• 대한기계학회논문집B
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• 제21권11호
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• pp.1449-1457
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• 1997

Since a non-nulling method of five-hole probes is valid only when the flow angle is within the calibrated angle range, it can not be used in a complex flow field. Full angle range pressure coefficient maps show that widely used nulling methods do not guarantee correct alignment of the probe with the flow direction in the unknown complex flow field. Zone decision method and features of zone map were studied by investigating the full angle range pressure coefficient maps. A reliable and efficient new nulling algorithm using zone decision by pressure ordering is proposed and verified. Since the zone decision method by pressure ordering can decide whether the flow is within the calibration angle range or not, it is useful in wide angle nonnulling methods, too.

• 동력기계공학회지
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• 제18권1호
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• pp.22-31
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• 2014

This paper introduced the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new velocity data reduction method using both a commercial two-dimensional curve-fitting program and the zone partition method of a calibration map was firstly introduced in this study. This new calibration method can be applied up to the wide flow angle of ${\pm}80^{\circ}$ despite of using a five-hole pressure probe because this data reduction method showed a comparatively good performance in calculating yaw and pitch angles from the calibration map.

• 동력기계공학회지
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• 제12권4호
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• pp.18-25
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• 2008

This paper investigated the new calibration algorithm of a straight-type five-hole pressure probe necessary for calculating three-dimensional flow velocity components. The new data reduction method Includes a look-up, a geometry transformation such as the translation and reflection of nodes, and a binary search algorithm. This new calibration map was applied up to the application angle, ${\pm}55^{\circ}$ of a probe. As a result, this data reduction method showed a perfect performance without any kind of interpolation errors In calculating yaw and pitch angle from the calibration map.

• 대한기계학회논문집B
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• 제32권11호
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• pp.863-869
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• 2008

This paper investigated the new calibration algorithm of a straight-type five-hole pressure probe for measuring three-dimensional flow velocity components. This new calibration algorithm was used for velocity data reduction from the calibration map and based on the combination of a look-up, a binary search algorithm and a geometry transformation including the translation and reflection of nodes in a calibration map. The calibration map was expanded up to the application angle, ${\pm}55^{\circ}$ of a probe. This velocity data reduction method showed a perfect performance without any kind of interpolating errors in calculating yaw and pitch angles from the calibration map. Moreover, when it was applied to an actual flow field including a swirling flow, a good result came out on the whole.

• 동력기계공학회지
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• 제10권4호
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• pp.56-64
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• 2006

This paper shows the development process of a straight-type five-hole pressure probe for measuring three-dimensional flow velocity components. The data reduction method using a bi-cubic curve-fitting program in a new calibration map was introduced in this study. This new calibration map can be applied up to the application angle, ${\pm}55^{\circ}$ of a probe. As a result, for the application angle of ${\pm}45^{\circ}$, an error for yaw and pitch angles appeared from $-1.76^{\circ}\;to\;1.83^{\circ}$ and from $-1.91^{\circ}\;to\;1.75^{\circ}$, respectively. Moreover, an error for a vector magnitude and a static pressure compared with a dynamic one showed from -7.83% to 4.87% and from -0.73 to 0.77, respectively. Even though this data reduction method showed unsatisfactory errors in a vector magnitude, it resulted in an easy and simple application method. Especially, when it was applied to an actual flow field including a swirling flow, a good result came out on the whole. However, in order to obtain a better result, it is thought that a more sophisticated interpolation method needs to be introduced.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.165-171
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• 2009

We developed a 'multi-point vibration acceleration method' for accurately predicting the cavitation intensity in pumps. Pressure wave generated by cavitation bubble collapse propagates and causes pump vibration. We measured vibration accelerations at several points on a casing, suction and discharge pipes of centrifugal and mixed-flow pumps. The measured vibration accelerations scattered because the pressure wave damped differently between the bubble collapse location and each sensor. In a conventional method, experimental constants are proposed without evaluating pressure propagation paths, then, the scattered vibration accelerations cause the inaccurate cavitation intensity. In our method, we formulated damping rate, transmittance of the pressure wave, and energy conversion from the pressure wave to the vibration along assumed pressure propagation paths. In the formulation, we theoretically defined a 'pressure propagation coefficient,' which is a correlation coefficient between the vibration acceleration and the bubble collapse pressure. With the pressure propagation coefficient, we can predict the cavitation intensity without experimental constants as proposed in a conventional method. The prediction accuracy of cavitation intensity is improved based on a statistical analysis of the multi-point vibration accelerations. The predicted cavitation intensity was verified with the plastic deformation rate of an aluminum sheet in the cavitation erosion area of the impeller blade. The cavitation intensities were proportional to the measured plastic deformation rates for three kinds of pumps. This suggests that our method is effective for estimating the cavitation intensity in pumps. We can make a cavitation intensity map by conducting this method and varying the flow rate and the net positive suction head (NPSH). The map is useful for avoiding the operating conditions having high risk of cavitation erosion.

• 대한기계학회논문집B
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• 제21권11호
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• pp.1437-1448
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• 1997

Pressures of a five-hole probe were measured for a full range of yaw and pitch angles and complete pressure coefficient maps were obtained. Based on these maps, various features of five-hole probe pressures were revealed and new five-hole probe calibration coefficients were devised. The new calibration coefficients show non-diverging characteristics for any flow direction and one-to-one correspondence for a wide range of flow angles. These calibration coefficients expand the valid flow angle range of five-hole probe calibration by .+-.10 degrees and complement a critical defect of five-hole probe zone-division calibration method which has not been known yet. Moreover new non-diverging calibration coefficients have advantages in nulling methods, too.

• 한국환경복원기술학회지
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• 제25권2호
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• pp.85-92
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• 2022

The amphibian breeding habitat is confirmed by mating call. In some cases, the researcher directly identifies the amphibian individual, but in order to designate the habitat, it is necessary to map the mating call region of the amphibian population. Until now, it has been a popular methodology for researchers to hear mating calls and outline their breeding habitats. To improve this subjective methodology, we developed a technique for mapping mating call regions using Unmanned Aerial Vehicle (UAV). The technology uses a UAV, fitted with a sound recorder to record ground mating calls as it flies over an amphibian habitat. The core technology is to synchronize the recorded sound pressure with the flight log of the UAV and predict the sound pressure in a two-dimensional plane with probability density. For a demonstration study of this technology, artificial mating call was generated by a potable speaker on the ground and recorded by a UAV. Then, the recorded sound data was processed with an algorithm developed by us to map mating calls. As a result of the study, the correlation coefficient between the artificial mating call on the ground and the mating call map measured by the UAV was R=0.77. This correlation coefficient proves that our UAV recording system is sufficiently capable of detecting amphibian mating call regions.

• 대한기계학회논문집
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• 제12권4호
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• pp.833-846
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• 1988

본 연구에서는 후래시현상과 가열이 동시에 존재하면서 증발을 일으키는 수직 증발관내에서의 유동양식에 대해서, 우선 전기 프로우브를 이용하여 관내의 유동양식 에 따른 전기적 신호를 얻고, 시진실험 방법(photographic experimental method)을 통 하여 이를 확인한다. 또한, 전기 프로우브를 통하여 얻은 신호는 적절한 해석과정을 통해 수직 증발관내의 유동에 따른 기공률을 측정하는데 적용된다.

• Spatial Information Research
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• 제23권3호
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• pp.79-89
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• 2015

건축물이 일정규모 이상 높아지면 구조설계 시 바람의 영향이 중요한 요인으로 작용하게 된다. 우리나라는 지형적인 특성상 태풍과 같은 위험현상이 자주 발생하는 지역이므로 더욱 중요한 요인이라 할 수 있다. 이러한 시대적 흐름과 기상변화를 고려한다면 건축물의 합리적인 내풍설계의 필요성이 더욱 부각되고 있다. 본 연구에서는 1:5,000 수치지형도를 바탕으로 공간정보분석을 이용하여 설계풍하중 산정방법을 제시하였으며 실제 적용사례와 비교분석 하였다. 제안된 방법으로 풍속고도분포계수, 지형계수를 산정할 경우 보다 정량적, 객관적으로 설계풍속을 산정할 수 있었으며 기존의 방법과 비교했을 때 평가에 필요한 시간과 비용을 단축할 수 있을 것으로 기대되 건축물의 합리적이고 경제적인 내풍설계에 도움이 될 것으로 기대된다.