Improvement of an LRN two-equation turbulence model reflecting multi-time scales

2015 ◽  
Vol 51 ◽  
pp. 221-228 ◽  
Author(s):  
Yasutaka Nagano ◽  
Hirofumi Hattori
Keyword(s):  
Time Scales ◽  
Turbulence Model

A Two Time Scales Turbulence Model of Turbulent Bubbly Flows

2013 ◽  
Vol 40 (3) ◽  
pp. 185-203
Author(s):  
Dhahri Maher ◽  
Bellakhel Ghazi ◽  
Chahed Jamel
Keyword(s):  
Time Scales ◽  
Turbulence Model ◽  
Bubbly Flows

Toward a Pointwise Turbulence Model for Wall-Bounded and Free Shear Flows

1994 ◽  
Vol 116 (1) ◽  
pp. 72-76 ◽  
Author(s):  
Uriel C. Goldberg
Keyword(s):  
Time Scales ◽  
Turbulence Model ◽  
Shear Flows ◽  
Explicit Knowledge ◽  
Complex Geometries ◽  
Wall Function ◽  
Predictive Capability ◽  
Large Eddy ◽  
Local Distance ◽  
Near Wall

A modified version of the Baldwin-Barth k-ℜ two-equation turbulence model is proposed, in which the near-wall function fμ is based on the ratio of the large eddy and the Kolmogorov time scales. This results in a model applicable to both wall-bounded and free shear flows which, nevertheless, does not require explicit knowledge of local distance to walls, rendering it useful within both structured and unstructured computational frameworks for flow predictions involving complex geometries. The new model’s predictive capability is demonstrated through a number of flow cases.

LVSEM: Past Present and Future

1990 ◽  
Vol 48 (1) ◽  
pp. 364-365
Author(s):  
James B. Pawley
Keyword(s):  
Field Emission ◽  
Line Width ◽  
Time Scales ◽  
Silicon Oxide ◽  
Beam Current ◽  
High Brightness ◽  
High Beam ◽  
Fixed Charges ◽  
Beam Voltage ◽  
Deposited Metal

Past: In 1960 Thornley published the first description of SEM studies carried out at low beam voltage (LVSEM, 1-5 kV). The aim was to reduce charging on insulators but increased contrast and difficulties with low beam current and frozen biological specimens were also noted. These disadvantages prevented widespread use of LVSEM except by a few enthusiasts such as Boyde. An exception was its use in connection with studies in which biological specimens were dissected in the SEM as this process destroyed the conducting films and produced charging unless LVSEM was used.In the 1980’s field emission (FE) SEM’s came into more common use. The high brightness and smaller energy spread characteristic of the FE-SEM’s greatly reduced the practical resolution penalty associated with LVSEM and the number of investigators taking advantage of the technique rapidly expanded; led by those studying semiconductors. In semiconductor research, the SEM is used to measure the line-width of the deposited metal conductors and of the features of the photo-resist used to form them. In addition, the SEM is used to measure the surface potentials of operating circuits with sub-micrometer resolution and on pico-second time scales. Because high beam voltages destroy semiconductors by injecting fixed charges into silicon oxide insulators, these studies must be performed using LVSEM where the beam does not penetrate so far.

SPECTRAL DIFFUSION AND RELAXATION OF PHOTOCHEMICAL HOLES ON LOGARITHMIC TIME SCALES

1985 ◽  
Vol 46 (C7) ◽  
pp. C7-357-C7-361 ◽  
Author(s):  
J. Friedrich ◽  
D. Haarer
Keyword(s):  
Time Scales ◽  
Spectral Diffusion
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