scholarly journals Experimental and Computational Study of Two-Dimensional Roughness Effects on the Instability of the Flat Plate Boundary Layer.

1998 ◽  
Vol 41 (1) ◽  
pp. 52-59
Author(s):  
Mohammad ali ARDEKANI ◽  
Hirosuke MUNAKATA ◽  
Kiyoaki ONO
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Computational Study ◽  
Plate Boundary ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Flat Plate Boundary Layer

scholarly journals Modeling of Laminar-Turbulent Transition in Boundary Layers and Rough Turbine Blades

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Liang Wei ◽  
Xuan Ge ◽  
Jacob George ◽  
Paul Durbin
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Skin Friction ◽  
Current Model ◽  
Turbine Blades ◽  
Great Influence ◽  
Plate Boundary ◽  
Freestream Turbulence ◽  
Roughness Effects ◽  
Flat Plate Boundary Layer

A local, intermittency-function-based transition model was developed for the prediction of laminar-turbulent transitional flows with freestream turbulence intensity Tu at low (Tu < 1%), moderate (1% < Tu < 3%), and high Tu > 3% levels, and roughness effects in a broad range of industrial applications such as turbine and helicopter rotor blades, and in nature. There are many mechanisms (natural or bypass) that lead to transition. Surface roughness due to harsh working conditions could have great influence on transition. Accurately predicting both the onset location and length of transition has been persistently difficult. The current model is coupled with the k–ω Reynolds-averaged Navier–Stokes (RANS) model, that can be used for general computational fluid dynamics (CFD) purpose. It was validated on the ERCOFTAC experimental zero-pressure-gradient smooth flat plate boundary layer with both low and high leading-edge freestream turbulence intensities. Skin friction profiles agree well with the experimental data. The model was then tested on ERCOFTAC experimental flat plate boundary layer with favorable/adverse pressure gradients cases, periodic wakes, and flows over Stripf's turbine blades with roughness from hydraulically smooth to fully rough. The predicted skin friction and heat transfer properties by the current model agree well with the published experimental and numerical data.

scholarly journals Oblique route to turbulence

2011 ◽  
Vol 674 ◽  
pp. 1-4
Author(s):  
MUJEEB R. MALIK
Keyword(s):  
Boundary Layer ◽  
Numerical Simulations ◽  
Flat Plate ◽  
Boundary Layers ◽  
Plate Boundary ◽  
Direct Numerical Simulations ◽  
Two Dimensional ◽  
Mach 3 ◽  
Transition Scenario ◽  
Flat Plate Boundary Layer

Direct numerical simulations have been performed by Mayer, Von Terzi & Fasel (J. Fluid Mech., this issue, vol. 674, 2011, pp. 5–42) to demonstrate that oblique-mode breakdown leads to fully turbulent flow for a Mach 3 flat-plate boundary layer. Since very low level of initial disturbances is required for this transition scenario, oblique-mode breakdown is the most potent mechanism for transition in two-dimensional supersonic boundary layers in low-disturbance environments relevant to flight.

Disturbance evolution in a Mach 4.8 boundary layer with two-dimensional roughness-induced separation and shock

2010 ◽  
Vol 648 ◽  
pp. 435-469 ◽  
Author(s):  
OLAF MARXEN ◽  
GIANLUCA IACCARINO ◽  
ERIC S. G. SHAQFEH
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Stokes Equations ◽  
Roughness Element ◽  
Plate Boundary ◽  
Destructive Interference ◽  
Two Dimensional ◽  
Limited Bandwidth ◽  
Additional Perturbation ◽  
Flat Plate Boundary Layer

A numerical investigation of the disturbance amplification in a Mach 4.8 flat-plate boundary layer with a localized two-dimensional roughness element is presented. The height of the roughness is varied and reaches up to approximately 70% of the boundary-layer thickness. Simulations are based on a time-accurate integration of the compressible Navier–Stokes equations, with a small disturbance of fixed frequency being triggered via blowing and suction upstream of the roughness element. The roughness element considerably alters the instability of the boundary layer, leading to increased amplification or damping of a modal wave depending on the frequency range. The roughness is also the source of an additional perturbation. Even though this additional mode is stable, the interaction with the unstable mode in the form of constructive and destructive interference behind the roughness element leads to a beating and therefore transiently increased disturbance amplitude. Far downstream of the roughness, the amplification rate of a flat-plate boundary layer is recovered. Overall, the two-dimensional roughness element behaves as disturbance amplifier with a limited bandwidth capable of filtering a range of frequencies and strongly amplifying only a selected range.

scholarly journals Development of second-mode instability in a Mach 6 flat plate boundary layer with two-dimensional roughness

2015 ◽  
Vol 27 (6) ◽  
pp. 064105 ◽  
Author(s):  
Qing Tang ◽  
Yiding Zhu ◽  
Xi Chen ◽  
Cunbiao Lee
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Plate Boundary ◽  
Two Dimensional ◽  
Mode Instability ◽  
Second Mode ◽  
Flat Plate Boundary Layer

Global two-dimensional stability measures of the flat plate boundary-layer flow

2008 ◽  
Vol 27 (5) ◽  
pp. 501-513 ◽  
Author(s):  
Espen Åkervik ◽  
Uwe Ehrenstein ◽  
François Gallaire ◽  
Dan S. Henningson
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Dimensional Stability ◽  
Boundary Layer Flow ◽  
Plate Boundary ◽  
Two Dimensional ◽  
Layer Flow ◽  
Flat Plate Boundary Layer
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