Multiple plane stereo PIV results and data from a rake of ten hot-wire probes are used to investigate the largest scale structures in a zero-pressure-gradient turbulent boundary layer. Instantaneous vector fields from stereo PIV in spanwisestreamwise planes reveal long lowand high-speed regions, with a length that often exceeds the viewing window (> 2δ). Also evident is a remarkable degree of s...

resemble streamwise vortices and streaks. A somewhat We study the Linearized Navier-Stokes (LNS) equations from an input-output point of view by analyzing their spatio-temporal frequency responses. We show how the relative roles of Tollmien-Schlichting (TS) waves and streamwise vortices and streaks can be explained as input-output resonances of the spatiotemporal frequency responses. Furthermor...

The impact of periodic pulsation normal to the flow passage on heat and momentum transport is studied using direct numerical simulations. selected test case fully developed supersonic turbulent at Reynolds numbers Reb=ρ¯bU¯bδ/μ¯wall=3000 6000 Mach number Mcl=U¯cl/c¯cl≈1.5, bounded by isothermal walls. introduced imposing a time-periodic uniform body-force in spanwise directions, mimicking two a...

Direct numerical simulations (DNS) are carried out to investigate the effect of effu-sion cooling by blowing through spanwise slits and discrete holes in a laminar flat-plate boundary layer at various Mach numbers. The comparison with experimental data for a Mach-2.67 boundary layer with a cool wall and a spanwise slit shows good agreement. For an adiabatic Mach-6 boundary layer, the focus of t...

Bayesian optimization is a powerful tool in the kinematic design of bio-inspired flight, where expensive high-fidelity numerical simulations are required. However, traditional single acquisition strategy cannot adapt to all problems, which have various input–output characteristics. The hybrid improves robustness by utilizing three types functions, and each function assigned different balance pa...

Time-resolved DPIV measurements performed in wall parallel planes at several wall normal locations in a turbulent boundary layer (TBL) are used to illuminate the distribution of wall parallel velocities in a three-dimensional energy spectrum over streamwise, spanwise, and temporal wavelengths. To our knowledge, this is the rst time this type of spectral distribution has been reported. Slices of...

The small vortex generation is a key issue of the mechanism for late flow transition and turbulence generation. It was widely accepted that small length vortices were generated by large vortex breakdown. According to our recent DNS, we find that the hairpin vortex structure is very stable and never breaks down to small pieces. On the other hand, we recognize that there are strong positive spike...

Microscopic particle-image velocimetry (microPIV) measurements are made in the streamwise–wallnormal plane of a 536 lm capillary at Re = 4,500 to study the statistical and structural features of wall turbulence at the microscale. Single-point velocity statistics, including the mean velocity profile, the root-mean-square streamwise and wall-normal velocities, and the Reynolds shear stress profil...