Abstract
Rough turbulent pipe flow is reviewed with two purposes: one is to identify a standard experimental rough surface, the other is to provide a conceptual frame for the experimental investigation of drag reduction in pipes pursued at FVU AB. The basis of handbook knowledge is Nikuradse`s set of friction data obtained with sand-roughened pipes. The scale obtained is a consistent one and experience with various natural surfaces has been correlated with these data using a sand equivalent roughness. Unfortunately, this has become a flow parameter which is quite difficult to relate to the actual geometry of the rough surface. Nikuradse`s original surfaces are practically impossible to reproduce, making them a poor experimental standard. Considerable progress has been obtained in the correlation of flow parameters with roughness geometry for artificial, but reproducible, two-dimensional roughness patterns such as transverse square ribs. These ribs are then a suitable experimental standard, in spite of the lack of intuitive correspondence with natural roughness. Some progress has been obtained for three-dimensional roughness patterns. For Newtonian fluids, the most energy-efficient heat transfer enhancing structures of a pipe wall are those that just puncture the viscous sublayer or promote swirl. The less efficient are fins that protrude far
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Citation Formats
Bjurstroem, H.
DRA 4. Wall roughness in turbulent pipe flow.
Sweden: N. p.,
1993.
Web.
Bjurstroem, H.
DRA 4. Wall roughness in turbulent pipe flow.
Sweden.
Bjurstroem, H.
1993.
"DRA 4. Wall roughness in turbulent pipe flow."
Sweden.
@misc{etde_10150470,
title = {DRA 4. Wall roughness in turbulent pipe flow}
author = {Bjurstroem, H}
abstractNote = {Rough turbulent pipe flow is reviewed with two purposes: one is to identify a standard experimental rough surface, the other is to provide a conceptual frame for the experimental investigation of drag reduction in pipes pursued at FVU AB. The basis of handbook knowledge is Nikuradse`s set of friction data obtained with sand-roughened pipes. The scale obtained is a consistent one and experience with various natural surfaces has been correlated with these data using a sand equivalent roughness. Unfortunately, this has become a flow parameter which is quite difficult to relate to the actual geometry of the rough surface. Nikuradse`s original surfaces are practically impossible to reproduce, making them a poor experimental standard. Considerable progress has been obtained in the correlation of flow parameters with roughness geometry for artificial, but reproducible, two-dimensional roughness patterns such as transverse square ribs. These ribs are then a suitable experimental standard, in spite of the lack of intuitive correspondence with natural roughness. Some progress has been obtained for three-dimensional roughness patterns. For Newtonian fluids, the most energy-efficient heat transfer enhancing structures of a pipe wall are those that just puncture the viscous sublayer or promote swirl. The less efficient are fins that protrude far into the core or inserts that act solely on the core flow. Drag reduction with additives is connected with the creation of an elastic buffer zone between viscous and inertial sublayers. At maximum drag reduction, this buffer zone extends into the core. Drag reduction is accompanied by a reduction in heat transfer. Only little information is available on the interaction of wall roughness with drag reduction, but there may be reason to revise the ranking of heat transfer enhancing devices for these non-Newtonian fluids. 98 refs, 54 figs, 1 tab}
place = {Sweden}
year = {1993}
month = {May}
}
title = {DRA 4. Wall roughness in turbulent pipe flow}
author = {Bjurstroem, H}
abstractNote = {Rough turbulent pipe flow is reviewed with two purposes: one is to identify a standard experimental rough surface, the other is to provide a conceptual frame for the experimental investigation of drag reduction in pipes pursued at FVU AB. The basis of handbook knowledge is Nikuradse`s set of friction data obtained with sand-roughened pipes. The scale obtained is a consistent one and experience with various natural surfaces has been correlated with these data using a sand equivalent roughness. Unfortunately, this has become a flow parameter which is quite difficult to relate to the actual geometry of the rough surface. Nikuradse`s original surfaces are practically impossible to reproduce, making them a poor experimental standard. Considerable progress has been obtained in the correlation of flow parameters with roughness geometry for artificial, but reproducible, two-dimensional roughness patterns such as transverse square ribs. These ribs are then a suitable experimental standard, in spite of the lack of intuitive correspondence with natural roughness. Some progress has been obtained for three-dimensional roughness patterns. For Newtonian fluids, the most energy-efficient heat transfer enhancing structures of a pipe wall are those that just puncture the viscous sublayer or promote swirl. The less efficient are fins that protrude far into the core or inserts that act solely on the core flow. Drag reduction with additives is connected with the creation of an elastic buffer zone between viscous and inertial sublayers. At maximum drag reduction, this buffer zone extends into the core. Drag reduction is accompanied by a reduction in heat transfer. Only little information is available on the interaction of wall roughness with drag reduction, but there may be reason to revise the ranking of heat transfer enhancing devices for these non-Newtonian fluids. 98 refs, 54 figs, 1 tab}
place = {Sweden}
year = {1993}
month = {May}
}