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Results for “boundary-layer transition”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1957

Preliminary Note on a Correlation of a Boundary-Layer Transition Results on Highly Cooled Blunt Bodies

Transition data on highly cooled blunt bodies are correlated in terms of the ratio of wall to local-stream enthalpy, Reynolds number based on displacement thickness, and location of transition. The proposed correlation, although not sensitive enough to predict the exact location of transition does predict the enthalpy ratio below which very early transition on blunt bodies is expected. The correlation is not altered by moderate amounts of surface roughness; however, the location of transition may well be affected by roughness.

Wisniewski, Richard J.↗
NASA NTRS1951

Comparison of Theoretical and Experimental Heat-Transfer Characteristics of Bodies of Revolution at Supersonic Speeds

An investigation of the three important factors that determine convective heat-transfer characteristics at supersonic speeds, location boundary-layer transition, recovery factor, and heat-transfer parameter has been performed at Mach numbers from 1.49 to 1.18. The bodies of revolution that were tested had, in most cases, laminar boundary layers, and the test results have been compared with available theory. Boundary-layer transition was found to be affected by heat transfer. Adding heat to a laminar boundary layer caused transition to move forward on the test body, while removing heat caused transition to move rearward. These experimental results and the implications of boundary-layer-stability theory are in qualitative agreement.

Scherrer, Richard↗
DOE OSTI2025

Assessment and Improvement of the SST-Gamma Transition Model in Nalu-Wind

We conduct laminar–turbulent boundary-layer transition simulations using a local correlation-based transition model for two-dimensional incompressible flow and present enhancements to improve the accuracy of transition predictions. Menter’s Galilean-invariant 𝛾 transition model is implemented in the incompressible, unstructured-grid flow solver Nalu-Wind and is validated against experimental data and results from NASA’s flow solvers. The test cases of the AIAA Transition Prediction and Modeling Workshop are investigated, namely, the T3A/T3B flat plates and the NLF(1)-0416 and S809 airfoils. Based on the results, best practices for transition simulations, particularly for an unstructured-grid flow solver, are identified. Additional airfoil simulations are conducted for two wind turbine airfoils, S822 at Reynolds numbers of 𝑂⁡(10 5 ) and DU00-W-212 at Reynolds numbers of 𝑂⁡(10 7 ), to assess the model at low and high Reynolds numbers. Furthermore, through this work, we propose several approaches to enhance transition simulations, including 1) enforcing positivity of the implicit operator for the source terms of the transition model, 2) employing a constant turbulence intensity in stationary external flow simulations, and 3) recommending meshing for unstructured-grid flow solvers. Finally, we provide detailed documentation of the validation and data for the canonical cases to the transition modeling community.

17 WIND ENERGY↗
NASA NTRS1952

Experimental Study of the Effects of Finite Surface Disturbances and Angle of Attack on the Laminar Boundary Layer of an NACA 64A010 Airfoil with Area Suction

A Langley low-turbulence wind-tunnel investigation of a porous NACA 64A010 airfoil section has been made to determine the effectiveness of area suction in maintaining full-chord laminar flow behind finite disturbances and at angles of attacks other than 0 degrees. Aero suction resulted in only a small increase in the size of a finite disturbance required to cause premature boundary-layer transition as compared with that for the airfoil without suction. Combined wake and suction drags lower than the drag of the plain airfoil were obtained through a range of low lift coefficient by the use of area suction.

FLOW, LAMINAR↗
NASA NTRS1948

Maintaining Laminar Flow in the Boundary Layer using a Swept-Back Wing

The positions of boundary-layer transition were ascertained experimentally for a swept-back wing and a wing without sweepback which were alike in all other respects and were compared for the same angle of attack (R(sub e) = 5.6 x 10(exp 5)). The swept-back wing in a definite range of angle of attack resulted in a backward shift of the transition point on the suction side of the wing. The favorable effect of sweepback on the position of the transition point is confirmed, consequently. In addition to decreasing the drag at high Mach numbers, the swept-back wing is acknowledged to have additional advantages. These are: (1) Decrease of the pressure drag. The reduction factor is approximately equal to the cosine of the angle of sweepback. (2) Backward shift of the transition point. There are no known experiments which establish experimentally the advantage anticipated. It appeared justifiable, therefore, to carry out some fundamental experiments which might furnish some idea of the magnitude of the advantage expected. Such an experiment is reported in what follows; the advantage of the sweepback appears clearly.

Brennecke↗
NASA NTRSDate not supplied

Material Properties and Modeling of Room Temperature Vulcanizing Silicone

Room Temperature Vulcanizing silicone (RTV) is a high-temperature adhesive that has successfully been used as a gap-filler between Thermal Protection System (TPS) tiles for heatshields on numerous missions. It is also used to bond instrumentation plugs such as temperature and pressure sensors into the heatshields. While RTV has been traditionally assumed to be a non-porous and non-ablating material, numerous experiments have shown that RTV pyrolyzes and becomes highly porous as it is heated. Heating RTV has also shown swelling, or intumescence, which can pose unique problems that lead to roughness induced boundary-layer transition, surface oxide formation and contamination of heat shield sensors. Therefore, it is crucial to understand and model the intumescence phenomenon of RTV. As data for RTV material properties is limited, the first step in modeling RTV is to collect material properties such as pyrolysis mass-loss, microstructure change, virgin and char porosity, etc. which was performed in our initial study. Additionally, thermomechanical properties such as Young’s modulus and Poisson ratio are required for modeling the intumescence of RTV, which were taken from literature and the coefficient of thermal expansion was collected using in-situ heating and Micro Computed Tomography (µ-CT) in previous studies. Finally, numerous other properties such as pyrolysis gas properties, virgin and char thermal conductivity and specific heat were compiled from previous experiments and literature into a material database that can be used for simulations. In Porous Material Analysis Toolbox based on OpenFOAM (PATO) [4], structural mechanics coupled with material response was used for simulating the intumescence of RTV as it is heated. However, since the permeability of the material is very low, the pyrolysis gas creates an internal pressure build-up as the material is being heated, significantly contributing to the deformation of the material. To correctly characterize this phenomenon, additional physics models were implemented into PATO's stress analysis solver, and results were compared with RTV dilatometry test data as a preliminary verification case. Future work will include experiments of RTV at the Plasmatron X facility and the in-situ heating cell with µ-CT, and improvement of simulation tools to more accurately model RTV intumescence.

PATO↗
NASA NTRS1990

Theory on instability and transition

The fundamental fluid dynamics governing instability and transition to turbulence in boundary layers are considered, and attention is focused on the key aspects of nonlinear dynamics central to the transition process and to turbulent boundary-layer phenomena. Emphasis is placed on truly nonlinear theories, in which the boundary layer mean-flow profile is completely altered from its original form. Nonlinear TS transitions, Euler-stage interactions, and vortex/wave interactions are discussed, and compressible boundary layers are analyzed. Connections with experiments and computations are outlined, along with overall trends including the extension of the nonlinear theory and the advancement in the compressible and other flow regimes.

Smith, Frank T.↗
NASA NTRS1941

Tests of the NACA 0025 and 0035 Airfoils in the Full-Scale Wind Tunnel

This report presents the results of an investigation conducted in the NACA full-scale wind tunnel to determine the aerodynamic characteristics of the 6 by 36-foot rectangular NACA 0025 and 0035 airfoils. The aerodynamic characteristics of the plain airfoils with rounded and square tips were determined by force tests through a complete angle-of-attack range, in addition, the profile drag was determined by the momentum method. The transition points on the airfoils were located by boundary-layer determinations with small total-head and static tubes. Each airfoil was also tested with a 0.20c full-span split flap. Tuft surveys were included to show the progressive breakdown of flow with increasing angles of attack. Previously published data from tests of the NACA 0009, 0012, and 0018 airfoils in the full-scale tunnel have been included in the summary curves.

Bullivant, W Kenneth↗
DOE OSTI2026

Zooming in: SCREAM at 100 m using regional refinement over the San Francisco Bay Area

Pushing global climate models to large-eddy simulation (LES) scales over complex terrain has remained a major challenge. This study presents the first known implementation of a global model – SCREAM (Simple Cloud-Resolving E3SM Atmosphere Model) – at 100 m horizontal resolution using a regionally refined mesh (RRM) over the San Francisco Bay Area. Two hindcast simulations were conducted to test performance under both strong synoptic forcing and weak, boundary-layer-driven conditions. We demonstrate that SCREAM can stably run at LES scales while realistically capturing topography, surface heterogeneity, and coastal processes. The 100 m SCREAM-RRM substantially improves near-surface wind speed, temperature, humidity, and pressure biases compared to the baseline 3.25 km simulation, and better reproduces fine-scale wind oscillations and boundary-layer structures. These advances leverage SCREAM's scale-aware SHOC turbulence parameterization, which transitions smoothly across scales without tuning. Performance tests show that while CPU-only simulations remain costly, GPU acceleration with SCREAMv1 on NERSC's Perlmutter system enables two-day hindcasts to complete in under two wall-clock days. Our results open the door to LES-scale studies of orographic flows, boundary-layer turbulence, and coastal clouds within a fully comprehensive global modeling framework.

Geosciences↗
DOE OSTI2026

Land-Surface Temperature Transitions at the Bankhead National Forest (LASTT-BNF) Field Campaign Report

Land surface types that are common in the Southeast United States (e.g., forests, agriculture, urban) can play key roles in the regulation of surface-atmosphere energy exchange and boundary-layer evolution in the region (Hinkle et al. 2024). Heterogeneity in these land-surface types and associated emissivities can drive strong transitions in land surface temperature (LST), which is an important component of the surface energy balance. Within the forested canopy surrounding the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) User Facility’s field deployment at the Bankhead National Forest (BNF) in Alabama main site (M1) (Kuang et al. 2026), the different components of the vegetation and ground surface can create strong gradients in surface temperature that can influence the canopy thermal environment and vegetative function (e.g., stress, transpiration), both of which can have important, yet poorly characterized, controls on lower atmospheric processes (e.g., thermal turbulence, secondary circulations).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

A robust aerosol impact on clouds along the subtropical to tropical transition

Marine clouds undergo a transition from subtropical stratocumulus (Sc) to shallow cumulus (Cu) and eventually to deep convective (DC) systems as air masses advect from the subtropics towards the deep tropics. How aerosols modulate this Lagrangian cloud evolution remains largely uncertain. Here we use both 5 years of satellite observations mapped along 8 d Lagrangian trajectories and complementary large-eddy simulations from 9 initiation locations across the Northeast Pacific, Southeast Pacific, and Southeast Atlantic. This Lagrangian framework allows us to quantify the aerosol effect and its co-variability with meteorological conditions on cloud microphysics, macrophysics, and top-of-atmosphere radiation through the full Sc-Cu-DC transition. We show that increasing aerosol concentrations leads to deeper and more reflective clouds throughout this cloud transition. Examining the thermodynamic evolution along the trajectory indicates a well-known trend: enhanced moistening near the boundary-layer top and lower free troposphere under polluted conditions, suggesting that part of the co-variability between aerosol and meteorological conditions may be internally driven. The agreement between model simulations and satellite data alongside the multi-basin coherence of the results indicates that aerosols systematically amplify cloud depth and reflectivity during the subtropical–to–tropical cloud transition.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1936

Behavior of turbulent boundary layers on curved convex walls

The system of linear differential equations which indicated the approach of separation and the so-called "boundary-layer thickness" by Gruschwitz is extended in this report to include the case where the friction layer is subject to centrifugal forces. Evaluation of the data yields a strong functional dependence of the momentum change and wall drag on the boundary-layer thickness radius of curvature ratio for the wall. It is further shown that the transition from laminar to turbulent flow occurs at somewhat higher Reynolds Numbers at the convex wall than at the flat plate, due to the stabilizing effect of the centrifugal forces.

Schmidbauer, Hans↗
NASA NTRS1939

Comparison of Profile-drag and Boundary-layer Measurements Obtained in Flight and in the Full-scale Wind Tunnel

The effect of the existing turbulence in the full scale tunnel was determined from measurements of the profile drag of an N-22 section by the momentum method under corresponding conditions in flight and the tunnel. The transition-point location on the upper surface of the air-foil was also determined from velocity surveys in the boundary layer. The measurements were made at section lift coefficients from 0.480 to 0.635 with a range of Reynolds Numbers from 4,600,000 to 3,900,000. The results show that the end of transition occurs at approximately the same point on the airfoil in flight and in the tunnel. The transition region was somewhat broader in the tunnel and started farther forward than in flight. The laminar profiles in the tunnel had some characteristics of transition profiles in the tunnel and had a much steeper slope near the surface than did the laminar profiles obtained in flight. These differences, however, caused an increase of only 0.0001 in the profile-drag coefficients, as determined by the momentum method.

Goett, Harry J↗
DOE OSTI2026

CAPE-K_ISO: Water vapor isotopic measurements from Western Tasmania

This dataset provides processed 1-minute water vapor isotope observations from the Water Vapor Isotopic Measurements During CAPE-K project at the Kennaook/Cape Grim Baseline Air Pollution Station in northwestern Tasmania. Measurements were made with a Picarro L-2130 cavity ring-down spectroscopy analyzer during the CAPE-K deployment. The dataset includes water vapor mixing ratio, d18O, dD, deuterium excess, and propagated 1-sigma uncertainties. Isotope ratios are calibrated to the VSMOW/SLAP scale. Calibration intervals, transition periods, and obvious isotope outliers have been removed. The processed record spans 11 June 2024 to 15 October 2025 and is intended for studies of Southern Ocean marine boundary-layer moisture, isotope variability, air-sea exchange, and cloud and precipitation processes.

Water Vapor Isotopic Composition↗