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Uncertainty Quantification of Store-Separation Simulation Due to Ejector Modeling using a Monte Carlo Approach with Kriging Model

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Advances in Applied Mathematics and Mechanics 2022年第3期14卷 622-651页

作者： Shuling Tian Rongjie Li Jiawei Fu Zihan Jiao Jiangtao Chen Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjingJiangsu 210016China Shenyang Aircraft Design&Research Institute ShenyangLiaoning 110000China Science and Technology on Space Physics Laboratory China Academy of Launch Vehicle TechnologyBeijing 100076China China Aerodynamics Research and Development Center MianyangSichuan 621000China

Precise calculation of the trajectory of store separation is critical in assess-ing whether the store can be released *** ejection is the initial stage of the releasing process and any uncertainty introduced at this stage will propagate through the whole *** this work,the impact of the uncertainties in ejector modeling on the simulation of a generic store separation is investigated by using a Monte-Carlo-based *** reduce the extremely large computation cost resulted from the direct use CFD in Monte Carlo simulation,the CFD solutions are represented by a time-dependent Kriging model,which is constructed at each time step by using the samples from the URANS *** stochastic outputs,including the distri-bution of probability density function,expected value and 95%conﬁdence interval of store separation trajectory,are obtained by the Monte Carlo *** sensitiv-ity analysis is also carried out by using the Monte-Carlo-based method to determine the most signiﬁcant variables in ejector modeling,which affect the output *** results show that ejector modeling is one of the main uncertainty sources of store separation simulation and the approximation in ejector modeling can cause a signiﬁ-cant deviation,especially in the angular displacement.

关键词： Uncertainty quantification Monte Carlo simulation Kriging surrogate model store separation

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Bionic microchannels for step lifting transpiration

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International Journal of Extreme Manufacturing 2023年第2期5卷 244-252页

作者： Zhaolong Wang Qiu Yin Ziheng Zhan Wenhao Li Mingzhu Xie Huigao Duan Ping Cheng Ce Zhang Yongping Chen Zhichao Dong Interdisciplinary Research Center of Low-carbon Technology and Equipment College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082People’s Republic of China MOE Key Laboratory for Power Machinery and Engineering School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240People’s Republic of China Qian Xuesen Laboratory of Space Technology China Academy of Space Technology(CAST)Beijing 100094People’s Republic of China Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Environmental Science and EngineeringSuzhou University of Science and TechnologySuzhouJiangsu 215009People’s Republic of China Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjing 210096People’s Republic of China Chinese Academy of Sciences Key Laboratory of Bio-inspired Materials and Interface Sciences Technical Institute of Physics and ChemistryChinese Academy of Sciences100190 BeijingPeople’s Republic of China

Those various cross-sectional vessels in trees transfer water to as high as 100 meters,but the traditional fabrication methods limit the manufacturing of those vessels,resulting in the non-availability of those bionic ***,we fabricate those bionic microchannels with various cross-sections by employing projection micro-stereolithography(PμSL)based 3D printing *** circumradius of bionic microchannels(pentagonal,square,triangle,and five-pointed star)can be as small as 100μm with precisely fabricated sharp ***'s more,those bionic microchannels demonstrate marvelous microfluidic performance with strong precursor effects enabled by their sharp *** significantly,those special properties of our bionic microchannels enable them outstanding step lifting performance to transport water to tens of millimeters,though the water can only be transported to at most 20 mm for a single bionic *** mimicked transpiration based on the step lifting of water from bionic microchannels is also *** precisely fabricated,low-cost,various cross-sectional bionic microchannels promise applications as microfluidic chips,long-distance unpowered water transportation,step lifting,mimicked transpiration,and so on.

关键词： bionic microchannel microfluidics water transportation step lifting 3D printing

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Experimental comparison of induction control methods for wind farm power maximization on a scaled two-turbine setup

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Journal of physics: Conference Series 2024年第9期2767卷 092064-092064页

作者： Daan Van Der Hoek Carlos Simão Ferreira Jan-Willem Van Wingerden Delft Center for Systems and Control Faculty of Mechanical Engineering Delft University of Technology Delft The Netherlands Wind Energy Section Department of Flow Physics and Technology Faculty of Aerospace Engineering Delft University of Technology Delft The Netherlands

Induction control methods offer a potential solution to minimizing wake effects that occur in large wind farms. This paper presents an experimental study on multiple induction control methods for wind farm power maximization. Wind tunnel experiments were conducted on two aligned scaled wind turbines. The upstream turbine was operated with static induction control, periodic dynamic induction control with collective pitch actuation, and dynamic individual pitch control (the helix approach). All wind farm control implementations were compared to a baseline case, which optimized the individual power extraction of both turbines. Tomographic particle image velocimetry was used to measure the wake of the upstream turbine. Based on turbine measurements, grid searches were employed to discover the optimal frequency and amplitude of the pitch actuation in the dynamic induction control cases. While static induction control showed increased wake velocities in the near wake, it did not provide an overall increase in power production of the two-turbine array. Dynamic induction control methods, especially the helix approach in the counterclockwise direction, were seen to significantly increase the total power output compared to the baseline control case. However, this improvement came with a larger amount of pitch actuation and increased fatigue loading of structural components in the fore-aft direction.

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The effect of angle of attack on the formation and evolution of the flow associated with a synthetic jet actuator 9th

The effect of angle of attack on the formation and evolution...

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9th AIAA flow control Conference, 2018

作者： Rice, Thomas T. Amitay, Michael Rensselaer Polytechnic Institute Center for Flow Physics and Control TroyNY12180 United States

ISBN: (数字)9781624105548

ISBN: (纸本)9781624105548

Synthetic jet actuators have received significant interest in the field of flow control due to their high control authority, low power requirement, and zero dependence on pneumatic plumbing. Many experiments have characterized the behavior and flow physics associated with a synthetic jet in a laminar boundary layer at zero pressure gradient, but this scenario, although a good reference, is rarely observed in full scale applications. The current study includes an analysis of the flowfield generated by a synthetic jet actuator in a turbulent or transitional boundary layer in three specific scenarios: A favorable pressure gradient, an adverse pressure gradient, and a separated flow where the synthetic jet actuators have the ability to reattach the flow. This is accomplished by placing a synthetic jet (or array of synthetic jets) on an airfoil surface and altering its angle of attack. A volumetric flowfield was reconstructed by using a series of spanwise stereo PIV fields, taken in both the time-and phase-averaged sense. It was found that a favorable pressure gradient reduces the diffusion and decay of coherent vortical structures, allowing for the downstream effect to withstand longer spatially than its adverse pressure gradient counterpart;however, it was also shown that an adverse pressure gradient allowed stronger coherent structures to form near the actuator orifice, implying sensitivity to chordwise placement. At higher angles of attack (α = 21◦), it was shown that the coherent structures associated with the synthetic jet diffuse and dissipate significantly quicker spatially, and much of the energy associated with the actuator maintains attached flow. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Angle of attack

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Computational and experimental investigation of camber morphing airfoils for reverse flow drag reduction on high-speed rotorcraft 74

Computational and experimental investigation of camber morph...

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74th American Helicopter Society International Annual Forum and Technology Display 2018: The Future of Vertical Flight

作者： Jacobellis, George Gandhi, Farhan Rice, Thomas Amitay, Michael Rennselaer Polytechnic Institute United States Center for Flow Physics and Control Rennselaer Polytechnic Institute United States

Through computational fluid dynamics simulations and wind tunnel tests this study examines a NACA63-218 airfoil in reverse flow at Re = 375,000, and demonstrates reduction in reverse flow drag through the introduction of reflex camber when the airfoil is pitched nose up in reverse flow. Of the three dominant sources of reverse flow drag - ram pressure on the upper surface near the trailing-edge, suction on the lower surface near the trailing-edge, and bluff body separation at the rounded nose, reflex camber influences the first two, while leaving the third mostly unaffected. The change in trailing-edge geometry reduces exposure to ram drag on the upper surface while the suction on the lower surface rotates to result in a force opposite to the direction of the free stream. Although the 2D CFD simulations (URANS with SA turbulence model) had difficulty predicting the bluff body separation at the airfoil nose well, the change in flow at the trailing-edge was well captured yielding drag reductions of around 60% for a 10◦ reflex camber (compared to reductions of around 50% in the wind-tunnel test). Even greater percentage reductions in drag (up to 70%) were observed with a larger 15◦ reflex angle for nose-up pitch angles greater than 5◦ in reverse flow. With simulations at a higher Reynolds number (1.5 million) showing very similar drag reductions, using reflex camber over inboard blade sections appears to have signifcant promise for alleviating reverse flow drag on edgewise rotors at high advance ratio.

关键词： Cambers

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A numerical and experimental investigation of flow separation control over a wall-mounted hump model

A numerical and experimental investigation of flow separatio...

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AIAA Aerospace Sciences Meeting, 2018

作者： Koklu, Mehti NASA Langley Research Center Flow Physics and Control Branch MS 170 HamptonVA23681 United States

ISBN: (数字)9781624105241

ISBN: (纸本)9781624105241

Numerical simulations and wind tunnel experiments were performed to investigate flow separation and its control over a wall-mounted hump model. Three-dimensional, unsteady fluid dynamic simulations were used to capture the relevant flow physics of unsteady flow separation and its control via active and passive flow control methods. Surface pressure measurements and surface oilflow visualization were obtained in the experiments. Current measurements documented a considerably thinner incoming boundary layer, but similar pressure distribution, compared to the reference data reported in the CFD Validation (CFDVAL 2004) Experiments. Consistent with the data available in the literature, numerical simulations predicted a longer separation bubble, which manifested itself as a shift in the pressure distributions. Streamwise vortices generated by passive vortex generators increased the suction pressure and provided substantial pressure recovery. Numerical simulations of vortex generators qualitatively predicted the effects of control, and revealed patterns of attached/separated flow regions. On the other hand, active flow control using steady discrete jets reduced, but was not able to eliminate, flow separation for the tested configuration. Although the major disagreement between the numerical and experimental results was in the pressure recovery region due to the inaccurate prediction of the separation bubble, the relative pressure recoveries from the baselines were comparable. Surface oilflow visualization and simulated surface streamlines were qualitatively in good agreement revealing the key flow features. © 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Pressure distribution

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Steady and unsteady excitation of separated flow over the NASA hump model 9th

Steady and unsteady excitation of separated flow over the NA...

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9th AIAA flow control Conference, 2018

作者： Koklu, Mehti NASA Langley Research Center Flow Physics and Control Branch MS 170 HamptonVA23681 United States

ISBN: (数字)9781624105548

ISBN: (纸本)9781624105548

Separated flow and its control over the NASA hump model were investigated at subsonic speeds. Three-dimensional, unsteady fluid dynamic simulations were supplemented by wind tunnel measurements. flow control was implemented by means of spatially distributed discrete jets operating in steady and unsteady modes. The effects of excitation amplitude and frequency were studied numerically and experimentally. Several integral parameters were explored as quality metrics. In addition to the existing ones, two new integral parameters, which are slightly modified versions of the normal force and moment coefficients, were introduced. These two parameters together with pressure drag coefficient were found to be well correlated with the flow control and used in the performance evaluation of different flow control methods including, zero net mass flux actuators, steady suction, sweeping jet actuators, and the currently studied steady and unsteady excitations. For the cases tested, it was found that the unsteady excitation is superior to the steady excitation and slightly better than the sweeping jet actuators whereas the steady suction was found to be the most effective. Although the numerical simulations overpredict the separation bubble, these simulations capture the salient features of flow separation control and hence help us to understand the effect of steady/unsteady excitation on the separated flow. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： flow control

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Transition induced by tandem rectangular roughness elements on a supersonic flat plate 48th

Transition induced by tandem rectangular roughness elements ...

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48th AIAA Fluid Dynamics Conference, 2018

作者： Chou, Amanda King, Rudolph A. Kegerise, Michael A. NASA Langley Research Center Flow Physics & Control Branch M/S 170 HamptonVA23681 United States

ISBN: (数字)9781624105531

ISBN: (纸本)9781624105531

The flow behind two rectangular roughness elements with a height approximately 38– 41% of the boundary layer thickness was examined with a hot-wire probe. The rectangular roughness elements are oriented so that one element was at a +45-degree angle relative to the leading edge of the plate. A second roughness element was placed 7.16 mm downstream of the first one with either the same orientation relative to the leading edge of the plate, or an opposing orientation of −45 degrees from the leading edge. Mean mass-flux and total-temperature profiles of the flow field downstream of the tandem roughness elements were examined for mean-flow distortion. Using streak strength as a measure of mean-flow distortion, the tandem roughness elements had approximately the same amount of distortion, regardless of their relative orientation. Mass-flux fluctuation profiles show that the dominant mode downstream of the tandem roughness elements with the same orientation was similar to that of a single roughness element and centered at a frequency of approximately 55 kHz. The dominant instability downstream of the tandem roughness elements with opposing orientation was centered at a frequency of 65 kHz and grew more slowly than the instabilities behind the single roughness element. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Boundary layers

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The flow physics of synthetic jets interaction with flow over a flapped airfoil 9th

The flow physics of synthetic jets interaction with flow ove...

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9th AIAA flow control Conference, 2018

作者： Lindstrom, Annika M. Monastero, Marianne C. Amitay, Michael Rensselaer Polytechnic Institute Department of Mechanical Aerospace and Nuclear Engineering Center for Flow Physics and Control 110 8th Street TroyNY12180 United States Rensselaer Polytechnic Institute Center for Flow Physics and Control 110 8th Street TroyNY12180 United States

ISBN: (数字)9781624105548

ISBN: (纸本)9781624105548

The interaction of an array of synthetic jet actuators with the flow over an unswept flapped airfoil model was investigated experimentally. Surface pressure measurements were used to determine the global effect of the jets on the flow. When the jets were actuated, the separated flow over the controlled surface became reattached and the sectional lift coefficient was increased by 65%. Stereo particle image velocimetry measurements were obtained in order to explore the three-dimensional flow structures that were formed due to the interaction. The data showed vortical structures emanating from the orifice, which later evolved into double-ring structures, and broke down farther downstream. These vortical structures accelerated the flow around and through them along the surface, re-energizing the boundary layer in the process. These vortical structures are the key component to the jets effectiveness in delaying separation and increasing the lift of the airfoil. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Airfoils

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Production of turbulent kinetic energy in curved shear layers 11

Production of turbulent kinetic energy in curved shear layer...

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11th International Symposium on Turbulence and Shear flow Phenomena, TSFP 2019

作者： Moore, Daniel M. Amitay, Michael Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute 110 8th Street TroyNY12180 United States Center for Flow Physics and Control Department of Mechanical Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute 110 8th Street TroyNY12180 United States

An experimental campaign on a bluff body of rectangular cross section, having a side length ratio of 5:1 was carried out using both particle image velocimetry and hot wire anemometry at a Reynolds number of 3.04×104. Results show that under a slight angle of attack, the development of unsteadiness in the form of turbulent kinetic energy is significantly altered. Furthermore, the change in shear layer trajectory, due to the angle of attack, mainly affects the initial development of the shear layer instability occurring at the leading edge corner. The consequences of these changes are naturally amplified and result in a difference in shear layer thicknesses of approximately a factor 2 on either side of the body. It is postulated that this imbalance of shear flow entering the wake is circularly responsible for differences found at the leading edge, enforcing the notion of a globally unstable flowfield. © 2019 International Symposium on Turbulence and Shear flow Phenomena, TSFP. All rights reserved.

关键词： Angle of attack

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