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Academic literature on the topic 'DSMC'

Author: Grafiati

Published: 4 June 2021

Last updated: 14 March 2023

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Journal articles on the topic "DSMC"

1

Zhao, Di, and Haiwu He. "DSMC: Fast direct simulation Monte Carlo solver for the Boltzmann equation by Multi-Chain Markov Chain and multicore programming." International Journal of Modeling, Simulation, and Scientific Computing 07, no. 02 (June 2016): 1650009. http://dx.doi.org/10.1142/s1793962316500094.

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Direct Simulation Monte Carlo (DSMC) solves the Boltzmann equation with large Knudsen number. The Boltzmann equation generally consists of three terms: the force term, the diffusion term and the collision term. While the first two terms of the Boltzmann equation can be discretized by numerical methods such as the finite volume method, the third term can be approximated by DSMC, and DSMC simulates the physical behaviors of gas molecules. However, because of the low sampling efficiency of Monte Carlo Simulation in DSMC, this part usually occupies large portion of computational costs to solve the Boltzmann equation. In this paper, by Markov Chain Monte Carlo (MCMC) and multicore programming, we develop Direct Simulation Multi-Chain Markov Chain Monte Carlo (DSMC3): a fast solver to calculate the numerical solution for the Boltzmann equation. Computational results show that DSMC3 is significantly faster than the conventional method DSMC.

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Karthikeyan, Viji, Anil Kumar Tiwari, Agalya Vedi, and Buvana Devaraju. "Input-output linearization of DC-DC converter with discrete sliding mode fuzzy control strategy." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 2 (April 1, 2022): 1223. http://dx.doi.org/10.11591/ijece.v12i2.pp1223-1232.

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The major thrust of the paper is on designing a fuzzy logic approach has been combined with a well-known robust technique discrete sliding mode control (DSMC) to develop a new strategy for discrete sliding mode fuzzy control (DSMFC) in direct current (DC-DC) converter. Proposed scheme requires human expertise in the design of the rule base and is inherently stable. It also overcomes the limitation of DSMC, which requires bounds of uncertainty to be known for development of a DSMC control law. The scheme is also applicable to higher order systems unlike model following fuzzy control, where formation of rule base becomes difficult with rise in number of error and error derivative inputs. In this paper the linearization of input-output performance is carried out by the DSMFC algorithm for boost converter. The DSMFC strategy minimizes the chattering problem faced by the DSMC. The simulated performance of a discrete sliding mode fuzzy controller is studied and the results are investigated.

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Luo, Le, and Ming-Zhong Yang. "Switching Power Supply Control Strategy Based on Monitoring Configuration." Journal of Nanoelectronics and Optoelectronics 16, no. 5 (May 1, 2021): 766–72. http://dx.doi.org/10.1166/jno.2021.2993.

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In this paper, a new discrete-time sliding mode predictive control (DSMPC) strategy with a PID sliding function is proposed for synchronous DC-DC Buck converter. The model predictive control, along with digital sliding mode control (DSMC) is able to further reducing the chattering phenomenon, steady-state error, overshoot, and undershoot of the converter output voltage. The proposed control method implementation only requires output error voltage evaluation. The effectiveness of the proposed DSMPC is proved through simulation results executed by the MATLAB/SIMULINK software. These results demonstrate its performance is superior to DSMC. The selected synchronous Buck converter in this paper has 380 V input voltage and 48 V output voltage that can be applied in sections of DC distribution systems.

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Olson, Spencer E., and Andrew J. Christlieb. "Gridless DSMC." Journal of Computational Physics 227, no. 17 (September 2008): 8035–64. http://dx.doi.org/10.1016/j.jcp.2008.04.038.

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DE SOCIO, L. M., and L. MARINO. "SIMULATION AND MODELLING OF FLOWS BETWEEN ROTATING CYLINDERS." Mathematical Models and Methods in Applied Sciences 10, no. 01 (February 2000): 73–83. http://dx.doi.org/10.1142/s0218202500000069.

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The equations which govern a number of models for flows between rotating cylinders at different Knudsen numbers are solved numerically by means of the direct simulation Monte Carlo method (DSMCM) to show their limitations. The DSMC code was firstly tested and validated against existing experimental data and then its results represented the reference data base for evaluating the characteristics of each model.

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Zhang, Qing-Wei, La-Mei Teng, Xin-Tian Zhang, Jing-Jing Zhang, Ying Zhou, Zhi-Rui Zhou, Yi-Chao Hou, Zhi-Zheng Ge, and Xiao-Bo Li. "Narrow-band imaging in the diagnosis of deep submucosal colorectal cancers: a systematic review and meta-analysis." Endoscopy 49, no. 06 (May 4, 2017): 564–80. http://dx.doi.org/10.1055/s-0043-103014.

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Abstract Background and aims Magnifying endoscopy with narrow-band imaging (M-NBI) has been widely used in the differential diagnosis of deep submucosal colorectal cancers (dSMCs) from superficial submucosal cancers (sSMCs) and intramucosal neoplasms. We aimed to pool the diagnostic efficacy of M-NBI and compare it with that of magnifying chromoendoscopy (M-CE) in diagnosing colorectal dSMC. Methods PubMed, EMBASE, and the Cochrane Library were searched to identify eligible studies. Meeting abstracts were also searched. A bivariate mixed-effects binary regression model was used in the meta-analysis to calculate the pooled diagnostic efficacy of M-NBI and compare it with that of M-CE in the diagnosis of dSMC. Subgroup analyses and meta-regression were conducted to explore sources of heterogeneity. Results We included 17 studies: 14 full texts and 3 meeting abstracts. The pooled sensitivity, specificity, and area under the summary receiver operating characteristic curve (AUC) with 95 % confidence intervals (CIs) in diagnosing dSMC were 74 % (66 % – 81 %; I2 = 84.6 %), 98 % (94 % – 99 %; I2 = 94.4 %), and 0.91 (0.88 – 0.93), respectively, for M-NBI. The pooled sensitivity, specificity and AUC (95 %CI) were 84 % (76 % – 89 %; I2 = 76.9 %), 97 % (94 % – 99 %; I2 = 90.2 %), and 0.97 (0.95 – 0.98), respectively, for M-CE. M-NBI had lower sensitivity (P < 0.01) than M-CE with similar specificity (P = 0.32). Subgroup analyses and meta-regression indicated that endoscopic diagnostic criteria, study type, endoscope type, risk of index test bias, and histopathological diagnostic criteria might be the sources of heterogeneity. Conclusions M-NBI and M-CE had comparable specificities in diagnosing dSMC, but the sensitivity of M-NBI was slightly lower than that of M-CE.

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Xiao, Hong, Yuhe Shang, and Di Wu. "DSMC Simulation and Experimental Validation of Shock Interaction in Hypersonic Low Density Flow." Scientific World Journal 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/732765.

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Direct simulation Monte Carlo (DSMC) of shock interaction in hypersonic low density flow is developed. Three collision molecular models, including hard sphere (HS), variable hard sphere (VHS), and variable soft sphere (VSS), are employed in the DSMC study. The simulations of double-cone and Edney’s type IV hypersonic shock interactions in low density flow are performed. Comparisons between DSMC and experimental data are conducted. Investigation of the double-cone hypersonic flow shows that three collision molecular models can predict the trend of pressure coefficient and the Stanton number. HS model shows the best agreement between DSMC simulation and experiment among three collision molecular models. Also, it shows that the agreement between DSMC and experiment is generally good for HS and VHS models in Edney’s type IV shock interaction. However, it fails in the VSS model. Both double-cone and Edney’s type IV shock interaction simulations show that the DSMC errors depend on the Knudsen number and the models employed for intermolecular interaction. With the increase in the Knudsen number, the DSMC error is decreased. The error is the smallest in HS compared with those in the VHS and VSS models. When the Knudsen number is in the level of 10−4, the DSMC errors, for pressure coefficient, the Stanton number, and the scale of interaction region, are controlled within 10%.

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Yan, T. H., B. Wu, B. He, W. H. Li, and R. B. Wang. "A Novel Fuzzy Sliding-Mode Control for Discrete-Time Uncertain System." Mathematical Problems in Engineering 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/1530760.

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This paper considers the sliding-mode control problem for discrete-time uncertain systems. It begins by presenting a discrete variable speed reaching law and a discrete-time sliding-mode controller (DSMC) designed using the proposed reaching law, followed by an analysis of their stability and dynamic performance. A sliding-mode controller with simple fuzzy logic is then proposed to further strengthen the dynamic performance of the proposed sliding-mode controller. Finally, the presented DSMC and the DSMC with fuzzy control for adjusting the parameters in this paper are compared with one of the previous proposed classic DSMC systems. The results of this simulation show that the DSMC presented here can suppress chatter and ensure good dynamic performances when fuzzy logic is used to tune the parameters.

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Burt, Jonathan M., and Iain D. Boyd. "Convergence Detection in Direct Simulation Monte Carlo Calculations for Steady State Flows." Communications in Computational Physics 10, no. 4 (October 2011): 807–22. http://dx.doi.org/10.4208/cicp.090210.311210a.

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AbstractA new criterion is presented to detect global convergence to steady state, and to identify local transient characteristics, during rarefied gas flow simulations performed using the direct simulation Monte Carlo (DSMC) method. Unlike deterministic computational fluid dynamics (CFD) schemes, DSMC is generally subject to large statistical scatter in instantaneous flow property evaluations, which prevents the use of residual tracking procedures as are often employed in CFD simulations. However, reliable prediction of the time to reach steady state is necessary for initialization of DSMC sampling operations. Techniques currently used in DSMC to identify steady state convergence are usually insensitive to weak transient behavior in small regions of relatively low density or recirculating flow. The proposed convergence criterion is developed with the goal of properly identifying such weak transient behavior, while adding negligible computational expense and allowing simple implementation in any existing DSMC code. Benefits of the proposed technique over existing convergence detection methods are demonstrated for representative nozzle/plume expansion flow, hypersonic blunt body flow and driven cavity flow problems.

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Di Staso, G., H. J. H. Clercx, S. Succi, and F. Toschi. "Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2080 (November 13, 2016): 20160226. http://dx.doi.org/10.1098/rsta.2016.0226.

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Hybrid particle–continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier–Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’.

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Dissertations / Theses on the topic "DSMC"

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Piekos, Edward S. (Edward Stanley). "DSMC modeling of micromechanical devices." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11149.

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Lunde, Dominic Charles. "A Homegrown DSMC-PIC Model for Electric Propulsion." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2066.

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Powering spacecraft with electric propulsion is becoming more common, especially in CubeSat-class satellites. On account of the risk of spacecraft interactions, it is important to have robust analysis and modeling tools of electric propulsion engines, particularly of the plasma plume. The Navier-Stokes equations used in classic continuum computational fluid dynamics do not apply to the rarefied plasma, and therefore another method must be used to model the flow. A good solution is to use the DSMC method, which uses a combination of particle modeling and statistical methods for modeling the simulated molecules. A DSMC simulation known as SINATRA has been developed with the goal to model electric propulsion plumes. SINATRA uses an octree mesh, is written in C++, and is designed to be expanded by further research. SINATRA has been initially validated through several tests and comparisons to theoretical data and other DSMC models. This thesis examines expanding the functionality of SINATRA to simulate charged particles and make SINATRA a DSMC-PIC hybrid. The electric potential is calculated through a 7-point 3D stencil on the mesh nodes and solved with a Gauss-Seidel solver. It is validated through test cases of charged particles to demonstrate the accuracy and capabilities of the model. An ambipolar diffusion test case is compared to a neutral diffusion case and the electric field is shown to stabilize the diffusion rate. A steady state flow test case shows the simulation is able to stabilize and solve the electric potential for a plume-like scenario. It includes additional features to simplify further research including a comprehensive user manual, industry-standard version control, text file inputs, GUI control, and simple parallelism of the simulation. Compilation and execution are standardized to be simple and platform independent to allow longevity of the code base. Finally, the execution bottlenecks of linking particles to cells and particle moving were removed to reduce the simulation time by 95%.

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Palaniswaamy, Geethpriya. "DSMC multicomponent aerosol dynamics sampling algorithms and aerosol processes /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4737.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Dec. 12, 2007). Vita. Includes bibliographical references.

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Palharini, Rodrigo Cassinel. "Atmospheric reentry modelling using an open-source DSMC code." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24375.

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Aerothermodynamic investigations of hypersonic re-entry vehicles provides crucial information to other key disciplines as structures and materials, assisting the development of efficient and lightweight thermal protection systems (TPS). Under the transitional flow regime, where chemical and thermal nonequilibrium are predominant, the most successful numerical method for such studies has been the direct simulation Monte Carlo (DSMC) numerical technique. In the present work, the solver dsmcFoam has been benchmarked against experimental, numerical, and theoretical data found in the open literature for inert and chemically reactive flows. The Quantum-Kinetic (QK) chemistry model with a full set of 19 chemical reactions has been implemented into the code and it proved to be essential in the correct prediction of the shock wave structure and heating flux to the vehicle's surface during the re-entry phase. Having implemented the QK chemistry model, the dsmcFoam solver was employed to investigate thermal protection system discontinuities. These TPS discontinuities, representative of panel-to-panel joints or the impact of micro meteorites/ice droplets, were modelled as a family of cavities with different length-to-depth ratios. The results showed that the cavity length has a significant impact on the flowfield structure and aerodynamic surface quantities distribution inside and around the cavities. In addition, for L/D = 5, the flow separates at the cavity upstream lip and attaches to the cavity bottom surface, representing a potentially catastrophic feature under rarefied gas conditions. Furthermore, the same phenomena is only observed in the continuum regime when L/D > 14.

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Masters, Nathan Daniel. "Efficient Numerical Techniques for Multiscale Modeling of Thermally Driven Gas Flows with Application to Thermal Sensing Atomic Force Microscopy." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11574.

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The modeling of Micro- and NanoElectroMechanical Systems (MEMS and NEMS) requires new computational techniques that can deal efficiently with geometric complexity and scale dependent effects that may arise. Reduced feature sizes increase the coupling of physical phenomena and noncontinuum behavior, often requiring models based on molecular descriptions and/or first principles. Furthermore, noncontinuum effects are often localized to small regions of (relatively) large systemsprecluding the global application of microscale models due to computational expense. Multiscale modeling couples efficient continuum solvers with detailed microscale models to providing accurate and efficient models of complete systems. This thesis presents the development of multiscale modeling techniques for nonequilibrium microscale gas phase phenomena, especially thermally driven microflows. Much of this focuses on improving the ability of the Information Preserving DSMC (IP-DSMC) to model thermally driven flows. The IP-DSMC is a recent technique that seeks to accelerate the solution of direct simulation Monte Carlo (DSMC) simulations by preserving and transporting certain macroscopic quantities within each simulation molecules. The primary contribution of this work is the development of the Octant Splitting IP-DSMC (OSIP-DSMC) which recovers previously unavailable information from the preserved quantities and the microscopic velocities. The OSIP-DSMC can efficiently simulate flow fields induced by nonequilibrium systems, including phenomena such as thermal transpiration. The OSIP-DSMC provides an efficient method to explore rarefied gas transport phenomena which may lead to a greater understanding of these phenomena and new concepts for how these may be utilized in practical engineering systems. Multiscale modeling is demonstrated utilizing the OSIP-DSMC and a 2D BEM solver for the continuum (heat transfer) model coupled with a modified Alternating Schwarz coupling scheme. An interesting application for this modeling technique is Thermal Sensing Atomic Force Microscopy (TSAFM). TSAFM relies on gas phase heat transfer between heated cantilever probes and the scanned surface to determine the scan height, and thus the surface topography. Accurate models of the heat transfer phenomena are required to correctly interpret scan data. This thesis presents results demonstrating the effect of subcontinuum heat transfer on TSAFM operation and explores the mechanical effects of the Knudsen Force on the heated cantilevers.

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Al-Mohssen, Husain Ali 1977. "An excursion with the Boltzmann equation at low speeds : variance-reduced DSMC." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61591.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 133-139).
The goal of the present thesis is to develop a practical method for simulating low-signal kinetic (small-scale) gaseous flows. These flows have recently received renewed attention in connection with the design and optimization of MEMS/NEMS devices operating in gaseous environments; they are typically described using the Boltzmann equation which is most efficiently solved using a stochastic particle simulation method known as direct simulation Monte Carlo (DSMC). The latter is a simple and versatile simulation method which is very efficient in producing samples of the single particle distribution function which can be used for estimating hydrodynamic properties. Unfortunately, in cases where the signal of interest is small (e.g. low-speed flows), the computational cost associated with reducing the statistical uncertainty of simulation outputs becomes overwhelming. This thesis presents a variance reduction approach for reducing the statistical uncertainty associated with low-signal flows thus making their simulation not only possible but also efficient. Variance reduction is achieved using a control variate approach based on the observation that low-signal flows are typically close to an equilibrium state. As with previous variance reduction methods, significant variance reduction is achieved making the simulation of arbitrarily small deviations from equilibrium possible. However, in contrast to previous variance-reduction methods, the method proposed, which we will refer to as VRDSMC, is able to reduce the variance with virtually no modification to the standard DSMC algorithm. This is achieved by introducing an auxiliary equilibrium simulation which, via an importance weight formulation, uses the same particle data as the non-equilibrium (DSMC) calculation; subtracting the equilibrium from the non-equilibrium hydrodynamic fields drastically reduces the statistical uncertainty of the latter because the two fields are correlated. By retaining the basic DSMC formulation, in contrast to previous approaches, the VRDSMC approach combines ease of implementation with computational efficiency and the ability to simulate all molecular interaction models available within the DSMC formulation. Our validation tests show that the proposed VRDSMC method provides considerable variance reduction for only a small increase in computational cost and approximation error compared to equivalent DSMC simulations. In other words, by addressing the major weakness associated with DSMC, VRDSMC is well suited to the solution of low-signal kinetic problems of practical interest.
by Husain Ali Al-Mohssen.
Ph.D.

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Al-Kouz, Wael G. "Investigation of Supersonic Gas Flows into Nanochannels Using an Unstructured 3D Direct Simulation Monte Carlo Method." Digital WPI, 2009. https://digitalcommons.wpi.edu/etd-dissertations/317.

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"This dissertation is devoted to the computational investigation of supersonic gas flows in rectangular nanochannels with scales between 100 nm and 1000 nm, using an unstructured three-dimensional Direct Simulation Monte Carlo (U3DSMC) methodology. This dissertation also contributes to the computational mathematics background of the U3DSMC method with validations and verifications at the micronscale and nanoscale, as well as with the investigation of the statistical fluctuations and errors associated with U3DSMC simulations at the nanoscale. The U3DSMC code is validated by comparisons with previous two dimensional DSMC simulations of flows in micron-scale rectangular channels. The simulation involves the supersonic flow of nitrogen into a microchannel with height of 1.2 m and width of 6 m. The free stream conditions correspond to a pressure of 72,450 Pa, Mach number , Knudsen number and mean free path nm. The U3DSMC centerline temperature, heat flux to the wall, and mean velocity as a function of the transverse direction are in very good agreement with previous 2D results. Statistical fluctuations and errors in U3DSMC have added significance in nanoscale domains because the number of real particles can be very small inside a computational cell. The effect of the number of samples, the number of computational particles in a Delaunay cell, and the Mach number on the fractional errors of density, velocity and temperature are investigated for uniform and pressure-driven nanoscale flows. The uniform nanoflow is implemented by applying a and free stream boundary condition with m-3, K, nm in a domain that requires resolution of a characteristic length scale nm. The pressure-driven flows consider a nanochannel of 500 nm height, 100 nm width and 4 m length. Subsonic boundary conditions are applied with inlet pressure 101,325 Pa and outlet pressure of 10132.5 Pa. The analysis shows that U3DSMC simulations at nanoscales featuring 10-30 particles per Delaunay cell result in statistical errors that are consistent with theoretical estimates. The rarefied flow of nitrogen with speed ratio of 2, 5, and 10, pressure of 10.132 kPa into rectangular nanochannels with height of 100, 500 and 1000 nm is investigated using U3DSMC. The investigation considers rarefaction effects with =0.481, 0.962, 4.81, geometric effects with nanochannel aspect ratios of (L/H) from AR=1, 10, 100 and back-pressure effects with imposed pressures from 0 to 200 kPa. The computational domain features a buffer region upstream of the inlet and the nanochannel walls are assumed to be diffusively reflecting at the free stream temperature of 273 K. The analysis is based on the phase space distributions as well as macroscopic flow variables sampled in cells along the centerline. The phase space distributions show the formation of a disturbance region ahead of the inlet due to slow particles backstreaming through the inlet and the formation of a density enhancement with its maximum inside the nanochannel. The velocity phase-space distributions show a low-speed particle population generated inside the nanochannel due to wall collisions which is superimposed with the free stream high-speed population. The mean velocity decreases, while the number density increases in the buffer region. The translational temperature increases in the buffer region and reaches its maximum near the inlet. For AR=10 and 100 nanochannels the gas reaches near equilibrium with the wall temperature. The heat transfer rate is largest near the inlet region where non-equilibrium effects are dominant. For =0.481, 0.962, 4.81, vacuum back pressure, and AR=1, the nanoflow is supersonic throughout the nanochannel, while for AR=10 and 100, the nanoflow is subsonic at the inlet and becomes sonic at the outlet. For =0.962, AR=1, and imposed back pressure of 120 kPa and 200 kPa, the nanoflow becomes subsonic at the outlet. For =0.962 and AR=10, the outlet pressure nearly matches the imposed back pressure with the nanoflow becoming sonic at 40 kPa and subsonic at 100 kPa. Heat transfer rates at the inlet and mass flow rates at the outlet are in good agreement with those obtained from theoretical free-molecular models. The flows in these nanochannels share qualitative characteristics found in microchannels ad well as continuum compressible flows in channels with friction and heat loss. The rarefied flow of nitrogen with speed ratio of 2, 5, 10, at an atmospheric pressure of 101.32 kPa into rectangular nanochannels with height of 100 and 500 nm is investigated using U3DSMC. The investigation considers rarefaction effects with =0.0962 and 4.81, geometric effects with nanochannel aspect ratios of (L/H) of AR=1 and 10 and vacuum back-pressure. Phase plots and sample-averaged macroscopic parameters are used in the analysis. Under vacuum back pressure the centerline velocity decreases in the buffer region from its free stream value. For 0.481, 0.0962 and AR=1 the Mach number is supersonic at the inlet and remains supersonic throughout the nanochannel. For 0.481, 0.0962 and AR=10, the flow becomes subsonic at the inlet and shows a sharp increase in pressure. The Mach number, subsequently, increases and reaches the sonic point at the outlet. For 0.481, 0.0962 and AR=1 the translational temperature reaches a maximum near the inlet and decreases monotonically up to the outlet. For 0.481, 0.0962 and AR=10, the translational temperature reaches a maximum near the inlet and then decreases to come in near equilibration with the wall temperature of 273 K. "

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Oh, David Y. (David Younghee). "Computational modeling of expanding plasma plumes in space using a PIC-DSMC algorithm." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10756.

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Cave, Hadley Mervyn. "Development of Modelling Techniques for Pulsed Pressure Chemical Vapour Deposition (PP-CVD)." Thesis, University of Canterbury. Mechanical Engineering, 2008. http://hdl.handle.net/10092/1572.

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In this thesis, a numerical and theoretical investigation of the Pulsed Pressure Chemical Vapour Deposition (PP-CVD) progress is presented. This process is a novel method for the deposition of thin films of materials from either liquid or gaseous precursors. PP-CVD operates in an unsteady manner whereby timed pulsed of the precursor are injected into a continuously evacuated reactor volume. A non-dimensional parameter indicating the extent of continuum breakdown under strong temporal gradients is developed. Experimental measurements, supplemented by basic continuum simulations, reveal that spatio-temporal breakdown of the continuum condition occurs within the reactor volume. This means that the use of continuum equation based solvers for modelling the flow field is inappropriate. In this thesis, appropriate methods are developed for modelling unsteady non-continuum flows, centred on the particle-based Direct Simulation Monte Carlo (DSMC) method. As a first step, a basic particle tracking method and single processor DSMC code are used to investigate the physical mechanisms for the high precursor conversion efficiency and deposition uniformity observed in experimental reactors. This investigation reveals that at soon after the completion of the PP-CVD injection phase, the precursor particles have an approximately uniform distribution within the reactor volume. The particles then simply diffuse to the substrate during the pump-down phase, during which the rate of diffusion greatly exceeds the rate at which particles can be removed from the reactor. Higher precursor conversion efficiency was found to correlate with smaller size carrier gas molecules and moderate reactor peak pressure. An unsteady sampling routine for a general parallel DSMC method called PDSC, allowing the simulation of time-dependent flow problems in the near continuum range, is then developed in detail. Nearest neighbour collision routines are also implemented and verified for this code. A post-processing procedure called DSMC Rapid Ensemble Averaging Method (DREAM) is developed to improve the statistical scatter in the results while minimising both memory and simulation time. This method builds an ensemble average of repeated runs over small number of sampling intervals prior to the sampling point of interest by restarting the flow using either xi a Maxwellian distribution based on macroscopic properties for near equilibrium flows (DREAM-I) or output instantaneous particle data obtained by the original unsteady sampling of PDSC for strongly non-equilibrium flows (DREAM-II). The method is validated by simulating shock tube flow and the development of simple Couette flow. Unsteady PDSC is found to accurately predict the flow field in both cases with significantly reduced run-times over single processor code and DREAM greatly reduces the statistical scatter in the results while maintaining accurate particle velocity distributions. Verification simulations are conducted involving the interaction of shocks over wedges and a benchmark study against other DSMC code is conducted. The unsteady PDSC routines are then used to simulate the PP-CVD injection phase. These simulations reveal the complex flow phenomena present during this stage. The initial expansion is highly unsteady; however a quasi-steady jet structure forms within the reactor after this initial stage. The simulations give additional evidence that the collapse of the jet at the end of the injection phase results in an approximately uniform distribution of precursor throughout the reactor volume. Advanced modelling methods and the future work required for development of the PP-CVD method are then proposed. These methods will allow all configurations of reactor to be modelled while reducing the computational expense of the simulations.

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Rose, Martin. "Untersuchungen zur Oberflächenchemie der Atomlagenabscheidung und deren Einfluss auf die Effizienz von Prozessen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-63111.

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In dieser Arbeit werden verschiedene Prozesse zur Atomlagenabscheidung (ALD) von TiO2 und HfO2 experimentell untersucht. Die Untersuchungen schließen eine experimentelle Charakterisierung des Schichtwachstums sowie eine massenspektrometrische Analyse der Reaktionsprodukte ein. Im Detail wurden der ALD-Prozess mit Cp*Ti(OMe)3 und Ozon zur Abscheidung von TiO2 sowie der ALD-Prozess mit TEMAHf und Ozon zur Abscheidung von HfO2 untersucht. Der theoretische Teil der Arbeit beginnt mit einer Methode zur Bestimmung des absoluten Haftkoeffizienten. Anschließend werden numerische Modelle entwickelt, welche die Adsorption von Präkursormolekülen durch strukturierte Substrate beschreiben. Diese Modelle enthalten die Substratstruktur und den absoluten Haftkoeffizienten. Es wird eine statistische numerische Methode entwickelt, mit der der Gastransport in dem ALD-Reaktor statistisch beschrieben wird. Die statistischen Größen, welche die Gasdynamik im Reaktor beschreiben, werden mit der Discrete Simulation Monte Carlo (DSMC) Methode bestimmt. Mit dieser Methode und den Modellen der Adsorption kann der komplette ALD-Prozess simuliert werden. Die neu entwickelte Methode wird verwendet um die Effizienz verschiedener ALD-Reaktoren in Abhängigkeit des absoluten Haftkoeffizienten, der Substratstruktur sowie der Prozessbedingungen zu untersuchen. Die Geometrie des Reaktors wird variiert und mit der Referenzgeometrie verglichen
This dissertation is divided into an experimental part and a theoretical part. The experimental part describes the atomic layer deposition (ALD) of TiO2 and HfO2. TDMAT and Cp*Ti(OMe)3 were used as titanium precursors, while TEMAHf was used as the hafnium precursor. Ozone was used as the oxygen source. The self limiting film growth and the temperature window of these ALD processes were investigated. The reaction by-products of the Cp*Ti(OMe)3/O3 process were identified by quadrupol mass spectrometry (QMS). The QMS analysis of the TEMAHf/O3 process revealed that water is formed during the metal precursor pulse. The theoretical part of this thesis describes the development of models and numerical methods to simulate the ALD as a whole. First of all, a model for the adsorption of precursor molecules by planar substrates was developed. This model was extended to describe the adsorption of precursor molecules inside a cylindrical hole with an aspect ratio of 20, 40 and 80. The adsorption of precursor molecules is dominated by the absolute sticking coefficient (SC), i.e., the reactivity of the precursor molecules. From the numerical model the saturation profiles along the wall of a cylindrical hole can be determined. From the comparison of the simulated profile with an experimentally determined thickness profile the SC can be determined. This method was used to determine the SC of the precursors examined in the experimental part. The SC of TEMAHf increases exponentially with the substrate temperature. A discrete particle method (DSMC) was used to derive a statistical description of the gas kinetics inside an ALD reactor. Combining the statistical description of the gas transport and the numerical models of the adsorption, it is possible to simulate the ALD for any combination of reactor, substrate and SC. It is possible to distinguish the contribution of the reactor geometry, the process parameters and the process chemistry (SC) to the process efficiency. Therefore, the ALD reactor geometry can be optimized independently of the process chemistry. This method was used to study a shower head ALD reactor. The reactor geometry, the composition of the gas at the inlet and the position of the inlet nozzles was varied in order to find more efficient ALD reactors. The efficiency of the reference geometry is limited by the inlet nozzles close to the exhaust and the decrease of the pressure on the substrate near the exhaust. The efficiency of ALD processes with different SCs was simulated for planar and structured substrates with a diameter of 300 mm and 450 mm

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Books on the topic "DSMC"

1

College, Defense Systems Management, ed. DSMC at a glance. Fort Belvoir, VA (9820 Belvoir Rd., Ft Belvoir 22060-5565): Defense Systems Management College, 1995.

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College, Defense Systems Management, ed. DSMC at a glance. Fort Belvoir, VA (9820 Belvoir Rd., Ft Belvoir 22060-5565): Defense Systems Management College, 1995.

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College, Defense Systems Management, ed. DSMC at a glance. Fort Belvoir, VA (9820 Belvoir Rd., Ft Belvoir 22060-5565): Defense Systems Management College, 1995.

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Hall, Mary-jo. Process improvement: The DSMC approach. Fort Belvoir, Va: Defense Systems Management College, 1994.

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Hall, Mary-jo. Process improvement: The DSMC approach (PRIMA). 2nd ed. Fort Belvoir, Va: Defense Systems Management College, 1995.

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N, Gupta Roop, Price Joseph M, and United States. National Aeronautics and Space Administration., eds. DSMC simulations of OREX entry conditions. [Washington, D.C: National Aeronautics and Space Administration, 1996.

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United States. Dept. of Defense., ed. DSMC Program Managers Tool Kit, March 1999. [S.l: s.n., 1999.

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A'Hearn, Francis W. I want you to know about these DSMC publications. Fort Belvoir, Va: Defense Systems Management College, Dept. of Research and Information, 1986.

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A, Bird G., and Langley Research Center, eds. Implementation of a vibrationally linked chemical reaction model for DSMC. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1994.

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College, Defense Systems Management, ed. A Special course at DSMC just for multinational program managers. [Fort Belvoir, VA: Defense Systems Management College, 1985.

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Book chapters on the topic "DSMC"

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La Torre, Federico, Sasa Kenjeres, Chris R. Kleijn, and Jean-Luc P. A. Moerel. "Evaluation of Micronozzle Performance through DSMC, Navier-Stokes and Coupled DSMC/Navier-Stokes Approaches." In Lecture Notes in Computer Science, 675–84. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01970-8_67.

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Pallegoix, J. F. "DSMC calculation on a delta wing." In Hypersonic Flows for Reentry Problems, 960–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77922-0_73.

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Moss, James N., Joseph M. Price, and M. Cevdet Celenligil. "DSMC Calculations for The Double Ellipse." In Hypersonic Flows for Reentry Problems, 882–95. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76527-8_57.

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Cevdet Celenligil, M., and James N. Moss. "DSMC Calculations for The Delta Wing." In Hypersonic Flows for Reentry Problems, 1051–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76527-8_68.

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Ignatieva, Svetlana, and Vladimir Memnonov. "Parallel Implementation of a Corrected DSMC Method." In Lecture Notes in Computer Science, 436–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/3-540-44743-1_45.

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Müller, Matthias, and Hans J. Herrmann. "DSMC — A Stochastic Algorithm for Granular Matter." In Physics of Dry Granular Media, 413–20. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-017-2653-5_30.

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Roohi, Ehsan. "DSMC Simulations of Nanoscale and Microscale Gas Flow." In Encyclopedia of Microfluidics and Nanofluidics, 681–93. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4614-5491-5_1723.

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Scanlon, T. J., C. White, M. Schuebler, R. E. Brown, and J. M. Reese. "Thermochemistry Modelling in an Open Space DSMC Code." In 28th International Symposium on Shock Waves, 145–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25688-2_22.

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Roohi, Ehsan. "DSMC Simulations of Nanoscale and Microscale Gas Flow." In Encyclopedia of Microfluidics and Nanofluidics, 1–14. Boston, MA: Springer US, 2013. http://dx.doi.org/10.1007/978-3-642-27758-0_1723-2.

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Sengil, N., and F. O. Edis. "Implementation of parallel DSMC method to adiabatic piston problem." In Lecture Notes in Computational Science and Engineering, 75–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-92744-0_9.

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Conference papers on the topic "DSMC"

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Garcia, A. "DSMC/Continuum hybrid methods." In RAREFIED GAS DYNAMICS: 22nd International Symposium. AIP, 2001. http://dx.doi.org/10.1063/1.1407584.

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Bird, G. A. "Chemical Reactions in DSMC." In 27TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS. AIP, 2011. http://dx.doi.org/10.1063/1.3562806.

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Breuer, Kenneth, Edward Piekos, and David Gonzales. "DSMC simulations of continuum flows." In 30th Thermophysics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-2088.

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Piekos, Edward, and Kenneth Breuer. "DSMC modeling of micromechanical devices." In 30th Thermophysics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-2089.

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Bobylev, Alexander V., Irina F. Potapenko, and Stanislav A. Karpov. "DSMC methods for multicomponent plasmas." In 28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2012. AIP, 2012. http://dx.doi.org/10.1063/1.4769589.

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Gallis, M. A., J. R. Torczynski, D. J. Rader, G. A. Bird, and Takashi Abe. "An Improved-Accuracy DSMC Algorithm." In RARIFIED GAS DYNAMICS: Proceedings of the 26th International Symposium on Rarified Gas Dynamics. AIP, 2008. http://dx.doi.org/10.1063/1.3076490.

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Aktas, Ozgur, N. R. Aluru, and Umberto Ravaioli. "DSMC Simulation of Microfilter Elements." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0305.

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Abstract Direct Simulation Monte Carlo (DSMC) analysis of micro-filter elements for collection of airborne particles is considered in this paper. Three filter elements with different dimensions were simulated. Boundary conditions were chosen to simulate an array of filters. Our results indicate that, as the filter gets smaller, the slip flow will be critical in determining flow characteristics. The change in the flow rate and the characteristics of the flow in different dimensions are investigated.

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BARTEL, TIMOTHY, and CHARLES JUSTIZ. "DSMC simulation of ionized rarefied flows." In 23rd Fluid Dynamics, Plasmadynamics, and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1993. http://dx.doi.org/10.2514/6.1993-3095.

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Hash, D., and H. Hassan. "A hybrid DSMC/Navier-Stokes solver." In 33rd Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-410.

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Gallis, Michael, John Torczynski, and Daniel Rader. "DSMC Convergence Behavior for Transient Flows." In 39th AIAA Thermophysics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2007. http://dx.doi.org/10.2514/6.2007-4258.

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Reports on the topic "DSMC"

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Gallis, Michail A., and Edward Stanley Piekos. Accelerating DSMC data extraction. Office of Scientific and Technical Information (OSTI), October 2006. http://dx.doi.org/10.2172/922066.

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Wadsworth, D. C., D. B. VanGilder, I. J. Wysong, C. Kaplan, and D. Mott. SUPREM-DSMC Version 1.0 User's Manual. Fort Belvoir, VA: Defense Technical Information Center, July 2000. http://dx.doi.org/10.21236/ada411285.

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Gimelshein, Sergey, Gennady Markelov, and Marc Rieffel. Collision Models in the Hawk DSMC Implementation. Fort Belvoir, VA: Defense Technical Information Center, July 1996. http://dx.doi.org/10.21236/ada448751.

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Schneller, George. Program Manager - A Bimonthly Magazine of DSMC. Fort Belvoir, VA: Defense Technical Information Center, December 1999. http://dx.doi.org/10.21236/ada372041.

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Wadsworth, Dean C., Douglas B. VanGilder, and Virendra K. Dogra. Gas-Surface Interaction Model Evaluation for DSMC Applications. Fort Belvoir, VA: Defense Technical Information Center, July 2002. http://dx.doi.org/10.21236/ada406005.

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BARTEL, TIMOTHY J., STEVEN J. PLIMPTON, and MICHAIL A. GALLIS. Icarus: A 2-D Direct Simulation Monte Carlo (DSMC) Code for Multi-Processor Computers. Office of Scientific and Technical Information (OSTI), October 2001. http://dx.doi.org/10.2172/789256.

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Campbell, David, Dean Wadsworth, Douglas VanGilder, Ingrid Wysong, and Carolyn Kaplan. SUPREM-DSMC: A New Scalable, Parallel, Reacting, Multidimensional Direct Simulation Monte Carlo Flow Code. Fort Belvoir, VA: Defense Technical Information Center, April 2000. http://dx.doi.org/10.21236/ada407889.

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Campbell, David, Dean Wadsworth, Ingrid Wysong, and Carolyn Kaplan. SUPREM DSMC: A New Scalable, Parallel, Reacting, Multidimensional Direct Simulation Monte Carlo Flow Code. Fort Belvoir, VA: Defense Technical Information Center, February 2000. http://dx.doi.org/10.21236/ada409492.

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Stewart, Jesse, Norman S. Bull, and John Krieger. Acquisition Program Transition Workshops: An Element of the DSMC Program Manager Mission Assistance Capability. Fort Belvoir, VA: Defense Technical Information Center, October 2011. http://dx.doi.org/10.21236/ada606209.

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Bartel, T., S. Plimpton, J. Johannes, and J. Payne. Icarus: A 2D direct simulation Monte Carlo (DSMC) code for parallel computers. User`s manual - V.3.0. Office of Scientific and Technical Information (OSTI), October 1996. http://dx.doi.org/10.2172/399675.

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