Surface Roughness: Its Effects on the Performance of a Two-Dimensional Compressor Cascade

The effects of surface roughness on the losses in the flow through a two-dimensional compressor cascade were studied. The cascade consisted of 7 NACA 65-A506 airfoils with 2-in. chords and aspect ratio of 1. The blades were mounted with a stagger angle of 16 deg, an angle of attack of 15 deg and a s...

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Bibliographic Details
Main Author: Poulin,J R
Format: Report
Language:English
Subjects:
Airfoils
ANGLE OF ATTACK
ASPECT RATIO
BLADE AIRFOILS
BLADES
BOUNDARY LAYER
CASCADE STRUCTURES
COEFFICIENTS
COMPRESSOR BLADES
COMPRESSORS
EDGES
Fluid Mechanics
HOT WIRE ANEMOMETERS
INTENSITY
LEADING EDGES
LOSSES
MOMENTUM
NACA-65-A506
PRESSURE
PRESSURE DISTRIBUTION
RECOVERY
REYNOLDS NUMBER
ROUGHNESS
SUCTION
SURFACE ROUGHNESS
SURFACES
THESES
THICKNESS
TRAILING EDGES
TRANSITIONS
TURBULENCE
TWO DIMENSIONAL
TWO DIMENSIONAL FLOW
VELOCITY
WAKE
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Summary:The effects of surface roughness on the losses in the flow through a two-dimensional compressor cascade were studied. The cascade consisted of 7 NACA 65-A506 airfoils with 2-in. chords and aspect ratio of 1. The blades were mounted with a stagger angle of 16 deg, an angle of attack of 15 deg and a solidity of 1.5. The Reynolds number/foot was in excess of 2 million. Three blade configurations were evaluated: one smooth and two with different degrees of roughness applied to the first quarter chord. Hot wire/film anemometers measured velocities and turbulence intensities both in the wake and along the suction surface of the center blade. Surface roughness is shown to increase both boundary layer edge velocities and boundary layer thickness towards the trailing edge while advancing the transition point towards the leading edge. It is also shown to increase wake full thickness, momentum thickness, form factor, and total pressure loss coefficient while decreasing the velocity recovery immediately downstream of the trailing edge. Wake characteristics are most sensitive to an initial increase in roughness but the majority of the changes occur within the first half chord length distance downstream.