Surface Pressure Fluctuation Generated by a Jet Imaging on a Curved Plate

AIAA Journal ◽  
1977 ◽  
Vol 15 (9) ◽  
pp. 1348-1350 ◽  
Author(s):  
Ho Chi-Ming ◽  
Dennis A. Plocher ◽  
Howard L. Leve
Keyword(s):  
Surface Pressure ◽  
Pressure Fluctuation

Pressure Fluctuations in Rectangular Cavity Flows

1999 ◽  
Vol 15 (3) ◽  
pp. 97-102
Author(s):  
Kung-Ming Chung
Keyword(s):  
Surface Pressure ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Pressure Variation ◽  
Rectangular Cavity ◽  
Front Face ◽  
Cavity Flows ◽  
Rear Face ◽  
Closed Cavity ◽  
Depth Ratio

AbstractExperiments are performed to study the unsteadiness of rectangular cavity flows at Mach 0.325, 0.620 and 0.818. Typical characteristics of mean surface pressure distributions show a slight pressure variation near the front face, a local peak surface pressure ahead of the rear corner and a low pressure at immediate downstream of the cavity. Larger peak pressure and pressure variation near the cavity rear face are observed as the length-to-depth ratio increases. Surface pressure fluctuation distribution shows an increase toward the cavity rear face and reaches a peak value. At further downstream locations, the level of surface pressure fluctuation approaches the value of incoming flow. The amplitude of peak surface pressure fluctuation is associated with length-to-depth ratio and reaches the maximum at length-to-depth ratio of 8.60. This is considered due to intermittent switching between open- and closed-cavity flows. Higher moments of surface pressure signal at immediate downstream of the cavity show a similar trend. More negative skewness coefficient and larger deviation of flatness coefficient indicate the presence of more large negative events, which is mainly corresponding to mass removal process (breath-out phase). This unsteady mass flow is more pronounced at higher Mach number.

Surface pressure fluctuations in a separating turbulent boundary layer

1987 ◽  
Vol 177 ◽  
pp. 167-186 ◽  
Author(s):  
Roger L. Simpson ◽  
M. Ghodbane ◽  
B. E. Mcgrath
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Surface Pressure ◽  
Pressure Fluctuation ◽  
Wave Speed ◽  
Pressure Fluctuations ◽  
Shearing Stress ◽  
Flow Surface ◽  
Attached Flow

Measurements of surface pressure-fluctuation spectra and wave speeds are reported for a well-documented separating turbulent boundary layer. Two sensitive instrumentation microphones were used in a new technique to measure pressure fluctuations through pinhole apertures in the flow surface. Because a portion of the acoustic pressure fluctuations is the same across the nominally two-dimensional turbulent flow, it is possible to decompose the two microphone signals and obtain the turbulent flow contributions to the surface pressure spectra. In addition, data from several earlier attached-flow surface-pressure-fluctuation studies are re-examined and compared with the present measurements.The r.m.s. of the surface pressure fluctuation p′ increases monotonically through the adverse-pressure-gradient attached-flow region and the detached-flow zone. Apparently p′ is proportional to the ratio α of streamwise lengthscale to lengthscales in other directions. For non-equilibrium separating turbulent boundary layers, α is as much as 2.5, causing p′ to be higher than equilibrium layers with lower values of α.The maximum turbulent shearing stress τM appears to be the proper stress on which to scale p′; p′/τM from available data shows much less variation than when p′ is scaled on the wall shear stress. In the present measurements p′/τM increases to the detachment location and decreases downstream. This decrease is apparently due to the rapid movement of the pressure-fluctuation-producing motions away from the wall after the beginning of intermittent backflow. A correlation of the detached-flow data is given that is derived from velocity- and lengthscales of the separated flow.Spectra Φ (ω) for ωδ*/U∞ > 0.001 are presented and correlate well when normalized on the maximum shearing stress τM. At lower frequencies, for the attached flow Φ (ω) ∼ ω−0.7 while Φ(ω) ∼ (ω)−3 at higher frequencies in the strong adverse-pressuregradient region. After the beginning of intermittent backflow, Φ(ω) varies with ω at low frequencies and ω−3 at high frequencies; farther downstream the lower-frequency range varies with ω1.4.The celerity of the surface pressure fluctuations for the attached flow increases with frequency to a maximum; at higher frequencies it decreases and agrees with the semi-logarithmic overlap equation of Panton & Linebarger. After the beginning of the separation process, the wave speed decreases because of the oscillation of the instantaneous wave speed direction. The streamwise coherence decreases drastically after the beginning of flow reversal.

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