Search NASA⌕ Search

SEARCH · Search NASA

Results for “Pressure-Sensitive Paint”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

102 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Cross-Validation of Computational and Experimental Distributed Surface Pressures on the Space Launch System

This paper presents a new workflow for comparing experimental pressure-sensitive paint (PSP) data to computational fluid dynamic (CFD) simulations by way of mapping data from corresponding grids utilizing interpolation methods. In addition to generating quantitative and qualitative point-to-point comparisons between PSP and CFD data, this workflow extracts sectional loading data from both grids and generates lineload comparison charts for corresponding PSP and CFD runs. Experimental PSP data presented in this paper were taken from a 2016 NASA Ames Research Center Unitary Plan Wind Tunnel 11- by 11-Foot Transonic WindTunnel Facility test of the NASA Space Launch System. CFD simulation data for comparison purposes were generated using the FUN3D code. Overall, interpolation onto PSP grids versus CFD grids yields comparable surface pressure fields. However, lineload comparisons are easier to make on the CFD grid-mapped data due to the grid topology and the current capabilities of the lineload analysis tools at NASA Langley Research Center. This workflow is written using contemporary software (Python, Tecplot, PyTecplot), is compatible with existing tools at NASA Langley, and is developed to be adaptable depending on the situation.

SLS↗
NASA NTRSDate not supplied

SLS AUAT uPSP Pressure-Time History video

The attached video (auat-132803-60fps-aligned.mov) is a flow visualization showing pressure-time histories on the SLS Block 1B model. Experimental data was collected Dec 2017 using unsteady pressure-sensitive paint.

uPSP↗
NASA NTRSDate not supplied

Integration of CFD and Wind-Tunnel Testing at NASA

The debate over when wind-tunnel testing will be replaced by Computational Fluid Dynamics (CFD) comes and goes. More recently, however, the debate has subsided with a more collaborative spirit between practitioners of these two disciplines. Combining these complementary disciplines has led to significant improvements in both as well as better understanding of aero- and fluid dynamics. Also, as CFD codes become more accurate, the need for comparisons with experimental data has increased. New measurement techniques, pressure-sensitive paint and off-body velocity measurements for example, have provided detailed, high-quality data for the comparisons. In-tunnel CFD simulations are also providing more direct comparisons between predicted and measured flows. Given this newenvironment, a concerted effort is now underway to facilitate in-tunnel CFD for the 12 major wind tunnels operated by NASA.The Aerosciences Evaluation and Test Capabilities Portfolio (AETC) manages the major aerodynamic ground-testing facilities within NASA. This group is responsible for the operation, maintenance, and improvement of the wind-tunnel facilities and their capabilities. AETC has recently added a project to integrate CFD and wind-tunnel testing to better support customers of the NASA wind tunnels and to better understand the flow in the wind tunnels themselves. Being able to perform CFD simulations of wind-tunnel models in the wind tunnel environment providesthe cleanest way to assess the accuracy of the simulations relative to test data. AETC plans to provide accurate geometry and guidance to wind-tunnel customers who request it, to facilitate in-tunnel simulations. How this effort got started will be presented along with the status and plans for the project.

CFD↗
NASA NTRSDate not supplied

Implementation of the Lifetime Method in uPSP Measurements

At NASA Ames Research Center, unsteady pressure-sensitive paint (uPSP) measurements are obtained using the ‘intensity method’ which measures paint luminescence in response to a continuous, constant excitation. These measurements are obtained using high-speed cameras and are processed into fluctuating components of pressure. However, the nature of the intensity method also requires a separate steady state (time mean) pressure measurement to be obtained. This steady state measurement has typically been obtained using a separate set of PSP equipment that uses the ‘lifetime method’, which uses pulsed excitation to measure paint decay lifetime. If the lifetime method were implemented in the high-speed uPSP system, both the fluctuating and mean components of pressure could be obtained with a single system. This would greatly streamline setup, operations, and processing. In this paper, we describe work performed at the Fluid Mechanics Laboratory at NASA Ames to implement the lifetime method in our uPSP system. The uPSP acquisition system uses Phantom v2512 high-speed cameras, and it was initially uncertain if results of adequate quality could be obtained - their high framerate comes at the cost of several undesirable characteristics, which are explored in this paper. It was also uncertain if illumination using LED lamps, rather than a stronger source such as lasers, would be adequate. The data acquisition and data processing are discussed and the results analyzed. It was found that satisfactory lifetime method results can indeed be obtained using these high-speed cameras and LED lamps. This will allow the uPSP system to be greatly simplified and will have a large operational impact on how uPSP data is acquired in future wind tunnel tests.

Pressure Sensitive Paint↗
NASA NTRS2023

Users' Guide to Vinci: Personal Computer Software for Planning Image-based Measurements in Wind Tunnels

Vinci is software that can be used to plan image-based measurements in wind tunnels. It allows the user to plan the placement of cameras and the choice of lenses well in advance of a test, thereby reducing the set-up time and cost when tunnel occupancy begins. It can also be used post-test to display data (pressure-sensitive paint, particle image velocimetry, model deformation) in context with the test article. Vinci is self-contained and runs on personal computers under Windows operating systems. No other software is required. Test articles are represented by CFD-like surface grids that may be read from an external file or created within the program as a combination of simple geometric shapes. The user controls the position and orientation of the test article through a Graphical User Interface (GUI) and may add many additional objects, including tunnel walls and windows, a wide variety of simple geometric shapes, mirrors, lamps, and laser sheets. The application computes simulated images from up to 40 cameras. Images are based on pinhole projection. Each camera is defined by the sensor size and the focal length of the lens. All camera parameters, including position and point angles, are controlled through the GUI. Simulated images are displayed in a window of the GUI and may be saved as bitmaps.

Users’ Guide, Image Planning, Wind Tunnels, Softwa↗
NASA NTRSDate not supplied

Comparison of OVERFLOW Computational and Experimental Results for a Blunt Mars Entry Vehicle Concept During Supersonic Retropropulsion

Simulations of supersonic retropropulsion (SRP) flow over a Hypersonic Inflatable Aerodynamic Decelerator (HIAD) blunt-body vehicle were performed using the Overflow Computational Fluid Dynamics (CFD) solver. Simulation conditions and geometry were designed to match specific test runs in the Descent System Study (DSS) testing campaign. The relative accuracy of simulation predictions are assessed by direct comparison to experimental data. Computational predictions of the SRP flowfield and bow shock shape are compared to experimental schlieren images. Comparisons of the model surface pressure environment are presented for unsteady and static discrete tap data as well as time-averaged Pressure-Sensitive Paint (PSP) data.

Supersonic Retropropulsion↗
NASA NTRSDate not supplied

Comparison of OVERFLOW Computational and Experimental Results of the CobraMRV Mars Entry Vehicle Concept during Supersonic Retropropulsion

The CFD solver Overflow was used to simulate the CobraMRV undergoing supersonic retropropulsion (SRP) in the Langley Unitary Plan Wind Tunnel as part of a CFD and wind tunnel integration effort. Selection of numerical methods and resulting comparisons to selected tunnel conditions of interest are detailed. Comparisons of mean pressures with static taps and pressure-sensitive paint are provided for multiple SST-based turbulence models. URANS predicitons of heat shield pressures at high thrust conditions are poor compared to TMRC and DES predictions. Comparisons to experimental measurements of pressure fluctuations indicate complex relationships between heat shield unsteadiness, flight Mach number, and engine thrust coefficient. Bow shock topology and shock cell structure between experimental and OVERFLOW data show good agreement in Schlieren imaging. Recommendations for future investigation into flow field unsteadiness and turbulence models are suggested.

CFD↗
NASA NTRSDate not supplied

Steady Surface Pressure Measurement via the Lifetime Method With High-Speed Cameras in NASA's Unitary Plan Wind Tunnel

High spatial resolution measurement of steady surface pressure via pressure-sensitive paint at NASA Ames has traditionally relied on specialized cameras equipped to accumulate charge over multiple exposures, whereas measurement of the fluctuating component of pressure uses an altogether separate set of high-speed cameras. To reduce complexity of installation, data acquisition, and processing, we have implemented methods to use a single set of commercial off-the-shelf cameras to produce both steady and unsteady pressure measurements. Both imaging systems were installed in the 11-by 11-foot NASA Ames Unitary Plan Wind Tunnel and acquired images of a scaled model of the Space Launch System Block 1B Crew and Cargo configurations over a variety of flow conditions. This work focuses on methods for data acquisition, processing, and calibration to produce steady-state pressure estimates on the surface of the wind tunnel model based on the lifetime method. It will then compare the steady solutions produced by the legacy and high-speed imaging systems.

Pressure Sensitive Paint↗
NASA NTRSDate not supplied

Invited: uPSP Launch Vehicle Demonstration Test at NASA Ames Research Center

The Unsteady Pressure-Sensitive Paint (uPSP) Development Team outof NASA Ames Research Center (ARC) has spent the past five yearsimproving the systems and processes to advance the uPSP technology for production-level wind tunnel testing. Already considered turnkey for small-scale and research applications, development in acquisition, calibration, data transfer, and data processing were needed to be useful to customers testing at NASA wind tunnels. This development focused at ARC at the Unitary Plan Wind Tunnel (UPWT) 11-by 11-ft Transonic Wind Tunnel due to the large optical access of the test section and the NASA Advanced Supercomputer(NAS), also located at ARC. A Launch Vehicle Demonstration Test (LVDT) at the UPWT represents a milestone of this initial phase of development where several new improvements were demonstrated in a production wind tunnel environment for the first time. LVDT was conducted in April 2024 and used a 4% forebody Space Launch System (SLS) Block 1B model as the test article. Both a crew and cargo configuration were tested, with varying Mach numbers, pressures, model positions, and camera magnifications. This paper summarizes the details of the test and is part of a collection with four additional papers that provide greater detail on: high-speed lifetime methodology, spectral proper orthogonal decomposition analysis, quality of high-resolution data compared to Corcos model, and data quality, calibration, and uncertainty.

SLS↗