31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31最新文献

{"title":"Conformational landscape of the SF6 dimer as revealed by various free jet conditions","authors":"M. Gaveau, M. Mons, L. Bruel, A. Potapov, Andrew C. Turner, V. Boudon, P. Asselin","doi":"10.1063/1.5119529","DOIUrl":"https://doi.org/10.1063/1.5119529","url":null,"abstract":"The experiment SPIRALES coupling a tunable infrared laser to a pulsed supersonic free jet has allowed us to reinvestigate the high-resolution absorption spectroscopy of the SF6 dimer in the ν3 mode...","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123098918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hybrid reduced order model for N2-N interactions for application to dissociation and energy transfer processes","authors":"Robyn L. Macdonald, R. Jaffe, M. Panesi","doi":"10.1063/1.5119638","DOIUrl":"https://doi.org/10.1063/1.5119638","url":null,"abstract":"Recent work in the aerothermodynamics community has focused on the development of reduced-order models for thermo-chemical non-equilibrium which avoid the restrictive assumptions of multi-temperature models and the prohibitive cost associated with State-to-State (StS) models. In the present work, this is accomplished by lumping energy states together and assuming groups of states are roughly in equilibrium. As a result, the non-equilibrium behavior of a gas can be captured at a reduced computational cost from a full StS simulation. In this work, we present a hybrid grouping model for studying energy transfer and dissociation in a mixture of nitrogen molecules due to N 2 -N 2 reactions. This is accomplished by making use of a grouping strategy informed by data from the N 2 N StS kinetic data. [1] However, due to the massive computational cost associated with constructing StS data for the N 2 -N 2 system, the kinetic data for the hybrid grouping model are calculated using the quasi-classical trajectory (QCT) method by sampling states for trajectory within the groups. [2,3] This general framework is called the Maximum-Entropy Quasi-Classical Trajectory (ME-QCT) method. The primary challenge associated with this method is that rates for reverse grouped reactions cannot be obtained through detailed balance at a group level, due to the variation of group internal temperatures. To construct the full model for N 2 -N 2 grouped kinetics using the ME-QCT method, detailed balance is invoked at the microscopic level, allowing for the calculation of the full kinetic data from QCT. Results will be presented using the full ME-QCT model for the N 2 -N 2 system in an isothermal and isochoric reactor simulation. In addition, simple CFD test cases for a one-dimensional standing shock and for a quasi-one-dimensional nozzle will be used for demonstration of the ME-QCT method. This method allows for the calculation of","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"154 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126929863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study of mechanical response of CNT-polyethylene nanocomposite using molecular dynamics approach","authors":"K. Sharma, Kishore K. Kammara, Rakesh Kumar","doi":"10.1063/1.5119591","DOIUrl":"https://doi.org/10.1063/1.5119591","url":null,"abstract":"This study aims to gain an understanding of the mechanical response of nanocomposite systems at a molecular level and uses a carbon nanotube (CNT) and polyethylene (PE) nanocomposite as its example. The CNT and PE systems are modeled using molecular dynamics (MD) method and validated for small strain values. Tensile loading behavior of the nanocomposite is documented at various CNT mass fractions. The Young’s moduli of the several CNT mass fraction samples are evaluated at 2% to 4% strain and compared among them. The results from the nanocomposites, as compared to the mixing rule predictions, show a negligible gain in the tensile strength while reducing the ultimate strength of the nanocomposite.This study aims to gain an understanding of the mechanical response of nanocomposite systems at a molecular level and uses a carbon nanotube (CNT) and polyethylene (PE) nanocomposite as its example. The CNT and PE systems are modeled using molecular dynamics (MD) method and validated for small strain values. Tensile loading behavior of the nanocomposite is documented at various CNT mass fractions. The Young’s moduli of the several CNT mass fraction samples are evaluated at 2% to 4% strain and compared among them. The results from the nanocomposites, as compared to the mixing rule predictions, show a negligible gain in the tensile strength while reducing the ultimate strength of the nanocomposite.","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115447672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computations of rarefied hypersonic blunt body flow in binary inert gas mixtures using the generalized Boltzmann equation","authors":"Geng Qian, R. Agarwal","doi":"10.1063/1.5119606","DOIUrl":"https://doi.org/10.1063/1.5119606","url":null,"abstract":"The results of 2-D numerical simulations of hypersonic flow of a single diatomic gas, e.g., Nitrogen and a binary inert mixture of two gases (which are constituents of air namely N2, O2, Ar) past a 2-D blunt body in rotational non-equilibrium from low to high Knudsen Numbers are obtained using the Wang-Chang Uhlenbeck equation [1] or the Generalized Boltzmann Equation (GBE) [2]. The computational framework available for the classical Boltzmann equation for a monoatomic gas with translational degrees of freedom [3] is extended by including the rotational degrees of freedom in the GBE. The general computational methodology for the solution of the GBE for a diatomic gas is similar to that for the classical Boltzmann equation except that the evaluation of the collision integral becomes significantly more complex due to the quantization of rotational energy levels. There are two main difficulties encountered in computation of high Mach number flows of diatomic gases with rotational degrees of freedom using the...","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114516301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DSMC simulation of a radiating hypersonic flow","authors":"Kyle J. Higdon, D. Goldstein, P. Varghese","doi":"10.1063/1.5119568","DOIUrl":"https://doi.org/10.1063/1.5119568","url":null,"abstract":"This research continues development of radiative results with the direct simulation Monte Carlo (DSMC) method for an 11-species air hypersonic flow. A 10.28 km/s, 0.2 Torr hypersonic shock tube experiment in rarefied air is simulated using the Computation of Hypersonic Ionizing Particles in Shocks (CHIPS) DSMC code and CHIPS results are post processed by the NEQAIR line-by-line radiative solver to produce emission spectra. The chosen scenario reproduces the conditions of recent NASA Electric Arc Shock Tube (EAST) experiments which are used as benchmarks for the simulated emission spectra. Several improvements to the CHIPS code were completed to advance the comparison with radiative experiments. An updated 11-species air chemical reaction rate set was developed and analyzed to ensure compatibility with the chemical reaction models. In addition, species specific electronic collision numbers were found to be necessary for the electronic excitation model used in CHIPS. The CHIPS/NEQAIR interconnect was also updated to calculate radiative quantities directly from excited state populations. This required development of an ungrouping method which utilizes a polynomial least squares curve fit to ungroup a set of states using the local slope in a Boltzmann plot. With these improvements, reasonable agreement was observed between simulations and experimentally measured spectra in the VUV, UV/Vis, Vis/NIR, and IR spectral ranges and several areas of improvement were identified. The results of this hypersonic scenario represent the nominal simulation of a future sensitivity analysis of CHIPS input parameters.This research continues development of radiative results with the direct simulation Monte Carlo (DSMC) method for an 11-species air hypersonic flow. A 10.28 km/s, 0.2 Torr hypersonic shock tube experiment in rarefied air is simulated using the Computation of Hypersonic Ionizing Particles in Shocks (CHIPS) DSMC code and CHIPS results are post processed by the NEQAIR line-by-line radiative solver to produce emission spectra. The chosen scenario reproduces the conditions of recent NASA Electric Arc Shock Tube (EAST) experiments which are used as benchmarks for the simulated emission spectra. Several improvements to the CHIPS code were completed to advance the comparison with radiative experiments. An updated 11-species air chemical reaction rate set was developed and analyzed to ensure compatibility with the chemical reaction models. In addition, species specific electronic collision numbers were found to be necessary for the electronic excitation model used in CHIPS. The CHIPS/NEQAIR interconnect was also u...","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"12 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129262671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inverse problem of finding surface roughness parameters in rarefied gas flow","authors":"O. Aksenova, I. A. Khalidov","doi":"10.1063/1.5119658","DOIUrl":"https://doi.org/10.1063/1.5119658","url":null,"abstract":"The new algorithm is proposed to determine the real values of the roughness parameter σ1 from aerodynamic measurements solving the inverse problem. Roughness parameters are measured usually in the experiment from the profile diagram. However, the main parameter defining surface roughness according to usual standard procedures is not σ1, but the square mean deviation σ of the height of the surface. The roughness parameter in rarefied gas σ1 is not measured in the experiments. In addition, even if the parameter σ1 is measured, the main input into the influence of surface roughness on aerodynamic values takes the roughness of smaller scale, usually negligible on the profile diagram. Therefore σ1 must be determined from the solution of the inverse problem. The solution of the inverse problem is based on the simulation of surface roughness on micro-level by Gaussian or poly-Gaussian random field and on the representation of the scattering function on rough surface. The main advantage of the model is based on relative simple relations between the parameters of the model and the basic statistical characteristics of random field. Considered statistical approach permits to apply not only diffuse-specular model of the local scattering function of reflected gas atoms, but also Cercignani–Lampis scattering kernel or phenomenological models of scattering function. From the results we can see that the value of σ1 obtained from the solution of inverse problem is substantially higher than the value of σ1 from the profile diagram measurements.","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"443 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116331136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Validation of DSMC and CFD based catalysis modelling using plasma wind tunnel flows","authors":"W. Reschke, B. Massuti-Ballester, M. Pfeiffer, G. Herdrich, S. Fasoulas","doi":"10.1063/1.5119574","DOIUrl":"https://doi.org/10.1063/1.5119574","url":null,"abstract":"In this paper, results of the simulation tools URANUS and PICLas are compared to Plasma wind tunnel experiments. This is done for validation purposes of catalytic modelling within these tools. Therefore, the used experimental setup, from which the discussed simulation case is derived, and challenges in the flow characterization are shown. The main focus is on the validation of the newly developed surface Monte Carlo reconstruction method implemented in PICLas. For this method a brief description is given. It shows good agreements to experiments without a priori fitting of simulation parameters to experiments. However, further validation for evaluation of this method is needed.","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127602685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Periodically patterned radiometric pumps: Novel configurations and further applications","authors":"A. Lotfian, E. Roohi, S. Stefanov","doi":"10.1063/1.5119675","DOIUrl":"https://doi.org/10.1063/1.5119675","url":null,"abstract":"With the aid of direct simulation Monte Carlo (DSMC), a detailed investigation is reported considering the fluid and thermal characteristics of rarefied gas flow with regard to various arrangements for radiometric pumps featuring vane and ratchet structures. For the same, we consider three geometries of radiometric pumps consisting of channels with their bottom or top surfaces periodically patterned with different structures. The structures in the design of the first geometry are assumed to be on the bottom wall and consist of a simple vane. The second and third geometries contain either a channel with double isosceles triangular fins on its lowermost surface or a zigzag channel with double isosceles triangular fins on both walls. The temperature is kept steady on the horizontal walls of the channel; thus, radiometric flow is produced by subjecting the adjacent sides of the vane/ratchet to constant but unequal temperatures. The DSMC simulations are performed at a Knudsen number based on the vane/ratchet height of around one. The dominant mechanism in the production of radiometric force is clarified for the examined configurations. Our results demonstrate that at the investigated Knudsen number the zigzag channel experiences maximum induced velocity with a parabolic velocity profile, whereas its net radiometric force vanishes. In the case of all other configurations, the flow pattern resembles a Couette flow in the open section of the channel situated above the vane/ratchet. For binary mixtures, we demonstrate that the arrangement with the double isosceles teeth embedded just on the bottom wall performs a measurable gas separation with a linear species variation along the pump height.With the aid of direct simulation Monte Carlo (DSMC), a detailed investigation is reported considering the fluid and thermal characteristics of rarefied gas flow with regard to various arrangements for radiometric pumps featuring vane and ratchet structures. For the same, we consider three geometries of radiometric pumps consisting of channels with their bottom or top surfaces periodically patterned with different structures. The structures in the design of the first geometry are assumed to be on the bottom wall and consist of a simple vane. The second and third geometries contain either a channel with double isosceles triangular fins on its lowermost surface or a zigzag channel with double isosceles triangular fins on both walls. The temperature is kept steady on the horizontal walls of the channel; thus, radiometric flow is produced by subjecting the adjacent sides of the vane/ratchet to constant but unequal temperatures. The DSMC simulations are performed at a Knudsen number based on the vane/ratchet h...","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128043101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monte Carlo simulation of a gas transport system based on thermal induced flow","authors":"H. Matsumoto, Hiroki Tanaka, K. Koga, T. Morokuma","doi":"10.1063/1.5119569","DOIUrl":"https://doi.org/10.1063/1.5119569","url":null,"abstract":"In this study, thermal induced flow around a set of thin discs with slits in a straight pipe was investigated using the direct simulation Monte Carlo DSMC method. The surface temperature of one side of each disc was set higher than that of the other side, with the temperature ratio between high and low temperature surfaces (TH/TL) set equal to 1.05. The simulation showed that the pressure rapidly increases before and after the disc, suggesting that the thin disc plays the role of a pump by generating thermal induced flow around the slits in each thin disc.In this study, thermal induced flow around a set of thin discs with slits in a straight pipe was investigated using the direct simulation Monte Carlo DSMC method. The surface temperature of one side of each disc was set higher than that of the other side, with the temperature ratio between high and low temperature surfaces (TH/TL) set equal to 1.05. The simulation showed that the pressure rapidly increases before and after the disc, suggesting that the thin disc plays the role of a pump by generating thermal induced flow around the slits in each thin disc.","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134450621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative study of the discrete velocity and the moment method for rarefied gas flows","authors":"Weiqi Yang, X. Gu, D. Emerson, Yonghao Zhang, Shuo Tang","doi":"10.1063/1.5119619","DOIUrl":"https://doi.org/10.1063/1.5119619","url":null,"abstract":"In the study of rarefied gas dynamics, the discrete velocity method (DVM) has been widely employed to solve the gas kinetic equations. However, it is usually computationally expensive in dealing with complex geometry and high Mach number flows. In the present work, both classical third-order time implicit DVM and the moment method are employed in finding steady-state solutions of the force-driven Poiseuille flow and flow past a circle cylinder. Their performance, in terms of accuracy, has been compared and analyzed. Choosing the velocity distribution functions (VDFs) obtained from DVM solutions as the benchmark, we reconstruct the expanded VDFs using regularized 13 moment equations (R13) and regularized 26 moment equations (R26) and then compare the accuracy of the expanded VDFs with different order of Hermite polynomial expansions. From the computed velocity profiles and reconstructed VDFs, we have found that the moment method can extend the macroscopic equations into the early transition regime, and the R26 can relatively accurately represent the characteristics of the VDFs in comparison with the gas kinetic model. Conversely, the Navier-Stokes-Fourier (NSF) equations are not able to produce an accurate description of the expanded distribution functions.","PeriodicalId":374335,"journal":{"name":"31ST INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS: RGD31","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133613056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}