Towards Practical Hybrid Laminar Flow Control
Boundary Layer Stability with Suction and Scalability of Pressure Losses across Perforated Sheets
J.P.P. Hemmen (TU Delft - Aerospace Engineering)
Kotsonis Kotsonis – Mentor
Alberto F. Rius Vidales – Mentor
Bas W. van Oudheusden – Graduation committee member
Daniele Ragni – Graduation committee member
Renato Cosin – Graduation committee member
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Abstract
Hybrid laminar flow control (HLFC) reduces skin friction drag, by combining boundary layer suction with pressure gradient tailoring to delay boundary layer transition. This research addresses two key developments required to perform the aerodynamic design of suction-type HLFC components. First, an existing numerical transition prediction tool was made compatible with boundary layer suction, by incorporating suction in its boundary layer solver and by ensuring that an appropriate grid of disturbance frequencies is evaluated with linear stability theory. Second, the scalability of the pressure losses associated to the perpendicular flow through large-scale and actual-scale perforated sheets was investigated experimentally. This development is required to predict the pressure losses of generic HLFC surfaces. It was found that the scalability of these pressure losses is limited, because the frictional losses inside holes decrease continually with decreasing hole diameter. In contrast, the inertial losses across holes reach a steady value with sufficiently many holes.