STRUCTURE OF THE REYNOLDS STRESS
AND THE OCCURRENCE OF BURSIS IN
THE TURBULENT BOUNDARY LAYER
1. INTRODUCTION
The past decade has been a period of rapid advance in our understand:ng
of the nature of the structure of the fluctuating flow h k l in the turbulent
boundary layer. The decade began at Stanford University with the perfection, by Runstadler et al. (1%3), of a flow visuahtiga method using small
hydrogen bubbles produced by electrolysis of water‘along a fine current
carrying wire. With this flow visuabtion method the Stanford group was
able to identify a deterministic pattern and sequence of events callad a burst
during which large contributions to Reynolds strm murred. The bursts
that were observcd (see Kim et al., 1968) resulted in a violent and intense
swirling and mixing of low spaad fluid near the wall ‘Htith h i d farther from
the wall.
Corino and Brodkey (1969) have recently reported results of flow visualization studies in the boundary layer near the wall obtained by observing the
motion of small neutrally buoyant particles suspended in water. Their observations confirmed the results of the Stanford group and contributed the
important new information that when a burst occurred there was a violent
small scale interaction in the region 7 < y + < 30 between fluid moving
unusually slowly near the wall and higher spead fluid slightly farther from
the wall [here y + = yu*/v and u+ = ( ~ / p ) ’ / ~
where T is the wall shear stress].
In addition, Corino and Brodkey abo identified an event they called a
“sweep” in which it appeared that after a burst of slowcr speed outward
moving fluid occurred the Illrid in the violent bursting interaction was
replaced or swept away by high speed fluid moving toward the wall. Corino
and Brodkey estimated that approximately 70 of the contribution to the
’ Presetit address: Department of Power Mechanical Engineering, National Tsing Hua
University, Hsinchu, Taiwan.
287
AND THE OCCURRENCE OF BURSIS IN
THE TURBULENT BOUNDARY LAYER
1. INTRODUCTION
The past decade has been a period of rapid advance in our understand:ng
of the nature of the structure of the fluctuating flow h k l in the turbulent
boundary layer. The decade began at Stanford University with the perfection, by Runstadler et al. (1%3), of a flow visuahtiga method using small
hydrogen bubbles produced by electrolysis of water‘along a fine current
carrying wire. With this flow visuabtion method the Stanford group was
able to identify a deterministic pattern and sequence of events callad a burst
during which large contributions to Reynolds strm murred. The bursts
that were observcd (see Kim et al., 1968) resulted in a violent and intense
swirling and mixing of low spaad fluid near the wall ‘Htith h i d farther from
the wall.
Corino and Brodkey (1969) have recently reported results of flow visualization studies in the boundary layer near the wall obtained by observing the
motion of small neutrally buoyant particles suspended in water. Their observations confirmed the results of the Stanford group and contributed the
important new information that when a burst occurred there was a violent
small scale interaction in the region 7 < y + < 30 between fluid moving
unusually slowly near the wall and higher spead fluid slightly farther from
the wall [here y + = yu*/v and u+ = ( ~ / p ) ’ / ~
where T is the wall shear stress].
In addition, Corino and Brodkey abo identified an event they called a
“sweep” in which it appeared that after a burst of slowcr speed outward
moving fluid occurred the Illrid in the violent bursting interaction was
replaced or swept away by high speed fluid moving toward the wall. Corino
and Brodkey estimated that approximately 70 of the contribution to the
’ Presetit address: Department of Power Mechanical Engineering, National Tsing Hua
University, Hsinchu, Taiwan.
287