Analyzing Vortex Dynamics in the Laminar Separation Bubble vis Surface Pressure Measurements

2015 ◽  
Author(s):  
Andrew Lambert ◽  
Serhiy V. Yarusevych
Keyword(s):  
Surface Pressure ◽  
Vortex Dynamics ◽  
Separation Bubble ◽  
Laminar Separation Bubble ◽  
Pressure Measurements ◽  
Laminar Separation

Characterization of Vortex Dynamics in a Laminar Separation Bubble

AIAA Journal ◽  
2017 ◽  
Vol 55 (8) ◽  
pp. 2664-2675 ◽  
Author(s):  
Andrew R. Lambert ◽  
Serhiy Yarusevych
Keyword(s):  
Vortex Dynamics ◽  
Separation Bubble ◽  
Laminar Separation Bubble ◽  
Laminar Separation

Investigation of laminar separation bubble over a supercritical airfoil in an incompressible flow

2021 ◽  
pp. 095440622110207
Author(s):  
Massoud Tatar ◽  
Mehran Masdari ◽  
Mojtaba Tahani
Keyword(s):  
Boundary Layer ◽  
Surface Pressure ◽  
Separation Bubble ◽  
Second Derivative ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Supercritical Airfoil ◽  
Time Frequency ◽  
Transition Points ◽  
Hot Film

Supercritical airfoils have an unknown behavior at incompressible flow regime and Reynolds numbers lower than those related to their design point at transonic condition. In this work, boundary layer transition is studied over a supercritical airfoil by means of hot-film and pressure measurements completed with numerical simulations. The experiments are performed at chord-based Reynolds number of [Formula: see text]and Mach number of [Formula: see text] at different angles of attack. Hot-film measurement over the upper surface of the supercritical airfoil is carried out and the transition points are computed using the standard deviation of the signals. The upper surface pressure is also recorded and a peak in its second derivative is presented as the transition point generated by the laminar separation bubble mechanism. Moreover, an appropriate time-frequency analysis is applied to the hot-film signals to get an insight into the spectral content and development of the transitional boundary layer structures. On the other hand, two numerical codes are employed and the transition points obtained from numerical simulations are compared with the experimental outcomes. Results express a rapid change of the bubble position over the upper surface, as the angle of attack is increased to the value of [Formula: see text]. Laminar separation bubble is observed in the surface pressure distribution data and is well identified using its second derivative along the streamwise direction. The spectral characteristics of the boundary layer are satisfactorily explored including the streamwise fluctuations within the laminar flow, intermittent behavior of the transitional zone and the wide range of the spectrum in turbulent flow, thanks to the time-frequency analysis. A promising agreement is observed between the transition points computed by both the numerical and experimental studies and confirms the accuracy of findings achieved by the second derivative of surface pressure data, hot-film measurements and the reliability of the employed numerical transition models for optimization studies.

Structure and dynamics of a laminar separation bubble near a wingtip

2021 ◽  
Vol 929 ◽  
Author(s):  
Connor E. Toppings ◽  
Serhiy Yarusevych
Keyword(s):  
Vortex Shedding ◽  
Vortex Dynamics ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Surface Flow ◽  
Laminar Separation Bubble ◽  
Two Dimensional ◽  
Flow Topology ◽  
Laminar Separation ◽  
The Mean

The three-dimensional flow topology of a laminar separation bubble forming on the suction surface of a semispan wing with an aspect ratio of $2.5$ and NACA 0018 airfoil section is characterised experimentally using surface pressure measurements and particle image velocimetry at a chord Reynolds number of $125\ 000$ . In the inboard region of the wing, the separation bubble is essentially two-dimensional, and the transition process in the separated shear layer leads to periodic vortex shedding, which dominates the bubble dynamics, similar to two-dimensional separation bubbles. However, progressive spanwise changes in the mean structure and vortex dynamics occur near the wingtip, leading to an open separation and eventual suppression of the bubble. In the immediate proximity of the wingtip, the boundary layer remains attached, no vortex shedding occurs and the flow remains laminar, terminating separation bubble formation. Despite variations in the mean separation bubble topology and vortex dynamics along the span, the fundamental shedding characteristics remain nearly invariant across the portion of the wing where vortex shedding occurs, and the flow appears to lock onto a common instability mode across the span, leading to minimal changes in the mean bubble characteristics despite notable changes in the effective angle of attack along the span. A comparison with available surface flow visualisations from previous studies indicates that the observed changes to the mean bubble footprint along the span of the wing are similar across different geometries and flow characteristics, suggesting similarities in the three-dimensional bubble topology and dynamics on finite wings.

Mechanisms of surface pressure distribution within a laminar separation bubble at different Reynolds numbers

2015 ◽  
Vol 27 (2) ◽  
pp. 023602 ◽  
Author(s):  
Donghwi Lee ◽  
Soshi Kawai ◽  
Taku Nonomura ◽  
Masayuki Anyoji ◽  
Hikaru Aono ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Surface Pressure ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Surface Pressure Distribution

Loss Production Mechanisms in a Laminar Separation Bubble

2012 ◽  
Vol 89 (4) ◽  
pp. 547-562 ◽  
Author(s):  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Separation Bubble ◽  
Laminar Separation Bubble ◽  
Laminar Separation ◽  
Production Mechanisms
Sign in / Sign up

Export Citation Format

Share Document