Influence of tripping devices in hastening transition in a flat plate submitted to zero and favorable pressure gradients

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Abstract

Tripping devices are commonly used in wind tunnel testing to hasten the laminar-turbulent transition of the boundary layer in order to mimic the aerodynamic effects present in the full-scale application. In this paper, we experimentally investigated the effectiveness of two types of tripping devices, e.g., zigzag strips and randomly distributed grits of varied sizes, in hastening the transition in a flat plate. Flows of zero and favorable pressure gradients were considered. Hot-wire anemometry was used to quantify the velocity profile in the streamwise direction. The acceleration coefficient for the sink flow was K = 5.3 × 10−7 . All studies were performed at chord-based Reynolds number of 1 × 106 . The research demonstrates that the absence of a tripping device led the boundary layer to remain laminar along the entire flat plate length for both zero and positive pressure gradients cases. All trips hastened the transition from laminar to turbulent flow. Zigzag strips introduced stronger disturbances inside the boundary layer compared to grits, and consequently, induced a faster transition. However, the zigzag strips overstimulated the inner region of the boundary layer, requiring a more significant recovery length compared to the grits. The grits with the height of 59% of the boundary layer thickness presented the most consistent results for both pressure gradients since this trip did not overstimulate the boundary layer and developed a turbulent flow faster than the smallest grit investigated, corresponding to 25% of the boundary layer thickness. Furthermore, a recommendation is made regarding the trip height to guarantee the development of a self-similar turbulent boundary layer valid for zero and favorable pressure gradients.
Original languageEnglish
Title of host publicationAIAA Scitech 2020 Forum
ISBN (Electronic)978-1-62410-595-1
DOIs
Publication statusPublished - 2020
EventAIAA Scitech Forum 2020 - Hyatt Regency Orlando, Orlando, United States
Duration: 6 Jan 202010 Jan 2020

Conference

ConferenceAIAA Scitech Forum 2020
CountryUnited States
CityOrlando
Period6/01/2010/01/20

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