Download or read book Modeling of Microscale Gas Flows Using the Direct Simulation Monte Carlo Method written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rarefied Gas Flows in Microscale Geometries written by Stephanie Y. Docherty and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate predictions of the flow behaviour in microscale geometries are needed, for example, to design and optimise micro devices, and to ensure their safety/reliability. Rarefied gas flows in such geometries tend, however, to be far from local thermodynamic equilibrium, meaning that the flow behaviour cannot be described by conventional fluid mechanics. Alternative approaches for modelling 'non-equilibrium' gas flows have been proposed in recent years; because analytical solution methods are subject to significant limitations, the direct simulation Monte Carlo (DSMC) method is, at present, the most practical numerical simulation tool for dilute gases. Unfortunately, the computational expense of tracking and computing collisions between thousands (or perhaps millions) of DSMC particles means that simulating the scales of realistic flow problems can require months (or even years) of computing time. This has resulted in the development of continuum-DSMC 'hybrid' methods, which aim to combine the efficiency of a conventional continuum-fluid description with the detail and accuracy of the DSMC method. This thesis focuses on the development of a continuum-DSMC method that offers a more general approach than existing methods. Using a heterogeneous framework with a field-wise coupling strategy, this new method is not subject to the limitations of the well-known domain decomposition framework, or the restrictions of the heterogeneous point-wise coupling approach. The continuum-fluid description is applied across the entire flow field, while the DSMC method is performed in dispersed micro elements that can be any size and at any location; these elements then provide the continuum description with updated constitutive and boundary information. Unlike most methods in the literature, the coupling strategy presented here is able to cope with heat transfer, and so non-isothermal flows can be simulated. Testing and validation of this new continuum-DSMC method is performed by simulating a number of benchmark cases and comparing the results with full DSMC solutions of the same cases. Two 1D flow problems are considered: a micro Fourier flow problem tests the energy coupling procedure of the method, and a high-speed micro Couette flow problem demonstrates the full coupling algorithm. In general, the method's accuracy is found to depend on the arrangement of the micro elements - with sufficient micro resolution, good agreement with the equivalent full DSMC simulations can be obtained. Although the hybrid method offers no computational speed-up over the full DSMC simulations for several of these 1D test cases and only modest speed-ups for the others, both of these 1D ow problems are simulated only to validate the coupling strategy of the method. Considerable speed-ups are offered by the method when simulating a larger and more realistic flow problem: a microchannel with a high-aspect-ratio cross-section acts as a representative geometry for modelling a gas flow through a narrow microscale crack. While the limitations of existing hybrid methods preclude their use for this type of high-aspect-ratio geometry, the new hybrid method is able to model this problem under isothermal and non-isothermal conditions. The implementation of the method is simplified to 2D by assuming that the flow variation in the streamwise direction is negligible, i.e. the method is applied to the microchannel cross-section only. Accurate predictions of the mass flow rate and the streamwise velocity field are obtained for a number of test cases; accurate predictions of the temperature field are also obtained when there is a temperature difference between the bounding walls.
Download or read book Rarefied Gas Dynamics written by Ching Shen and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "This book elucidates the methods of molecular gas dynamics or rarefied gas dynamics which treat the problems of gas flows when the discrete molecular effects of the gas prevail under the circumstances of low density, the emphases being stressed on the basis of the methods, the direct simulation Monte Carlo method applied to the simulation of non-equilibrium effects and the frontier subjects related to low speed microscale rarefied gas flows. It provides a solid basis for the study of molecular gas dynamics for senior students and graduates in the aerospace and mechanical engineering departments of universities and colleges. It gives a general acquaintance of modern developments of rarefied gas dynamics in various regimes and leads to the frontier topics of non-equilibrium rarefied gas dynamics and low speed microscale gas dynamics. It will be also of benefit to the scientific and technical researchers engaged in aerospace high altitude aerodynamic force and heating design and in the research on gas flow in MEMS" -- SpringerLink.
Download or read book Microscale Gas Flow written by Toby Thatcher and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Toward the Improved Simulation of Microscale Gas Flow written by Matthew James McNenly and published by . This book was released on 2006 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Study and Numerical Modeling of Gas Flow in Microchannels and Micronozzles written by and published by . This book was released on 2005 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the course of this research effort gas flows in microchannels and micronozzles were studied both experimentally and numerically. For the experimental study a flow visualization system was built and used to Study gas flows in microscale. Gas velocity measurements in microscope were conducted using both Laser Induced Fluorescence technique in conjunction with Image Correlation Velocimetry and Molecular Tagging Velocimetry technique. For the numerical study three different approaches were utilized. Continuum computational fluid dynamics was first used to study gas flows in microchannels and micronozzles. For micronozzles, effects of geometrical scaling down and different gas propellants were studied. For microchannels, slip versus no-slip boundary condition and compressibility and rarefaction effects were studied. Secondly, Direct simulation Monte Carlo (DSMC) method was used to study low Reynolds number flows in a conical micronozzle. The DSMC simulations were compared with the continuum model and available experimental data, and also used to study propellant gas temperature effect on the generated thrust Thirdly, a Unified Flow Solver that utilizes hybrid approach using deterministic Boltzmann solver for highly non-equilibrium flows at high Knudsen number and continuum solvers for low Knudsen numbers was tested and demonstrated for gas flows in microscale. Tested cases included gas flows in both microchannels and micronozzles.
Download or read book Molecular Gas Dynamics and the Direct Simulation of Gas Flows written by G. A. Bird and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The direct simulation Monte Carlo (or DSMC) method has become widely used for engineering and scientific studies of gas flows that involve low densities or very small physical dimensions. This book is developed from first principles and has been extended to cover the new models and procedures.
Download or read book Efficient Numerical Techniques for Multiscale Modeling of Thermally Driven Gas Flows with Application to Thermal Sensing Atomic Force Microscopy written by Nathan Daniel Masters and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Monte Carlo Methods in Mechanics of Fluid and Gas written by Oleg Mikhaĭlovich Belot︠s︡erkovskiĭ and published by World Scientific. This book was released on 2010 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is devoted to analysis of Monte Carlo methods developed in rarefied gas dynamics. Presented is the short history of the development of such methods, described are their main properties, their advantages and deficiencies. It is shown that the contemporary stage in the progress of computational methods cannot be regarded without a complex approach to the preparation of algorithms taking into account all the peculiarities of the problem under consideration, that is, of the physical nature of a process, the mathematical model and the theoretical aspects of computational mathematics and stochastic processes. Thoroughly investigated is the possibility of application of Monte Carlo methods in some kindred areas of science which are non-traditional for the use of statistical modeling (continuous media, turbulence). Considered are the possible directions of development of statistical modeling.
Download or read book Direct Simulation Monte Carlo Modeling for Non Equilibrium Flowfield Applications written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Questions important to modeling of nonequilibrium gas flows are examined. Testing and validation of Direct Simulation Monte Carlo (DSMC) codes have been performed. Several models for vibrational relaxation and chemical reaction of diatomic molecules have been implemented and studied parametrically, utilizing measurement and advanced calculations from the literature as benchmarks. DSMC results have been compared to rotational temperature measurements of nitrogen in finite background jet expansion flows. The influence of the rotational relaxation model, the influx boundary condition, and the outer boundary treatment on the simulation have been investigated.
Download or read book Direct Simulation Monte Carlo Modelling of Surface Catalytic Events in High Enthalpy Rarefied Gas Flows written by Russell Simmons and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Direct Simulation Monte Carlo Modeling for Non Equilibrium Flowfield Applications written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Questions important to modeling of nonequilibrium gas flows are examined. Testing and validation of Direct Simulation Monte Carlo (DSMC) codes have been performed. Several models for vibrational relaxation and chemical reaction of diatomic molecules have been implemented and studied parametrically, utilizing measurement and advanced calculations from the literature as benchmarks. DSMC results have been compared to rotational temperature measurements of nitrogen in finite background jet expansion flows. The influence of the rotational relaxation model, the influx boundary condition, and the outer boundary treatment on the simulation have been investigated.
Download or read book Parallel Direct Simulation Monte Carlo DSMC Methods for Modeling Rarefied Gas Dynamics written by Cheng-Chin Su and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Application of a Direct Simulation Monte Carlo Method to Rarefied Gas Flow Problems written by Eric D. Bermingham and published by . This book was released on 1987 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book MEMS written by Mohamed Gad-el-Hak and published by CRC Press. This book was released on 2005-11-29 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thoroughly revised and updated, the new edition of the best-selling MEMS Handbook is now presented as a three-volume set that offers state-of-the-art coverage of microelectromechanical systems. The first volume, MEMS: Introduction and Fundamentals builds the required background and explores various physical considerations of MEMS. Topics include scaling, simulation models, the basics of control theory, and the physics of materials flow, thin liquid films, and bubble/drop transport. New chapters in this edition address lattice Boltzmann simulations and microscale hydrodynamics. Standing well on its own, this books builds an outstanding foundation for further exploration of MEMS and their applications.
Download or read book Gas Flows in Microsystems written by Lucien Baldas and published by MDPI. This book was released on 2019-10-28 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last two decades have witnessed a rapid development of microelectromechanical systems (MEMS) involving gas microflows in various technical fields. Gas microflows can, for example, be observed in microheat exchangers designed for chemical applications or for cooling of electronic components, in fluidic microactuators developed for active flow control purposes, in micronozzles used for the micropropulsion of nano and picosats, in microgas chromatographs, analyzers or separators, in vacuum generators and in Knudsen micropumps, as well as in some organs-on-a-chip, such as artificial lungs. These flows are rarefied due to the small MEMS dimensions, and the rarefaction can be increased by low-pressure conditions. The flows relate to the slip flow, transition or free molecular regimes and can involve monatomic or polyatomic gases and gas mixtures. Hydrodynamics and heat and mass transfer are strongly impacted by rarefaction effects, and temperature-driven microflows offer new opportunities for designing original MEMS for gas pumping or separation. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel theoretical and numerical models or data, as well as on new experimental results and technics, for improving knowledge on heat and mass transfer in gas microflows. Papers dealing with the development of original gas MEMS are also welcome.
Download or read book Navier Stokes Direct Simulation Monte Carlo Modeling of Small Cold Gas Thruster Nozzle and Plume Flows written by and published by . This book was released on 2002 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt:
