Engineering topics

Lowe, K. Todd

Publications and source records attributed to Lowe, K. Todd.

5 records

NASA NTRS2019

Space Launch System Booster Separation Supersonic Powered Testing with Surface and Off-Body Measurements

A wind tunnel test was run in the NASA Langley Unitary Plan Wind Tunnel simulating the separation of the two solid rocket boosters (SRB) from the core stage of the NASA Space Launch System (SLS). The test was run on a 0.9% scale model of the SLS Block 1B Cargo (27005) configuration and the SLS Block 1B Crew (28005) configuration at a Mach of 4.0. High pressure air was used to simulate plumes from the booster separation motors located at the nose and aft skirt of the two boosters. Force and moment data were taken on both SRBs and on the core stage. Schlieren still photos and video were recorded throughout testing. A set of points were acquired using Cross-correlation Doppler Global Velocimetry (CCDGV) readings to get 3 component velocity measurements between the core and the left-hand SRB. The CCDGV laser was utilized to record flow visualization in the same location, between the core and the left-hand SRB. Pressure Sensitive Paint data were taken on a separate set of runs. Computational Fluid Dynamics (CFD) runs were computed on a subset of the wind tunnel data points for comparison. A combination of the force/moment, CCDGV and Pressure Sensitive Paint (PSP) data (as well as schlieren images) at the CFD-specified test conditions will be used te the CFD simulations that will be used to build an SLS booster separation database flight conditions.

Winski, Courtney S.↗

NASA NTRS2019

Laser Light Sheet Flow Visualization of the Space Launch System Booster Separation Test

Planar flow visualizations were obtained in a wind tunnel test in the NASA Langley Research Center’s Unitary Plan Wind Tunnel using the laser-light-sheet method. This method uses a laser to illuminate fine particles generated in the wind tunnel to visualize flow structures. The test article was designed to simulate the separation of the two solid rocket boosters (SRBs) from the core stage of the NASA Space Launch System (SLS) at Mach 4 using a scale model. The test was run on of the SLS Block 1B Cargo (27005) configuration and the SLS Block 1B Crew (28005) configuration. Planar flow visualization was obtained only on the crew configuration. Air at pressures up to 1500 psi was used to simulate plumes from the booster separation motors (BSMs) located at the nose, and aft skirt of the two boosters. The facility free stream was seeded with water vapor, which condensed and froze into small ice crystals in the tunnel nozzle expansion. A continuous wave green (532 nm) laser sheet was used to illuminate the ice crystals, and the resulting Mie-scattered light was collected with a camera. The resulting images clearly identify shock waves and other flow features including BSM plume shapes. Measurements were acquired for different BSM pressures and booster separation locations.

Danehy, Paul M.↗

NASA NTRS2016

Velocity Statistics and Spectra in Three-Stream Jets

Velocimetry measurements were obtained in three-stream jets at the NASA Glenn Research Center Nozzle Acoustics Test Rig using the time-resolved Doppler global velocimetry technique. These measurements afford exceptional frequency response, to 125 kHz bandwidth, in order to study the detailed dynamics of turbulence in developing shear flows. Mean stream-wise velocity is compared to measurements acquired using particle image velocimetry for validation. Detailed results for convective velocity distributions throughout an axisymmetric plume and the thick side of a plume with an offset third-stream duct are provided. The convective velocity results exhibit that, as expected, the eddy speeds are reduced on the thick side of the plume compared to the axisymmetric case. The results indicate that the time-resolved Doppler global velocimetry method holds promise for obtaining results valuable to the implementation and refinement of jet noise prediction methods being developed for three-stream jets.

Three-Stream Jets↗

NASA NTRS2015

Particle Image Velocimetry Applications Using Fluorescent Dye-Doped Particles

Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). These particles may be doped with fluorescent dyes such that signals spectrally shifted from the incident laser wavelength may be detected via Laser Induced Fluorescence (LIF). An attractive application of the LIF signal is achieving velocimetry in the presence of strong interference from laser scatter, opening up new research possibilities very near solid surfaces or at liquid/gas interfaces. Additionally, LIF signals can be used to tag different fluid streams to study mixing. While fluorescence-based PIV has been performed by many researchers for particles dispersed in water flows, the current work is among the first in applying the technique to micron-scale particles dispersed in a gas. A key requirement for such an application is addressing potential health hazards from fluorescent dyes; successful doping of Kiton Red 620 (KR620) has enabled the use of this relatively safe dye for fluorescence PIV for the first time. In this paper, basic applications proving the concept of PIV using the LIF signal from KR620-doped particles are exhibited for a free jet and a twophase flow apparatus. Results indicate that while the fluorescence PIV techniques are roughly 2 orders of magnitude weaker than Mie scattering, they provide a viable method for obtaining data in flow regions previously inaccessible via standard PIV. These techniques have the potential to also complement Mie scattering signals, for example in multi-stream and/or multi-phase experiments.

Petrosky, Brian J.↗

NASA NTRS2013

Characterization of Fluorescent Polystyrene Microspheres for Advanced Flow Diagnostics

Fluorescent dye-doped polystyrene latex microspheres (PSLs) are being developed for velocimetry and scalar measurements in variable property flows. Two organic dyes, Rhodamine B (RhB) and dichlorofluorescence (DCF), are examined to assess laser-induced fluorescence (LIF) properties for flow imaging applications and single-shot temperature measurements. A major interest in the current research is the application of safe dyes, thus DCF is of particular interest, while RhB is used as a benchmark. Success is demonstrated for single-point laser Doppler velocimetry (LDV) and also imaging fluorescence, excited via a continuous wave 2 W laser beam, for exposures down to 10 ms. In contrast, when exciting with a pulsed Nd:YAG laser at 200 mJ/pulse, no fluorescence was detected, even when integrating tens of pulses. We show that this is due to saturation of the LIF signal at relatively low excitation intensities, 4-5 orders of magnitude lower than the pulsed laser intensity. A two-band LIF technique is applied in a heated jet, indicating that the technique effectively removes interfering inputs such as particle diameter variation. Temperature measurement uncertainties are estimated based upon the variance measured for the two-band LIF intensity ratio and the achievable dye temperature sensitivity, indicating that particles developed to date may provide about +/-12.5 C precision, while future improvements in dye temperature sensitivity and signal quality may enable single-shot temperature measurements with sub-degree precision.

Maisto, Pietro M. F.↗