Features of the wall pressure field associated with turbulent spots in a laminar boundary layer

1980 ◽  
Vol 68 (S1) ◽  
pp. S106-S106
Author(s):  
Fred C. DeMetz
Keyword(s):  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Pressure Field ◽  
Wall Pressure ◽  
Turbulent Spots

Decay of fluctuating wall-pressure field of Mach 5 turbulent boundary layer

AIAA Journal ◽  
1999 ◽  
Vol 37 ◽  
pp. 1088-1096
Author(s):  
O. H. Unalmis ◽  
D. S. Dolling
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Field ◽  
Wall Pressure

Wall-pressure fluctuations beneath turbulent boundary layers on a flat plate and a cylinder

1970 ◽  
Vol 41 (1) ◽  
pp. 47-80 ◽  
Author(s):  
W. W. Willmarth ◽  
C. S. Yang
Keyword(s):  
Boundary Layer ◽  
Pressure Field ◽  
Time Correlation ◽  
Space Time ◽  
Wall Pressure ◽  
Plane Boundary ◽  
Wall Pressure Fluctuations ◽  
Turbulent Pressure ◽  
Transverse Scale ◽  
Convection Speed

Measurements of the turbulent pressure field on the outer surface of a 3 in. diameter cylinder aligned with the flow were made at a point approximately 24 ft. downstream of the origin of the turbulent boundary layer in an air stream of 145 ft./sec. The boundary-layer thickness was 2·78 in. and the Reynolds number based on momentum thickness was 2·62 × 104. The wall-pressure measurements were made with pressure transducers constructed from 0·06 in. diameter lead–zirconate–titanate disks mounted flush with the wall. The measurements including root-mean-square, power spectrum, and correlations of the wall pressure are compared with the existing experimental results for the turbulent pressure field beneath a plane boundary layer. The streamwise convection speed deduced from longitudinal space-time correlation measurements was almost identical to that obtained in the plane boundary layer. The rate of decay of the maxima of the space-time correlation of the pressure produced by the convected eddies was double that in a plane boundary layer. The longitudinal and transverse scales of the pressure correlation were approximately equal (in a plane boundary layer the transverse scale is larger than longitudinal scale) and were one-half or less than the longitudinal scale in the plane boundary layer. It is concluded that the effect of the transverse curvature of the wall is an overall reduction in size of pressure-producing eddies. The reduction in transverse scale of the larger eddies is greater than that of the smaller eddies. In general, the smaller eddies decay more rapidly and produce greater spectral densities at high frequencies owing to the unchanged convection speed.

Investigation of transition to turbulence using white-noise excitation and local analysis techniques

1997 ◽  
Vol 348 ◽  
pp. 29-83 ◽  
Author(s):  
F. N. SHAIKH
Keyword(s):  
Boundary Layer ◽  
White Noise ◽  
Laminar Boundary Layer ◽  
Nonlinear Flow ◽  
Local Analysis ◽  
Hot Wire ◽  
Turbulent Spots ◽  
Analysis Techniques ◽  
White Noise Excitation ◽  
Highly Nonlinear

Weak free-stream turbulence excites modulated Tollmien–Schlichting (T–S) waves in a laminar boundary layer that grow in magnitude with downstream distance and ultimately lead to the formation of turbulent spots and then fully turbulent flow. Hot-wire experiments have indicated that the development of localized large-amplitude ‘events’ in the velocity records are the essential precursor to the eventual formation of turbulent spots in the flow field. Traditional global Fourier techniques are unable to resolve the localized nature of these events and hence provide little useful information concerning the physical processes responsible for this breakdown process.This investigation used sequences of computer-generated deterministic white noise to excite a laminar boundary layer via a loudspeaker embedded in a flat-plate model. This form of excitation generated the modulated disturbance waves of interest a short distance downstream from the source in a repeatable and deterministic manner. Further downstream the pattern of flow breakdown and subsequent generation of turbulent spots was similar to that observed in naturally excited situations. By repeatedly exciting the boundary layer with a single white-noise sequence it was possible to examine the highly nonlinear stages of ‘event’ development and breakdown with a single hot-wire probe.Two local analysis techniques, the wavelet transform (WT) and singular spectrum analysis (SSA), were used in conjunction with the white-noise excitation technique to examine the highly nonlinear flow mechanisms responsible for the localized formation of events that lead to the eventual breakdown to turbulence.

K-1404 Visualization experiment on mutual Interaction between turbulent spots in a laminar boundary layer

2001 ◽  
Vol II.01.1 (0) ◽  
pp. 211-212
Author(s):  
Ryuichi AOYAMA ◽  
Hideharu MAKITA ◽  
Nobumasa SEKISHITA ◽  
Naoyuki TUCHIYA
Keyword(s):  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Mutual Interaction ◽  
Turbulent Spots ◽  
Visualization Experiment

Study on the Fluctuating Wall Pressure Field and the Coherent Structure in the Turbulent Boundary Layer

2004 ◽  
Vol 2004.53 (0) ◽  
pp. 303-304
Author(s):  
Yasuhiko SAKAI ◽  
Takeo OOTSUKA ◽  
Takehiro KUSHIDA ◽  
Hironao YOKOI
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Coherent Structure ◽  
Pressure Field ◽  
Wall Pressure
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