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The NASA Open Science Data Repository: Biomedical Data, Analysis Tools, and Informatic Collaborations

Increased biomedical risks and challenges associated with deep space missions require knowledge discovery, health countermeasures, and biomedical support capabilities. Maximally open-access and reusable data is needed by developers, scientists, and engineers to develop these systems. The NASA Open Science Data Repository (OSDR) is a maximally open access and FAIR database (ie., findable, accessible, interoperable, and reusable), and meets various scientific, technical, and operational needs. It offers users and submitters the ability to upload, download, search, share, analyze, cite, and visualize data across ‘omics, physiological, phenotypic, payload, hardware, behavioral, bioimaging, video, and environmental monitoring telemetry datasets. OSDR is an expanded database, based upon the successes of NASA GeneLab. OSDR has >460 studies with datasets covering model organisms to non-NASA human astronauts. There are ~12 datasets from the Inspiration 4 (I4) mission, spanning metagenomics, comprehensive metabolic panels, clonal hematopoiesis, spatial transcriptomics, proteomics, and cytokine panels. In the interest of data privacy, two I4 datasets with raw files relating to the epitranscriptome, and a new request feature is live in OSDR (with a backend review process established) developed from industry norms. OSDR is collecting and curating biomedical human data from a new sub-orbital research flight and is open to more space life science/biomedical submissions from the international and commercial sectors. OSDR also recently began a collaboration with the European Space Agency (ESA) to collect and curate >200 terabytes of human and model organism data. The OSDR submission portal is designed to ingest and curate ~25 ‘omics and ~50 physiological-phenotypic-imaging assay data types. Tools available for OSDR users include: 1) an Environmental Data Application to compare radiation, CO2, relative humidity, temperature, and other telemetry across missions and subjects, 2) the RadLab database, a collaboration between NASA, ESA, the German and Italian Space Agencies, and the Bulgarian Academy of Sciences, and 3) a Multi-study visualization tool which enables users to look across and combine ‘omics datasets. There are ~600 volunteer OSDR Analysis Working Group (AWG) members providing feedback on scientific data/metadata standards and collaborating to mine-reuse OSDR in research. OSDR/GeneLab has enabled ~60 publications reusing data as of October 2023.

space biology↗
NASA NTRS1992

Habituation and adaptation of the vestibuloocular reflex: a model of differential control by the vestibulocerebellum

We habituated the dominant time constant of the horizontal vestibuloocular reflex (VOR) of rhesus and cynomolgus monkeys by repeated testing with steps of velocity about a vertical axis and adapted the gain of the VOR by altering visual input with magnifying and reducing lenses. After baseline values were established, the nodulus and ventral uvula of the vestibulocerebellum were ablated in two monkeys, and the effects of nodulouvulectomy and flocculectomy on VOR gain adaptation and habituation were compared. The VOR time constant decreased with repeated testing, rapidly at first and more slowly thereafter. The gain of the VOR was unaffected. Massed trials were more effective than distributed trials in producing habituation. Regardless of the schedule of testing, the VOR time constant never fell below the time constant of the semicircular canals (approximately 5 s). This finding indicates that only the slow component of the vestibular response, the component produced by velocity storage, was habituated. In agreement with this, the time constant of optokinetic after-nystagmus (OKAN) was habituated concurrently with the VOR. Average values for VOR habituation were obtained on a per session basis for six animals. The VOR gain was adapted by natural head movements in partially habituated monkeys while they wore x 2.2 magnifying or x 0.5 reducing lenses. Adaptation occurred rapidly and reached about +/- 30%, similar to values obtained using forced rotation. VOR gain adaptation did not cause additional habituation of the time constant. When the VOR gain was reduced in animals with a long VOR time constant, there were overshoots in eye velocity that peaked at about 6-8 s after the onset or end of constant-velocity rotation. These overshoots occurred at times when the velocity storage integrator would have been maximally activated by semicircular canal input. Since the activity generated in the canals is not altered by visual adaptation, this finding indicates that the gain element that controls rapid changes in eye velocity in the VOR is separate from that which couples afferent input to velocity storage. Nodulouvulectomy caused a prompt and permanent loss of habituation, returning VOR time constants to initial values. VOR gain adaptation, which is lost after flocculectomy, was unaffected by nodulouvulectomy. Flocculectomy did not alter habituation of the VOR or of OKAN. Using a simplified model of the VOR, the decrease in the duration of vestibular nystagmus due to habituation was related to a decrement in the dominant time constant of the velocity storage integrator (1/h0).(ABSTRACT TRUNCATED AT 400 WORDS).

NASA Discipline Neuroscience↗
NASA NTRS1973

Experiment M-131 - Human vestibular function.

The purpose of the M-131 experiment is to measure responses in astronauts throughout orbital flight that reflect vestibular function and compare them with measurements made before and after flight. Three subtasks require measurement of (1) susceptibility to motion sickness, (2) thresholds of response to stimulation of the semicircular canals, and (3) space perception, viz, visual and nonvisual localization, using external spacecraft and internal morphological frames of reference. Four astronauts will be available for all measurements in Skylab 2 and 3 and two additional astronauts for only the 'static' measurements during the flights.

Miller, E. F., II↗
NASA NTRS1974

Sensor performance evaluation of the Skylab multispectral photographic facility

Results of resolution tests for multispectral imagery from Skylabs 2, 3, and 4 are presented. Methods employed were visual edge matching and edge slope analysis, and resolution was evaluated as a function of spectral band, EREP pass, target orientation, field of view, exposure, and contrast. Preflight and postflight image quality data were compared. The multispectral image quality has equaled or slightly exceeded design predictions.

Corbett, F. J.↗
NASA NTRS1981

Natural sunlight accelerated weathering of photovoltaic modules

Photovoltaic modules are exposed to the equivalent of ten years of sunlight aging in an accelerated exposure testing and evaluation program, the objective being to determine the long-term durability characteristics of flat plate modules in comparatively short periods of time. The modules are illuminated with concentrated sunlight in a large, sun-tracking, Fresnel-reflecting solar concentrator. The effects of the accelerated exposure are assessed by performing periodic visual inspections and electrical measurements. It is found that field-experienced failure modes are duplicated, that acceleration factors of 6x to 8x are readily attainable, and that the test method is feasible as a predictive tool for photovoltaic module lifetime durability.

Zerlaut, G. A.↗
NASA NTRS1983

Detection and recognition of simple spatial forms

A model of human visual sensitivity to spatial patterns is constructed. The model predicts the visibility and discriminability of arbitrary two-dimensional monochrome images. The image is analyzed by a large array of linear feature sensors, which differ in spatial frequency, phase, orientation, and position in the visual field. All sensors have one octave frequency bandwidths, and increase in size linearly with eccentricity. Sensor responses are processed by an ideal Bayesian classifier, subject to uncertainty. The performance of the model is compared to that of the human observer in detecting and discriminating some simple images.

Watson, A. B.↗
NASA NTRS1991

Investigations into the damage for various types of unprotected carbon fibre composites with a variety of lightning arc attachments

Very little quantitative information exists on the extent and nature of damage caused to unprotected carbon fiber composites (CFC's) due to lightning arc attachment. An initial investigation into the arc damage to three different types and various thickness of CFC's from A and C component type lightning discharges is described. The difference in damage which the two types of waveform produced and the way the area of damage varies with different levels of action integral and charge transfer is compared. In some cases, the temperature rise at the rear of the panels was recorded for various levels of action integral and charge transfer. A comparison was made of the area of damage from visual inspection and soft x ray photography, using a suitable penetrant in the damage area. It is concluded there is a need for a more detailed analysis of the damage.

Reid, G. W.↗
NASA NTRS1993

Multicolor photometry of x ray selected Abell clusters

Strong evidence of evolution in cluster of galaxies at relatively low redshift has been indicated by recent x-ray studies. We are conducting a comprehensive optical study of a sample of Abell clusters that are strong x-ray emitters in order to test the x-ray evolution scenarios that have been proposed. The initial observations consist of three-color (B, R, I) imaging of low-redshift (0.025 less than z less than 0.25) Abell clusters using the T2KA CCD on the 0.9m telescope at KPNO the large field (23 ft. x 23 ft., approx. 1 Mpc at z = 0.025 and approx. 7 Mpc at z = 0.25) gives the unprecedented ability to sample most of the extent of the field of low-redshift clusters using a CCD. Given the advantages of CCDs over photographic plates, we expect to improve on many of the previous studies. A list of x-ray selected cluster of galaxies provides a homogeneous sample of true clusters that cannot be mistaken from apparent over-densities due to projection effects of field galaxies. Some optical indicators of cluster evolution are the population of ratios of cluster galaxies and their spatial distribution, a regular spiral-poor cluster is expected to be more evolved than an irregular spiral-rich cluster. Also regular spiral-poor clusters present high central concentrations while irregular spiral-rich are less concentrated. Variations in the Luminosity Function (LF) can indicate evolution. But in order to build reliable LFs it is necessary to determine the Hubble types of the cluster galaxies. In the past the classifications of cluster galaxies have been done by visual inspection on photographic material, this technique is very limited and can lead to errors when the galaxies are faint. The Hubble types of cluster galaxies can be determined in an objective manner by comparing colors and profiles from surface photometry. To show that this approach is feasible, I have presented preliminary results from the photometric analysis of the Abell-cluster A1213. Colors and profiles of the surface brightness distribution were compared to determine the Hubble types of the cluster galaxies.

Lopez-Cruz, Omar↗
NASA NTRS1961

Effects of Mach Number, Leading-Edge Bluntness, and Sweep on Boundary-Layer Transition on a Flat Plate

The effects of leading-edge bluntness and sweep on boundary-layer transition on flat plate models were investigated at Mach numbers of 2.00, 2.50, 3.00, and 4.00. The effect of sweep on transition was also determined on a flat plate model equipped with an elliptical nose at a Mach number of 0.27. Models used for the supersonic investigation had leading-edge radii varying from 0.0005 to 0.040 inch. The free-stream unit Reynolds number was held constant at 15 million per foot for the supersonic tests and the angle of attack was 0 deg. Surface flow conditions were determined by visual observation and recorded photographically. The sublimation technique was used to indicate transition, and the fluorescent-oil technique was used to indicate flow separation. Measured Mach number and sweep effects on transition are compared with those predicted from shock-loss considerations as described in NACA Rep. 1312. For the models with the blunter leading edges, the transition Reynolds number (based on free-stream flow conditions) was approximately doubled by an increase in Mach number from 2.50 to 4.00; and nearly the same result was predicted from shock-loss considerations. At all super- sonic Mach numbers, increases in sweep reduced the transition Reynolds number and the amount of reduction increased with increases in bluntness. The shock-loss method considerably underestimated- the sweep effects, possibly because of the existence of crossflow instability associated with swept wings. At a Mach number of 0.27, no reduction in the transition Reynolds number with sweep was measured (as would be expected with no shock loss) until the sweep angle was attained where crossflow instability appeared.

Jillie, Don W.↗
NASA NTRS1999

Neural Networks Used to Compare Designed and Measured Time-Average Patterns

Electronic time-average holograms are convenient for comparing the measured vibration modes of fan blades with those calculated by finite-element models. At the NASA Lewis Research Center, neural networks recently were trained to perform what had been a simple visual comparison of the predictions of the design models with the measurements. Finite-element models were used to train neural networks to recognize damage and strain information encoded in subtle changes in the time-average patterns of cantilevers. But the design-grade finite element models were unable to train the neural networks to detect damage in complex blade shapes. The design-model-generated patterns simply did not agree well enough with the measured patterns. Instead, hybrid-training records, with measured time-average patterns as the input and model-generated strain information as the output, were used to effect successful training.

Decker, Arthur J.↗
NASA NTRS2013

Preliminary Results from the Joint Russian and US Field Test: Measurement of Sensorimotor and Cardiovascular Responses Immediately Following Landing of the Soyuz Spacecraft

Ongoing collaborative research efforts between NASA's Neuroscience and Cardiovascular Laboratories, and the Institute of Biomedical Problems' (IBMP) Sensory-Motor and Countermeasures Laboratories have been measuring functional sensorimotor, cardiovascular and strength responses following bed rest, dry immersion, short duration (Space Shuttle) and long duration (Mir and International Space Station) space flights. While the unloading paradigms associated with dry immersion and bed rest have do serve as acceptable flight analogs, testing of crew responses following the long duration flights does not begin until a minimum of 24 hours after landing. As a result it is not possible to estimate the nonlinear trend of the early (<24 hr) recovery process nor is it possible to accurately assess the full impact of the decrements associated with long duration flight. To overcome these limitations both the Russian and U.S. sides have implemented testing at the time of landing and before the flight crews have left the landing site. By joint agreement this research effort has been identified as the functional Field Test (FT). For practical reasons the FT has been divided into two phases: the full FT and a preliminary pilot version (PFT) of the FT that is reduced in both length and scope. The primary goal of this research is to determine functional abilities in long duration space flight crews beginning as soon after landing as possible (< 2 hr) with one to three immediate follow-up measurements on the day of landing. This goal has both sensorimotor and cardiovascular elements including an evaluation of NASA's new anti-orthostatic compression garment as compared with the Russian Kentavr garment. Functional sensorimotor measurements will include, but are not limited to, assessment of hand/eye coordination, ability to egress from a seated position, walk normally without falling, measurement of dynamic visual acuity, ability to discriminate different forces generated with both the hands and legs, recovery from a fall, a coordinated walk involving tandem heel-to-toe placement and determination of postural ataxia while standing. The cardiovascular portion of the investigation includes blood pressure and heart rate measurements during a timed stand test in conjunction with postural ataxia testing. In addition to the immediate post-landing collection of data for the full FT, postflight data will be acquired at a minimum of one to three more other times within the 24 hr following landing and continue until functional sensorimotor and cardiovascular responses have returned to preflight normative values. The PFT represents a single trial run comprised of jointly agreed tests from the full FT and relies heavily on IBMP's Sensory-Motor and Countermeasures Laboratories for content, and implementation. The PFT is currently scheduled for the September 2013 landing of the Soyuz spacecraft (34S). Testing will include: (1) a sit-to-stand test, (2) recovery from a fall where the crewmember begins in the prone position on the ground and then stands for 3 min while cardiovascular stability is determined and postural ataxia data are acquired, and (3) a tandem heel-to-toe walk to determine changes in the central locomotor program. Video, cardiovascular parameters (heart rate and blood pressure), data from body-worn inertial sensors and severity of postflight motion sickness will be available for analysis. It is our intent to present, at this celebratory symposium, a summary of these data obtained from two crewmembers. In summary, the level of functional deficit is expected to be most profound during the acquisition of gravity loads immediately after landing when the demands for crew intervention in response to emergency operations will be greatest. Clearly measureable performance parameters such as ability to perform a seat egress, recover from a fall or the ability to see clearly when walking, and related physiological data (orthostatic responses) are required to provide an evidence base for characterizing programmatic risks and the degree of variability among crewmembers. Overall, these early functional and related physiological measurements will allow estimation of nonlinear sensorimotor and cardiovascular recovery trends to an accuracy that has not been previously captured in over 50 years of space flight.

Reschke, M. F.↗
NASA NTRS2015

Effects of Angular Frequency During Clinorotation on Mesenchymal Stem Cell Morphology and Migration

Background/Objectives: Ground-based microgravity simulation can reproduce the apparent effects of weightlessness in spaceflight using clinostats that continuously reorient the gravity vector on a specimen, creating a time-averaged nullification of gravity. In this work, we investigated the effects of clinorotation speed on the morphology, cytoarchitecture, and migration behavior of human mesenchymal stem cells (hMSCs). Methods: We compared cell responses at clinorotation speeds of 0, 30, 60, and 75 rpm over 8 hours in a recently developed lab-on-chip-based clinostat system. Time lapse light microscopy was used to visualize changes in cell morphology during and after cessation of clinorotation. Cytoarchitecture was assessed by actin and vinculin staining, and chemotaxis was examined using time lapse light microscopy of cells in NGF (100 ng/ml) gradients. Results: Among clinorotated groups, cell area distributions indicated a greater inhibition of cell spreading with higher angular frequency (p is less than 0.005), though average cell area at 30 rpm after 8 hours became statistically similar to control (p = 0.794). Cells at 75rpm clinorotation remained viable and were able to re-spread after clinorotation. In chemotaxis chambers clinorotation did not alter migration patterns in elongated cells, but most clinorotated cells exhibited cell retraction, which strongly compromised motility.

microgravity↗
NASA NTRS1997

Development of an Antimicrobial Susceptibility Testing Method Suitable for Performing During Space Flight

Very little is known regarding the affects of the microgravity environment of space flight upon the action of antimicrobial agents on bacterial pathogens. This study was undertaken to develop a simple method for conducting antibacterial susceptibility tests during a Space Shuttle mission. Specially prepared susceptibility test research cards (bioMerieux Vitek, Hazelwood, MO) were designed to include 6-11 serial two-fold dilutions of 14 antimicrobial agents, including penicillins, cephalosporins, a Beta-lactamase inhibitor, vancomycin, erythromycin, tetracycline, gentamicin, ciprofloxacin, and trimethoprim/sulfamethoxazole. Minimal inhibitory concentrations (MICS) of the drugs were determined by visual reading of color endpoints in the Vitek research cards made possible by incorporation of a colorimetric growth indicator (alamarBlue(Trademark), Accumed International, Westlake, OH). This study has demonstrated reproducible susceptibility results when testing isolates of Staphylococcus aurezis, Group A Streptococcus, Enterococcusfaecalis, Escherichia coli (beta-lactamase positive and negative strains), Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomoiias aeruginosa. In some instances, the MICs were comparable to those determined using a standard broth microdilution method, while in some cases the unique test media and format yielded slightly different values, that were themselves reproducible. The proposed in-flight experiment will include inoculation of the Vitek cards on the ground prior to launch of the Space Shuttle, storage of inoculated cards at refrigeration temperature aboard the Space Shuttle until experiment initiation, then incubation of the cards for 18-48 h prior to visual interpretation of MICs by the mission's astronauts. Ground-based studies have shown reproducible MICs following storage of inoculated cards for 7 days at 4-8 C to accommodate the mission's time schedule and the astronauts' activities. For comparison, ground-based control (normal gravity) MIC values will be generated by simultaneous inoculation and incubation of a second set of test cards in a laboratory at the launch site. This procedure can provide a safe and compact experiment that should yield new information on the affects of microgravity on the biological activities of various classes of antibiotics.

Jorgensen, James H.↗
NASA NTRS1975

Conspicuity of target lights: The influence of flash rate and brightness

The stimulus characteristics of lights that might aid a pilot to see and avoid, by alerting him to a potential threat were studied. The relative conspicuity of foveally equated, point-source, steady and flashing lights of several brightnesses, seen against a star background was examined. From the subject's viewpoint, these target lights could appear anywhere within a large (40 deg horizontal by 35 deg vertical) field of view. The lights appeared at random time intervals while the subject was periodically distracted by a simulated cockpit task. The results indicate that correct target detection increases and reaction time decreases with increased target intensity. Steady lights are missed more frequently and acquired more slowly than flashing lights, but no significant differences are found among the wide range of flash rates employed. The intensity of the light has a greater effect on both detection and reaction time to steady lights than to flashing lights. These results are compared with results of other researchers who used targets which appeared at fixed locations. The longest reaction times were recorded to lights which appeared either at the extremes or at the very center of the visual field.

Connors, M. M.↗
NASA NTRS1979

Influence of coolant tube curvature on film cooling effectiveness as detected by infrared imagery

Thermal film cooling footprints observed by infrared imagery from straight, curved, and looped coolant tube geometries are compared. It was hypothesized that the differences in secondary flow and in the turbulence structure of flow through these three tubes should influence the mixing properties between the coolant and the main stream. A flow visualization tunnel, an infrared camera and detector, and a Hilsch tube were employed to test the hypothesis.

Papell, S. S.↗
NASA NTRS1989

Infrared imaging and tufts studies of boundary layer flow regimes on a NACA 0012 airfoil

A study of boundary-layer flow regimes on a NACA 0012 airfoil from zero angle of attack up to separation is presented. The boundary-layer transition from the laminar to the turbulent regime and the onset of the separation were detected by surface thermography of the airfoil performed with an infrared imaging system. The findings were compared with observations of aluminum-foil tufts visible with the infrared imaging system. This arrangement allows the infrared imaging system to assume the dual role of flow regime detection through surface thermography and flow visualization through the observation of the aluminum-foil tufts. Ultimately the temperature history on an uncontaminated surface could provide an interpretation of the state of boundary-layer flow. Separation studies performed on the NACA 0012 airfoil showed that aluminum foil tufts can be observed with infrared imaging systems.

Gartenberg, Ehud↗
NASA NTRS1996

Helicopter Rotor Blade Computation in Unsteady Flows Using Moving Overset Grids

An overset grid thin-layer Navier-Stokes code has been extended to include dynamic motion of helicopter rotor blades through relative grid motion. The unsteady flowfield and airloads on an AH-IG rotor in forward flight were computed to verify the methodology and to demonstrate the method's potential usefulness towards comprehensive helicopter codes. In addition, the method uses the blade's first harmonics measured in the flight test to prescribe the blade motion. The solution was impulsively started and became periodic in less than three rotor revolutions. Detailed unsteady numerical flow visualization techniques were applied to the entire unsteady data set of five rotor revolutions and exhibited flowfield features such as blade vortex interaction and wake roll-up. The unsteady blade loads and surface pressures compare well against those from flight measurements. Details of the method, a discussion of the resulting predicted flowfield, and requirements for future work are presented. Overall, given the proper blade dynamics, this method can compute the unsteady flowfield of a general helicopter rotor in forward flight.

Ahmad, Jasim↗
NASA NTRS1999

Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

In boiling high heat fluxes are possible driven by relatively small temperature differences, which make its use increasingly attractive in aerospace applications. The objective of the research is to develop ways to overcome specific problems associated with boiling in the low gravity environment by substituting the buoyancy force with the electric force to enhance bubble removal from the heated surface. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50, as compared to values obtained for the same system without electric fields. The goal of our research is to experimentally explore the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions, by visualizing the temperature distributions in the vicinity of the heated surface and around the bubble during boiling using real-time holographic interferometry (HI) combined with high-speed cinematography. In the first phase of the project the influence of the electric field on a single bubble is investigated. Pool boiling is simulated by injecting a single bubble through a nozzle into the subcooled liquid or into the thermal boundary layer developed along the flat heater surface. Since the exact location of bubble formation is known, the optical equipment can be aligned and focused accurately, which is an essential requirement for precision measurements of bubble shape, size and deformation, as well as the visualization of temperature fields by HI. The size of the bubble and the frequency of bubble departure can be controlled by suitable selection of nozzle diameter and mass flow rate of vapor. In this approach effects due to the presence of the electric field can be separated from effects caused by the temperature gradients in the thermal boundary layer. The influence of the thermal boundary layer can be investigated after activating the heater at a later stage of the research. For the visualization experiments a test cell was developed. All four vertical walls of the test cell are transparent, and they allow transillumination with laser light for visualization experiments by HI. The bottom electrode is a copper cylinder, which is electrically grounded. The copper block is heated with a resistive heater and it is equipped with 6 thermocouples that provide reference temperatures for the measurements with HI. The top electrode is a mesh electrode. Bubbles are injected with a syringe into the test cell through the bottom electrode. The working fluids presently used in the interferometric visualization experiments, water and PF 5052, satisfy requirements regarding thermophysical, optical and electrical properties. A 30kV power supply equipped with a voltmeter allows to apply the electric field to the electrodes during the experiments. The magnitude of the applied voltage can be adjusted either manually or through the LabVIEW data acquisition and control system connected to a PC. Temperatures of the heated block are recorded using type-T thermocouples, whose output is read by a data acquisition system. Images of the bubbles are recorded with 35mm photographic and 16mm high-speed cameras, scanned and analyzed using various software packages. Visualized temperature fields HI allows the visualization of temperature fields in the vicinity of bubbles during boiling in the form of fringes. Typical visualized temperature distributions around the air bubbles injected into the thermal boundary layer in PF5052 are shown. The temperature of the heated surface is 35 C. The temperature difference for a pair of fringes is approximately 0.05 C. The heat flux applied to the bottom surface is moderate, and the fringe patterns are regular. In the image a bubble penetrating the thermal boundary layer is visible. Because of the axial symmetry of the problem, simplified reconstruction techniques can be applied to recover the temperature field. The thermal plume developing above the heated surface for more intensive heating is shown. The temperature distribution in the liquid is clearly 3D, and tomographic techniques have to be applied to recover the temperature distribution in such a physical situation. A sequence of interferometric images showing the temperature distribution around the rising bubble, recorded with a high-speed camera is shown. Again, the temperature distribution is 3D, and a more complex approach to the evaluation, the tomographic reconstruction has to be taken. Measurement of the temperature distribution from the fringe pattern temperature distributions that yield important information regarding heat transfer are determined. Two algorithms that allow the quantitative evaluation of interferometric fringe patterns and the reconstruction of temperature fields during boiling have been developed at the Heat Transfer Laboratory of the Johns Hopkins University. In the first algorithm the bubble is assumed to be axially symmetrical, which significantly reduces the computational effort for quantifying the temperature distribution around the bubble. For this purpose the thermal boundary layer around the bubble is divided into equidistant concentric shells, and the refractive index is assumed to be constant in each of the shells. Since large temperature gradients are expected in the vicinity of the bubble during boiling, the deflection of the light beam cannot be neglected in boiling experiments. Since the exit angle of the light beam is known, this allows to account for the deflections and phase shifts outside the boundary layer (in the bulk fluid and in the windows of the test cell). Three dimensional temperature distributions in the vicinity of the bubble are reconstructed using tomographic techniques. In tomography, the measurement volume is sliced into 2D planes. In the present study these planes are parallel to the heated surface. The objective is to determine the values of the field parameter of interest in form of the field function in these 2D planes. The field parameter is the change of the refractive index of the liquid in the measurement volume caused by temperature changes. By superimposing data for many 2D planes recorded at the same time instant, the 3D temperature distribution in the measurement volume is recovered.

Herman, Cila↗