Predicting the Drag of Rough Surfaces

2021 ◽  
Vol 53 (1) ◽  
pp. 439-471
Author(s):  
Daniel Chung ◽  
Nicholas Hutchins ◽  
Michael P. Schultz ◽  
Karen A. Flack
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Incompressible Flow ◽  
Rough Surfaces ◽  
Full Scale ◽  
Rough Wall ◽  
Turbulent Fluid Flow ◽  
Turbulent Fluid

Reliable full-scale prediction of drag due to rough wall-bounded turbulent fluid flow remains a challenge. Currently, the uncertainty is at least 10%, with consequences, for example, on energy and transport applications exceeding billions of dollars per year. The crux of the difficulty is the large number of relevant roughness topographies and the high cost of testing each topography, but computational and experimental advances in the last decade or so have been lowering these barriers. In light of these advances, here we review the underpinnings and limits of relationships between roughness topography and drag behavior, focusing on canonical and fully turbulent incompressible flow over rigid roughness. These advances are beginning to spill over into multiphysical areas of roughness, such as heat transfer, and promise broad increases in predictive reliability.

The Effect of Fluid Flow on Heat Transfer and Shell Growth in Continuous Casting of Copper

2006 ◽  
Vol 508 ◽  
pp. 503-508 ◽  
Author(s):  
Sami Vapalahti ◽  
Seppo Louhenkilpi ◽  
Tuomo Räisänen
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Continuous Casting ◽  
Turbulent Fluid Flow ◽  
Turbulent Fluid ◽  
Material Data ◽  
University Of Technology ◽  
Flow Heat ◽  
Heat Transfer And Solidification ◽  
Transfer Models

Molten metal is cooled in a continuous casting mould forming initially a thin shell that grows thicker. The main phenomena in the mould are: fluid flow, heat transfer and solidification. A lot of mathematical models have been developed to simulate these phenomenons in continuous casting machines but most of the models developed are not calculating the fluid flow at all. In these models, it is assumed that the strand (solid and liquid) is withdrawn through the machine with a constant velocity field (= casting speed) and the convective heat transfer generated by the fluid flow is taken into account by using an effective thermal conductivity method. Also at the Helsinki University of Technology, these kinds of heat transfer models have been developed (TEMPSIMU for steels and CTEMP3D for coppers). The flow in the mould is three-dimensional and turbulent. Coupled models calculate the fluid flow, heat transfer and solidification simultaneously. The fluid flow is affected by many things: inlet flow rate, design of the inlet nozzle (SEN), immersion depth of the SEN, movement of the solid shell, natural convection, solidification shrinkage, etc. and the fully coupled, turbulent fluid flow and heat transfer models are generally subjected to convergence difficulties and they need a lot of computing time. Due to these reasons, these kinds of models are not so much used in industry so far. In the present study, a commercial FLOW-3D package is used to make coupled simulations of heat transfer, turbulent fluid flow and solidification in a copper continuous casting machine. The effect of thermophysical material data are also studied and presented. The material data are calculated by a model developed at the Helsinki University of Technology, called CASBOA.

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