Thomas J. Kulp

Remote-Raman Spectroscopy at Intermediate Ranges Using Low-Power cw Lasers

A portable Raman system is described that has been developed for line-of-site spectral measurements of remotely located samples at intermediate ranges. Raman spectra were measured at distances up to 20 m with the use of a 40-mm-diameter collection optic (f/500) and at 16.7 m with a 22-mm-diameter collection optic (f/750). In all cases, low-power cw lasers were used with powers ranging from 23 to 100 mW. The system consists of a small f/4 image-corrected spectrograph with a liquid-nitrogen-cooled CCD detector and has been demonstrated with both an argon-ion laser, emitting at 488 nm, and an 809-nm diode laser. Applications of the system include monitoring of organic and inorganic compounds at toxic waste sites during remediation, process monitoring, and remote detection of highly toxic materials.

Direct measurement of interstitial velocity field variations in a porous medium using fluorescent-particle image velocimetry

Abstract Fluorescent-particle image velocimetry (FPIV) is used in conjunction with refractive-index matching to measure flow velocities in the interstitial regions of a porous medium. Adaptations that allow the use of conventional PIV methodology in index-matched systems are discussed, and the results of flow field measurements in a porous test bed under saturated flow conditions are presented. Preliminary analysis of these data, in which the horizontal and vertical components of the interstitial velocity vectors were averaged over a specified region within the medium, are also presented and compared with the vertical velocity component calculated from the total volumetric flow rate. The magnitude of the macroscopically derived and FPIV-measured values are found to be very similar. In general, our results demonstrate the utility of the FPIV technique to determine both the point velocity and the local volume-averaged velocity within porous media.

Fluorescent particle image velocimetry: application to flow measurement in refractive index-matched porous media

This paper presents results in which particle image velocimetry (PIV) is used in conjunction with refractive index matching to measure fluid flow velocities within complex, multiphase systems. This application required the adaptation of PIV for use with fluorescent, rather than scattering, seed particles; we refer to the technique as fluorescent PIV (FPIV). We applied index-matched FPIV to the measurement of low flow velocities (tens of microns per second) at high spatial resolution (tens of microns) in a porous medium. We produced clear images of flowing particles in heterogeneous porous media and obtained reliable velocity vectors by a point-by-point interrogation of these images. We also found evidence of the intrapore mixing of porous media flow.

Measurement of porous medium velocity fields and their volumetric averaging characteristics using particle tracking velocimetry

Abstract The application of a new method for measuring velocity fields within a porous medium is presented. Fluid containing fluorescent microspheres is flowed through a transparent, refractive-index-matched column filled with 3.1 mm spherical beads. A planar laser beam illuminates a cross-section of the bed. Using a video camera and a frame-accurate videocassette recorder, the motions of the fluorescing particles are recorded as the fluid flows through the bed. Subsequently, the particles are tracked through a series of frames using a commerical image analysis software package. Because the particles move slowly compared to the video frame rate (30 frames per second), frame-to-frame particle identification is unambiguous. The time histories of the particle positions are used to calculate velocity components in the plane of the beam. Results are shown in which the velocity field within a full volumetric segment of a column is measured, and the averaging properties of the measured velocity field are discussed. The volumetrically averaged velocities are shown to be in good agreement with the superficial velocity. This technique is easy to automate and can be used to measure a wide range of velocities with high precision.

Backscatter absorption gas imaging: a new technique for gas visualization

This paper presents a new laser-based method of gas detection that permits real-time television images of gases to be produced. The principle of this technique [which is called backscatter absorption gas imaging (BAGI)] and the operation of two instruments used to implement it are described. These instruments use 5-W and 20-W CO(2) lasers to achieve gas imaging at ranges of approximately 30 and 125 m, respectively. Derivations of relevant BAGI signal equations that can be used to predict the performance of a gas imager are provided. The predictions of this model and the measured range performance of an extended-range gas imager are compared. Finally, the results of gas sensitivity measurements and imaging tests on flowing gases are presented. These can be used to generate a realistic estimate of the BAGI sensitivity expected in detecting leaks of many different vapors.

Development and testing of a synchronous-scanning underwater imaging system capable of rapid two-dimensional frame imaging

The design and construction of a synchronous-scanning underwater imaging system capable of rapid two-dimensional scanning are described. The imager employs a 7-W, all-lines, argon-ion laser in onjunction with a galvanometrically driven raster scanner and an image-dissector tube receiver. The imager is capable of directly generating real-time RS-170 video imagery. The results of an in-water test of the imaging system, in which a high-contrast imaging test pattern was imaged, demonstrate operating anges of up to 4 attenuation lengths (AL) when the test was run at real-time frame rates, ranges of 5.1-5.5 AL when the system operated with an eight-frame running average, and ranges of 6.3 AL when a 128-frame running average was used. The system performance was compared with that of several floodlight/silicon-intensified-target TV camera configurations, which produced a maximum imaging range of ∼2.6 AL. Also, an imaging configuration that used the raster-scanned beam of the laser as an illumination source for the sil n-intensified-target camera was tested. That system had an ultimate range of ∼ 4 AL.

Investigation of dispersion in porous media using fiber-optic technology

This paper presents results of a laboratory investigation of characteristics of solute transport utilizing fiber-optic technology. In this work, we examine solute transport in a uniform homogeneous porous medium with a one dimensional flow system using a fiber-optic fluorimeter system. In a series of experiments, fiber-optic sensors are used in-situ in a packed column to make observations of species concentration at the microscopic level. The tracer that is employed is assumed to be ideal and the flow field is restricted to be fully saturated and laminar. Using data measured at the pore level, we study the spatial variability in the concentration field during miscible displacement and relate these observations to the macroscopic flow characteristics.

Results of the final tank test of the LLNL/NAVSEA synchronous-scanning underwater laser imaging system

The design and construction of a synchronous-scanning underwater imaging system capable of rapid two-dimensional scanning is described. The imager employs a 7 W all-lines argon ion laser in conjunction with a galvanometrically driven raster scanner and an image-dissector tube receiver. The imager is capable of directly generating real-time RS-170 video imagery. The results of in-water test of the imaging system demonstrate operating ranges of up to 4 attenuation lengths (AL) when running at real-time frame rates, ranges of 5.1 - 5.5 AL when operating with an 8-frame running average, and ranges of 6.3 AL when using a 128-frame running average. Future frame averaging requirements are expected to be relaxed, due to improvements in the detector preamplifier. The system performance was compared with that of several floodlight/silicon intensified target (SIT) television camera configurations, which produced a maximum imaging range of about 2.6 AL. Also, an imaging configuration that used the raster-scanned beam of the laser as an illumination source for the SIT camera was tested. That system had an ultimate range of about 4 AL.

Current Status Of The NAVSEA Synchronous Scanning Laser Imaging System

This paper constitutes an update on our efforts to develop an underwater laser-based imaging system (UWLIS). The work is being performed under contract from the Naval Sea Systems Command Office of Salvage and Diving (NAUSEA/00C) in order to provide instrumentation that will improve the visibility range available to deep-ocean (1500-6000 m) submersible vehicles during ocean-floor search-and-salvage operations. In general, these submersibles are remotely operated vehicles (ROV) that currently employ high-intensity floodlights and low-light-level TV cameras to produce video images of the seafloor, which are relayed to the mother ship to allow target identification. Often, these floodlight-based systems require that the ROV come within 6 to 10 m of the target in order to positively identify it. This poses both a risk of damaging the vehicle on outcropping seafloor terrain features and an increase in mission cost due to the time lost on maneuvering to identify false targets. Given that salvage-operation costs typically range from

Application of flourescent particle imaging to measuring flow in complex media

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