• 대한기계학회논문집B
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• 제21권5호
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• pp.637-649
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• 1997

Effects of cone angle, pressure-hole orientation and Reynolds number on the five-hole probe calibration have been investigated for eight large-scale conical five-hole probes, which have either perpendicular pressure holes or forward-facing pressure holes for the cone angles of 45 deg, 60 deg, 75 deg and 90.deg. Pitch and yaw angles are changed from -40 deg to +40 deg with an interval of 5 deg, respectively, when the probe Reynolds numbers are 1.77*10$^{4}$, 3.53*10$^{4}$ and 7.06*10$^{4}$. The result shows that larger cone angle results in more sensitive changes in the calibration coefficients. In the case that the cone angle is 45 deg, the pitch-angle and yaw-angle coefficients of the five-hole probe with the perpendicular pressure holes show a very different trend compared with those of the five-hole probe with the forward-facing pressure holes. On the other hand, when the cone angle is more than 60 deg, each calibration coefficient is nearly independent of the pressure-hole orientation. Additionally, the effects of the Reynolds number on the calibration coefficients are also reported in detail.

• 한국정밀공학회지
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• 제21권7호
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• pp.179-184
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• 2004

In this work, a copper-clad aluminum composite was fabricated using hot hydrostatic extrusion with various extrusion ratios (8.5, 19, 49) and semi-die angles (30, 45, 60 degree) at a temperature of 32$0^{\circ}C$, Material characteristics of copper-clad aluminum composites were determined from compression tests and hardness tests The results showed that for ER of 8.5, the optimum semi-die angle was below or equal to 30 degree and a pressure drop was about 31%. For ER of 19, the optimum semi-die angle was in the range of 40 to 50 degree and a pressure drop was about 38%. In the case of ER=49, the optimum semi-die angle was above or equal to 60 degree and a pressure drop was about 36%. Compressive yield strength was maximum for ER of 8.5 and semi-die angle of 30 degree and the value of maximum was 155 MPa. Uniform hardness distribution was obtained as the extrusion ratio increases and the semi-die angle decreases. In the case of ER=8.5 and semi-die angle of 30 degree, the lowest extrusion pressure and the maximum compressive yield strength was obtained. Therefor, it was concluded that the optimum extrusion condition for fabricated copper-clad aluminum composites under hydrostatic pressure environment was ER of 19 and semi-die angle of 30 degree.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.218-224
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• 2011

A supersonic inlet at angle of attack has anti-symmetric pressure distribution, and it can make flow instability and structural problem. In this study, numerical analysis of three-dimensional inviscid flow was conducted under various throttle ratio and angle of attack conditions. Throttle ratio was defined as the ratio of the exit area to the smallest cross section area at inlet, and the ratio is controlled from 0 to 2.42. At various angle of attack, the characteristics of steady and unsteady flow around supersonic inlet is observed under different throttling ratios. From these results, pressure recovery curves and pressure history curves were plotted by post processing. Using pressure history data, FFT analysis is also carried out. Through these processes, it shows the tendency of pressure distribution anti-symmetricity and changing dominant frequency as increasing angle of attack.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.946-951
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• 2001

This experimental study is to investigate the intermittent spray characteristics of a pintle nozzle. High speed camera used in this expreiment with 9000fps. The factor, which controls the diesel spray, is the Injection pressure, ambient pressure and ambient temperature. In this paper, experiments were conducted free spray for the ambient pressure(3, 4, 5Mpa), nozzle Injection pressure(10, 14, 18MPa) and ambient temperature(293, 473K). With the higher opening pressure, the spray tip velocity and spray penetration increases while the spray angle decreases, On the other hand, With the higher ambient pressure, the spray angle increase while the spray tip penetration and spray tip velocity decrease. also, With the higher ambient temperature, the spray penetration decrease while the spray angle decrease.

• 한국유체기계학회 논문집
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• 제16권1호
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• pp.32-39
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• 2013

The multi-stage control valve is one of the devices which controls cavitation and high pressure drop. To attain the high pressure drop, the conventional control valves adopted the multi-stage trim to avoid the occurrence of local cavitation in valves. This work studied the effect of divergence angle on the characteristics of multi-stage trim. Pressure drop and flow characteristics was calculated for the 1 passage of multi-staged trim by using the FLUENT 6.3.26. The result showed that the pressure drop is significantly influenced by the divergence angle of multi-stage trim. In addition, the pressure drop increased consistently as the Reynolds number and divergence angle increases.

• 한국전문물리치료학회지
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• 제25권3호
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• pp.12-18
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• 2018

Background: Passive straight leg raising (PSLR) is the common clinical test to measure of hamstring muscle length. Hip flexion angle contributes to change the lumbopelvic rotation during PSLR. Pressure biofeedback unit (PBU) is commonly used to detect lumbopelvic movement during lower limb movements. Thus, there may be the relationship between pressure of PBU and lumbopelvic motion during PSLR. Objects: The objective of this study was to determine the relationship between pressure of PBU and lumbopelvic motion during PSLR. Methods: Thirty two subjects participated in this study. A three-dimensional motion analysis system were used to measure the lumbopelvic angle during PSLR, while recording the pressure of PBU according to angle of PSLR by 10 degree increments. Pearson product moment correlations and linear regression analysis were used to describe the relationship between variables. Results: The results showed that there was a significant relationship between the lumbopelvic and angle of PSLR (Pearson's r=.83, p<.05), between the pressure of PBU and angle of PSLR (Pearson's r=.75, p<.05), and between lumbopelvic motion and pressure of PUB (Pearson's r=.83, p<.05). Linear regression equation using lumbopevic angle as an independent factor was as follows: Pressure of PBU = 47.35 + (2.55 ${\times}$ angle of lumbopelvic motion) ($R^2=.69$, p<.05). Conclusion: Results of the present study indicate that pressure of PBU can be used to indirectly detect the amounts of lumbobevic motion during muscle length test or stretching of hamstring.

• 설비공학논문집
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• 제25권1호
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• pp.43-48
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• 2013

In this study, the performance of an impeller according to blade length and pitch angle was studied experimentally by building a variable pitch impeller while changing blade length to review the effect of blade length and pitch angle on a fan's performance. The pitch angle was changed in six steps from $20^{\circ}{\sim}45^{\circ}$ at intervals of $5^{\circ}$ while the blade lengths were changed to 90 mm, 100 mm, 110 mm and 120 mm with an identical airfoil shape while carrying out the experiment. The results are summarized as follows: The air flow per static pressure of axial fans increased linearly with increase of pitch angle, but the high static pressure showed a decrease at a pitch angle of $35^{\circ}$. The shaft power increased proportionally to the pitch angle at all blade lengths; the larger the pitch angle, the larger the measured increase of shaft power. This is because the drag at the fan's front increases with the pitch angle. In the axial fans considered in this research, the flow and increase of static pressure amount increased up to a pitch angle of $30^{\circ}$ but decreased rapidly above $35^{\circ}$.

• 한국콘텐츠학회논문지
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• 제10권2호
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• pp.268-276
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• 2010

본 연구의 목적은 경사로를 오르는 동안 슬관절 굴곡각도와 족저압의 차이를 각각 다른 경사도에 따라 분석하고자 하는 것이다. 24명의 건강한 성인 참가자들에게 각각의 경사도($0^{\circ},\;3^{\circ},\;6{\circ},\;9^{\circ}$)를 걷게 한 후, Parotec system을 이용하여 족저압을 측정하였으며, 걷는 모습을 캠코더로 녹화 한 후 Dartfish system을 이용하여 슬관절 각도를 분석하였으며, 수집된 데이터는 SPSS/PC 통계 프로그램을 이용하여 일원배치분산분석으로 분석하였다. 결과는 각 경사로에 따라 슬관절 굴곡 각도는 통계학적으로 유의한 차이가 나타났으며, 족저압은 좌측 하지의 발뒤꿈치 외측 부위(1번 감지기), 중족부 내측 부위(9번 감지기), 전족부 내측 부위(15번, 16번 감지기), 그리고 우측 하지에서는 발뒤꿈치 외측 부위(3번 감지기)에서 통계학적으로 유의한 차이를 보였다. 슬관절 각도가 $10{\sim}20^{\circ}$ 사이에서 발뒤꿈치 외측 부위 및 내측 부위의 족저압이 통계학적으로 유의하게 높게 나타났다.

• 동력기계공학회지
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• 제13권4호
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• pp.31-37
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• 2009

The purpose of this numerical study was to investigate performance characteristics for cooling tower axial fans with sweep. Performance data for the fans with various sweep angles were obtained in terms of the setting angle at a constant flow rate. Viscous flow calculations were carried out to obtain Performance data of the total pressure rise and hydraulic efficiency. A solution of the Ffowcs Williams-Hawkings equations was used to calculate the sound pressure level at three times fan diameter away from the fan. The calculated performance data well represented performance characteristics of the cooling tower axial fan. The total pressure rise and hydraulic efficiency at the same setting angle decreased with sweep angle. Sound pressure level slightly decreased for the fan with a sweep angle of 10 degree. No significant effect of the sweep geometry was found on the sound pressure level.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.426-431
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• 2001

This paper experimentally investigates the characteristics of dual coaxial jet issuing from inner supersonic nozzle and four kinds of outer converging nozzle of 40, 50, $60^{\circ}$ and $70^{\circ}$ in outer ejection angle. The pressure ratio of the stagnation to the exit ambient pressures in the inner supersonic nozzle of constant expansion rate is 7.5, which is corresponded to the condition of a slightly underexpanded, and that of outer nozzle is 4.0. Flow visualizations by using of shadowgraph method, impact pressure and centerline static pressure measurements are presented. It is found that the jet structure is changed significantly by the variation of outer nozzle ejection angle. Impact pressure level is lower and undulation of static pressure is higher, as the injection angle of outer jet increases.