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AIAA Aerospace sciences Meeting, 2018

作者： Han, Xu Rahman, Mizanur M. Agarwal, Ramesh K. Dept. of Mechanical Engineering & Materials Science Washington University in St. Louis St. LouisMO63130 United States Washington University in St. Louis St. LouisMO63130 United States Dept. of Mechanical Engineering Aalto University Finland

ISBN: (纸本)9781624105241

This paper describes a new wall distance free version of the recently developed one-equation Wray-Agarwal eddy viscosity turbulence model (WA2017). The results from the new model are compared to the experimental data for several standard benchmark test cases. Computational results for a flat plate flow, high Reynolds number channel flow, NASA wall-mounted hump, asymmetric plane diffuser, periodic hill, backward facing step, curved backward facing step, NACA4412 airfoil and axisymmetric transonic bump are presented. It is shown that the wall distance free version of the Wray-Agarwal model has good agreement with the experimental results. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Turbulence models

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Numerical determination of critical mach number of a three-element airfoil in unbounded flow and in ground effect 36th

Numerical determination of critical mach number of a three-e...

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36th AIAA Applied Aerodynamics Conference, 2018

作者： Hu, Bowen Qu, Qiulin Agarwal, Ramesh K. Washington University in St. Louis Dept. of Mechanical Engineering & Materials Science Institute of Fluid Mechanics St. LouisMO63130 United States

ISBN: (数字)9781624105593

ISBN: (纸本)9781624105593

The focus of this paper is on determining the critical Mach number of a three-element airfoil 30P30N in unbounded flow and in ground effect. The commercial CFD software ICEM is employed to generate the mesh. ANSYS Fluent is used to compute the low field. The compressible Reynolds-averaged Navier-Stokes (RANS) equations in conjunction with the Spalart-Allmaras (SA) turbulence model are solved to compute the flow field. The results are discussed in two parts: First the critical Mach number of 30P30N airfoil in unbounded flow is computed and the results for lift and drag coefficients are discussed by bringing the context of critical Mach number of single element airfoil RAE2822. Next the critical Mach number of 30P30N in ground effect for different ground clearances is computed;It is shown that the critical Mach number increases as the ground clearance decreases. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Airfoils

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Structure-Property Relationships of Topological Insulator Nanomaterials

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Microscopy and Microanalysis 2019年第S2期25卷 962-963页

作者： Pengzi Liu Judy J. Cha Dept. of Mechanical Engineering and Materials Science Yale. University New Haven USA Energy Sciences Institute Yale West Campus West Haven USA Canadian Institute for Advanced Research Azrieli Global Scholar Canada

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Numerical investigation of cavitation characteristics of a liquid oxygen turbo pump 48th

Numerical investigation of cavitation characteristics of a l...

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48th AIAA Fluid Dynamics Conference, 2018

作者： Quanzhong, Liu Lujia, Gong Gao, Han Agarwal, Ramesh K. Dept. of Energy Science & Technology Harbin Institute of Technology HarbinHeilongjiang150001 China Dept. of Mechanical Engineering & Materials Science Washington University in St. Louis St. LouisMO63130 United States

ISBN: (数字)9781624105531

ISBN: (纸本)9781624105531

Liquid oxygen turbo pump is a key part of a liquid rocket engine, and is used for supplying liquid oxygen to combustion chamber. Cavitation may seriously compromise the pump from working properly;it can cause hydraulic instability and decline in efficiency. Cavitation flow is a multiphase flow in which propellant gets vaporized and is not able to keep its liquid state in some regions of the flow. Numerical investigation of cavitation flow in turbo pump can help in determining an approach to prevent the turbo pump from cavitation. Numerical simulations for a two-phase flow described by the Zwart-Gerber-Belamri model are performed to investigate the liquid volume fraction and vortex structure in the cavitation flow. Based on the numerical simulations of nascent cavitation flow and developed cavitation flow, detailed patterns of cavitation flow in turbo pump are obtained. Cavitation regions grow in the inducer and impeller and expand to the suction chamber as cavitation develops. Angles of attack on both the inducer blades and impeller blades change with the increase in cavitation, and increase in cavitation leads to separation and swirl in some flow regions around the blades. A vortex analysis method is proposed to determine the characteristics of the cavitation flow. Analysis of vortex volume fraction indicates that the vortex structure due to cavitation is of low-intensity but is very different from that in flow without cavitation. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Oxygen

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Formation of Graphene atop a Si adlayer on the C-face of SiC

arXiv

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arXiv 2019年

作者： Li, Jun Wang, Qingxiao He, Guowei Widom, Michael Nemec, Lydia Blum, Volker Kim, Moon Rinke, Patrick Feenstra, Randall M. Dept. Physics Carnegie Mellon University PittsburghPA15213 United States Dept. Materials Science and Engineering University of Texas at Dallas RichardsonTX75080 United States Fritz-Haber-Institut der Max-Planck-Gesellschaft BerlinD-14195 Germany Dept. Mechanical Engineering and Materials Science Duke University DurhamNC27708 United States Dept. Applied Physics Aalto University P.O. Box 11100 AaltoFI-00076 Finland

The structure of the SiC(000 1) surface, the C-face of the {0001} SiC surfaces, is studied as a function of temperature and of pressure in a gaseous environment of disilane (Si2H6). Various surface reconstructions are observed, both with and without the presence of an overlying graphene layer (which spontaneously forms at sufficiently high temperatures). Based on cross-sectional scanning transmission electron microscopy measurements, the interface structure that forms in the presence of the graphene is found to contain 1.4 – 1.7 monolayers (ML) of Si, a somewhat counter-intuitive result since, when the graphene forms, the system is actually under C-rich conditions. Using ab initio thermodynamics, it is demonstrated that there exists a class of Si-rich surfaces containing about 1.3 ML of Si that are stable on the surface (even under C-rich conditions) at temperatures above ~400 K. The structures that thus form consist of Si adatoms atop a Si adlayer on the C-face of SiC, with or without the presence of overlying graphene. Copyright © 2019, The Authors. All rights reserved.

关键词： Silicon carbide

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Direct observation of alkaline and enzymatic poly(ethylene terephthalate) hydrolysis via neutron reflectivity: Kinetics and mechanistic insights

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Journal of Colloid and Interface science 2025年 698卷 138021页

作者： Machatschek, Rainhard Tarazona, Natalia A. Balk, Maria Göttsch, Frederike Wei, Ren Bornscheuer, Uwe T. Moulin, Jean-François Keller, Manuela Schneider, Nicole Gutfreund, Philipp Müller, Martin Toma, Francesca M. Mangiapia, Gaetano Institute for Active Polymers Helmholtz-Zentrum Hereon Kantstr. 55 Teltow 14513 Germany Institute for Functional Materials for Sustainability Helmholtz-Zentrum Hereon Kantstr. 55 Teltow 14513 Germany Institute of Biochemistry Dept. of Biotechnology & Enzyme Catalysis University of Greifswald Felix-Hausdorff-Straße 8 Greifswald 17489 Germany German Engineering Materials Science Centre (GEMS) am Heinz Maier-Leibnitz Zentrum (MLZ) Helmholtz-Zentrum Hereon Lichtenbergstr. 1 Garching bei München 85748 Germany Institut Laue-Langevin 71 Avenue des Martyrs Grenoble 38042 France Institute of Materials Physics Helmholtz-Zentrum Hereon Max-Planck-Str. 1 Geesthacht 21502 Germany Institut für Experimentelle und Angewandte Physik (IEAP) Christian-Albrechts-Universität zu Kiel Leibnizstr. 19 Kiel 24098 Germany Faculty of Mechanical and Civil Engineering Helmut Schmidt University Hamburg 22043 Germany

One of the challenges in achieving industrial enzymatic depolymerization of poly(ethylene terephthalate) (PET) is the rapid loss of catalytic activity leading to incomplete polymer hydrolysis. While there are several possible explanations for this phenomenon, there is a lack of methods that can measure polymer hydrolysis directly, which makes it challenging to reliably infer mechanistic details. Here, we introduce neutron reflectivity of polymer thin films as a method that allows for direct assessment of the hydrolysis rate of polymers like PET. Through matching and variation of the isotopic contrasts, one can directly observe the reaction kinetics, while simultaneously obtaining structural information on the polymer/enzyme/water system. We show that the Michaelis-Menten theory describes well the enzymatic chain scission kinetics, whereas the alkaline one follows a (pseudo)-first order kinetics. At the concentrations used in the experiments, the areal density of enzymes at the polymer surface is very low, ruling out surface passivation or overcrowding as inhibition mechanisms. © 2025 The Author(s)

关键词： Enzymatic hydrolysis Neutron reflectivity PET

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Uncertainty quantification of geometric and flow variables affecting the performance of a transonic axial compressor

Uncertainty quantification of geometric and flow variables a...

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AIAA Aerospace sciences Meeting, 2018

作者： Li, Zhihui Liu, Yanming Agarwal, Ramesh K. Beijing Institute of Technology School of Aerospace Engineering Beijing100081 United States Dept. of Mechanical Engineering & Materials Science Washington University in St. Louis St. LouisMO63130 United States

ISBN: (数字)9781624105241

ISBN: (纸本)9781624105241

Manufacturing and operational uncertainties always lead to significant variability in compressor performance. In this work, the uncertainties inherent in a transonic axial compressor are quantified to determine their effect on the performance. These uncertainties include the effects of inlet total pressure, inlet turbulence intensity, blade surface roughness, endwall surface roughness, blade thickness and tip clearance size. A validated roughness prediction model and a tip clearance loss model in conjunction with a 3D Reynolds-Averaged Navier-Stokes (RANS) solver are utilized to simulate these uncertainties and quantify their effect on the adiabatic efficiency, surge margin and choked mass flow of the compressor. The sensitivity analysis method is employed to determine which parameters play the most significant roles in influencing the overall performance of the compressor. To propagate these uncertainties, the non-instrusive polynomial chaos expansion (PCE) algorithm is used in this paper. The uncertainties considered are ranked in order of their effect on compressor performance and the probability distributions of compressor performance are predicted according to the built UQ platform. © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Sensitivity analysis

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Surrogate Model Assisted Design of Silicon Anode Considering Lithiation Induced Stresses

Surrogate Model Assisted Design of Silicon Anode Considering...

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Annual International Symposium on Reliability Physics

作者： Zhuoyuan Zheng Bo Chen Yashraj Gurumukhi John Cook Mehmet N. Ates Nenad Miljkovic Paul V. Braun Pingfeng Wang Dept. of Industrial and Enterprise Systems Engineering University of Illinois at Urbana-Champaign Urbana IL USA Dept. of Mechanical Science and Engineering University of Illinois at Urbana-Champaign Urbana IL USA Xerion Advanced Battery Corporation Kettering OH USA Materials Research Laboratory University of Illinois at Urbana-Champaign Urbana IL USA

Silicon-based lithium ion battery anodes are attracting considerable attention due to their high theoretical capacity. However, the significant volume change of silicon during lithiation/de-lithiation cycles restricts its application. A novel bi-continuous Si anode, designed to mitigate the effect of cycling-induced volume changes, is investigated in this study. The effects of the design parameters and the operating conditions of the anode are explored via multi-physics simulation model. It is found that, with the novel anode structure, battery charging C rate has little impact on the mechanical properties. However, the anode structural design parameters would largely influence the stress distribution on the anode. Thus, a Gaussian Processes (GP) based surrogate model is developed to assist the design optimization of the Si anode, while using the simulated results from a multiphysics simulation model as training data. An optimized Si anode design can then be extracted efficiently based upon the developed surrogate model.

关键词： Silicon Anodes Stress Batteries Nickel Solid modeling Strain

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Thermal conductivity of lightweight foamed concrete filled fly ash

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IOP Conference Series: materials science and engineering 2020年第1期725卷

作者： Chundakus Habsya Kuncoro Diharjo Prabang Setyono Prasasto Satwiko Civil Engineering Education Dept. Faculty of Teacher Training and Education Sebelas Maret University Surakarta Indonesia Mechanical Engineering Dept. Engineering Faculty Sebelas Maret University Surakarta Indonesia Environmental Science Dept. Postgraduate Program Sebelas Maret University Surakarta Indonesia Department of Architecture Faculty of Engineering Universitas Atma Jaya Yogyakarta Indonesia

Wall is the wider component of high-rise building to exposed the sunshine than roof. The building wall in tropical countries receives the solar heat all day and it makes temperature rise of its room and becomes less comfortable. Therefore, a wall with good thermal insulation is needed for buildings in tropical countries. Lightweight foamed concrete (LFC) can be used as a wall brick substitution as well as thermal insulator. The experimental research about LFC was investigated using FA and foam content to the thermal conductivity of LFC. The investigations were performed through the measurement of thermal conductivity, material density, and observation to the morphology of LFC surface. The LFC samples were varied in volume fraction of foam and FA in mortar. The result shows that the increase in volume fraction of foam in all variations of FA content decreases its thermal conductivity. In contrast, the increase of FA content in LFC results in an increase in thermal conductivity until 45 wt% of FA content, then it decreases as the addition of FA. Thus, the optimum thermal conductivity of the LFC was obtained by FA of 45 wt%. The relationship between thermal conductivity and LFC density shows that any increase in LFC density resulted in an increase in thermal conductivity. Otherwise, any decrease in LFC density resulted in a decrease in thermal conductivity.

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Processing and mechanical Properties of Dual-Carbide (B 4 C, SiC), Dual-Metallic Phases (Al, Si) Infiltrated Composites

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materials Today: Proceedings 2019年 16卷 374-383页

作者： Arivumani Ravanan Joaquim M. Vieira B.A. Almeida C. Ramkumar Filipe J. Oliveira A.B. Lopes Hongyan Wu Department of Mechanical Engineering KIT – Kalaignar Karunanidhi Institute of Technology Kannampalayam 641 402 Coimbatore India Centre for Research in Ceramics and Composite Materials (CICECO) Campus Universitário de Santiago PT 3810-193 Aveiro Portugal Zhejiang University Dept. of Materials Science and Engg. & State Key Laboratory of Silicon Materials CN-310027 Hangzhou PR China

This work is on processing and studying of toughening property of indentation fracture composites. By applying reactive melt infiltration method infiltrated composites were prepared where different Si-Al compositions and as-pressed porous boron carbide were used at various infiltration temperatures. In which the process became feasible within the experimental constrains of this task. Polished sections of infiltrated composites were examined by quantitative methods with standards for the volumetric fractions of B 4 C, Si, Al, and SiC crystalline phases; and the element distribution in the phases were investigated by SEM/EDS, represented through ternary phase diagram. The distribution of ductile aluminium and brittle phases could determine the means of toughening mechanism and further discussed the de-bonding of interphases.

关键词： Al-Si alloy Boron carbide Composite Hardness Phase diagram Reactive melt infiltration Toughness

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