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An Experimental Study of CO2 Thermochemical Nonequilibrium

AIAA JOURNAL 2022年第3期60卷 1283-1292页

作者： Gu, Sangdi Morgan, Richard G. McIntyre, Timothy J. Brandis, Aaron M. Univ Queensland Ctr Hyperson Sch Mech & Min Engn Brisbane Qld 4072 Australia Univ Queensland Ctr Hyperson Sch Math & Phys Brisbane Qld 4072 Australia NASA Ames AMA Aerothermodynam Branch Mountain View CA 94035 USA Hong Kong Polytech Univ Dept Aeronaut & Aviat Engn Kowloon Hong Kong Peoples R China

An experimental study of CO2 flows subjected to expanding conditions relevant to Mars entry is presented. A condition with a nominal velocity of 4.0 km/s was generated in the X2 expansion tunnel. Midwavelength infrared emission measurements of the 4.3 and 2.7 mu m bands were made over both a two-dimensional wedge model and for the freestream. Consistent results in the characterization of the freestream were obtained from pressure and spectroscopic measurements. The rotational and vibrational temperatures estimated in the wedge flow using the 2.7 mu m band were consistent with those estimated from the 4.3 mu m band. The difference between the CO2 translational-rotational temperature and the CO2 vibrational temperature was shown to be small in the freestream and expanding flow over the wedge model: less than 10%. Using vibrational relaxation rates tuned for postshock conditions, computational fluid dynamics simulations significantly overestimated the thermal nonequilibrium in the expanding flow, but not in the postshock (compressive) flow. This observation is consistent with past results for N-2 and CO, as well as CO2 at lower temperatures.

关键词： Freestream Conditions Nonequilibrium Flows Thermal Nonequilibrium computational fluid dynamics simulation Emission Spectrum Spectroscopy Energy Distribution Static Pressure Pressure Transducers Pitot Probes

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Machining performance evaluation under recently developed sustainable HAJM process of zirconia ceramic using hot SiC abrasives: An experimental and simulation approach

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART C-JOURNAL OF MECHANICAL ENGINEERING SCIENCE 2022年第2期236卷 1009-1035页

作者： Pradhan, Subhadip Das, Sudhansu Ranjan Jena, Pankaj Charan Dhupal, Debabrata Veer Surendra Sai Univ Technol Dept Prod Engn Sambalpur 768018 Odisha India

The proposed research work accomplishes the experimental study and computational fluid dynamics (CFD) technique for erosive footprint prediction extent in hot abrasive jet machining (HAJMing) constraints on target surface erosion rate, surface roughness of intricately shaped tapered holes generation. The CFD-obtained footprints were in superior agreement with experimentally measured data. HAJMing process uses a relatively high speed air-hot abrasive stream to produce both high accuracy micro-channels and tapered holes. HAJM also defines itself phenomenal competence over all advanced manufacturing techniques due to its growing demands for better surface reliability with defects (mostly stress, heat) free surfaces. Zirconia is widely accepted and associated in the non-conventional machining processes and industries with the years of track on record of proven performance in a vast number of brittle materials. Most perceptible act in this research is the selection of abrasive particle to achieve the appropriate intricate shaped holes on zirconia ceramic with hot silicon carbide (SiC) abrasives. Machining of these features are done with varying the abrasive temperature. Optical microscopic view was considered for the generation of machined holes during HAJMing. All the experimental data were presented to study the effect of machining constraints on target surface erosion rate and surface roughness using HAJMing. Single impact experiments were executed to measure the target surface erosion due to impact of individual hot silicon carbide abrasive particles. An experimental setup has been designed to conduct the machining trials using Box-Behnken design of experiments. It is also shown that the generated workpiece surface contour and erosion rate are the function of machining constraints which have a negligible influence on air-abrasive flow characteristics. This research work also deals with the sustainability assessment under environmental-friendly hot abrasive-assisted m

关键词： Hot abrasive jet machine zirconia ceramic silicon carbide computational fluid dynamics simulation scanning electron microscopic study sustainability assessment

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System Identification of Two-Dimensional Transonic Buffet

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AIAA JOURNAL 2022年第5期60卷 3090-3106页

作者： Sansica, Andrea Loiseau, Jean-Christophe Kanamori, Masashi Hashimoto, Atsushi Robinet, Jean-Christophe Japan Aerosp Explorat Agcy JAXA Numer Simulat Res Unit Aeronaut Technol Directorate 7-44-1 Jindaiji Higashi Machi Chofu Tokyo 1828522 Japan HESAM Univ Arts & Metiers Inst Technol CNAM DynFluid Lab F-75013 Paris France

When modeled within the unsteady Reynolds-averaged Navier-Stokes framework, the shock wave dynamics on a two-dimensional airfoil at transonic buffet conditions is characterized by time-periodic oscillations. Given the time series of the lift coefficient at different angles of attack for the OAT15A supercritical profile, the Sparse Identification of Nonlinear dynamics (SINDy) technique is used to extract a parameterized, interpretable, and minimal-order description of this dynamics. For all the operating conditions considered, SINDy infers that the dynamics in the lift-coefficient time series can be modeled by a simple parameterized Stuart-Landau oscillator, reducing the computation time from hundreds of core hours to seconds. The identified models are then supplemented with equally parameterized low-dimensional dynamic mode decomposition based state observers enabling real-time estimation of the whole flowfield from the predicted lift. The value of this simple model is in the possibility of enriching sparse data sets in the buffet regime for new geometries. Only a few unsteady simulations need to be performed to adjust the coefficients of the identified model and then supplement the data set with new cases. Simplicity, accuracy, and interpretability make the identified model an attractive tool toward the construction of real-time systems to be used during the design, certification, and operational phases of the aircraft life cycle.

关键词： Linear Time Invariant Lift Coefficient Reynolds Averaged Navier Stokes Shock Waves Nonlinear dynamics Two Dimensional Airfoil Real Time System Kalman Filter computational fluid dynamics simulation Flow Conditions

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Development and verification of a reduced dimethoxymethane/n-heptane/toluene kinetic mechanism and modelling for CI engines

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APPLIED THERMAL ENGINEERING 2022年 214卷

作者： Shi, Xiuyong Qian, Weiwei Wang, Haoyu Pan, Mingzhang Wang, Qiwei Ni, Jimin Tongji Univ Sch Automot Studies Shanghai 201804 Peoples R China Guangxi Univ Coll Mech Engn Nanning 530004 Peoples R China

Dimethoxymethane (CH3OCH2OCH3, DMM) has been regarded as a potential alternative fuel for CI engines due to its advantage of high oxygen contents and renewability. However, little investigation has been conducted for computational fluid dynamics (CFD) simulation because of the lack of appropriate reduced mechanisms of DMM. In this study, a reduced DMM/n-heptane/toluene kinetic mechanism is developed, which contains 173 species and 698 reactions based on the decoupling methodology. In addition, the new reduced mechanism has been validated via comparison to experiments of ignition delay times, laminar flame speeds, and species concentrations. It is found that the prediction of reduced kinetic mechanism proposed by this study can well capture the combustion characteristics of dimethoxymethane, n-heptane, and toluene. Meanwhile, it is worth noting that the maximum flame speeds of DMM appears at a slightly richer mixture (higher equivalence ratio) in comparison with n-heptane. The DMM maximum laminar flame speeds of 45 cm/s, 55 cm/s, and 64 cm/s are observed at temperatures of 298 K, 328 K, and 358 K, respectively. Eventually, the proposed model has been coupled with CFD software to simulate the combustion process of CI engines, the results indicate that both the simulated pressure and heat release rate have a good agreement with the experiments. Moreover, the addition of DMM leads to an increase in NO product, while a reduction in soot distribution.

关键词： Dimethoxymethane Reduced kinetic modeling Ignition delay times Laminar flame speed computational fluid dynamics simulation

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The face behind the Covid-19 mask - A comprehensive review

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ENVIRONMENTAL TECHNOLOGY & INNOVATION 2022年 28卷 102837页

作者： Ganesapillai, Mahesh Mondal, Bidisha Sarkar, Ishita Sinha, Aritro Ray, Saikat Sinha Kwon, Young-Nam Nakamura, Kazuho Govardhan, K. Vellore Inst Technol Sch Chem Engn Mass Transfer Grp Vellore Tamil Nadu India Ulsan Natl Inst Sci & Technol Dept Urban & Environm Engn Ulsan South Korea Yokohama Natl Univ Fac Engn Div Mat Sci & Chem Engn Yokohama Kanagawa 2408501 Japan Vellore Inst Technol Sch Elect Engn Dept Micro & Nanoelect Vellore Tamil Nadu India Vellore Inst Technol Sch Chem Engn Vellore 632014 Tamil Nadu India

The threat of epidemic outbreaks like SARS-CoV-2 is growing owing to the exponen-tial growth of the global population and the continual increase in human mobility. Personal protection against viral infections was enforced using ambient air filters, face masks, and other respiratory protective equipment. Available facemasks feature considerable variation in efficacy, materials usage and characteristic properties. Despite their widespread use and importance, face masks pose major potential threats due to the uncontrolled manufacture and disposal techniques. Improper solid waste management enables viral propagation and increases the volume of associated biomedical waste at an alarming rate. Polymers used in single-use face masks include a spectrum of chemical constituents: plasticisers and flame retardants leading to health-related issues over time. Despite ample research in this field, the efficacy of personal protective equipment and its impact post-disposal is yet to be explored satisfactorily. The following review assimilates information on the different forms of personal protective equipment currently in use. Proper waste management techniques pertaining to such special wastes have also been discussed. The study features a holistic overview of innovations made in face masks and their corresponding impact on human health and environment. Strategies with SDG3 and SDG12, outlining safe and proper disposal of solid waste, have also been discussed. Furthermore, employing the CFD paradigm, a 3D model of a face mask was created based on fluid flow during breathing techniques. Lastly, the review concludes with possible future advancements and promising research avenues in personal protective equipment.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://***/licenses/by/4.0/).

关键词： Biodegradability computational fluid dynamics simulation Health impacts Psychological aspects Solid waste management Engineered nanomaterials

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Frossling Number Assessment for Airfoil Under Fully Turbulent Flow Conditions

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2022年第2期36卷 389-398页

作者： Samad, Abdallah Tagawa, Gitsuzo B. S. Khamesi, Rasoul Rajabi Morency, Francois Volat, Christophe Univ Quebec Chicoutimi Antiicing Mat Int Lab Dept Appl Sci 555 Univ Blvd Chicoutimi PQ G7H 2B1 Canada Ecole Technol Super Thermofluids Transport Lab Mech Engn Dept 1100 Notre Dame St West Montreal PQ H3C 1K3 Canada Univ Quebec Chicoutimi Antiicing Mat Int Lab Dept Appl Sci 555 Univ Blvd Chicoutimi PQ G7H 2B1 Canada

North American winters are notorious for aircraft icing, which is a direct threat to aviation safety. Existing high-fidelity codes successfully model icing/de-icing simulations and calculate convective heat transfer, with a penalty of a high computational cost. For a conceptual design of an ice protection system, however, correlations offer a quick approach to determine the average heat transfer rate on an airfoil. The objective of this paper is to introduce a novel correlation for the Frossling number on a NACA 0012, under fully turbulent flow conditions. The correlation is the result of curve fitting a heat transfer database, created using computational fluid dynamics simulations and valid for a wide range of Reynolds numbers and angles of attack. Moreover, the effects of using two different turbulence models as well as two different thermal boundary conditions are investigated. A flat plate test case is used to verify the heat transfer prediction, and airfoil simulations are validated with experimental measurements at the stagnation point. The final form of the correlation shows that a cubic variation of a fits the computational fluid dynamics data best, with an average error of 2.14%.

关键词： Transitional Flow NACA 0012 computational fluid dynamics simulation Calculated Heat Transfer Coefficients Stagnation Point Turbulence Models Lift Coefficient Ice Protection System Reynolds Numbers De Icing

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Effect of the air supply angle of swirling diffusers on the air diffusion performance index in a vehicle assembly workshop

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INDOOR AND BUILT ENVIRONMENT 2022年第7期31卷 1918-1931页

作者： Li, Can Zi, Huali Wei, Xiaoqing Xiong, Jiayuan Hunan Univ Technol Coll Civil Engn Taishan West Rd 88 Zhuzhou 412007 Peoples R China

Airflow improvement in a large industrial building is one of the most effective ways to improve the thermal comfort of workers. Air Diffusion Performance Indices (ADPI) of an industrial workshop area under different air supply angles (15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees and 90 degrees in summer and 90 degrees in winter) of the ceiling-mounted swirling diffusers were evaluated by on-site measurements and computational fluid dynamics (CFD) modelling. The measurement data was used to verify the CFD numerical model. The temperature and velocity field of the working area were simulated and analysed under seven operating conditions of swirling diffusers. The findings showed that in summer, the increase of the swirling air supply angle would increase the air velocity. When the air supply angle was larger than 75 degrees, a draughty wind speed (>0.3 m/s) in the local working area, was produced. When the air supply angle was 30 degrees-75 degrees, the indoor design comfortable temperature range (26 degrees C-28 degrees C) was produced. The ADPIs of the workshop were 100% with the air supply angles of 45 degrees and 60 degrees in summer and 90 degrees in winter, respectively. The research findings should provide a reference for improving the airflow organization in the working area of a tall factory building.

关键词： Swirling air diffuser large industrial building computational fluid dynamics simulation air diffusion performance index air supply angles

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Numerical evaluation of contaminants mixing uniformity in a full-scale test chamber with mixing fan

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INDOOR AND BUILT ENVIRONMENT 2022年第1期31卷 155-169页

作者： Xu, Hai-Xia Mu, Yu-Tong Zhang, Yin-Ping Tao, Wen-Quan Shanghai Res Inst Bldg Sci Grp Co Ltd Shanghai Peoples R China Xi An Jiao Tong Univ Sch Human Settlements & Civil Engn Xian Shaanxi Peoples R China Tsinghua Univ Dept Bldg Sci Beijing Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn China Key Lab Thermofluid Sci & Engn MOE 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China

Most existing models and standards for volatile organic compounds emission assume that contaminants are uniform in the testing devices. In this study, a three-dimensional transient numerical model was proposed to simulate the mass transport process based on a full-scale test chamber with a mixing fan, and the airflow field and contaminants concentration distribution were obtained within the chamber under airtight and ventilated conditions. The model was validated by comparing the numerical results with experimental data. The numerical results show that the contaminant source position and the airflow field characteristics have significant impact on the contaminant mixing, and the fan rotation has an important role in accelerating mixing. In the initial mixing stage, the concentration distribution is obviously uneven;as the mixing progresses, it gradually reaches acceptable uniformity except for some sensitive regions, such as high concentration region at the injection point of the contaminants and low concentration region at the air inlet. To ensure test accuracy, the monitor should avoid above sensitive regions;and some special regions are recommended where contaminant concentration uniformity can be reached sooner. The ventilated chamber results indicate that the mixture of contaminants in the chamber is actually better than the results shown by conventional test method.

关键词： Full-scale test chamber Volatile organic compounds computational fluid dynamics simulation Mixing uniformity Moving mesh method

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Towards Mixed-Fidelity Aero-Structural-Acoustic Optimization for Urban Air Mobility Vehicle Design

Towards Mixed-Fidelity Aero-Structural-Acoustic Optimization...

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AIAA Aviation Forum

作者： Pacini, Bernardo Prajapati, Malhar Duraisamy, Karthik Martins, Joaquim R. R. A. He, Ping Univ Michigan Dept Mech Engn Ann Arbor MI USA Univ Michigan Dept Aerosp Engn Ann Arbor MI USA Univ Michigan Aerosp Engn Ann Arbor MI USA Iowa State Univ Dept Aerosp Engn Ames IA USA

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

Many urban air mobility vehicle designs feature propellers integrated with fuselage, wings, and other appendages. These vehicle designs are based on complex configurations with novel propulsion systems and flight technology. The tightly coupled nature of the systems in these vehicles and the novel technologies within them create opportunities for vehicle analysis and optimization. Furthermore, the geometries being developed are unique, utilizing advanced materials for integral components. Aerodynamic, structural, and acoustic analysis and optimization can provide insight into their performance, and how the propellers, structures, and lifting surfaces can be designed to further improve vehicle efficiency considering operational constraints. This work details an aero-structural-acoustic optimization toolchain built with the MACH and OpenMDAO tools, embedded within the modeling and optimization framework called MPhys. This analysis and optimization framework utilizes multiple model fidelities, including hybrid blade element momentum theory, computational fluid dynamics, finite-element modeling, and an aeroacoustic analogy. With this toolchain, this work presents gradientbased aero-structural-acoustic optimization, minimizing required flight power while ensuring structural integrity and respecting acoustic considerations. The toolchain is applied to the NASA tiltwing concept vehicle to optimize the wing and propeller designs, yielding a 17.8% reduction in required power for cruise flight while considering aerodynamic, structural, and acoustic constraints. This aero-structural-acoustic optimization framework can help make vehicle designs more efficient, lighter, and quieter.

关键词： Urban Air Mobility Propeller Performance computational fluid dynamics simulation Finite Element Analysis Tractor Configuration Blade Element Momentum Theory Flight Technology Ffowcs Williams Hawkings Equation NASA OpenMDAO

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Anisotropic Mach Cone Aligned Mesh Adaptation for Low Boom simulations

Anisotropic Mach Cone Aligned Mesh Adaptation for Low Boom S...

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AIAA Aviation Forum

作者： Ashby, Chase P. Housman, Jeffrey A. Duensing, Jared NASA Computat Aerosci Branch Ames Res Ctr M-S 258-2 Moffett Field CA 94035 USA

ISBN: (数字)9781624107047

ISBN: (纸本)9781624107047

An automated off-body Mach cone aligned structured curvilinear grid generation procedure is presented for near-field computational fluid dynamics simulations. This procedure combines output-based indicators and mesh redistribution to perform anisotropic mesh adaptation while maintaining Mach cone alignment. Automation is achieved through a novel direction-based adaptation indicator formulation. The adaptation procedure is demonstrated on the JAXA Wing Body geometry and X-59 C608 demonstrator model from the Second and Third AIAA Sonic Boom Prediction Workshops, respectively. It is demonstrated that anisotropic mesh adaptation may result in a greater than fifty percent reduction in the resource usage required to achieve the same level of accuracy as uniform and user constructed Mach cone aligned grids for near-field pressure signatures, ground-level overpressure signatures, and loudness metrics.

关键词： Sonic Booms computational fluid dynamics simulation Compressible Flow Aerodynamics Aspect Ratio Euler Equations Angle of Attack Environmental Control System Nonlinear Systems Richardson Extrapolation

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