High-speed vehicles experience a highly challenging environment in which the freestream Mach number and surface temperature greatly influence aerodynamic drag and heat transfer. The interplay of these two parameters strongly affects the near-wall dynamics of high-speed turbulent boundary layers (TBLs) in a non-trivial way, breaking similarity arguments on velocity and temperature fields, typically derived for adiabatic cases. We present direct numerical simulations of flat-plate zero-pressure-gradient TBLs spanning three freestream Mach numbers [2,4,6] and four wall temperature conditions (from adiabatic to very cold walls), emphasising the choice of the wall-cooling parameter to recover a similar flow organisation at different Mach numbers. We link qualitative observations on flow patterns to first- and second-order statistics to explain the decoupling of temperature–velocity fluctuations that occurs at reduced wall temperatures and high Mach numbers. For these cases, we discuss the formation of a secondary peak of thermal production in the viscous sublayer, which is in contrast with the monotonic behaviour of adiabatic profiles. We propose different physical mechanisms induced by wall-cooling and compressibility that result in apparently similar flow features, such as a higher peak in the streamwise velocity turbulence intensity, and distinct features, such as the separation of turbulent scales.

Cogo, M., Baù, U., Chinappi, M., Bernardini, M., Picano, F. (2023). Assessment of heat transfer and Mach number effects on high-speed turbulent boundary layers. JOURNAL OF FLUID MECHANICS, 974 [10.1017/jfm.2023.791].

Assessment of heat transfer and Mach number effects on high-speed turbulent boundary layers

Mauro Chinappi;
2023-01-01

Abstract

High-speed vehicles experience a highly challenging environment in which the freestream Mach number and surface temperature greatly influence aerodynamic drag and heat transfer. The interplay of these two parameters strongly affects the near-wall dynamics of high-speed turbulent boundary layers (TBLs) in a non-trivial way, breaking similarity arguments on velocity and temperature fields, typically derived for adiabatic cases. We present direct numerical simulations of flat-plate zero-pressure-gradient TBLs spanning three freestream Mach numbers [2,4,6] and four wall temperature conditions (from adiabatic to very cold walls), emphasising the choice of the wall-cooling parameter to recover a similar flow organisation at different Mach numbers. We link qualitative observations on flow patterns to first- and second-order statistics to explain the decoupling of temperature–velocity fluctuations that occurs at reduced wall temperatures and high Mach numbers. For these cases, we discuss the formation of a secondary peak of thermal production in the viscous sublayer, which is in contrast with the monotonic behaviour of adiabatic profiles. We propose different physical mechanisms induced by wall-cooling and compressibility that result in apparently similar flow features, such as a higher peak in the streamwise velocity turbulence intensity, and distinct features, such as the separation of turbulent scales.
2023
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore ING-IND/06
English
Cogo, M., Baù, U., Chinappi, M., Bernardini, M., Picano, F. (2023). Assessment of heat transfer and Mach number effects on high-speed turbulent boundary layers. JOURNAL OF FLUID MECHANICS, 974 [10.1017/jfm.2023.791].
Cogo, M; Baù, U; Chinappi, M; Bernardini, M; Picano, F
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/359063
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