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RISS 인기검색어
- 검색키워드
- 저자 : Noor Fatima (검색결과 3 건)
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Decoupling of hyperbolic conservation laws using an improved eigenvector matrix
Noor Fatima Siddiqui,Mukkarum Hussain 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3
The resolution of Harten’s non-oscillatory explicit second-order accurate total variation diminishing scheme was relatively high for computations of nonlinear wave equations. However, this scheme shows false dissipation for sharp discontinuities, such as shocks and contacts, when applied to 1D Euler equation. The selection of the entropy fixing parameter, flux limiter, and appropriate eigenvector matrix is crucial to control the amount of such dissipation. This study focuses on the formulation of eigenvector matrix, which is used for the decoupling of a highly coupled nonlinear 1D Euler equation into a nonlinear wave equation. The selection of the eigenvector matrix is crucial to limit the unwanted false dissipation, which is inherent to the numerical schemes derived for nonlinear wave equations. A generalized form of the scaling factor for the eigenvector matrix is then derived, which is satisfied by the scaling factors used by Harten, Hofmann, and Yee. LAX, SOD, and inverse shock test cases of the shock tube problem are solved to examine and analyze the corresponding physical aspects. The findings show that multiplying the scaling factor by itself or by a constant does not affect the results. However, the variables inside the scaling factor, as well as these variables’ powers play a vital role in controlling false dissipation. These scaling factors can effectively capture physics in one case, but might not exhibit satisfactory performance for other problems. In addition, Yee’s scaling factor can effectively capture shock and contact discontinuities, especially for the inverse shock test case.
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Appraisal of geopolymer lightweight aggregates sintered by microwave radiations
Nimra Saleem,Khuram Rashid,Noor Fatima,Sadia Hanif,Ghinwa Naeem,Aamna Aslam,Miral Fatima,Kiran Aslam 아시아콘크리트학회 2020 Journal of Asian Concrete Federation Vol.6 No.2
This work was designed for the production of geopolymer based lightweight aggregate (LWA) using industrial by-products. Combination of fly ash (FA) and silica fume (SF) were used as precursors, whereas, combination of sodium hydroxide and sodium silicate were used as activator. Small amount of sodium bicarbonate was also used for surface hardening and early strength development. Pellets of dif-ferent sizes were crafted manually and cured by microwave radiations just for 5 minutes. The physico-mechanical properties of produced pellets (LWA) were discussed in light of: morphology, density, water absorption, specific gravity, porosity, aggregate impact value, and particle crushing strength. The prop-erties of LWA were also compared with literature reported synthetic LWAs cured with different tech-niques. The water absorption and specific gravity of LWAs were within the specified range provided by ACI standard. Mechanical strength properties briefed that the produced LWAs were strong enough to resist compressive load comparable to natural LWAs and many other synthetic LWAs. Thus, proposed curing method, microwave irradiation, has been found to be a sustainable and fast curing technique than conventional energy-intensive curing regimes. The results also confirmed that produced LWAs have po-tential to replace natural LWAs both in cast-in-place and precast concrete elements with possible eco-nomic, environmental, and technical benefits.
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