• 한국전산유체공학회지
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• 제21권3호
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• pp.77-88
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• 2016

A parametric study on a fluidic oscillator was performed numerically in this work. Three-dimensional unsteady Reynolds-averaged Navier-Stokes equations were solved to analyze the flow in the fluidic oscillator. As turbulence closure, $k-{\varepsilon}$ model was employed. Validation of the numerical results was performed by comparing numerical results with experimental data for frequency of the oscillation. The parametric study was performed using five geometric parameters. Performance of the fluidic oscillator was evaluated in terms of velocity ratio and pressure drop. The results show that the inlet channel width and the distance between splitters are important factors in determining the performance of the fludic oscillator.

• 대한기계학회논문집A
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• 제28권1호
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• pp.22-30
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• 2004

A micro-fluidic oscillator is used to control a linear actuator in a dynamic microsystem. The pressure difference at its two output ports causes the linear actuator to move, and it is a standard of judging the performance of the oscillator. The performance can be improved by optimizing the geometry of the oscillator, which has to enable fluid jet to switch at low inlet velocity. For this, in this study the relationship between the pressure coefficient (difference) and geometric parameters is obtained through the analysis using the software FLUENT. From the results the optimized model that maximize the output pressure difference is obtained by using a cyclic coordinate method that is one of optimization methods. As a result not only the performance is improved, but also the working range is more widen.

• 한국항공우주학회지
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• 제50권11호
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• pp.747-754
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• 2022

유체진동기에서 분출되는 초음속 진동제트를 이용하여 충격파에 의한 경계층 박리유동을 제어하는 실험적 연구가 이루어졌다. 유체진동기의 위치와 제어압력의 변화가 경사충격파에 의하여 발생되는 경계층 박리유동의 특성에 미치는 영향이 관찰되었고, 이를 위하여 고속 슐리렌, 표면유동가시화, 벽압력 측정, 그리고 정밀 피토관 측정 기법이 적용되었다. 본 연구의 초음속 진동제트의 박리유동 제어 특성은 공기제트 와류를 이용한 기존 제어기법과 정량적으로 비교 분석되었다.

• 한국가시화정보학회지
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• 제18권1호
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• pp.50-58
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• 2020

This paper presents flow characteristics of a sweeping jet issued by a feedback-free fluidic oscillator. Overall flow characteristics of feedback-free sweeping jet (FFSJ) were analyzed using flow visualization. The feedback-free sweeping jet has a sinusoidal external flow pattern. The oscillating frequency of the FFSJ is three times higher than that of a conventional sweeping jet at the same Reynolds number. Flow structure and turbulence characteristics were investigated using time-resolved particle image velocimetry (TR-PIV). In instantaneous velocity fields, the flow did not stay at ends but changed the direction continuously in contrast to the conventional sweeping jet. Velocity distributions at each plane which were extracted from mean velocity field has Gaussian distribution, which is similar with a circular jet. The sweep angles were constant as 45° at all Reynolds numbers in the high flow rate regime.

• 한국항공우주학회지
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• 제48권3호
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• pp.167-174
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• 2020

내부에 공유피드백 유로를 갖는 공유형 초음속 유체진동기에서 나타나는 유동특성에 관한 연구가 수행되었다. 비정상 전산유체역학적 해석이 수행되었고 수치해석 결과는 동일한 운용조건에서 수행된 실험결과와 비교 검증되었다. 수치해석 결과, 공유피드백 유로가 해당 유체진동기의 진동 메커니즘에 큰 영향을 주어 진동기 출구 각 제트유동의 동조화에 큰 역할을 하고 있음이 확인되었다. 공유형 유체진동기는 동일 형상의 단일형 유체진동기와 비교하여 진동수가 증가하나 압력손실 또한 커짐이 확인되었다.

• 한국가시화정보학회지
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• 제16권3호
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• pp.16-25
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• 2018

PIV experiments were carried out to visualize the velocity distribution of the sweeping jet impinging onto a flat plate and kinematic behavior of the jet from the fluidic oscillator. Two parameters such as four different Re cases and four different jet-to-wall distances were examined. Time-resolved two dimensional PIV measurements were performed for both streamwise and normal planes respect to the jet axis. Ensemble averaged and phase averaged velocity fields were obtained for the tested range of parameters. The sweeping frequency of the jet increases linearly with increase of Re. The kinetic energy of the sweeping jet decreases as the distance from the jet to the impinging plate increases. In addition, turbulence flow is generated due to the swinging motion of sweeping jet, and various vortices such as primary and secondary vortex are observed near the impinging wall.

• 한국가시화정보학회지
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• 제17권2호
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• pp.58-66
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• 2019

This study investigated heat transfer and flow characteristics of a sweeping jet issued from a rectangular nozzle with a thin plate. A thin vertical aluminum plate was attached on outlet of fluidic oscillator to increase velocity of central area with Coanda effect and enhance heat transfer performance. From visualization and PIV experiments, sweeping jet with a thin plate has larger velocity distribution in center region than that of the normal sweeping jet while oscillating frequency is similar as the normal one. Thermographic phosphor thermometry method was used to visualize the temperature field and Nu distribution of plate with impinging sweeping jet with thin plate. Four Reynolds numbers and three jet-to-wall distances were selected as parameters. It is found that heat transfer performance in the low jet-to-wall spacing was enhanced as the cooled area was expanded. However, when the jet-to-wall spacing became greater than 8dh, heat transfer performance became similar due to reduced impinging velocity.