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Accession Number:

AD1168537

Title:

Surface Irregularity Effects on Laminar-Turbulent Transition - Understanding the Surface Quality Requirements for Laminar Flow on Wings

Author(s):

• Faraco de Medeiros, Marcello A.
• Mathias, Marlon S.
• Himeno, Fernando H.
• Beraldo, Matheus M.
• Salaro, Christian B.
• Victorino, Victor B.
• Basilio, Ana E.
• Aguirre, Felipe O.

Author Organization(s):

• Fundacao de Apoio a Universidade de Sao Paulo

Report Date:

2022-04-24

Abstract:

The effect of gaps and bumps on transition to turbulence in boundary layers was investigated. Linear stability theory and direct numerical simulations revealed that gaps can behave like large cavities and induce transition. Results explained experiments recently developed and published by Boeing. The effect of Re, Ma, ratio between boundary layer thickness and gap dimensional and gap aspect ratio was investigated and explained physically. Transition is caused by the interaction of Rossiter and centrifugal modes. Centrifugal modes nonlinearly affect the Rossiter instability, but the linear instability provides a lower safe bound for laminar flow. The interaction of TS waves and bumps were studied via very accurate direct numerical simulations. A boundary for a linear effect of the bump height on TS waves was found to be about 10% boundary layer displacement thickness. The effect of Mach and frequency was also investigated. A very precise and efficient model based on a Taylor expansion combined with a Stokes layer was developed to be used in numerical simulations. Theoretical equations were deduced for the optimal choice of computational parameters for use of matrix-free methods of global instability analysis.

Document Type:

Conference:

Journal:

Pages:

356

File Size:

29.89MB

Contracts:

Grants:

Descriptors:

Identifiers:

• Surface Irregularity
• Laminar-Turbulent Transitions
• boundary layer thickness
• gap dimensional ratio
• gap aspect ratio
• Centrifugal modes
• Rossiter modes
• Taylor expansion
• Stokes layers
• Theoretical equations
• matrix-free methods
• global instability analysis
• Gap instability boundary
• by-pass transitions
• ts waves
• ts (Tollmien Schlichting)
• bump wakes
• hydrodynamic stability
• open cavities

SubjectCategory:

• Physics

Communities of Interest:

• Weapons Technologies

Distribution Statement:

Approved For Public Release

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