Unified Model for Ballistic Transport and Gas-Solid Reactions in Features

1990 ◽  
Vol 204 ◽  
Author(s):  
T. S. Cale ◽  
G. B. Raupp ◽  
T. H. Gandy
Keyword(s):  
Surface Diffusion ◽  
Ballistic Transport ◽  
Three Dimensional ◽  
Low Pressure ◽  
Unified Model ◽  
Governing Equations ◽  
Adsorbed Species ◽  
Molecular Velocity ◽  
Patterned Wafers

ABSTRACTThe three dimensional equations which govern free molecular or ballistic transport and heterogeneous gas-solid reactions in features on patterned wafers during low pressure processing are reviewed. The governing equations specific to long rectangular trenches are extended to include nonuniform molecular velocity distributions in the source volume above the wafer as well as surface diffusion of adsorbed species or intermediates. Introduction of reaction stoichiometries and kinetic expressions for general deposition and etch reactions completes the specification of the problem. Local generalized sticking factors arise in the process of nondimensionalizing the governing equations.

Propagation and Reflection of Plane Waves in a Rotating Magneto-Elastic Fibre-Reinforced Semi Space with Surface Stress

2020 ◽  
Vol 22 (4) ◽  
pp. 939-958
Author(s):  
Indrajit Roy ◽  
D. P. Acharya ◽  
Sourav Acharya
Keyword(s):  
Surface Stress ◽  
Incident Angle ◽  
Plane Waves ◽  
Three Dimensional ◽  
Elastic Fibre ◽  
Amplitude Ratios ◽  
Governing Equations ◽  
Rotation Surface ◽  
Wave Velocities ◽  
Magnetic Field Rotation

AbstractThe present paper investigates the propagation of quasi longitudinal (qLD) and quasi transverse (qTD) waves in a magneto elastic fibre-reinforced rotating semi-infinite medium. Reflections of waves from the flat boundary with surface stress have been studied in details. The governing equations have been used to obtain the polynomial characteristic equation from which qLD and qTD wave velocities are found. It is observed that both the wave velocities depend upon the incident angle. After imposing the appropriate boundary conditions including surface stress the resultant amplitude ratios for the total displacements have been obtained. Numerically simulated results have been depicted graphically by displaying two and three dimensional graphs to highlight the influence of magnetic field, rotation, surface stress and fibre-reinforcing nature of the material medium on the propagation and reflection of plane waves.

scholarly journals Investigation of Pressure Oscillation and Cavitation Characteristics for Submerged Self-Resonating Waterjet

2021 ◽  
Vol 11 (15) ◽  
pp. 6972
Author(s):  
Lihua Cui ◽  
Fei Ma ◽  
Tengfei Cai
Keyword(s):  
Sudden Change ◽  
Three Dimensional ◽  
Pressure Oscillation ◽  
Experimental Tests ◽  
Low Pressure ◽  
The Self ◽  
Two Phase ◽  
Cavitation Phenomenon ◽  
Pressure Zone ◽  
Unsteady Characteristics

The cavitation phenomenon of the self-resonating waterjet for the modulation of erosion characteristics is investigated in this paper. A three-dimensional computational fluid dynamics (CFD) model was developed to analyze the unsteady characteristics of the self-resonating jet. The numerical model employs the mixture two-phase model, coupling the realizable turbulence model and Schnerr–Sauer cavitation model. Collected data from experimental tests were used to validate the model. Results of numerical simulations and experimental data frequency bands obtained by the Fast Fourier transform (FFT) method were in very good agreement. For better understanding the physical phenomena, the velocity, the pressure distributions, and the cavitation characteristics were investigated. The obtained results show that the sudden change of the flow velocity at the outlet of the nozzle leads to the forms of the low-pressure zone. When the pressure at the low-pressure zone is lower than the vapor pressure, the cavitation occurs. The flow field structure of the waterjet can be directly perceived through simulation, which can provide theoretical support for realizing the modulation of the erosion characteristics, optimizing nozzle structure.

Design of an Intermediate Turbine Duct Downstream of a High Pressure Turbine

2016 ◽  
Author(s):  
Chaoshan Hou ◽  
Hu Wu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Low Pressure ◽  
Aerodynamic Load ◽  
Duct Flow ◽  
Original Design ◽  
High Pressure Turbine ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Inlet Conditions

The flow leaving the high pressure turbine should be guided to the low pressure turbine by an annular diffuser, which is called as the intermediate turbine duct. Flow separation, which would result in secondary flow and cause great flow loss, is easily induced by the negative pressure gradient inside the duct. And such non-uniform flow field would also affect the inlet conditions of the low pressure turbine, resulting in efficiency reduction of low pressure turbine. Highly efficient intermediate turbine duct cannot be designed without considering the effects of the rotating row of the high pressure turbine. A typical turbine model is simulated by commercial computational fluid dynamics method. This model is used to validate the accuracy and reliability of the selected numerical method by comparing the numerical results with the experimental results. An intermediate turbine duct with eight struts has been designed initially downstream of an existing high pressure turbine. On the basis of the original design, the main purpose of this paper is to reduce the net aerodynamic load on the strut surface and thus minimize the overall duct loss. Full three-dimensional inverse method is applied to the redesign of the struts. It is revealed that the duct with new struts after inverse design has an improved performance as compared with the original one.

Effects of moving lid direction on mixed convection and entropy generation in a cubical cavity with longitudinal triangular fin insertion

2017 ◽  
Vol 27 (4) ◽  
pp. 839-860 ◽  
Author(s):  
Lioua Kolsi ◽  
Hakan F. Öztop ◽  
Nidal Abu-Hamdeh ◽  
Borjini Mohamad Naceur ◽  
Habib Ben Assia
Keyword(s):  
Mixed Convection ◽  
Entropy Generation ◽  
Three Dimensional ◽  
Thermal Conductivity Ratio ◽  
Governing Equations ◽  
Content Type ◽  
Driven Cavity ◽  
Triangular Fin ◽  
Cubical Cavity ◽  
3D Problem

Purpose The main purpose of this work is to arrive at a three-dimensional (3D) numerical solution on mixed convection in a cubic cavity with a longitudinally located triangular fin in different sides. Design/methodology/approach The 3D governing equations are solved via finite volume technique by writing a code in FORTRAN platform. The governing parameters are chosen as Richardson number, 0.01 ≤ Ri ≤ 10 and thermal conductivity ratio 0.01 ≤ Rc ≤ 100 for fixed parameters of Pr = 0.7 and Re = 100. Two cases are considered for a lid-driven wall from left to right (V+) and right to left (V−). Findings It is observed that entropy generation due to heat transfer becomes dominant onto entropy generation because of fluid friction. The most important parameter is the direction of the moving lid, and lower values are obtained when the lid moves from right to left. Originality The main originality of this work is to arrive at a solution of a 3D problem of mixed convection and entropy generation for lid-driven cavity with conductive triangular fin attachments.

scholarly journals Numerical Calculation of Flow for Cascade With Tip Clearance

1994 ◽  
Author(s):  
Shimpei Mizuki ◽  
Hoshio Tsujita
Keyword(s):  
Three Dimensional ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Governing Equations ◽  
Tensor Form ◽  
Pressure Surface ◽  
Rear Part ◽  
Blade Tip ◽  
Flow Through ◽  
Blade Tip Geometry

Three-dimensional incompressible turbulent flow within a linear turbine cascade with tip clearance is analyzed numerically. The governing equations involving the standard k-ε model are solved in the physical component tensor form with a boundary-fitted coordinate system. In the analysis, the blade tip geometry is treated accurately in order to predict the flow through the tip clearance in detail when the blades have large thicknesses. Although the number of grids employed in the present study is not enough because of the limitation of computer storage memory, the computed results show good agreements with the experimental results. Moreover, the results clearly exhibit the locus of minimum pressure on the rear part of the pressure surface at the blade tip.

Review of Three Dimensional Dynamic Analyses of Circular Cylinders and Cylindrical Shells

1994 ◽  
Vol 47 (10) ◽  
pp. 501-516 ◽  
Author(s):  
Kostas P. Soldatos
Keyword(s):  
Cylindrical Shells ◽  
Three Dimensional ◽  
Circular Cylinders ◽  
Accurate Information ◽  
Two Dimensional ◽  
Governing Equations ◽  
Complicated Form ◽  
Dynamic Analyses ◽  
Cylindrical Panels ◽  
Elastic Cylinders

There is an increasing usefulness of exact three-dimensional analyses of elastic cylinders and cylindrical shells in composite materials applications. Such analyses are considered as benchmarks for the range of applicability of corresponding studies based on two-dimensional and/or finite element modeling. Moreover, they provide valuable, accurate information in cases that corresponding predictions based on that later kind of approximate modeling is not satisfactory. Due to the complicated form of the governing equations of elasticity, such three-dimensional analyses are comparatively rare in the literature. There is therefore a need for further developments in that area. A survey of the literature dealing with three-dimensional dynamic analyses of cylinders and open cylindrical panels will serve towards such developments. This paper presents such a survey within the framework of linear elasticity.

Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine

2014 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Arne Graßmann
Keyword(s):  
Steam Turbine ◽  
Design Process ◽  
Energy Demand ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Pressure Steam ◽  
Last Stage

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.

The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPE

2007 ◽  
Vol 4 (7) ◽  
pp. 2506-2509 ◽  
Author(s):  
Tetuso Narita ◽  
Yoshio Honda ◽  
Masahito Yamaguchi ◽  
Nobuhiko Sawaki
Keyword(s):  
Surface Diffusion ◽  
Low Pressure ◽  
Facet Structure
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