Abstract
Abstract
Highlights
Methods to modify and control the boundary layer behaviour have been sought from the earliest stage of boundary layer studies and, in this respect, wall-normal transpiration immediately appeared as a relatively simple and very effective control technique
The case of a zero pressure gradient (ZPG) boundary layer with uniform suction applied at the wall is of particular interest because it is possible to achieve a state for which the momentum loss due to wall friction is exactly compensated by the entrainment of high-momentum fluid due to suction, the boundary layer thickness remains constant in the streamwise direction
It has been known since the earliest studies on suction boundary layers that an initially turbulent boundary layers (TBLs) will eventually relaminarize for large enough suction rates
Summary
Methods to modify and control the boundary layer behaviour have been sought from the earliest stage of boundary layer studies and, in this respect, wall-normal transpiration immediately appeared as a relatively simple and very effective control technique. Since wall suction has a strong stabilizing effect on boundary layers, it has been investigated as a technique to delay the laminar–turbulent transition to accomplish drag reduction by the inherent lower friction drag of a laminar boundary layer in comparison with a turbulent boundary layer (TBL) (see Ulrich (1947) and Kay (1948) among others). The case of a zero pressure gradient (ZPG) boundary layer with uniform suction applied at the wall is of particular interest because it is possible to achieve a state for which the momentum loss due to wall friction is exactly compensated by the entrainment of high-momentum fluid due to suction, the boundary layer thickness remains constant in the streamwise direction. A turbulent asymptotic suction boundary layer (TASBL) appears to be considerably more difficult to obtain than its laminar counterpart. Bobke, Örlü & Schlatter (2016) numerically obtained two TASBLs through large eddy simulations (LES) and raised doubts on the possibility of obtaining an ASBL in a practically realizable experiment
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