# Accession Number:

## ADA167186

# Title:

## Bursts and Pressure Fluctuations in Turbulent Boundary Layers.

# Descriptive Note:

## Final rept. Nov 84-Nov 85,

# Corporate Author:

## IMPERIAL COLL OF SCIENCE AND TECHNOLOGY LONDON (ENGLAND) DEPT OF AERONAUTICS

# Personal Author(s):

# Report Date:

## 1986-01-01

# Pagination or Media Count:

## 52.0

# Abstract:

Surface pressure fluctuations below turbulent boundary layers were studied, in part, because they can be regarded as footprints of passing turbulent eddies. The pressure fluctuations are formally described by a Poisson equation, implying that the pressure fluctuation at a given point is mathematically represented by the integral of a source term over the whole flow field, with a weighting inversely proportional to the distance of the source from the given point. In turbulent boundary layers, fluctuations were made in a low-speed constant pressure the high-frequency part of the wall pressure fluctuations is generated mainly within the inner layer - say, the first 20 of the boundary layer thickness - and the low-frequency part is generated mainly in the outer layer. Measurements of velocity and surface-pressure turbulent boundary layer well downstream of an extensive region of wall roughness. The turbulence near the wall was representative of a smooth-wall flow, while that in the outer layer was typical of the upper stream rough-wall flow. Comparison with previous measurements on an entirely smooth wall illustrates the relative contributions of the inner and outer layers to the surface pressure fluctuations. Further work has been done to compare the VITA Variable ge conditional-sampling algorithm withuctuations were more advanced algorithms. Keywords Turbulent boundary layer, Noise measurement, Statistical analysis, Surface roughness, and VITA algorithm.

# Descriptors:

- *TURBULENT BOUNDARY LAYER
- *VARIABLE PRESSURE
- VELOCITY
- ALGORITHMS
- MEASUREMENT
- THICKNESS
- LAYERS
- SURFACE ROUGHNESS
- BOUNDARY LAYER
- TURBULENCE
- EDDIES(FLUID MECHANICS)
- TIME
- VARIABLES
- WEIGHTING FUNCTIONS
- FLOW FIELDS
- SURFACE PROPERTIES
- INTERNAL
- SAMPLING
- PRESSURE
- WALLS
- EXTERNAL
- FLOW
- STATISTICAL ANALYSIS
- NOISE
- ROUGHNESS
- STREAMS
- INTERVALS
- UNITED KINGDOM

# Subject Categories:

- Statistics and Probability
- Fluid Mechanics