scholarly journals Surface chemistry models for GaAs epitaxial growth and hydride cracking using reacting flow simulations

2021 ◽  
Vol 130 (11) ◽  
pp. 115702
Author(s):  
Malik Hassanaly ◽  
Hariswaran Sitaraman ◽  
Kevin L. Schulte ◽  
Aaron J. Ptak ◽  
John Simon ◽  
...  
Keyword(s):  
Surface Chemistry ◽  
Epitaxial Growth ◽  
Reacting Flow ◽  
Flow Simulations ◽  
Hydride Cracking

A step towards 'shape-shifting' algorithms - Reacting flow simulations using generalized grids

2001 ◽  
Author(s):  
Edward Luke ◽  
Xiao-Ling Tong ◽  
Junxiao Wu ◽  
Lin Tang ◽  
Pasquale Cinnella
Keyword(s):  
Reacting Flow ◽  
Flow Simulations

Numerical Studies on Trapped-Vortex Concepts for Stable Combustion

1998 ◽  
Vol 120 (1) ◽  
pp. 60-68 ◽  
Author(s):  
V. R. Katta ◽  
W. M. Roquemore
Keyword(s):  
Drag Coefficient ◽  
Reacting Flow ◽  
Flow Conditions ◽  
Third Order ◽  
Cold Flow ◽  
Flow Simulations ◽  
Numerical Studies ◽  
Dynamic Flows ◽  
Experimental Findings ◽  
Trapped Vortex

Spatially locked vortices in the cavities of a combustor aid in stabilizing the flames. On the other hand, these stationary vortices also restrict the entrainment of the main air into the cavity. For obtaining good performance characteristics in a trapped-vortex combustor, a sufficient amount of fuel and air must be injected directly into the cavity. This paper describes a numerical investigation performed to understand better the entrainment and residence-time characteristics of cavity flows for different cavity and spindle sizes. A third-order-accurate time-dependent Computational Fluid Dynamics with Chemistry (CFDC) code was used for simulating the dynamic flows associated with forebody-spindle-disk geometry. It was found from the nonreacting flow simulations that the drag coefficient decreases with cavity length and that an optimum size exists for achieving a minimum value. These observations support the earlier experimental findings of Little and Whipkey (1979). At the optimum disk location, the vortices inside the cavity and behind the disk are spatially locked. It was also found that for cavity sizes slightly larger than the optimum, even though the vortices are spatially locked, the drag coefficient increases significantly. Entrainment of the main flow was observed to be greater into the smaller-than-optimum cavities. The reacting-flow calculations indicate that the dynamic vortices developed inside the cavity with the injection of fuel and air do not shed, even though the cavity size was determined based on cold-flow conditions.

The In Situ Adaptive Tabulation (ISAT) Algorithm for Reacting Flow Computations With Complex Surface Chemistry

2013 ◽  
Author(s):  
Sandip Mazumder ◽  
Ankan Kumar
Keyword(s):  
Steady State ◽  
Surface Chemistry ◽  
Catalytic Combustion ◽  
Catalytic Converter ◽  
Differential Algebraic Equations ◽  
Heterogeneous Reactions ◽  
Reacting Flow ◽  
In Situ Adaptive Tabulation ◽  
The Impact

The In Situ Adaptive Tabulation (ISAT) procedure, originally developed for the efficient computation of homogeneous reactions in chemically reacting flows, is adapted and demonstrated for reacting flow computations with complex heterogeneous (or surface) reactions. The treatment of heterogeneous reactions within a reacting flow calculation requires solution of a set of nonlinear differential algebraic equations at boundary faces/nodes, as opposed to the solution of an initial value problem for which the original ISAT procedure was developed. The modified ISAT algorithm, referred to as ISAT-S, is coupled to a three-dimensional unstructured reacting flow solver, and strategies for maximizing efficiency without hampering accuracy and convergence are developed. These include use of multiple binary tables, use of dynamic tolerance values to control errors, and periodic deletion and/or re-creation of the binary tables. The new procedure is demonstrated for steady-state catalytic combustion of a methane-air mixture on platinum using a 24-step reaction mechanism with 19 species, and for steady-state three-way catalytic conversion using a 61-step mechanism with 34 species. Both reaction mechanisms are first tested in simple 3D channel geometry with reacting walls, and the impact of various ISAT parameters is investigated. As a final step, the catalytic combustion mechanism is demonstrated in a laboratory-scale monolithic catalytic converter geometry with 57 channels discretized using 354,300 control volumes (4.6 million unknowns). For all of the cases considered, the reduction in the time taken to perform surface chemistry calculations alone was found to be a factor of 5–11.

Studies of Si Surface Chemistry and Epitaxy Using Scanning Tunneling Microscopy and Spectroscopy

1988 ◽  
Vol 131 ◽  
Author(s):  
Phaedon Avouris ◽  
Robert Wolkow
Keyword(s):  
Electronic Structure ◽  
Spatial Distribution ◽  
Surface Chemistry ◽  
Scanning Tunneling Microscopy ◽  
Epitaxial Growth ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy

ABSTRACTWe apply scanning tunneling microscopy (STM) and spectroscopy (STS) to study the reaction of NH3 with Si(111)-(7×7), and the epitaxial growth of CaF2 on Si(11). By a combination of topographs and atom-resolved spectra we can follow the spatial distribution of the reaction and changes in electronic structure with atomic resolution. We find that there are strong site-selectivities for the NH3 reaction on the 7×7 surface. We also observe the initial stages of the CaF2 deposition and even are able to image insulating multi-layer CaF2 films.

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