1,721,443 research outputs found
Dataset for: Numerical investigations on the flow over cubes with rounded corners and the noise emitted
No full textThis dataset supports the following publication:
Yanan Wang, Zhiwei Hu, David Thompson. Numerical investigations on the flow over cubes with rounded corners and the emitted noise 2020. Computers and Fluids. DOI: https://doi.org/10.1016/j.compfluid.2020.104521
Abstract: The effect of corner rounding on the flow past a cube is investigated numerically at different Reynolds numbers ranging from 50,000 to 200,000 using delayed detached-eddy simulation in OpenFOAM. Different corner radii from 0 to 40% of the cube length have been considered. To validate the adopted methodology, a benchmark case on the flow over a sphere with the same characteristic length is first performed. Good agreement has been achieved between the results of the benchmark and available experimental and numerical data from literature. Subsequently, features of the flow around cubes with rounded corners are investigated, including the aerodynamic coefficients, mean flow patterns and the surface pressure distribution. The relation between flow features and the aerodynamic coefficients is also analysed. In addition, the far-field noise emitted from the rounded cube is predicted using the Ffowcs William-Hawkings acoustic analogy in FLUENT. It is found that corner rounding with carefully determined radius can be an effective way to reduce the emitted noise. The minimum noise is found for a radius 1/3 of the cube side length with the lowest surface pressure fluctuations, but the sound level increases again for a further increase in corner radius to R/L = 2/5 due to vortex shedding.</span
Aerodynamic flow over cuboids and the noise generated
No full textThis thesis is motivated by the need to reduce train aerodynamic noise, especially the noise from pantographs and bogies which are comprised of bluff bodies including cuboids. The underlying physics of the flow over cuboids with different cross-sections and the emitted noise are studied. The effects of wall proximity and corner radii on the flow field and noise of a cube as well as the effect of the aspect ratio of cuboids are the main focus. The Delayed Detached Eddy Simulation method is adopted to investigate the flow features and obtain the noise source information. The far-field noise is then predicted using the Ffowcs Williams-Hawkings acoustic analogy. Benchmark comparisons on the flow over a wall-mounted cube and a sphere are conducted to validate the feasibility of the adopted methodology for describing the flow field; a separate simulation on a square cylinder is also implemented to gain confidence in predicting surface pressure fluctuations and the far-field noise. Good agreement has been achieved between results from the benchmark cases and those from the literature.It is found that the wall proximity mainly affects the behaviour of the separated flow from the lower leading edge of the cube and also the flow separation along the ground. Large pressure fluctuations are observed close to the trailing edge and locations of the flow reattachment on the bottom of the cube. With the increase of the elevation height, the sound from the cube increases rapidly in the vertical direction and the maximum sound is observed when the cube is elevated by one quarter of the edge length above the ground. For rounded cubes, the flow separation is delayed with the increase of the corner radius; the shear layer moves towards the lateral surfaces and the recirculation length in the wake reduces. Flow features of the rounded cube vary with the Reynolds number, although no systematic dependence is observed. Large pressure fluctuations are found in the recirculating region on the lateral surface and near the trailing edge due to reduced recirculation length in the wake. Rounding the cube with a suitable radius can be an effective way to reduce the emitted noise. The minimum noise is found for a radius one third of the edge length. Cuboids with different aspect ratios are studied, where the aspect ratio is defined as the ratio of the width in the spanwise direction to the length in the streamwise direction. The flow separated from the upper leading edge only reattaches to the top surface for aspect ratios smaller than 1 whereas the vortex shedding in the wake tends to be more evident as the aspect ratio is increased. The Reynolds number has negligible effect on the mean flow behaviours of the cuboid.Large pressure fluctuations happen with the flow reattachment and the formation of the secondary vortex near the trailing edge. The emitted noise from the cuboid is always higher in the cross-flow direction than that in the streamwise and spanwise directions. The maximum sound is found for the aspect ratio of 6
Wang Yanan and the Studies of Classical Political Economy in China
Full text linkThe article focuses on research in the history of dissemination of classical political economy in
China through the activities of Wang Yanan and Guo Dali who translated in the 1930s the works of
Smith, Riсardo, Malthus and Mill into Chinese. The translators’ plans were connected with ideological
tendencies of the epoch and aimed at creation of conditions for the propagation of Marxism while
taking into account the specifics of the perception of Western thought in China. Key attention is given
to Chinese translation of the Wealth of Nations by Adam Smith published in 1931–1932 and its differences
from the first Chinese translation of this book at the beginning of the 20th century by Yan Fu.
The aspiration of translators to subordinate publications to broader programs of popularization in China of different trends of Western social thought was the specific feature of Chinese translations of
the Wealth of Nations. Refs 32
Numerical investigations on the flow over cubes with rounded corners and the noise emitted
No full textThe effect of corner rounding on the flow past a cube is investigated numerically at different Reynolds numbers ranging from 50,000 to 200,000 using delayed detached-eddy simulation in OpenFOAM. Different corner radii from 0 to 40% of the cube length have been considered. To validate the adopted methodology, a benchmark case on the flow over a sphere with the same characteristic length is first performed. Good agreement has been achieved between the results of the benchmark and available experimental and numerical data from literature. Subsequently, features of the flow around cubes with rounded corners are investigated, including the aerodynamic coefficients, mean flow patterns and the surface pressure distribution. The relation between flow features and the aerodynamic coefficients is also analysed. In addition, the far-field noise emitted from the rounded cube is predicted using the Ffowcs William-Hawkings acoustic analogy in FLUENT. It is found that corner rounding with carefully determined radius can be an effective way to reduce the emitted noise. The minimum noise is found for a radius 1/3 of the cube side length with the lowest surface pressure fluctuations, but the sound level increases again for a further increase in corner radius to R/L = 2/5 due to vortex shedding
Dataset for "Numerical investigations on the flow over cuboids with different aspect ratios and the emitted noise"
No full textData supports the paper Yanan Wang, David Thompson1 and Zhiwei Hu Numerical investigations on the flow over cuboids with different aspect ratios and the emitted noise Physics of Fluids DOI: https://doi.org/10.1063/1.5131827</span
Enlightenment of the Chinese Economics Established by Wang Yanan for Rebuilding the Chinese Economics Today
No full text在旧中国，王亚南“站在中国人立场”，以“比较的全面的和发展的研究方法”，“有效的活用”马克思主义为指导，写成了《中国经济原论》及其《续篇》。同时，批判“混合经济制度论”，强调指出多种经济成分并存的社会，必须确定某一经济成分为“代表”和起主导作用，才能保证建设、发展的正确方向。In old China, Wang Yanan, taking the Chinese stand, with a relatively all- round and developing research method and guided by effectively flexible Marxism, wrote his "Primary Discourse on Chinese Economy'"and its " Continuation ". At the same time, he criticized "the Theory of Mixed Economic System" and emphasized that a certain economic element must be established as the representative to play the main role so that the correct building and developing direction can be guaranteed in the multi - economic - element - coexisting society
Variations with Mach number for gust–airfoil interaction noise
No full textThe interaction of turbulence with airfoil is an important noise source in many engineering fields, including helicopters, turbofans, and contra-rotating open rotor engines, where turbulence generated in the wake of upstream blades interacts with the leading edge of downstream blades and produces aerodynamic noise. One approach to study turbulence-airfoil interaction noise is to model the oncoming turbulence as harmonic gusts. A compact noise source produces a dipole-like sound directivity pattern. However, when the acoustic wavelength is much smaller than the airfoil chord length, the airfoil needs to be treated as a non-compact source, and the gust-airfoil interaction becomes more complicated and results in multiple lobes generated in the radiated sound directivity. Capturing the short acoustic wavelength is a challenge for numerical simulations. In this work, simulations are performed for gust-airfoil interaction at different Mach numbers using a high-fidelity direct computational aeroacoustic (CAA) approach based on a spectral/hp element method verified by a CAA benchmark case. It is found that the squared sound pressure varies approximately as the fifth power of Mach number, which changes slightly with the observer location. This scaling law can give a better sound prediction than the flat-plate theory for thicker airfoils. Furthermore, another prediction method, based on the flat-plate theory and CAA simulation, has been proposed to give better predictions than the scaling law for thicker airfoils.</p
Characteristics of the flow around finite wall-mounted square cylinders and the mechanism of tonal noise
No full textMotivated by the need to reduce the noise from train pantographs, numerical simulations are carried out for the flow over finite wall-mounted square cylinders with different aspect ratios at a Reynolds number of 1.5x10^4. Five aspect ratios (height-to-width ratios) are taken into account, namely, 1.4, 4.3, 7.1, 10 and 12.9. The effect of the aspect ratio on the aerodynamic coefficients, the near-wall flow topologies and the pressure distributions are studied in detail to give insight into the noise generation mechanisms. The pressure rate of change dp/dt on the cylinder surfaces is adopted to evaluate the dipole noise source. It turns out that distributions of dp/dt are closely related with flow evolutions near the free ends and the wall-mounting junctions of cylinders with different aspect ratios. High levels of dp/dt are found close to lateral trailing edges of the cylinder, while the strength grows quickly as the aspect ratio is increased. The far-field noise emitted from these cylinders is predicted using the Ffowcs Williams-Hawkings acoustic analogy and validated with wind tunnel measurements available in the literature. For receivers located in the cross-flow direction, a single acoustic tone near a Strouhal number of 0.1 is observed for cylinders with aspect ratios not greater than 7, while an additional tone at a higher Strouhal number occurs as the aspect ratio is further increased. The underlying mechanism of the tonal noise emitted to the far field is also investigated by combining the noise source localization and dynamic mode decompositions
Effect of rounded corners on the flow and noise from a cube
No full textIn this work, the flow characteristics and the emitted noise at different Reynolds numbers for a cube in free space are investigated numerically for a series of rounded corners. In the first step, the Delayed Detached Eddy Simulation (DDES) model is employed in the Computational Fluid Dynamics (CFD) technique to examine the flow features. Subsequently, based on the fluctuating pressure on the solid surfaces obtained from the CFD simulation, the noise in the far field is predicted by using the Ffowcs Williams and Hawkings (FW-H) acoustic analogy. The results show that, as the cube is increasingly rounded, the location of the flow separation moves from the leading edges further downstream. The variations in the flow topology due to the corner radius and the Reynolds number influence the sound radiated to the far field. It turns out that by increasing the radius of the rounded corners, the noise from a cube is reduced, which suggests it is a practical way to reduce the noise from cubes.</p
Numerical investigations on the flow over cuboids with different aspect ratios and the emitted noise
No full textThe effect of aspect ratio on the flow over cuboids in cross-flow is investigated numerically, together with the noise emitted to the far field. The near-field flow features are obtained using the delayed detached eddy simulation approach and the far-field noise is predicted using the Ffowcs Williams–Hawkings acoustic analogy. Ten values of aspect ratio are studied in the current work ranging from 1/6 to 12 at three Reynolds numbers between 50 000 and 200 000. Aerodynamic coefficients, flow patterns, and pressure distributions along the cuboid surfaces are studied in detail with respect to cuboid aspect ratio for different Reynolds numbers. It is found that the separated flow from the leading edge reattaches to the lateral surfaces of cuboids with aspect ratios smaller than unity, while a secondary vortex is formed near the trailing edge for larger aspect ratios. In addition, the aspect ratio has considerable effect on the tonal peak in the far-field noise spectra from the cuboids occurring for aspect ratios greater than 1
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