better than other reconstructive method or reattachment without microsurgery.

• 대한족부족관절학회지
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• 제25권2호
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• pp.95-99
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• 2021

The surgical treatment of Achilles tendinopathy can be considered after the failure of conservative treatment, and the surgical methods may be divided into two groups; treatments for insertional and non-insertional tendinopathy. In the case of insertional tendinopathy, debridement including tendon and calcification of the diseased lesion, reattachment of the tendon, and calcaneal ostectomy of the Haglund lesion are the primary treatments. If reattachment is not possible, reconstruction should be performed by other methods such as tendon transfer. As a result of surgery for insertional tendinopathy, there is an improvement in the pain and function after surgery, but there are some patients whose pain does not completely disappear. Some residual pain may persist; therefore, the overall success rate of the surgery can be expected to be 80% to 90%. For the patients of non-insertional tendinopathy, conservative treatment through eccentric exercise is the primary treatment, and most of them have reported good results. In case of failure after various conservative treatments, debridement of the diseased lesion and repair of the remaining tendon would be the primary surgical treatments. If the remaining tendon is not sufficient, reconstruction such as tendon transfer should be considered.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1023-1032
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• 2003

The effect of local forcing on the separated flow over a backward-facing step is investigated through hot-wire measurements and flow visualization with multi-smoke wires. The boundary layer upstream of the separation point is laminar and the Reynolds number based on the free stream velocity and the step height is 13800. The local forcing is given from a slit located at the step edge and the forcing signal is always defined when the wind tunnel is in operation. In case of single frequency forcing, the streamwise velocity and the reattachment length are measured under forcing with various forcing frequencies. For the range of 0.010〈S $t_{\theta}$〈0.013, the forcing frequency component of the streamwise velocity fluctuation grows exponentially and is saturated at x/h = 0.75 , while its subharmonic component grows following the fundamental and is saturated at x/h = 2.0. However, the saturated value of the subharmonic is much lower than that of the fundamental. It is observed that the vortex formation is inhibited by the forcing at S $t_{\theta}$ = 0.019 . For double frequency forcing, natural instability frequency is adopted as a fundamental frequency and its subharmonic is superposed on it. The fundamental frequency component of the streamwise velocity grows exponentially and is saturated at 0.5 < x/ｈ < 0.75, while its subharmonic component grows following the fundamental and is saturated at x/ｈ= 1.5 . Furthermore, the saturated value of the subharmonic component is much higher than that for the single frequency forcing and is nearly the same or higher than that of the fundamental. It is observed that the subharmonic component does not grow for the narrow range of the initial phase difference. This means that there is a range of the initial phase difference where the vortex parring cannot be enhanced or amplified by double frequency forcing. In addition, this effect of the initial phase difference on the development of the shear layer and the distribution of the reattachment length shows a similar trend. From these observations, it can be inferred that the development of the shear layer and the reattachment length are closely related to the vortex paring.