Computations are performed to study the flow past an isolated roughness element in a Mach 3.5, laminar, flat plate boundary layer. To determine effects of on location laminar-turbulent transition inside layer, instability characteristics stationary wake behind investigated over range heights. The adjacent spanwise plane symmetry is characterized by narrow region increased layer thickness. Beyond near region, centerline streak surrounded pair high-speed streaks with reduced thickness and...

A Nomarski polarizing prism has been used in conjunction with a focused laser differential interferometer to measure the phase velocity of density disturbance at sampling frequencies ≥10MHz. Use this enables simultaneous measurement disturbances two closely spaced points that can be arbitrarily oriented about instrument's optical axis. The orientation is prescribed by rotating Since all four beams (one beam pair each point) propagate parallel one another within test volume, any bias imparted...

Transition on a swept-wing leading-edge model at Mach 3.5 is investigated. Surface pressure and temperature measurements are obtained in the NASA Langley Research Center Supersonic Low-Disturbance Tunnel. For one case, temperature-sensitive paint sublimating chemical used to visualize surface flow features such as transition location. The experimental data compared with 1) mean-flow results computed solutions thin-layer Navier-Stokes equations 2) N-factors using envelope e N method....

Progress on an experimental effort to quantify the instability mechanisms associated with roughness-induced transition in a high-speed boundary layer is reported this paper. To simulate low-disturbance environment encountered during high-altitude flight, study was performed NASA-Langley Mach 3.5 Supersonic Low-Disturbance Tunnel. A flat plate trip sizing first identify roughness height required force transition. That study, which included onset measurements under both quiet and noisy...

A swept flat plate model with an imposed pressure gradient was experimentally investigated in a low-speed flow to determine the effect of backward-facing step on transition stationary crossflow-dominated flow. Detailed hotwire measurements boundary-layer were performed investigate upstream shift due height 49% local unperturbed thickness. Increasing initial crossflow amplitude caused movement front for case. The increase growth instabilities, but at sufficiently low (<0.04Ue ) so that not...

An experimental investigation was conducted to examine acoustic receptivity and subsequent boundary-layer instability evolution for a Blasius boundary layer formed on flat plate in the presence of two-dimensional oblique (three-dimensional) surface waviness. The effect non-localized roughness geometry wave amplitude process explored. had well-defined wavenumber spectrum with fundamental k w . A planar downstream-travelling created temporally excite flow near resonance frequency an unstable...

Supersonic boundary-layer receptivity to freestream acoustic disturbances is investigated by solving the Navier–Stokes equations for Mach 3.5 flow over a 7 deg half-angle cone. The are generated from wavy wall placed at nozzle wall. radiated obtained linearized Euler equations. results show that no noticeable instability modes when impinge cone obliquely. perturbations inside boundary layer response of external forcing. amplitude forced about 2.5 times larger than incoming field zero...

An experimental campaign was conducted to measure and characterize the freestream disturbance levels in NASA Langley Research Center 20-Inch Mach 6 Wind Tunnel. A pitot rake instrumented with fast pressure transducers, hot wires, an atomic layer thermopile quantify fluctuation of pressure, mass flux, heat respectively. In conjunction these probe-based measurements, focused laser differential interferometry used optically density fluctuations. Measurements were made at five nominal different...

Updates to an analytic tool developed for Shuttle support predict the onset of boundary layer transition resulting from thermal protection system damage or repair are presented. The is part a suite tools that analyze local aerothermodynamic environment enable informed disposition making recommendations fly as repair. Using mission specific trajectory information and details each d agmea site repair, expected time (and thus Mach number) predicted help define proper environments use in...

Recent flow measurements have been acquired in the National Transonic Facility to assess test-section unsteady environment. The primary purpose of test is determine feasibility facility conduct laminar-flow-control testing and boundary-layer transition-sensitive at flight-relevant operating conditions throughout transonic Mach number range. can operate two modes, warm cryogenic for full semispan-scaled models. Data were unit Reynolds numbers ranging from collectively air conditions....

Progress on an experimental study of laminar-to-turbulent transition induced by isolated roughness element in a supersonic laminar boundary layer is reported this paper. Here, the primary focus effects planform shape instability and characteristics. Four different shapes were considered (a diamond, circle, right triangle, 45 degree fence) height width each one was held fixed so that consistent frontal area presented to oncoming layer. The nominal Reynolds number 462 ratio thickness 0.48....

Efforts to design and operate hypersonic entry vehicles are constrained by many considerations that involve all aspects of an vehicle system. One the more significant physical phenomenon affect trajectory thermal protection system is occurrence boundary layer transition from a laminar turbulent state. During Space Shuttle Return To Flight activity following loss Columbia her crew seven, NASA's aerothermodynamics community implemented engineering correlation based framework for prediction on...

The effects of forward- and backward-facing steps on the receptivity stability three-dimensional supersonic boundary layers over a swept wing with blunt leading edge are numerically investigated for freestream Mach number 3 sweep angle 30 degrees. flow fields obtained by solving full Navier-Stokes equations. evolution instability waves generated surface roughness is simulated without steps. separation bubble lengths about 5-10 step heights forward-facing 10 step. linear calculations show...

The steady flow fields with and without roughness elements are obtained by solving the full Navier-Stokes equations. N-factors computed in this study at transition onset locations reported Ref. 1 for over swept cylinder approximately 16.5 traveling crossflow disturbances 9 stationary disturbances. high based on our past experiences. However, they comparatively smaller than those Archambaud et al., who found N-factor values range of 20 to 25 13 Similarly, sharp wing 7 2.5, respectively, blunt...

A review is provided of recent aerothermodynamic ground-test contributions by NASA Langley Research Center (LaRC) to the BOLT flight test program. Several entries into Aerothermodynamic Laboratory 20-Inch Mach 6 Air Tunnel are discussed. These were intended support development and design hardware instrumentation. Some trends observations from these provided. Also, a comparison two different global heat transfer techniques included

Boundary-layer transition on a sharp 5-deg half-angle cone at incidence was investigated Mach 3.5 in NASA's Supersonic Low-Disturbance Pilot Tunnel. The tests were conducted with low and high levels of freestream acoustic disturbance, four angles attack (alpha/theta-c = 0, 0.12, 0.4, 0.8). Transition data, obtained without significantly reduced disturbance levels, are compared conventional ('noisy') wind-tunnel data. It found that, under quiet flow conditions, there no significant unit...

Experimental measurements were performed on a swept flat-plate model with an airfoil leading edge and imposed chordwise pressure gradient to determine the effects of backward-facing step transition in low-speed stationary crossflow-dominated boundary layer. Detailed hot-wire for three heights ranging from 36 49% boundary-layer thickness at corresponding subcritical, nearly critical, critical cases. In general, had small localized effect growth crossflow vortex, whereas unsteady disturbance...

Hot-wire measurements in a Mach 3.5 quiet tunnel were made the wake of roughness patch on flat plate. These used to determine mode shapes and frequencies dominant instabilities leading boundary-layer transition. The egg-crate pattern is an analytic function described by sinusoidal equation, similar array discrete elements that are positioned spanwise streamwise grid, but containing both protuberances dimples. This intermediate configuration towards understanding underlying physics...

The receptivity and interaction of stationary traveling crossflow instability three-dimensional supersonic boundary layers over a swept biconvex wing with blunt leading edge are numerically investigated for freestream Mach number 3. steady unsteady flow fields obtained by solving the full Navier-Stokes equations. layer to surface roughness, acoustic waves, vorticity waves investigated. initial amplitudes vortices generated 1 micron roughness elements is about 2000 times larger than...