EPTT 2022

13th Spring School on Transition and Turbulence

Wall pressure fluctuations measurement during boundary layer transition

Submission Author: Matheus Maia Beraldo , SP
Co-Authors: Matheus Maia Beraldo, Christian Bresci, Victor Barcelos Victorino, Marcello Augusto Faraco de Medeiros
Presenter: Victor Barcelos Victorino

doi://10.26678/ABCM.EPTT2022.EPT22-0047

 

Abstract

With the constant raise in fuel prices and regulation of new pollutant emission standards, reducing consumption and greenhouse gas emissions are problems that are becoming increasingly relevant in commercial and military aviation. The benefits of using laminar flow control over larger regions of the surface can reach 10% of the total drag of the aircraft, which would result in great savings in operating costs. However, for this technology to develop, being able to properly predict the transition point between the laminar and turbulent flow is of great importance. This work objective was to experimentally study the transition of the boundary layer between the laminar and turbulent flow by measure of wall pressure fluctuations with microphones. Experiments were conducted at the Low Acoustic Noise and Turbulence (LANT) wind tunnel at University of São Paulo. The model consist of a flat plate with 2320mm x 1000mm x 10mm and the surface finish was specially selected to reduce the influence on the transition. Measurements of wall pressure fluctuations were carried out using an array of 90 microphones attached to the rear surface of the plate and connected to the test surface through pinholes (0,3mm). The model has more than 400 pinholes where the microphones can be placed according of interest. The diameter of the pinholes were carefully studied not to affect the development of the boundary layer in the model and to set the Helmholtz resonance frequency distant from the frequencies of interest. Results shown that the microphones were able to locate the region where the boundary layer transition occurs and to identify disturbances inside the boundary layer.

Keywords

Wind Tunnel, Wall Pressure Fluctuations, Boundary Layer

 

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