Journal
SYMMETRY-BASEL
Volume 14, Issue 2, Pages -Publisher
MDPI
DOI: 10.3390/sym14020342
Keywords
drag reduction; transverse groove; optimal depth; maximum depth
Categories
Funding
- National Natural Science Foundation of China [52176032, 51976005]
- National Science and Technology Major Project [2017-?-0004-0016]
- Aeronautics Power Foundation [6141B090315]
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This paper aims to establish a physical model describing the relationship between the dimensionless depth and inflow velocity of transverse grooves and the drag reduction rate, and solve the optimal and maximum depths using a quasi-analytical approach to reduce carbon emissions.
Reducing the skin-friction drag of a vehicle is an important way to reduce carbon emissions. Previous studies have investigated the drag reduction mechanisms of transverse grooves. However, it is more practical to investigate which groove geometry is optimal at different inflow conditions for engineering. The purpose of this paper is to establish the physical model describing the relationship between the dimensionless depth (H+=Hu(tau)/upsilon) of the transverse groove, the dimensionless inflow velocity (U & INFIN;+=U & INFIN;/u(tau)), and the drag reduction rate (eta) to quasi-analytically solve the optimal and maximum transverse groove depth according to the Reynolds numbers. Firstly, we use the LES with the dynamic subgrid model to investigate the drag reduction characteristics of transverse V-grooves with different depths (h = 0.05~0.9 mm) at different Reynolds numbers (1.09x10(4)~5.44x10(5)) and find that H+ and U & INFIN;(+) affect the magnitude of slip velocity (U-s(+)), thus driving the variation of the viscous drag reduction rate (eta nu) and the increased rate of pressure drag (eta p). Moreover, the relationship between U-s(+), eta nu, and eta p is established based on the slip theory and the law of pressure distribution. Finally, the quasi-analytical solutions for the optimal and maximum depths are solved by adjusting U-s(+) to balance the cost (eta(p)) and benefit (eta(nu)). This solution is in good agreement with the present numerical simulations and previous experimental results.
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