scholarly journals Influence of freestream turbulence on the flow over a wall roughness

2021 ◽  
Vol 6 (6) ◽  
Author(s):  
M. A. Bucci ◽  
S. Cherubini ◽  
J.-Ch. Loiseau ◽  
J.-Ch. Robinet
Keyword(s):  
Wall Roughness ◽  
Freestream Turbulence

The Dependence of Demolding Characteristics on Side Wall Roughness of Mold in Thermal Imprint

2008 ◽  
Vol 128 (8) ◽  
pp. 325-330 ◽  
Author(s):  
Hiroaki Kawata ◽  
Junya Ishihara ◽  
Masayo Kayama ◽  
Masaaki Yasuda ◽  
Yoshihiko Hirai
Keyword(s):  
Side Wall ◽  
Wall Roughness

Wall Roughness Effects on Combustion Development in Confined Supersonic Flow

2021 ◽  
Vol 37 (1) ◽  
pp. 151-166
Author(s):  
Guillaume Pelletier ◽  
Marc Ferrier ◽  
Axel Vincent-Randonnier ◽  
Vladimir Sabelnikov ◽  
Arnaud Mura
Keyword(s):  
Supersonic Flow ◽  
Wall Roughness ◽  
Roughness Effects

Synthetic freestream turbulence generation at an inflow boundary condition

2021 ◽  
Author(s):  
Gabriel B. Goodwin ◽  
Christian L. Bachman ◽  
Ryan F. Johnson ◽  
David A. Kessler
Keyword(s):  
Boundary Condition ◽  
Freestream Turbulence ◽  
Inflow Boundary Condition ◽  
Turbulence Generation

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

scholarly journals Investigation of Side Wall Roughness Effect on Optical Losses in a Multimode Si3N4 Waveguide Formed on a Quartz Substrate

Photonics ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 104
Author(s):  
Anastasia Yakuhina ◽  
Alexey Kadochkin ◽  
Vyacheslav Svetukhin ◽  
Dmitry Gorelov ◽  
Sergey Generalov ◽  
...  
Keyword(s):  
Optical Waveguides ◽  
Quartz Substrate ◽  
Side Wall ◽  
Wall Roughness ◽  
Roughness Parameters ◽  
Optical Losses ◽  
Waveguide Width ◽  
Integration Density ◽  
Frequency Domain Reflectometry ◽  
Multimode Operation

This article presents the results of the study of the influence of the most significant parameters of the side wall roughness of an ultra-thin silicon nitride lightguide layer of multimode integrated optical waveguides with widths of 3 and 8 microns. The choice of the waveguide width was made due to the need to provide multimode operation for telecommunication wavelengths, which is necessary to ensure high integration density. Scattering in waveguide structures was measured by optical frequency domain reflectometry (OFDR) of a backscattering reflectometer. The finite difference time domain method (FDTD) was used to study the effect of roughness parameters on optical losses in fabricated waveguides, the roughness parameters that most strongly affect optical scattering were determined, and methods of its significant reduction were specified. The prospects for implementing such structures on a quartz substrate are justified.

The Effect of Freestream Turbulence on Film Cooling Adiabatic Effectiveness

2002 ◽  
Author(s):  
James E. Mayhew ◽  
James W. Baughn ◽  
Aaron R. Byerley
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Main Flow ◽  
Freestream Turbulence ◽  
Coverage Area ◽  
Liquid Crystal Thermography ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness ◽  
Cooling Air

The film-cooling performance of a flat plate in the presence of low and high freestream turbulence is investigated using liquid crystal thermography. High-resolution distributions of the adiabatic effectiveness are determined over the film-cooled surface of the flat plate using the hue method and image processing. Three blowing rates are investigated for a model with three straight holes spaced three diameters apart, with density ratio near unity. High freestream turbulence is shown to increase the area-averaged effectiveness at high blowing rates, but decrease it at low blowing rates. At low blowing ratio, freestream turbulence clearly reduces the coverage area of the cooling air due to increased mixing with the main flow. However, at high blowing ratio, when much of the jet has lifted off in the low turbulence case, high freestream turbulence turns its increased mixing into an asset, entraining some of the coolant that penetrates into the main flow and mixing it with the air near the surface.

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