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1,236 results on '"Li, Huixin"'

8. Measurement error of tracer-based velocimetry in single-phase turbulent flows with inhomogeneous refractive indices

Author

Li, Huixin, Fischer, Andreas, Avila, Marc, and Xu, Duo

Subjects
Physics - Fluid Dynamics
Abstract

Inhomogeneous refractive index fields lead to errors in optical flow velocity measurements. Former respective studies are mostly in quasi two-dimensional flows, and attribute the measurement errors to spatial gradients in the refractive index field, while less attention has been paid to flows with three-dimensional refractive index fields which usually change in space and in time. In this study, ray tracing simulations were carried out in a three-dimensional flow, which is from a direct numerical simulation of single-phase turbulent mixing of two fluids. Given the data of the numerical simulation as reference, the ray tracing simulation is used to quantify the measurement errors of the flow velocity and flow acceleration for tracer-based velocimetry, i.e. particle tracking velocimetry in this study. The errors of both flow velocity and flow acceleration are attributed to the spatial and the spatio-temporal gradients of the refractive indices, respectively, which are closely inherited from flow characteristics. While the dominant type of error depends on the studied flow, the main measurement error for the considered turbulent mixing flow is caused by the random error. When the maximum spatial difference of the refractive indices is about 10 to the power of -6, the relative random measurement error is about 1 % in velocity and about 200 % in acceleration, respectively. When the maximum index difference is about 0.01 (water), the relative random measurement errors of velocity and acceleration are 2000 % and 100,000%, respectively, for the flow considered in this study.

Published
2022
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19. A single-camera synthetic Schlieren method for the measurement of free liquid surfaces

Author

Li, Huixin, Avila, Marc, and Xu, Duo

Subjects
Physics - Fluid Dynamics
Abstract

A single-camera synthetic Schlieren method is introduced to measure the height of a dynamic free liquid surface in a container with a flat bottom. Markers placed on the bottom, seen through the free surface, are virtually displaced due to light refraction at the surface. According to Snell's law, the marker displacements depend on the refractive indices of the transparent liquid and the air, and on the surface height and its spatial gradients. We solve the resulting governing nonlinear equation with the Newton-Raphson method to obtain the surface height. Our method does not require a reference surface height, which allows the measurement of surfaces topography in situations where the liquid depth is unknown. We demonstrate the accuracy of the method by performing experiments of surface ripples and dam-break flows and discuss the measurement uncertainty, errors and limitations.

Published
2021
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29. Economic and environmental analysis of Malaysia's 2025 renewable and sustainable energy targets in the generation mix

Author

Masoud Yahoo, Norlida Hanim Mohd Salleh, Fatemeh Chatri, and Li Huixin

Subjects
Renewable energy, Malaysia, Computable general equilibrium, Electricity mix change, Welfare, Zero emissions, Science (General), Q1-390, Social sciences (General), H1-99
Abstract

In pursuing the goals of sustainable development and transiting from fossil fuel-dependent electricity generation to renewable and sustainable alternatives as endorsed by COP28, Malaysia set a 31 % target for renewable-energy in the power generation mix by 2025. This underlines Malaysia's commitment to combat climate change, mainly by reducing its economy-wide GDP carbon intensity by 45 % from the 2005 levels by 2030. To better understand the effects of renewable energy expansion on the economy, environment, electricity output and input-mix, a computable general equilibrium model is applied using an updated benchmark. The simulation results show that increasing the share of coal and gas in the power generation mix compromises emission reduction targets. Further, there is a trade-off between subsidized natural gas supplies and power generation and exports. The results also show that a larger proportion of renewable energy leads to improved welfare. As the share of gas and coal in renewable energy generation is not very high, its impact on carbon emissions is limited. However, if renewable energy expansion is complemented by subsidy rationalizations, the positive impacts are more pronounced. In terms of policy implications, the findings suggest that Malaysia must step up its emission reduction efforts by augmenting the generation of renewable rather than non-renewable resources. Complementary initiatives such as emission abatement policies and consumption subsidies for refined oil products and fossil-fuel power generation should be rationalized to expand renewable resources, improve energy security, and attain emission reductions.

Published
2024
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