• The KSFM Journal of Fluid Machinery
• /
• v.16 no.3
• /
• pp.39-47
• /
• 2013

Effect of semicircular rib or groove on the performance of a rim-seal was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations. The turbulence was modeled using the one-equation Spalart-Allmaras turbulence closure model. Reynolds number based on the axial chord of the turbine blade was 500,000 at the mainstream outlet. The numerical results for a sealing effectiveness was validated in comparison with experimental data. To examine the effect of the semicircular rib or groove on sealing effectiveness of the rim-seal, location and diameter of the rib or groove were selected as the parameters to be performed. The rim-seals with the semicircular groove showed a higher sealing effectiveness than that with the semicircular rib. The semicircular groove installed on the stator side showed best sealing effectiveness among the numerical simulation results.

• 한국전산유체공학회:학술대회논문집
• /
• 2002.05a
• /
• pp.128-133
• /
• 2002

The heat transfer characteristics of a turbulent flow in a ribbed two-dimensional channel have been investigated numerically. The fully elliptic governing equations, coupled with a four-equation turbulence model, $\kappa-\omega-\bar{t^2}-\epsilon_t$, are solved by a finite volume method of SIMPLE type. Calculations have been carried out for three rib cross-sections : square, triangular, and semicircular, with various rib pitches and Reynolds numbers. The procedure appears to be satisfactory as the results for the square rib compare favorably with available experimental data and earlier calculation. The optimal rib pitch that yields the maximum heat transfer has been identified. It is also found that the square rib is most effective in enhancing the heat transfer. The semicircular rib, on the other hand, incurs the least amount of pressure drop but the improvement in heat transfer is substantially lower.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.1
• /
• pp.149-157
• /
• 1999

Heat transfer in a duct is augmented remarkably by rib turbulators. However, increasing friction loss is accompanied due to ribs disturbing flows. Hence, pressure drops and heat transfer are considered simultaneously to decide heat/mass transfer performance in a rib-roughened duct. In the present study, the effects of rib cross section shape on pressure drop through a duct are investigated as well as those on heat transfer characteristics. The results show that the characteristics of heat/mass transfer and friction loss in the duct roughened with triangular ribs are similar to those with square ribs, while significantly different from those with semicircular ribs. The best performance in the duct is obtained by using semicircular shaped ribs among three types of ribs for the large rib angles of ${\alpha}{\geq}63^{\circ}$.

• Journal of Power System Engineering
• /
• v.15 no.5
• /
• pp.43-48
• /
• 2011

The article represents an experimental investigation on friction and turbulent flow characteristics of free airflow through a rectangular duct fitted with semicircular ribs of uniform height (e = 3.5 mm) on one principle wall. The aspect ratio of the rectangular duct was AR= 5 where the duct height (H) was of 30 mm. Four different rib pitches (P) of 28 mm, 35 mm, 42 mm and 49 mm were used for constant rib height to hydraulic diameter ratio (e/Dh = 0.07) and constant rib height to channel height ratio (e/H = 0.11). The experimental results show some significant effects on pressure drop as well as turbulent characteristics at various configurations among different numbers of rib arrangements varying Reynolds number in the range of 15000 to 30000. Pressure transducer and hot wire anemometer were used for data acquisition of this experiment.

• Journal of Chest Surgery
• /
• v.21 no.4
• /
• pp.782-786
• /
• 1988

We experienced plastic reconstruction of tuberculous bronchostenosis with patient`s rib cartilage. He suffered from coughing and sputum for 2months, and was treated for pulmonary tuberculosis 10 years ago. In preoperative bronchoscopy, left main bronchus was fibrotic obstructive and LUL bronchus was severely destructed. After thoracotomy, we harvested the rib cartilage at the 6th rib, and designed semicircular and tubular graft. And then onlayed the graft over the longitudinal bronchotomy site by simple interrupted sutures with 4-0 Vicryl Postoperative course was good, coughing and sputum disappeared. In postoperative bronchoscopy, the patch graft was good in that position, and the internal diameter was sufficient, but the granuloma was found in the stoma of LUL bronchus. He was discharged without any other event.