30 research outputs found
Seasonal Abundance of the Bean Bug, Riptortus pedestris (Heteroptera: Alydidae) in Some Leguminous Plants
Effects of Adding Reducing Agent to the Nutrient Solution Containing Chloramine on the Occurrence of Root Browning and Growth in Lettuce
Dynamic Behavior of Premixed Flames Propagating in Non-Uniform Velocity Fields —Assessment of Intrinsic Instability in Turbulent Combustion—
Acoustic Receptivity of a Blasius Boundary Layer with 2-D and Oblique Surface Waviness
An experimental investigation was conducted to examine acoustic receptivity and subsequent boundary-layer instability evolution for a Blasius boundary layer formed on a flat plate in the presence of two-dimensional (2-D) and oblique (3-D) surface waviness. The effect of the non-localized surface roughness geometry and acoustic wave amplitude on the receptivity process was explored. The surface roughness had a well defined wavenumber spectrum with fundamental wavenumber k (sub w). A planar downstream traveling acoustic wave was created to temporally excite the flow near the resonance frequency of an unstable eigenmode corresponding to k (sub ts) = k (sub w). The range of acoustic forcing levels, epsilon, and roughness heights, DELTA h, examined resulted in a linear dependence of receptivity coefficients; however, the larger values of the forcing combination epsilon dot DELTA h resulted in subsequent nonlinear development of the Tollmien-Schlichting (T-S) wave. This study provided the first experimental evidence of a marked increase in the receptivity coefficient with increasing obliqueness of the surface waviness in excellent agreement with theory. Detuning of the 2-D and oblique disturbances was investigated by varying the streamwise wall-roughness wavenumber a,, and measuring the T-S response. For the configuration where laminar-to-turbulent breakdown occurred, the breakdown process was found to be dominated by energy at the fundamental and harmonic frequencies, indicative of K-type breakdown