Abstract The role of streamline curvature-driven favourable pressure gradients in modifying the turbulence structure a Mach 4.9, high-Reynolds-number ( ${\mathit{Re}}_{\theta } = 43\hspace{0.167em} 000$ ) boundary layer is examined. Three gradient cases $\beta (\mathrm{d} p/ \mathrm{d} x)({\delta }^{\ast / {\tau }_{w} )= 0. 07, - 3$ and $- 1. 0$ are characterized via particle image velocimetry. expected stabilizing trends Reynolds stresses observed, with sign reversal shear stress outer part...

We present an initial demonstration of simultaneous velocity and temperature mapping in gaseous flow fields using a new nitric oxide planar laser-induced fluorescence-based method. The vibrationally excited NO monitoring (VENOM) technique is extension two-component velocimetry generated from the photodissociation seeded NO(2) [Appl. Opt. 48, 4414 (2009)], where two sequential fluorescence images are obtained probing different rotational states to provide both maps. Comparisons computational...

We report a laser diagnostic technique which relies on planar laser-induced fluorescence of vibrationally excited nitric oxide (NO v=1 ) molecules produced from the 355 nm photodissociation seeded NO 2 for molecular tagging velocimetry applications. The was applied toward an axisymmetric highly underexpanded jet flowfield to yield single-component (streamwise) velocity maps. Detection photodissociated would be valuable in flow environments where desirable, but there are also significant...

Abstract Femtosecond laser electronic excitation tagging (FLEET) velocimetry is applied in a hypersonic boundary layer behind an array of turbulence-inducing trips. One-dimensional mean velocity and root-mean-square (RMS) fluctuation profiles are extracted from FLEET emissions oriented across 2.75 ∘ wedge through above flat plate two test campaigns spanning 21 tunnel runs. The experiment was performed the Texas A&M University Actively Controlled Expansion that operated near Mach 6.0 with...

In this article, the authors present an experimental investigation of thermochemical relaxation regions downstream symmetric Mach reflections generated in 8.5 flows with stagnation enthalpies from 7 to 10 MJ/kg. The experiment was performed Hypervelocity Expansion Tunnel at National Aerothermochemistry and Hypersonics Laboratory Texas A&M University. focused on studying nitric oxide morphology vicinity a strong normal shock wave shear layers. Experimental planar laser-induced...

The Air Force Office of Scientific Research and the Laboratory (AFRL) funded Boundary Layer Turbulence Flight Experiment in Memory Mike Holden (BOLT II) to better understand quantify natural forced boundary-layer transition turbulence hypersonic flight regimes for a complex, three-dimensional geometry. Texas A&M University CUBRC led mission vehicle design along with critical support from AFRL NASA. experimental launched NASA Wallops on two-stage suborbital sounding rocket March 21st,...

The smooth-wall transition process was characterized during flight at Mach 6.0 on a research geometry with concave curvature and swept leading edges, which introduced boundary layer stationary laminar vortex streaks, competing mechanisms, complex early turbulence. This flight, termed BOLT II, the second in series coordinated by Air Force Office of Scientific Research. Surface heat flux, skin friction, pressure fluctuation spectra were acquired to characterize process. Transition first...

We investigate the effects of thermal boundary conditions and Mach number on turbulence close to walls. In particular, we study near-wall asymptotic behaviour for adiabatic pseudo-adiabatic walls, compare recently found near isothermal cold walls (Baranwal et al . 2022. J. Fluid Mech. 933 , A28). This is done by analysing a new large database highly-resolved direct numerical simulations turbulent channels with different wall centreline numbers. observe that power-law Reynolds stresses as...

We report the application of molecular tagging velocimetry (MTV) toward two-component as demonstrated in an underexpanded free jet flowfield. Two variants MTV technique are presented: 1) electronic excitation seeded nitric oxide (NO) with gated fluorescence imaging (fluorescence lifetime) and 2) photodissociation NO2 followed by NO (NO2 photodissociation). The lifetime is advantageous low-quenching, high-velocity flowfields, while useful high-quenching environments, either high- or...

The performance of the vibrationally excited nitric oxide monitoring (VENOM) technique for simultaneous velocity and temperature measurements in gaseous flowfields is presented. Two different schemes were investigated, employing methods to "write" a transient NO grid flow using 355 nm photolysis NO(2), which was subsequently probed by planar laser induced fluorescence imaging extract maps. We find that only one scheme provides full-frame most accurate measurement attained writing an pattern...

We present measurements demonstrating simultaneous determination of velocity and temperature using a variant the Vibrationally Excited Nitric Oxide Monitoring (VENOM) technique that does not employ NO2. The is based on tagging by electronic excitation NO in A²∑(1/2)⁺ (v'=0)←X2Π1/2(v''=0) band subsequent formation vibrationally excited NO(X2Π) spontaneous emission collisional quenching. Sequential planar laser-induced fluorescence imaging nascent NO(X2Π, v''=1) was used to obtain spatially...

View Video Presentation: https://doi.org/10.2514/6.2022-1602.vid A new hypervelocity expansion tunnel (HXT) was recently brought to operational status at Texas A&M University. This facility allows for replication of true flight temperature, pressure, and velocity over a large portion many hypersonic trajectories. The advantage an is the ability produce high enthalpy test conditions without introducing unrealistic air chemistry. HXT constructed from 0.48 m diameter tube, 30.5 long with 0.92...

Quasi-random distributed roughness topologies were produced to transition the boundary layer over an axisymmetric tangent ogive nosecone in hypersonic flow. Surface was accomplished by applying a cylindrical 2D Fourier series triangulated surface of nosetip manner that resembles sand grit roughness. In total, one smooth tip and three rough tips with varying heights 3D-printed examine their effectiveness at transition. The models assessed Infrared (IR) Thermography Focused Laser Differential...

Femtosecond Laser Electronic Excitation Tagging (FLEET) and Coherent Anti-Stoke Raman Spectroscopy (CARS) were used to measure freestream flows in the Hypervelocity Expansion Tunnel (HXT) at Texas A&M University. Hypersonic of air nitrogen with a Mach number 8.5 stagnation enthalpies ranging from 1.8 7.3 MJ/kg probed. Despite short test times bright, broadband background emission, accurate FLEET velocity measurements achieved. Theoretical computations HXT facility validated using measured...

Thefull,three-dimensionalFavre-averaged Navier -Stokesequations,coupledwiththesecond-orderZhang etal. (Zhang, H., So, R., Gatski, T., and Speziale, C., A Near-Wall Second-Order Closure for Compressible Turbulent Flows,Near-WallTurbulentFlows ,editedbyR. So,C.Speziale, andB.Launder,Elsevier,NewYork,1993,pp.209 - 218) Reynolds-stress turbulence K-≤ models, were used to numerically simulate a 25-deg, Mach 1.8 injection into Mach3.0 crosse ow.Detailed comparisonswith experimental data...

Sonic transverse gaseous injection into a Mach 5.0 freestream flow was numerically simulated using two-equation and detached-eddy turbulence models. Circular- diamond-shaped injectors were investigated in this study. The numerical simulations compared with available experimental results it determined that both the Reynolds-averaged Navier-Stokes simulation models captured secondary structure. A detailed comparison of structures performed for injectors. Two new vortex practical importance...

The effects of convex curvature on the outer structure a Mach 4.9 turbulent boundary layer (Reθ = 4.7 × 104) are investigated using condensate Rayleigh scattering and analyzed spatial correlations, intermittency, fractal theory. It is found that post-expansion morphology appears subtle, but certain features exhibit more obvious response. large-scale flow structures survive initial expansion, appearing to maintain same physical size. However, due nature expansion fan, differential...

The leading-edge flow structure of the NACA 0012 airfoil is experimentally investigated under dynamic-stall conditions (; , 22.4 deg; ) using planar particle image velocimetry. was dynamically pitched about one-fourth chord at a reduced frequency, . As expected, on upstroke, remains attached in region above static stall angle, whereas during downstroke, separated below angle. A phase-averaging procedure involving triple velocity decomposition combination with Hilbert transform enables entire...