Science.gov

Sample records for pressure drop porosity

  1. Prediction of the collection efficiency, the porosity, and the pressure drop across filter cakes in particulate air filtration

    NASA Astrophysics Data System (ADS)

    Al-Otoom, Awni Y.

    This study presents a new statistical model to predict the collection efficiency, cake thickness, cake porosity, and pressure drop across filter cakes during the particulate filtration of gases. This model is based on generation of a random distribution of particle sizes and particle falling locations. The model predicts the cake collection efficiency, which was found to be strongly dependent on the ratio of the mean particle size to the mean pore size of the filter medium. The average cake porosity decreases with increasing cake thickness and the pressure drop increases when the mean particle diameter decreases.

  2. Pressure Drop

    NASA Technical Reports Server (NTRS)

    Lawson, Mike

    2010-01-01

    Mike Lawson briefly discussed pressure drop for aerospace applications and presented short stories about adventures experienced while working at NASA and General Dynamics, including exposure to technologies like the Crew and Equipment Translation Aid (CETA) cart and the SWME.

  3. Gas Pressure-Drop Experiment

    ERIC Educational Resources Information Center

    Luyben, William L.; Tuzla, Kemal

    2010-01-01

    Most chemical engineering undergraduate laboratories have fluid mechanics experiments in which pressure drops through pipes are measured over a range of Reynolds numbers. The standard fluid is liquid water, which is essentially incompressible. Since density is constant, pressure drop does not depend on the pressure in the pipe. In addition, flow…

  4. Air Flow and Pressure Drop Measurements Across Porous Oxides

    NASA Technical Reports Server (NTRS)

    Fox, Dennis S.; Cuy, Michael D.; Werner, Roger A.

    2008-01-01

    This report summarizes the results of air flow tests across eight porous, open cell ceramic oxide samples. During ceramic specimen processing, the porosity was formed using the sacrificial template technique, with two different sizes of polystyrene beads used for the template. The samples were initially supplied with thicknesses ranging from 0.14 to 0.20 in. (0.35 to 0.50 cm) and nonuniform backside morphology (some areas dense, some porous). Samples were therefore ground to a thickness of 0.12 to 0.14 in. (0.30 to 0.35 cm) using dry 120 grit SiC paper. Pressure drop versus air flow is reported. Comparisons of samples with thickness variations are made, as are pressure drop estimates. As the density of the ceramic material increases the maximum corrected flow decreases rapidly. Future sample sets should be supplied with samples of similar thickness and having uniform surface morphology. This would allow a more consistent determination of air flow versus processing parameters and the resulting porosity size and distribution.

  5. Pressure Drop in Radiator Air Tubes

    NASA Technical Reports Server (NTRS)

    Parsons, S R

    1921-01-01

    This report describes a method for measuring the drop in static pressure of air flowing through a radiator and shows (1) a reason for the discrepancy noted by various observers between head resistance and drop in pressure; (2) a difference in degree of contraction of the jet in entering a circular cell and a square cell; (3) the ratio of internal frictional resistance to total head resistance for two representative types; (4) the effect of smoothness of surface on pressure gradient; and (5) the effects of supplying heat to the radiator on pressure gradient. The fact that the pressure gradients are found to be approximately proportional to the square of the rate of flow of air appears to indicate turbulent flow, even in the short tubes of the radiator. It was found that the drop in the static pressure in the air stream through a cellular radiator and the pressure gradient in the air tubes are practically proportional to the square of the air flow in a given air density; that the difference between the head resistance per unit area and the fall of static pressure through the air tubes in radiators is apparent rather than real; and that radiators of different types differ widely in the amount of contraction of the jet at entrance. The frictional resistance was found to vary considerably, and in one case to be two-thirds of the head resistance in the type using circular cells and one-half of the head resistance of the radiator type using square cells of approximately the same dimensions.

  6. Low-Pressure-Drop Shutoff Valve

    NASA Technical Reports Server (NTRS)

    Thornborrow, John

    1994-01-01

    Flapper valve remains open under normal flow conditions but closes upon sudden increases to high rate of flow and remains closed until reset. Valve is fluid/mechanical analog of electrical fuse or circuit breaker. Low-pressure-drop shutoff valve contains flapper machined from cylindrical surface. During normal flow conditions, flapper presents small cross section to flow. (Useful in stopping loss of fluid through leaks in cooling systems.)

  7. Predicting Pressure Drop In Porous Materials

    NASA Technical Reports Server (NTRS)

    Lawing, Pierce L.

    1990-01-01

    Theory developed to predict drop in pressure based on drag of individual fibers. Simple correlation method for data also developed. Helps in predicting flow characteristics of many strain-isolation pad (SIP) glow geometries in Shuttle Orbiter tile system. Also helps in predicting venting characteristics of tile assemblies during ascent and leakage of hot gas under tiles during descent. Useful in study of mechanics of flows through fibrous and porous media, and procedures applicable to purged fiberglass insulation, dialysis filters, and other fibrous and porous media.

  8. Pressure drop of He II flow through a porous media

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1990-01-01

    The paper reports on measurements of He II pressure drop across two porous SiO2 ceramic filter materials. These materials vary only in porosity, having values of 0.94 and 0.96. The average fiber diameter in both cases is approximately 5 microns. The experiment consists of a glass tube containing a piece of this sponge in one end. The tube is rapidly displaced downward in a bath of helium and the liquid levels are allowed to equilibrate over time producing variable velocities up to 10 cm/sec. The results are compared with those previously obtained using fine mesh screens. Good qualitative agreement is observed for turbulent flow; however, the behavior in the laminar flow regime is not fully understood.

  9. Pressure drop of He II flow through a porous media

    NASA Astrophysics Data System (ADS)

    Maddocks, J. R.; van Sciver, S. W.

    The paper reports on measurements of He II pressure drop across two porous SiO2 ceramic filter materials. These materials vary only in porosity, having values of 0.94 and 0.96. The average fiber diameter in both cases is approximately 5 microns. The experiment consists of a glass tube containing a piece of this sponge in one end. The tube is rapidly displaced downward in a bath of helium and the liquid levels are allowed to equilibrate over time producing variable velocities up to 10 cm/sec. The results are compared with those previously obtained using fine mesh screens. Good qualitative agreement is observed for turbulent flow; however, the behavior in the laminar flow regime is not fully understood.

  10. Fundamental study of transpiration cooling. [pressure drop and heat transfer data from porous metals

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Dutton, J. L.; Benson, B. A.

    1973-01-01

    Isothermal and non-isothermal pressure drop data and heat transfer data generated on porous 304L stainless steel wire forms, sintered spherical stainless steel powder, and sintered spherical OFHC copper powder are reported and correlated. Pressure drop data was collected over a temperature range from 500 R to 2000 R and heat transfer data collected over a heat flux range from 5 to 15 BTU/in2/sec. It was found that flow data could be correlated independently of transpirant temperature and type (i.e., H2, N2). It was also found that no simple relation between heat transfer coefficient and specimen porosity was obtainable.

  11. Method for reducing pressure drop through filters, and filter exhibiting reduced pressure drop

    DOEpatents

    Sappok, Alexander; Wong, Victor

    2014-11-18

    Methods for generating and applying coatings to filters with porous material in order to reduce large pressure drop increases as material accumulates in a filter, as well as the filter exhibiting reduced and/or more uniform pressure drop. The filter can be a diesel particulate trap for removing particulate matter such as soot from the exhaust of a diesel engine. Porous material such as ash is loaded on the surface of the substrate or filter walls, such as by coating, depositing, distributing or layering the porous material along the channel walls of the filter in an amount effective for minimizing or preventing depth filtration during use of the filter. Efficient filtration at acceptable flow rates is achieved.

  12. Secondary compaction after secondary porosity: Can it form a pressure seal?

    NASA Astrophysics Data System (ADS)

    Weedman, Suzanne D.; Brantley, Susan L.; Albrecht, Wolfgang

    1992-04-01

    Petrography analysis of sandstones from the vicinity of a pressure seal (transition from normal to overpressure) at 5.5-km depth in the lower Tuscaloosa Formation in Louisiana documents local, high porosity above and below the seal. Packing analysis shows that compaction is greater in normally pressured, high-porosity sandstones than in overpressured, high-porosity sandstones; compaction in overpressured, high-porosity sandstones is similar to that in normally pressured, well-cemented sandstones. We propose that focused corrosive fluids created a zone of high secondary porosity, allowing further compaction that we call "secondary compaction." Secondary compaction is greater above the seal than below, suggesting that high-pressure fluid below the seal has preserved porosity and that the pressure seal became effective soon after dissolution of cement. Cuttings from the pressure-seal zone reveal an unusual texture of fragmented, pressure-solved grains and matrix, which may be a result of extensive secondary compaction.

  13. Effect of humidity on the filter pressure drop

    SciTech Connect

    Vendel, J.; Letourneau, P.

    1995-02-01

    The effects of humidity on the filter pressure drop have been reported in some previous studies in which it is difficult to draw definite conclusions. These studies show contradictory effects of humidity on the pressure drop probably due to differences in the hygroscopicity of the test aerosols. The objective of this paper is to present experimental results on the evolution of the filter pressure drop versus mass loading, for different test aerosols and relative humidities. Present results are compared to those found in various publication. An experimental device has been designed to measure filter pressure drop as the function of the areal density for relative humidity varying in the range of 9 % to 85 %. Experiments have been conducted with hygroscopic: (CsOH) and nonhygroscopic aerosols (TiO{sub 2}). Cesium hydroxyde (CsOH) of size of 2 {mu} M AMMD has been generated by an ultrasonic generator and the 0.7 {mu}m AMMD titanium oxyde has been dispersed by a {open_quotes}turn-table{close_quotes} generator. As it is noted in the BISWAS`publication [3], present results show, in the case of nonhygroscopic aerosols, a linear relationship of pressure drop to mass loading. For hygroscopic aerosols two cases must be considered: for relative humidity below the deliquescent point of the aerosol, the relationship of pressure drop to mass loading remains linear; above the deliquescent point, the results show a sudden increase in the pressure drop and the mass capacity of the filter is drastically reduced.

  14. Pressure drop through generic lumens of hemodialysis catheters.

    PubMed

    Fricker, Zachary P; Rockwell, Donald O

    2007-01-01

    A unique, air-based system has been developed and implemented for rapid and accurate determination of pressure drop versus flow rate characteristics of generic catheter lumens; dimensionless scaling parameters can be effectively used to express these characteristics in units of blood flow used in the clinical setting. Theoretical models are compared with experimental data. For flow and geometric parameters of practical importance, the pronounced effect of developing flow in the lumen must be accounted for in calculation of the pressure drop along the lumen. That is, the theory of classical Poiseuille flow substantially underpredicts the pressure drop. Moreover, a side hole can induce significant, and in some cases large, values of pressure drop, even when the area of the hole exceeds the cross-sectional area of the lumen.

  15. Pressure drop in tubing in aircraft instrument installations

    NASA Technical Reports Server (NTRS)

    Wildhack, W A

    1937-01-01

    The theoretical basis of calculation of pressure drop in tubing is reviewed briefly. The effect of pressure drop in connecting tubing upon the operation and indication of aircraft instruments is discussed. Approximate equations are developed, and charts and tables based upon them are presented for use in designing installations of altimeters, air-speed indicators, rate-of-climb indicators, and air-driven gyroscopic instruments.

  16. A kinetic model of pressure solution/compaction for porosity prediction

    SciTech Connect

    Lahann, R.W. )

    1991-03-01

    A pressure/temperature history model for prediction of porosity of well-sorted, quartzose sandstones was developed and calibrated. The model assumes that porosity loss of quartzose sandstones is by pressure solution, which can be modeled by calculations of pressure solution/compaction of a uniform grain pack. The model assumes that all mass mobilized by the pressure solution is precipitated within the system and no mass is introduced from outside sources. A pressure solution rate law was developed that requires depth, temperature, and pressure information throughout the sandstone burial history. Rate of pressure solution is assumed to be proportional to effective lithostatic pressure, inversely proportional to te contact area between grains, and to have an Arrhenius-type dependence on temperature. The predicted porosities vary as a function of grain size and the pressure/temperature history of the sample. 'Unknowns' in the rate law were determined by calibration to a North Sea/Norwegian shelf data base of average porosities for well-sorted sandstones ranging in age from Devonian to Jurassic. Comparison of observed and model-predicted porosities indicates that, for the calibration data base, the model has a standard error if estimate of 3.6 porosity units. Sources of error include erroneous model assumptions, and grain size, sorting, and temperature and pressure history determinations on the calibration set. The model was tested on US Gulf Coast Miocene and Oligocene reservoirs and provided good estimates of observed porosities.

  17. Prediction of Frictional Pressure Drop During Water Permeation Through Packed Beds of Granular Particulates

    SciTech Connect

    KING, WILLIAM D.; ALEMAN, SEBASTIAN E.; HAMM, L. LARRY; PETTIS, MYRA A.

    2005-10-25

    A methodology has been developed based on the Kozeny-Carman equation to predict frictional pressure drops during water permeation of packed columns containing essentially noncompressible, but highly irregular particles. The resulting model accurately predicts pressure drop as a function of liquid flow rate and resin particle size for this system. A total of five particle sieve cuts across the range -20 to +70 mesh were utilized for testing using deionized water as the mobile phase. The Rosin-Rammler equation was used to fit the raw particle size data (wet sieve analysis) for the as-received resin sample and generate a continuous cumulative distribution function based on weight percent passing through the sieve. Probability distribution functions were calculated from the cumulative distribution for each particle sieve cut tested. Nine particle diameter definitions (i.e., number mean, volume mean, etc.) were then selected from the distribution function for each sample to represent the average spherically-equivalent particle diameter as input to the Kozeny-Carman equation. Nonlinear least squares optimization of the normalized pressure drop residuals were performed by parameter estimation of particle shape factor and bed porosity for all samples simultaneously using a given average particle diameter definition. Good fits to the full experimental data set were obtained when utilizing the number mean and the number median diameters. However, the shape factor and porosity values of 0.88 and 0.40, respectively, obtained from fitting the data using the number mean diameter were more consistent with experimental observations.

  18. Effects of cake collapse caused by deposition of fractal aggregates on pressure drop during ceramic filtration.

    PubMed

    Zhang, Wei; Li, Cai-Ting; Wei, Xian-Xun; Gao, Hong-Liang; Wen, Qing-Bo; Fan, Xiao-Peng; Shu, Xin; Zeng, Guang-Ming; Wei, Wei; Zhai, Yun-Bo; He, Yi-De; Li, Shan-Hong

    2011-05-15

    A cake collapse model was developed by taking the combined effects of fractal dimension, relaxation ratio, coordination number, and aggregate diameter into consideration. The cake porosity including intraaggregate and interaggregate porosities was modeled successively by three typical coordination numbers (n = 6, 8, and 12). Accordingly, an inversion method made it possible to deduce the coordination number using the measured cake porosities, and the reverse-calculated value with minimum error and the corresponding relaxation ratios were applied as the parameters for the model. As a result, the profiles of intraaggregate and interaggregate porosities and cake porosity were respectively predicted in contrast to the integrated variation of the relaxation ratio and the fractal dimension. Furthermore, a comparison between the model predictions of the cake pressure drop gradients with and without aggregate compression was conducted to validate the presence of cake collapse. The results show that the predictions based on the proposed collapse model are in agreement with the experiments, and the coordination number is one of the key factors that must be incorporated into the cake collapse models.

  19. Reducing cyclone pressure drop with evasés

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclones are widely used to separate particles from gas flows and as air emissions control devices. Their cost of operation is proportional to the fan energy required to overcome their pressure drop. Evasés or exit diffusers potentially could reduce exit pressure losses without affecting collection...

  20. He II heat transfer through random packed spheres: Pressure drop

    NASA Astrophysics Data System (ADS)

    Vanderlaan, M. H.; Van Sciver, S. W.

    2014-09-01

    Heat flow induced pressure drop through superfluid helium (He II) contained in porous media is examined. In this experiment, heat was applied to one side of a He II column containing a random pack of uniform size polyethylene spheres. Measured results include steady state pressure drops across the random packs of spheres (nominally 35 μm, 49 μm, and 98 μm diameter) for different heat inputs. Laminar, turbulent, and transition fluid flow regimes are examined. The laminar permeability and equivalent channel shape factor are compared to our past studies of the temperature drop through He II in the same porous media of packed spheres. Results from the pressure drop experiments are more accurate than temperature drop experiments due to reduced measurement errors achieved with the pressure transducer. Turbulent results are fitted to models with empirically derived friction factors. A turbulent model considering only dynamic pressure losses in the normal fluid yields the most consistent friction factors. The addition of the laminar and turbulent heat flow equations into a unifying prediction fits all regimes to within 10%.

  1. Controlling Vapor Pressure In Hanging-Drop Crystallization

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C.; Smith, Robbie

    1988-01-01

    Rate of evaporation adjusted to produce larger crystals. Device helps to control vapor pressure of water and other solvents in vicinity of hanging drop of solution containing dissolved enzyme protein. Well of porous frit (sintered glass) holds solution in proximity to drop of solution containing protein or enzyme. Vapor from solution in frit controls evaporation of solvent from drop to control precipitation of protein or enzyme. With device, rate of nucleation limited to decrease number and increase size (and perhaps quality) of crystals - large crystals of higher quality needed for x-ray diffraction studies of macromolecules.

  2. Pressure Drop Reduction of Slush Nitrogen in Turbulent Pipe Flows

    NASA Astrophysics Data System (ADS)

    Ohira, K.; Nozawa, M.; Ishimoto, J.; Koizumi, N.; Kamiya, T.

    2008-03-01

    Slush fluid such as slush hydrogen and slush nitrogen is a two-phase (solid-liquid) single-component cryogenic fluid containing solid particles in liquid, and consequently its density and refrigerant capacity are greater than for liquid state fluid. Experimental tests were performed with slush nitrogen to obtain the frictional pressure drop flowing in a 15 mm internal diameter, 400 mm long, horizontal, stainless steel pipe. The primary objective of this study was to investigate the pressure drop reduction phenomenon with changes in velocity and solid fraction. From the experimental results, the pressure drop correlation between the friction factor and the Reynolds number was obtained and an empirical correlation was derived. Flow patterns for slush nitrogen inside a pipe and the behavior of solid particles were also observed using a high speed camera.

  3. Experimental Investigation of Oscillatory Flow Pressure and Pressure Drop Through Complex Geometries

    NASA Technical Reports Server (NTRS)

    Ibrahim, Mounir B.; Wang, Meng; Gedeon, David

    2005-01-01

    A series of experiments have been performed to investigate the oscillatory flow pressure and pressure drop through complex geometries. These experiments were conducted at the CSU-SLRE facility which is a horizontally opposed, two-piston, single-acting engine with a split crankshaft driving mechanism. Flow through a rectangular duct, with no insert (obstruction), was studied first. Then four different inserts were examined: Abrupt, Manifold, Diverging Short and Diverging Long. The inserts were mounted in the center of the rectangular duct to represent different type of geometries that could be encountered in Stirling machines. The pressure and pressure drop of the oscillating flow was studied for: 1) different inserts, 2) different phase angle between the two pistons of the engine (zero, 90 lead, 180, and 90 lag), and 3) for different piston frequencies (5, 10, 15, and 20 Hz). It was found that the pressure drop of the oscillatory flow increases with increasing Reynolds number. The pressure drop was shown to be mainly due to the gas inertia for the case of oscillatory flow through a rectangular duct with no insert. On the other hand, for the cases with different inserts into the rectangular duct, the pressure drop has three sources: inertia, friction, and local losses. The friction pressure drop is only a small fraction of the total pressure drop. It was also shown that the dimensionless pressure drop decreases with increasing kinetic Reynolds number.

  4. Drop splashing induced by target roughness and porosity: The size plays no role.

    PubMed

    Roisman, Ilia V; Lembach, Andreas; Tropea, Cameron

    2015-08-01

    Drop splash as a result of an impact onto a dry substrate is governed by the impact parameters, gas properties and the substrate properties. The splash thresholds determine the boundaries between various splash modes. Various existing models for the splash threshold are reviewed in this paper. It is shown that our understanding of splash is not yet complete. The most popular, widely used models for splash threshold do not describe well the available experimental data. The scientific part of this paper is focused on the description of drop prompt splash on rough and porous substrates. It is found that the absolute length scales of the substrate roughness, like Ra or Rz, do not have any significant effect on the splash threshold. It is discovered that on rough substrates the main influencing splash parameters are the impact Weber number and the characteristic slope of the roughness of the substrate. The drop deposition without splash on porous substrates is enhanced by the liquid modified Reynolds number. Surprisingly, it is not influenced by the pore size, at least for the impact parameters used in the experiments. Finally, an empirical correlation for the prompt splash on rough and porous substrates is proposed, based on a rather amount of experimental data. PMID:25791159

  5. Determination of pressure drop across activated carbon fiber respirator cartridges.

    PubMed

    Balanay, Jo Anne G; Lungu, Claudiu T

    2016-01-01

    Activated carbon fiber (ACF) is considered as an alternative adsorbent to granular activated carbon (GAC) for the development of thinner, lighter, and efficient respirators because of their larger surface area and adsorption capacities, thinner critical bed depth, lighter weight, and fabric form. This study aims to measure the pressure drop across different types of commercially available ACFs in respirator cartridges to determine the ACF composition and density that will result in acceptably breathable respirators. Seven ACF types in cloth (ACFC) and felt (ACFF) forms were tested. ACFs in cartridges were challenged with pre-conditioned constant air flow (43 LPM, 23°C, 50% RH) at different compositions (single- or combination-ACF type) in a test chamber. Pressure drop across ACF cartridges were obtained using a micromanometer, and compared among different cartridge configurations, to those of the GAC cartridge, and to the NIOSH breathing resistance requirements for respirator cartridges. Single-ACF type cartridges filled with any ACFF had pressure drop measurements (23.71-39.93 mmH2O) within the NIOSH inhalation resistance requirement of 40 mmH2O, while those of the ACFC cartridges (85.47±3.67 mmH2O) exceeded twice the limit due possibly to the denser weaving of ACFC fibers. All single ACFF-type cartridges had higher pressure drop compared to the GAC cartridge (23.13±1.14 mmH2O). Certain ACF combinations (2 ACFF or ACFC/ACFF types) resulted to pressure drop (26.39-32.81 mmH2O) below the NIOSH limit. All single-ACFF type and all combination-ACF type cartridges with acceptable pressure drop had much lower adsorbent weights than GAC (≤15.2% of GAC weight), showing potential for light-weight respirator cartridges. 100% ACFC in cartridges may result to respirators with high breathing resistance and, thus, is not recommended. The more dense ACFF and ACFC types may still be possibly used in respirators by combining them with less dense ACFF materials and/or by

  6. Determination of pressure drop across activated carbon fiber respirator cartridges.

    PubMed

    Balanay, Jo Anne G; Lungu, Claudiu T

    2016-01-01

    Activated carbon fiber (ACF) is considered as an alternative adsorbent to granular activated carbon (GAC) for the development of thinner, lighter, and efficient respirators because of their larger surface area and adsorption capacities, thinner critical bed depth, lighter weight, and fabric form. This study aims to measure the pressure drop across different types of commercially available ACFs in respirator cartridges to determine the ACF composition and density that will result in acceptably breathable respirators. Seven ACF types in cloth (ACFC) and felt (ACFF) forms were tested. ACFs in cartridges were challenged with pre-conditioned constant air flow (43 LPM, 23°C, 50% RH) at different compositions (single- or combination-ACF type) in a test chamber. Pressure drop across ACF cartridges were obtained using a micromanometer, and compared among different cartridge configurations, to those of the GAC cartridge, and to the NIOSH breathing resistance requirements for respirator cartridges. Single-ACF type cartridges filled with any ACFF had pressure drop measurements (23.71-39.93 mmH2O) within the NIOSH inhalation resistance requirement of 40 mmH2O, while those of the ACFC cartridges (85.47±3.67 mmH2O) exceeded twice the limit due possibly to the denser weaving of ACFC fibers. All single ACFF-type cartridges had higher pressure drop compared to the GAC cartridge (23.13±1.14 mmH2O). Certain ACF combinations (2 ACFF or ACFC/ACFF types) resulted to pressure drop (26.39-32.81 mmH2O) below the NIOSH limit. All single-ACFF type and all combination-ACF type cartridges with acceptable pressure drop had much lower adsorbent weights than GAC (≤15.2% of GAC weight), showing potential for light-weight respirator cartridges. 100% ACFC in cartridges may result to respirators with high breathing resistance and, thus, is not recommended. The more dense ACFF and ACFC types may still be possibly used in respirators by combining them with less dense ACFF materials and/or by

  7. Prediction of Pressure Drop in the ITER Divertor Cooling Channels

    SciTech Connect

    Yin, S.T.; Chen, J.L.

    2005-04-15

    This study investigated the pressure drop in the divertor cooling channels of the International Thermonuclear Experimental Reactor (ITER). The water in the cooling channels will encounter the following flow and boiling regimes: 1) single-phase convection, 2) highly-subcooled boiling, 3) onset of nucleate boiling (ONB), and 4) fully-developed subcooled boiling. The upper operating boundary is limited by the departure from nucleate boiling (DNB) or burnout conditions. Twisted-tape insert will be used to enhance local heat transfer. Analytical models, validated with relevant databases, were proposed for the above-identified flow regimes. A user-friendly computer code was developed to calculate the overall pressure drop and the exit pressure of a specific local segment throughout the entire flow circuit. Although the operating parameters were based on the CDA phase input the results are found in general agreement when compared with the ITER EDA results.

  8. Equivalent particle diameter and length scale for pressure drop in porous metals

    SciTech Connect

    Dukhan, Nihad; Patel, Pragnesh

    2008-04-15

    The internal architecture of metal foam is significantly different from that of traditional porous media. This provides a set of challenges for understanding the fluid flow in this relatively new class of materials. This paper proposes that despite the geometrical differences between metal foam and traditional porous media, the Ergun correlation is a good fit for the linear pressure drop as a function of the Darcian velocity, provided that an appropriate equivalent particle diameter is used. The paper investigates an appropriate particle diameter considering the physics of energy dissipation, i.e. the viscous shear and the form drag. The above approach is supported by wind tunnel steady-state unidirectional pressure drop measurements for airflow through several isotropic open-cell aluminum foam samples having different porosities and pore densities. For each foam sample, the equivalent particle diameter correlated well with the surface area per unit volume of the foam. This was also very well valid for previous porous metal pressure drop data in the open literature. (author)

  9. Percolating porosity in ultrafine grained copper processed by High Pressure Torsion

    SciTech Connect

    Wegner, Matthias Leuthold, Jörn; Peterlechner, Martin; Divinski, Sergiy V. Wilde, Gerhard; Setman, Daria; Zehetbauer, Michael; Pippan, Reinhard

    2013-11-14

    Defect structures in copper of different purity (nominally 99.99 and 99.999 wt. %) deformed via High Pressure Torsion (HPT) with varying processing parameters are investigated utilizing the radiotracer diffusion technique. While the degree of deformation is kept constant, the effects of applied quasi-hydrostatic pressure, processing temperature, post-deformation annealing treatments, and of the impurity concentration on the deformed samples are analyzed in terms of the formation of interconnected internal porosity. Furthermore, the anisotropy of the developing porosity network is examined. The porosity channels occurred to be interconnected along the direction parallel to the surface normal with a volume fraction of the order of a few ppm while no long-range penetration along the internal porosity could be detected when measured along the azimuthal or radial directions of a HPT processed sample.

  10. Validation of an All-Pressure Fluid Drop Model: Heptane Fluid Drops in Nitrogen

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.; Bulzan, Daniel L. (Technical Monitor)

    2000-01-01

    Despite the fact that supercritical fluids occur both in nature and in industrial situations, the fundamentals of their behavior is poorly understood because supercritical fluids combine the characteristics of both liquids and gases, and therefore their behavior is not intuitive. There are several specific reasons for the lack of understanding: First, data from (mostly optical) measurements can be very misleading because regions of high density thus observed are frequently identified with liquids. A common misconception is that if in an experiment one can optically identify "drops" and "ligaments", the observed fluid must be in a liquid state. This inference is incorrect because in fact optical measurements detect any large change (i.e. gradients) in density. Thus, the density ratio may be well below Omicron(10(exp 3)) that characterizes its liquid/gas value, but the measurement will still identify a change in the index of refraction providing that the change is sudden (steep gradients). As shown by simulations of supercritical fluids, under certain conditions the density gradients may remain large during the supercritical binary fluids mixing, thus making them optically identifiable. Therefore, there is no inconsistency between the optical observation of high density regions and the fluids being in a supercritical state. A second misconception is that because a fluid has a liquid-like density, it is appropriate to model it as a liquid. However, such fluids may have liquid-like densities while their transport properties differ from those of a liquid. Considering that the critical pressure of most fuel hydrocarbons used in Diesel and gas turbine engines is in the range of 1.5 - 3 MPa, and the fact that the maximum pressure attained in these engines is about 6 Mps, it is clear that the fuel in the combustion chamber will experience both subcritical and supercritical conditions. Studies of drop behavior over a wide range of pressures were performed in the past

  11. Pressure drop and He II flow through fine mesh screens

    NASA Technical Reports Server (NTRS)

    Maddocks, J. R.; Van Sciver, S. W.

    1989-01-01

    Fluid acquisition systems for He II transfer devices will utilize gallery arms to ensure that the fluid encounters the pump inlet. In near term experiments such as Superfluid Helium on Orbit Transfer (SHOOT), the preferred configuration consists of several rectangular channels which have one side made from a Dutch weave stainless steel screen having 325 x 2300 wires per inch. The effective pore diameter for this screen is about 5 microns. The present paper reports on measurements of pressure drop across a screen when it is subjected to a flow of liquid helium. The experiment measures the time rate of change of the level in two different helium reservoirs connected by a screen-blocked channel. Results with normal helium are compared with predictions based on the Armour-Cannon (1968) equations. The He II data show considerable deviation from the classical result. A discussion of the He II pressure drop results in terms of two fluid hydrodynamics is included.

  12. The pressure drop in a porous material layer during combustion

    SciTech Connect

    Kondrikov, B.N.

    1995-07-01

    During the combustion of a porous material layer, a manometer, which is attached to the cold end of the charge, records at the bottom of the layer a pressure reduction, which was discovered more than 20 years ago but which remains essentially unexplained up to the present. It is experimentally shown that this effect is similar to the pressure change in the cavities when a light gas (helium, hydrogen) diffuses from (or to) them under isothermal conditions and that it increases during the combustion mainly due to the accompanying Stefan type flow, and probably also as a result of the thermal diffusion. A pressure drop in the cavities is evidently made possible also by the pressure reduction in the flame which follows from the Hugoniot adiabatic theory.

  13. Limiting the Accidental Pressure Drop in NIF Beam Tubes

    SciTech Connect

    Garcia, M

    2000-11-06

    This report summarizes the use of a one-dimensional model of a time-dependent compressible flow condition to validate the results from a more sophisticated three-dimensional model. The flow conditions consist of the sudden decompression of a pressurized tube joined to an evacuated sphere, where the tube also has a leak to external atmosphere that is triggered open at a given pressure difference below sea-level pressure. This flow model is used to calculate conditions in a NIF beam tube if an internal vacuum barrier fails, and to calculate how the size and timing of an opening to external atmosphere changes tube pressure. Decompression of a NIF beam tube is a potential safety hazard since the tube could collapse if the tube pressure is reduced below the buckling limit. To prevent this from occurring, each pressurized section includes a rupture panel which is designed to open to external atmosphere at a given pressure difference. The inrush of external atmosphere through the rupture panel fills both the tube and the vacuum drawing on it, and in this way the pressure drop in the tube is quickly limited and reversed. In summary, the results from the 1D model indicate that the 3-D calculations are accurate and reasonable.

  14. A Seismic Velocity-Pressure Model for Sedimentary Rocks Consistent with Critical Porosity and Compaction Theory

    NASA Astrophysics Data System (ADS)

    Saul, M.; Lumley, D. E.

    2011-12-01

    Knowledge of the pressure dependence of seismic rock properties is useful for analysis of sedimentary basins, prediction of pore pressure and geomechanical effects, and time-lapse monitoring of groundwater, petroleum, geothermal and CO2 sequestration reservoirs. We are especially interested in changes in seismic rock properties due to changes in pore pressure caused by injection or withdrawal of fluids from the sedimentary rock. A long standing problem has been that physical model-based derivations of velocity-pressure relationships (e.g., Hertz-Mindlin) do not fit lab measurements well, and alternatively, empirical regressions that are fit to specific data points do not extrapolate well to other conditions because they have little or no physical basis. A key problem is the accurate determination of the dry rock frame properties at low effective pressure (i.e., high pore pressure), particularly when ultrasonic lab measurements at or near zero effective pressure are not available. We propose a double exponential model to describe the pressure sensitivity of the bulk modulus (K) and shear modulus (G) for unconsolidated sands. The physical basis for this model incorporates compaction porosity-depth trends for unconsolidated sands, and the concept of critical porosity when a sediment-fluid mixture is at the critical point of a suspension. Grain size distribution and sorting information is used to estimate the critical porosity of a rock when it was first deposited as sediment, and this value is used to constrain the compacted rock velocity at zero effective pressure. A porosity-pressure relationship is included in the model to account for porosity loss with increases in effective pressure, and this leads to a relationship to predict density changes with effective pressure. Our new model is tested on laboratory measurements of unsaturated sand samples and fits well over a wide range of pressure conditions, grain size distributions and compositions. This new velocity-pressure

  15. Sudden Drops in Blood Pressure Tied to Higher Odds for Dementia

    MedlinePlus

    ... news/fullstory_161422.html Sudden Drops in Blood Pressure Tied to Higher Odds for Dementia Dizziness, faintness ... be an association between sudden drops in blood pressure upon standing up -- a condition called orthostatic hypotension -- ...

  16. How low can you go? Low pressure drop laboratory design

    SciTech Connect

    Weale, John; Rumsey, Peter; Sartor, Dale; Lock, Lee Eng

    2001-12-01

    Laboratory buildings are characterized by the production of potentially hazardous fumes within the occupied space. The primary objective of a laboratory ventilation system is to isolate and protect the occupants from the fumes, as well as provide minimum outside air at a comfortable temperature. Fume removal results in the need for a large volume of conditioned make-up air, typically a significantly greater volume than required for space temperature conditioning purposes. The high quantity of exhaust naturally results in a once through system, which is also often required by codes that prohibit any recirculation in a laboratory space. The high costs associated with high airflow systems are magnified by the 24 hours a day, 356 days a year ventilation operation often seen in laboratory situations. All too often, the common design approach taken to laboratory mechanical systems results in a traditional office ventilation system upsized to meet a laboratory's requirements. Recognizing the unique aspects of laboratory requirements and operation is essential to optimizing the mechanical system. Figure 1 shows a breakdown of a laboratory building's electricity use, based on a DOE 2 model of a baseline laboratory building design for Montana State University (Bozeman, MT). In laboratory buildings, the largest and easiest target for energy use reduction is usually the ventilation energy. At about 50 percent of the buildings total electricity usage, a 15 percent reduction in the power required by the ventilation system would save more energy than eliminating all lighting energy. As the largest component of a laboratory's energy consumption, the ventilation system is the first target to reduce the energy bill. Significantly improving the standard design efficiency of a ventilation system requires a lower air pressure drop system on both the supply and exhaust system. Implementing low-pressure drop design strategies from the early stages of the design process will result in

  17. Effects of brush seal morphology on leakage and pressure drops

    NASA Technical Reports Server (NTRS)

    Braun, M. J.; Yang, Y.; Hendricks, R. C.

    1991-01-01

    Research on brush seals which was undertaken earlier by Braun et al. (1990) is continued. Particular attention is given to the effects of brush positioning, design, and morphology on sealing surfaces, fluid leakage, and associated pressure drops. It is found that both the structure and the design of the brush are important to its performance. High resistance to the flow of the brush/fence combination can result in catastrophic failure of the brush, while at lower flow resistances, the failure is more gradual.

  18. Numerical Analysis including Pressure Drop in Oscillating Water Column Device

    NASA Astrophysics Data System (ADS)

    das Neves Gomes, Mateus; Domingues dos Santos, Elizaldo; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira

    2015-06-01

    The wave energy conversion into electricity has been increasingly studied in the last years. There are several proposed converters. Among them, the oscillatingwater column (OWC) device has been widespread evaluated in literature. In this context, the main goal of this work was to perform a comparison between two kinds of physical constraints in the chimney of the OWC device, aiming to represent numerically the pressure drop imposed by the turbine on the air flow inside the OWC. To do so, the conservation equations of mass,momentumand one equation for the transport of volumetric fraction were solved with the finite volume method (FVM). To tackle thewater-air interaction, the multiphase model volume of fluid (VOF)was used. Initially, an asymmetric constraint inserted in chimney duct was reproduced and investigated. Subsequently, a second strategywas proposed,where a symmetric physical constraint with an elliptical shapewas analyzed. Itwas thus possible to establish a strategy to reproduce the pressure drop in OWC devices caused by the presence of the turbine, as well as to generate its characteristic curve.

  19. Laboratory measurements of Vp and Vs in a porosity-developed crustal rock: Experimental investigation into the effects of porosity at deep crustal pressures

    NASA Astrophysics Data System (ADS)

    Saito, Satoshi; Ishikawa, Masahiro; Arima, Makoto; Tatsumi, Yoshiyuki

    2016-05-01

    In order to evaluate the influence of porosity on the elastic properties of crustal rocks at deep crustal pressures, we performed laboratory measurements of compressional-wave (Vp) and shear-wave (Vs) velocities in a porosity-developed gabbro sample up to 1.0 GPa at room temperature. Based on the measured Vp and Vs data, we evaluated the changes in velocities, Vp/Vs, Poisson's ratio (σ), and total porosity of the rock as a function of pressure. Compared with the 'porosity-free' intrinsic elastic values of the gabbro sample, our results suggest that the development of porosity in crustal rocks lowers their Vp, Vs, Vp/Vs, and Poisson's ratio. Deviations (ΔVp, ΔVs, ΔVp/Vs, and Δσ) of the measured values from the intrinsic values are enhanced with increasing porosity. We evaluated the ΔVp from previous experimental study on the rocks of Tanzawa plutonic complex providing constraints on interpretation of the seismic velocity profiles of the Izu-Bonin-Mariana (IBM) arc and found a large negative ΔVp (up to - 22.7%) at lower pressures. The intrinsic velocity combined with the measured velocity data at in situ pressure conditions suggest that the ranges of Vp (6.0-6.5 km/s) in the middle crust of the IBM arc reflect the presence of considerable porosity and its closure in intermediate rocks and/or the change of composition from felsic to intermediate in mid-crustal rocks.

  20. The principles of pressure drop in long segment stenosis.

    PubMed

    Goldberg, S J

    1986-10-01

    With Doppler echocardiography, determination of pressure gradients at the region of valvular stenoses with the aid of the modified Bernoulli equation has been shown feasible in clinical and experimental studies. The Bernoulli equation neglects frictional losses and prerequisites laminar flow across the stenosis such that it would not appear applicable for long segment stenoses in the cardiovascular system. To evaluate pressure drop in a long segment stenosis, the full form of the energy balance equation, encompassing frictional losses and localized velocity profile, must be taken into consideration. Frictional losses occur in the region of flow contraction, the stenosis itself and at the expansion area. Assuming a reasonably square edge at the contraction and expansion, losses in these areas, and, employing the Fanning friction factor, losses in the stenosis can be calculated. Investigation of the theoretically-derived frictional loss equation in an in vitro model of a long segment stenosis with various stenosis lengths and diameters showed a good correlation between manometrically determined pressure gradients and those calculated according to the Bernoulli equation and the frictional loss equation. On use of the frictional loss equation, the pressure gradients, however, were only slightly underestimated while those rendered by the Bernoulli equation were clearly underestimated. In vitro data suggest that a long segment stenosis existed when the obstructive length was greater than twice the obstructive diameter for each 10,000 Reynolds numbers.

  1. Effect of Stepwise Pressure Change on Porosity Evolution during Directional Solidification in Small Cylindrical Channels

    NASA Technical Reports Server (NTRS)

    Grugel, R.N.; Lee, C.P.; Cox, M.C.; Blandford, B.T.; Anilkumar, A.V.

    2008-01-01

    Controlled directional solidification experiments were performed in capillary channels, using nitrogen-saturated succinonitrile, to examine the effect of an in-situ stepwise processing pressure increase on an isolated pore evolution. Two experiments were performed using different processing pressure input profiles. The results indicate that a processing pressure increase has a transient effect on pore growth geometry characterized by an initial phase of decreasing pore diameter, followed by a recovery phase of increasing pore diameter. The experimental results also show that processing pressure can be used as a control parameter to either increase or terminate porosity formation. A theoretical model is introduced which indicates that the pore formation process is limited by the diffusion of solute-gas through the melt, and that the observed response toa pressure increase is attributed to the re-equilibration of solute concentration in the melt associated with the increased melt pressure.

  2. A dramatic drop in blood pressure following prehospital GTN administration.

    PubMed

    Boyle, Malcolm J

    2007-03-01

    A male in his sixties with no history of cardiac chest pain awoke with chest pain following an afternoon sleep. The patient did not self medicate. The patient's observations were within normal limits, he was administered oxygen via a face mask and glyceryl trinitrate (GTN). Several minutes after the GTN the patient experienced a sudden drop in blood pressure and heart rate, this was rectified by atropine sulphate and a fluid challenge. There was no further deterioration in the patient's condition during transport to hospital. There are very few documented case like this in the prehospital scientific literature. The cause appears to be the Bezold-Jarish reflex, stimulation of the ventricular walls which in turn decreases sympathetic outflow from the vasomotor centre. Prehospital care providers who are managing any patient with a syncopal episode that fails to recover within a reasonable time frame should consider the Bezold-Jarisch reflex as the cause and manage the patient accordingly.

  3. Porosity Development of Single-Wall Carbon Nanohorn @Assemblies by High Pressure Compression

    NASA Astrophysics Data System (ADS)

    Bekyarova, E.; Murata, K.; Kaneko, K.; Yudasaka, M.; Kasuya, D.; Iijima, S.

    2002-03-01

    Pore structure modification of single-wall carbon nanohorns (SWNHs) after compression at high pressure was studied by physical adsorption and TEM. Dahlia-SWNHs were dispersed in ethanol, dried and compressed at high pressure. The adsorption studies show a remarkable development of porosity after compression. Thus, the surface area and micropore volume of compressed SWNHs double those of as-grown SWNHs. The changes in the pore size distribution, dramatic in the range 20-50 nm, will be discussed. It will be shown that dispersion of SWNHs in solvents, heat treatment in vacuum and oxygen before and after compression, alter the porosity development. Particular attention is focused on the compressed SWNHs as an efficient adsorbent for methane.

  4. A pressurized drop-tube furnace for coal reactivity studies

    NASA Astrophysics Data System (ADS)

    Ouyang, Shan; Yeasmin, Hasina; Mathews, Joseph

    1998-08-01

    The design and characterization of a pressurized drop-tube furnace for investigation of coal devolatilization, gasification, and combustion are presented. The furnace is designed for high-temperature, isothermal operation in a developing laminar flow regime. It can be operated at pressures up to 1600 kPa, and temperatures up to 1673 K, with variable reaction time, particle feeding rate, and with inert and various oxidizing atmospheres. Particle residence times can be varied between ˜0.02 and ˜10 s depending upon operating conditions and positions of injection and sampling probes. Observations ports are available for sample collections and for optical investigation of the reactions or temperature measurements. Characterization of gas temperature in the furnace shows that, although the gas temperature profile in the furnace is affected by the water-cooled injection probe, the furnace is able to achieve isothermal operation in a developing laminar flow regime. Results from a series of brown coal devolatilization tests demonstrated the suitability of the furnace for experiments in coal research.

  5. On Porosity Formation in Metal Matrix Composites Made with Dual-Scale Fiber Reinforcements Using Pressure Infiltration Process

    NASA Astrophysics Data System (ADS)

    Etemadi, Reihaneh; Pillai, Krishna M.; Rohatgi, Pradeep K.; Hamidi, Sajad Ahmad

    2015-05-01

    This is the first such study on porosity formation phenomena observed in dual-scale fiber preforms during the synthesis of metal matrix composites (MMCs) using the gas pressure infiltration process. In this paper, different mechanisms of porosity formation during pressure infiltration of Al-Si alloys into Nextel™ 3D-woven ceramic fabric reinforcements (a dual-porosity or dual-scale porous medium) are studied. The effect of processing conditions on porosity content of the ceramic fabric infiltrated by the alloys through the gas PIP (PIP stands for "Pressure Infiltration Process" in which liquid metal is injected under pressure into a mold packed with reinforcing fibers.) is investigated. Relative density (RD), defined as the ratio of the actual MMC density and the density obtained at ideal 100 pct saturation of the preform, was used to quantify the overall porosity. Increasing the infiltration temperature led to an increase in RD due to reduced viscosity of liquid metal and enhanced wettability leading to improved feedability of the liquid metal. Similarly, increasing the infiltration pressure led to enhanced penetration of fiber tows and resulted in higher RD and reduced porosity. For the first time, the modified Capillary number ( Ca*), which is found to predict formation of porosity in polymer matrix composites quite well, is employed to study porosity in MMCs made using PIP. It is observed that in the high Ca* regime which is common in PIP, the overall porosity shows a strong downward trend with increasing Ca*. In addition, the effect of matrix shrinkage on porosity content of the samples is studied through using a zero-shrinkage Al-Si alloy as the matrix; usage of this alloy as the matrix led to a reduction in porosity content.

  6. Using equilibrium thermodynamics to estimate pressure and porosity changes during reactive transport

    NASA Astrophysics Data System (ADS)

    Malvoisin, Benjamin; Podladchikov, Yury; Vrijmoed, Johannes

    2015-04-01

    Mineralogical reactions play a key role during transport in porous media by generating or consuming fluids and modifying the fluid pathways through volume changes. Here, we used a theoretical and numerical approach to determine the interplays between reaction, transport and deformation during metamorphic reactions. Mass conservations equations were written for a reacting system and a system of equations was obtained to describe the relationships between fluid pressure, porosity and three thermodynamic parameters (the density of the fluid, the density of the non-volatile solid and a function of the volume change). Thermodynamic parameters were calculated by energy minimization with PerpleX for three lithologies found in subduction zones: sedimentary, mafic and ultramafic rocks. The evolution of porosity and fluid pressure was predicted in several cases. First, the maximum pressure changes associated with volume change during reaction was estimated for univariant reactions. Then, multi-variant reactions were considered and the system of equations was solved with several assumptions. Typical equations for porosity waves were obtained by simplifying the system with a solid density as a simple function of pressure or with the assumption of a constant amount of non-volatile species. Numerical models were finally used to solve these equations for three cases: the dehydration of chlorite in mafic rocks (positive Clapeyron slope), the dehydration of serpentine in ultramafic rocks (negative Clapeyron slope) and the decarbonation of calcite (positive Clapeyron slope with a H2O-CO2 fluid). Such kind of models take into account the complexity of mineralogical reactions and allow to better understand the generation of fluid pathways in metamorphic rocks.

  7. Pressure drop and thrust predictions for transonic micronozzle flows

    NASA Astrophysics Data System (ADS)

    Gomez, J.; Groll, R.

    2016-02-01

    In this paper, the expansion of xenon, argon, krypton, and neon gases through a Laval nozzle is studied experimentally and numerically. The pressurized gases are accelerated through the nozzle into a vacuum chamber in an attempt to simulate the operating conditions of a cold-gas thruster for attitude control of a micro-satellite. The gases are evaluated at several mass flow rates ranging between 0.178 mg/s and 3.568 mg/s. The Re numbers are low (8-256) and the estimated values of Kn number lie between 0.33 and 0.02 (transition and slip-flow regime). Direct Simulation Monte Carlo (DSMC) and continuum-based simulations with a no-slip boundary condition are performed. The DSMC and the experimental results show good agreement in the range Kn > 0.1, while the Navier-Stokes results describe the experimental data more accurately for Kn < 0.05. Comparison between the experimental and Navier-Stokes results shows high deviations at the lower mass flow rates and higher Kn numbers. A relation describing the deviation of the pressure drop through the nozzle as a function of Kn is obtained. For gases with small collision cross sections, the experimental pressure results deviate more strongly from the no-slip assumption. From the analysis of the developed function, it is possible to correct the pressure results for the studied gases, both in the slip-flow and transition regimes, with four gas-independent accommodation coefficients. The thrust delivered by the cold-gas thruster and the specific impulse is determined based on the numerical results. Furthermore, an increase of the thickness of the viscous boundary layer through the diffuser of the micronozzle is observed. This results in a shock-less decrease of the Mach number and the flow velocity, which penalizes thrust efficiency. The negative effect of the viscous boundary layer on thrust efficiency can be lowered through higher values of Re and a reduction of the diffuser length.

  8. Resonances, radiation pressure and optical scattering phenomena of drops and bubbles

    NASA Technical Reports Server (NTRS)

    Marston, P. L.; Goosby, S. G.; Langley, D. S.; Loporto-Arione, S. E.

    1982-01-01

    Acoustic levitation and the response of fluid spheres to spherical harmonic projections of the radiation pressure are described. Simplified discussions of the projections are given. A relationship between the tangential radiation stress and the Konstantinov effect is introduced and fundamental streaming patterns for drops are predicted. Experiments on the forced shape oscillation of drops are described and photographs of drop fission are displayed. Photographs of critical angle and glory scattering by bubbles and rainbow scattering by drops are displayed.

  9. Porosity and pressure: Role of compaction disequilibrium in the development of geopressures in a Gulf Coast Pleistocene basin

    SciTech Connect

    Hart, B.S.; Flemings, P.B.; Deshpande, A. )

    1995-01-01

    Measured pressures in Pleistocene strata of the Eugene Island block 330 area of offshore Louisiana reach approx. nine-tenths of the lithostatic pressures below 2 km depth; three-fourths of these geopressures are due to compaction disequilibrium. We show the relation between effective stress and porosity for compacting sediments to be exponential in shallow, normally pressured strata, then use the relation to calculate fluid pressure at depth in geopressured strata. Measured pressures below 2 km exceed our predicted values. A plot of effective stress vs. porosity demonstrates that compaction disequilibrium accounts for about three-quarters of the overpressures. We infer that the remainder must be due to pore-pressure generation at depth that occurred after the rocks reached their present porosity. 22 refs., 5 figs.

  10. Linking the pressure dependency of elastic and electrical properties of porous rocks by a dual porosity model

    NASA Astrophysics Data System (ADS)

    Han, Tongcheng; Gurevich, Boris; Pervukhina, Marina; Clennell, Michael Ben; Zhang, Junfang

    2016-04-01

    Knowledge about the pressure dependency of elastic and electrical properties is important for a variety of geophysical applications. We present a technique to invert for the stiff and compliant porosity from velocity measurements made as a function of differential pressure on saturated sandstones. A dual porosity concept is used for dry rock compressibility and a squirt model is employed for the pressure and frequency dependent elastic properties of the rocks when saturated. The total porosity obtained from inversion shows satisfactory agreement with experimental results. The electrical cementation factor was determined using the inverted porosity in combination with measured electrical conductivity. It was found that cementation factor increased exponentially with increasing differential pressure during isostatic loading. Elastic compressibility, electrical cementation factor and electrical conductivity of the saturated rocks correlate linearly with compliant porosity, and electrical cementation factor and electrical conductivity exhibit linear correlations with elastic compressibility of the saturated rocks under loading. The results show that the dual porosity concept is sufficient to explain the pressure dependency of elastic, electrical and joint elastic-electrical properties of saturated porous sandstones.

  11. The effect of pressure on annular flow pressure drop in a small pipe

    SciTech Connect

    de Bertodano, M.A.L.; Beus, S.G.; Shi, Jian-Feng

    1996-09-01

    New experimental data was obtained for pressure drop and entrainment for annular up-flow in a vertical pipe. The 9.5 mm. pipe has an L/D ratio of 440 to insure fully developed annular flow. The pressure ranged from 140 kPa to 660 kPa. Therefore the density ratio was varied by a factor of four approximately. This allows the investigation of the effect of pressure on the interfacial shear models. Gas superficial velocities between 25 and 126 m/s were tested. This extends the range of previous data to higher gas velocities. The data were compared with well known models for interfacial shear that represent the state of the art. Good results were obtained when the model by Asali, Hanratty and Andreussi was modified for the effect of pressure. Furthermore an equivalent model was obtained based on the mixing length theory for rough pipes. It correlates the equivalent roughness to the film thickness.

  12. Effect of External Pressure Drop on Loop Heat Pipe Operating Temperature

    NASA Technical Reports Server (NTRS)

    Jentung, Ku; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    This paper discusses the effect of the pressure drop on the operating temperature in a loop heat pipe (LHP). Because the evaporator and the compensation chamber (CC) both contain two-phase fluid, a thermodynamic constraint exists between the temperature difference and the pressure drop for these two components. As the pressure drop increases, so will the temperature difference. The temperature difference in turn causes an increase of the heat leak from the evaporator to the CC, resulting in a higher CC temperature. Furthermore, the heat leak strongly depends on the vapor void fraction inside the evaporator core. Tests were conducted by installing a valve on the vapor line so as to vary the pressure drop, and by charging the LHP with various amounts of fluid. Test results verify that the LHP operating temperature increases with an increasing differential pressure, and the temperature increase is a strong function of the fluid inventory in the loop.

  13. Laboratory manual for static pressure drop experiments in LMFBR wire wrapped rod bundles

    SciTech Connect

    Burns, K.J.; Todreas, N.E.

    1980-07-01

    Purpose of this experiment is to determine both interior and edge subchannel axial pressure drops for a range of Reynolds numbers. The subchannel static pressure drop is used to calculate subchannel and bundle average friction factors, which can be used to verify existing friction factor correlations. The correlations for subchannel friction factors are used as input to computer codes which solve the coupled energy, continuity, and momentum equations, and are also used to develop flow split correlations which are needed as input to codes which solve only the energy equation. The bundle average friction factor is used to calculate the overall bundle pressure drop, which determines the required pumping power.

  14. Compressibility Effects on Heat Transfer and Pressure Drop in Smooth Cylindrical Tubes

    NASA Technical Reports Server (NTRS)

    Nielsen, Jack N

    1944-01-01

    An analysis is made to simplify pressure-drop calculations for nonadiabatic and adiabatic friction flow of air in smooth cylindrical tubes when the density changes due to heat transfer and pressure drop are appreciable. Solutions of the equation of motion are obtained by the use of Reynolds' analogy between heat transfer and skin friction. Charts of the solutions are presented for making pressure-drop calculations. A technique of using the charts to determine the position of a normal shock in a tube is described.

  15. LHe Flow Regime/Pressure Drop for D0 Solenoid at Steady State Conditions

    SciTech Connect

    Rucinski, R.; /Fermilab

    1993-03-03

    This paper describes in a note taking format what was learned from several sources on two phase liquid helium flow regimes and pressure drops as applied to the D-Zero solenoid upgrade project. Calculations to estimate the steady state conditions for the D-Zero solenoid at 5, 10 and 15 g/s are also presented. For the lower flow rates a stratified type regime can be expected with a pressure drop less than 0.5 psi. For the higher flow rate a more homogeneous flow regime can be expected with a pressure drop between 0.4 to 1.5 psi.

  16. Effect of Hydrostatic Pressure on the 3D Porosity Distribution and Mechanical Behavior of a High Pressure Die Cast Mg AZ91 Alloy

    NASA Astrophysics Data System (ADS)

    Sket, Federico; Fernández, Ana; Jérusalem, Antoine; Molina-Aldareguía, Jon M.; Pérez-Prado, María Teresa

    2015-09-01

    A limiting factor of high pressure die cast (HPDC) Mg alloys is the presence of porosity, which has a detrimental effect on the mechanical strength and gives rise to a large variability in the ductility. The application of hydrostatic pressure after casting is known to be beneficial to improve the mechanical response of HPDC Mg alloys. In this study, a combined experimental and simulation approach has been developed in order to investigate the influence of pressurization on the 3D porosity distribution and on the mechanical behavior of an HPDC Mg AZ91 alloy. Examination of about 10,000 pores by X-ray computed microtomography allowed determining the effect of hydrostatic pressure on the bulk porosity volume fraction, as well as the change in volume and geometry of each individual pore. The evolution of the 3D porosity distribution and mechanical behavior of a sub-volume containing 200 pores was also simulated by finite element analysis. Both experiments and simulations consistently revealed a decrease in the bulk porosity fraction and a bimodal distribution of the individual volume changes after the application of the pressure. This observation is associated with pores containing internal pressure as a result of the HPDC process. Furthermore, a decrease in the complexity factor with increasing volume change is observed experimentally and predicted by simulations. The pressure-treated samples have consistently higher plastic flow strengths.

  17. Heat transfer and pressure drop for air flow through enhanced passages

    SciTech Connect

    Obot, N.T.; Esen, E.B.

    1992-06-01

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effect depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.

  18. Heat transfer and pressure drop for air flow through enhanced passages. Final report

    SciTech Connect

    Obot, N.T.; Esen, E.B.

    1992-06-01

    An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics for laminar, transitional and turbulent flow of air through a smooth passage and twenty-three enhanced passages. The internal surfaces of all enhanced passages had spirally shaped geometries; these included fluted, finned/ribbed and indented surfaces. The Reynolds number (Re) was varied between 400 and 50000. The effect of heat transfer (wall cooling or fluid heating) on pressure drop is most significant within the transition region; the recorded pressure drop with heat transfer is much higher than that without heat transfer. The magnitude of this effect depends markedly on the average surface temperature and, to a lesser extent, on the geometric characteristics of the enhanced surfaces. When the pressure drop data are reduced as values of the Fanning friction factor(f), the results are about the same with and without heat transfer for turbulent flow, with moderate differences in the laminar and transition regions.

  19. Effect of static mixer geometry on flow mixing and pressure drop in marine scr applications

    NASA Astrophysics Data System (ADS)

    Park, Taewha; Sung, Yonmo; Kim, Taekyung; Lee, Inwon; Choi, Gyungmin; Kim, Duckjool

    2014-03-01

    Flow mixing and pressure drop characteristics for marine selective catalytic reduction applications were investigated numerically to develop an efficient static mixer. Two different mixers, line- and swirl-type, were considered. The effect of vane angles on the relative intensity, uniformity index, and pressure drop was investigated in a swirl-type mixer; these parameters are dramatically affected by the mixer geometry. The presence of a mixer, regardless of the mixer type, led to an improvement of approximately 20% in the mixing performance behind the mixer in comparison to not having a mixer. In particular, there was a tradeoff relationship between the uniformity and the pressure drop. Con­sidering the mixing performance and the pressure drop, the swirl-type mixer was more suitable than the line-type mixer in this study.

  20. Effects of pressure drop and superficial velocity on the bubbling fluidized bed incinerator.

    PubMed

    Wang, Feng-Jehng; Chen, Suming; Lei, Perng-Kwei; Wu, Chung-Hsing

    2007-12-01

    Since performance and operational conditions, such as superficial velocity, pressure drop, particles viodage, and terminal velocity, are difficult to measure on an incinerator, this study used computational fluid dynamics (CFD) to determine numerical solutions. The effects of pressure drop and superficial velocity on a bubbling fluidized bed incinerator (BFBI) were evaluated. Analytical results indicated that simulation models were able to effectively predict the relationship between superficial velocity and pressure drop over bed height in the BFBI. Second, the models in BFBI were simplified to simulate scale-up beds without excessive computation time. Moreover, simulation and experimental results showed that minimum fluidization velocity of the BFBI must be controlled in at 0.188-3.684 m/s and pressure drop was mainly caused by bed particles. PMID:18074287

  1. Liquid-metal pin-fin pressure drop by correlation in cross flow

    SciTech Connect

    Wang, Zhibi; Kuzay, T.M.; Assoufid, L.

    1994-08-01

    The pin-fin configuration is widely used as a heat transfer enhancement method in high-heat-flux applications. Recently, the pin-fin design with liquid-metal coolant was also applied to synchrotron-radiation beamline devices. This paper investigates the pressure drop in a pin-post design beamline mirror with liquid gallium as the coolant. Because the pin-post configuration is a relatively new concept, information in literature about pin-post mirrors or crystals is rare, and information about the pressure drop in pin-post mirrors with liquid metal as the coolant is even more sparse. Due to this the authors considered the cross flow in cylinder-array geometry, which is very similar to that of the pin-post, to examine the pressure drop correlation with liquid metals over pin fins. The cross flow of fluid with various fluid characteristics or properties through a tube bank was studied so that the results can be scaled to the pin-fin geometry with liquid metal as the coolant. Study lead to two major variables to influence the pressure drop: fluid properties, viscosity and density, and the relative length of the posts. Correlation of the pressure drop between long and short posts and the prediction of the pressure drop of liquid metal in the pin-post mirror and comparison with an existing experiment are addressed.

  2. Bed mixing and leachate recycling strategies to overcome pressure drop buildup in the biofiltration of hydrogen sulfide.

    PubMed

    Roshani, Babak; Torkian, Ayoob; Aslani, Hasan; Dehghanzadeh, Reza

    2012-04-01

    The effects of leachate recycling and bed mixing on the removal rate of H(2)S from waste gas stream were investigated. The experimental setup consisted of an epoxy-coated three-section biofilter with an ID of 8 cm and effective bed height of 120 cm. Bed material consisted of municipal solid waste compost and PVC bits with an overall porosity of 54% and dry bulk density of 0.456 g cm(-3). Leachate recycling had a positive effect of increasing elimination capacity (EC) up to 21 g S m(-3) bed h(-1) at recycling rates of 75 ml d(-1), but in the bed mixing period EC declined to 8 g S m(-3) bed h(-1). Pressure drop had a range of zero to 18 mm H(2)O m(-1) in the course of leachate recycling. Accumulation of sulfur reduced removal efficiency and increased pressure drop up to 110 mm H(2)O m(-1) filter during the bed mixing stage.

  3. Effect of bed pressure drop on performance of a CFB boiler

    SciTech Connect

    Hairui Yang; Hai Zhang; Shi Yang; Guangxi Yue; Jun Su; Zhiping Fu

    2009-05-15

    The effect of bed pressure drop and bed inventory on the performances of a circulating fluidized bed (CFB) boiler was studied. By using the state specification design theory, the fluidization state of the gas-solids flow in the furnace of conventional CFB boilers was reconstructed to operate at a much lower bed pressure drop by reducing bed inventory and control bed quality. Through theoretical analysis, it was suggested that there would exist a theoretical optimal value of bed pressure drop, around which the boiler operation can achieve the maximal combustion efficiency and with significant reduction of the wear of the heating surface and fan energy consumption. The analysis was validated by field tests carried out in a 75 t/h CFB boiler. At full boiler load, when bed pressure drop was reduced from 7.3 to 3.2 kPa, the height of the dense zone in the lower furnace decreased, but the solid suspension density profile in the upper furnace and solid flow rate were barely influenced. Consequently, the average heat transfer coefficient in the furnace was kept nearly the same and the furnace temperature increment was less than 17{sup o}C. It was also found that the carbon content in the fly ash decreased first with decreasing bed pressure drop and then increased with further increasing bed pressure drop. The turning point with minimal carbon content was referred to as the point with optimal bed pressure drop. For this boiler, at the optimum point the bed pressure was around 5.7 kPa with the overall excess air ratio of 1.06. When the boiler was operated around this optimal point, not only the combustion efficiency was improved, but also fan energy consumption and wear of heating surface were reduced. 23 refs., 6 figs., 4 tabs.

  4. Experimental microbubble generation by sudden pressure drop and fluidics

    NASA Astrophysics Data System (ADS)

    Franco Gutierrez, Fernando; Figueroa Espinoza, Bernardo; Aguilar Corona, Alicia; Vargas Correa, Jesus; Solorio Diaz, Gildardo

    2014-11-01

    Mass and heat transfer, as well as chemical species in bubbly flow are of importance in environmental and industrial applications. Microbubbles are well suited to these applications due to the large interface contact area and residence time. The objective of this investigation is to build devices to produce microbubbles using two methods: pressure differences and fluidics. Some characteristics, advantages and drawbacks of both methods are briefly discussed, as well as the characterization of the bubbly suspensions in terms of parameters such as the pressure jump and bubble equivalent diameter distribution. The authors acknowledge the support of Consejo Nacional de Ciencia y Tecnología.

  5. Novel cyclone empirical pressure drop and emissions with heterogeneous particulate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    New cyclone designs equally effective at controlling emissions that have smaller pressure losses would reduce both the financial and the environmental cost of procuring electricity. Tests were conducted with novel and industry standard 30.5 cm diameter cyclones at inlet velocities from 8 to 18 m s-...

  6. Pressure drop characteristics of cryogenic mixed refrigerant at macro and micro channel heat exchangers

    NASA Astrophysics Data System (ADS)

    Baek, Seungwhan; Jeong, Sangkwon; Hwang, Gyuwan

    2012-12-01

    Mixed Refrigerant-Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. The temperature glide effect is one of the major features of using mixed refrigerants since a recuperative heat exchanger in a MR-JT refrigerator is utilized for mostly two-phase flow. Although a pressure drop estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in MR-JT refrigerator heat exchanger designs, it has been rarely discussed so far. In this paper, macro heat exchangers and micro heat exchangers are compared in order to investigate the pressure drop characteristics in the experimental MR-JT refrigerator operation. The tube in tube heat exchanger (TTHE) is a well-known macro-channel heat exchanger in MR-JT refrigeration. Printed Circuit Heat Exchangers (PCHEs) have been developed as a compact heat exchanger with micro size channels. Several two-phase pressure drop correlations are examined to discuss the experimental pressure measurement results. The result of this paper shows that cryogenic mixed refrigerant pressure drop can be estimated with conventional two-phase pressure drop correlations if an appropriate flow pattern is identified.

  7. Investigation of pressure drop in capillary tube for mixed refrigerant Joule-Thomson cryocooler

    SciTech Connect

    Ardhapurkar, P. M.; Sridharan, Arunkumar; Atrey, M. D.

    2014-01-29

    A capillary tube is commonly used in small capacity refrigeration and air-conditioning systems. It is also a preferred expansion device in mixed refrigerant Joule-Thomson (MR J-T) cryocoolers, since it is inexpensive and simple in configuration. However, the flow inside a capillary tube is complex, since flashing process that occurs in case of refrigeration and air-conditioning systems is metastable. A mixture of refrigerants such as nitrogen, methane, ethane, propane and iso-butane expands below its inversion temperature in the capillary tube of MR J-T cryocooler and reaches cryogenic temperature. The mass flow rate of refrigerant mixture circulating through capillary tube depends on the pressure difference across it. There are many empirical correlations which predict pressure drop across the capillary tube. However, they have not been tested for refrigerant mixtures and for operating conditions of the cryocooler. The present paper assesses the existing empirical correlations for predicting overall pressure drop across the capillary tube for the MR J-T cryocooler. The empirical correlations refer to homogeneous as well as separated flow models. Experiments are carried out to measure the overall pressure drop across the capillary tube for the cooler. Three different compositions of refrigerant mixture are used to study the pressure drop variations. The predicted overall pressure drop across the capillary tube is compared with the experimentally obtained value. The predictions obtained using homogeneous model show better match with the experimental results compared to separated flow models.

  8. Experimental determination of pressure drop caused by wire gauze in an air stream

    NASA Technical Reports Server (NTRS)

    1925-01-01

    For several kinds of wire gauze the difference in static, dynamic and total or absolute pressure in front of and behind the gauze were determined for comparison with the pressure drop caused by an airplane radiator, such gauze being used on airplane models to represent the radiator.

  9. Negative pressures and spallation in water drops subjected to nanosecond shock waves

    DOE PAGESBeta

    Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; Koglin, Jason E.; Liang, Mengning; Aquila, Andrew L.; Robinson, Joseph S.; Gumerlock, Karl L.; Blaj, Gabriel; Sierra, Raymond G.; et al

    2016-05-16

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

  10. Negative Pressures and Spallation in Water Drops Subjected to Nanosecond Shock Waves.

    PubMed

    Stan, Claudiu A; Willmott, Philip R; Stone, Howard A; Koglin, Jason E; Liang, Mengning; Aquila, Andrew L; Robinson, Joseph S; Gumerlock, Karl L; Blaj, Gabriel; Sierra, Raymond G; Boutet, Sébastien; Guillet, Serge A H; Curtis, Robin H; Vetter, Sharon L; Loos, Henrik; Turner, James L; Decker, Franz-Josef

    2016-06-01

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below -100 MPa were reached in the drops. We model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures. PMID:27182751

  11. Active control of static pressure drop caused by hydraulic servo-actuator engage

    SciTech Connect

    Janlovic, J.

    1994-12-31

    Pressure drop caused by propagation of expansion waves in the source pipeline of fast high cyclic hydraulic actuator produces possible anomalies in its function. To prevent pressure drop it is possible to minimize wave effects by active control of actuator servo-valve throttle leakage. In the paper is presented synthesis of possible discrete active control of hydraulic actuator and its servo-valve for prevention expansion wave pressure drop. Control synthesis is based on static pressure increasing with decreasing of fluid flow velocity, which can be realized by lower throttle leakage. Some of the effects of assumed control are shown on corresponding diagrams of control valve throttle motion, piston displacement and its corresponding linear velocity.

  12. Effect of flameholder pressure drop on emissions and performance of premixed-prevaporized combustors

    NASA Technical Reports Server (NTRS)

    Duerr, R. A.; Lyons, V. J.

    1983-01-01

    Parametric tests were conducted to determine the effects of flameholder pressure drop on the emissions and performance of lean premixed-prevaporized combustors. A conical flameholder mounted in a diverging duct was tested with two values of flameholder blockage. Emissions of nitrogen oxides, carbon monoxide, carbon dioxide, and unburned hydrocarbons were measured for combustor entrance conditions of 600 to 800 K air temperature, 0.3 MPa to 0.5 MPa pressure, and 20 m/sec to 35 m/sec reference velocity. Jet A fuel was injected at flow rates corresponding to an equivalence ratio range from 0.8 down to the lean stability limit. Emission results for the high-blockage flameholder were a substantial improvement over the low-blockage emission results. A correlation of combustion efficiency with flameholder pressure drop was developed for pressure drops less than 9 percent.

  13. Negative Pressures and Spallation in Water Drops Subjected to Nanosecond Shock Waves.

    PubMed

    Stan, Claudiu A; Willmott, Philip R; Stone, Howard A; Koglin, Jason E; Liang, Mengning; Aquila, Andrew L; Robinson, Joseph S; Gumerlock, Karl L; Blaj, Gabriel; Sierra, Raymond G; Boutet, Sébastien; Guillet, Serge A H; Curtis, Robin H; Vetter, Sharon L; Loos, Henrik; Turner, James L; Decker, Franz-Josef

    2016-06-01

    Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below -100 MPa were reached in the drops. We model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.

  14. Experimental investigation of ice slurry flow pressure drop in horizontal tubes

    SciTech Connect

    Grozdek, Marino; Khodabandeh, Rahmatollah; Lundqvist, Per

    2009-01-15

    Pressure drop behaviour of ice slurry based on ethanol-water mixture in circular horizontal tubes has been experimentally investigated. The secondary fluid was prepared by mixing ethyl alcohol and water to obtain initial alcohol concentration of 10.3% (initial freezing temperature -4.4 C). The pressure drop tests were conducted to cover laminar and slightly turbulent flow with ice mass fraction varying from 0% to 30% depending on test conditions. Results from flow tests reveal much higher pressure drop for higher ice concentrations and higher velocities in comparison to the single phase flow. However for ice concentrations of 15% and higher, certain velocity exists at which ice slurry pressure drop is same or even lower than for single phase flow. It seems that higher ice concentration delay flow pattern transition moment (from laminar to turbulent) toward higher velocities. In addition experimental results for pressure drop were compared to the analytical results, based on Poiseulle and Buckingham-Reiner models for laminar flow, Blasius, Darby and Melson, Dodge and Metzner, Steffe and Tomita for turbulent region and general correlation of Kitanovski which is valid for both flow regimes. For laminar flow and low buoyancy numbers Buckingham-Reiner method gives good agreement with experimental results while for turbulent flow best fit is provided with Dodge-Metzner and Tomita methods. Furthermore, for transport purposes it has been shown that ice mass fraction of 20% offers best ratio of ice slurry transport capability and required pumping power. (author)

  15. Flow rate-pressure drop relation for deformable shallow microfluidic channels

    NASA Astrophysics Data System (ADS)

    Christov, Ivan C.; Cognet, Vincent; Stone, Howard A.

    2013-11-01

    Laminar flow in devices fabricated from PDMS causes deformation of the passage geometry, which affects the flow rate-pressure drop relation. Having an accurate flow rate-pressure drop relation for deformable microchannels is of importance given that the flow rate for a given pressure drop can be as much as 500% of the flow rate predicted by Poiseuille's law for a rigid channel. proposed a successful model of the latter phenomenon by heuristically coupling linear elasticity with the lubrication approximation for Stokes flow. However, their model contains a fitting parameter that must be found for each channel shape by performing an experiment. We present a perturbative derivation of the flow rate-pressure drop relation in a shallow deformable microchannel using Kirchoff-Love theory of isotropic quasi-static plate bending and Stokes' equations under a ``double lubrication'' approximation (i.e., the ratio of the channel's height to its width and of the channel's width to its length are both assumed small). Our result contains no free parameters and confirms Gervais et al.'s observation that the flow rate is a quartic polynomial of the pressure drop. ICC was supported by NSF Grant DMS-1104047 and the U.S. DOE through the LANL/LDRD Program; HAS was supported by NSF Grant CBET-1132835.

  16. Nucleate boiling pressure drop in an annulus: Book 5

    SciTech Connect

    Not Available

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. Nineteen test series and a total of 178 tests were performed. Testing addressed the effects of: Heat flux; pressure; helium gas; power tilt; ribs; asymmetric heat flux. This document consists solely of the plato file index from 11/87 to 11/90.

  17. A Validated All-Pressure Fluid Drop Model and Lewis Number Effects for a Binary Mixture

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1999-01-01

    The differences between subcritical liquid drop and supercritical fluid drop behavior are discussed. Under subcritical, evaporative high emission rate conditions, a film layer is present in the inner part of the drop surface which contributes to the unique determination of the boundary conditions; it is this film layer which contributes to the solution's convective-diffusive character. In contrast, under supercritical condition as the boundary conditions contain a degree of arbitrariness due to the absence of a surface, and the solution has then a purely diffusive character. Results from simulations of a free fluid drop under no-gravity conditions are compared to microgravity experimental data from suspended, large drop experiments at high, low and intermediary temperatures and in a range of pressures encompassing the sub-and supercritical regime. Despite the difference between the conditions of the simulations and experiments (suspension vs. free floating), the time rate of variation of the drop diameter square is remarkably well predicted in the linear curve regime. The drop diameter is determined in the simulations from the location of the maximum density gradient, and agrees well with the data. It is also shown that the classical calculation of the Lewis number gives qualitatively erroneous results at supercritical conditions, but that an effective Lewis number previously defined gives qualitatively correct estimates of the length scales for heat and mass transfer at all pressures.

  18. Deformation of drop due to radiation pressure of acoustic standing wave

    NASA Astrophysics Data System (ADS)

    Yamanaka, T.; Saito, M.; Kamimura, H.

    To investigate the deformation of a liquid drop due to radiation pressure of acoustic standing waves, an analytical and experimental study was carried out. An approximate axisymmetric figure of equilibrium is obtained. The experimental study was carried out in the laboratory by using a triaxial acoustic chamber. An injection syringe was placed at the center of the triaxial acoustic resonance chamber. Holding a small liquid drop at the pointed end of the syringe, deformations of the liquid drop were measured. Assuming an oblate spheroid for the deformation, the experimental results were compared with theory.

  19. Nucleate boiling pressure drop in an annulus: Book 2

    SciTech Connect

    Block, J.A.; Crowley, C.; Dolan, F.X.; Sam, R.G.; Stoedefalke, B.H.

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. Nineteen test series and a total of 178 tests were performed. Testing addressed the effects of: Heat flux; pressure; helium gas; power tilt; ribs; asymmetric heat flux.

  20. Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures

    NASA Technical Reports Server (NTRS)

    Reid, R. S.; Martin, J. J.; Yocum, D. J.; Stewart, E. T.

    2007-01-01

    Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 < r* < 0.83. These smooth tube data may serve as a reference to the heat transfer and pressure drop performance in annuli, tubes, and channels having helixes or spacer ribs, or other surfaces.

  1. Effect of superficial velocity on vaporization pressure drop with propane in horizontal circular tube

    NASA Astrophysics Data System (ADS)

    Novianto, S.; Pamitran, A. S.; Nasruddin, Alhamid, M. I.

    2016-06-01

    Due to its friendly effect on the environment, natural refrigerants could be the best alternative refrigerant to replace conventional refrigerants. The present study was devoted to the effect of superficial velocity on vaporization pressure drop with propane in a horizontal circular tube with an inner diameter of 7.6 mm. The experiments were conditioned with 4 to 10 °C for saturation temperature, 9 to 20 kW/m2 for heat flux, and 250 to 380 kg/m2s for mass flux. It is shown here that increased heat flux may result in increasing vapor superficial velocity, and then increasing pressure drop. The present experimental results were evaluated with some existing correlations of pressure drop. The best prediction was evaluated by Lockhart-Martinelli (1949) with MARD 25.7%. In order to observe the experimental flow pattern, the present results were also mapped on the Wang flow pattern map.

  2. Influence of ambient pressure on drop-size and velocity distributions in dense sprays

    SciTech Connect

    Jasuja, A.K.; Lefebvre, A.H.

    1994-12-31

    The primary aim of the research is to determine the capabilities of modern noninvasive diagnostics for characterizing the sprays produced by a practical gas turbine atomizer when operating at realistic engine conditions of pressure, fuel type, and fuel-air throughput. A single-velocity-component Phase Doppler Particle Analyzer is used to measure local variations of drop-size distributions and drop velocities along three spray radii at downstream distances from the atomizer of 50 and 70 mm. In the 50-mm plane, excessive signal rejection rates limit measurements to a maximum air pressure of 9 bar and a maximum kerosene flow rate of 18.6 g/s. At the 70-mm measurement plane, satisfactory results are obtained at air pressures up to 12 bar and fuel-flow rates up to 24.8 g/s. The results show that increases in ambient air pressure lead to larger mean drop sizes and lower mean drop velocities in the spray. This is attributed to the fact that the beneficial effect of an increase in air pressure in raising Weber number is more than offset by several adverse factors, all of which are related to the increase in fuel-flow rate that accompanies an increase in air pressure at constant fuel/air ratio.

  3. An improved correlation of the pressure drop in stenotic vessels using Lorentz's reciprocal theorem

    NASA Astrophysics Data System (ADS)

    Ji, Chang-Jin; Sugiyama, Kazuyasu; Noda, Shigeho; He, Ying; Himeno, Ryutaro

    2015-02-01

    A mathematical model of the human cardiovascular system in conjunction with an accurate lumped model for a stenosis can provide better insights into the pressure wave propagation at pathological conditions. In this study, a theoretical relation between pressure drop and flow rate based on Lorentz's reciprocal theorem is derived, which offers an identity to describe the relevance of the geometry and the convective momentum transport to the drag force. A voxel-based simulator V-FLOW VOF3D, where the vessel geometry is expressed by using volume of fluid (VOF) functions, is employed to find the flow distribution in an idealized stenosis vessel and the identity was validated numerically. It is revealed from the correlation that the pressure drop of NS flow in a stenosis vessel can be decomposed into a linear term caused by Stokes flow with the same boundary conditions, and two nonlinear terms. Furthermore, the linear term for the pressure drop of Stokes flow can be summarized as a correlation by using a modified equation of lubrication theory, which gives favorable results compared to the numerical ones. The contribution of the nonlinear terms to the pressure drop was analyzed numerically, and it is found that geometric shape and momentum transport are the primary factors for the enhancement of drag force. This work paves a way to simulate the blood flow and pressure propagation under different stenosis conditions by using 1D mathematical model.

  4. Nucleate boiling pressure drop in an annulus: Book 3

    SciTech Connect

    Block, J.A.; Crowley, C.; Dolan, F.X.; Sam, R.G.; Stoedefalke, B.H.

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. This document consists of data plots and summary files of temperature measurements.

  5. Nucleate boiling pressure drop in an annulus: Book 4

    SciTech Connect

    Block, J.A.; Crowley, C.; Dolan, F.X.; Sam, R.G.; Stoedefalke, B.H.

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. This document consists of data plots and summary files of temperature measurements.

  6. Nucleate boiling pressure drop in an annulus: Book 8

    SciTech Connect

    Not Available

    1992-11-01

    The application of the work described in this report is the production reactors at the Savannah River Site, and the context is nuclear reactor safety. The Loss of Coolant Accident (LOCA) scenario considered involves a double-ended break of a primary coolant pipe in the reactor. During a LOCA, the flow through portions of the reactor may reverse direction or be greatly reduced, depending upon the location of the break. The reduced flow rate of coolant (D{sub 2}O) through the fuel assembly channels of the reactor -- downflow in this situation -- can lead to boiling and to the potential for flow instabilities which may cause some of the fuel assembly channels to overheat and melt. That situation is to be avoided. The experimental approach is to provide a test annulus which simulates geometry, materials, and flow conditions in a Mark-22 fuel assembly (Coolant Channel 3) to the extent possible. The annulus has a full-scale geometry, and in fat uses SRL dummy hardware for the inner annulus wall in the ribbed geometry. The materials aluminum. The annulus is uniformly heated in the axial direction, but the circumferential heat flux can be varied to provide ``power tilt`` or asymmetric heating of the inner and outer annulus walls. The test facility uses H{sub 2}O rather than D{sub 2}O, but it includes the effects of dissolved helium gas present in the reactor. The key analysis approaches are: To compare the minima in the measured demand curves with analytical criteria, in particular the Saha-Zuber (1974) model; and to compare the pressure and temperature as a function of length in the annulus with an integral model for flow boiling in a heated channel. This document consists of tables of temperature measurements.

  7. A steady state pressure drop model for screen channel liquid acquisition devices

    NASA Astrophysics Data System (ADS)

    Hartwig, J. W.; Darr, S. R.; McQuillen, J. B.; Rame, E.; Chato, D. J.

    2014-11-01

    This paper presents the derivation of a simplified one dimensional (1D) steady state pressure drop model for flow through a porous liquid acquisition device (LAD) inside a cryogenic propellant tank. Experimental data is also presented from cryogenic LAD tests in liquid hydrogen (LH2) and liquid oxygen (LOX) to compare against the simplified model and to validate the model at cryogenic temperatures. The purpose of the experiments was to identify the various pressure drop contributions in the analytical model which govern LAD channel behavior during dynamic, steady state outflow. LH2 pipe flow of LAD screen samples measured the second order flow-through-screen (FTS) pressure drop, horizontal LOX LAD outflow tests determined the relative magnitude of the third order frictional and dynamic losses within the channel, while LH2 inverted vertical outflow tests determined the magnitude of the first order hydrostatic pressure loss and validity of the full 1D model. When compared to room temperature predictions, the FTS pressure drop is shown to be temperature dependent, with a significant increase in flow resistance at LH2 temperatures. Model predictions of frictional and dynamic losses down the channel compare qualitatively with LOX LADs data. Meanwhile, the 1D model predicted breakdown points track the trends in the LH2 inverted outflow experimental results, with discrepancies being due to a non-uniform injection velocity across the LAD screen not accounted for in the model.

  8. Testing of a 4 K to 2 K heat exchanger with an intermediate pressure drop

    SciTech Connect

    Knudsen, Peter N.; Ganni, Venkatarao

    2015-12-01

    Most large sub-atmospheric helium refrigeration systems incorporate a heat exchanger at the load, or in the distribution system, to counter-flow the sub-atmospheric return with the super-critical or liquid supply. A significant process improvement is theoretically obtainable by handling the exergy loss across the Joule-Thompson throttling valve supplying the flow to the load in a simple but different manner. As briefly outlined in previous publications, the exergy loss can be minimized by allowing the supply flow pressure to decrease to a sub-atmospheric pressure concurrent with heat exchange flow from the load. One practical implementation is to sub-divide the supply flow pressure drop between two heat exchanger sections, incorporating an intermediate pressure drop. Such a test is being performed at Jefferson Lab's Cryogenic Test Facility (CTF). This paper will briefly discuss the theory, practical implementation and test results and analysis obtained to date.

  9. Model calibration for pressure drop in a pulse-jet cleaned fabric filter

    NASA Astrophysics Data System (ADS)

    Koehler, John L.; David, Leith

    A model based on Darcy's law allows prediction of pressure drop in a pulse-jet cleaned fabric filter. The model considers the effects of filtration velocity, dust areal density added during one filtration cycle, and pulse pressure. Data used to calibrate the model were collected in experiments with three fabric surface treatments and three dusts conducted at three filtration velocities, for a total of 27 different experimental conditions. The fabric used was polyester felt with untreated, singed, or PTFE-laminated surface. The dusts used were granite, limestone and fly ash. Filtration velocities were 50,75 and 100 mm s -1. Dust areal density added during one filtration cycle was constant, as was pulse pressure. Under these conditions, fabric surface treatment alone largely determined the values for two of the three constants in the model; the third constant depends on pressure drop characteristics of the venturi at the top of each filter bag.

  10. Experimental Investigations on the Pressure Drop of a Two-cone Hydrocyclone for Separation Fine Particles from Waste Water

    NASA Astrophysics Data System (ADS)

    Zhao, Qingguo; Li, Weiqing; He, Wei; Xia, Guodong

    2010-03-01

    To separate fine particles from waste water, a novel hydrocyclone was designed which features two cone sections. It is expected that flowrate can be increased at high separation efficiency without additional demand of pressure drop. This paper presents experimental investigations on its pressure drop characteristics. In this paper, influences of flowrate, split ratio, protrudent length of vertex finder, inlet area, vortex finder diameter, and inlet type on pressure drop are comprehensively discussed. It is evidenced that proper operation range falls within q = 5˜10 m3/h, and that the flowrate of the novel two-cone hydrocyclone can be increased by 50˜60%. Pressure drop decreases with vortex finder diameter. Experimental data prove that pressure drop can be significantly affected by split ratio, which has not been explicitly pointed out in literatures on conventional single cone hydrocyclones. Especially, it has been found that protrudent length of vortex finder influences pressure drop in a complex way so that there is a maximum value in pressure drop-protrudent length curve. It is demonstrated that reduction of the inlet area by a half will make pressure drop increase by about 78%. In comparison, involute form of fluid flow channel of inlets makes pressure drop lower than cycloid form.

  11. Prediction of pressure drop in fluid tuned mounts using analytical and computational techniques

    NASA Astrophysics Data System (ADS)

    Lasher, William C.; Khalilollahi, Amir; Mischler, John; Uhric, Tom

    1993-11-01

    A simplified model for predicting pressure drop in fluid tuned isolator mounts was developed. The model is based on an exact solution to the Navier-Stokes equations and was made more general through the use of empirical coefficients. The values of these coefficients were determined by numerical simulation of the flow using the commercial computational fluid dynamics (CFD) package FIDAP.

  12. An experimental study of heat transfer and pressure drop characteristics of divergent wavy minichannels using nanofluids

    NASA Astrophysics Data System (ADS)

    Dominic, A.; Sarangan, J.; Suresh, S.; Devahdhanush, V. S.

    2016-07-01

    An experimental investigation was conducted to study the heat transfer and pressure drop characteristics of an array of wavy divergent minichannels and the results were compared with wavy minichannels with constant cross-section. The experiment was conducted in hydro dynamically developed and thermally developing laminar and transient regimes. The minichannel heat sink array consisted of 15 rectangular channels machined on a 30 × 30 mm2 and 11 mm thick Aluminium substrate. Each minichannel was of 0.9 mm width, 1.8 mm pitch and the depth was varied from 1.3 mm at entrance to 3.3 mm at exit for the divergent channels. DI water and 0.5 and 0.8 % concentrations of Al2O3/water nanofluid were used as working fluids. The Reynolds number was varied from 700 to 3300 and the heat flux was maintained at 45 kW/m2. The heat transfer and pressure drop of these minichannels were analyzed based on the experimental results obtained. It was observed that the heat transfer performance of divergent wavy minichannels was 9 % higher and the pressure drop was 30-38 % lesser than that of the wavy minichannels with constant cross-section, in the laminar regime. Hence, divergent channel flows can be considered one of the better ways to reduce pressure drop. The performance factor of divergent wavy minichannels was 115-126 % for water and 110-113 % for nanofluids.

  13. Pressure drop and pumping power for fluid flow through round tubes

    NASA Technical Reports Server (NTRS)

    Jelinek, D.

    1973-01-01

    Program, written for Hewlett-Packard 9100A electronic desk computer provides convenient and immediate solution to problem of calculating pressure drop and fluid pumping power for flow through round tubes. Program was designed specifically for steady-state analysis and assumes laminar flow.

  14. Determining Seed Cotton Mass Flow Rate by Pressure Drop Across the Blowbox: Gin Testing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate measurement of the mass flow rate of seed cotton is needed for control and monitoring purposes in gins. A system was developed that accurately predicted mass flow rate based on the static pressure drop measured across the blowbox and the air velocity and temperature entering the blowbox usi...

  15. Determining Seed Cotton Mass Flow Rate by Pressure Drop Across a Blowbox: Gin Testing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate measurement of the mass flow rate of seed cotton is needed for control and monitoring purposes in gins. A system was developed that accurately predicted mass flow rate based on the static pressure drop measured across the blowbox and the air velocity and temperature entering the blowbox. Ho...

  16. Impact of flow regime on pressure drop increase and biomass accumulation and morphology in membrane systems.

    PubMed

    Vrouwenvelder, J S; Buiter, J; Riviere, M; van der Meer, W G J; van Loosdrecht, M C M; Kruithof, J C

    2010-02-01

    Biomass accumulation and pressure drop development have been studied in membrane fouling simulators at different flow regimes. At linear flow velocities as applied in practice in spiral wound nanofiltration (NF) and reverse osmosis (RO) membranes, voluminous and filamentous biofilm structures developed in the feed spacer channel, causing a significant increase in feed channel pressure drop. Elevated shear by both single phase flow (water) and two phase flow (water with air sparging: bubble flow) caused biofilm filaments and a pressure drop increase. The amount of accumulated biomass was independent of the applied shear, depending on the substrate loading rate (product of substrate concentration and linear flow velocity) only. The biofilm streamers oscillated in the passing water. Bubble flow resulted in a more compact and less filamentous biofilm structure than single phase flow, causing a much lower pressure drop increase. The biofilm grown under low shear conditions was more easy to remove during water flushing compared to a biofilm grown under high shear. To control biofouling, biofilm structure may be adjusted using biofilm morphology engineering combined with biomass removal from membrane elements by periodic reverse flushing using modified feed spacers. Potential long and short term consequences of flow regimes on biofilm development are discussed. Flow regimes manipulate biofilm morphology affecting membrane performance, enabling new approaches to control biofouling.

  17. Pressure drop reduction phenomenon of slush nitrogen flow in a horizontal pipe

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide

    2011-07-01

    Cryogenic slush fluids, such as slush hydrogen and slush nitrogen, are two-phase single-component fluids containing solid particles in a liquid. Their density and refrigerant capacity are greater than those of a liquid-state fluid alone. Owing to these advantages, there are high expectations for use of slush fluids in various applications such as a clean-energy fuel, fuel for space-planes to improve the efficiency of transportation and storage, and as a refrigerant for high-temperature superconducting power machines. Experimental tests were performed with slush nitrogen to obtain the frictional pressure drop flowing in a horizontal pipe with an inner diameter of 15 mm and a length of 400 mm. The primary objective of the study was to investigate the pressure drop reduction phenomenon according to changes in velocity and solid fraction. The pressure drop correlation between the friction factor and the Reynolds number was obtained, and an empirical correlation between them was derived. The flow pattern for slush nitrogen inside a pipe and the behavior of solid particles were observed using a high-speed video camera and the PIV method. From the experimental results, the pressure drop reduction phenomenon emerged clearly when the flow velocity was higher than 3.6 m/s and the flow pattern of solid particles inside the pipe was pseudo-homogeneous.

  18. Pressure drop of slush nitrogen flow in converging-diverging pipes and corrugated pipes

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Okuyama, Jun; Nakagomi, Kei; Takahashi, Koichi

    2012-12-01

    Cryogenic slush fluids such as slush hydrogen and slush nitrogen are solid-liquid, two-phase fluids. As a functional thermal fluid, there are high expectations for use of slush fluids in various applications such as fuels for spacecraft engines, clean-energy fuels to improve the efficiency of transportation and storage, and as refrigerants for high-temperature superconducting equipment. Experimental flow tests were performed using slush nitrogen to elucidate pressure-drop characteristics of converging-diverging (C-D) pipes and corrugated pipes. In experimental results regarding pressure drop in two different types of C-D Pipes, i.e., a long-throated pipe and a short-throated pipe, each having an inner diameter of 15 mm, pressure drop for slush nitrogen in the long-throated pipe at a flow velocity of over 1.3 m/s increased by a maximum of 50-60% as compared to that for liquid nitrogen, while the increase was about 4 times as compared to slush nitrogen in the short-throated pipe. At a flow velocity of over 1.5 m/s in the short-throated pipe, pressure drop reduction became apparent, and it was confirmed that the decrease in pressure drop compared to liquid nitrogen was a maximum of 40-50%. In the case of two different types of corrugated pipes with an inner diameter of either 12 mm or 15 mm, a pressure-drop reduction was confirmed at a flow velocity of over 2 m/s, and reached a maximum value of 37% at 30 wt.% compared to liquid nitrogen. The greater the solid fractions, the smaller the pipe friction factor became, and the pipe friction factor at the same solid fraction showed a constant value regardless of the Reynolds number. From the observation of the solid particles' behavior using a high-speed video camera and the PIV method, the pressure-drop reduction mechanisms for both C-D and corrugated pipes were demonstrated.

  19. Pressure-drop reduction and heat-transfer deterioration of slush nitrogen in horizontal pipe flow

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Nakagomi, Kei; Takahashi, Norifumi

    2011-10-01

    Cryogenic slush fluids such as slush hydrogen and slush nitrogen are two-phase, single-component fluids containing solid particles in a liquid. Since their density and refrigerant capacity are greater than those of liquid-state fluid alone, there are high expectations for the use of slush fluids in various applications such as clean-energy fuels, spacecraft fuels for improved efficiency in transportation and storage, and as refrigerants for high-temperature superconducting equipment. Experimental tests were performed using slush nitrogen to obtain the flow and heat-transfer characteristics in two different types of horizontal circular pipes with inner diameters of 10 and 15 mm. One of the primary objectives for the study was to investigate the effect of pipe diameter on the pressure-drop reduction and heat-transfer deterioration of slush nitrogen according to changes in the pipe flow velocity, solid fraction and heat flux. In the case of an inner diameter of 15 mm, pressure drop was reduced and heat-transfer characteristics deteriorated when the pipe flow velocity was higher than 3.6 m/s. On the other hand, in the case of an inner diameter of 10 mm, pressure drop was reduced and heat-transfer characteristics deteriorated when the pipe flow velocity was higher than 2.0 m/s. From these results, it can be seen that a larger pipe diameter produces a higher onset velocity for reducing pressure drop and deteriorating heat-transfer characteristics. Furthermore, based on observations using a high-speed video camera, it was confirmed that pressure drop was reduced and heat-transfer characteristics deteriorated when the solid particles migrated to the center of the pipe and the flow pattern of the solid particles inside the pipe was pseudo-homogeneous.

  20. Intercooler cooling-air weight flow and pressure drop for minimum drag loss

    NASA Technical Reports Server (NTRS)

    Reuter, J George; Valerino, Michael F

    1944-01-01

    An analysis has been made of the drag losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give a minimum drag loss for any given cooling effectiveness and, thus, a maximum power-plant net gain due to charge-air cooling. The drag losses considered in this analysis are those due to (1) the extra drag imposed on the airplane by the weight of the intercooler, its duct, and its supports and (2) the drag sustained by the cooling air in flowing through the intercooler and its duct. The investigation covers a range of conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and supercharger adiabatic efficiency. The optimum values of cooling air pressure drop and weight flow ratio are tabulated. Curves are presented to illustrate the results of the analysis.

  1. The oceanic response of the Turkish Straits System to an extreme drop in atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Book, Jeffrey W.; Jarosz, Ewa; Chiggiato, Jacopo; Beşiktepe, Åükrü

    2014-06-01

    Moorings across all four entry/exit sections of the Dardanelles Strait and the Bosphorus Strait simultaneously measured the response of the Turkish Straits System to the passage of a severe cyclonic storm that included an atmospheric pressure drop of more than 30 mbar in less than 48 h. The bottom pressure response at the Aegean Sea side of the Dardanelles Strait was consistent with an inverted barometer response, but the response at the other sections did not follow an inverted barometer, leading to a large bottom pressure gradient through the Turkish Straits System. Upper-layer flow toward the Aegean Sea was reversed by the storm and flow toward the Black Sea was greatly enhanced. Bottom pressure across the Sea of Marmara peaked 6 h after the passage of the storm's minimum pressure. The response on the Dardanelles side was a combination of sea elevation and pycnocline depth rise, and the response on the Bosphorus side was an even greater sea elevation rise and a drop in pycnocline depth. The peak in bottom pressure in the Sea of Marmara was followed by another reverse in the flow through the Dardanelles Strait as flow was then directed away from the Sea of Marmara in both straits. A simple conceptual model without wind is able to explain fluctuations in bottom pressure in the Sea of Marmara to a 0.89-0.96 level of correlation. This stresses the importance of atmospheric pressure dynamics in driving the mass flux of the Turkish Strait System for extreme storms.

  2. Pressure drop and temperature rise in He II flow in round tubes, Venturi flowmeters and valves

    NASA Technical Reports Server (NTRS)

    Walstrom, P. L.; Maddocks, J. R.

    1988-01-01

    Pressure drops in highly turbulent He II flow were measured in round tubes, valves, and Venturi flowmeters. Results are in good agreement with single-phase flow correlations for classical fluids. The temperature rise in flow in a round tube was measured, and found to agree well with predictions for isenthalpic expansion. Cavitation was observed in the venturis under conditions of low back pressure and high flow rate. Metastable superheating of the helium at the venturi throat was observed before the helium made a transition to saturation pressure.

  3. An experimental investigation of pressure drop of aqueous foam in laminar tube flow

    NASA Astrophysics Data System (ADS)

    Blackwell, B. F.; Sobolik, K. B.

    1987-04-01

    This report is the first of two detailing pressure-drop and heat-transfer measurements made at the Foam Flow Heat Transfer Loop. The work was motivated by a desire to extend the application of aqueous foam from petroleum drilling to geothermal drilling. Pressure-drop measurements are detailed in this report; a forthcoming report (SAND85-1922) will describe the heat-transfer measurements. The pressure change across a 2.4-m (8-ft) length of the 2.588-cm (1.019-in.) ID test section was measured for liquid volume fractions between 0.05 and 0.35 and average velocities between 0.12 and 0.80 m/s (0.4 and 2.6 ft/s). The resulting pressure-drop/flow-rate data were correlated to a theoretical model for a Bingham plastic. Simple expressions for the dynamic viscosity and the yield stress as a function of liquid volume fraction were estimated.

  4. Pressure drop and heat transfer characteristics of boiling water in sub-hundred micron channel

    SciTech Connect

    Bhide, R.R.; Singh, S.G.; Sridharan, Arunkumar; Duttagupta, S.P.; Agrawal, Amit

    2009-09-15

    The current work focuses on the pressure drop, heat transfer and stability in two phase flow in microchannels with hydraulic diameter of less than one hundred microns. Experiments were conducted in smooth microchannels of hydraulic diameter of 45, 65 {mu}m, and a rough microchannel of hydraulic diameter of 70 {mu}m, with deionised water as the working fluid. The local saturation pressure and temperature vary substantially over the length of the channel. In order to correctly predict the local saturation temperature and subsequently the heat transfer characteristics, numerical techniques have been used in conjunction with the conventional two phase pressure drop models. The Lockhart-Martinelli (liquid-laminar, vapour-laminar) model is found to predict the two phase pressure drop data within 20%. The instability in two phase flow is quantified; it is found that microchannels of smaller hydraulic diameter have lesser instabilities as compared to their larger counterparts. The experiments also suggest that surface characteristics strongly affect flow stability in the two phase flow regime. The effect of hydraulic diameter and surface characteristics on the flow characteristics and stability in two phase flow is seldom reported, and is of considerable practical relevance. (author)

  5. Microfluidic analysis of pressure drop and flow behavior in hypertensive micro vessels.

    PubMed

    Hu, Ruiqing; Li, Fen; Lv, Jiaqi; He, Ying; Lu, Detang; Yamada, Takashi; Ono, Naoki

    2015-01-01

    The retinal arterial network is the only source of the highly nutrient-consumptive retina, thus any insult on the arteries can impair the retinal oxygen and nutrient supply and affect its normal function. The aim of this work is to study the influences of vascular structure variation on the flow and pressure characteristics via microfluidic devices. Two sets of micro-channel were designed to mimic the stenosed microvessels and dichotomous branching structure in the retinal arteries. Three working fluids including red blood cell (RBC) suspension were employed to investigate the pressure drop in the stenosed channel. The flow behaviors of RBC suspensions inside the micro channels were observed using high speed camera system. Pressure drop of different working fluids and RBC velocity profiles in the stenosed channel were obtained. Moreover, hematocrit levels of RBC suspensions inside the bifurcated channels were analyzed from the sequential images of RBC flow. The results of the flow in the stenosed channel show that RBCs drift from the center of the channels, and RBC velocity is influenced not only by the inlet flow rate but also the interaction between RBCs. The measured pressure drops in the stenosed channel increase notably with the increase of fluid viscosity. Furthermore, the dimensionless pressure drop due to the stenosis decreases with Reynolds number. On the other hand, the results of flow through the bifurcated channels show that as the ratio of the daughter-branch width to the mother-channel width increases, the ratio of hematocrit in two connected branches (Ht/Hd) decreases, which is in favorable agreement with the available analysis results. PMID:26004808

  6. Effects of phosphoric acid sprayed into an incinerator furnace on the flue gas pressure drop at fabric filters.

    PubMed

    Takahashi, Shigetoshi; Hwang, In-Hee; Matsuto, Toshihiko

    2016-06-01

    Fabric filters are widely used to remove dust from flue gas generated by waste incineration. However, a pressure drop occurs at the filters, caused by growth of a dust layer on the filter fabric despite regular cleaning by pulsed-jet air. The pressure drop at the fabric filters leads to energy consumption at induced draft fan to keep the incinerator on negative pressure, so that its proper control is important to operate incineration facility efficiently. The pressure drop at fabric filters decreased whenever phosphoric acid wastewater (PAW) was sprayed into an incinerator for treating industrial waste. Operational data obtained from the incineration facility were analyzed to determine the short- and long-term effects of PAW spraying on the pressure drop. For the short-term effect, it was confirmed that the pressure drop at the fabric filters always decreased to 0.3-1.2kPa within about 5h after spraying PAW. This effect was expected to be obtained by about one third of present PAW spraying amount. However, from the long-term perspective, the pressure drop showed an increase in the periods of PAW spraying compared with periods for which PAW spraying was not performed. The pressure drop increase was particularly noticeable after the initial PAW spraying, regardless of the age and type of fabric filters used. These results suggest that present PAW spraying causes a temporary pressure drop reduction, leading to short-term energy consumption savings; however, it also causes an increase of the pressure drop over the long-term, degrading the overall operating conditions. Thus, appropriate PAW spraying conditions are needed to make effective use of PAW to reduce the pressure drop at fabric filters from a short- and long-term point of view.

  7. Effects of phosphoric acid sprayed into an incinerator furnace on the flue gas pressure drop at fabric filters.

    PubMed

    Takahashi, Shigetoshi; Hwang, In-Hee; Matsuto, Toshihiko

    2016-06-01

    Fabric filters are widely used to remove dust from flue gas generated by waste incineration. However, a pressure drop occurs at the filters, caused by growth of a dust layer on the filter fabric despite regular cleaning by pulsed-jet air. The pressure drop at the fabric filters leads to energy consumption at induced draft fan to keep the incinerator on negative pressure, so that its proper control is important to operate incineration facility efficiently. The pressure drop at fabric filters decreased whenever phosphoric acid wastewater (PAW) was sprayed into an incinerator for treating industrial waste. Operational data obtained from the incineration facility were analyzed to determine the short- and long-term effects of PAW spraying on the pressure drop. For the short-term effect, it was confirmed that the pressure drop at the fabric filters always decreased to 0.3-1.2kPa within about 5h after spraying PAW. This effect was expected to be obtained by about one third of present PAW spraying amount. However, from the long-term perspective, the pressure drop showed an increase in the periods of PAW spraying compared with periods for which PAW spraying was not performed. The pressure drop increase was particularly noticeable after the initial PAW spraying, regardless of the age and type of fabric filters used. These results suggest that present PAW spraying causes a temporary pressure drop reduction, leading to short-term energy consumption savings; however, it also causes an increase of the pressure drop over the long-term, degrading the overall operating conditions. Thus, appropriate PAW spraying conditions are needed to make effective use of PAW to reduce the pressure drop at fabric filters from a short- and long-term point of view. PMID:27040089

  8. Transitions and Pressure Drop Characteristics of Flow in Channels with Periodically Grooved Parts

    NASA Astrophysics Data System (ADS)

    Adachi, Takahiro; Uehara, Haruo

    Transitions of flow in periodically grooved channels and pressure drop characteristics are numerically investigated by assuming two-dimensional and fully developed flow fields. It is confirmed that a self-sustained oscillatory flow occurs at a critical Reynolds number from the steady-state flow as a result of Hopf bifurcation due to instability. The critical Reynolds numbers are obtained for various channel geometries. The ratio of the pressure drop of the grooved channel to that of the parallel-plate channel is also investigated. It is shown that the ratio is less than unity for the expanded channel geometries for the subcritical Reynolds numbers, whereas it increases above unity for the supercritical values. On the other hand, it always increases above unity for the contracted channel geometries.

  9. Pressure-drop Reduction and Heat-transfer Deterioration of Slush Nitrogen in Square Pipe flow

    NASA Astrophysics Data System (ADS)

    Ohira, Katsuhide; Nakagomi, Kei; Takahashi, Koichi; Aoki, Itsuo

    Pressure drop and heat transfer tests were carried out using slush nitrogen flowing in a horizontal square pipe at flow velocity between 1.0 and 4.9 m/s, with a mass solid fraction between 6 and 26 wt.%, and with heat fluxes of 0, 10 and 20 kW/m2. Pressure drop reduction became apparent at flow velocity of 2.5 m/s and over, with the maximum amount of reduction being 12% in comparison with liquid nitrogen, regardless of heating, while heat transfer deterioration became apparent at flow velocity of 1.0 m/s and over, with the maximum amount of deterioration being 16 and 21% at 10 and 20 kW/m2, respectively.

  10. Comparative studies on toluene removal and pressure drop in biofilters using different packing materials.

    PubMed

    Ryu, Hee Wook; Kim, So Jung; Cho, Kyung Suk

    2010-05-01

    To select the best available packing material for malodorous organic gases such as toluene and benzene, biofilter performance was compared in biofilters employed different packing materials including porous ceramic (celite), Jeju scoria (lava), a mixture of granular activated carbon (GAC) and celite (GAC/celite), and cubic polyurethane foam (PU). A toluene-degrading bacterium, Stenotrophomonas maltophilia T3-c, was used as the inoculum. The maximum elimination capacities in the celite, lava, and GAC/celite biofilters were 100, 130, and 110 gm(-3) hr(-1), respectively. The elimination capacity for the PU biofilter was approximately 350 g m(-3) hr(-1) at an inlet loading of approximately 430 g m(-3) hr(-1), which was 2 to 3.5 times higher than for the other biofilters. The pressure drop gradually increased in the GAC/ celite, celite and lava biofilters after 23 day due to bacterial over-growth, and the toluene removal efficiency remarkably decreased with increasing pressure drop. Backwashing method was not effective for the control of biomass in these biofilters. In the PU biofilter however, backwashing allowed maintenance of a pressure drop of 1 to 3 mm H2O m(-1) and a removal efficiency of > 80%, indicating that the PU was the best packing material for toluene removal among the packing materials tested.

  11. Pressure drop in fully developed, duct flow of dispersed liquid-vapor mixture at zero gravity

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Chao, B. T.; Soo, S. L.

    1990-01-01

    The dynamics of steady, fully developed dispersed liquid-vapor flow in a straight duct at 0-g is simulated by flowing water containing n-butyl benzoate droplets. Water and benzoate are immiscible and have identical density at room temperature. The theoretical basis of the simulation is given. Experiments showed that, for a fixed combined flow rate of water and benzoate, the frictional pressure drop is unaffected by large changes in the volume fraction of benzoate drops and their size distribution. Measured power spectra of the static wall pressure fluctuations induced by the turbulent water-benzoate flow also revealed that their dynamics is essentially unaltered by the presence of the droplets. These experimental findings, together with the theoretical analysis, led to the conclusion that the pressure drop in fully developed, dispersed liquid-vapor flow in straight ducts of constant cross section at 0-g is identical to that due to liquid flowing alone at the same total volumetric flow rate of the liquid-vapor mixture and, therefore, can be readily determined.

  12. Threshold concentrations of biomass and iron for pressure drop increase in spiral-wound membrane elements.

    PubMed

    Hijnen, W A M; Cornelissen, E R; van der Kooij, D

    2011-02-01

    In a model feed channel for spiral-wound membranes the quantitative relationship of biomass and iron accumulation with pressure drop development was assessed. Biofouling was stimulated by the use of tap water enriched with acetate at a range of concentrations (1-1000 μgCl(-1)). Autopsies were performed to quantify biomass concentrations in the fouled feed channel at a range of Normalized Pressure Drop increase values (NPD(i)). Active biomass was determined with adenosinetriphosphate (ATP) and the concentration of bacterial cells with Total Direct Cell count (TDC). Carbohydrates (CH) were measured to include accumulated extracellular polymeric substances (EPS). The paired ATP and CH concentrations in the biofilm samples were significantly (p<0.001; R(2)=0.62) correlated and both parameters were also significantly correlated with NPD(i) (p<0.001). TDC was not correlated with the pressure drop in this study. The threshold concentration for an NPD(i) of 100% was 3.7 ng ATP cm(-2) and for CH 8.1 μg CH cm(-2). Both parameters are recommended for diagnostic membrane autopsy studies. Iron concentrations of 100-400 mg m(-2) accumulated in the biofilm by adsorption were not correlated with the observed NPD(i), thus indicating a minor role of Fe particulates at these concentrations in fouling of spiral-wound membrane.

  13. Numerical analysis of the pressure drop in porous media flow with lattice Boltzmann (BGK) automata

    NASA Astrophysics Data System (ADS)

    Bernsdorf, J.; Brenner, G.; Durst, F.

    2000-07-01

    The lattice Boltzmann (LB) method is used for a detailed study on the origins of the pressure drop in porous media flow. In agreement with the experimental results [Durst et al., J. Non-Newtonian Fluid Mech. 22 (1987) 169] it is shown, that the elongation and the contraction of fluid elements is an important factor for the pressure loss in porous media flow, and that a significant error is made, when only shear forces are taken into account. To obtain the geometry information of the porous media for our simulations, we used the 3D computer tomography technique.

  14. Prevalence of detectable venous pressure drops expected with venous needle dislodgement.

    PubMed

    Ribitsch, Werner; Schilcher, Gernot; Hafner-Giessauf, Hildegard; Krisper, Peter; Horina, Jörg H; Rosenkranz, Alexander R; Schneditz, Daniel

    2014-01-01

    Venous needle dislodgement (VND) is a potentially fatal complication during hemodialysis (HD) treatment and the venous pressure monitor is the most widely used device for its detection. VND can only be detected by the venous sensor if the resulting pressure drop exceeds the difference between the actual venous pressure and the lower alarm limit. In clinical practice, the lower alarm limit is usually set 30-40 mmHg below the actual venous pressure to avoid a disproportionate high number of nuisance alarms. The aim of this study was to quantify the number of fistulas and grafts in a group of HD patients where venous pressure monitoring can be expected to detect VND. We determined intra-access pressures in 99 chronic HD patients. Sixty-five (65.7%) had a fistula and 34 (34.3%) had a prosthetic graft as a vascular access. Mean intra-access pressure (Pa ) in fistulas was 32.6 ± 23.5 mmHg, whereas in grafts mean Pa was 60.9 ± 19.5 mmHg. Nineteen (29.2%) of the fistulas and 32 (94.1%) of the grafts exhibited an intra-access pressure above 40 mmHg. Therefore, in our study nearly all grafts but only 29% of fistulas would fulfill the requirement for venous pressure monitoring to detect VND. PMID:24341865

  15. Effects of sudden expansion and contraction flow on pressure drops in the Stirling engine regenerator

    SciTech Connect

    Hamaguchi, K.; Yamashita, I.; Hirata, K.

    1998-07-01

    The flow losses in the regenerators greatly influence the performance of the Stirling engine. The losses mainly depend on fluid friction through the regenerator matrix, but are also generated in sudden expansion and contraction flow at the regenerator ends. The latter losses can't be neglected in the case of small area ratio (entrance area/cross-sectional area in regenerator). The pressure drops in regenerators are usually estimated assuming a uniform velocity distribution of working gas in the matrices. The estimation results, however, are generally smaller than practical data. The cross-sectional flow areas of the heater and cooler of typical Stirling engines are smaller than the cross- sectional area of the regenerator. The effects of the small flow passage on the velocity distribution of working fluid in the matrix, that is, a flow transition from tubes or channels to a regenerator matrix, can be often confirmed by the discolored matrix. Especially, the lack of a uniform distribution of velocity in the matrix causes increased flow loss and decreased thermal performance. So, it is necessary to understand the quantitative effects of the sudden change in flow area at the regenerator ends on the velocity distribution and pressure drop. In this paper, using matrices made of stacks of wire screens, the effects of the entrance and exit areas and the length of the regenerator on pressure drops are examined by an unidirectional steady flow apparatus. The experimental data are arranged in an empirical equation. The lack of a uniformity of velocity distribution is visualized using smoke-wire methods. The empirical equation presented is applied to the estimation of pressure loss in an actual engine regenerator. The applicability of the equation is examined by comparison of estimated value with engine data in pressure loss.

  16. Determination of the cathode and anode voltage drops in high power low-pressure amalgam lamps

    SciTech Connect

    Vasilyak, L. M.; Vasiliev, A. I. Kostyuchenko, S. V.; Sokolov, D. V.; Startsev, A. Yu.; Kudryavtsev, N. N.

    2011-12-15

    For the first time, cathode and anode drops of powerful low-pressure amalgam lamps were measured. The lamp discharge current is 3.2 A, discharge current frequency is 43 kHz, linear electric power is 2.4 W/cm. The method of determination of a cathode drop is based on the change of a lamp operating voltage at variation of the electrode filament current at constant discharge current. The total (cathode plus anode) drop of voltage was measured by other, independent ways. The maximum cathode fall is 10.8 V; the anode fall corresponding to the maximal cathode fall is 2.4 V. It is shown that in powerful low pressure amalgam lamps the anode fall makes a considerable contribution (in certain cases, the basic one) to heating of electrodes. Therefore, the anode fall cannot be neglected, at design an electrode and ballast of amalgam lamps with operating discharge current frequency of tens of kHz.

  17. Extraction of essential oils from Algerian myrtle leaves using instant controlled pressure drop technology.

    PubMed

    Berka-Zougali, Baya; Hassani, Aicha; Besombes, Colette; Allaf, Karim

    2010-10-01

    In the present work, the new extraction process of Détente Instantanée Contrôlée DIC (French, for instant controlled pressure drop) was studied, developed, quantitatively and qualitatively compared to the conventional hydrodistillation method for the extraction of essential oils from Algerian myrtle leaves. DIC was used as a thermomechanical treatment, DIC subjecting the product to a high-pressure saturated steam. The DIC cycle ends with an abrupt pressure drop towards vacuum, and this instantly leads to an autovaporization of myrtle volatile compounds. An immediate condensation in the vacuum tank produced a micro-emulsion of water and essential oils. Thus, an ultra-rapid cooling of residual leaves occurred, precluding any thermal degradation. An experimental protocol was designed with 3 independent variables: saturated steam pressure between 0.1 and 0.6 MPa, resulting in a temperature between 100 and 160°C, a total thermal processing time between 19 and 221 s, and between 2 and 6 DIC cycles. The essential oils yield was defined as the main dependent variable. This direct extraction gave high yields and high quality essential oil, as revealed by composition and antioxidant activity (results not shown). After this treatment, the myrtle leaves were recovered and hydrodistilled in order to quantify the essential oil content in residual DIC-treated samples. Scanning electron microscope (SEM) showed some modification of the structure with a slight destruction of cell walls after DIC treatment.

  18. Development of a new pressure dependent threshold superheated drop detector for neutrons

    NASA Astrophysics Data System (ADS)

    Rezaeian, Peiman; Raisali, Gholamreza; Akhavan, Azam; Ghods, Hossein; Hajizadeh, Bardia

    2015-03-01

    In this paper, a set of superheated drop detectors operated at different pressures is developed and fabricated by adding an appropriate amount of Freon-12 liquid on the free surface of the detector. The fabricated detectors have been used for determination of the threshold pressure for 2.89 MeV neutrons of a neutron generator in order to estimate the thermodynamic efficiency. Finally, knowing the thermodynamic efficiency of the detector and in a similar manner, the threshold pressure for 241Am-Be neutrons is determined and accordingly, the maximum neutron energy of the source spectrum is estimated. The maximum neutron energy of the 241Am-Be is estimated as 10.97±2.11 MeV. The agreement between this measured maximum energy and the reported value of the 241Am-Be neutron source shows that the method developed to apply pressure on the superheated drop detectors can be used to control the energy threshold of these detectors.

  19. The influence of the equivalent hydraulic diameter on the pressure drop prediction of annular test section

    NASA Astrophysics Data System (ADS)

    Al-Kayiem, A. H. H.; Ibrahim, M. A.

    2015-12-01

    The flow behaviour and the pressure drop throughout an annular flow test section was investigated in order to evaluate and justify the reliability of experimental flow loop for wax deposition studies. The specific objective of the present paper is to assess and highlight the influence of the equivalent diameter method on the analysis of the hydrodynamic behaviour of the flow and the pressure drop throughout the annular test section. The test section has annular shape of 3 m length with three flow passages, namely; outer thermal control jacket, oil annular flow and inner pipe flow of a coolant. The oil annular flow has internal and external diameters of 0.0422 m and 0.0801 m, respectively. Oil was re-circulated in the annular passage while a cold water-glycol mixture was re-circulated in the inner pipe counter currently to the oil flow. The experiments were carried out at oil Reynolds number range of 2000 to 17000, covering laminar, transition and turbulent flow regimes. Four different methods of equivalent diameter of the annulus have been considered in this hydraulic analysis. The correction factor model for frictional pressure drop was also considered in the investigations. All methods addressed the high deviation of the prediction from the experimental data, which justified the need of a suitable pressure prediction correlation for the annular test section. The conventional hydraulic diameter method is a convenient substitute for characterizing physical dimension of a non-circular duct, and it leads to fairly good correlation between turbulent fluid flow and heat transfer characteristic of annular ducts.

  20. Numerical investigation of cavitation flow inside spool valve with large pressure drop

    NASA Astrophysics Data System (ADS)

    Deng, Jian; Pan, Dingyi; Xie, Fangfang; Shao, Xueming

    2015-12-01

    Spool valves play an important role in fluid power system. Cavitation phenomena happen frequently inside the spool valves, which cause structure damages, noise and lower down hydrodynamic performance. A numerical tools incorporating the cavitation model, are developed to predict the flow structure and cavitation pattern in the spool valve. Two major flow states in the spool valve chamber, i.e. flow-in and flow-out, are studies. The pressure distributions along the spool wall are first investigated, and the results agree well with the experimental data. For the flow-in cases, the local pressure at the throttling area drops much deeper than the pressure in flow-out cases. Meanwhile, the bubbles are more stable in flow-in cases than those in flow-out cases, which are ruptured and shed into the downstream.

  1. Carbonate pore system evaluation using the velocity-porosity-pressure relationship, digital image analysis, and differential effective medium theory

    NASA Astrophysics Data System (ADS)

    Lima Neto, Irineu A.; Misságia, Roseane M.; Ceia, Marco A.; Archilha, Nathaly L.; Oliveira, Lucas C.

    2014-11-01

    Carbonate reservoirs exhibit heterogeneous pore systems and a wide variety of grain types, which affect the rock's elastic properties and the reservoir parameter relationships. To study the Albian carbonates in the Campos Basin, a methodology is proposed to predict the amount of microporosity and the representative aspect ratio of these inclusions. The method assumes three pore-space scales in two representative inclusion scenarios: 1) a macro-mesopore median aspect ratio from the thin-section digital image analysis (DIA) and 2) a microporosity aspect ratio predicted based on the measured P-wave velocities. Through a laboratory analysis of 10 grainstone core samples of the Albian age, the P- and S-wave velocities (Vp and Vs) are evaluated at effective pressures of 0-10 MPa. The analytical theories in the proposed methodology are functions of the aspect ratios from the differential effective medium (DEM) theory, the macro-mesopore system recognized from the DIA, the amount of microporosity determined by the difference between the porosities estimated from laboratorial helium-gas and the thin-section petrographic images, and the P-wave velocities under dry effective pressure conditions. The DIA procedure is applied to estimate the local and global parameters, and the textural implications concerning ultrasonic velocities and image resolution. The macro-mesopore inclusions contribute to stiffer rocks and higher velocities, whereas the microporosity inclusions contribute to softer rocks and lower velocities. We observe a high potential for this methodology, which uses the microporosity aspect ratio inverted from Vp to predict Vs with a good agreement. The results acceptably characterize the Albian grainstones. The representative macro-mesopore aspect ratio is 0.5, and the inverted microporosity aspect ratio ranges from 0.01 to 0.07. The effective pressure induced an effect of slight porosity reduction during the triaxial tests, mainly in the microporosity inclusions

  2. Effect of impregnation pressure and time on the porosity, structure and properties of polyacrylonitrile-fiber based carbon composites

    NASA Astrophysics Data System (ADS)

    Venugopalan, Ramani; Roy, Mainak; Thomas, Susy; Patra, A. K.; Sathiyamoorthy, D.; Tyagi, A. K.

    2013-02-01

    Carbon-carbon composites may find applications in critical parts of advanced nuclear reactors. A series of carbon-carbon composites were prepared using polyacrylonitrile (PAN) based carbon fibers. The materials were densified by impregnating two-dimensional (2D) preforms with liquid phenol formaldehyde resin at different pressures and for different periods of time and then carbonizing those by slowly heating at 1000 °C. Effects of the processing parameters on the structure of the composites were extensively studied. The study showed conclusively that open porosity decreased with increasing impregnation pressure, whereas impregnation time had lesser effect. Matrix-resin bonding also improved at higher pressure. d002 spacing decreased and ordering along c-axis increased with concomitant increase in sp2-carbon fraction at higher impregnation pressures. The fiber reinforced composites exhibited short range ordering of carbon atoms and satisfied structural conditions (d002 values) of amorphous carbon according to the turbostratic model for non-graphitic carbon materials. The composites had pellet-density of ˜85% of the theoretical value, low thermal expansion and negligible neutron-poisoning. They maintained structural integrity and retained disordered nature even on heat-treatment at ca. 1800 °C.

  3. Water management of proton exchange membrane fuel cell based on control of hydrogen pressure drop

    NASA Astrophysics Data System (ADS)

    Song, Mancun; Pei, Pucheng; Zha, Hongshan; Xu, Huachi

    2014-12-01

    Flooding experiments in various conditions are developed and the hydrogen pressure drop is investigated on a two-piece PEM fuel cell in this study. A two-level characteristic of hydrogen pressure drop is observed and analyzed in combination with water droplet accumulation in channels. Based on the characteristic, the flooding process can be divided into four continuous periods, which are the proper period, the humid period, the transitional period and the flooding period. The voltage shows the segmented tendency during these periods. Experimental results show that current and temperature have little influence on the growth rate of the two levels, while the effects of pressure and hydrogen stoichiometry are remarkable. The growth rate can be calculated through the channel dimensions and matches the experimental results well. Hydrogen purge is not a fundamental method to solve flooding. The end of the humid period should be the boundary before flooding. The moist section can be obtained in the beginning part of the humid period. In this section PEM fuel cell is neither flooding nor dehydration by adjusting the cell temperature, which is verified by two additional experiments. This water management is convenient and swift for PEM fuel cell applications and the fault diagnosis.

  4. Geometry-based pressure drop prediction in mildly diseased human coronary arteries.

    PubMed

    Schrauwen, J T C; Wentzel, J J; van der Steen, A F W; Gijsen, F J H

    2014-06-01

    Pressure drop (△p) estimations in human coronary arteries have several important applications, including determination of appropriate boundary conditions for CFD and estimation of fractional flow reserve (FFR). In this study a △p prediction was made based on geometrical features derived from patient-specific imaging data. Twenty-two mildly diseased human coronary arteries were imaged with computed tomography and intravascular ultrasound. Each artery was modelled in three consecutive steps: from straight to tapered, to stenosed, to curved model. CFD was performed to compute the additional △p in each model under steady flow for a wide range of Reynolds numbers. The correlations between the added geometrical complexity and additional △p were used to compute a predicted △p. This predicted △p based on geometry was compared to CFD results. The mean △p calculated with CFD was 855±666Pa. Tapering and curvature added significantly to the total △p, accounting for 31.4±19.0% and 18.0±10.9% respectively at Re=250. Using tapering angle, maximum area stenosis and angularity of the centerline, we were able to generate a good estimate for the predicted △p with a low mean but high standard deviation: average error of 41.1±287.8Pa at Re=250. Furthermore, the predicted △p was used to accurately estimate FFR (r=0.93). The effect of the geometric features was determined and the pressure drop in mildly diseased human coronary arteries was predicted quickly based solely on geometry. This pressure drop estimation could serve as a boundary condition in CFD to model the impact of distal epicardial vessels. PMID:24746019

  5. The impact of mass flow and masking on the pressure drop of air filter in heavy-duty diesel engine

    NASA Astrophysics Data System (ADS)

    Hoseeinzadeh, Sepideh; Gorji-Bandpy, Mofid

    2012-04-01

    This paper presents a computational fluid dynamics (CFD) calculation approach to predict and evaluate the impact of the mass-flow inlet on the pressure drop of turbocharger`s air filtfer in heavy-duty diesel engine. The numerical computations were carried out using a commercial CFD program whereas the inlet area of the air filter consisted of several holes connected to a channel. After entering through the channel, the air passes among the holes and enters the air filter. The effect of masking holes and hydraulic diameter is studied and investigated on pressure drop. The results indicate that pressure drop increase with decreasing of hydraulic diameter and masking of the holes has considerable affect on the pressure drop.

  6. Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space.

    PubMed

    Hallgren, Emma; Migeotte, Pierre-François; Kornilova, Ludmila; Delière, Quentin; Fransen, Erik; Glukhikh, Dmitrii; Moore, Steven T; Clément, Gilles; Diedrich, André; MacDougall, Hamish; Wuyts, Floris L

    2015-01-01

    It is a challenge for the human body to maintain stable blood pressure while standing. The body's failure to do so can lead to dizziness or even fainting. For decades it has been postulated that the vestibular organ can prevent a drop in pressure during a position change--supposedly mediated by reflexes to the cardiovascular system. We show--for the first time--a significant correlation between decreased functionality of the vestibular otolith system and a decrease in the mean arterial pressure when a person stands up. Until now, no experiments on Earth could selectively suppress both otolith systems; astronauts returning from space are a unique group of subjects in this regard. Their otolith systems are being temporarily disturbed and at the same time they often suffer from blood pressure instability. In our study, we observed the functioning of both the otolith and the cardiovascular system of the astronauts before and after spaceflight. Our finding indicates that an intact otolith system plays an important role in preventing blood pressure instability during orthostatic challenges. Our finding not only has important implications for human space exploration; they may also improve the treatment of unstable blood pressure here on Earth.

  7. Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space

    PubMed Central

    Hallgren, Emma; Migeotte, Pierre-François; Kornilova, Ludmila; Delière, Quentin; Fransen, Erik; Glukhikh, Dmitrii; Moore, Steven T.; Clément, Gilles; Diedrich, André; MacDougall, Hamish; Wuyts, Floris L.

    2015-01-01

    It is a challenge for the human body to maintain stable blood pressure while standing. The body’s failure to do so can lead to dizziness or even fainting. For decades it has been postulated that the vestibular organ can prevent a drop in pressure during a position change – supposedly mediated by reflexes to the cardiovascular system. We show – for the first time – a significant correlation between decreased functionality of the vestibular otolith system and a decrease in the mean arterial pressure when a person stands up. Until now, no experiments on Earth could selectively suppress both otolith systems; astronauts returning from space are a unique group of subjects in this regard. Their otolith systems are being temporarily disturbed and at the same time they often suffer from blood pressure instability. In our study, we observed the functioning of both the otolith and the cardiovascular system of the astronauts before and after spaceflight. Our finding indicates that an intact otolith system plays an important role in preventing blood pressure instability during orthostatic challenges. Our finding not only has important implications for human space exploration; they may also improve the treatment of unstable blood pressure here on Earth. PMID:26671177

  8. Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space.

    PubMed

    Hallgren, Emma; Migeotte, Pierre-François; Kornilova, Ludmila; Delière, Quentin; Fransen, Erik; Glukhikh, Dmitrii; Moore, Steven T; Clément, Gilles; Diedrich, André; MacDougall, Hamish; Wuyts, Floris L

    2015-01-01

    It is a challenge for the human body to maintain stable blood pressure while standing. The body's failure to do so can lead to dizziness or even fainting. For decades it has been postulated that the vestibular organ can prevent a drop in pressure during a position change--supposedly mediated by reflexes to the cardiovascular system. We show--for the first time--a significant correlation between decreased functionality of the vestibular otolith system and a decrease in the mean arterial pressure when a person stands up. Until now, no experiments on Earth could selectively suppress both otolith systems; astronauts returning from space are a unique group of subjects in this regard. Their otolith systems are being temporarily disturbed and at the same time they often suffer from blood pressure instability. In our study, we observed the functioning of both the otolith and the cardiovascular system of the astronauts before and after spaceflight. Our finding indicates that an intact otolith system plays an important role in preventing blood pressure instability during orthostatic challenges. Our finding not only has important implications for human space exploration; they may also improve the treatment of unstable blood pressure here on Earth. PMID:26671177

  9. A New Population Dataset on Dust Devil Pressure Drops : Setting the Stage for Mars Science Laboratory

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.

    2012-09-01

    A quarter of a century ago in the first in-situ study of dust devils on Mars, Ryan and Lucich (1983) rue that 'Unfortunately, we have been unable to find a terrestrial data set that permits a one-to-one comparison with our Mars data'. Remarkably, this state of affairs has largely persisted. Here I present a set of fixed station terrestrial field data, enabled by recent technological developments, which enables a direct comparison with dust devils (as indicated by vortex pressure drops) from Mars Pathfinder, Phoenix, and hopefully MSL Curiosity.

  10. The Interdependence of Plate Coupling Processes, Subduction Rate, and Asthenospheric Pressure Drop across Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Royden, L.; Holt, A.; Becker, T. W.

    2015-12-01

    One advantage of analytical models, in which analytic expressions are used for the various components of the subduction system, is the efficient exploration of parameter space and identification of the physical mechanisms controlling a wide breadth of slab kinematics. We show that, despite subtle differences in how plate interfaces and boundary conditions are implemented, results for single subduction from a 3-D semi-analytical model for subduction FAST (Royden & Husson, 2006; Jagoutz et al., 2015) and from the numerical finite-element model CitcomCU (Moresi & Gurnis, 1996, Zhong et al., 2006) are in excellent agreement when plate coupling (via shear stress on the plate interface) takes place in the FAST without the development of topographic relief at the plate boundary. Results from the two models are consistent across a variety of geometries, with fixed upper plate, fixed lower plate, and stress-free plate ends. When the analytical model is modified to include the development of topography above the subduction boundary, subduction rates are greatly increased, indicating a strong sensitivity of subduction to the mode of plate coupling. Rates of subduction also correlate strongly with the asthenospheric pressure drop across the subducting slab, which drives toroidal flow of the asthenosphere around the slab. When the lower plate is fixed, subduction is relatively slow and the pressure drop from below to above the slab is large, inhibiting subduction and slab roll-back. When the upper plate is fixed and when the plate ends are stress-free, subduction rates are approximately 50% faster and the corresponding asthenospheric pressure drop from below to above the slab is small, facilitating rapid subduction. This qualitative correlation between plate coupling processes, asthenospheric pressure drop, and rates of subduction can be extended to systems with more than one subduction zone (Holt et al., 2015 AGU Fall Abstract). Jagoutz, O., Royden, L., Holt, A. & Becker, T. W

  11. Isolation of Indonesian cananga oil using multi-cycle pressure drop process.

    PubMed

    Kristiawan, Magdalena; Sobolik, Vaclav; Allaf, Karim

    2008-05-30

    New process, instantaneous controlled pressure drop (DIC) was applied on Cananga odorata dry flowers with the aim to isolate essential oil. DIC is based on high temperature, short time heating followed by an abrupt pressure drop into a vacuum. A part of volatile compounds is carried away from flowers in the form of vapor (DIC direct oil) that evolves adiabatically during the pressure drop (proper isolation process) and the other part remains in the DIC-treated flowers (DIC residual oil). In the present paper, the effect of DIC cycle number (1-9) and heating time (4.3-15.7 min) on the availability of oil compounds was investigated at three levels of steam pressure (0.28, 0.4 and 0.6 MPa). The availability was defined as the amount of a compound in direct or residual oil divided by the amount of this compound in the reference oil extracted from non-treated flowers by chloroform during 2h. The total availability and yield of volatiles in the direct oil increased with pressure and cycle number. At a higher pressure, the effect of heating time was insignificant. The amount of oxygenated monoterpenes and other light oxygenated compounds (i.e. predominantly exogenous compounds) in the residual flowers was lower than in the direct oil and this amount decreased with cycle number. On the other hand, the availability of oxygenated sesquiterpenes and other heavy oxygenated compounds (i.e. predominantly endogenous compounds) in residual flowers exhibited a maximum for about five cycles and their quantity at this point was three times as much as in the direct oil. The total availability of each compound at 0.6 MPa was higher than one. The rapid DIC process (0.6 MPa, 8 cycles, 6 min) gave better results than steam distillation (16 h) concerning direct oil yield (2.8%dm versus 2.5%dm) and content of oxygenated compounds (72.5% versus 61.7%). PMID:18400225

  12. Effect of pore pressure on the elastic moduli, porosity and permeability of Berea sandstone and Leuders limestone

    SciTech Connect

    Thompson, T.W.; Kelkar, S.M.; Gray, K.E.

    1983-02-01

    The behavior of Berea sandstone and Leuders limestone under atmospheric and elevated pore pressures is reported. The porosity and the permeability changes, along with the static and dynamic moduli for these rocks have been determined under various conditions. The existing theoretical background pertinent to the study is reviewed along with the previous experimental work. The detailed descriptions and the discussions on the experimental procedure involved and the equipment utilized are presented. A discussion on the sources of experimental errors is included. It also includes the error propagation equations and relevant discussions on the data acquisition and analysis. The findings are summarized together with a discussion of the results. The conclusions drawn from these results are included. The bulk of the data acquired and the results computed from it are presented.

  13. Effects of slitted fins on the heat transfer and pressure drop characteristics of a compact heat exchanger

    SciTech Connect

    Kim, C.H.; Yun, J.Y.

    1996-12-31

    A compact heat exchanger which consists of air-cooled aluminum fins and copper tubes circulating refrigerant has been used in a cooling system for a long time. There are two key parameters to be seriously considered for a design of the heat exchanger and its performance improvement. These are the heat transfer rate and pressure drop coefficient which varies with the change of the tube size, its arrangement and the fin configuration. In here, a numerical study was carried to understand the effect of the fin configuration on the heat transfer and pressure drop of the heat exchanger. The diameter and the arrangement of tubes were fixed but three different types of the fin configuration were used to see its effect on the heat transfer capacity and the static pressure drop. The calculation results were compared with that of a flat plate fin. From the comparison, it was found that the slitted fins have higher pressure drop; however, they have higher heat transfer rate. It means that the simpler of the fin configuration, the lower pressure drop and heat transfer coefficients are obtained. It is mainly due to the discretisation of the thermal boundary layer on the fin surface to maximize the heat transfer to air. The slitted sides of fins act like obstacles in the airflow path. From the experimental result, it was found that the same trend in the variation of the heat transfer rate and the pressure drop with the change of the fin configuration was obtained.

  14. Prediction of two-phase pressure drop in heat exchanger for mixed refrigerant Joule-Thomson cryocooler

    NASA Astrophysics Data System (ADS)

    Ardhapurkar, P. M.; Atrey, M. D.

    2015-12-01

    The overall efficiency of a mixed refrigerant Joule-Thomson (MR J-T) cryocooler is governed by the performance of the recuperative heat exchanger. In the heat exchanger, the hot stream of the mixed refrigerant undergoes condensation at high pressure while the cold stream gets evaporated at low pressure. The pressure drop in the low pressure stream is crucial since it directly influences the achievable refrigeration temperature. However, experimental and theoretical studies related to two-phase pressure drop in mixtures at cryogenic temperatures, are limited. Therefore, the design of an efficient MR J-T cryocooler is a challenging task due to the lack of predictive tools. In the present work, the existing empirical correlations, which are commonly used for the prediction of pressure drop in the case of pure refrigerants, evaporating at near ambient conditions, are assessed for the mixed refrigerants. Experiments are carried out to measure the overall pressure drop in the evaporating cold stream of the tube-in-tube helically coiled heat exchanger. The predicted frictional pressure drop in the heat exchanger is compared with the experimental data. The suggested empirical correlations can be used to predict the hydraulic performance of the heat exchanger.

  15. Pressure drop in fully developed, turbulent, liquid-vapor annular flows in zero gravity

    NASA Technical Reports Server (NTRS)

    Sridhar, K. R.; Chao, B. T.; Soo, S. L.

    1992-01-01

    The prediction of frictional pressure drop in fully developed, turbulent, annular liquid-vapor flows in zero gravity using simulation experiments conducted on earth is described. The scheme extends the authors' earlier work on dispersed flows. The simulation experiments used two immiscible liquids of identical density, namely, water and n-butyl benzoate. Because of the lack of rigorous analytical models for turbulent, annular flows, the proposed scheme resorts to existing semiempirical correlations. Results based on two different correlations are presented and compared. Others may be used. It was shown that, for both dispersed and annular flow regimes, the predicted frictional pressure gradients in 0-g are lower than those in 1-g under otherwise identical conditions. The physical basis for this finding is given.

  16. Pressure Drop in Tortuosity/Kinking of the Internal Carotid Artery: Simulation and Clinical Investigation

    PubMed Central

    Wang, Lijun; Zhao, Feng; Wang, Daming; Hu, Shen; Liu, Jiachun; Zhou, Zhilun; Lu, Jun; Qi, Peng; Song, Shiying

    2016-01-01

    Background. Whether carotid tortuosity/kinking of the internal carotid artery leads to cerebral ischemia remains unclear. There is very little research about the hemodynamic variation induced by carotid tortuosity/kinking in the literature. The objective of this study was to research the blood pressure changes induced by carotid tortuosity/kinking. Methods. We first created a geometric model of carotid tortuosity/kinking. Based on hemodynamic boundary conditions, the hemodynamics of carotid tortuosity and kinking were studied via a finite element simulation. Then, an in vitro system was built to validate the numerical simulation results. The mean arterial pressure changes before and after carotid kinking were measured using pressure sensors in 12 patients with carotid kinking. Results. Numerical simulation revealed that the pressure drops increased with increases in the kinking angles. Clinical tests and in vitro experiments confirmed the numerical simulation results. Conclusions. Carotid kinking leads to blood pressure reduction. In certain conditions, kinking may affect the cerebral blood supply and be associated with cerebral ischemia. PMID:27195283

  17. Unidirectional gas flow in soil porosity resulting from barometric pressure cycles

    NASA Astrophysics Data System (ADS)

    Neeper, Donald A.; Stauffer, Philip

    2005-08-01

    During numerical simulation of air flow in the vadose zone, it was noticed that a small sinusoidal pressure would cause a gradual one-way migration of the pore gas. This was found to be a physical phenomenon, not a numerical artifact of the finite element simulation. The one-way migration occurs because the atmospheric pressure, and hence the air density, is slightly greater when air is flowing into the ground than when air is flowing out of the ground. A simple analytic theory of the phenomenon is presented, together with analytic calculations using actual barometric pressure data. In soil of one Darcy permeability, the one-way migration is of the order of a few tenths of a meter per year for either plane flow from ground surface or for radial flow from an open borehole. The migration is sufficiently small that it will have no practical consequences in most circumstances; however, investigators who conduct detailed numerical modeling should recognize that this phenomenon is not a numerical artifact in an apparently linear system.

  18. Fibrous filter efficiency and pressure drop in the viscous-inertial transition flow regime.

    SciTech Connect

    Sanchez, Andres L.; Brockmann, John E.; Dellinger, Jennifer Gwynne; Lucero, Daniel A.; Hubbard, Joshua A.; Servantes, Brandon Lee

    2011-10-01

    Fibrous filter pressure drop and aerosol collection efficiency were measured at low air pressures (0.2 to 0.8 atm) and high face velocities (5 to 20 meters per second) to give fiber Reynolds numbers in the viscous-inertial transition flow regime (1 to 16). In this regime, contemporary filtration theory based on Kuwabara's viscous flow through an ensemble of fibers under-predicts single fiber impaction by several orders of magnitude. Streamline curvature increases substantially as inertial forces become dominant. Dimensionless pressure drop measurements followed the viscous-inertial theory of Robinson and Franklin rather than Darcy's linear pressure-velocity relationship (1972). Sodium chloride and iron nano-agglomerate test aerosols were used to evaluate the effects of particle density and shape factor. Total filter efficiency collapsed when plotted against the particle Stokes and fiber Reynolds numbers. Efficiencies were then fitted with an impactor type equation where the cutpoint Stokes number and a steepness parameter described data well in the sharply increasing portion of the curve (20% to 80% efficiency). The cutpoint Stokes number was a linearly decreasing function of fiber Reynolds number. Single fiber efficiencies were calculated from total filter efficiencies and compared to contemporary viscous flow impaction theory (Stechkina et al. 1969), and numerical simulations from the literature. Existing theories under-predicted measured single fiber efficiencies although the assumption of uniform flow conditions for each successive layer of fibers is questionable; the common exponential relationship between single fiber efficiency and total filter efficiency may not be appropriate in this regime.

  19. Heat transfer and pressure drop in an annular channel with downflow

    NASA Astrophysics Data System (ADS)

    Dolan, F. X.; Crowley, C. J.; Qureshi, Z. H.

    The onset of a flow instability (OFI) determines the minimum flow rate for cooling in the flow channels of a nuclear fuel assembly. A test facility was constructed with full-scale models (length and diameter) of annular flow channels incorporating many instruments to measure heat transfer and pressure drop with downflow in the annulus. Tests were performed both with and without axial centering ribs at prototypical values of pressure, flow rate and uniform wall heat flux. The axial ribs have the effect of subdividing the annulus into quadrants, so the problem becomes one of parallel channel flow, unlike previous experiments in tubes (upflow and downflow). Other tests were performed to determine the effects if any of asymmetric and non-uniform circumferential wall heating, operating pressure level and dissolved gas concentration. Data from the tests are compared with models for channel heat transfer and pressure drop profiles in several regimes of wall heating from single-phase forced convection through partially and fully developed nucleate boiling. Minimum stable flow rates were experimentally determined as a function of wall heat flux and heat distribution and compared with the model for the transition to fully developed boiling which is a key criterion in determining the OFI condition in the channel. The heat transfer results in the channel without ribs are in excellent agreement with predictions from a computer model of the flow in the annulus and with empirical correlations developed from similar tests. The test results with centering ribs show that geometrical variations between the channels can lead to differences in subchannel behavior which can make the effect of the ribs and the geometry an important factor when assessing the power level at which the fuel assembly (and the reactor) can be operated to prevent overheating in the event of a loss-of-coolant-accident (LOCA).

  20. Flow distribution and pressure drop in parallel-channel configurations of planar fuel cells

    NASA Astrophysics Data System (ADS)

    Maharudrayya, S.; Jayanti, S.; Deshpande, A. P.

    Parallel-channel configurations for gas-distributor plates of planar fuel cells reduce the pressure drop, but give rise to the problem of severe flow maldistribution wherein some of the channels may be starved of the reactants. This study presents an analysis of the flow distribution through parallel-channel configurations. One-dimensional models based on mass and momentum balance equations in the inlet and exhaust gas headers are developed for Z- and U-type parallel-channel configurations. The resulting coupled ordinary differential equations are solved analytically to obtain closed-form solutions for the flow distribution in the individual channels and for the pressure drop over the entire distributor plate. The models have been validated by comparing the results with those obtained from three-dimensional computational fluid dynamics (CFD) simulations. Application of the models to typical fuel-cell distributor plates shows that severe maldistribution of flow may arise in certain cases and that this can be avoided by careful choice of the dimensions of the headers and the channels.

  1. Flow in microchannels with rough walls: flow pattern and pressure drop

    NASA Astrophysics Data System (ADS)

    Wang, Hao Li; Wang, Yuan

    2007-03-01

    In this paper perturbation methods are introduced to study the laminar flow in microchannels between two parallel plates with rough wall surfaces. By a coordinate transformation, the physical domain of the microchannel is transformed into the computational one. The relative roughness as a small parameter presents the governing equations resulting from the coordinate transformation. The equations are linearized through applying the perturbation method, and the spectral collocation method is employed to solve the perturbation equations. Furthermore, the boundary perturbation method is used to analyze the spatially-averaged pressure drop of the microchannel. The numerical results show that flow in microchannels with rough surfaces is quite different from Poiseuille flow: there exist apparent fluctuations and periodic variations of vorticity along the flow direction in the flow field; flow is viscously dominant under the conditions of a low Reynolds number and the flow separations happen in the troughs of wavy walls at a high Reynolds number. The spatially-averaged pressure drop being subject to the invariable flow rate could be greater than, equal to or even less than the theoretical value, which is qualitatively consistent with the results of the microfluidic experiments.

  2. Heat transfer and pressure drop characteristic of zinc-water nanofluid

    NASA Astrophysics Data System (ADS)

    Sonage, B. K.; Mohanan, P.

    2015-04-01

    Development of alternative working fluids with enhanced thermal properties is very much needed to replace conventional fluids. Colloidal solution of some base fluid with solid nanoparticles dispersed in it, which is called as nanofluid, is emerging as a promising alternative heat transfer fluid. Zinc, being ecofriendly material, is selected as dispersed phase in water to develop zinc-water (Zn-H2O) nanofluid. Zn-H2O nanofluid is synthesized by single step method and characterized. Thermophysical properties are estimated by available theoretical models. Estimated properties proved that nanofluid is having enhanced thermophysical properties compared to the base fluid due to which nanofluid can become potential working fluid for heat exchanging devices. Synthesized nanofluid is circulated through heat transfer loop to assess its performance in turbulent flow regime and at constant wall temperature condition. Heat transfer coefficient and pressure drop are estimated from experimental results and both are considered as performance evaluation criteria for heat transfer performance assessment. 83 % increase in Nusselt number with 9 % increase in pressure drop is observed for the nanofluid compared to water.

  3. Heat transfer and pressure drop characteristic of zinc-water nanofluid

    NASA Astrophysics Data System (ADS)

    Sonage, B. K.; Mohanan, P.

    2014-09-01

    Development of alternative working fluids with enhanced thermal properties is very much needed to replace conventional fluids. Colloidal solution of some base fluid with solid nanoparticles dispersed in it, which is called as nanofluid, is emerging as a promising alternative heat transfer fluid. Zinc, being ecofriendly material, is selected as dispersed phase in water to develop zinc-water (Zn-H2O) nanofluid. Zn-H2O nanofluid is synthesized by single step method and characterized. Thermophysical properties are estimated by available theoretical models. Estimated properties proved that nanofluid is having enhanced thermophysical properties compared to the base fluid due to which nanofluid can become potential working fluid for heat exchanging devices. Synthesized nanofluid is circulated through heat transfer loop to assess its performance in turbulent flow regime and at constant wall temperature condition. Heat transfer coefficient and pressure drop are estimated from experimental results and both are considered as performance evaluation criteria for heat transfer performance assessment. 83 % increase in Nusselt number with 9 % increase in pressure drop is observed for the nanofluid compared to water.

  4. Influence of peak inspiratory flow rates and pressure drops on inhalation performance of dry powder inhalers.

    PubMed

    Hira, Daiki; Okuda, Tomoyuki; Ichihashi, Mika; Mizutani, Ayano; Ishizeki, Kazunori; Okada, Toyoko; Okamoto, Hirokazu

    2012-01-01

    The aim of this study was to reveal the relationship between human inspiratory flow patterns and the concomitant drops in pressure in different inhalation devices, and the influence of the devices on inhalation performance. As a model formulation for inhalers, a physically mixed dry powder composed of salbutamol sulfate and coarse lactose monohydrate was selected. The drops in pressure at 28.3 L/min of three inhalation devices, Single-type, Dual-type, and Reverse-type, was 1.0, 5.1, and 8.7 kPa, respectively. Measurements of human inspiratory patterns revealed that although the least resistant device (Single) had large inter- and intra-individual variation of peak flow rate (PFR), the coefficients of variation of PFR of the three devices were almost the same. In tests with a human inspiratory flow simulator in vitro, inhalation performance was higher, but the variation in inhalation performance in the range of human flow patterns was wider, for the more resistant device. To minimize the intra- and inter-individual variation in inhalation performance for the model formulation in this study, a formulation design that allows active pharmaceutical ingredient to detach from the carrier with a lower inhalation flow rate is needed.

  5. An improved method for simultaneous determination of frictional pressure drop and vapor volume fraction in vertical flow boiling

    NASA Technical Reports Server (NTRS)

    Klausner, J. F.; Chao, B. T.; Soo, S. L.

    1990-01-01

    The two-phase frictional pressure drop and vapor volume fraction in the vertical boiling and adiabatic flow of the refrigerant, R11, have been simultaneously measured by a liquid balancing column and differential magnetic reluctance pressure transducers. An account is given of the experimental apparatus and procedure, data acquisition and analysis, and error estimation employed. All values of two-phase multipliers evaluated on the basis of the measured frictional pressure drop data in vertical upflow fall in the range bounded by the predictions of the Chisholm correlation and the homogeneous model.

  6. Numerical investigation of pressure drop and heat transfer in developing laminar and turbulent nanofluid flows

    NASA Astrophysics Data System (ADS)

    Ziaei-Rad, Masoud

    2013-07-01

    This paper concerns the study of laminar and turbulent force convection heat transfer and pressure drop between horizontal parallel plates with a nanofluid composed of Al2O3 and water. A set of governing equations are solved using a non-staggered SIMPLE procedure for the velocity-pressure coupling. For the convection-diffusion terms a power-law scheme is employed. A modified k-ɛ model with a two-layer technique for the near-wall region has been used to predict the turbulent viscosity. The effects of nanoparticle volume fraction in the base fluid on laminar and turbulent flow variables are presented and discussed. The velocity and temperature profiles, friction factor, pressure coefficient and Nusselt number at different Reynolds numbers in the entrance region for both the laminar and turbulent flow regimes are reported under different thermal boundary conditions. The results show that the effect of the presence of nanoparticles in the base fluid on hydraulic and thermal parameters for the turbulent flow is not very significant, while the rate of heat transfer for the laminar flow with nanoparticles is greater than that of the base liquid. Furthermore, the thermal boundary layer and consequently the Nusselt number more quickly reach their fully developed values by increasing the percentage of nanoparticles in the base fluid for the laminar flow regime, while no changes in the trend are observed for the turbulent flow.

  7. Quantitative determinations of antipyrine and benzocaine in ear drops by high-pressure liquid chromatography.

    PubMed

    Gupta, V D; Sachanandani, S

    1977-06-01

    Antipyrine and benzocaine were determined quantitatively in ear drops by high-pressure liquid chromatography on an octadecyltrichlorosilane permanently bonded to a Si-C column, using 0.02 M KH2PO4 in methanol-water as the mobile phase. Both compounds can be assayed in combination directly without interference from each other or from oxyquinoline sulfate (the preservative). The method is accurate, precise (estimated universe standard deviations of 0.68% for antipyrine and 1.18% for benzocaine), simple, and short (requires 30 min versus 2-3 hr by the NF method). The method was tried on a commercial product with excellent results and can be used in the presence of decomposition products.

  8. Two-phase pressure drop across a hydrofoil-based micro pin device using R-123

    SciTech Connect

    Kosar, Ali

    2008-05-15

    The two-phase pressure drop in a hydrofoil-based micro pin fin heat sink has been investigated using R-123 as the working fluid. Two-phase frictional multipliers have been obtained over mass fluxes from 976 to 2349 kg/m{sup 2} s and liquid and gas superficial velocities from 0.38 to 1.89 m/s and from 0.19 to 24 m/s, respectively. It has been found that the two-phase frictional multiplier is strongly dependent on flow pattern. The theoretical prediction using Martinelli parameter based on the laminar fluid and laminar gas flow represented the experimental data fairly well for the spray-annular flow. For the bubbly and wavy-intermittent flow, however, large deviations from the experimental data were recorded. The Martinelli parameter was successfully used to determine the flow patterns, which were bubbly, wavy-intermittent, and spray-annular flow in the current study. (author)

  9. Flow pattern and pressure drop of vertical upward gas-liquid flow in sinusoidal wavy channels

    SciTech Connect

    Nilpueng, Kitti; Wongwises, Somchai

    2006-06-15

    Flow patterns and pressure drop of upward liquid single-phase flow and air-water two-phase flow in sinusoidal wavy channels are experimentally studied. The test section is formed by a sinusoidal wavy wall of 1.00 m length with a wave length of 67.20mm, an amplitude of 5.76mm. Different phase shifts between the side walls of the wavy channel of 0{sup o}, 90{sup o} and 180{sup o} are investigated. The flow phenomena, which are bubbly flow, slug flow, churn flow, and dispersed bubbly flow are observed and recorded by high-speed camera. When the phase shifts are increased, the onset of the transition from the bubbly flow to the churn flow shifts to a higher value of superficial air velocity, and the regions of the slug flow and the churn flow are smaller. In other words, the regions of the bubbly flow and the dispersed bubbly flow are larger as the phase shift increases. The slug flow pattern is only found in the test sections with phase shifts of 0{sup o} and 90{sup o}. Recirculating gas bubbles are always found in the troughs of the corrugations. The recirculating is higher when the phase shifts are larger. The relationship between the two-phase multipliers calculated from the measured pressure drops, and the Martinelli parameter is compared with the Lockhart-Martinelli correlation. The correlation in the case of turbulent-turbulent condition is shown to fit the data very well for the phase shift of 0{sup o} but shows greater deviation when the phase shifts are higher. (author)

  10. Pressure drop and flow distribution in multiple parallel-channel configurations used in proton-exchange membrane fuel cell stacks

    NASA Astrophysics Data System (ADS)

    Maharudrayya, S.; Jayanti, S.; Deshpande, A. P.

    Single U- and Z-type parallel-channel configurations for gas distributor plates in planar fuel cells reduce the pressure drop but give rise to the problem of severe flow maldistribution wherein some of the channels may be starved of the reactants. In this paper, previous analytical solutions obtained for single U- and Z-type flow configurations are extended to multiple U- and multiple Z-type flow configurations of interest to fuel cell applications. Algorithms to calculate flow distribution and pressure drop in multiple U- and Z-type flow configurations are developed. The results are validated by comparison with those obtained from three-dimensional computational fluid dynamics (CFD) simulations. It is found that there is a significant improvement in the flow distribution in some configurations without paying for extra pressure drop. The possibility of unmatched distribution on the cathode and the anodes sides is also highlighted. Careful design of the flow configuration is therefore necessary for optimum performance.

  11. Experimental study on the flow patterns and the two-phase pressure drops in a horizontal impacting T-Junction

    NASA Astrophysics Data System (ADS)

    Bertani, C.; Malandrone, M.; Panella, B.

    2014-04-01

    The present paper analyzes the experimental results concerning the flow patterns and pressure drops in two-phase flow through a horizontal impacting T-junction, whose outlet pipes are aligned and perpendicular to the inlet pipe. The test section consists of plexiglass pipes with inner diameter of 10 mm. A mixture of water and air at ambient temperature and pressures up to 2.4 bar flows through the T-junction, with different splitting of flow rates in the two outlet branches; superficial velocities of air and water in the inlet pipe have been varied up to a maximum of 35 m/s and 3.5 m/s respectively. The flow patterns occurring in the inlet and branch pipes are compared with the predictions of the Baker and Taitel - Dukler maps. The pressure drops along the branches have been measured relatively to different splitting of the flow rate through the two branches and the pressure loss coefficients in the junction have been evaluated. Friction pressure drops have allowed us to evaluate two-phase friction multipliers, which have then been compared to the predictions of Lockhart-Martinelli, and Friedel correlations. Local pressure drops have been extrapolated at the junction centre and analyzed; the two-phase multiplier has been evaluated and compared with the predictions of Chisholm correlation; the value of the empirical coefficient that minimizes the discrepancy has also been evaluated.

  12. High-Pressure Transport Properties Of Fluids: Theory And Data From Levitated Drops At Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Ohsaka, Kenichi

    2003-01-01

    Although the high pressure multicomponent fluid conservation equations have already been derived and approximately validated for binary mixtures by this PI, the validation of the multicomponent theory is hampered by the lack of existing mixing rules for property calculations. Classical gas dynamics theory can provide property mixing-rules at low pressures exclusively. While thermal conductivity and viscosity high-pressure mixing rules have been documented in the literature, there is no such equivalent for the diffusion coefficients and the thermal diffusion factors. The primary goal of this investigation is to extend the low pressure mixing rule theory to high pressures and validate the new theory with experimental data from levitated single drops. The two properties that will be addressed are the diffusion coefficients and the thermal diffusion factors. To validate/determine the property calculations, ground-based experiments from levitated drops are being conducted.

  13. Comparison of pressure drop and filtration efficiency of particulate respirators using welding fumes and sodium chloride.

    PubMed

    Cho, Hyun-Woo; Yoon, Chung-Sik; Lee, Jin-Ho; Lee, Seung-Joo; Viner, Andrew; Johnson, Erik W

    2011-07-01

    Respirators are used to help reduce exposure to a variety of contaminants in workplaces. Test aerosols used for certification of particulate respirators (PRs) include sodium chloride (NaCl), dioctyl phthalate, and paraffin oil. These aerosols are generally assumed to be worst case surrogates for aerosols found in the workplace. No data have been published to date on the performance of PRs with welding fumes, a hazardous aerosol that exists in real workplace settings. The aim of this study was to compare the performance of respirators and filters against a NaCl aerosol and a welding fume aerosol and determine whether or not a correlation between the two could be made. Fifteen commercial PRs and filters (seven filtering facepiece, two replaceable single-type filters, and six replaceable dual-type filters) were chosen for investigation. Four of the filtering facepiece respirators, one of the single-type filters, and all of the dual-type filters contained carbon to help reduce exposure to ozone and other vapors generated during the welding process. For the NaCl test, a modified National Institute for Occupational Safety and Health protocol was adopted for use with the TSI Model 8130 automated filter tester. For the welding fume test, welding fumes from mild steel flux-cored arcs were generated and measured with a SIBATA filter tester (AP-634A, Japan) and a manometer in the upstream and downstream sections of the test chamber. Size distributions of the two aerosols were measured using a scanning mobility particle sizer. Penetration and pressure drop were measured over a period of aerosol loading onto the respirator or filter. Photos and scanning electron microscope images of clean and exposed respirators were taken. The count median diameter (CMD) and mass median diameter (MMD) for the NaCl aerosol were smaller than the welding fumes (CMD: 74 versus 216 nm; MMD: 198 versus 528 nm, respectively). Initial penetration and peak penetration were higher with the NaCl aerosol

  14. Comparison of pressure drop and filtration efficiency of particulate respirators using welding fumes and sodium chloride.

    PubMed

    Cho, Hyun-Woo; Yoon, Chung-Sik; Lee, Jin-Ho; Lee, Seung-Joo; Viner, Andrew; Johnson, Erik W

    2011-07-01

    Respirators are used to help reduce exposure to a variety of contaminants in workplaces. Test aerosols used for certification of particulate respirators (PRs) include sodium chloride (NaCl), dioctyl phthalate, and paraffin oil. These aerosols are generally assumed to be worst case surrogates for aerosols found in the workplace. No data have been published to date on the performance of PRs with welding fumes, a hazardous aerosol that exists in real workplace settings. The aim of this study was to compare the performance of respirators and filters against a NaCl aerosol and a welding fume aerosol and determine whether or not a correlation between the two could be made. Fifteen commercial PRs and filters (seven filtering facepiece, two replaceable single-type filters, and six replaceable dual-type filters) were chosen for investigation. Four of the filtering facepiece respirators, one of the single-type filters, and all of the dual-type filters contained carbon to help reduce exposure to ozone and other vapors generated during the welding process. For the NaCl test, a modified National Institute for Occupational Safety and Health protocol was adopted for use with the TSI Model 8130 automated filter tester. For the welding fume test, welding fumes from mild steel flux-cored arcs were generated and measured with a SIBATA filter tester (AP-634A, Japan) and a manometer in the upstream and downstream sections of the test chamber. Size distributions of the two aerosols were measured using a scanning mobility particle sizer. Penetration and pressure drop were measured over a period of aerosol loading onto the respirator or filter. Photos and scanning electron microscope images of clean and exposed respirators were taken. The count median diameter (CMD) and mass median diameter (MMD) for the NaCl aerosol were smaller than the welding fumes (CMD: 74 versus 216 nm; MMD: 198 versus 528 nm, respectively). Initial penetration and peak penetration were higher with the NaCl aerosol

  15. Study of Critical Heat Flux and Two-Phase Pressure Drop Under Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Abdollahian, Davood; Quintal, Joseph; Barez, Fred; Zahm, Jennifer; Lohr, Victor

    1996-01-01

    The design of the two-phase flow systems which are anticipated to be utilized in future spacecraft thermal management systems requires a knowledge of two-phase flow and heat transfer phenomena in reduced gravities. This program was funded by NASA headquarters in response to NRA-91-OSSA-17 and was managed by Lewis Research Center. The main objective of this program was to design and construct a two-phase test loop, and perform a series of normal gravity and aircraft trajectory experiments to study the effect of gravity on the Critical Heat Flux (CHF) and onset of instability. The test loop was packaged on two aircraft racks and was also instrumented to generate data for two-phase pressure drop. The normal gravity tests were performed with vertical up and downflow configurations to bound the effect of gravity on the test parameters. One set of aircraft trajectory tests was performed aboard the NASA DC-9 aircraft. These tests were mainly intended to evaluate the test loop and its operational performance under actual reduced gravity conditions, and to produce preliminary data for the test parameters. The test results were used to demonstrate the applicability of the normal gravity models for prediction of the two-phase friction pressure drop. It was shown that the two-phase friction multipliers for vertical upflow and reduced gravity conditions can be successfully predicted by the appropriate normal gravity models. Limited critical heat flux data showed that the measured CHF under reduced gravities are of the same order of magnitude as the test results with vertical upflow configuration. A simplified correlation was only successful in predicting the measured CHF for low flow rates. Instability tests with vertical upflow showed that flow becomes unstable and critical heat flux occurs at smaller powers when a parallel flow path exists. However, downflow tests and a single reduced gravity instability experiment indicated that the system actually became more stable with a

  16. Two-phase heat transfer and pressure drop of LNG during saturated flow boiling in a horizontal tube

    NASA Astrophysics Data System (ADS)

    Chen, Dongsheng; Shi, Yumei

    2013-12-01

    Two-phase heat transfer and pressure drop of LNG (liquefied natural gas) have been measured in a horizontal smooth tube with an inner diameter of 8 mm. The experiments were conducted at inlet pressures from 0.3 to 0.7 MPa with a heat flux of 8-36 kW m-2, and mass flux of 49.2-201.8 kg m-2 s-1. The effect of vapor quality, inlet pressure, heat flux and mass flux on the heat transfer characteristic are discussed. The comparisons of the experimental data with the predicted value by existing correlations are analyzed. Zou et al. (2010) correlation shows the best accuracy with 24.1% RMS deviation among them. Moreover four frictional pressure drop methods are also chosen to compare with the experimental database.

  17. Heat transfer and pressure drop in blade cooling channels with turbulence promoters

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Park, J. S.; Lei, C. K.

    1984-01-01

    Repeated rib roughness elements have been used in advanced turbine cooling designs to enhance the internal heat transfer. Often the ribs are perpendicular to the main flow direction so that they have an angle-of-attack of 90 deg. The objective of the project was to investigate the effect of rib angle-of-attack on the pressure drop and the average heat transfer coefficients in a square duct with two opposite rib-roughned walls for Reynolds number varied from 8000 to 80,000. The rib height-to-equivalent diameter ratio (e/D) was kept at a constant value of 0.063, the rib pitch-to-height ratio (P/e) was varied from 10 to 20, and the rib angle-of-attack (alpha) was varied from 90 deg to 60 deg to 45 deg to 30 deg respectively. Two types of entrance conditions were examined, namely, long duct and sudden contraction. The heat transfer coefficient distribution on the smooth side wall and the rough side wall at the entrance and the fully developed regions were measured. Thermal performance comparison indicated that the pumping power requirement for the rib with an oblique angle to the flow (alpha = 45 deg to 30 deg) was about 20 to 50 percent lower than the rib with a 90 deg angle to the flow for a given heat transfer duty.

  18. Impact of instantaneous controlled pressure drop on microstructural modification of green tea and its infusion quality.

    PubMed

    Wang, Yuefei; Xu, Ping; Feng, Liyun; Yang, Xianqiang; Qian, Lisheng

    2014-01-01

    Instantaneous controlled pressure drop (DIC) was applied to obtain a suitable cell disruption extent as a technology in green tea processing. Microstructural observations showed that DIC increased cell disruption in an even manner as reflected from loosened palisade, distorted cells, widened space between cells, disrupted and rearranged cellular membrane in tea leaves. Color difference determination supported that DIC could facilitate the release and transport of cell contents. DIC sample showed a rise in redness, over 2.5 times greater than the control after spreading naturally for 24 h. Chemical determination revealed a better infusion behavior of tea polyphenols and amino acids in green tea manufactured by DIC method both at high and low temperature. The increase in tea polyphenols content in liquor for the first brew from twisted and needle tea was about 35% and that from flat tea was about 15% in DIC method over the traditional processing. These results suggest that DIC process can be applied in green tea processing for both a traditional product and a new kind of tea capable of making with cold water.

  19. Comparative study of heat transfer and pressure drop during flow boiling and flow condensation in minichannels

    NASA Astrophysics Data System (ADS)

    Mikielewicz, Dariusz; Andrzejczyk, Rafał; Jakubowska, Blanka; Mikielewicz, Jarosław

    2014-09-01

    In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.

  20. Impact of instantaneous controlled pressure drop on microstructural modification of green tea and its infusion quality.

    PubMed

    Wang, Yuefei; Xu, Ping; Feng, Liyun; Yang, Xianqiang; Qian, Lisheng

    2014-01-01

    Instantaneous controlled pressure drop (DIC) was applied to obtain a suitable cell disruption extent as a technology in green tea processing. Microstructural observations showed that DIC increased cell disruption in an even manner as reflected from loosened palisade, distorted cells, widened space between cells, disrupted and rearranged cellular membrane in tea leaves. Color difference determination supported that DIC could facilitate the release and transport of cell contents. DIC sample showed a rise in redness, over 2.5 times greater than the control after spreading naturally for 24 h. Chemical determination revealed a better infusion behavior of tea polyphenols and amino acids in green tea manufactured by DIC method both at high and low temperature. The increase in tea polyphenols content in liquor for the first brew from twisted and needle tea was about 35% and that from flat tea was about 15% in DIC method over the traditional processing. These results suggest that DIC process can be applied in green tea processing for both a traditional product and a new kind of tea capable of making with cold water. PMID:24426047

  1. Influence of mold growth on the pressure drop in aerated solid state fermentors.

    PubMed

    Auria, R; Morales, M; Villegas, E; Revah, S

    1993-05-01

    The measurement of pressure drop(DeltaP) across an aerated fermentation bed is proposed as alternative on-line sensor for the qualitative and, in some cases, quantitative, macroscopic changes in a static solid state fermentor. An increase in the DeltaP is correlated with the evolution of the different phases of Aspergillus niger growth: germination, vegetative growth, limitation, and sporulation, we observed in the microscope. For the case where the support is not modified during the fermentation and the water content remains constant, i.e., a synthetic resin (Amberlite IRA-900), the gas phase permeability of the bed is directly related to the biomass content. For example, the permeability of the bed is reduced to 5% of the initial value when biomass attains 21 mg dry biomass/g dry support. Biomass was appropriately predicted from the DeltaP measurements in an independent test. Experiments with different initial sucrose solution concentrations showed that biomass could not be produced beyond a certain level (21.5 mg dry biomass/g dry support) which suggests steric limitations. For the case of wheat bran and cane bagasse, the increase in DeltaP was related qualitatively to the evolution in the growth and the morphology of the mold.

  2. Measurement of heat transfer and pressure drop in rectangular channels with turbulence promoters

    NASA Technical Reports Server (NTRS)

    Han, J. C.; Park, J. S.; Ibrahim, M. Y.

    1986-01-01

    Periodic rib turbulators were used in advanced turbine cooling designs to enhance the internal heat transfer. The objective of the present project was to investigate the combined effects of the rib angle of attack and the channel aspect ratio on the local heat transfer and pressure drop in rectangular channels with two opposite ribbed walls for Reynolds number varied from 10,000 to 60,000. The channel aspect ratio (W/H) was varied from 1 to 2 to 4. The rib angle of attack (alpha) was varied from 90 to 60 to 45 to 30 degree. The highly detailed heat transfer coefficient distribution on both the smooth side and the ribbed side walls from the channel sharp entrance to the downstream region were measured. The results showed that, in the square channel, the heat transfer for the slant ribs (alpha = 30 -45 deg) was about 30% higher that of the transverse ribs (alpha = 90 deg) for a constant pumping power. However, in the rectangular channels (W/H = 2 and 4, ribs on W side), the heat transfer at alpha = 30 -45 deg was only about 5% higher than 90 deg. The average heat transfer and friction correlations were developed to account for rib spacing, rib angle, and channel aspect ratio over the range of roughness Reynolds number.

  3. In Situ Measurement, Characterization, and Modeling of Two-Phase Pressure Drop Incorporating Local Water Saturation in PEMFC Gas Channels

    NASA Astrophysics Data System (ADS)

    See, Evan J.

    Proton Exchange Membrane Fuel Cells (PEMFCs) have been an area of focus as an alternative for internal combustion engines in the transportation sector. Water and thermal management techniques remain as one of the key roadblocks in PEMFC development. The ability to model two-phase flow and pressure drop in PEMFCs is of significant importance to the performance and optimization of PEMFCs. This work provides a perspective on the numerous factors that affect the two-phase flow in the gas channels and presents a comprehensive pressure drop model through an extensive in situ fuel cell investigation. The study focused on low current density and low temperature operation of the cell, as these conditions present the most challenging scenario for water transport in the PEMFC reactant channels. Tests were conducted using two PEMFCs that were representative of the actual full scale commercial automotive geometry. The design of the flow fields allowed visual access to both cathode and anode sides for correlating the visual observations to the two-phase flow patterns and pressure drop. A total of 198 tests were conducted varying gas diffusion layer (GDL), inlet humidity, current density, and stoichiometry; this generated over 1500 average pressure drop measurements to develop and validate two-phase models. A two-phase 1+1 D modeling scheme is proposed that incorporates an elemental approach and control volume analysis to provide a comprehensive methodology and correlation for predicting two-phase pressure drop in PEMFC conditions. Key considerations, such as condensation within the channel, consumption of reactant gases, water transport across the membrane, and thermal gradients within the fuel cell, are reviewed and their relative importance illustrated. The modeling scheme is shown to predict channel pressure drop with a mean error of 10% over the full range of conditions and with a mean error of 5% for the primary conditions of interest. The model provides a unique and

  4. Pressure drops in a distensible model of end-to-side anastomosis in systemic-to-pulmonary shunts.

    PubMed

    Migliavacca, Francesco; Pennati, Giancarlo; Di Martino, Elena; Dubini, Gabriele; Pietrabissa, Riccardo

    2002-06-01

    The modified Blalock-Taussig shunt is a surgical procedure used as a palliation to treat complex congenital heart defects. It consists of an interposing prosthetic tube between the innominate/subclavian artery and the right pulmonary artery. Previous experience indicates that the pressure drop across the shunt is affected by the pulmonary pressure at the distal anastomosis combined with the distensibility of the anastomosis. In this study, a computational fluid-structure interaction approach is presented to investigate the haemodynamic behaviour. Steady-state fluid dynamics and structural analyses were carried out using commercial codes based on the finite element method (FIDAP and ABAQUS) coupled by means of a purposely-developed procedure to transfer boundary conditions. Both prosthetic tube and artery walls were characterised by non-linear material properties. Three different pulmonary pressures (2, 5 and 15 mmHg) and two volume flow rates (0.4 and 0.8 l/min) were investigated. Results indicate that the effects of distensibility at the distal anastomosis on the shunt pressure drop are relevant only when the distal anastomosis on the shunt pressure drop are relevant only when the distal anastomosis is not fully distended, which occurs when the pulmonary pressure is lower than 5 mmHg.

  5. Summary report for ITER Task-T19: MHD pressure drop and heat transfer study for liquid metal systems

    SciTech Connect

    Reed, C.B.; Hua, T.Q.; Natesan, K.; Kirillov, I.R.; Vitkovski, I.V.; Anisimov, A.M.

    1995-03-01

    A key feasibility issue for the ITER Vanadium/Lithium breeding blanket is the question of insulator coatings. Design calculations show that an electrically insulating layer is necessary to maintain an acceptably low MHD pressure drop. To begin experimental investigations of the MHD performance of candidate insulator materials and the technology for putting them in place, a new test section was prepared. Aluminum oxide was chosen as the first candidate insulating material because it may be used in combination with NaK in the ITER vacuum vessel and/or the divertor. Details on the methods used to produce the aluminum oxide layer as well as the microstructures of the coating and the aluminide sublayer are presented and discussed. The overall MHD pressure drop, local MHD pressure gradient, local transverse MHD pressure difference, and surface voltage distributions in both the circumferential and the axial directions are reported and discussed. The positive results obtained here for high-temperature NaK have two beneficial implications for ITER. First, since NaK may be used in the vacuum vessel and/or the divertor, these results support the design approach of using electrically insulating coatings to substantially reduce MHD pressure drop. Secondly, while Al{sub 2}O{sub 3}/SS is not the same coating/base material combination which would be used in the advanced blanket, this work nonetheless shows that it is possible to produce a viable insulating coating which is stable in contact with a high temperature alkali metal coolant.

  6. Experimental investigation of the two-phase flow regimes and pressure drop in horizontal mini-size rectangular test section

    NASA Astrophysics Data System (ADS)

    Elazhary, Amr Mohamed; Soliman, Hassan M.

    2012-10-01

    An experimental study was conducted in order to investigate two-phase flow regimes and fully developed pressure drop in a mini-size, horizontal rectangular channel. The test section was machined in the form of an impacting tee junction in an acrylic block (in order to facilitate visualization) with a rectangular cross-section of 1.87-mm height on 20-mm width on the inlet and outlet sides. Pressure drop measurement and flow regime identification were performed on all three sides of the junction. Air-water mixtures at 200 kPa (abs) and room temperature were used as the test fluids. Four flow regimes were identified visually: bubbly, plug, churn, and annular over the ranges of gas and liquid superficial velocities of 0.04 ≤ JG ≤ 10 m/s and 0.02 ≤ JL ≤ 0.7 m/s, respectively, and a flow regime map was developed. Accuracy of the pressure-measurement technique was validated with single-phase, laminar and turbulent, fully developed data. Two-phase experiments were conducted for eight different inlet conditions and various mass splits at the junction. Comparisons were conducted between the present data and former correlations for the fully developed two-phase pressure drop in rectangular channels with similar sizes. Wide deviations were found among these correlations, and the correlations that agreed best with the present data were identified.

  7. One-Dimensional Reactive Transport Modeling of CO2 Storage Systems - Change in Cap Rock Porosity Triggered by Pressure and Temperature Dependent CO2-Water-Rock Interactions

    NASA Astrophysics Data System (ADS)

    Hemme, C.; van Berk, W.

    2015-12-01

    In carbon capture and storage (CCS) systems supercritical CO2 is injected into a reservoir and dissolves in the reservoir brine. Subsequently, CO2(aq) diffuses into the cap rock to regions of lower total pressure and temperature and triggers CO2-water-rock interactions that are coupled with mass transport and result in precipitation and/or dissolution of minerals along the CO2 migration path. Such hydrogeochemical interactions change porosities and are responsible for the improvement or deterioration of the long term integrity of the system. This study presents a semi-generic hydrogeochemical model based on chemical equilibrium thermodynamics, data from several CO2 storage systems, and plausible assumptions regarding non-available data. One-dimensional reactive transport modeling is performed by using the U.S.G.S. PHREEQC code (3.1.4-8929; phreeqc.dat database) to identify and quantify the loss or gain of total porosity affected by hydrogeochemical reactions driven by diffusive mass transport exposed to pressure and temperature gradients. A fine spatial and temporal discretization, the use of non-reactive tracers, and a broad variety of modeling scenarios enable the calculation of the relevant timescale for simulations of long-term storage of CO2 and the consideration of the pressure dependent mass action law constants along the CO2 migration path. Modeling results show that the relevant timescale for simulations of long-term storage of CO2 is in the range of 106 years, and that pressure/temperature conditions, heterogeneities (veins and fractures) and the mineralogical composition of the cap rock have the strongest influence on the increase in cap rock porosity (maximum increase from initial 5 % to 7.5 %). Critical parameter combinations - total pressure effects are crucial - could put long-term integrity at risks. Nevertheless, a wide range of conditions and parameter combinations for safe CO2 storage is identified by other modeling scenarios.

  8. A study of pressure drop in a Capillary tube-viscometer for a two-phase flow

    SciTech Connect

    Ohene, F.; Livingston, C.; Matthews, C.; Rhone, Y.

    1995-09-01

    The analysis of pipeline transportation of highly concentrated suspensions such as coal-water slurries, can exhibit several flow characteristics depending on the concentration and the physical parameters of the dispersed phase. Experiments were conducted for coal-water slurries flows in a series of horizontal capillary tubes of diameters 0.8, 1.5 and 3.0 mm and 100 mm in length, in order to investigate the effect of concentration, pressure drop, and the transitional Reynolds number from laminar to turbulent flow in a homogeneous slurry. The solid concentration was varied from 15% to 63% in 0.1% xanthum gum solution. Pressure drop and the volume flow measurement were made using HVA-6 Capillary viscometer. The Reynolds numbers obtained were found to be dependent on the slurry concentration and the viscosity of the slurry mixture, but independent of the capillary diameter.

  9. Two Phase Flow Modeling: Summary of Flow Regimes and Pressure Drop Correlations in Reduced and Partial Gravity

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Rame, E.; Kizito, J.; Kassemi, M.

    2006-01-01

    The purpose of this report is to provide a summary of state-of-the-art predictions for two-phase flows relevant to Advanced Life Support. We strive to pick out the most used and accepted models for pressure drop and flow regime predictions. The main focus is to identify gaps in predictive capabilities in partial gravity for Lunar and Martian applications. Following a summary of flow regimes and pressure drop correlations for terrestrial and zero gravity, we analyze the fully developed annular gas-liquid flow in a straight cylindrical tube. This flow is amenable to analytical closed form solutions for the flow field and heat transfer. These solutions, valid for partial gravity as well, may be used as baselines and guides to compare experimental measurements. The flow regimes likely to be encountered in the water recovery equipment currently under consideration for space applications are provided in an appendix.

  10. Experimental study of the effect of drag reducing agent on pressure drop and thermal efficiency of an air cooler

    NASA Astrophysics Data System (ADS)

    Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Saffarian, H.; Shekari, F.

    2016-01-01

    Effect of polymeric drag reduction agents (DRAs) on pressure drop and heat transfer was studied. Aqueous solutions of carboxy methyl cellulose were used inside an air-finned heat exchanger. Despite the previous studies which indicated the importance of drag reduction just in turbulent flow, results of this study in laminar flow indicated that the addition of DRA increases drag reduction, and decreases the overall heat transfer coefficient.

  11. On axial temperature gradients due to large pressure drops in dense fluid chromatography.

    PubMed

    Colgate, Sam O; Berger, Terry A

    2015-03-13

    The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier-Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule-Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms "resistive heating" or "frictional heating" have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of

  12. Workplace field testing of the pressure drop of particulate respirators using welding fumes.

    PubMed

    Cho, Hyun-Woo; Yoon, Chung-Sik

    2012-10-01

    In a previous study, we concluded that respirator testing with a sodium chloride aerosol gave a conservative estimate of filter penetration for welding fume aerosols. A rapid increase in the pressure drop (PD) of some respirators was observed as fumes accumulated on the filters. The present study evaluated particulate respirator PD based on workplace field tests. A field PD tester was designed and validated using the TSI 8130 Automatic Filter Tester, designed in compliance with National Institute for Occupational and Safety and Health regulation 42 CFR part 84. Three models (two replaceable dual-type filters and one replaceable single-type filter) were evaluated against CO(2) gas arc welding on mild steel in confined booths in the workplace. Field tests were performed under four airborne concentrations (27.5, 15.4, 7.9, and 2.1 mg m(-3)). The mass concentration was measured by the gravimetric method, and number concentration was monitored using P-Trak (Model 8525, TSI, USA). Additionally, photos and scanning electron microscopy-energy dispersive X-ray spectroscopy were used to visualize and analyze the composition of welding fumes trapped in the filters. The field PD tester showed no significant difference compared with the TSI tester. There was no significant difference in the initial PD between laboratory and field results. The PD increased as a function of fume load on the respirator filters for all tested models. The increasing PD trend differed by models, and PD increased rapidly at high concentrations because greater amount of fumes accumulated on the filters in a given time. The increase in PD as a function of fume load on the filters showed a similar pattern as fume load varied for a particular model, but different patterns were observed for different models. Images and elemental analyses of fumes trapped on the respirator filters showed that most welding fumes were trapped within the first layer, outer web cover, and second layer, in order, while no fumes

  13. Workplace field testing of the pressure drop of particulate respirators using welding fumes.

    PubMed

    Cho, Hyun-Woo; Yoon, Chung-Sik

    2012-10-01

    In a previous study, we concluded that respirator testing with a sodium chloride aerosol gave a conservative estimate of filter penetration for welding fume aerosols. A rapid increase in the pressure drop (PD) of some respirators was observed as fumes accumulated on the filters. The present study evaluated particulate respirator PD based on workplace field tests. A field PD tester was designed and validated using the TSI 8130 Automatic Filter Tester, designed in compliance with National Institute for Occupational and Safety and Health regulation 42 CFR part 84. Three models (two replaceable dual-type filters and one replaceable single-type filter) were evaluated against CO(2) gas arc welding on mild steel in confined booths in the workplace. Field tests were performed under four airborne concentrations (27.5, 15.4, 7.9, and 2.1 mg m(-3)). The mass concentration was measured by the gravimetric method, and number concentration was monitored using P-Trak (Model 8525, TSI, USA). Additionally, photos and scanning electron microscopy-energy dispersive X-ray spectroscopy were used to visualize and analyze the composition of welding fumes trapped in the filters. The field PD tester showed no significant difference compared with the TSI tester. There was no significant difference in the initial PD between laboratory and field results. The PD increased as a function of fume load on the respirator filters for all tested models. The increasing PD trend differed by models, and PD increased rapidly at high concentrations because greater amount of fumes accumulated on the filters in a given time. The increase in PD as a function of fume load on the filters showed a similar pattern as fume load varied for a particular model, but different patterns were observed for different models. Images and elemental analyses of fumes trapped on the respirator filters showed that most welding fumes were trapped within the first layer, outer web cover, and second layer, in order, while no fumes

  14. Heat transfer and pressure drop measurements in an air/molten salt direct-contact heat exchanger

    SciTech Connect

    Bohn, M.S.

    1988-11-01

    This paper presents a comparison of experimental data with a recently published model of heat exchange in irrigated packed beds. Heat transfer and pressure drop were measured in a 150 mm (ID) column with a 610-mm bed of metal Pall rings. Molten nitrate salt and preheated air were the working fluids with a salt inlet temperature of approximately 440{degree}C and air inlet temperatures of approximately 230{degree}C. A comparison between the experimental data and the heat transfer model is made on the basis of heat transfer from the salt. For the range of air and salt flow rates tested, 0.3 to 1.2 kg/m{sup 2} s air flow and 6 to 18 kg/m{sup 2} s salt flow, the data agree with the model within 22% standard deviation. In addition, a model for the column pressure drop was validated, agreeing with the experimental data within 18% standard deviation over the range of column pressure drop from 40 to 1250 Pa/m. 25 refs., 7 figs., 2 tabs.

  15. Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.

  16. Quadratic formula for determining the drop size in pressure-atomized sprays with and without swirl

    NASA Astrophysics Data System (ADS)

    Lee, T.-W.; An, Keju

    2016-06-01

    We use a theoretical framework based on the integral form of the conservation equations, along with a heuristic model of the viscous dissipation, to find a closed-form solution to the liquid atomization problem. The energy balance for the spray renders to a quadratic formula for the drop size as a function, primarily of the liquid velocity. The Sauter mean diameter found using the quadratic formula shows good agreements and physical trends, when compared with experimental observations. This approach is shown to be applicable toward specifying initial drop size in computational fluid dynamics of spray flows.

  17. Pressure drop increase by biofilm accumulation in spiral wound RO and NF membrane systems: role of substrate concentration, flow velocity, substrate load and flow direction.

    PubMed

    Vrouwenvelder, J S; Hinrichs, C; Van der Meer, W G J; Van Loosdrecht, M C M; Kruithof, J C

    2009-01-01

    In an earlier study, it was shown that biofouling predominantly is a feed spacer channel problem. In this article, pressure drop development and biofilm accumulation in membrane fouling simulators have been studied without permeate production as a function of the process parameters substrate concentration, linear flow velocity, substrate load and flow direction. At the applied substrate concentration range, 100-400 microg l(-1) as acetate carbon, a higher concentration caused a faster and greater pressure drop increase and a greater accumulation of biomass. Within the range of linear flow velocities as applied in practice, a higher linear flow velocity resulted in a higher initial pressure drop in addition to a more rapid and greater pressure drop increase and biomass accumulation. Reduction of the linear flow velocity resulted in an instantaneous reduction of the pressure drop caused by the accumulated biomass, without changing the biofilm concentration. A higher substrate load (product of substrate concentration and flow velocity) was related to biomass accumulation. The effect of the same amount of accumulated biomass on the pressure drop increase was related to the linear flow velocity. A decrease of substrate load caused a gradual decline in time of both biomass concentration and pressure drop increase. It was concluded that the pressure drop increase over spiral wound reverse osmosis (RO) and nanofiltration (NF) membrane systems can be reduced by lowering both substrate load and linear flow velocity. There is a need for RO and NF systems with a low pressure drop increase irrespective of the biomass formation. Current efforts to control biofouling of spiral wound membranes focus in addition to pretreatment on membrane improvement. According to these authors, adaptation of the hydrodynamics, spacers and pressure vessel configuration offer promising alternatives. Additional approaches may be replacing heavily biofouled elements and flow direction reversal.

  18. Shape oscillations of acoustically levitated drops in water: Early research with Bob Apfel on modulated radiation pressure

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.

    2001-05-01

    In 1976, research in collaboration with Bob Apfel demonstrated that low-frequency shape oscillations of hydrocarbon drops levitated in water could be driven using modulated radiation pressure. While that response to modulated ultrasound was subsequently extended to a range of systems, the emphasis here is to recall the initial stages of development in Bob Apfel's laboratory leading to some publications [P. L. Marston and R. E. Apfel, J. Colloid Interface Sci. 68, 280-286 (1979); J. Acoust. Soc. Am. 67, 27-37 (1980)]. The levitation technology used at that time was such that it was helpful to develop a sensitive method for detecting weak oscillations using the interference pattern in laser light scattered by levitated drops. The initial experiments to verify this scattering method used shape oscillations induced by modulated electric fields within the acoustic levitator. Light scattering was subsequently used to detect shape oscillations induced by amplitude modulating a carrier having a high frequency (around 680 kHz) at a resonance of the transducer. Methods were also developed for quantitative measurements of the drop's response and with improved acoustic coupling drop fission was observed. The connection with research currently supported by NASA will also be noted.

  19. Pressure, temperature and density drops along supercritical fluid chromatography columns in different thermal environments. III. Mixtures of carbon dioxide and methanol as the mobile phase.

    PubMed

    Poe, Donald P; Veit, Devon; Ranger, Megan; Kaczmarski, Krzysztof; Tarafder, Abhijit; Guiochon, Georges

    2014-01-01

    The pressure, temperature and density drops along SFC columns eluted with a CO2/methanol mobile phase were measured and compared with theoretical values. For columns packed with 3- and 5-μm particles the pressure and temperature drops were measured using a mobile phase of 95% CO2 and 5% methanol at a flow rate of 5mL/min, at temperatures from 20 to 100°C, and outlet pressures from 80 to 300bar. The density drop was calculated based on the temperature and pressure at the column inlet and outlet. The columns were suspended in a circulating air bath, either bare or covered with foam insulation. The experimental measurements were compared to theoretical results obtained by numerical simulation. For the convective air condition at outlet pressures above 100bar the average difference between the experimental and calculated temperature drops and pressure drops were 0.1°C and 0.7% for the bare 3-μm column, respectively, and were 0.6°C and 4.1% for the insulated column. The observed temperature drops for the insulated columns are consistent with those predicted by the Joule-Thomson coefficients for isenthalpic expansion. The dependence of the temperature and the pressure drops on the Joule-Thomson coefficient and kinematic viscosity are described for carbon dioxide mobile phases containing up to 20% methanol.

  20. Development of Porosity Measurement Method in Shale Gas Reservoir Rock

    NASA Astrophysics Data System (ADS)

    Siswandani, Alita; Nurhandoko, BagusEndar B.

    2016-08-01

    The pore scales have impacts on transport mechanisms in shale gas reservoirs. In this research, digital helium porosity meter is used for porosity measurement by considering real condition. Accordingly it is necessary to obtain a good approximation for gas filled porosity. Shale has the typical effective porosity that is changing as a function of time. Effective porosity values for three different shale rocks are analyzed by this proposed measurement. We develop the new measurement method for characterizing porosity phenomena in shale gas as a time function by measuring porosity in a range of minutes using digital helium porosity meter. The porosity of shale rock measured in this experiment are free gas and adsorbed gas porosoty. The pressure change in time shows that porosity of shale contains at least two type porosities: macro scale porosity (fracture porosity) and fine scale porosity (nano scale porosity). We present the estimation of effective porosity values by considering Boyle-Gay Lussaac approximation and Van der Waals approximation.

  1. Pressure drop and heat transfer rates in forced convection rotating square duct flows at high rotation rates

    NASA Astrophysics Data System (ADS)

    Pallares, J.; Grau, F. X.; Davidson, L.

    2005-07-01

    This paper presents and discusses numerical simulations of forced convection heat transfer in a rotating square duct at high rotation rates. The mean pressure gradient has been kept constant in the simulations that were conducted with a second order finite volume code with a dynamical localized subgrid scale model. The rotation number based on the bulk velocity (Ro=2ΩD/U¯b) was varied from 0.12 to 6.6 and consequently the Reynolds number (Re=U¯bD/ν) ranged from 3900 to 1810 according to the fact that rotation tends to increase the pressure drop in the duct. A model for estimating the velocities and the corresponding friction coefficient has been developed by analytically solving simplified versions of the momentum budgets within the Ekman layers occurring near the opposite two walls of the duct perpendicular to the rotation axis. The model reproduces accurately the velocity profiles of the numerical simulation at high rotation rates and predicts that the boundary layer quantities scale as Ek1/2 (Ek=ν/ΩD2). At Ro >1 the Ekman layers are responsible for most of the pressure drop of the flow while the maximum heat transfer rates are found on the wall where the stratification of the x-momentum is unstable with respect to the Coriolis force. Rotation enhances the differences between the contributions of the local friction coefficients and local Nusselt numbers of the four walls of the duct and considerably increases, in comparison with the non-rotating case, the pressure drop of the flow and the Nusselt number. The overall friction coefficient of the measurements and the simulations existing in the literature, as well as the present numerical predictions, are well correlated with the equation 1.09(Cf/Ek1/2)1.25=Ro in the range Ro ⩾1 for Re ⩽104.

  2. Experimental determination of pressure drop and statistical properties of oil-water intermittent flow through horizontal pipe

    SciTech Connect

    Poesio, Pietro

    2008-09-15

    In this paper, oil-water slug flow is studied experimentally. After presenting the experimental set-up and the post-processing tools, flow maps and pressure drops are shown. The main focus of this piece of work is, however, the determination of the statistical behaviour of the elongated oil drops. The characteristic frequency of the process is determined by three estimators: the mean frequency, the most probable frequency, and the so-called diffusional frequency. All the tools give very similar results indicating a regular behaviour of the flow. The regularity was then further proved by means of both diffusional analysis and by the rescaled range analysis. The fractal dimension of the process was also estimated reinforcing again the conclusion that the flow is made up by highly coherent structures. (author)

  3. Pore pressure propagation in a permeable thin-layer coal seam based on a dual porosity model: A case of risk prediction of water inrush in coalmines

    NASA Astrophysics Data System (ADS)

    Zhu, B.; Gao, F.; Yang, J. W.; Zhou, G. Q.

    2016-08-01

    Thin-layer coal seams, a type of filling coal rock body, are considered aquifer systems made up of dual porosity medium with immediate floor. A numerical simulation for the pore pressure propagation along a thin-layer coal seam was carried out for the case of the Zhaogezhuang coalmine in China. By valuing the permeability (Kf ) of the thin-layer coal seam, pore pressure variation with time was simulated and compared to the analytical solutions of a dual porosity model (DPM). The main conclusions were drawn as follow: (1) Seepage in the thin-layer coal seam was predominant in the whole process, and the distance of seepage was lengthened and the pore pressure decreased with increased Kf , (2) A series of simulated hydraulic graphs demonstrated that the pore pressure characteristics of peak-occurring and time-lag effects agreed with the analytical solutions of DPM; (3) By adjusting the parameters of DPM, two results of analytical solutions and numerical solutions fit well, particularly in the thin-layer coal seam, (4) The power law relationship between the peak-values and lag time of pore pressure were derived statistically under consideration of the Kf parameter in the range of 10-8 to 10-10 m2/pa-s orders, and it was reasonable that the Kf of the thin-layer coal seam was in the range of 10-8 m2/pa-s orders. The results were significantly helpful in decision-making for mining water prevention and prediction in practice.

  4. The effects of viscosity and pressure on the bursting of a drop in a Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    White, Andrew; Ward, Thomas

    2009-11-01

    As one fluid is injected into another fluid of greater viscosity, instabilities occur in the form of fingers which extend radially from the injection point (Saffman & Taylor, Proc. R. Soc. Lon. A, 1958). As the lower-viscosity fluid reaches the free surface it rapidly bursts through the higher- viscosity fluid (times are typically less that 50 ms for our system) and a pressure drop occurs. This pressure drop induces the shrinking of the non-bursting fingers. By varying the air pressure and water-glycerol viscosity we study this process by analyzing sequences of images prior and after the bursting event inside a Hele-Shaw cell with a gap spacing of between 10 and 500 micrometers. It has been shown that in a micro-scale environment the effects of gravity are negligible as fluid flow is dominated by capillary forces, thus such a setup would behave in space just as it does on Earth. Therefore it may then be possible to use hot air injected into a Hele-Shaw cell filled with water to generate steam in a microgravity environment.

  5. Impact of organic nutrient load on biomass accumulation, feed channel pressure drop increase and permeate flux decline in membrane systems.

    PubMed

    Bucs, Sz S; Valladares Linares, R; van Loosdrecht, M C M; Kruithof, J C; Vrouwenvelder, J S

    2014-12-15

    The influence of organic nutrient load on biomass accumulation (biofouling) and pressure drop development in membrane filtration systems was investigated. Nutrient load is the product of nutrient concentration and linear flow velocity. Biofouling - excessive growth of microbial biomass in membrane systems - hampers membrane performance. The influence of biodegradable organic nutrient load on biofouling was investigated at varying (i) crossflow velocity, (ii) nutrient concentration, (iii) shear, and (iv) feed spacer thickness. Experimental studies were performed with membrane fouling simulators (MFSs) containing a reverse osmosis (RO) membrane and a 31 mil thick feed spacer, commonly applied in practice in RO and nanofiltration (NF) spiral-wound membrane modules. Numerical modeling studies were done with identical feed spacer geometry differing in thickness (28, 31 and 34 mil). Additionally, experiments were done applying a forward osmosis (FO) membrane with varying spacer thickness (28, 31 and 34 mil), addressing the permeate flux decline and biofilm development. Assessed were the development of feed channel pressure drop (MFS studies), permeate flux (FO studies) and accumulated biomass amount measured by adenosine triphosphate (ATP) and total organic carbon (TOC). Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer thickness. The impact of the same amount of accumulated biomass on feed channel pressure drop and permeate flux was influenced by membrane process design and operational conditions. Reducing the nutrient load by pretreatment slowed-down the biofilm formation. The impact of accumulated biomass on membrane performance was reduced by applying a lower crossflow velocity and/or a thicker and/or a modified geometry feed spacer. The results indicate that cleanings can be delayed

  6. Impact of biofilm accumulation on transmembrane and feed channel pressure drop: effects of crossflow velocity, feed spacer and biodegradable nutrient.

    PubMed

    Dreszer, C; Flemming, H-C; Zwijnenburg, A; Kruithof, J C; Vrouwenvelder, J S

    2014-03-01

    Biofilm formation causes performance loss in spiral-wound membrane systems. In this study a microfiltration membrane was used in experiments to simulate fouling in spiral-wound reverse osmosis (RO) and nanofiltration (NF) membrane modules without the influence of concentration polarization. The resistance of a microfiltration membrane is much lower than the intrinsic biofilm resistance, enabling the detection of biofilm accumulation in an early stage. The impact of biofilm accumulation on the transmembrane (biofilm) resistance and feed channel pressure drop as a function of the crossflow velocity (0.05 and 0.20 m s(-1)) and feed spacer presence was studied in transparent membrane biofouling monitors operated at a permeate flux of 20 L m(-2) h(-1). As biodegradable nutrient, acetate was dosed to the feed water (1.0 and 0.25 mg L(-1) carbon) to enhance biofilm accumulation in the monitors. The studies showed that biofilm formation caused an increased transmembrane resistance and feed channel pressure drop. The effect was strongest at the highest crossflow velocity (0.2 m s(-1)) and in the presence of a feed spacer. Simulating conditions as currently applied in nanofiltration and reverse osmosis installations (crossflow velocity 0.2 m s(-1) and standard feed spacer) showed that the impact of biofilm formation on performance, in terms of transmembrane and feed channel pressure drop, was strong. This emphasized the importance of hydrodynamics and feed spacer design. Biomass accumulation was related to the nutrient load (nutrient concentration and linear flow velocity). Reducing the nutrient concentration of the feed water enabled the application of higher crossflow velocities. Pretreatment to remove biodegradable nutrient and removal of biomass from the membrane elements played an important part to prevent or restrict biofouling.

  7. Heat transfer, pressure drop, and mass flow rate in pin fin channels with long and short trailing edge ejection holes

    NASA Astrophysics Data System (ADS)

    Lau, S. C.; Han, J. C.; Batten, T.

    1988-06-01

    The turbulent heat transfer and friction characteristics in the pin fin channels with small trailing edge ejection holes found in internally-cooled turbine airfoils have been experimentally investigated. It is found that the overall heat transfer increases when the length of the trailing edge ejection holes is increased and when the trailing edge ejection holes are configured such that much of the cooling air is forced to flow further downstream in the radial flow direction prior to exiting. The increase in the overall heat transfer is shown to be accompanied by an increase in the overall pressure drop.

  8. The 4D evolution of porosity during ongoing pressure-solution processes in NaCl using x-ray microtomography

    NASA Astrophysics Data System (ADS)

    Macente, Alice; Fusseis, Florian; Butler, Ian; Tudisco, Erika; Hall, Stephen; Andò, Edward

    2016-04-01

    Pressure-solution creep is a common deformation mechanism in the upper crust. It represents a mass transfer via dissolution-reprecipitation that critically affects the hydraulic properties of rocks. Successful management of safe radioactive storage sites in rock-salt deposits critically depends on an accurate knowledge of the hydro-mechanical behaviour of salt deposits. Despite numerous lab experiments that have been conducted, many aspects of pressure-solution are still poorly understood. There is little knowledge about the spatio-temporal evolution of porosity and permeability during pressure-solution creep. While rates of pressure-solution creep in silicates and carbonates are slow, which makes laboratory investigations of these materials impractical, compaction experiments have demonstrated that NaCl samples deform sufficiently fast to study pressure-solution creep in a lab environment at room temperature and modest loads. We present results from novel experiments that quantify the 4-dimensional (three spatial dimensions plus time) evolution of pressure-solution processes using in-situ x-ray microtomography. Our experiments are performed in custom made x-ray transparent presses. 5 mm diameter NaCl powder samples with a grain size of 250-300 μm are loaded dry into the press and pre-compacted to produce a starting aggregated material. The sample is then flooded with saturated NaCl solution and loaded uniaxially by means of a pneumatic actuator to a constant uniaxial stress. Different sample mixtures were tested, as well as different uniaxial loads. The resulting deformation of the samples is documented in 3-dimensional microtomographic datasets, acquired at regular time intervals. Image analysis allowed characterization of the microstructural evolution of the NaCl grains and the spatio-temporal distribution of porosity during ongoing mechanical and chemical compaction. The microtomography data have also been analysed with 3D Digital Image Correlation (3D-DIC or

  9. Pressure drop measurements in the transition region for a circular tube with a square-edged entrance

    NASA Astrophysics Data System (ADS)

    Ghajar, Afshin J.; Augustine, Jody R.

    1990-06-01

    Pressure drop measurements were made in a horizontal circular straight tube with a square-edged entrance under isothermal flow conditions. The experiments covered a Reynolds number range from 512 to 14,970. A total of thirty-three sets of experimental data for the twenty pressure tap locations along the 20 ft length of the test section were gathered. For the square-edged entrance the range of Reynolds number for which transition flow exists was determined to be between 2070 to 2840. A correlation for prediction of fully developed skin friction coefficient in this region is recommended. In the entrance region the length required for the friction factor to become fully developed in both the laminar and turbulent regions was found to be inversely proportional to the Reynolds number, with the turbulent data showing a stronger dependency. A correlation for prediction of entrance length in the turbulent region is offered.

  10. Heat transfer and pressure drop of supercritical carbon dioxide flowing in several printed circuit heat exchanger channel patterns

    SciTech Connect

    Carlson, M.; Kruizenga, A.; Anderson, M.; Corradini, M.

    2012-07-01

    Closed-loop Brayton cycles using supercritical carbon dioxide (SCO{sub 2}) show potential for use in high-temperature power generation applications including High Temperature Gas Reactors (HTGR) and Sodium-Cooled Fast Reactors (SFR). Compared to Rankine cycles SCO{sub 2} Brayton cycles offer similar or improved efficiency and the potential for decreased capital costs due to a reduction in equipment size and complexity. Compact printed-circuit heat exchangers (PCHE) are being considered as part of several SCO{sub 2} Brayton designs to further reduce equipment size with increased energy density. Several designs plan to use a gas cooler operating near the pseudo-critical point of carbon dioxide to benefit from large variations in thermophysical properties, but further work is needed to validate correlations for heat transfer and pressure-drop characteristics of SCO{sub 2} flows in candidate PCHE channel designs for a variety of operating conditions. This paper presents work on experimental measurements of the heat transfer and pressure drop behavior of miniature channels using carbon dioxide at supercritical pressure. Results from several plate geometries tested in horizontal cooling-mode flow are presented, including a straight semi-circular channel, zigzag channel with a bend angle of 80 degrees, and a channel with a staggered array of extruded airfoil pillars modeled after a NACA 0020 airfoil with an 8.1 mm chord length facing into the flow. Heat transfer coefficients and bulk temperatures are calculated from measured local wall temperatures and local heat fluxes. The experimental results are compared to several methods for estimating the friction factor and Nusselt number of cooling-mode flows at supercritical pressures in millimeter-scale channels. (authors)

  11. In vitro comparison of Günther Tulip and Celect filters: testing filtering efficiency and pressure drop.

    PubMed

    Nicolas, M; Malvé, M; Peña, E; Martínez, M A; Leask, R

    2015-02-01

    In this study, the trapping ability of the Günther Tulip and Celect inferior vena cava filters was evaluated. Thrombus capture rates of the filters were tested in vitro in horizontal position with thrombus diameters of 3 and 6mm and tube diameter of 19mm. The filters were tested in centered and tilted positions. Sets of 30 clots were injected into the model and the same process was repeated 20 times for each different condition simulated. Pressure drop experienced along the system was also measured and the percentage of clots captured was recorded. The Günther Tulip filter showed superiority in all cases, trapping almost 100% of 6mm clots both in an eccentric and tilted position and trapping 81.7% of the 3mm clots in a centered position and 69.3% in a maximum tilted position. The efficiency of all filters tested decreased as the size of the embolus decreased and as the filter was tilted. The injection of 6 clots raised the pressure drop to 4.1mmHg, which is a reasonable value that does not cause the obstruction of blood flow through the system.

  12. In vitro comparison of Günther Tulip and Celect filters: testing filtering efficiency and pressure drop.

    PubMed

    Nicolas, M; Malvé, M; Peña, E; Martínez, M A; Leask, R

    2015-02-01

    In this study, the trapping ability of the Günther Tulip and Celect inferior vena cava filters was evaluated. Thrombus capture rates of the filters were tested in vitro in horizontal position with thrombus diameters of 3 and 6mm and tube diameter of 19mm. The filters were tested in centered and tilted positions. Sets of 30 clots were injected into the model and the same process was repeated 20 times for each different condition simulated. Pressure drop experienced along the system was also measured and the percentage of clots captured was recorded. The Günther Tulip filter showed superiority in all cases, trapping almost 100% of 6mm clots both in an eccentric and tilted position and trapping 81.7% of the 3mm clots in a centered position and 69.3% in a maximum tilted position. The efficiency of all filters tested decreased as the size of the embolus decreased and as the filter was tilted. The injection of 6 clots raised the pressure drop to 4.1mmHg, which is a reasonable value that does not cause the obstruction of blood flow through the system. PMID:25553669

  13. Evaluation of static pressure drops and PM10 and TSP emissions for modified 1D-3D cyclones

    SciTech Connect

    Holt, G.A.; Baker, R.V.; Hughs, S.E.

    1999-12-01

    Five modifications of a standard 1D3D cyclone were tested and compared against the standard 1D3D design in the areas of particulate emissions and static pressure drop across the cyclone. The modifications to the 1D3D design included a 2D2D inlet, a 2D2D air outlet, a D/3 trash exit, an expansion chamber with a D/3 trash exit, and a tapered air outlet duct. The 1D3D modifications that exhibited a significant improvement in reducing both PM10 and total suspended particulate (TSP) emissions were the designs with the 2D2D inlet and air exhaust combined with either the conical D/3 tail cone or the expansion chamber. In reference to the standard 1D3D cyclone, the average reduction in PM10 emissions was 24 to 29% with a 29 to 35% reduction observed in TSP emissions. The modifications with the tapered air outlets did not show any significant improvements in controlling PM10 emissions. However, the modification with the tapered air outlet/expansion chamber combination exhibited statistical significance in reducing TSP emissions by 18% compared to the 1D3D cyclone. All modifications tested exhibited lower static pressure drops than the standard 1D3D.

  14. Pressure drop and heat transfer characteristics for single-phase developing flow of water in rectangular microchannels

    NASA Astrophysics Data System (ADS)

    Mirmanto; Kenning, D. B. R.; Lewis, J. S.; Karayiannis, T. G.

    2012-11-01

    Experiments were conducted to investigate the pressure drop and heat transfer characteristics of single-phase flow of de-ionized water in single copper microchannels of hydraulic diameters 0.438 mm, 0.561 mm and 0.635 mm. The channel length was 62 mm. The experimental conditions covered a range of mass flux from 500 to 5000 kg/m2 s in the laminar, transitional and low Reynolds number turbulent regimes. Pressure drop was measured for adiabatic flows with fluid inlet temperatures of 30°C, 60°C and 90°C. In the heat transfer tests, the heat flux ranged from 256 kW/m2 to 519 kW/m2. Friction factors and Nusselt numbers determined from the measurements were higher than for fully-developed conditions, but in reasonable agreement with predictions made using published solutions for hydrodynamically and thermally developing flow. When entrance effects, experimental uncertainties, heat losses, inlet and exit losses, thermal boundary conditions and departure from laminar flow were considered, the results indicate that equations developed for flow and heat transfer in conventional size channels are applicable for water flows in microchannels of these sizes.

  15. A simple expression for pressure drops of water and other low molecular liquids in the flow through micro-orifices

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tomiichi; Ushida, Akiomi; Narumi, Takatsune

    2015-12-01

    Flows are generally divided into two types: shear flows and shear-free elongational (extensional) flows. Both are necessary for a thorough understanding of the flow properties of a fluid. Shear flows are easy to achieve in practice, for example, through Poiseuille or Couette flows. Shear-free elongational flows are experimentally hard to achieve, resulting in an incomplete understanding of the flow properties of fluids in micro-devices. Nevertheless, flows through micro-orifices are useful for probing the properties of elongational flows at high elongational rates; although these flows exhibit shear and elongation, the elongation is dominant and the shear is negligible in the central region of the flows. We previously reported an anomalous reduction in pressure drops in the flows of water, a 50/50 mixture of glycerol and water, and silicone oils through micro-orifices. In the present paper, we rearrange the data presented in the previous paper and reveal a simple relationship where the pressure drop is proportional to the velocity through the micro-orifices, independent of the orifice diameter and the viscosity of the liquids tested. We explain our observations by introducing a "fluid element" model, in which fluid elements are formed on entering the orifice. The model is based on the idea that low molecular liquids, including water, generate strong elongational stress, similar to a polymer solution, in the flow through micro-orifices.

  16. Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin

    NASA Astrophysics Data System (ADS)

    Ramana Murthy, K. V.; Ranganayakulu, C.; Ashok Babu, T. P.

    2016-05-01

    This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops.

  17. Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

    PubMed

    Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

    2014-07-01

    Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems. PMID:24994652

  18. Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

    PubMed

    Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

    2014-07-01

    Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems.

  19. Pressure Drop and Heat Transfer Characteristics of The Fluid Flow through an Array of Interrupted, Parallel-Plate Heat Transfer Surfaces

    NASA Astrophysics Data System (ADS)

    Mochizuki, Sadanari; Yagi, Yoshinao

    A scale-up modeling technique was used to examine the effect of the geometrical properties of interrupted surfaces on the heat transfer and pressure drop performance of compact heat exchangers having off-set-strip and slotted fins. The test cores, each consisting of a number of machined copper finns, were tested in a subsonic wind tunnel. The heat transfer and the pressure drop for each test core was measured for various fin lengths (in flow direction) and slot distances. Flow visualization and local turbulence intensity and pressure measurements within each test core were also performed to gain insight into the mechanisms of heat transfer augmentation in compact heat exchangers with interrupted surfaces. The effect of the geometrical properties of the fins as well as the Reynolds number on the heat transfer rate and the pressure drop were determined and those results were interpreted in terms of observed flow structure. Basic heat transfer and pressure drop data are presented in terms of Colburn j-factors and Fanning friction factors plotted versus Reynolds number. An empirical correlation for heat transfer and pressure drop characteristics for off-set-strip fins are presented.

  20. Computational and experimental investigation of the drag reduction and the components of pressure drop in horizontal slug flow using liquids of different viscosities

    SciTech Connect

    Daas, Mutaz; Bleyle, Derek

    2006-03-01

    Computational and experimental investigation in 10-cm ID horizontal pipes have been carried out utilizing carbon dioxide as the gas phase and two types of oil with different viscosities; namely 0.0025Pas and 0.05Pas, as the liquid phase. The influence of oil viscosity on the magnitude of total pressure drop and each of its components as well as the effectiveness of a drag reducing additive (DRA, CDR WS 500M flow improver) in decreasing the pressure loss was investigated in two-phase oil-gas slug flow. The effects of changing oil viscosity on the contribution of frictional and accelerational components to total pressure drop in slug flow were also examined and analyzed. Computations of accelerational and frictional components of pressure drop were performed. The accelerational component of pressure drop was dominant in the 0.0025Pas oil while the frictional component had significant contributions in the 0.05Pas oil. Despite the fact that the magnitude of drag reduction was higher in the 0.05Pas oil, the DRA was more effective in reducing the total pressure drop and its components in the 0.0025Pas oil. (author)

  1. Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation.

    PubMed

    Qureshi, M Umar; Vaughan, Gareth D A; Sainsbury, Christopher; Johnson, Martin; Peskin, Charles S; Olufsen, Mette S; Hill, N A

    2014-10-01

    A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen et al. (Ann Biomed Eng 28:1281-1299, 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of 'large' arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the 'smaller' arteries and veins of radii ≥ 50 μm. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment for circulatory diseases within the lung. PMID:24610385

  2. Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation.

    PubMed

    Qureshi, M Umar; Vaughan, Gareth D A; Sainsbury, Christopher; Johnson, Martin; Peskin, Charles S; Olufsen, Mette S; Hill, N A

    2014-10-01

    A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen et al. (Ann Biomed Eng 28:1281-1299, 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of 'large' arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the 'smaller' arteries and veins of radii ≥ 50 μm. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment for circulatory diseases within the lung.

  3. Pressure Drop Across Woven Screens Under Uniform and Nonuniform Flow Conditions. [flow characteristics of water through Dutch twill and square weave fabrics

    NASA Technical Reports Server (NTRS)

    Ludewig, M.; Omori, S.; Rao, G. L.

    1974-01-01

    Tests were conducted to determine the experimental pressure drop and velocity data for water flowing through woven screens. The types of materials used are dutch twill and square weave fabrics. Pressure drop measures were made at four locations in a rectangular channel. The data are presented as change in pressure compared with the average entry velocity and the numerical relationship is determined by dividing the volumetric flow rate by the screen area open to flow. The equations of continuity and momentum are presented. A computer program listing an extension of a theoretical model and data from that computer program are included.

  4. Short term Heart Rate Variability to predict blood pressure drops due to standing: a pilot study

    PubMed Central

    2015-01-01

    Background Standing from a bed or chair may cause a significant lowering of blood pressure (ΔBP), which may have severe consequences such as, for example, falls in older subjects. The goal of this study was to develop a mathematical model to predict the ΔBP due to standing in healthy subjects, based on their Heart Rate Variability, recorded in the 5 minutes before standing. Methods Heart Rate Variability was extracted from an electrocardiogram, recorded from 10 healthy subjects during the 5 minutes before standing. The blood pressure value was measured before and after rising. A mathematical model aiming to predict ΔBP based on Heart Rate Variability measurements was developed using a robust multi-linear regression and was validated with the leave-one-subject-out cross-validation technique. Results The model predicted correctly the ΔBP in 80% of experiments, with an error below the measurement error of sphygmomanometer digital devices (±4.5 mmHg), a false negative rate of 7.5% and a false positive rate of 10%. The magnitude of the ΔBP was associated with a depressed and less chaotic Heart Rate Variability pattern. Conclusions The present study showes that blood pressure lowering due to standing can be predicted by monitoring the Heart Rate Variability in the 5 minutes before standing. PMID:26391336

  5. Advanced turbine systems program conceptual design and product development: Task 8.1, Low-pressure drop recuperator

    SciTech Connect

    1995-09-01

    Purpose of the ATS program is to develop a new baseline for industrial gas turbine systems for the 21st century. A recuperated gas turbine cycle was selected; the eventual engine that result will utilize Solar`s Primary Surface Recuperator (PSR) technology. Besides higher thermal efficiency, other goals included lower emission, cost of power, and improved RAMD (reliability, availability, maintainability). Performance data have been obtained for the candidate heat transfer surface, and on a scaled rig. Pretest predictions of air-side and gas-side pressure drop were in very good agreement with tests results; predicted effectiveness also agreed well with experiment. A flattened tube test to determine changes of the PSR heat transfer surface profile after exposure is underway.

  6. Unusual properties of high-compliance porosity extracted from measurements of pressure-dependent wave velocities in rocks

    NASA Astrophysics Data System (ADS)

    Zaitsev, Vladimir Y.; Radostin, Andrey V.; Pasternak, Elena; Dyskin, Arcady

    2016-04-01

    Conventionally the interpretation of wave velocities and their variations under load is conducted assuming that closable cracks have simple planar shapes, like the popular model of penny-shape cracks. For such cracks, the proportion between complementary variations in different elastic parameters of rocks (such as S- and P-wave velocities) is strictly pre-determined, in particular, it is independent of the crack aspect ratio and rather weakly dependent on the Poisson's ratio of the intact rock. Real rocks, however, contain multitude of cracks of different geometry. Faces of such cracks can exhibit complex modes of interaction when closed by external load, which may result in very different ratios between normal- and shear compliances of such defects. In order to describe the reduction of different elastic moduli, we propose a model in which the compliances of crack-like defects are explicitly decoupled and are not predetermined, so that the ratio q between total normal- and shear- compliances imparted to the rock mass (as well as individual values of these compliances) can be estimated from experimental data on reduction of different elastic moduli (e.g., pressure dependences of P- and S-wave velocities). Physically, the so-extracted ratio q can be interpreted as intrinsic property of individual crack-like defects similar to each other, or as a characteristic of proportion between concentrations of pure normal cracks with very large q and pure shear cracks with q→0. The latter case can correspond, e.g., to saturated cracks in which weakly-compressible liquid prevents crack closing under normal loading. It can be shown that for conventional dry planar cracks, the compliance ratio is q ˜2. The developed model applied to the data on wave-velocity variations with external pressure indicates that elastic properties of the real crack-like defects in rocks can differ considerably from the usually assumed ones. Comparison with experimental data on variations P- and S

  7. On the Accuracy of CFD-Based Pressure Drop Predictions for Right-Angle Ducts

    NASA Technical Reports Server (NTRS)

    Brankovic, Andreja

    1993-01-01

    The predictive capability of computational fluid dynamics (CFD) codes for turbulent flow through curved ducts is of significant importance to the design and performance analysis of modern rocket engine flowpaths. Code calibration and validation studies for this class of flow are desireable to estimate the performance margin and operating range of components designed using Navier-Stokes methods. Parametric experimental studies such as that of Weske (NACA ARR W-39) provided a wealth of performance data for the design of single- and compound elbow configurations with various cross-sections, curvature and aspect ratios at varying Reynolds numbers. In that work, the majority of data is presented in the form of loss coefficients, characterizing pressure losses due to duct curvature, and including losses due to wall friction. Using measured friction coefficients, losses of equivalent straight lengths of duct are subtracted, resulting in performance curves useful for design computations. These data are currently used in a CFD-based parametric study covering a broad range of operating conditions. Of particular interest for the accuracy of CFD predictions are the effects on pressure loss due to inlet boundary layer thickness (dependent on upstream development length), and the wall treatment for the turbulence equations (conventional wall functions vs. wall integration using a two-layer model). The experimental data are reassessed in the form of an error analysis, and are compared with CFD predictions for 18 computational cases. Grid-independence, grid spacing, and convergence requirements of the cases are discussed. Conclusions regarding the relative importance of the parametric variables will be presented.

  8. Impermeable high-porosity magmas

    NASA Astrophysics Data System (ADS)

    Heap, Michael; Vona, Alessandro; Kolzenburg, Stephan; Ryan, Amy; Russell, Kelly

    2016-04-01

    Magma vesiculation (i.e., porosity increase) is the consequence of decompression-driven volatile release during ascent and/or heating. The ease at which these exsolved volatiles can escape is thought to strongly impact volcanic explosivity. Permeability is usually considered to increase as a function of porosity. High and low porosity are typically associated with high and low permeability, respectively. Here we present permeability experiments on foamed natural rhyolitic melts containing total porosities from 0.12 to 0.65; we compliment these data with measurements on synthetic foamed glasses (prepared by FOAMGLAS®) that contain a total porosity of 0.9. The rhyolitic melts (from Krafla, Iceland: Tg = 690 °C) were kept at atmospheric pressure and 1000 °C for 0.5, 1, 2, and 4 hours, followed by quenching. The four experiments yielded total porosities of 0.12, 0.44, 0.51, and 0.65, respectively. The permeability of these samples was then measured using a steady-state, benchtop permeameter under a confining pressure of 1 MPa. The permeability of the foamed samples containing a porosity of 0.12 and 0.44 were not measurable in our system, meaning their permeabilities are lower than ~10-18 m2. The permeability of the samples containing a porosity of 0.51 and 0.65 were 8.7 × 10-15 and 1.0 × 10-15 m2, respectively. Both types of FOAMGLAS® - containing a porosity of 0.9 - also have permeabilities lower than ~10-18 m2. Our study highlights that highly porous magmas are not necessarily permeable due to the absence of a connected network of pores. These data suggest that (1) the percolation threshold for magma requires further thought and, (2) that the liberation of exsolved volatiles will require the fracturing of bubble walls to connect the network of pores within the magma.

  9. Heat transfer and pressure drop performance of a finned-tube heat exchanger proposed for use in the NASA Lewis Altitude Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Vanfossen, G. J.

    1985-01-01

    A segment of the heat exchanger proposed for use in the NASA Lewis Altitude Wind Tunnel (AWT) facility has been tested under dry and icing conditions. The heat exchanger has the largest pressure drop of any component in the AWT loop. It is therefore critical that its performance be known at all conditions before the final design of the AWT is complete. The heat exchanger segment is tested in the NASA Lewis Icing Research Tunnel (IRT) in order to provide an icing cloud environment similar to what will be encountered in the AWT. Dry heat transfer and pressure drop data are obtained and compared to correlations available in the literature. The effects of icing sprays on heat transfer and pressure drop are also investigated.

  10. Steam-explosion pretreatment of wood: effect of chip size, acid, moisture content and pressure drop

    SciTech Connect

    Brownell, H.H.; Yu, E.K.C.; Saddler, J.N.

    1986-06-01

    Material balances for pentosan, lignin, and hexosan, during steam-explosion pretreatment of aspenwood, showed almost quantitative recovery of cellulose in the water-insoluble fraction. Dilute acid impregnation resulted in more selective hydrolysis of pentosan relative to undesirable pyrolysis, and gave a more accessible substrate for enzymatic hydrolysis. Thermocouple probes, located inside simulated aspenwood chips heated in 240 degrees C-saturated steam, showed rapid heating of air-dry wood, whereas green or impregnated wood heated slowly. Small chips, 3.2 mm in the fiber direction, whether green or air dry gave approximately equal rates of pentosan destruction and solubilization, and similar yields of glucose and of total reducing sugars on enzmatic hydrolysis with Trichoderma harzianum. Partial pyrolysis, destroying one-third of the pentosan of aspenwood at atmospheric pressure by dry steam at 276 degrees C, gave little increase in yield of reducing sugars on enzymatic hydrolysis. Treatment with saturated steam at 240 degrees C gave essentially the same yields of butanediol and ethanol on fermentation with Klebsiella pneumoniae, whether or not 80% of the steam was bled off before explosion and even if the chips remained intact, showing that explosion was unnecessary. 17 references.

  11. Pressure drop in single-phase and two-phase couette-poiseuille flow

    SciTech Connect

    Salhi, A. ); Rey, C.; Rosant, J.M. )

    1992-03-01

    This paper is concerned with axial pressure gradient in single-phase and two-phase flow at low void fraction in a narrow annular space between two concentric cylinders, the inner one rotating. From experimental results, the coupling function (inertial forces/centrifugal forces) is parameterized by Taylor or Rossby numbers for two values of the intercylindrical width (clearance). The results are discussed with regard to different flow regimes and it is shown in particular that transition from the turbulent vorticed regime to the turbulent regime occurs at Ro {approx equal} 1. The proposed correlation agrees in a satisfactory manner to all the regimes studied in our experiments and in those given in the bibliography. In addition, original tests with a two-phase liquid/gas flow at 5 percent G.O.R. (gas oil ratio), for a finely dispersed gas phase are also reported. These results indicate a similar behavior to single-phase flows, justifying the transposition of the same correlation in the framework of the homogeneous model.

  12. PRESSURE DROP OF FILTERING FACEPIECE RESPIRATORS: HOW LOW SHOULD WE GO?

    PubMed Central

    Kim, Jung-Hyun; Roberge, Raymond J.; Powell, Jeffrey B.; Shaffer, Ronald E.; Ylitalo, Caroline M.; Sebastian, John M.

    2015-01-01

    Objectives This study was undertaken to determine the mean peak filter resistance to airflow (Rfilter) encountered by subjects while wearing prototype filtering facepiece respirators (PRs) with low Rfilter during nasal and oral breathing at sedentary and low-moderate work rates. Material and Methods In-line pressure transducer measurements of mean Rfilter across PRs with nominal Rfilter of 29.4 Pa, 58.8 Pa and 88.2 Pa (measured at 85 l/min constant airflow) were obtained during nasal and oral breathing at sedentary and low-moderate work rates for 10 subjects. Results The mean Rfilter for the 29.4 PR was significantly lower than the other 2 PRs (p < 0.000), but there were no significant differences in mean Rfilter between the PRs with 58.8 and 88.2 Pa filter resistance (p > 0.05). The mean Rfilter was greater for oral versus nasal breathing and for exercise compared to sedentary activity (p < 0.001). Conclusions Mean oral and nasal Rfilter for all 3 PRs was at, or below, the minimal threshold level for detection of inspiratory resistance (the 58.8–74.5 Pa/1×s−1), which may account for the previously-reported lack of significant subjective or physiological differences when wearing PRs with these low Rfilter. Lowering filtering facepiece respirator Rfilter below 88.2 Pa (measured at 85 l/min constant airflow) may not result in additional subjective or physiological benefit to the wearer. PMID:26159949

  13. Grain-size characteristics of experimental pyroclasts of 1980 Mount St. Helens cryptodome dacite: effects of pressure drop and temperature

    NASA Astrophysics Data System (ADS)

    Spieler, Oliver; Alidibirov, Mikhail; Dingwell, Donald

    2002-11-01

    Using the fragmentation bomb, we analysed the effects of temperature and pressure drop on the grain-size characteristics of experimentally produced pyroclasts. Experiments performed on vesicular samples of grey dacite of the 1980 Mount St. Helens cryptodome at T=20-900 °C and initial pressure differential up to 18.5 MPa provide clear evidence of the influence of these physical conditions upon fragment size and character. Cylindrical dacite samples (diameter=17 mm, length=50 mm) are placed in the high-pressure-temperature section of the apparatus, heated and saturated by argon gas. The disruption of a diaphragm located between the high- and low-pressure sections of the apparatus initiates the rapid depressurisation of the sample. The main results may be summarised as follows. (1) Increasing temperature from 20 to 900 °C results in a decrease in the fragmentation threshold value from 9 to 3 MPa, and an increase in the median diameter of the experimental pyroclasts. These observations imply a decrease in the dynamic tensile strength of dacite at higher temperatures which in turn influences the characteristic size of fragments. (2) Increasing initial pressure differential yields a decrease of the median diameter. Thus, a higher initial elastic potential energy in the magma generates a higher degree of fragmentation. (3) Fragments of angular shape are observed from experiments at all investigated temperatures (20-900 °C), including thereby temperatures significantly higher than the classical (dilatometrically or calorimetrically determined) glass transition temperature determined for this dacite of 810 °C. Thus, brittle response of the dacite is observed under rapid decompression. (4) Fragment size distributions do not correspond to log-normal distributions and are more closely described by Rosin-Rammler distributions. With a decrease of temperature and increase of the initial pressure differential, fragment size distributions approach a Rosin-Rammler distribution

  14. Define and Quantify the Physics of Air Flow, Pressure Drop and Aerosol Collection in Nuclear Grade HEPA Filters

    SciTech Connect

    Moore, Murray E.

    2015-02-23

    Objective: Develop a set of peer-review and verified analytical methods to adjust HEPA filter performance to different flow rates, temperatures and altitudes. Experimental testing will measure HEPA filter flow rate, pressure drop and efficiency to verify the analytical approach. Nuclear facilities utilize HEPA (High Efficiency Particulate Air) filters to purify air flow for workspace ventilation. However, the ASME AG-1 technical standard (Code on Nuclear Air and Gas Treatment) does not adequately describe air flow measurement units for HEPA filter systems. Specifically, the AG-1 standard does not differentiate between volumetric air flow in ACFM (actual cubic feet per minute)compared to mass flow measured in SCFM (standard cubic feet per minute). More importantly, the AG-1 standard has an overall deficiency for using HEPA filter devices at different air flow rates, temperatures, and altitudes. Technical Approach: The collection efficiency and pressure drops of 18 different HEPA filters will be measured over a range of flow rates, temperatures and altitudes. The experimental results will be compared to analytical scoping calculations. Three manufacturers have allocated six HEPA filters each for this effort. The 18 filters will be tested at two different flow rates, two different temperatures and two different altitudes. The 36 total tests will be conducted at two different facilities: the ATI Test facilities (Baltimore MD) and the Los Alamos National Laboratory (Los Alamos NM). The Radiation Protection RP-SVS group at Los Alamos has an aerosol wind tunnel that was originally designed to evaluate small air samplers. In 2010, modifications were started to convert the wind tunnel for HEPA filter testing. (Extensive changes were necessary for the required aerosol generators, HEPA test fixtures, temperature control devices and measurement capabilities.) To this date, none of these modification activities have been funded through a specific DOE or NNSA program. This is

  15. Heat transfer coefficients and pressure drops for R-134a and an ester lubricant mixture in a smooth tube and a micro-fin tube

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1998-10-01

    This paper reports average heat transfer coefficients and pressure drops during the evaporation and condensation of mixtures of R-134a and a 150 SUS penta erythritol ester branched-acid lubricant. The smooth tube and micro-fin tube tested in this study had outer diameters of 9.52 mm (3/8 in.). The micro-fin tube had 60 fins, a fin height of 0.2 mm (0.008 in), and a spiral angle of 18{degree}. The objective of this study is to evaluate the effectiveness of the micro-fin tube with R-134a and to determine the effect of circulating lubricant. The experimental results show that the micro-fin tube has distinct performance advantages over the smooth tube. For example, the average heat transfer coefficients during evaporation and condensation in the micro-fin tube were 50--200% higher than those for the smooth tube, while the average pressure drops were on average only 10--50% higher. The experimental results indicate that the presence of a lubricant degrades the average heat transfer coefficients during both evaporation and condensation at high lubricant concentrations. Pressure drops during evaporation increased with the addition of a lubricant in both tubes. For condensation, pressure drops were unaffected by the addition of a lubricant.

  16. An empirical investigation on thermal characteristics and pressure drop of Ag-oil nanofluid in concentric annular tube

    NASA Astrophysics Data System (ADS)

    Abbasian Arani, A. A.; Aberoumand, H.; Aberoumand, S.; Jafari Moghaddam, A.; Dastanian, M.

    2016-08-01

    In this work an experimental study on Silver-oil nanofluid was carried out in order to present the laminar convective heat transfer coefficient and friction factor in a concentric annulus with constant heat flux boundary condition. Silver-oil nanofluid prepared by Electrical Explosion of Wire technique with no nanoparticles agglomeration during nanofluid preparation process and experiments. The average sizes of particles were 20 nm. Nanofluids with various particle Volume fractions of 0.011, 0.044 and 0.171 vol% were employed. The nanofluid flowing between the tubes is heated by an electrical heating coil wrapped around it. The effects of different parameters such as flow Reynolds number, tube diameter ratio and nanofluid particle concentration on heat transfer coefficient are studied. Results show that, heat transfer coefficient increased by using nanofluid instead of pure oil. Maximum enhancement of heat transfer coefficient occurs in 0.171 vol%. In addition the results showed that, there are slight increases in pressure drop of nanofluid by increasing the nanoparticle concentration of nanofluid in compared to pure oil.

  17. Turbulent heat transfer and pressure drop characteristics of dilute water based Al2O3-Cu hybrid nanofluids.

    PubMed

    Suresh, S; Venkitaraj, K P; Hameed, M Shahul; Sarangan, J

    2014-03-01

    A study on fully developed turbulent convective heat transfer and pressure drop characteristics of Al2O3-Cu/water hybrid nanofluid flowing through a uniformly heated circular tube is presented in this paper. For this, Al2O3-Cu nanocomposite powder was synthesized in a thermo chemical route using hydrogen reduction technique and dispersed the hybrid nano powder in deionised water to form a stable hybrid nanofluid of 0.1% volume concentration. The prepared powder was characterized by X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) to confirm the chemical composition, determine the particle size and study the surface morphology. Stability of the nanofluid was ensured by pH and zeta potential measurements. The average heat transfer enhancement for Al2O3-Cu/water hybrid nanofluid is 8.02% when compared to pure water. The experimental results also showed that 0.1% Al2O3-Cu/water hybrid nanofluids have slightly higher friction factor compared to 0.1% Al2O3/water nanofluid. The empirical correlations proposed for Nusselt number and friction factor were well agreed with the experimental data.

  18. Experimental investigation of heat transfer and pressure drop of turbulent flow inside tube with inserted helical coils

    NASA Astrophysics Data System (ADS)

    Sharafeldeen, M. A.; Berbish, N. S.; Moawed, M. A.; Ali, R. K.

    2016-08-01

    The heat transfer and pressure drop were experimentally investigated in a coiled wire inserted tube in turbulent flow regime in the range of Reynolds number of 14,400 ≤ Re ≤ 42,900. The present work aims to extend the experimental data available on wire coil inserts to cover wire diameter ratio of 0.044 ≤ e/d ≤ 0.133 and coil pitch ratio of 1 ≤ p/d ≤ 5. Uniform heat flux was applied to the external surface of the tube and air was selected as fluid. The effects of Reynolds number and wire diameter and coil pitch ratios on the Nusselt number and friction factor were studied. The enhancement efficiency and performance criteria ranges are of (46.9-82.6 %) and (100.1-128 %) within the investigated range of the different parameters, respectively. Correlations are obtained for the average Nusselt number and friction factor utilizing the present measurements within the investigated range of geometrical parameters and Re. The maximum deviation between correlated and experimental values for Nusselt number and friction factor are ±5 and ±6 %, respectively.

  19. Foot Drop

    MedlinePlus

    ... Awards Enhancing Diversity Find People About NINDS NINDS Foot Drop Information Page Table of Contents (click to ... research is being done? Clinical Trials What is Foot Drop? Foot drop describes the inability to raise ...

  20. Experimental study of single-phase pressure drop and heat transfer in a micro-fin tube

    SciTech Connect

    Li, Xiao-Wei; Meng, Ji-An; Li, Zhi-Xin

    2007-11-15

    The single-phase pressure drop and heat transfer in a micro-fin tube were measured using oil and water as the working fluids. The Prandtl number varied from 3.2 to 220 and the Reynolds number ranged from 2500 to 90,000. The results show that there is a critical Reynolds number, Re{sub cr}, for heat transfer enhancement. For Re

  1. Instant controlled pressure drop technology and ultrasound assisted extraction for sequential extraction of essential oil and antioxidants.

    PubMed

    Allaf, Tamara; Tomao, Valérie; Ruiz, Karine; Chemat, Farid

    2013-01-01

    The instant controlled pressure drop (DIC) technology enabled both the extraction of essential oil and the expansion of the matrix itself which improved solvent extraction. The sequential use of DIC and Ultrasound Assisted Extraction (UAE) triggered complementary actions materialized by supplementary effects. We visualized these combination impacts by comparing them to standard techniques: Hydrodistillation (HD) and Solvent Extraction (SE). First, the extraction of orange peel Essential Oils (EO) was achieved by HD during 4h and DIC process (after optimization) during 2 min; EO yields was 1.97 mg/g dry material (dm) with HD compared to 16.57 mg/g d m with DIC. Second, the solid residue was recovered to extract antioxidant compounds (naringin and hesperidin) by SE and UAE. Scanning electron microscope showed that after HD the recovered solid shriveled as opposite to DIC treatment which expanded the product structure. HPLC analyses showed that the best kinetics and yields of naringin and hesperidin extraction was when DIC and UAE are combined. Indeed, after 1h of extraction, DIC treated orange peels with UAE were 0.825 ± 1.6 × 10(-2)g/g of dry material (dm) for hesperidin and 6.45 × 10(-2) ± 2.3 × 10(-4)g/g d m for naringin compared to 0.64 ± 2.7 × 10(-2)g/g of dry material (dm) and 5.7 × 10(-2) ± 1.6 × 10(-3)g/g d m, respectively with SE. By combining DIC to UAE, it was possible to enhance kinetics and yields of antioxidant extraction.

  2. Characterisation of heat transfer and pressure drop in condensation processes within mini-channel tubes with last generation of refrigerant fluids

    NASA Astrophysics Data System (ADS)

    Lopez Belchi, D. Alejandro

    Heat exchanger developments are driven by energetic efficiency increase and emissionreduction. To reach the standards new system are required based on mini-channels. Mini-channels can be described as tubes with one or more ports extruded in aluminiumwith hydraulic diameter are in the range of 0.2 to 3 mm. Its use in refrigeration systemsfor some years ago is a reality thanks to the human ability to made micro-scale systems.Some heat exchanger enterprises have some models developed specially for their use inautomotive sector, cooling sector, and industrial refrigeration without having a deepknowledge of how these reduced geometries affect the most important parameters suchas pressure drop and the heat transfer coefficient. To respond to this objective, an exhaustive literature review of the last two decades hasbeen performed to determinate the state of the research. Between all the publications,several models have been selected to check the predicting capacities of them becausemost of them were developed for single port mini-channel tubes. Experimentalmeasurements of heat transfer coefficient and frictional pressure drop were recorded inan experimental installation built on purpose at the Technical University of Cartagena.Multiple variables are recorded in this installation in order to calculate local heattransfer coefficient in two-phase condensing flow within mini-channels. Both pressure drop and heat transfer coefficient experimental measurements arecompared to the previously mentioned models. Most of them capture the trend correctlybut others fail predicting experimental data. These differences can be explained by theexperimental parameters considered during the models development. In some cases themodels found in the literature were developed specific conditions, consequently theirpredicting capacities are restricted. As main contributions, this thesis provides new modelling tools for mini-channelscondensing pressure drop and heat transfer coefficient

  3. The effect of passive mixing on pressure drop and oxygen mass fraction using opposing channel flow field design in a Proton Exchange Membrane Fuel Cell

    NASA Astrophysics Data System (ADS)

    Singh, Anant Bir

    This study investigates a flow field with opposing channel design. Previous studies on flow field designs have been focused on improving fuel utilization which often leads to increased pressure drop. This increased pressure drop is typical because standard designs employ either a single flow channel to clear blockages or dead end condition to force the flow through the gas diffusion layer. The disadvantage with these designs is the increased resistance to the flow which requires higher pressure, which becomes a parasitic loss that lowers the system efficiency. For this study the focus was to reduce the pressure drop by providing a less resistive path to the flow. To achieve a less resistive path, the inlet channel was split into two opposing channels. These channels are then recombined only to be split again for the next leg. Therefore, the split channel design should reduce the pressure drop which reduces the parasitic load and ultimately contributes to higher system efficiency. In addition the recombining of the streams at each leg should induce mixing. Having opposing channels should also increase cross flow under the lands to reduce mass transfer loses. The cathode side of the fuel cell is especially sensitive to the mass transport losses since air (oxygen mixed with nitrogen) is used for supplying oxygen unlike the anode side which uses pure hydrogen. To test the hypothesis of having benefits from an opposing channel design, both an experimental and analytical approach was taken. For the experiment, a serpentine flow field and opposing channel flow field plates were compared over several flow rates with compressed air. To test the hypothesis of increased mass transfer, the two flow fields were modeled using a CFD software package, COMSOL. It was found that the opposing channel configuration for high flow rate with multiple entry and exit conditions exhibited significant improvement over the single serpentine channel. Pressure drop was ⅓ less than the

  4. A comparison of the heat transfer and pressure drop performance of R-134a-lubricant mixtures in different diameter smooth tubes and micro-fin tubes

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1998-10-01

    The average heat transfer coefficients and pressure drops during evaporation and condensation are reported for mixtures of R-134a and an ester lubricant in tubes of 12.7 mm (1/2 in.) outer diameter. The objective of this paper is to evaluate the performance of the R-134a-lubricant mixtures in these tubes and determine the performance benefits of the micro-fin tube. The performance benefits of the tubes with 12.7 mm (1/2 in.) outer diameter are compared to those of smaller tubes with 9.52 mm (3/8 in.) outer diameter. The lubricant used was a 169 SUS penta erythritol ester mixed-acid lubricant. The lubricant concentration was varied from 0--5.1% in the mixture. The average heat transfer coefficients in the 12.7 mm (1/2 in.) micro-fin tube were 50--150% higher than those for the 12.7 mm (1/2 in.) smooth tube, while pressure drops in the micro-fin tube were 5% to 50% higher than in the smooth tube. The addition of lubricant degraded the average heat transfer coefficients in all cases except during evaporation at low lubricant concentrations. Pressure drops were always increased with the addition of lubricant. The experimental results also indicate that tube diameter has some effect on the performance benefits of the micro-fin tube over that of the smooth tube.

  5. A critical review of forced convection heat transfer and pressure drop of Al2O3, TiO2 and CuO nanofluids

    NASA Astrophysics Data System (ADS)

    Khurana, Deepak; Choudhary, Rajesh; Subudhi, Sudhakar

    2016-04-01

    Nanofluid is the colloidal suspension of nanosized solid particles like metals or metal oxides in some conventional fluids like water and ethylene glycol. Due to its unique characteristics of enhanced heat transfer compared to conventional fluid, it has attracted the attention of research community. The forced convection heat transfer of nanofluid is investigated by numerous researchers. This paper critically reviews the papers published on experimental studies of forced convection heat transfer and pressure drop of Al2O3, TiO2 and CuO based nanofluids dispersed in water, ethylene glycol and water-ethylene glycol mixture. Most of the researchers have shown a little rise in pressure drop with the use of nanofluids in plain tube. Literature has reported that the pumping power is appreciably high, only at very high particle concentration i.e. more than 5 %. As nanofluids are able to enhance the heat transfer at low particle concentrations so most of the researchers have used less than 3 % volume concentration in their studies. Almost no disagreement is observed on pressure drop results of different researchers. But there is not a common agreement in magnitude and mechanism of heat transfer enhancement. Few studies have shown an anomalous enhancement in heat transfer even at low particle concentration. On the contrary, some researchers have shown little heat transfer enhancement at the same particle concentration. A large variation (2-3 times) in Nusselt number was observed for few studies under similar conditions.

  6. Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles. [for combustion studies

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.

  7. Porosity reduction in Monterey Formation, California

    SciTech Connect

    Compton, J.S.

    1987-05-01

    Porosity and grain density were determined for different lithologies from throughout a 1.2-km thick section of the Monterey and Sisquoc formations in the Santa Maria basin area, California. Porosity reduction by physical and chemical compaction in the predominantly siliceous sediment is controlled largely by the bulk sediment composition and silica phase transformations. Physical compaction of sediment grains from increasing overburden pressure is responsible for most of the gradual porosity reduction with increasing burial depth in opal-A siliceous ooze and diatomite. The porous, incompressible diatom frustule maintains a high porosity relative to clayey and calcareous sediment. Therefore, a positive correlation exists between porosity and biogenic silica (diatom) content of the sediment. During the opal-A to opal-CT silica phase transformation, solution of the porous diatom frustule and precipitation of cryptocrystalline opal-CT results in a porosity reduction that roughly correlates with the biogenic silica content of the sediment. Local porosity reduction occurs in pore-filling dolomite and chert nodules. Dry bulk density as well as porosity reduction tend to increase with sediment depth. Dolomite and organic matter have the most significant influence on the bulk density because of their respective high and low density. The maximum burial depth of the uplifted and eroded section is estimated by overlapping the porosity-depth relation of average deep-sea siliceous ooze.

  8. Flow pattern, pressure drop and void fraction of two-phase gas-liquid flow in an inclined narrow annular channel

    SciTech Connect

    Wongwises, Somchai; Pipathattakul, Manop

    2006-03-01

    Two-phase flow pattern, pressure drop and void fraction in horizontal and inclined upward air-water two-phase flow in a mini-gap annular channel are experimentally studied. A concentric annular test section at the length of 880mm with an outer diameter of 12.5mm and inner diameter of 8mm is used in the experiments. The flow phenomena, which are plug flow, slug flow, annular flow, annular/slug flow, bubbly/plug flow, bubbly/slug-plug flow, churn flow, dispersed bubbly flow and slug/bubbly flow, are observed and recorded by high-speed camera. A slug flow pattern is found only in the horizontal channel while slug/bubbly flow patterns are observed only in inclined channels. When the inclination angle is increased, the onset of transition from the plug flow region to the slug flow region (for the horizontal channel) and from the plug flow region to slug/bubbly flow region (for inclined channels) shift to a lower value of superficial air velocity. Small shifts are found for the transition line between the dispersed bubbly flow and the bubbly/plug flow, the bubbly/plug flow and the bubbly/slug-plug flow, and the bubbly/plug flow and the plug flow. The rest of the transition lines shift to a higher value of superficial air velocity. Considering the effect of flow pattern on the pressure drop in the horizontal tube at low liquid velocity, the occurrence of slug flow stops the rise of pressure drop for a short while, before rising again after the air velocity has increased. However, the pressure does not rise abruptly in the tubes with {theta}=30{sup o} and 60{sup o} when the slug/bubbly flow occurs. At low gas and liquid velocity, the pressure drop increases, when the inclination angles changes from horizontal to 30{sup o} and 60{sup o}. Void fraction increases with increasing gas velocity and decreases with increasing liquid velocity. After increasing the inclination angle from horizontal to {theta}=30{sup o} and 60{sup o}, the void fraction appears to be similar, with a

  9. Formation of shrinkage porosity during solidification of steel: Numerical simulation and experimental validation

    NASA Astrophysics Data System (ADS)

    Riedler, M.; Michelic, S.; Bernhard, C.

    2016-07-01

    The phase transformations in solidification of steel are accompanied by shrinkage and sudden changes in the solubility of alloying elements, resulting in negative side effects as micro- and macrosegregation and the formation of gas and shrinkage porosities. This paper deals with the numerical and experimental simulation of the formation of shrinkage porosity during the solidification of steel. First the physical basics for the mechanism of shrinkage pore formation will be discussed. The main reason for this type of porosity is the restraint of fluid flow in the mushy zone which leads to a pressure drop. The pressure decreases from the dendrite tip to the root. When the pressure falls below a critical value, a pore can form. The second part of the paper deals with different approaches for the prediction of the formation of shrinkage porosity. The most common one according to these models is the usage of a simple criterion function, like the Niyama criterion. For the computation of the porosity criterion the thermal gradient, cooling rate and solidification rate must be known, easily to determine from numerical simulation. More complex simulation tools like ProCAST include higher sophisticated models, which allow further calculations of the shrinkage cavity. Finally, the different approaches will be applied to a benchmark laboratory experiment. The presented results deal with an ingot casting experiment under variation of taper. The dominant influence of mould taper on the formation of shrinkage porosities can both be demonstrated by the lab experiment as well as numerical simulations. These results serve for the optimization of all ingot layouts for lab castings at the Chair of Ferrous Metallurgy.

  10. Effect of magnetic field on the forced convection heat transfer and pressure drop of a magnetic nanofluid in a miniature heat sink

    NASA Astrophysics Data System (ADS)

    Ashjaee, Mehdi; Goharkhah, Mohammad; Khadem, Leila Azizi; Ahmadi, Reza

    2014-12-01

    The effect of an external magnetic field on the forced convection heat transfer and pressure drop of water based Fe3O4 nanofluid (ferrofluid) in a miniature heat sink is studied experimentally. The heat sink with the dimensions of 40 mm (L) × 40 mm (W) × 10 mm (H) consists of an array of five circular channels with diameter and length of 4 and 40 mm, respectively. It is heated from the bottom surface with a constant heat flux while the other surfaces are insulated. The heat sink is also influenced by an external magnetic field generated by an electromagnet. The local convective coefficients are measured at various flow rates (200 < Re < 900), magnetic field intensities (B < 1,400 G), and particle volume fractions (φ = 0.5, 1, 2 and 3 %). Results show that using ferrofluid results in a maximum of 14 % improvement in heat transfer compared to the pure water, in the absence of magnetic field. This value grows up to 38 % when a magnetic field with the strength of 1,200 G is applied to the ferrofluid. On the other hand, it is observed that the significant heat transfer enhancement due to the magnetic field is always accompanied by a pressure drop penalty. The optimum operating condition is obtained based on the maximum heat transfer enhancement per pressure loss.

  11. Experimental analysis of the pressure drop and heat transfer through metal foams used as volumetric receivers under concentrated solar radiation

    SciTech Connect

    Albanakis, C.; Missirlis, D.; Yakinthos, K.; Goulas, A.; Michailidis, N.; Omar, H.; Tsipas, D.; Granier, B.

    2009-01-15

    The main objective of this work was to evaluate the behavior of porous materials, when treated as volumetric receivers under concentrated solar radiation. For this reason various porous metallic and ceramic materials have been tested as potential receivers for concentrated solar radiation. The experimental investigation showed that their efficiency was depending on both materials parameters and flow conditions. In this work, a variety of foam materials such as Ni and Ni alloy, inconel, copper, aluminum and SiC with different open cell porosity were tested as potential media to be used as volumetric receivers and heat exchangers. However, since the results were similar, for space economy, only the results of two of them, nickel and inconel were presented in detail and compared with each other. (author)

  12. Study on measurement of the coal powder concentration in pneumatic pipes of a boiler with relationship between air velocity and pressure drop

    SciTech Connect

    Pan, W.; Shen, F.; Lin, W.; Chen, L.; Zhang, D.; Wang, Q.; Ke, J.; Quan, W.

    1999-07-01

    According to the theoretical relationship between air velocity and pressure drop in different solid-air mass flow in vertical pipes with the condition of upward air-solid flowing, the experimental research on measuring the coal powder concentration is directed against the pneumatic pipes of a boiler's combustion system in the energy industry. Through analyzing the experimental results, a mathematical model for measuring the coal powder concentration in pneumatic pipes is obtained. Then, the error analysis is done, and the method of on-line measurement and its function are provided.

  13. Porosity variations in and around normal fault zones: implications for fault seal and geomechanics

    NASA Astrophysics Data System (ADS)

    Healy, David; Neilson, Joyce; Farrell, Natalie; Timms, Nick; Wilson, Moyra

    2015-04-01

    clear lithofacies control on the Vp-porosity and the Vs-Vp relationships for faulted limestones. Using porosity patterns quantified in naturally deformed rocks we have modelled their effect on the mechanical stability of fluid-saturated fault zones in the subsurface. Poroelasticity theory predicts that variations in fluid pressure could influence fault stability. Anisotropic patterns of porosity in and around fault zones can - depending on their orientation and intensity - lead to an increase in fault stability in response to a rise in fluid pressure, and a decrease in fault stability for a drop in fluid pressure. These predictions are the exact opposite of the accepted role of effective stress in fault stability. Our work has provided new data on the spatial and statistical variation of porosity in fault zones. Traditionally considered as an isotropic and scalar value, porosity and pore networks are better considered as anisotropic and as scale-dependent statistical distributions. The geological processes controlling the evolution of porosity are complex. Quantifying patterns of porosity variation is an essential first step in a wider quest to better understand deformation processes in and around normal fault zones. Understanding porosity patterns will help us to make more useful predictive tools for all agencies involved in the study and management of fluids in the subsurface.

  14. On models of double porosity poroelastic media

    NASA Astrophysics Data System (ADS)

    Boutin, Claude; Royer, Pascale

    2015-12-01

    This paper focuses on the modelling of fluid-filled poroelastic double porosity media under quasi-static and dynamic regimes. The double porosity model is derived from a two-scale homogenization procedure, by considering a medium locally characterized by blocks of poroelastic Biot microporous matrix and a surrounding system of fluid-filled macropores or fractures. The derived double porosity description is a two-pressure field poroelastic model with memory and viscoelastic effects. These effects result from the `time-dependent' interaction between the pressure fields in the two pore networks. It is shown that this homogenized double porosity behaviour arises when the characteristic time of consolidation in the microporous domain is of the same order of magnitude as the macroscopic characteristic time of transient regime. Conversely, single porosity behaviours occur when both timescales are clearly distinct. Moreover, it is established that the phenomenological approaches that postulate the coexistence of two pressure fields in `instantaneous' interaction only describe media with two pore networks separated by an interface flow barrier. Hence, they fail at predicting and reproducing the behaviour of usual double porosity media. Finally, the results are illustrated for the case of stratified media.

  15. Noninvasive estimation of transmitral pressure drop across the normal mitral valve in humans: importance of convective and inertial forces during left ventricular filling

    NASA Technical Reports Server (NTRS)

    Firstenberg, M. S.; Vandervoort, P. M.; Greenberg, N. L.; Smedira, N. G.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.

    2000-01-01

    OBJECTIVES: We hypothesized that color M-mode (CMM) images could be used to solve the Euler equation, yielding regional pressure gradients along the scanline, which could then be integrated to yield the unsteady Bernoulli equation and estimate noninvasively both the convective and inertial components of the transmitral pressure difference. BACKGROUND: Pulsed and continuous wave Doppler velocity measurements are routinely used clinically to assess severity of stenotic and regurgitant valves. However, only the convective component of the pressure gradient is measured, thereby neglecting the contribution of inertial forces, which may be significant, particularly for nonstenotic valves. Color M-mode provides a spatiotemporal representation of flow across the mitral valve. METHODS: In eight patients undergoing coronary artery bypass grafting, high-fidelity left atrial and ventricular pressure measurements were obtained synchronously with transmitral CMM digital recordings. The instantaneous diastolic transmitral pressure difference was computed from the M-mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation and was compared to the catheter measurements. RESULTS: From 56 beats in 16 hemodynamic stages, inclusion of the inertial term ([deltapI]max = 1.78+/-1.30 mm Hg) in the noninvasive pressure difference calculation significantly increased the temporal correlation with catheter-based measurement (r = 0.35+/-0.24 vs. 0.81+/-0.15, p< 0.0001). It also allowed an accurate approximation of the peak pressure difference ([deltapc+I]max = 0.95 [delta(p)cathh]max + 0.24, r = 0.96, p<0.001, error = 0.08+/-0.54 mm Hg). CONCLUSIONS: Inertial forces are significant components of the maximal pressure drop across the normal mitral valve. These can be accurately estimated noninvasively using CMM recordings of transmitral flow, which should improve the understanding of diastolic filling and function of the heart.

  16. The T-By Tray: A plug flow, low pressure drop, high-efficiency contacting device for cross-flow columns

    SciTech Connect

    Bravo, J.L. ); Parker, B.M.; Parker, T.J. )

    1991-01-01

    This report describes the development of the T-By tray, a new tray design for cross-flow contacting of gas and liquid in absorption, stripping and distillation applications, which is designed to promote liquid plug flow and eliminate tray stagnant side zones. Two different designs, T-By I and T-By II, were tested for capacity, mass transfer efficiency and pressure drop. The T-By I design is the most successful, and offers the following advantages over sieve and valve trays: lower pressure drop per tray at equivalent open areas and weir heights, better turndown capability and a wider operating range, equivalent or higher efficiency for mass transfer, and greater vapor handling capacity. Mass transfer data from larger scale devices are needed to confirm some advantages seen in smaller columns, but the T-By tray should perform at least as well and probably better than conventional sieve and valve trays in larger diameter columns. 7 refs., 22 figs., 8 tabs.

  17. Drop dynamics

    NASA Technical Reports Server (NTRS)

    Elleman, D. D.

    1981-01-01

    The drop dynamics module is a Spacelab-compatible acoustic positioning and control system for conducting drop dynamics experiments in space. It consists basically of a chamber, a drop injector system, an acoustic positioning system, and a data collection system. The principal means of collecting data is by a cinegraphic camera. The drop is positioned in the center of the chamber by forces created by standing acoustic waves generated in the nearly cubical chamber (about 12 cm on a side). The drop can be spun or oscillated up to fission by varying the phse and amplitude of the acoustic waves. The system is designed to perform its experiments unattended, except for start-up and shutdown events and other unique events that require the attention of the Spacelab payload specialist.

  18. High Pressure, Transport Properties of Fluids: Theory and Data from Levitated Fluid-Drops at Combustion-Relevant Temperatures

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Ohaska, K.

    2001-01-01

    The objective of this investigation is to derive a set of consistent mixing rules for calculating diffusivities and thermal diffusion factors over a thermodynamic regime encompassing the subcritical and supercritical ranges. These should serve for modeling purposes, and therefore for accurate simulations of high pressure phenomena such as fluid disintegration, turbulent flows and sprays. A particular consequence of this work will be the determination of effective Lewis numbers for supercritical conditions, thus enabling the examination of the relative importance of heat and mass transfer at supercritical pressures.

  19. Porosity and Permeability of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Corrigan, Catherine M.; Dahl, Jason; Long, Michael

    1996-01-01

    We have investigated the porosity of a large number of chondritic interplanetary dust particles and meteorites by three techniques: standard liquid/gas flow techniques, a new, non-invasive ultrasonic technique, and image processing of backscattered images . The latter technique is obviously best suited to sub-kg sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, non-destructive pressure release technique. We find that chondritic IDP's have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. These values suggest IDP bulk densities of 1.1 to 3.3 g/cc. Type 1-3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1-3 chondrites have the same approximate range as exhibited by matrix, indicating that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as matrix. These results reveal that the porosity of primitive materials at scales ranging from nanogram to kilogram are similar, implying similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, or chondrite type.

  20. Analysis of Heat Transfer and Pressure Drop for a Gas Flowing Through a set of Multiple Parallel Flat Plates at High Temperatures

    NASA Technical Reports Server (NTRS)

    Einstein, Thomas H.

    1961-01-01

    Equations were derived representing heat transfer and pressure drop for a gas flowing in the passages of a heater composed of a series of parallel flat plates. The plates generated heat which was transferred to the flowing gas by convection. The relatively high temperature level of this system necessitated the consideration of heat transfer between the plates by radiation. The equations were solved on an IBM 704 computer, and results were obtained for hydrogen as the working fluid for a series of cases with a gas inlet temperature of 200 R, an exit temperature of 5000 0 R, and exit Mach numbers ranging from 0.2 to O.8. The length of the heater composed of the plates ranged from 2 to 4 feet, and the spacing between the plates was varied from 0.003 to 0.01 foot. Most of the results were for a five- plate heater, but results are also given for nine plates to show the effect of increasing the number of plates. The heat generation was assumed to be identical for each plate but was varied along the length of the plates. The axial variation of power used to obtain the results presented is the so-called "2/3-cosine variation." The boundaries surrounding the set of plates, and parallel to it, were assumed adiabatic, so that all the power generated in the plates went into heating the gas. The results are presented in plots of maximum plate and maximum adiabatic wall temperatures as functions of parameters proportional to f(L/D), for the case of both laminar and turbulent flow. Here f is the Fanning friction factor and (L/D) is the length to equivalent diameter ratio of the passages in the heater. The pressure drop through the heater is presented as a function of these same parameters, the exit Mach number, and the pressure at the exit of the heater.

  1. Residual Porosity as An Explanation for Ductile-Brittle Behaviour During Dome Extrusion: Experimental Constraints

    NASA Astrophysics Data System (ADS)

    Kennedy, L.; Russell, J. K.; Nelles, E.

    2009-12-01

    Decompression of rising magmas causes gas exsolution and a concomitant increase in magma porosity. Slow ascent commonly results in cooling and crystallization of the residual melt on the same time scale. Thus, slow ascending magmas commonly produce domes that are typically at or below their Tg, or have undergone degassing-induced crystallization. These magmas can be either highly porous or nonporous. For example, high residual porosity indicates that the system had low permeability and was quenched before the porosity could be removed. This quenching of primary porosity could be induced by cooling of the melt to below Tg, or by crystallization of the melt to produce a solid framework. Here, we demonstrate experimentally the effects of porosity on the strength and failure behaviour of dacite dome rocks. Our triaxial rock deformation experiments were run at confining pressures (Pc) of 0, 25, 50, and 75MPa, at room temperature and strain rates of ~1 x 10-4 s-1. Our starting material has both low (6-8%) and high (17-24%) porosities, a uniform bulk composition (65 wt% SiO2) and is either highly crystalline or has a glassy matrix. The low porosity dacite experiments show a progressive increase in peak strength (100-700 MPa) with increasing Pc and all cores show brittle behavior, characterized by a rapid stress drop. Run products contain macroscopic fractures with deformation extremely localized around the shear fractures. Experimentally deformed dacites show extreme grain size reduction and the production of gouge. We ran two sets of experiments on low porosity rocks: one for which the gear train was stopped just at failure and one for which, after failure and creation of the fracture surface, frictional sliding continued along the fracture. Grain size from the experimentally generated gouge was measured using a grain size laser particle analyzer. The vast majority of ultra-fine grained particles (< 20 μm) are produced at fracture (ie large stress drops), and further

  2. Porosity, single-phase permeability, and capillary pressure data from preliminary laboratory experiments on selected samples from Marker Bed 139 at the Waste Isolation Pilot Plant. Volume 1 of 3: Main report, appendix A

    SciTech Connect

    Howarth, S.M.; Christian-Frear, T.

    1997-08-01

    Three groups of core samples from Marker Bed 139 of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) were analyzed to provide data to support the development of numerical models used to predict the long-term hydrologic and structural response of the WIPP repository. These laboratory experiments, part of the FY93 Experimental Scoping Activities of the Salado Two-Phase Flow Laboratory Program, were designed to (1) generate WIPP-specific porosity and single-phase permeability data, (2) provide information needed to design and implement planned tests to measure two-phase flow properties, including threshold pressure, capillary pressure, and relative permeability, and (3) evaluate the suitability of using analog correlations for the Salado Formation to assess the long-term performance of the WIPP. This report contains a description of the boreholes core samples, the core preparation techniques used, sample sizes, testing procedures, test conditions, and results of porosity and single-phase permeability tests performed at three laboratories: TerraTek, Inc. (Salt Lake City, UT), RE/SPEC, Inc. (Rapid City, SD), and Core Laboratories-Special Core Analysis Laboratory (Carrollton, TX) for Rock Physics Associates. In addition, this report contains the only WIPP-specific two-phase-flow capillary-pressure data for twelve core samples. The WIPP-specific data generated in this laboratory study and in WIPP field-test programs and information from suitable analogs will form the basis for specification of single- and two-phase flow parameters for anhydrite markers beds for WIPP performance assessment calculations.

  3. Air atmospheric pressure plasma jet pretreatment for drop-wise loading of dexamethasone on hydroxyapatite scaffold for increase of osteoblast attachment.

    PubMed

    Lee, Jung-Hwan; Kwon, Jae-Sung; Kim, Yong Hee; Choi, Eun Ha; Kim, Kwang-Mahn; Kim, Kyoung-Nam

    2014-10-01

    Periodontal disease affects alveolar bone resorption around the involved teeth. To gain bone height, bone graft materials have been widely used with drug carriers. Application of an atmospheric pressure plasma jet (APPJ) treatment is widely studied due to its ability to change surface characteristics without topographical change. The aim of this study is to identify whether the air APPJ (AAPPJ) treatment before drop-wise loading performance could change loaded amount of dexamethasone, and induce increase of cell attachment and proliferation. The results suggested that AAPPJ treatment decreased the contact angle down to about 13 degrees, which increased gradually but significantly lowered at least 4 days compared to no-treated group. After AAPPJ treatment, hydrocarbon was removed with change of zeta potential into positive charge. However, the AAPPJ treatment did not change the quantity or releasing profile of dexamethasone (p > 0.05). Confocal analysis combined with DNA proliferation analysis showed increase of osteoblast attachment and proliferation. Hence, AAPPJ could be a useful pretreatment method before drop-wise loading on HA scaffold with dexamethasone for increase of osteoblast attachment. PMID:25942843

  4. Analysis of pressure drop characteristics and methods for calculating gas and gas-solid flow in horizontal pipes for dilute coal conveying system

    SciTech Connect

    Weiguo Pan; Zuohe Chi; Yongjing Liao

    1997-07-01

    This article reported pressure drop characteristics and methods for calculating friction factors {lambda} 0 and {lambda}{sub {mu}} for gas and gas-solids flows, respectively, in straight horizontal pipes are summarized advantages seed. The and disadvantages of calculating friction factor {lambda}{sub {mu}} through dimensional analysis in comparison with model simulation are analyzed. It is pointed out that model simulation is more suitable to engineering use than dimensional analysis. According to experimental results of dilute gas-coal powder flow in straight horizontal pipes of the coal pulverization system in a power plant; an empirical formula and a theoretical formula for calculating friction factor {lambda}{sub {mu}} in straight horizontal pipes transporting dilute coal powder are obtained.

  5. A Numerical Procedure for Flow Distribution and Pressure Drops for U and Z Type Configurations Plate Heat Exchangers with Variable Coefficients

    NASA Astrophysics Data System (ADS)

    López, R.; Lecuona, A.; Ventas, R.; Vereda, C.

    2012-11-01

    In Plate Heat Exchangers it is important to determine the flow distribution and pressure drops, because they affect directly the performance of a heat exchanger [1]. This work proposes an incompressible, one-dimensional, steady state, discrete model allowing for variable overall momentum coefficients to determine these magnitudes. The model consists on a modified version of the Bajura and Jones [2] model for dividing and combining flow manifolds. The numerical procedure is based on the finite differences approximation approach proposed by Datta and Majumdar [3]. A linear overall momentum coefficient distribution is used in the dividing manifold, but the model is not limited to linear distributions. Comparisons are made with experimental, numerical and analytical data, yielding good results.

  6. Drag with external and pressure drop with internal flows: a new and unifying look at losses in the flow field based on the second law of thermodynamics

    NASA Astrophysics Data System (ADS)

    Herwig, Heinz; Schmandt, Bastian

    2013-10-01

    Internal and external flows are characterized by friction factors and drag coefficients, respectively. Their definitions are based on pressure drop and drag force and thus are very different in character. From a thermodynamics point of view in both cases dissipation occurs which can uniformly be related to the entropy generation in the flow field. Therefore we suggest to account for losses in the flow field by friction factors and drag coefficients that are based on the overall entropy generation due to the dissipation in the internal and external flow fields. This second law analysis (SLA) has been applied to internal flows in many studies already. Examples of this flow category are given together with new cases of external flows, also treated by the general SLA-approach.

  7. Investigations of Pressure Drops during Piston Flow Pneumatic Conveying of Ice Cubes and Applying It to High Density Conveying of Cold Energy

    NASA Astrophysics Data System (ADS)

    Ohira, Akiyoshi; Yanadori, Michio; Tsubota, Yuji

    To overcome the defect of conventional chilled water systems, we propose pneumatic conveying of ice cubes. We conducted experiments to investigate the pressure drops during pneumatic conveying of ice cubes in a prototype conveyance pipe, and obtained the following results : (1)The mean velocity of the ice cubes is proportional to the mean velocity of the conveying air flow regardless of balls in the pipe or the volume fraction of the ice cubes. (2) Difference in the velocity of the air flow cause variations in the density of ice cubes. If we convey ice cubes with balls, it is possible to convey a higher density. (3) The volume fraction of this method is about 10 times that of the previous experimental results. (4)The pump power of this proposed conveyance system is reduced to about 0.71 to 0.59 times that of the conventional chilled water systems.

  8. Heat transfer and pressure drop in a compact pin-fin heat exchanger with pin orientation at 18 deg to the flow direction

    NASA Technical Reports Server (NTRS)

    Olson, D. A.

    1991-01-01

    The heat transfer and pressure drop characteristics of a novel, compact heat exchanger in helium gas were measured at 3.5 MPa and Reynolds numbers of 450 to 12,000. The pin-fin specimen consisted of pins, 0.51 mm high and spaced 2.03 mm on centers, spanning a channel through which the helium flows; the angle of the row of pins to the flow direction was 18 deg. The specimen was radiatively heated on the top side at heat fluxes up to 74 W/sq cm and insulated on the back side. Correlations were developed for the friction factor and Nusselt number. The Nusselt number compares favorably to those of past studies of staggered pin-fins, when the measured temperatures are extrapolated to the temperature of the wall-fluid interface.

  9. Void Fraction and Pressure Drop in Two-Phase Equilibrium Flows in a Vertical 2 × 3 Rod Bundle Channel ─ Assessment of Correlations against the Present Subchannel Data

    NASA Astrophysics Data System (ADS)

    Sadatomi, Michio; Kano, Keiko; Kawahara, Akimaro; Mori, Naoki

    In order to increase void fraction and pressure drop data in a multi-subchannel system like an actual fuel rod bundle, air-water experiments have been conducted using a vertical 2 × 3 rod bundle channel made up of two central and four side subchannels as the test channel. Void fraction and pressure drop in each subchannel were measured and the frictional pressure drop was determined mainly for slug and churn flows. The results show that both the void fraction and the frictional pressure drop are higher in the central subchannel than the side one. In order to analyze the data, the data on gas and liquid flow rates in each subchannel under the same flow condition have been used. In the analysis, the calculations by various correlations reported in literatures have been compared with the present data for validation. The recommended correlations respectively for the void fraction and the frictional pressure drop have been clarified. Results of such experiments and analyses are presented and discussed in this paper.

  10. Parametric study on heat transfer enhancement and pressure drop of an internal blade tip-wall with pin-fin arrays

    NASA Astrophysics Data System (ADS)

    Xie, Gongnan; Sundén, Bengt; Wang, Lieke; Utriainen, Esa

    2011-01-01

    One way to cool gas turbine tips is to design serpentine passages with 180° turns inside the blades to fully utilize the coolant potential. It is therefore a desire to improve the cooling of the blade tips to ensure a long durability and safe operation. In the present work, a two-pass channel with a 180° turn and various arrays of pin-fins mounted internally on the tip-cap is considered. The effects of pin-fin height, diameter and pitches on the heat transfer enhancement and pressure drop are investigated numerically. The nominal ratio of height to diameter (H/D) of the pin-fins is 2, and the ratio of tip clearance to pin-fin height is about 10. The inlet Reynolds numbers based on hydraulic diameter are ranging from 100,000 to 600,000. Details of the three dimensional fluid flow and heat transfer over the pin-finned tips are presented. The overall performances of various tips are compared. It is found that due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of the pin-finned tips is up to a factor of 2.1 higher than that of the smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 30%. Results show that the magnitude of the heat transfer enhancement depends upon pin-fin configuration and arrangement. It is suggested that pin-fins are suitable to enhance the blade tip heat transfer and thus to improve the tip cooling.

  11. Overall heat transfer coefficient and pressure drop in a typical tubular exchanger employing alumina nano-fluid as the tube side hot fluid

    NASA Astrophysics Data System (ADS)

    Kabeel, A. E.; Abdelgaied, Mohamed

    2016-08-01

    Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.

  12. Microparticles with hierarchical porosity

    SciTech Connect

    Petsev, Dimiter N; Atanassov, Plamen; Pylypenko, Svitlana; Carroll, Nick; Olson, Tim

    2012-12-18

    The present disclosure provides oxide microparticles with engineered hierarchical porosity and methods of manufacturing the same. Also described are structures that are formed by templating, impregnating, and/or precipitating the oxide microparticles and method for forming the same. Suitable applications include catalysts, electrocatalysts, electrocatalysts support materials, capacitors, drug delivery systems, sensors and chromatography.

  13. Liquid drops impacting superamphiphobic coatings.

    PubMed

    Deng, Xu; Schellenberger, Frank; Papadopoulos, Periklis; Vollmer, Doris; Butt, Hans-Jürgen

    2013-06-25

    The dynamics of liquid drops impacting superamphiphobic coatings is studied by high-speed video microscopy. Superamphiphobic coatings repel water and oils. The coating consists of a fractal-like hydrophobized silica network. Mixtures of ethanol-water and glycerin-water are chosen to investigate the influence of interfacial tension and viscosity on spreading and retraction dynamics. Drop spreading is dominated by inertia. At low impact velocity, the drops completely rebound. However, the contact time increases with impact velocity, whereas the restitution coefficient decreases. We suggest that the drop temporarily impales the superamphiphobic coating, although the drop completely rebounds. From an estimate of the pressure, it can be concluded that impalement is dominated by depinning rather than sagging. With increasing velocity, the drops partially pin, and an increasing amount of liquid remains on the coating. A time-resolved study of the retraction dynamics reveals two well-separated phases: a fast inertia-dominated phase followed by a slow decrease of the contact diameter of the drop. The crossover occurs when the diameter of the retracting drop matches the diameter of the drop before impact. We suggest that the depth of impalement increases with impact velocity, where impalement is confined to the initial impact zone of the drop. If the drop partially pins on the coating, the depth of impalement exceeds a depth, preventing the whole drop from being removed during the retraction phase.

  14. In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube. Part 2: Condensation

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1994-12-31

    Average in-tube heat transfer coefficients and pressure drops during condensation are reported for condensation of refrigerant R-134a/lubricant mixtures in a smooth tube and a micro-fin tube of 9.52-mm (3/8-in.) outer diameter. The lubricants tested were 169-SUS and 369-SUS penta erythritol ester mixed acids. Lubricant concentrations ranged from 0% to 5%. The average saturation temperature in the test tube was approximately 40 C (104 F). The mass flux of the refrigerant-lubricant mixtures was varied from 85 kg/m{sup 2}{center_dot}s (62,700 lb/ft{sup 2}{center_dot}h) to 375 kg/m{sup 2}{center_dot}s (276,640 lb/ft{sup 2}{center_dot}h). Heat transfer coefficients during condensation decreased with the addition of lubricants in all cases. Condensation pressure drops increased with the addition of the 169-SUS ester lubricant in both the smooth tube and the micro-fin tube. The addition of the 369-SUS lubricant did not affect pressure drops in the smooth tube, but it decreased the pressure drops in the micro-fin tube. Pure R-134a heat transfer coefficients in the micro-fin tube were 100% to 200% higher than those in the smooth tube, with the higher values occurring at the lower mass fluxes. Pressure drops in the micro-fin tube were 20% to 50% higher than those in the smooth tube. Design equations are presented that aid in predicting the heat transfer coefficients and pressure drops of R-134a/lubricant mixtures in the smooth and micro-fin tubes.

  15. Recommendations on selecting the closing relations for calculating friction pressure drop in the loops of nuclear power stations equipped with VVER reactors

    NASA Astrophysics Data System (ADS)

    Alipchenkov, V. M.; Belikov, V. V.; Davydov, A. V.; Emel'yanov, D. A.; Mosunova, N. A.

    2013-05-01

    Closing relations describing friction pressure drop during the motion of two-phase flows that are widely applied in thermal-hydraulic codes and in calculations of the parameters characterizing the flow of water coolant in the loops of reactor installations used at nuclear power stations and in other thermal power systems are reviewed. A new formula developed by the authors of this paper is proposed. The above-mentioned relations are implemented in the HYDRA-IBRAE thermal-hydraulic computation code developed at the Nuclear Safety Institute of the Russian Academy of Sciences. A series of verification calculations is carried out for a wide range of pressures, flowrates, and heat fluxes typical for transient and emergency operating conditions of nuclear power stations equipped with VVER reactors. Advantages and shortcomings of different closing relations are revealed, and recommendations for using them in carrying out thermal-hydraulic calculations of coolant flow in the loops of VVER-based nuclear power stations are given.

  16. Experimental investigation of heat transfer and pressure drop characteristics of water and glycol-water mixture in multi-port serpentine microchannel slab heat exchangers

    NASA Astrophysics Data System (ADS)

    Khan, Md Mesbah-ul Ghani

    Microchannels have several advantages over traditional large tubes. Heat transfer using microchannels recently have attracted significant research and industrial design interests. Open literatures leave with question on the applicability of classical macroscale theory in microchannels. Better understanding of heat transfer in various microchannel geometries and building experimental database are continuously urged. The purpose of this study is to contribute the findings and data to this emerging area through carefully designed and well controlled experimental works. The commercially important glycol-water mixture heat transfer fluid and multiport slab serpentine heat exchangers are encountered in heating and cooling areas, e.g. in automotive, aircraft, and HVAC industries. For a given heat duty, the large diameter tubes experience turbulent flow whereas the narrow channels face laminar flow and often developing flow. Study of low Reynolds number developing glycol-water mixture laminar flow in serpentine microchannel heat exchanger with parallel multi-port slab is not available in the open literature. Current research therefore experimentally investigates glycol-water mixture and water in simultaneously developing laminar flows. Three multiport microchannel heat exchangers; straight and serpentine slabs, are used for each fluid. Friction factors of glycol-water mixture and water flows in straight slabs are higher than conventional fully developed laminar flow. If a comprehensive pressure balance is introduced, the results are well compared with conventional Poiseuille theory. Similar results are found in serpentine slab. The pressure drop for the straight core is the highest, manifolds are the intermediate, and serpentine is the least; which are beneficial for heat exchangers. The heat transfer results in serpentine slab for glycol-water mixture and water are higher and could not be compared with conventional fully developed and developing flow correlations. New

  17. Porosity trends of the Lower Cretaceous J Sandstone, Denver Basin, Colorado

    USGS Publications Warehouse

    Schmoker, J.W.; Higley, D.K.

    1991-01-01

    The petrographic factors that most affect J sandstone porosity variability at a given level of thermal maturity are carbonate cementation and clay content. Carbonate cement, where present, reduces porosity. If previously more widespread, carbonate cement could also introduce porosity heterogeneity by temporarily preserving the pore network relative to uncemented intervals. Abundant detrital and authigenic clay reduces porosity by occupying pores. Low clay content indirectly reduces porosity because the inhibiting effects of clay upon quartz cementation and pressure solution are largely absent. -from Authors

  18. Controlled porosity in electrodes

    SciTech Connect

    Chiang, Yet-Ming; Bae, Chang-Jun; Halloran, John William; Fu, Qiang; Tomsia, Antoni P.; Erdonmez, Can K.

    2015-06-23

    Porous electrodes in which the porosity has a low tortuosity are generally provided. In some embodiments, the porous electrodes can be designed to be filled with electrolyte and used in batteries, and can include low tortuosity in the primary direction of ion transport during charge and discharge of the battery. In some embodiments, the electrodes can have a high volume fraction of electrode active material (i.e., low porosity). The attributes outlined above can allow the electrodes to be fabricated with a higher energy density, higher capacity per unit area of electrode (mAh/cm.sup.2), and greater thickness than comparable electrodes while still providing high utilization of the active material in the battery during use. Accordingly, the electrodes can be used to produce batteries with high energy densities, high power, or both compared to batteries using electrodes of conventional design with relatively highly tortuous pores.

  19. Acute sensitivity of landslide rates to initial soil porosity

    USGS Publications Warehouse

    Iverson, R.M.; Reid, M.E.; Iverson, N.R.; LaHusen, R.G.; Logan, M.; Mann, J.E.; Brien, D.L.

    2000-01-01

    Some landslides move imperceptibly downslope, whereas others accelerate catastrophically. Experimental landslides triggered by rising pore water pressure moved at sharply contrasting rates due to small differences in initial porosity. Wet sandy soil with porosity of about 0.5 contracted during slope failure, partially liquefied, and accelerated within 1 second to speeds over I meter per second. The same soil with porosity of about 0.4 dilated during failure and supped episodically at rates averaging 0.002 meter per second. Repeated slip episodes were induced by gradually rising pore water pressure and were arrested by pore dilation and attendant pore pressure decline.

  20. Acute sensitivity of landslide rates to initial soil porosity.

    PubMed

    Iverson, R M; Reid, M E; Iverson, N R; LaHusen, R G; Logan, M; Mann, J E; Brien, D L

    2000-10-20

    Some landslides move imperceptibly downslope, whereas others accelerate catastrophically. Experimental landslides triggered by rising pore water pressure moved at sharply contrasting rates due to small differences in initial porosity. Wet sandy soil with porosity of about 0.5 contracted during slope failure, partially liquefied, and accelerated within 1 second to speeds over 1 meter per second. The same soil with porosity of about 0.4 dilated during failure and slipped episodically at rates averaging 0.002 meter per second. Repeated slip episodes were induced by gradually rising pore water pressure and were arrested by pore dilation and attendant pore pressure decline. PMID:11039931

  1. A novel target-type low pressure drop bidirectional optoelectronic air flow sensor for infant artificial ventilation: Measurement principle and static calibration

    NASA Astrophysics Data System (ADS)

    Saccomandi, Paola; Schena, Emiliano; Silvestri, Sergio

    2011-02-01

    An optoelectronic target-type volumetric air flow-rate transducer for bidirectional measurements is presented. The sensor is composed of a T-shaped target and two nominally identical LED-photodiode couples which are operated in differential mode. The sensitive surfaces of the photodiodes are differentially shadowed by the deflection of the target, which in turn depends on the gas flow-rate. The principle of operation is described in mathematical terms and the design parameters have been optimized in order to obtain the highest sensitivity along with minimal pressure drop and reduced dimensions. The sensor is placed in a 20 mm diameter hose and was tested with air flow-rate in the typical temperature range of mechanical ventilation between 20 and 40 °C. The theoretical model was validated through experiments carried out in the volumetric flow range from -7.0 to +7.0 l min-1. The nonlinear behavior allows sensitivities equal to 0.6 V l-1 min for flow rates ranging from -2.0 to +2.0 l min-1, equal to 2.0 V l-1 min for flow rates ranging from -3.0 to -2.0 l min-1 and from +2.0 to +3.0 l min-1, up to 5.7 V l-1 min at higher flow rates ranging from -7.0 to -3.0 l min-1 and from +3.0 to +7.0 l min-1. The linear range extends from 3.0 to 7.0 l min-1 with constant sensitivity equal to 5.7 V l-1 min. The sensor is able to detect a flow-rate equal to 1.0 l min-1 with a sensitivity of about 400 mV l-1 min. The differential nature of the output minimizes the influence of the LEDs' power supply variations and allows to obtain a repeatability in the order of 3% of full scale output. The small pressure drop produced by the sensor placed in-line the fluid stream, of about 2.4 Pa at 7 l min-1, corresponds to a negligible fluid dynamic resistance lower than 0.34 Pa l-1 min.

  2. A novel target-type low pressure drop bidirectional optoelectronic air flow sensor for infant artificial ventilation: Measurement principle and static calibration

    SciTech Connect

    Saccomandi, Paola; Schena, Emiliano; Silvestri, Sergio

    2011-02-15

    An optoelectronic target-type volumetric air flow-rate transducer for bidirectional measurements is presented. The sensor is composed of a T-shaped target and two nominally identical LED-photodiode couples which are operated in differential mode. The sensitive surfaces of the photodiodes are differentially shadowed by the deflection of the target, which in turn depends on the gas flow-rate. The principle of operation is described in mathematical terms and the design parameters have been optimized in order to obtain the highest sensitivity along with minimal pressure drop and reduced dimensions. The sensor is placed in a 20 mm diameter hose and was tested with air flow-rate in the typical temperature range of mechanical ventilation between 20 and 40 deg. C. The theoretical model was validated through experiments carried out in the volumetric flow range from -7.0 to +7.0 l min{sup -1}. The nonlinear behavior allows sensitivities equal to 0.6 V l{sup -1} min for flow rates ranging from -2.0 to +2.0 l min{sup -1}, equal to 2.0 V l{sup -1} min for flow rates ranging from -3.0 to -2.0 l min{sup -1} and from +2.0 to +3.0 l min{sup -1}, up to 5.7 V l{sup -1} min at higher flow rates ranging from -7.0 to -3.0 l min{sup -1} and from +3.0 to +7.0 l min{sup -1}. The linear range extends from 3.0 to 7.0 l min{sup -1} with constant sensitivity equal to 5.7 V l{sup -1} min. The sensor is able to detect a flow-rate equal to 1.0 l min{sup -1} with a sensitivity of about 400 mV l{sup -1} min. The differential nature of the output minimizes the influence of the LEDs' power supply variations and allows to obtain a repeatability in the order of 3% of full scale output. The small pressure drop produced by the sensor placed in-line the fluid stream, of about 2.4 Pa at 7 l min{sup -1}, corresponds to a negligible fluid dynamic resistance lower than 0.34 Pa l{sup -1} min.

  3. Turbulent Kinetic Energy Measurement Using Phase Contrast MRI for Estimating the Post-Stenotic Pressure Drop: In Vitro Validation and Clinical Application

    PubMed Central

    Ha, Hojin; Kim, Guk Bae; Kweon, Jihoon; Huh, Hyung Kyu; Lee, Sang Joon; Koo, Hyun Jung; Kang, Joon-Won; Lim, Tae-Hwan; Kim, Dae-Hee; Kim, Young-Hak

    2016-01-01

    Background Although the measurement of turbulence kinetic energy (TKE) by using magnetic resonance imaging (MRI) has been introduced as an alternative index for quantifying energy loss through the cardiac valve, experimental verification and clinical application of this parameter are still required. Objectives The goal of this study is to verify MRI measurements of TKE by using a phantom stenosis with particle image velocimetry (PIV) as the reference standard. In addition, the feasibility of measuring TKE with MRI is explored. Methods MRI measurements of TKE through a phantom stenosis was performed by using clinical 3T MRI scanner. The MRI measurements were verified experimentally by using PIV as the reference standard. In vivo application of MRI-driven TKE was explored in seven patients with aortic valve disease and one healthy volunteer. Transvalvular gradients measured by MRI and echocardiography were compared. Results MRI and PIV measurements of TKE are consistent for turbulent flow (0.666 < R2 < 0.738) with a mean difference of −11.13 J/m3 (SD = 4.34 J/m3). Results of MRI and PIV measurements differ by 2.76 ± 0.82 cm/s (velocity) and −11.13 ± 4.34 J/m3 (TKE) for turbulent flow (Re > 400). The turbulence pressure drop correlates strongly with total TKE (R2 = 0.986). However, in vivo measurements of TKE are not consistent with the transvalvular pressure gradient estimated by echocardiography. Conclusions These results suggest that TKE measurement via MRI may provide a potential benefit as an energy-loss index to characterize blood flow through the aortic valve. However, further clinical studies are necessary to reach definitive conclusions regarding this technique. PMID:26978529

  4. The precipitation of silica gels along seismogenic faults due to sudden fluid pressure drops: an example from the Zuccale low angle normal fault, Italy

    NASA Astrophysics Data System (ADS)

    Holdsworth, R. E.; Smith, S.; Lloyd, G. E.

    2012-04-01

    Based on experimental and some field-based studies several authors have proposed that silica gel (hydrated amorphous silica) layers are generated by frictional slip along seismogenic faults. The precise mechanism(s) of formation have remained somewhat enigmatic, but most studies invoke a mixture of frictional and chemical processes simultaneous with seismogenic slip. In this presentation we describe a new occurrence of ultrafine grained silica fault rocks that are hosted along a number of detachment faults developed within the Zuccale low angle normal fault on the island of Elba, Italy. Based on the geological and microstructural observations, including very detailed EBSD measurements, we propose an alternative mechanism of formation in which the gels precipitate rapidly from supersaturated pore fluids formed due to sudden drops in fluid pressure along faults during or immediately following episodes of seismogenic slip. This mechanism may have widespread application to other examples of fault-hosted silica gels. Furthermore, given the field appearance of these layers (see figure) and the recognition of ultrafine quartz crystallites in thin section, it is possible that similar examples in other natural fault zones may have been mistakenly identified as pseudotachylytes. The implications for fault weakening will also be discussed.

  5. Liquids with permanent porosity.

    PubMed

    Giri, Nicola; Del Pópolo, Mario G; Melaugh, Gavin; Greenaway, Rebecca L; Rätzke, Klaus; Koschine, Tönjes; Pison, Laure; Gomes, Margarida F Costa; Cooper, Andrew I; James, Stuart L

    2015-11-12

    Porous solids such as zeolites and metal-organic frameworks are useful in molecular separation and in catalysis, but their solid nature can impose limitations. For example, liquid solvents, rather than porous solids, are the most mature technology for post-combustion capture of carbon dioxide because liquid circulation systems are more easily retrofitted to existing plants. Solid porous adsorbents offer major benefits, such as lower energy penalties in adsorption-desorption cycles, but they are difficult to implement in conventional flow processes. Materials that combine the properties of fluidity and permanent porosity could therefore offer technological advantages, but permanent porosity is not associated with conventional liquids. Here we report free-flowing liquids whose bulk properties are determined by their permanent porosity. To achieve this, we designed cage molecules that provide a well-defined pore space and that are highly soluble in solvents whose molecules are too large to enter the pores. The concentration of unoccupied cages can thus be around 500 times greater than in other molecular solutions that contain cavities, resulting in a marked change in bulk properties, such as an eightfold increase in the solubility of methane gas. Our results provide the basis for development of a new class of functional porous materials for chemical processes, and we present a one-step, multigram scale-up route for highly soluble 'scrambled' porous cages prepared from a mixture of commercially available reagents. The unifying design principle for these materials is the avoidance of functional groups that can penetrate into the molecular cage cavities. PMID:26560299

  6. Porosity in polysilsesquioxane xerogels

    SciTech Connect

    LOY,DOUGLAS A.; SCHNEIDER,DUANE A.; BAUGHER,BRIGITTA M.; RAHIMIAN,KAMYAR

    2000-05-09

    Polysilsesquioxanes, [RSiO{sub 1.5}]{sub n} are a class of hybrid organic-inorganic materials in which silicon atoms are linked with up to three siloxane bonds to other monomer units in the polymer and the organic group is a pendent functionality. Polysilsesquioxanes are prepared by the hydrolysis and condensation of organotrialkoxysilanes (Scheme l). Organotrialkoxysilanes RSi(OR{prime}){sub 3}, have been extensively used as coupling agents for composites or surface treatments for materials. Polysilsesquioxanes have become increasingly popular for generating specialty coatings such as low k dielectric materials for microelectronic applications. While there is extensive information on the formation of polysilsesquioxanes, there has not been a survey of the ability of organotrialkoxysilanes to form gels until recently. The formation of polysilsesquioxanes gels has been shown to be very sensitive to the nature of the organic group. Many monomers will only form soluble oligomers or polymers upon hydrolysis and condensation, even when the reaction is conducted solvent-free with neat monomer and aqueous catalyst. Furthermore, there is little information concerning the influence of the organic group, R, on the porosity of the polysilsesquioxanes gels that are formed. In this paper the authors describe the preparation of polysilsesquioxane gels where R = H, methyl, ethyl, cyanoethyl, vinyl, dodecyl, hexadecyl, octadecyl, chloromethyl, and chloromethylphenyl, and the characterization of the porosity of the respective xerogels. Gels were prepared from the hydrolysis and condensation of organotrimethoxysilanes, RSi(OEt){sub 3}, and organotriethoxy-silanes, RSi(OEt){sub 3}.

  7. Causes and remedies for porosity in composite manufacturing

    NASA Astrophysics Data System (ADS)

    Fernlund, G.; Wells, J.; Fahrang, L.; Kay, J.; Poursartip, A.

    2016-07-01

    Porosity is a challenge in virtually all composite processes but in particular in low pressure processes such as out of autoclave processing of prepregs, where the maximum pressure is one atmosphere. This paper discusses the physics behind important transport phenomena that control porosity and how we can use our understanding of the underlying science to develop strategies to achieve low porosity for these materials and processes in an industrial setting. A three step approach is outlined that addresses and discusses: gas evacuation of trapped air, volatiles and off-gassing, and resin infiltration of evacuated void space.

  8. Investigations of levitated helium drops

    NASA Astrophysics Data System (ADS)

    Whitaker, Dwight Lawrence

    1999-11-01

    We report on the development of two systems capable of levitating drops of liquid helium. Helium drops of ˜20 mum have been levitated with the radiation pressure from two counter-propagating Nd:YAG laser beams. Drops are produced with a submerged piezoelectric transducer, and could be held for up to three minutes in our optical trap. Calculations show that Brillouin and Raman scattering of the laser light in the liquid helium produces a negligible rate of evaporation of the drop. Evaporation caused by the enhanced vapor pressure of the curved drop surfaces appears to be a significant effect limiting the drop lifetimes. Helium drops as large as 2 cm in diameter have been suspended in the earth's gravitational field with a magnetic field. A commercial superconducting solenoid provides the necessary field, field-gradient product required to levitate the drops. Drops are cooled to 0.5 K with a helium-3 refrigerator, and can be held in the trap indefinitely. We have found that when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. This effect is a result of the evaporation of liquid from between the two drops, and is found to occur only for normal fluid drops. We can induce shape oscillations in charged, levitated drops with an applied ac electric field. We have measured the resonance frequencies and damping rates for the l = 2 mode of oscillation as function of temperature. We have also developed a theory to describe the small amplitude shape oscillations of a He II drop surrounded by its saturated vapor. In our theory, we have considered two sets of boundary conditions---one where the drop does not evaporate and another in which the liquid and vapor are in thermodynamic equilibrium. We have found that both solutions give a frequency that agrees well with experiment, but that the data for the damping rate agree better with the solution without evaporation.

  9. Porosity in Polysilsesquioxane Xerolgels

    SciTech Connect

    Baugher, B.M.; Loy, D.A.; Rahimian, K.

    1999-08-17

    Polymerization of organotrialkoxysilanes is a convenient method for introducing organic functionality into hybrid organic-inorganic materials. However, not much is known about the effects of the organic substituent on the porosity of the resulting xerogels. In this study, we prepared a series of polysilsesquioxane xerogels from organotrialkoxysilanes, RSi(OR{sup 1}){sub 3}, with different organic groups (R = H, Me, Et dodecyl, hexadecyl, octadecyl, vinyl, chloromethyl, (p-chloromethyl) phenyl, cyanoethyl). Polymerizations of the monomers were carried out under a variety of conditions, varying monomer concentration, type of catalyst, and alkoxide substituent. The effect of the organic substituent on the sol-gel process was often dramatic. In many cases, gels were formed only at very high monomer concentration and/or with only one type of catalyst. All of the gels were processed as xerogels and characterized by scanning electron microscopy and nitrogen sorption porosimetry to evaluate their pore structure.

  10. Fatigue Crack and Porosity Measurement in Composite Materials by Thermographic and Ultrasonic Methods

    NASA Technical Reports Server (NTRS)

    Walker, James L.; Russell, Samuel S.; Suits, Michael W.; Workman, Gary L.

    2003-01-01

    Contents include the following: 1. Purpose. Detect thermo-mechanically induced intra-ply fatigue microcracking and manufactured porosity in unlined composite pressure vessels. 2. Defect descriptions. Porosity, microcracking. 3. Thermography. Overview of technique. Strengths and Weaknesses. Examples of its use for porosity detection. 4. Resonant ultrasound spectroscopy. Overview of technique. Strengths and Weaknesses. Examples of its use for microcracking detection. Conclusions.

  11. Thermoelectric materials having porosity

    SciTech Connect

    Heremans, Joseph P.; Jaworski, Christopher M.; Jovovic, Vladimir; Harris, Fred

    2014-08-05

    A thermoelectric material and a method of making a thermoelectric material are provided. In certain embodiments, the thermoelectric material comprises at least 10 volume percent porosity. In some embodiments, the thermoelectric material has a zT greater than about 1.2 at a temperature of about 375 K. In some embodiments, the thermoelectric material comprises a topological thermoelectric material. In some embodiments, the thermoelectric material comprises a general composition of (Bi.sub.1-xSb.sub.x).sub.u(Te.sub.1-ySe.sub.y).sub.w, wherein 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 1.8.ltoreq.u.ltoreq.2.2, 2.8.ltoreq.w.ltoreq.3.2. In further embodiments, the thermoelectric material includes a compound having at least one group IV element and at least one group VI element. In certain embodiments, the method includes providing a powder comprising a thermoelectric composition, pressing the powder, and sintering the powder to form the thermoelectric material.

  12. Mechanistic Effects of Porosity on Structural Composite Materials

    NASA Astrophysics Data System (ADS)

    Siver, Andrew

    As fiber reinforced composites continue to gain popularity as primary structures in aerospace, automotive, and powersports industries, quality control becomes an extremely important aspect of materials and mechanical engineering. The ability to recognize and control manufacturing induced defects can greatly reduce the likelihood of unexpected catastrophic failure. Porosity is the result of trapped volatiles or air bubbles during the layup process and can significantly compromise the strength of fiber reinforced composites. A comprehensive study was performed on an AS4C-UF3352 TCR carbon fiber-epoxy prepreg system to determine the effect of porosity on flexural, shear, low-velocity impact, and damage residual strength properties. Autoclave cure pressure was controlled to induce varying levels of porosity to construct six laminates with porosity concentrations between 0-40%. Porosity concentrations were measured using several destructive and nondestructive techniques including resin burnoff, sectioning and optical analysis, and X-ray computed tomography (CT) scanning. Ultrasonic transmission, thermography, and CT scanning provided nondestructive imaging to evaluate impact damage. A bilinear relationship accurately characterizes the change in mechanical properties with increasing porosity. Strength properties are relatively unaffected when porosity concentrations are below approximately 2.25% and decrease linearly by up to 40% in high porosity specimens.

  13. In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube. Part 1: Evaporation

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1994-12-31

    In-tube heat transfer coefficients and pressure drops during evaporation are reported for mixtures of refrigerant R-134a and a penta erythritol ester mixed-acid lubricant. The ester lubricant was tested at viscosities of 169 SUS and 369 SUS over a lubricant concentration range of 0% to 5% in both a smooth tube and a micro-fine tube. The average saturation temperature used was 1 C (33.8 F). Measurements were taken for the refrigerant-lubricant mixture over a mass flux range of 85 kg/m{sup 2}{center_dot}s (62,700 lb/ft{sup 2}{center_dot}h) to 375 kg/m{sup 2}{center_dot}s (276,640 lb/ft{sup 2}{center_dot}h) in test tubes with an outer diameter of 9.52 mm (3/8 in.). Heat transfer coefficients during evaporation increased at low concentrations of the 169-SUS ester lubricant and then dropped off at high lubricant concentrations in both the smooth tube and the micro-fin tube. The higher viscosity 369-SUS lubricant decreased the heat transfer coefficients in both tubes over the range of lubricant concentrations tested. Pressure drops during evaporation increased in both the smooth tube and the micro-fin tube with the addition of ester lubricant of either viscosity. The heat transfer coefficients for the micro-fin tube were 100% to 50% higher than those for the smooth tube, with the higher values occurring at low mass fluxes. Pressure drops in the micro-fin tube were 10% to 20% higher than those in the smooth tube.

  14. Convective Mixing in Porosity Waves during Melt Migration

    NASA Astrophysics Data System (ADS)

    Jordan, J.; Hesse, M. A.

    2014-12-01

    Models of trace element partitioning during non-reactive, one-dimensional melt migration predict the decoupling of tracers with different partition coefficients (e.g. La and Sm)(Navon & Stolper 1987, DePaolo 1996 Liang 2008). Such decoupling is often not observed in igneous products at the surface. We propose a numeric melt migration model derived from first principles to aid our understanding of mixing during melt migration in the mantle. We assert that circulation within a porosity wave could provide an explanation for this disparity. Buoyancy drives regions of elevated melt fraction through the overlying mantle as porosity waves (Richter & McKenzie 1984, Spiegelman 1993). Within those waves we expect porous flow to lead to the transport and mixing of distinct peridotite-derived lithologies (Kelemen 1997). A consequence of this mixing includes partitioning of trace elements in the partially molten, mixing lithologies. We begin our numeric experiment by imposing a partially molten region in a nearly impermeable background. As the partially molten region rises, the buoyant melt races to the front of the porosity wave. Once the melt reaches the edge of the porosity wave, it encounters an extreme drop in permeability. Though the melt within the porosity wave may move faster than the wave itself, the permeable region confines the melt. Since the melt cannot outrun the porosity wave, it would pool at the edge of the impermeable region. However, the porosity wave continues to rise around the melt. This causes the melt to appear to double back into the more permeable region within the porosity wave. After "turning back", the buoyant melt hugs the low permeability wall of the porosity wave as it continues to migrate. Near the bottom of the porosity wave the melt changes direction and begins to move upward again. The porosity wave and melt create a convective mixing cell. Modeled circulation of melt within the porosity wave could explain why the linear decoupling of trace

  15. Exploding Water Drops

    NASA Astrophysics Data System (ADS)

    Reich, Gary

    2016-01-01

    Water has the unusual property that it expands on freezing, so that ice has a specific gravity of 0.92 compared to 1.0 for liquid water. The most familiar demonstration of this property is ice cubes floating in a glass of water. A more dramatic demonstration is the ice bomb shown in Fig. 1. Here a cast iron flask is filled with water and tightly stoppered. The flask is then cooled, either by leaving it outdoors in winter or by immersing it in a cryogenic fluid, until the water freezes. As the water freezes and expands, the pressure inside the flask increases dramatically, eventually becoming sufficient to fracture the metal walls of the enclosure. A related, but much less familiar, phenomenon is the explosive fracturing of small water drops upon freezing. That water drops can fracture in this way has been known for many years, and the phenomenon has been described in detail in the atmospheric sciences literature, where it is seen as relevant to the freezing of raindrops as they fall through cold air. Carefully controlled experiments have been done documenting how the character and frequency of fracture is affected by such variables as drop size, rate of cooling, chemistry of dissolved gases, etc. Here I describe instead a simple demonstration of fracture suitable for video analysis and appropriate for study at the introductory physics level. Readers may also be interested in other characteristics of freezing and fragmenting water drops, for example, charge separation upon fracture and the appearance of spikes and bulges on the surface.

  16. Permeability and porosity of the Illinois UPH 3 drillhole granite and a comparison with other deep drillhole rocks

    USGS Publications Warehouse

    Morrow, C.A.; Lockner, D.A.

    1997-01-01

    Permeability, porosity, and volumetric strain measurements were conducted on granite cores obtained at depths of 0.7 to 1.6 km from the Illinois UPH 3 drillhole at effective confining pressures from 5 to 100 MPa. Initial permeabilities were in the range of 10-17 to 10-19 m2 and dropped rapidly with applied pressure to values between 10-20 and 10-24 m2 at 100 MPa, typical of other deep granite core samples. These values are several decades lower than equivalent weathered surface granites at comparable effective confining pressures, where weathering products in cracks and pores inhibit crack closure with applied pressure. Permeabilities of the Illinois cores were inversely related to sample depth, suggesting that stress relief and thermal microfractures induced during core retrieval dominated the fluid flow. Thus these samples provide an upper bound on in situ matrix permeability values. A comparison of core permeability from UPH 3 and other deep drillholes shows that stress relief damage can often dominate laboratory permeability measurements. We conclude that it may be difficult to make meaningful estimates of in situ permeability based on either borehole samples (possible damage during retrieval) or surface-derived analogs (altered by weathering). Volumetric strain determined from porosity measurements was compared with differential strain analysis (DSA) data reported by other investigators on samples from the same depths in the drillhole. Our strain measurements (0.002 to 0.005 at 100 MPa) were nearly twice as large as the DSA values, probably because of the crack-enhancing effects of fluids present in our samples that are absent in the dry DSA cores, as well as other time-dependent deformation effects. This difference in observed strain magnitudes between the two measurement methods may be an important consideration if strain and/or porosity data from deep core samples are used in models of stress, fluid circulation, and excess fluid pressure generation in the

  17. Superamphiphobic polymeric surfaces sustaining ultrahigh impact pressures of aqueous high- and low-surface-tension mixtures, tested with laser-induced forward transfer of drops.

    PubMed

    Ellinas, Kosmas; Chatzipetrou, Marianneza; Zergioti, Ioanna; Tserepi, Angeliki; Gogolides, Evangelos

    2015-04-01

    Superamphiphobic, (quasi-)ordered plasma-textured surfaces, coated with a perfluorinated monolayer, exhibit extreme resistance against drop-pinning for both water-like and low-surface-tension mixtures (36 mN m(-1)). The highest values reported here are 36 atm for a water-like mixture, 5 times higher than previously reported in the literature, and 7 atm for a low-surface-tension mixture, the highest ever reported value for lotus-leaf-inspired surfaces.

  18. Hemodynamic transition driven by stent porosity in sidewall aneurysms.

    PubMed

    Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Lovblad, Karl-Olof; Farhat, Mohamed; Pereira, Vitor Mendes

    2015-05-01

    The healing process of intracranial aneurysms (IAs) treated with flow diverter stents (FDSs) depends on the IA flow modifications and on the epithelization process over the neck. In sidewall IA models with straight parent artery, two main hemodynamic regimes with different flow patterns and IA flow magnitude were broadly observed for unstented and high porosity stented IA on one side, and low porosity stented IA on the other side. The hemodynamic transition between these two regimes is potentially involved in thrombosis formation. In the present study, CFD simulations and multi-time lag (MTL) particle imaging velocimetry (PIV) measurements were combined to investigate the physical nature of this transition. Measurable velocity fields and non-measurable shear stress and pressure fields were assessed experimentally and numerically in the aneurysm volume in the presence of stents with various porosities. The two main regimes observed in both PIV and CFD showed typical flow features of shear and pressure driven regimes. In particular, the waveform of the averaged IA velocities was matching both the shear stress waveform at IA neck or the pressure gradient waveform in parent artery. Moreover, the transition between the two regimes was controlled by stent porosity: a decrease of stent porosity leads to an increase (decrease) of pressure differential (shear stress) through IA neck. Finally, a good PIV-CFD agreement was found except in transitional regimes and low motion eddies due to small mismatch of PIV-CFD running conditions. PMID:25798761

  19. Brittle and semibrittle creep in a low porosity carbonate rock

    NASA Astrophysics Data System (ADS)

    Nicolas, Aurélien; Fortin, Jérôme; Regnet, Jean-Baptiste; Dimanov, Alexandre; Guéguen, Yves

    2016-04-01

    The mechanical behavior of limestones at room temperature is brittle at low confining pressure and becomes semi-brittle with the increase of the confining pressure. The brittle behavior is characterized by a macroscopic dilatancy due to crack propagation, leading to a stress drop when cracks coalesce at failure. The semi-brittle behavior is characterized by diffuse deformation due to intra-crystalline plasticity (dislocation movements and twinning) and microcracking. The aim of this work is to examine the influence of pore fluid and time on the mechanical behavior. Constant strain rate triaxial deformation experiments and stress-stepping creep experiments were performed on white Tavel limestone (porosity 14.7%). Elastic wave velocity evolutions were recorded during each experiment and inverted to crack densities. Constant strain rate triaxial experiments were performed for confining pressure in the range of 5-90 MPa. For Pc≤55 MPa our results show that the behavior is brittle. In this regime, water-saturation decreases the differential stress at the onset of crack propagation and enhances macroscopic dilatancy. For Pc≥70 MPa, the behavior is semi-brittle. Inelastic compaction is due to intra-crystalline plasticity and micro-cracking. However, in this regime, our results show that water-saturation has no clear effect at the onset of inelastic compaction. Stress stepping creep experiments were performed in a range of confining pressures crossing the brittle-ductile transition. In the brittle regime, the time-dependent axial deformation is coupled with dilatancy and a decrease of elastic wave velocities, which is characteristic of crack propagation and/or nucleation. In the semi-brittle regime, the first steps are inelastic compactant because of plastic pore collapse. But, following stress steps are dilatant because of crack nucleation and/or propagation. However, our results show that the axial strain rate is always controlled by plastic phenomena, until the last

  20. Sound field inside acoustically levitated spherical drop

    NASA Astrophysics Data System (ADS)

    Xie, W. J.; Wei, B.

    2007-05-01

    The sound field inside an acoustically levitated small spherical water drop (radius of 1mm) is studied under different incident sound pressures (amplitude p0=2735-5643Pa). The transmitted pressure ptr in the drop shows a plane standing wave, which varies mainly in the vertical direction, and distributes almost uniformly in the horizontal direction. The maximum of ptr is always located at the lowermost point of the levitated drop. Whereas the secondary maximum appears at the uppermost point if the incident pressure amplitude p0 is higher than an intermediate value (3044Pa), in which there exists a pressure nodal surface in the drop interior. The value of the maximum ptr lies in a narrow range of 2489-3173Pa, which has a lower limit of 2489Pa when p0=3044Pa. The secondary maximum of ptr is rather small and only remarkable at high incident pressures.

  1. Static Magnetowetting of Ferrofluid Drops.

    PubMed

    Rigoni, Carlo; Pierno, Matteo; Mistura, Giampaolo; Talbot, Delphine; Massart, René; Bacri, Jean-Claude; Abou-Hassan, Ali

    2016-08-01

    We report results of a comprehensive study of the wetting properties of sessile drops of ferrofluid water solutions at various concentrations deposited on flat substrates and subjected to the action of permanent magnets of different sizes and strengths. The amplitude and the gradient of the magnetic field experienced by the ferrofluid are changed by varying the magnets and their distance to the surface. Magnetic forces up to 100 times the gravitational one and magnetic gradients up to 1 T/cm are achieved. A rich phenomenology is observed, ranging from flattened drops caused by the magnetic attraction to drops extended normally to the substrate because of the normal traction of the magnetic field. We find that the former effect can be conveniently described in terms of an effective Bond number that compares the effective drop attraction with the capillary force, whereas the drop's vertical elongation is effectively expressed by a dimensionless number S, which compares the pressure jump at the ferrofluid interface because of the magnetization with the capillary pressure.

  2. Static Magnetowetting of Ferrofluid Drops.

    PubMed

    Rigoni, Carlo; Pierno, Matteo; Mistura, Giampaolo; Talbot, Delphine; Massart, René; Bacri, Jean-Claude; Abou-Hassan, Ali

    2016-08-01

    We report results of a comprehensive study of the wetting properties of sessile drops of ferrofluid water solutions at various concentrations deposited on flat substrates and subjected to the action of permanent magnets of different sizes and strengths. The amplitude and the gradient of the magnetic field experienced by the ferrofluid are changed by varying the magnets and their distance to the surface. Magnetic forces up to 100 times the gravitational one and magnetic gradients up to 1 T/cm are achieved. A rich phenomenology is observed, ranging from flattened drops caused by the magnetic attraction to drops extended normally to the substrate because of the normal traction of the magnetic field. We find that the former effect can be conveniently described in terms of an effective Bond number that compares the effective drop attraction with the capillary force, whereas the drop's vertical elongation is effectively expressed by a dimensionless number S, which compares the pressure jump at the ferrofluid interface because of the magnetization with the capillary pressure. PMID:27385506

  3. Equilibrium shapes of acoustically levitated drops

    NASA Astrophysics Data System (ADS)

    Trinh, E. H.; Hsu, C.-J.

    1986-05-01

    The quantitative determination of the shape of liquid drops levitated in an ultrasonic standing wave has provided experimental data on the radiation pressure-induced deformations of freely suspended liquids. Within the limits of small deviations from the spherical shape and small drop diameter relative to the acoustic wavelength, an existing approximate theory yields a good agreement with experimental evidence. The data were obtained for millimeter and submillimeter drops levitated in air under 1 g, where g is the sea level gravitational acceleration.

  4. Alternate drop pulse polarography

    USGS Publications Warehouse

    Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

    1976-01-01

    The new technique of alternate drop pulse polarography is presented. An experimental evaluation of alternate drop pulse polarography shows complete compensation of the capacitative background due to drop expansion. The capillary response phenomenon was studied in the absence of faradaic reaction and the capillary response current was found to depend on the pulse width to the -0.72 power. Increased signal-to-noise ratios were obtained using alternate drop pulse polarography at shorter drop times.

  5. Injector Element which Maintains a Constant Mean Spray Angle and Optimum Pressure Drop During Throttling by Varying the Geometry of Tangential Inlets

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P. (Inventor); Myers, William Neill (Inventor)

    2014-01-01

    A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The tangential inlet area for each throttleable stage is calculated. The correlation between the tangential inlet areas and delta pressure values is used to calculate the spring displacement and variable inlet geometry. An injector designed using the method includes a plurality of geometrically calculated tangential inlets in an injection tube; an injection tube cap with a plurality of inlet slots slidably engages the injection tube. A pressure differential across the injector element causes the cap to slide along the injection tube and variably align the inlet slots with the tangential inlets.

  6. Nanoscale porosity in SAFOD core samples (San Andreas Fault)

    NASA Astrophysics Data System (ADS)

    Janssen, Christoph; Wirth, Richard; Reinicke, Andreas; Rybacki, Erik; Naumann, Rudolf; Wenk, Hans-Rudolf; Dresen, Georg

    2011-01-01

    With transmission electron microscopy (TEM) we observed nanometer-sized pores in four ultracataclastic and fractured core samples recovered from different depths of the main bore hole of the San Andreas Fault Observatory at Depth (SAFOD). Cutting of foils with a focused ion beam technique (FIB) allowed identifying porosity down to the nm scale. Between 40 and 50% of all pores could be identified as in-situ pores without any damage related to sample preparation. The total porosity estimated from TEM micrographs (1-5%) is comparable to the connected fault rock porosity (2.8-6.7%) estimated by pressure-induced injection of mercury. Permeability estimates for cataclastic fault rocks are 10- 21-10- 19 m2 and 10- 17 m2 for the fractured fault rock. Porosity and permeability are independent of sample depth. TEM images reveal that the porosity is intimately linked to fault rock composition and associated with deformation. The TEM-estimated porosity of the samples increases with increasing clay content. The highest porosity was estimated in the vicinity of an active fault trace. The largest pores with an equivalent radius > 200 nm occur around large quartz and feldspar grains or grain-fragments while the smallest pores (equivalent radius < 50 nm) are typically observed in the extremely fine-grained matrix (grain size < 1 μm). Based on pore morphology we distinguish different pore types varying with fault rock fabric and alteration. The pores were probably filled with formation water and/or hydrothermal fluids at elevated pore fluid pressure, preventing pore collapse. The pore geometry derived from TEM observations and BET (Brunauer, Emmett and Teller) gas adsorption/desorption hysteresis curves indicates pore blocking effects in the fine-grained matrix. Observations of isolated pores in TEM micrographs and high pore body to pore throat ratios inferred from mercury injection suggest elevated pore fluid pressure in the low permeability cataclasites, reducing shear strength

  7. Porosity, single-phase permeability, and capillary pressure data from preliminary laboratory experiments on selected samples from Marker Bed 139 at the Waste Isolation Pilot Plant. Volume 3 of 3: Appendices C, D, E, and F

    SciTech Connect

    Howarth, S.M.; Christian-Frear, T.

    1997-08-01

    This volume contains the mineralogy, porosity, and permeability results from the Marker Bed 139 anhydrite specimens evaluated by TerraTek, Inc. for the Waste Isolation Pilot Plant. This volume also documents the brine recipe used by RE/SPEC, Inc., the parameter package submitted to Performance Assessment based on all the data, and a memo on the mixed Brooks and Corey two-phase characteristic curves.

  8. Dual porosity gas evolving electrode

    DOEpatents

    Townsend, Carl W.

    1994-01-01

    A dual porosity electrode for use in thermoelectrochemical systems where simultaneous transport of gas and liquid into and/or out of the electrode is required. The electrode includes catalytic electrode particles having diameters ranging from about 25 to 100 angstroms. The catalytic electrode particles are anchored to a support network in clusters which have internal pores ranging in size from 25 to 100 angstroms. The pores between the clusters range in size from between about 1 to 20 microns. A method for making the dual porosity electrodes is also disclosed.

  9. Dual porosity gas evolving electrode

    DOEpatents

    Townsend, C.W.

    1994-11-15

    A dual porosity electrode is described for use in thermoelectrochemical systems where simultaneous transport of gas and liquid into and/or out of the electrode is required. The electrode includes catalytic electrode particles having diameters ranging from about 25 to 100 angstroms. The catalytic electrode particles are anchored to a support network in clusters which have internal pores ranging in size from 25 to 100 angstroms. The pores between the clusters range in size from between about 1 to 20 microns. A method for making the dual porosity electrodes is also disclosed.

  10. Spatially resolved measurement of rock core porosity.

    PubMed

    Marica, F; Chen, Q; Hamilton, A; Hall, C; Al, T; Balcom, B J

    2006-01-01

    Density weighted, centric scan, Conical SPRITE MRI techniques are applied in the current work for local porosity measurements in fluid saturated porous media. The methodology is tested on a series of sandstone core samples. These samples vary in both porosity and degree of local heterogeneity due to bedding plane structure. The MRI porosity measurement is in good agreement with traditional gravimetric measurements of porosity. Spatially resolved porosity measurements reveal significant porosity variation in some samples. This novel MRI technique should have applications to the characterization of local porosity in a wide variety of porous media. PMID:16216540

  11. Spatially resolved measurement of rock core porosity.

    PubMed

    Marica, F; Chen, Q; Hamilton, A; Hall, C; Al, T; Balcom, B J

    2006-01-01

    Density weighted, centric scan, Conical SPRITE MRI techniques are applied in the current work for local porosity measurements in fluid saturated porous media. The methodology is tested on a series of sandstone core samples. These samples vary in both porosity and degree of local heterogeneity due to bedding plane structure. The MRI porosity measurement is in good agreement with traditional gravimetric measurements of porosity. Spatially resolved porosity measurements reveal significant porosity variation in some samples. This novel MRI technique should have applications to the characterization of local porosity in a wide variety of porous media.

  12. Electrohydrodynamics of a viscous drop with inertia.

    PubMed

    Nganguia, H; Young, Y-N; Layton, A T; Lai, M-C; Hu, W-F

    2016-05-01

    Most of the existing numerical and theoretical investigations on the electrohydrodynamics of a viscous drop have focused on the creeping Stokes flow regime, where nonlinear inertia effects are neglected. In this work we study the inertia effects on the electrodeformation of a viscous drop under a DC electric field using a novel second-order immersed interface method. The inertia effects are quantified by the Ohnesorge number Oh, and the electric field is characterized by an electric capillary number Ca_{E}. Below the critical Ca_{E}, small to moderate electric field strength gives rise to steady equilibrium drop shapes. We found that, at a fixed Ca_{E}, inertia effects induce larger deformation for an oblate drop than a prolate drop, consistent with previous results in the literature. Moreover, our simulations results indicate that inertia effects on the equilibrium drop deformation are dictated by the direction of normal electric stress on the drop interface: Larger drop deformation is found when the normal electric stress points outward, and smaller drop deformation is found otherwise. To our knowledge, such inertia effects on the equilibrium drop deformation has not been reported in the literature. Above the critical Ca_{E}, no steady equilibrium drop deformation can be found, and often the drop breaks up into a number of daughter droplets. In particular, our Navier-Stokes simulations show that, for the parameters we use, (1) daughter droplets are larger in the presence of inertia, (2) the drop deformation evolves more rapidly compared to creeping flow, and (3) complex distribution of electric stresses for drops with inertia effects. Our results suggest that normal electric pressure may be a useful tool in predicting drop pinch-off in oblate deformations. PMID:27300985

  13. Electrohydrodynamics of a viscous drop with inertia.

    PubMed

    Nganguia, H; Young, Y-N; Layton, A T; Lai, M-C; Hu, W-F

    2016-05-01

    Most of the existing numerical and theoretical investigations on the electrohydrodynamics of a viscous drop have focused on the creeping Stokes flow regime, where nonlinear inertia effects are neglected. In this work we study the inertia effects on the electrodeformation of a viscous drop under a DC electric field using a novel second-order immersed interface method. The inertia effects are quantified by the Ohnesorge number Oh, and the electric field is characterized by an electric capillary number Ca_{E}. Below the critical Ca_{E}, small to moderate electric field strength gives rise to steady equilibrium drop shapes. We found that, at a fixed Ca_{E}, inertia effects induce larger deformation for an oblate drop than a prolate drop, consistent with previous results in the literature. Moreover, our simulations results indicate that inertia effects on the equilibrium drop deformation are dictated by the direction of normal electric stress on the drop interface: Larger drop deformation is found when the normal electric stress points outward, and smaller drop deformation is found otherwise. To our knowledge, such inertia effects on the equilibrium drop deformation has not been reported in the literature. Above the critical Ca_{E}, no steady equilibrium drop deformation can be found, and often the drop breaks up into a number of daughter droplets. In particular, our Navier-Stokes simulations show that, for the parameters we use, (1) daughter droplets are larger in the presence of inertia, (2) the drop deformation evolves more rapidly compared to creeping flow, and (3) complex distribution of electric stresses for drops with inertia effects. Our results suggest that normal electric pressure may be a useful tool in predicting drop pinch-off in oblate deformations.

  14. Flowmeter for pressure-driven chromatography systems

    DOEpatents

    Paul, Phillip H.; Arnold, Don W.

    2002-01-01

    A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 .mu.m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of .mu.L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

  15. Flowmeter for pressure-driven chromatography systems

    DOEpatents

    Paul, Phillip H.; Arnold, Don W.

    2003-01-01

    A flowmeter for accurately measuring the flowrate of fluids in high pressure chromatography systems. The flowmeter is a porous bed of a material, the porous bed having a porosity in the range of about 0.1 to 0.6 and a pore size in the range of about 50 nm to 1 .mu.m, disposed between a high pressure pumping means and a chromatography column. The flowmeter is provided with pressure measuring means at both the inlet and outlet of the porous bed for measuring the pressure drop through the porous bed. This flowmeter system provides not only the ability to measure accurately flowrates in the range of .mu.L/min to nL/min but also to provide a signal that can be used for a servo loop or feedback control system for high pressure pumping systems.

  16. The Porosity of 433 Eros

    NASA Technical Reports Server (NTRS)

    Britt, D. T.; Yeomans, Donald K.; Consolmagno, G. J.

    2001-01-01

    Data from the NEAR mission show the bulk density of 433 Eros is 2.67 g/cm 3 . Given an L or LL composition, the bulk porosity of Eros is in the range of 25-29% and the macroporosity is 14-18%. This is consistent with a fractured, but coherent asteroid. Additional information is contained in the original extended abstract.

  17. Ternary drop collisions

    NASA Astrophysics Data System (ADS)

    Hinterbichler, Hannes; Planchette, Carole; Brenn, Günter

    2015-10-01

    It has been recently proposed to use drop collisions for producing advanced particles or well-defined capsules, or to perform chemical reactions where the merged drops constitute a micro-reactor. For all these promising applications, it is essential to determine whether the merged drops remain stable after the collision, forming a single entity, or if they break up. This topic, widely investigated for binary drop collisions of miscible and immiscible liquid, is quite unexplored for ternary drop collisions. The current study aims to close this gap by experimentally investigating collisions between three equal-sized drops of the same liquid arranged centri-symmetrically. Three drop generators are simultaneously operated to obtain controlled ternary drop collisions. The collision outcomes are observed via photographs and compared to those of binary collisions. Similar to binary collisions, a regime map is built, showing coalescence and bouncing as well as reflexive and stretching separation. Significant differences are observed in the transitions between these regimes.

  18. Dilating Eye Drops

    MedlinePlus

    ... Conditions Most Common Searches Adult Strabismus Amblyopia Cataract Conjunctivitis Corneal Abrasions Dilating Eye Drops Lazy eye (defined) ... Loading... Most Common Searches Adult Strabismus Amblyopia Cataract Conjunctivitis Corneal Abrasions Dilating Eye Drops Lazy eye (defined) ...

  19. Attracting Water Drops

    NASA Video Gallery

    Astronauts Cady Coleman and Ron Garan perform the Attracting Water Drops experiment from Chabad Hebrew Academy in San Diego, Calif. This research determines if a free-floating water drop can be att...

  20. Apfel's superheated drop detector

    NASA Astrophysics Data System (ADS)

    D'Errico, Francesco

    2001-05-01

    The introduction of new approaches for radiation dosimetry is rare. A similar breakthrough occurred in 1979, when Robert Apfel invented the superheated drop detector, a miniature relative of the bubble chamber. A fundamental in high-energy particle physics, the bubble chamber utilizes a liquid briefly brought to a transient, radiation-sensitive superheated state by reducing its pressure. Mass boiling of the liquid is prevented by cyclic pressurization, drastically limiting the detection efficiency. In Apfel's detector, the liquid is kept in a steady superheated state by fractionating it into droplets and dispersing them in an immiscible host fluid, a perfectly smooth and clean container. The approach extends the lifetime of the metastable droplets to the point that practical application in radiation dosimetry is possible. Bubble formation is measured from the volume of vapor or by detecting individual vaporizations acoustically. Various halocarbons are employed and this permits a wide range of applications. Moderately superheated halocarbons are used for neutron measurements, since they are only nucleated by energetic neutron recoil particles. Highly superheated halocarbons nucleate with much smaller energy deposition and are used to detect photons and electrons. This paper reviews the radiation physics of superheated emulsions and their manifold applications.

  1. Longhi Games, Internal Reservoirs, and Cumulate Porosity

    NASA Astrophysics Data System (ADS)

    Morse, S. A.

    2009-05-01

    Fe in plagioclase at an early age, T-rollers (or not) on the Di-Trid boundary in Fo-Di-Sil, the mantle solidus, origins of anorthosites, esoteric uses of Schreinemakers rules and many more topics are all fresh and pleasant memories of John Longhi's prolific and creative work. The Fram-Longhi experimental effect of pressure on plagioclase partitioning with liquid in mafic rocks became essential to an understanding of multiphase Rayleigh fractionation of plagioclase in big layered intrusions. Only by using the pressure effect could I find a good equation through the data for the Kiglapait intrusion, and that result among others required the existence with probability 1.0 of an internal reservoir (Morse, JPet 2008). Knowledge of cumulate porosity is a crucial key to the understanding of layered igneous rocks. We seek both the initial (inverse packing fraction) and residual porosity to find the time and process path from sedimentation to solidification. In the Kiglapait Lower Zone we have a robust estimate of mean residual porosity from the modes of the excluded phases augite, oxides, sulfide, and apatite. To this we apply the maximum variance of plagioclase composition (the An range) to find an algorithm that extends through the Upper Zone and to other intrusions. Of great importance is that all these measurements were made in grain mounts concentrated from typically about 200 g of core or hand specimen, hence the represented sample volume is thousands of times greater than for a thin section. The resulting distribution and scatter of the An range is novel and remarkable. It is V-shaped in the logarithmic representation of stratigraphic height, running from about 20 mole % at both ends (base to top of the Layered Series) to near-zero at 99 PCS. The intercept of the porosity-An range relation gives An range = 3.5 % at zero residual porosity. Petrographic analysis reveals that for PCS less than 95 and greater than 99.9, the An range is intrinsic, i.e. pre-cumulus, for

  2. Non-coalescence of oppositely charged drops.

    PubMed

    Ristenpart, W D; Bird, J C; Belmonte, A; Dollar, F; Stone, H A

    2009-09-17

    Electric fields induce motion in many fluid systems, including polymer melts, surfactant micelles and colloidal suspensions. Likewise, electric fields can be used to move liquid drops. Electrically induced droplet motion manifests itself in processes as diverse as storm cloud formation, commercial ink-jet printing, petroleum and vegetable oil dehydration, electrospray ionization for use in mass spectrometry, electrowetting and lab-on-a-chip manipulations. An important issue in practical applications is the tendency for adjacent drops to coalesce, and oppositely charged drops have long been assumed to experience an attractive force that favours their coalescence. Here we report the existence of a critical field strength above which oppositely charged drops do not coalesce. We observe that appropriately positioned and oppositely charged drops migrate towards one another in an applied electric field; but whereas the drops coalesce as expected at low field strengths, they are repelled from one another after contact at higher field strengths. Qualitatively, the drops appear to 'bounce' off one another. We directly image the transient formation of a meniscus bridge between the bouncing drops, and propose that this temporary bridge is unstable with respect to capillary pressure when it forms in an electric field exceeding a critical strength. The observation of oppositely charged drops bouncing rather than coalescing in strong electric fields should affect our understanding of any process involving charged liquid drops, including de-emulsification, electrospray ionization and atmospheric conduction. PMID:19759616

  3. Pressure drop, heat transfer, critical heat flux, and flow stability of two-phase flow boiling of water and ethylene glycol/water mixtures - final report for project "Efficent cooling in engines with nucleate boiling."

    SciTech Connect

    Yu, W.; France, D. M.; Routbort, J. L.

    2011-01-19

    Because of its order-of-magnitude higher heat transfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and to eliminate potential hot spots in engines. However, the fundamental understanding of flow boiling mechanisms of a 50/50 ethylene glycol/water mixture under engineering application conditions is still limited. In addition, it is impractical to precisely maintain the volume concentration ratio of the ethylene glycol/water mixture coolant at 50/50. Therefore, any investigation into engine coolant characteristics should include a range of volume concentration ratios around the nominal 50/50 mark. In this study, the forced convective boiling heat transfer of distilled water and ethylene glycol/water mixtures with volume concentration ratios of 40/60, 50/50, and 60/40 in a 2.98-mm-inner-diameter circular tube has been investigated in both the horizontal flow and the vertical flow. The two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux of the test fluids were determined experimentally over a range of the mass flux, the vapor mass quality, and the inlet subcooling through a new boiling data reduction procedure that allowed the analytical calculation of the fluid boiling temperatures along the experimental test section by applying the ideal mixture assumption and the equilibrium assumption along with Raoult's law. Based on the experimental data, predictive methods for the two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux under engine application conditions were developed. The results summarized in this final project report provide the necessary information for designing and implementing nucleate-boiling vehicular cooling systems.

  4. Determination of musk fragrances in sewage sludge by pressurized liquid extraction coupled to automated ionic liquid-based headspace single-drop microextraction followed by GC-MS/MS.

    PubMed

    Vallecillos, Laura; Borrull, Francesc; Pocurull, Eva

    2012-10-01

    A method for the quantitative determination of ten musk fragrances extensively used in personal care products from sewage sludge was developed by using a pressurized liquid extraction (PLE) followed by an automated ionic liquid-based headspace single-drop microextraction and gas chromatography-tandem mass spectrometry. The influence of main factors on the efficiency of PLE was studied. For all musks, the highest recovery values were achieved using 1 g of pretreated sewage sludge, H(2) O/methanol (1:1) as an extraction solvent, a temperature of 80°C, a pressure of 1500 psi, an extraction time of 5 min, 2 cycles, a 100% flush volume, a purge time of 120 s, and 1 g Florisil as in-cell clean-up extraction sorbent. The use and optimization of an in-cell clean-up sorbent was necessary to remove fatty interferents of the PLE extract that make the subsequent ionic liquid-based headspace single-drop microextraction difficult. Validation parameters, namely LODs and LOQs, ranged from 0.5-1.5 to 2.5-5 ng/g, respectively. Good levels of intra- and interday repeatabilities were obtained analyzing sewage sludge samples spiked at 10 ng/g (n = 3, RSDs < 10%). The method applicability was tested with sewage sludge from different wastewater treatment plants. The analysis revealed the presence of all the polycyclic musks studied at concentrations higher than the LOQs, ranging from 6 to 530 ng/g. However, the nitro musk concentrations were below the LOQs or, in the case of musk xylene, was not detected.

  5. Confined-unconfined changes above longwall coal mining due to increases in fracture porosity

    SciTech Connect

    Booth, C.J.

    2007-11-15

    Subsidence and strata movement above longwall (total extraction) coal mines produce complex hydrologic responses that can occur independently of drainage to the mine. One response is dewatering from confined to unconfined conditions in bedrock aquifers as a result of loss of water into new void space created by fracture and bedding separations. This dewatering process has been little studied but accounts for several hydraulic and geochemical effects of longwall mining. This article presents a conceptual model of the process and reviews evidence from case studies. Confined bedrock aquifers in subsiding zones exhibit dramatically steep head drops because of the low value of confined storage coefficients relative to the volume of water drained into the new fracture void space. The aquifer changes rapidly to an unconfined condition. Tight units to which air entry is restricted may even develop negative water pressures. In the unconfined state, sulfide minerals present in the strata readily oxidize to soluble hydrated sulfates. When the aquifer re-saturates, these salts are rapidly mobilized and produce a flush of increased sulfate and total dissolved solids (TDS) levels. Observations made in our previous studies in Illinois are consistent with the confined-unconfined model and include rapid head drops, changes to unconfined conditions, and increases in sulfate and TDS during re-saturation of a sandstone aquifer. Studies reported from the Appalachian coalfield show aspects consistent with the model, but in this high-relief fractured setting it is often difficult to distinguish aquifers from aquitards, confined from unconfined states, and the fracture-porosity cause of head drops from several others that occur during mine subsidence.

  6. Micro-explosion of compound drops

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Kuei; Lin, Ta-Hui

    2014-08-01

    Introducing water into spray combustion systems, by either water-in-oil emulsification or supplementary water injection, is one of the major techniques for combustion improvement and NOx reduction. Plentiful researches are available on combustion of water-in-oil emulsion fuel drops. The emulsified liquid is a heterogeneous mixture of immiscible liquids. One component forms the continuous phase and the other component forms the discrete phase. The discrete phase consists of globules of the one fluid that are suspended in the continuous phase fluid. Water-in-oil emulsions are commonly considered for combustion applications because emulsions can result in micro-explosion, thereby reducing the average drop diameter to enhance liquid vaporization, and suppressing the formation of soot and NOx. However, the water addition generally does not exceed about 20% for smooth engine operations[!, 21. The combustion characteristics and micro-explosion of emulsion drop were studied by many researchers. The micro-explosion of water in fuel emulsion drops was caused by very fast growth of superheated water vapor bubbles, its superheat limits must be lower than the boiling point temperature of the fuel. These bubbles were primarily governed by the pressure difference between the superheated vapor and the liquid, and by the inertia imparted to the liquid by the motion of the bubble surface[3 6 In this study, we used a coaxial nozzle to generation the multi-component drop. The different type of water-in-oil fuel drops called the compound drops. Unlike an emulsion drop, a compound drop consists of a water core and a fuel shell, which can originate from the phase separation of emulsion[7, 81 or a water drop colliding with a fuel drop[9, 101 Burning and micro-explosion of compound drops have been found to be distinct from those of emulsion drops[9-111 Wang et al.[9 , 101 studied the combustion characteristics of collision merged alkane-water drops. The merged drops appeared in adhesive

  7. Drag on Sessile Drops

    NASA Astrophysics Data System (ADS)

    Milne, Andrew J. B.; Fleck, Brian; Nobes, David; Sen, Debjyoti; Amirfazli, Alidad; University of Alberta Mechanical Engineering Collaboration

    2013-11-01

    We present the first ever direct measurements of the coefficient of drag on sessile drops at Reynolds numbers from the creeping flow regime up to the point of incipient motion, made using a newly developed floating element differential drag sensor. Surfaces of different wettabilities (PMMA, Teflon, and a superhydrophobic surface (SHS)), wet by water, hexadecane, and various silicone oils, are used to study the effects of drop shape, and fluid properties on drag. The relation between drag coefficient and Reynolds number (scaled by drop height) varies slightly with liquid-solid system and drop volume with results suggesting the drop experiences increased drag compared to similar shaped solid bodies due to drop oscillation influencing the otherwise laminar flow. Drops adopting more spherical shapes are seen to experience the greatest force at any given airspeed. This indicates that the relative exposed areas of drops is an important consideration in terms of force, with implications for the shedding of drops in applications such as airfoil icing and fuel cell flooding. The measurement technique used in this work can be adapted to measure drag force on other deformable, lightly adhered objects such as dust, sand, snow, vesicles, foams, and biofilms. The authours acknowledge NSERC, Alberta Innovates Technology Futures, and the Killam Trusts.

  8. Pressure-flow relationships for packed beds of compressible chromatography media at laboratory and production scale.

    PubMed

    Stickel, J J; Fotopoulos, A

    2001-01-01

    Pressure drop across chromatography beds employing soft or semirigid media can be a significant problem in the operation of large-scale preparative chromatography columns. The shape or aspect ratio (length/diameter) of a packed bed has a significant effect on column pressure drop due to wall effects, which can result in unexpectedly high pressures in manufacturing. Two types of agarose-based media were packed in chromatography columns at various column aspect ratios, during which pressure drop, bed height, and flow rate were carefully monitored. Compression of the packed beds with increasing flow velocities was observed. An empirical model was developed to correlate pressure drop with the aspect ratio of the packed beds and the superficial velocity. Modeling employed the Blake-Kozeny equation in which empirical relationships were used to predict bed porosity as a function of aspect ratio and flow velocity. Model predictions were in good agreement with observed pressure drops of industrial scale chromatography columns. A protocol was developed to predict compression in industrial chromatography applications by a few laboratory experiments. The protocol is shown to be useful in the development of chromatographic methods and sizing of preparative columns.

  9. Generalized Charts for Determination of Pressure Drop of a High-speed Compressible Fluid in Heat-exchanger Passages I : Air Heated in Smooth Passages of Constant Area with Constant Wall Temperature

    NASA Technical Reports Server (NTRS)

    Valerino, Michael F

    1948-01-01

    In the present paper an analysis is made of the compressible-flow variations occurring in heat-exchanger passages. The results of the analysis describe the flow and heating characteristics for which specific flow passages can be treated as segments of generalized flow systems. The graphical representation of the flow variations in the generalized flow systems can then be utilized as working charts to determine directly the pressure changes occurring in any specific flow passage. On the basis of these results, working charts are constructed to handle the case of air heated at constant wall temperature under turbulent-flow conditions. A method is given of incorporating the effect on the heat-exchanger flow process of high temperature differential between passage wall and fluid as based on recent NACA experimental data. Good agreement is obtained between the experimental and the chart pressure-drop values for passage-wall average temperatures as high as 1752 degrees R (experimental limit) and for flow Mach numbers ranging from 0.32 to 1.00 (choke) at the passage exit.

  10. Youth Crime Drop. Report.

    ERIC Educational Resources Information Center

    Butts, Jeffrey A.

    This report examines the recent drop in violent crime in the United States, discussing how much of the decrease seen between 1995-99 is attributable to juveniles (under age 18 years) and older youth (18-24 years). Analysis of current FBI arrest data indicates that not only did America's violent crime drop continue through 1999, but falling youth…

  11. Drop Tower Physics

    ERIC Educational Resources Information Center

    Dittrich, William A.

    2014-01-01

    The drop towers of yesteryear were used to make lead shot for muskets, as described in "The Physics Teacher" in April 2012. However, modern drop towers are essentially elevators designed so that the cable can "break" on demand, creating an environment with microgravity for a short period of time, currently up to nine seconds at…

  12. Axisymmetric Liquid Hanging Drops

    ERIC Educational Resources Information Center

    Meister, Erich C.; Latychevskaia, Tatiana Yu

    2006-01-01

    The geometry of drops hanging on a circular capillary can be determined by numerically solving a dimensionless differential equation that is independent on any material properties, which enables one to follow the change of the height, surface area, and contact angle of drops hanging on a particular capillary. The results show that the application…

  13. Effective Thermal Conductivity of High Porosity Open Cell Nickel Foam

    NASA Technical Reports Server (NTRS)

    Sullins, Alan D.; Daryabeigi, Kamran

    2001-01-01

    The effective thermal conductivity of high-porosity open cell nickel foam samples was measured over a wide range of temperatures and pressures using a standard steady-state technique. The samples, measuring 23.8 mm, 18.7 mm, and 13.6 mm in thickness, were constructed with layers of 1.7 mm thick foam with a porosity of 0.968. Tests were conducted with the specimens subjected to temperature differences of 100 to 1000 K across the thickness and at environmental pressures of 10(exp -4) to 750 mm Hg. All test were conducted in a gaseous nitrogen environment. A one-dimensional finite volume numerical model was developed to model combined radiation/conduction heat transfer in the foam. The radiation heat transfer was modeled using the two-flux approximation. Solid and gas conduction were modeled using standard techniques for high porosity media. A parameter estimation technique was used in conjunction with the measured and predicted thermal conductivities at pressures of 10(exp -4) and 750 mm Hg to determine the extinction coefficient, albedo of scattering, and weighting factors for modeling the conduction thermal conductivity. The measured and predicted conductivities over the intermediate pressure values differed by 13%.

  14. Sessile Rayleigh drop instability

    NASA Astrophysics Data System (ADS)

    Steen, Paul; Bostwick, Josh

    2012-11-01

    Rayleigh (1879) determined the mode shapes and frequencies of the inviscid motion of a free drop held by surface tension. We study the inviscid motions of a sessile Rayleigh drop - a drop which rests on a planar solid and whose contact-line is free to move. Linear stability analysis gives the modes and frequencies of the droplet motions. In this talk, we focus on the ``walking instability,'' an unstable mode wherein the drop moves across a planar substrate in an inviscid rocking-like motion. The mode shape is non-axisymmetric. Although the experimental literature has hinted at such a mode, this is the first prediction from linear stability analysis, as far as we are aware. The ``walking instability'' of the drop converts energy stored in the liquid shape into the energy of liquid motion - which represents a heretofore unknown pathway of energy conversion of potentially wide significance for a broad range of applications.

  15. Thermal properties of heterogeneous granular materials - control of grain porosity,packing porosity, and paste-phase -

    NASA Astrophysics Data System (ADS)

    Kurita, K.; Iwasaki, A.; Toyota, T.; Baratoux, D.

    2010-12-01

    Thermal conductivity of granular materials is an important parameter to characterize the nature of planetary surface. Interpretation of thermal inertia obtained by planetary explorations requires physical understanding of the thermal properties. Because of this extensive laboratory investigations have been conducted to characterize them( Preseley and Christensen 1997,Huetter et al 2008 for examples). The basic principal factor in controlling thermal conductivity of granular aggregates at martian surface pressure is widely considered as grain size, but there are also other critical factors to be considered. Interpretation of thermal inertia value in terms of only grain size sometimes would overlook essential nature. Here we present how the thermal conductivity of heterogeneous granular aggregates is modeled by grain size, grain porosity, packing porosity and existence of paste-phase based on measurements of thermal conductivity of vesiculated materials under vacuum and atmospheric pressure. We should note different role of packing porosity and grain porosity. The samples are collections of vesiculated pyroclasts of pumice/scoria having grain porosity up to 0.7 and vesiculated glass beads. Monodispersed/polydispersed samples are prepared by arranging shivered fractions. The average grain size is 40 microns to 6mm. For monodispered aggregate prepared by normal tapping thermal conductivity seems to follow a unique function of the bulk porosity under atmospheric pressure. The conductivity changes from 0.25 to 0.05 W/mK in the bulk porosity of 0.4 to 0.96, respectively. The packing porosity is about 0.4 for all the monodispersed samples under normal tapping preparation. This corresponds to random close packing state, where similar number of grain contact mostly controls thermal conduction between grains. Polydispersed samples are prepared by mixing two grain sizes:50 micron and 4000 micron with variable fractions. Change of the conductivity in terms of bulk porosity is

  16. Dehydration-induced porosity waves and episodic tremor and slip

    NASA Astrophysics Data System (ADS)

    Skarbek, Rob M.; Rempel, Alan W.

    2016-02-01

    Episodic tremor and slip (ETS) along the subduction interface takes place where there is abundant evidence for elevated, near-lithostatic pore pressures, at sufficiently great depths (30-45 km) that chemical dehydration reactions must act as their dominant source. We simulate fluid and heat flow while tracking the location of a vertically oriented, one-dimensional column of material as it subducts through the slow slip and tremor zone. The material in the column is transformed through a pressure-dependent and temperature-dependent dehydration reaction that we describe with a generalized nonlinear kinetic rate law. Column deformation is largely dominated by viscous creep, with a closure rate that depends linearly on porosity. This behavior causes the dehydration reaction to generate traveling porosity waves that transport increased fluid pressures within the slow slip region. To explore the possibility that the observed periodicity of slow slip and tremor in subduction zones can be explained by the migration of such porosity waves, we derive a dispersion relation that accurately describes our numerical results. We also obtain an expression for how the thickness of the dehydrating layer is expected to vary as a function of the parameters in the reaction rate law. Although the amplitudes of pore pressure perturbations rival those that are produced by known external forcings (e.g., tides or passing surface waves), our analysis suggests that given reasonable estimates of rock viscosity, permeabilities in the range 6.5×10-15 to 5×10-10 m2 are required for porosity wave trains to form at periods comparable to those of slow slip and tremor.

  17. A Novel Porosity Model for Use in Hydrocode Simulations

    NASA Technical Reports Server (NTRS)

    Wuennemann, K.; Collins, G. S.; Melosh, H. J.

    2005-01-01

    Introduction: Numerical modeling of impact cratering has reached a high degree of sophistication; however, the treatment of porous materials still poses a large problem in hydrocode calculations. Porosity plays only a minor role in the formation of large craters on most planetary objects, but impacts on comets are believed to be highly affected by the presence of porosity, which may be as much as 80%. The upcoming Deep Impact Mission (launched January 2005) will provide more detailed data about the composition of a comet (Tempel 1) by shooting a approx.370 kg projectile onto the surface of its nucleus. The numerical simulations of such impact events requires an appropriate model for how pore space in the comet is crushed out during the violent initial stage of the impact event. Most hydro-codes compute the pressure explicitly using an "equation of state" (EOS) for each material, which relates changes in density and internal energy to changes in pressure. The added complication introduced by porosity is that changes in a material s density are due to both the closing of pore space (compaction) and compression of the matrix. The amount of resistance to volume change and the amount of irreversible work done during these two processes is very different; it is far easier to compact a porous material sample than to compress a non-porous sample of the same material. As an alternative to existing porosity models, like the Pdot(alpha) model [1], we present a novel approach for dealing with the compaction of porosity in hydrocode calculations.

  18. Porosity in metal-organic framework glasses.

    PubMed

    Thornton, A W; Jelfs, K E; Konstas, K; Doherty, C M; Hill, A J; Cheetham, A K; Bennett, T D

    2016-03-01

    The porosity of a glass formed by melt-quenching a metal-organic framework, has been characterized by positron annihilation lifetime spectroscopy. The results reveal porosity intermediate between the related open and dense crystalline frameworks ZIF-4 and ZIF-zni. A structural model for the glass was constructed using an amorphous polymerization algorithm, providing additional insight into the gas-inaccessible nature of porosity and the possible applications of hybrid glasses.

  19. Porosity determination of thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Van Roode, Mark; Beardsley, Brad

    1988-01-01

    Coating porosity is believed to be a critical factor for the thermal conductivity of thermal barrier coatings (TBCs). A number of different techniques have been used to determine the porosities of thermal barrier coatings for diesel applications as part of a NASA/DOE sponsored study. A comparison is made between methods based on water immersion, optical microscopy, eddy current thickness measurements, and Archimedes principle for TBC porosity determination.

  20. Liquid Metal Drop Impingement

    NASA Astrophysics Data System (ADS)

    Che, Judy; Han, Jaehoon; Tryggvason, Gretar; Ceccio, Steven

    1996-11-01

    "Ballistic Partical Manufacturing" is a process in which individual drops are layered to form a part. We examine how metal drops deform and solidify, and how the solidification rate affects the material microstructure using both numerical simulations and experiments. A single set of equations governing the conservation of mass, energy, and momentum are written for all phases involved, and the phase boundary is treated as an imbedded interface by adding the appropriate source terms. We have simulated single drops colliding with a surface using a simple model which assumes that a melt solidifies below the melting point. Although simple, this model captures many aspects of the fluid flow and solidification. The experimental apparatus creates a single drop of prescribed size and propels it toward a cooled substrate. Favorable comparisons of experimental and numerical results have been achieved.

  1. Drop Tower Workshop

    NASA Technical Reports Server (NTRS)

    Urban, David

    2013-01-01

    Ground based microgravity facilities are an important proving ground for space experiments, ground-based research and space hardware risk mitigation. An overview of existing platforms will be discussed with an emphasis on drop tower capabilities. The potential for extension to partial gravity conditions will be discussed. Input will be solicited from attendees for their potential to use drop towers in the future and the need for enhanced capabilities (e.g. partial gravity)

  2. Modeling of drop breakup in the bag breakup regime

    NASA Astrophysics Data System (ADS)

    Wang, C.; Chang, S.; Wu, H.; Xu, J.

    2014-04-01

    Several analytic models for predicting the drop deformation and breakup have been developed over the last three decades, but modeling drop breakup in the bag-type regime is less reported. In this Letter, a breakup model has been proposed to predict the drop deformation length and breakup time in the bag-type breakup regime in a more accurate manner. In the present model, the drop deformation which is approximately as the displacement of the centre of mass (c. m.) along the axis located at the centre of the drop, and the movement of c. m. is obtained by solving the pressure balance equation. The effects of the drop deformation on the drop external aerodynamic force are considered in this model. Drop breakup occurs when the deformation length reaches the maximum value and the maximum deformation length is a function of Weber number. The performance and applicability of the proposed breakup model are tested against the published experimental data.

  3. (De)compaction of porous viscoelastoplastic media: Solitary porosity waves

    NASA Astrophysics Data System (ADS)

    Yarushina, Viktoriya M.; Podladchikov, Yuri Y.; Connolly, James A. D.

    2015-07-01

    Buoyancy-driven flow in deformable porous media is important for understanding sedimentary compaction as well as magmatic and metamorphic differentiation processes. Here mathematical analysis of the viscoplastic compaction equations is used to develop an understanding of the porosity wave instability and its sensitivity to the choice of rheological model. The conditions of propagation, size, speed, and shape of the porosity waves depend strongly on the properties of the solid rock frame. Whereas most of the previous studies on porosity waves were focused on viscous or viscoelastic mode, here we consider the ability of a solid matrix to undergo simultaneous plastic (rate-independent) and viscous (rate-dependent) deformation in parallel. Plastic yielding is identified as a cause of compaction-decompaction asymmetry in porous media—this is known to lead to a strong focusing of porous flow. Speed and amplitude of a porosity wave are given as functions of material parameters and a volume of a source region. Formulation is applicable to fluid flow in sedimentary rocks where viscous deformation is due to pressure solution as well as in deep crustal or upper mantle rocks deforming in a semibrittle regime.

  4. Hanging drop crystal growth apparatus and method

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor); Smith, Robbie E. (Inventor)

    1989-01-01

    An apparatus (10) is constructed having a cylindrical enclosure (16) within which a disc-shaped wicking element (18) is positioned. A well or recess (22) is cut into an upper side (24) of this wicking element, and a glass cover plate or slip (28) having a protein drop disposed thereon is sealably positioned on the wicking element (18), with drop (12) being positioned over well or recess (22). A flow of control fluid is generated by a programmable gradient former (16), with this control fluid having a vapor pressure that is selectively variable. This flow of control fluid is coupled to the wicking element (18) where control fluid vapor diffusing from walls (26) of the recess (22) is exposed to the drop (12), forming a vapor pressure gradient between the drop (12) and the control fluid vapor. Initially, this gradient is adjusted to draw solvent from the drop (12) at a relatively high rate, and as the critical supersaturation point is approached (the point at which crystal nucleation occurs), the gradient is reduced to more slowly draw solvent from the drop (12). This allows discrete protein molecules more time to orient themselves into an ordered crystalline lattice, producing protein crystals which, when processed by X-ray crystallography, possess a high degree of resolution.

  5. Quantitative method for analysis of monensin in soil, water, and urine by direct combination of single-drop microextraction with atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Sekar, Ramaiyan; Wu, Hui-Fen

    2006-09-15

    A simple and selective analytical method for the quantitative determination of low concentrations of monensin in soil, surface water, and human urine has been developed. Prior to atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) analysis, the samples were preconcentrated by using the single-drop microextraction (SDME) technique. Several factors that affect the analyte's extraction, including selection of solvent, microdrop volume, extraction time, and ionic strength, were investigated. Chloroform-toluene (1:1, v/v) was selected as the extraction solvent. Reliable results were obtained using dibenzo-30-crown-10-ether as an internal standard. The proposed method has been successfully applied for the determination of monensin in soil, surface water, and human urine spiked samples. Under the optimized conditions, the limits of quantification of the analyte in surface water, soil, and human urine were 6.7, 12.4 and 7.8 ng/mL, respectively. The intraday and interday precision variation and accuracy of the present method is within the acceptable ranges. The present method avoids the pre- and postderivatization of weak UV absorbing monensin determination using high performance liquid chromatography-ultraviolet detection (HPLC-UV). Furthermore, these techniques are time-consuming, nonreproducible at trace levels, and form undesirable products. The proposed SDME combined with AP-MALDI-MS is simple, fast, and selective for the determination of monensin in environmental and urine samples.

  6. A review of recent advances in the assessment of bone porosity, permeability, and interstitial fluid flow

    PubMed Central

    Cardoso, Luis; Fritton, Susannah P.; Gailani, Gaffar; Benalla, Mohammed; Cowin, Stephen C.

    2012-01-01

    This contribution reviews recent research performed to assess the porosity and permeability of bone tissue with the objective of understanding interstitial fluid movement. Bone tissue mechanotransduction is considered to occur due to the passage of interstitial pore fluid adjacent to dendritic cell structures in the lacunar-canalicular porosity. The movement of interstitial fluid is also necessary for the nutrition of osteocytes. This review will focus on four topics related to improved assessment of bone interstitial fluid flow. First, the advantages and limitations of imaging technologies to visualize bone porosities and architecture at several length scales are summarized. Second, recent efforts to measure the vascular porosity and lacunar-canalicular microarchitecture are discussed. Third, studies associated with the measurement and estimation of the fluid pressure and permeability in the vascular and lacunar-canalicular domains are summarized. Fourth, the development of recent models to represent the interchange of fluids between the bone porosities is described. PMID:23174418

  7. Rotating drops of axion dark matter

    NASA Astrophysics Data System (ADS)

    Davidson, Sacha; Schwetz, Thomas

    2016-06-01

    We consider how QCD axions produced by the misalignment mechanism could form galactic dark matter halos. We recall that stationary, gravitationally stable axion field configurations have the size of an asteroid with masses of order 10-13M⊙ (because gradient pressure is insufficient to support a larger object). We call such field configurations "drops." We explore whether rotating drops could be larger, and find that their mass could increase by a factor ˜10 . This mass is comparable to the mass of miniclusters generated from misalignment axions in the scenario where the axion is born after inflation. We speculate that misalignment axions today are in the form of drops, contributing to dark matter like a distribution of asteroids (and not as a coherent oscillating background field). We consider some observational signatures of the drops, which seem consistent with a galactic halo made of axion dark matter.

  8. Rain Drop Charge Sensor

    NASA Astrophysics Data System (ADS)

    S, Sreekanth T.

    begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge

  9. Liquid metal drop ejection

    NASA Technical Reports Server (NTRS)

    Khuri-Yakub, B. T.

    1993-01-01

    The aim of this project was to demonstrate the possibility of ejecting liquid metals using drop on demand printing technology. The plan was to make transducers for operation in the 100 MHz frequency range and to use these transducers to demonstrate the ability to eject drops of liquid metals such as gallium. Two transducers were made by indium bonding piezoelectric lithium niobate to quartz buffer rods. The lithium niobate plates were thinned by mechanical polishing to a thickness of 37 microns for operation at 100 MHz. Hemispherical lenses were polished in the opposite ends of the buffer rods. The lenses, which focus the sound waves in the liquid metal, had an F-number equals 1. A mechanical housing was made to hold the transducers and to allow precise control over the liquid level above the lens. We started by demonstrating the ability to eject drops of water on demand. The drops of water had a diameter of 15 microns which corresponds to the wavelength of the sound wave in the water. A videotape of this ejection was made. We then used a mixture of Gallium and Indium (used to lower the melting temperature of the Gallium) to demonstrate the ejection of liquid metal drops. This proved to be difficult because of the oxide skin which forms on the surface of the liquid. In some instances, we were able to eject metal drops, however, this was not consistent and reproducible. An experiment was set up at NASA-Lewis to stabilize the process of drop on demand liquid metal ejection. The object was to place the transducer and liquid metal in a vacuum station so that no oxide would form on the surface. We were successful in demonstrating that liquid metals could be ejected on demand and that this technology could be used for making sheet metal in space.

  10. Static shape of an acoustically levitated drop with wave-drop interaction

    NASA Astrophysics Data System (ADS)

    Lee, C. P.; Anilkumar, A. V.; Wang, T. G.

    1994-11-01

    The static shape of a drop levitated and flattened by an acoustic standing wave field in air is calculated, requiring self-consistency between the drop shape and the wave. The wave is calculated for a given shape using the boundary integral method. From the resulting radiation stress on the drop surface, the shape is determined by solving the Young-Laplace equation, completing an iteration cycle. The iteration is continued until both the shape and the wave converge. Of particular interest are the shapes of large drops that sustain equilibrium, beyond a certain degree of flattening, by becoming more flattened at a decreasing sound pressure level. The predictions for flattening versus acoustic radiation stress, for drops of different sizes, compare favorably with experimental data.

  11. Drying drops of blood

    NASA Astrophysics Data System (ADS)

    Brutin, David; Sobac, Benjamin; Loquet, Boris; Sampol, José.

    2010-11-01

    The drying of a drop of human blood is fascinating by the complexity of the physical mechanisms that occur as well as the beauty of the phenomenon which has never been previously evidenced in the literature. The final stage of full blood evaporation reveals for a healthy person the same regular pattern with a good reproducibility. Other tests on anemia and hyperlipidemic persons were performed and presented different patterns. By means of digital camera, the influence of the motion of red blood cells (RBCs) which represent about 50% of the blood volume, is revealed as well as its consequences on the final stages of drying. The mechanisms which lead to the final pattern of dried blood drops are presented and explained on the basis of fluid and solid mechanics in conjunction with the principles of hematology. Our group is the first to evidence that the specific regular patterns characteristic of a healthy individual do not appear in a dried drop of blood from a person with blood disease. Blood is a complex colloidal suspension for which the flow motion is clearly non-Newtonian. When drops of blood evaporate, all the colloids are carried by the flow motion inside the drop and interact.

  12. A modeling and numerical algorithm for thermoporomechanics in multiple porosity media for naturally fractured reservoirs

    NASA Astrophysics Data System (ADS)

    Kim, J.; Sonnenthal, E. L.; Rutqvist, J.

    2011-12-01

    TOUGHREACT coupled to ROCMECH (geomechanics simulator), and tested 1D and 2D small-scale problems. The numerical results show clear differences between the single and dual/multiple porosity systems. For example, the pressure in the fracture for the five-porosity model becomes higher than those for the single porosity system because the fracture bulk modulus is lower than the upscaled bulk modulus used in the single porosity. For elastoplasticity (the Mohr-Coulomb model), the pressure in the fracture can be supported by compaction when the fracture is in the plastic region. In a 2D case of the five-porosity system, we compare results of thermoporoelasticity with those of a conventional flow simulation using rock compressibility, and find significant differences between them. In conclusion, introducing multiple continuum concepts into geomechanical descriptions of fractured rock can provide more accurate models for coupled flow and geomechanics in fractured porous media.

  13. Reduction of Wake-Stator Interaction Noise Using Passive Porosity

    NASA Technical Reports Server (NTRS)

    Tinetti, Ana F.; Kelly, Jeffrey J.; Thomas, Russell H.; Bauer, Steven X. S.

    2002-01-01

    The present study was conducted to assess the potential of Passive Porosity Technology as a mechanism to reduce interaction noise in turbomachinery by reducing the fluctuating forces acting on the vane surfaces. To do so, a typical fan stator airfoil was subjected to the effects of a transversely moving wake; time histories of the primitive aerodynamic variables, obtained from Computational Fluid Dynamics (CFD) solutions, were then input into an acoustic prediction code. This procedure was performed on the solid airfoil to obtain a baseline, and on a series of porous configurations in order to isolate those that yield maximum noise reductions without compromising the aerodynamic performance of the stator. It was found that communication between regions of high pressure differential - made possible by the use of passive porosity - is necessary to significantly alter the noise radiation pattern of the stator airfoil. In general, noise reductions were obtained for those configurations incorporating passive porosity in the region between x/c is approximately 0.15 on the suction side of the airfoil and x/c is approximately 0.20 on the pressure side. Reductions in overall radiated noise of approximately 1.0 dB were obtained. The noise benefit increased to about 2.5 dB when the effects of loading noise alone were considered.

  14. How do drops evaporate?

    NASA Astrophysics Data System (ADS)

    Murisic, Nebojsa; Kondic, Lou

    2007-11-01

    The problem of evaporating drops with non-pinned contact line, although seemingly trivial, so far lacks satisfactory theoretical description. In particular, there has been much discussion regarding appropriate evaporative mass flux model. We make an attempt to resolve this issue by comparing our experimental data with the results of several mathematical models for evaporating drops. After describing experimental procedure, we propose several models for mass flux and develop a governing equation for evolution of drop's thickness. Two-dimensional numerical results are then compared to the experimental results, and the most appropriate mass flux model is identified. Finally, we propose the governing equation for the full 3D system and present some new numerical results related to curious phenomena, where so-called ``octopus-shaped'' instabilities appear ahead of the contact line of volatile dropsootnotetextY. Gotkis, I. Ivanov, N. Murisic, L. Kondic, Phys. Rev. Lett. 97, 186101 (2006)..

  15. Impact of surface porosity and topography on the mechanical behavior of high strength biomedical polymers.

    PubMed

    Evans, Nathan T; Irvin, Cameron W; Safranski, David L; Gall, Ken

    2016-06-01

    The ability to control the surface topography of orthopedic implant materials is desired to improve osseointegration but is often at the expense of mechanical performance in load bearing environments. Here we investigate the effects of surface modifications, roughness and porosity, on the mechanical properties of a set of polymers with diverse chemistry and structure. Both roughness and surface porosity resulted in samples with lower strength, failure strain and fatigue life due to stress concentrations at the surface; however, the decrease in ductility and fatigue strength were greater than the decrease in monotonic strength. The fatigue properties of the injection molded polymers did not correlate with yield strength as would be traditionally observed in metals. Rather, the fatigue properties and the capacity to maintain properties with the introduction of surface porosity correlated with the fracture toughness of the polymers. Polymer structure impacted the materials relative capacity to maintain monotonic and cyclic properties in the face of surface texture and porosity. Generally, amorphous polymers with large ratios of upper to lower yield points demonstrated a more significant drop in ductility and fatigue strength with the introduction of porosity compared to crystalline polymers with smaller ratios in their upper to lower yield strength. The latter materials have more effective dissipation mechanisms to minimize the impact of surface porosity on both monotonic and cyclic damage.

  16. Drum drop test report

    SciTech Connect

    McBeath, R.S.

    1995-02-28

    Testing was performed to determine actual damage to drums when dropped from higher than currently stacked elevations. The drum configurations were the same as they are placed in storage; single drums and four drums banded to a pallet. Maximum drop weights were selected based on successful preliminary tests. Material was lost from each of the single drum tests while only a small amount of material was lost from one of the pelletized drums. The test results are presented in this report. This report also provides recommendations for further testing to determine the appropriate drum weight which can be stored on a fourth tier.

  17. Permeability-Porosity Relationships in Deep Sea Hydrothermal Vent Deposits

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Gittings, H.; Tivey, M. K.

    2003-12-01

    To map out the thermal and chemical regimes within vent deposits where micro-and macro-organisms reside requires accurate modeling of mixing and reaction between hydrothermal fluid and seawater within the vent structures. However, a critical piece of information, quantitative knowledge of the permeability of vent deposits, and how it relates to porosity and pore geometry, is still missing. To address this, systematic laboratory measurements of permeability and porosity were conducted on 3 large vent structures from the Mothra Hydrothermal vent field on the Endeavor Segment of the Juan de Fuca Ridge. Twenty-five cylindrical cores with diameters of 2.54 cm and various lengths were taken from Phang (a tall sulfide-dominated spire that was not actively venting when sampled), Roane (a lower temperature spire with dense macrofaunal communities growing on its sides that was venting diffuse fluid of < 300° C) and Finn (an active black smoker with a well-defined inner conduit that was venting 302° C fluids prior to recovery (Delaney et al., 2000; Kelley et al, 2000)). Measurements were made to obtain porosity and permeability of these drill cores using a helium porosimeter (UltraPoreTM300) and a nitrogen permeameter (UltrapermTM400) from Core Laboratories Instruments. The porosimeter uses Boyle's law to determine pore volume from the expansion of a know mass of helium into a calibrated sample holder, whereas the permeameter uses Darcy's law to determine permeability by measuring the steady-state flow rate through the sample under a given pressure gradient. A moderate confining pressure of 1.38 MPa was applied during the measurements to prevent leakage between the sample surface and the sample holder. The permeability and porosity relationship is best described by two different power law relationships with exponents of ˜9 (group I) and ˜3 (group II), respectively. Microstructural observations suggest that the difference in the two permeability-porosity relationships

  18. Relationship between compressional-wave velocity and porosity of sediments along subduction plate interface

    NASA Astrophysics Data System (ADS)

    Yamaguchi, M.; Hashimoto, Y.

    2012-12-01

    Evolution of physical properties of sediments along subduction interface has effects on wedge strength, wedge geometry, dewatering and dehydration processes, and seismic behavior. Sediments have initially more than 70% of porosity prior to subduction. Through underthrusting and accretion, porosity of sediments decreases by compaction and cementation to be lithified sediments. The purpose of this study is to understand evolution of physical properties from a state before subduction to a state within a wedge using a relationship between compressional-wave velocity and porosity. In this study, we obtained new data for sediments from a reference site in IODP NanTroSEIZE, Expedition 333. In addition to that, we have complied velocity-porosity relationships for the samples and also for previous studies from NanTroSEIZE (off Kumano) (Hashimoto et al., 2010, 2011), ODP Leg 190 (off Shikoku) (Hoffman and Tobin, 2004) and ODP Leg 170 (off Costa Rica) (Gettemy and Tobin, 2003). Velocity measurement procedure in this study to obtain new data is as following: Two pumps were used to control pore fluid pressure and confining pressure. The pore pressure of 1000kPa was kept under drained conditions. Confining (effective) pressure was increased stepwise in the measurements. Velocity measurements were conducted under isotropic pressure conditions. Confining pressure was pressurized in tens seconds and kept for more than 8 hours for next step to obtain equilibrium conditions between effective pressure and sediments strain. Lead zirconate titanate (PZT) shear wave transducers (500kHz) were used in a source-receiver pair to measure wave speed. Porosity and P-wave velocity ranges about 27 - 75% and 1.4 - 2.2 km/s in this study, respectively. In the comparison in Vp-porosity relationships between sedimetns from reference sites and others, sediments were classified into two, simply compacted sediments (reference site and slope sediments) and wedge sediments. Different trends in Vp-porosity

  19. Airflows generated by an impacting drop.

    PubMed

    Bischofberger, Irmgard; Ray, Bahni; Morris, Jeffrey F; Lee, Taehun; Nagel, Sidney R

    2016-03-28

    A drop impacting a solid surface with sufficient velocity will splash and emit many small droplets. However, lowering the ambient air pressure suppresses splashing completely. This effect, robustly found for different liquid and substrate properties, raises the fundamental question of how air affects a spreading drop. In a combined experimental and numerical study we characterize the flow of air induced by the drop after it hits the substrate, using a modified Schlieren optics technique combined with high-speed video imaging and Lattice-Boltzmann simulations. Our experiments reveal the emergence of air structures on different length scales. On large scales, the airflow induced in the drop's wake leads to vortex structures due to interaction with the substrate. On smaller scales, we visualize a ring structure above the outer edge of the spreading liquid generated by the spreading of the drop. Our simulations reveal the interaction between the wake vorticity and the flows originating from the rapidly escaping air from below the impacting drop. We show that the vorticity is governed by a balance between inertial and viscous forces in the air, and is unrelated to the splashing threshold. PMID:26809314

  20. Airflows generated by an impacting drop.

    PubMed

    Bischofberger, Irmgard; Ray, Bahni; Morris, Jeffrey F; Lee, Taehun; Nagel, Sidney R

    2016-03-28

    A drop impacting a solid surface with sufficient velocity will splash and emit many small droplets. However, lowering the ambient air pressure suppresses splashing completely. This effect, robustly found for different liquid and substrate properties, raises the fundamental question of how air affects a spreading drop. In a combined experimental and numerical study we characterize the flow of air induced by the drop after it hits the substrate, using a modified Schlieren optics technique combined with high-speed video imaging and Lattice-Boltzmann simulations. Our experiments reveal the emergence of air structures on different length scales. On large scales, the airflow induced in the drop's wake leads to vortex structures due to interaction with the substrate. On smaller scales, we visualize a ring structure above the outer edge of the spreading liquid generated by the spreading of the drop. Our simulations reveal the interaction between the wake vorticity and the flows originating from the rapidly escaping air from below the impacting drop. We show that the vorticity is governed by a balance between inertial and viscous forces in the air, and is unrelated to the splashing threshold.

  1. Mathematical modeling to study influence of porosity on apple and potato during dehydration.

    PubMed

    Singh, Fateh; Katiyar, V K; Singh, B P

    2015-09-01

    Several structural and physical changes in foodstuffs are the consequence of water removal during the drying process. Porosity (volume fraction of pores) is one of the key parameter that affects the quality and other properties of foods (such as apple and potato). To understand the effect of dehydration in apple and potato, in the present study an arbitrary small cubic volume element is considered which contains pores (intracellular spaces) distributed in it. Further, it is assumed that each pore in the cubic volume element is spherical. A mathematical relation is developed between porosity (volume fraction of pores) and pressure generated (due to contraction of cells during water removal) in outward direction on the surface of spherical elements containing pore. The developed relation is satisfactory in respect of experimental observations given in the literature. For the given pressure range, acquired porosity range is 0.1 to 0.92 for apple and 0.03 to 0.89 for potato which is matched with the existing experimental values. The results showed that the porosity is increasing with the increasing values of pressure, as expected, during moisture removal. Further, it is observed that the current porosity is depended on the initial porosity for both apple and potato. PMID:26344960

  2. Effect of Porosity on Surface Catalytic Efficiency

    NASA Technical Reports Server (NTRS)

    Stewart, David A.; Pallix, Joan; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    This paper describes the effect of surface porosity of thermal protection materials on surface catalytic efficiency using test data taken from both arc-jet and side-arm reactor facilities. Relative surface porosity of the samples varied from 6% to 50%. Surface porosity was measured using a flow apparatus and Bernoulli equation. The surface catalytic efficiency of the materials was calculated using aerothermodynamic, and kinetic theories. The catalytic efficiency of the materials are compared at surface temperatures between room temperature and 2500 F. The data are presented in the form of graphs and tables.

  3. Method for determining effective reservoir porosity

    SciTech Connect

    Devries, M.R.; Fertl, W.H.

    1982-08-31

    A clay content curve, for the borehole under investigation is developed through logging procedures such as a gamma ray log or a spectral gamma ray log. Additionally, compaction trend curves based upon historic logging data are obtained for the geologic area of interest. Information provided by the total porosity trend curve is corrected using a function of the shaliness indicator curve. This correction allows the deviation of an effective porosity log for the reservoir which can be recorded or can be used to edit porosity logs.

  4. Acoustic forcing of a liquid drop

    NASA Technical Reports Server (NTRS)

    Lyell, M. J.

    1992-01-01

    The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

  5. Evolution of porosity in geotechnical composites.

    PubMed

    Tyrologou, Pavlos; Dudeney, Alvan William L; Grattoni, Carlos A

    2005-07-01

    Nuclear magnetic resonance (NMR) (H1) transverse relaxation measurements were carried out on 37x70-mm cylindrical mineral/organic composites to determine and monitor the porosity evolution. Porosity is related, in principle, to the stability of such materials in geotechnical applications, for example, engineering foundations. The specimens represented novel formulations of mixed "wastes" containing coarse screened mineral, digested sewage sludge, quicklime, and pulverized fuel ash mixed and compacted together to form mechanically competent material. The measurements on a selected formulation indicated initially low porosity (<12%) that becomes lower over 6 months ( approximately 8%) due to pozzolanic reactions occurring. A relaxation time cutoff of 1.5 ms between "bound" and 'mobile' pore water much lower than sandstones (33 ms) was observed. The results confirmed that the NMR method allows a more reliable assessment of porosity and pore-size evolution.

  6. Fabrication of dual porosity electrode structure

    DOEpatents

    Smith, J.L.; Kucera, E.H.

    1991-02-12

    A substantially entirely fibrous ceramic is described which may have dual porosity of both micro and macro pores. Total porosity may be 60-75% by volume. A method of spraying a slurry perpendicularly to an ambient stream of air is disclosed along with a method of removing binders without altering the fiber morphology. Adding fine ceramic particulates to the green ceramic fibers enhances the sintering characteristics of the fibers. 3 figures.

  7. Fabrication of dual porosity electrode structure

    DOEpatents

    Smith, James L.; Kucera, Eugenia H.

    1991-01-01

    A substantially entirely fibrous ceramic which may have dual porosity of both micro and macro pores. Total porosity may be 60-75% by volume. A method of spraying a slurry perpendicularly to an ambient stream of air is disclosed along with a method of removing binders without altering the fiber morphology. Adding fine ceramic particulates to the green ceramic fibers enhances the sintering characteristics of the fibers.

  8. Porosity prediction in sandstones using erosional unconformities

    SciTech Connect

    Shanmugam, G.

    1989-03-01

    Erosional unconformities of subaerial origin are created by tectonic uplifts and eustatic sea level fall. Most erosional unconformities developed on sandstones are planes of increased porosity because uplifted sandstones are exposed to undersaturated CO/sub 2/-charged meteoric waters that result in dissolution of unstable framework grains and cements. The chemical weathering of sandstones is intensified in humid regions by the heavy rainfall, soil zones, lush vegetation, and accompanying voluminous production of organic and inorganic acids. Erosional unconformities are considered hydrologically open systems because of abundant supply of fresh meteoric water and relatively unrestricted transport of dissolved constituents away from the site of dissolution, causing a net gain in porosity near unconformities. Thus, porosity in sandstones tends to increase toward overlying unconformities. Such porosity trends have been observed in hydrocarbon-bearing sandstone reservoirs in Alaska, Algeria, Australia, China, Libya, Netherlands, Norwegian North Sea, Norwegian Sea, and Texas. A common attribute of these reservoirs is that they were all subaerially exposed under heavy rainfall conditions. An empirical model has been developed for the Triassic and Jurassic sandstone reservoirs in the Norwegian North Sea on the basis of the observed relationship that shows an increase in porosity in these reservoirs with increasing proximity to the overlying base of Cretaceous unconformity. An important practical attribute of this model is that it allows for the prediction of porosity in the neighboring undrilled areas by recognizing the base of Cretaceous unconformity in seismic reflection profiles and by constructing subcrop maps.

  9. Numerical Simulations of Drop Collisions

    NASA Technical Reports Server (NTRS)

    Nobari, M. R. H.; Tryggvason, G.

    1994-01-01

    Three-dimensional simulations of the off-axis collisions of two drops are presented. The full Navier-Stokes equations are solved by a Front-Tracking/Finite-Difference method that allows a fully deformable fluid interface and the inclusion of surface tension. The drops are accelerated towards each other by a body force that is turned off before the drops collide. Depending on whether the interface between the drops is ruptured or not, the drops either bounce or coalesce. For drops that coalesce, the impact parameter, which measures how far the drops are off the symmetry line, determines the eventual outcome of the collision. For low impact parameters, the drops coalesce permanently, but for higher impact parameters, a grazing collision, where the drops coalesce and then stretch apart again is observed. The results are in agreement with experimental observations.

  10. Drop tube technical tasks

    NASA Technical Reports Server (NTRS)

    Workman, G. L.

    1986-01-01

    Criteria, using fundamental thermochemical dynamics, were developed to assist a scientist using the Drop Tube Facility in designing a good experiment. The types of parameters involved in designing the experiments include the type of furnace, the type of atmosphere, and in general which materials are better behaved than others as determined by past experience in the facility. One of the major advantages of the facility lies in its ability to provide large undercoolings in the cooling curve during the drops. A beginning was to consider the effect of oxygen and other gases upon the amount of undercooling observed. The starting point of the thermochemistry was given by Ellingham and later transformed into what is known as the Richardson Chart. The effect of surface oxidations upon the nucleation phenomena can be observed in each specimen.

  11. Encapsulating Ellipsoids in Drops

    NASA Astrophysics Data System (ADS)

    Norton, Michael; Brugarolas, Teresa; Chou, Jonathan; Bau, Haim; Lee, Daeyeon

    2012-11-01

    Large aspect ratio particles were produced by embedding spherical polystyrene particles within a polymer film and subsequently heating and stretching the film. Particles were released by dissolving the film. Using a flow-focusing device, the elongated particles were partially encapsulated within droplets of fluid A, such as water, surrounded by an immiscible fluid B, such as oil. Drop volumes were controlled by adjusting the flow rates of fluids A and B. The contact angle was adjusted indirectly by varying the amount of surfactant adsorbed to the particle surface. The encapsulation process was visualized with a high-speed video camera. We observed cases ranging from partial to complete encapsulation and examined experimentally and theoretically the shape of the interface between fluid A and fluid B as a function of the drop volume. The numerically predicted position of the pinning line and the shape of the drop were compared to experimentally produced conformations and agreed favorably. This work was supported by ITMAT (UL1RR024134 from the NCRR) and the Penn MRSEC (NSF DMR-1120901).

  12. Effects of pressure and temperature on the thermal properties of a salt and a quartz monzonite

    SciTech Connect

    Durham, W.B.; Abey, A.E.

    1981-03-27

    Measurements have been made of thermal conductivity, diffusivity, and linear expansion as a function of temperature (to 573 K) and hydrostatic pressure (to 50 MPa) on two rocks, Avery Island domal salt and Climax Stock quartz monzonite. For Avery Island salt the thermal properties do not show any pressure dependence and are approximately the same values as for single crystal halite at 0.1 MPa. The lack of pressure dependence is attributed to the high symmetry of halite (cubic) and to its low strength, both of which inhibit brittle fracturing. For Climax Stock quartz monzonite no pressure dependence of thermal diffusivity has been resolved, but conductivity does show a drop of approximately 10% with decreasing pressure from 50 to 3 MPa. The pressure dependence is not measurably altered by heating the rock to as high as 473 K under 50 MPa. Our measurements so far on the thermal conductivity of quartz monzonite vs temperature and pressure are in agreement with predictions of the Walsh and Decker (1966) model of thermal conductivity vs crack porosity based on independent measurements of crack porosity vs temperature and pressure for the same quartz monzonite. Heating to temperatures greater than 473 K at 50 MPa, or heating to lower temperatures at lower pressures, should substantially reduce thermal conductivity of the quart monzonite.

  13. Glaucoma eye drops adverse skin reactions.

    PubMed

    Cantisani, Carmen; Ambrifi, Marina; Frascani, Federica; Fazia, Gilda; Paolino, Giovanni; Lisi, Roberto; Calvieri, Stefano

    2014-01-01

    The term "Glaucoma" is used to describe a number of diseases of the eye characterized by a particular form of optic nerve damage that is often associated with high intraocular pressure (IOP). The open-angle glaucoma is the most common form that is also referred to as chronic glaucoma. This is described as an optic neuropathy with multifactorial nature in which there is a loss of characteristics of the optic nerve fibers. Therapeutic options for the treatment of this disease are different, you can take advantage of eye drops, laser therapy and conventional surgery or more combined treatments. Medicated eye drops are the most common way to treat glaucoma. Although eye drops are widely used, adverse reactions are not frequently observed and described. In particular, the adverse skin reactions are not frequently described in the literature, but often seen in dermatologic clinic, we reported their skin reactions and possible alternative treatments described in literature and their patent applications. PMID:25487259

  14. Condensation Enhancement by Surface Porosity: Three-Stage Mechanism.

    PubMed

    Yarom, Michal; Marmur, Abraham

    2015-08-18

    Surface defects, such as pores, cracks, and scratches, are naturally occurring and commonly found on solid surfaces. However, the mechanism by which such imperfections promote condensation has not been fully explored. In the current paper we thermodynamically analyze the ability of surface porosity to enhance condensation on a hydrophilic solid. We show that the presence of a surface-embedded pore brings about three distinct stages of condensation. The first is capillary condensation inside the pore until it is full. This provides an ideal hydrophilic surface for continuing the condensation. As a result, spontaneous condensation and wetting can be achieved at lower vapor pressure than on a smooth surface.

  15. The new Drop Tower catapult system

    NASA Astrophysics Data System (ADS)

    von Kampen, Peter; Kaczmarczik, Ulrich; Rath, Hans J.

    2006-07-01

    The Center of Applied Space Technology and Microgravity (ZARM) was founded in 1985 as an institute of the University Bremen, which focuses on research on gravitational and space-related phenomena. In 1988, the construction of the "Drop Tower" began. Since then, the eye-catching tower with a height of 146 m and its characteristic glass roof has become the emblem of the technology centre in Bremen. The Drop Tower Bremen provides a facility for experiments under conditions of weightlessness. Items are considered weightless, when they are in "free fall", i.e. moving without propulsion within the gravity field of the earth. The height of the tower limits the simple "free fall" experiment period to max. 4.74 s. With the inauguration of the catapult system in December 2004, the ZARM is entering a new dimension. This world novelty will meet scientists' demands of extending the experiment period up to 9.5 s. Since turning the first sod on May 3rd, 1988, the later installation of the catapult system has been taken into account by building the necessary chamber under the tower. The catapult system is located in a chamber 10 m below the base of the tower. This chamber is almost completely occupied by 12 huge pressure tanks. These tanks are placed around the elongation of the vacuum chamber of the drop tube. In its centre there is the pneumatic piston that accelerates the drop capsule by the pressure difference between the vacuum inside the drop tube and the pressure inside the tanks. The acceleration level is adjusted by means of a servo hydraulic breaking system controlling the piston velocity. After only a quarter of a second the drop capsule achieves its lift-off speed of 175 km/h. With this exact speed, the capsule will rise up to the top of the tower and afterwards fall down again into the deceleration unit which has been moved under the drop tube in the meantime. The scientific advantages of the doubled experiment time are obvious: during almost 10 s of high

  16. The effect of porosity on the mechanical properties of cordierite diesel particulate filter substrates

    SciTech Connect

    Shyam, Amit; Lara-Curzio, Edgar; Watkins, Thomas R

    2009-01-01

    Diesel particulate filter (DPF) technology depends on porous ceramic structures that trap the particulate matter in the diesel engine exhaust gas stream. The design of DPFs requires balancing the functional requirement of soot filtration with the mechanical properties and both are influenced by the porosity of the substrate. In addition, increasing the porosity of the substrate can assist with the catalytic washcoating, engine back pressure and engine efficiency. The effect of porosity on the elastic and fracture mechanical properties of cordierite based ceramic particulate filters was examined and will be described. Elastic modulus of DPF substrates was determined using resonant ultrasound spectroscopy while fracture toughness was characterized using the double-torsion test method. The interrelationships among specimen thickness, wall orientation, porosity and mechanical properties of the filter substrates will be discussed. A materials selection procedure to obtain filters with high thermal shock resistance and optimal mechanical properties will be described.

  17. Tuning the porosity of zinc oxide electrodes: from dense to nanopillar films

    NASA Astrophysics Data System (ADS)

    Fanni, Lorenzo; Delaup, Benoît; Niesen, Bjoern; Milstein, Yonat; Shachal, Dubi; Morales-Masis, Monica; Nicolay, Sylvain; Ballif, Christophe

    2015-07-01

    Thin films with tunable porosity are of high interest in applications such as gas sensing and antireflective coatings. We report a facile and scalable method to fabricate ZnO electrodes with tuneable porosity. By adjusting the substrate temperature and ratio of precursor gasses during low-pressure chemical vapor deposition we can accurately tune the porosity of ZnO films, from 0 up to 24%. The porosity change of the films from dense layer to separated nanopillars results in an effective refractive index reduction from 1.9 to 1.65 at 550 nm, as determined by optical and x-ray spectroscopy. The low-refractive-index ZnO films are incorporated into amorphous silicon solar cells demonstrating reflection losses reduction down to 4% in the visible wavelengths range.

  18. Measurement of intergranular stress and porosity during dynamic compaction of porous beds of cyclotetramethylene tetranitramine

    NASA Astrophysics Data System (ADS)

    Greenaway, M. W.

    2005-05-01

    The dynamic compaction of granular beds of the propellant cyclotetramethylene tetranitramine (HMX) has been investigated using a modified split Hopkinson pressure bar system. Intergranular stress and bed porosity were simultaneously measured during controlled loading. The importance of grain size was investigated by comparing conventional HMX (mean particle size ˜260μm) to microfine HMX (<5μm). Samples were radially confined and compression was predetermined using special end caps. Initial porosity was varied by hydraulically pressing the beds prior to testing. With large grains, resistance to compaction increased with the solid volume fraction. Microfine HMX behaved like low porosity conventional HMX beds in all cases. Porosity was typically reduced by 5%-10% during compaction and intergranular stresses below the yield stress were ensured. Energy dissipation to plastic flow and fracture were largely eliminated. Optical particle size analysis and electron microscopy support the experimental observations.

  19. Drop Testing Representative Multi-Canister Overpacks

    SciTech Connect

    Snow, Spencer D.; Morton, Dana K.

    2015-06-01

    The objective of the work reported herein was to determine the ability of the Multi- Canister Overpack (MCO) canister design to maintain its containment boundary after an accidental drop event. Two test MCO canisters were assembled at Hanford, prepared for testing at the Idaho National Engineering and Environmental Laboratory (INEEL), drop tested at Sandia National Laboratories, and evaluated back at the INEEL. In addition to the actual testing efforts, finite element plastic analysis techniques were used to make both pre-test and post-test predictions of the test MCOs structural deformations. The completed effort has demonstrated that the canister design is capable of maintaining a 50 psig pressure boundary after drop testing. Based on helium leak testing methods, one test MCO was determined to have a leakage rate not greater than 1x10-5 std cc/sec (prior internal helium presence prevented a more rigorous test) and the remaining test MCO had a measured leakage rate less than 1x10-7 std cc/sec (i.e., a leaktight containment) after the drop test. The effort has also demonstrated the capability of finite element methods using plastic analysis techniques to accurately predict the structural deformations of canisters subjected to an accidental drop event.

  20. Effects of Passive Porosity on Interacting Vortex Flows At Supersonic Speeds

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.

    2000-01-01

    A wind tunnel experiment was conducted in the NASA Langley Research Center (LaRC) Unitary Plan Wind Tunnel (UPWT) to determine the effects of passive surface porosity on vortex flow interaction about a general research fighter configuration at supersonic speeds. Optical flow measurement and flow visualization techniques were used and included pressure-sensitive paint (PSP), schlieren, and laser vapor screen (LVS) These techniques were combined with force and moment and conventional electronically-scanned pressure (ESP) measurements to quantify and to visualize the effects of flow-through porosity applied to a wing leading-edge extension (LEX) mounted to a 65 deg cropped delta wing model.

  1. SALTSTONE VARIABILITY STUDY - MEASUREMENT OF POROSITY

    SciTech Connect

    Harbour, J; Vickie Williams, V; Tommy Edwards, T; Russell Eibling, R; Ray Schumacher, R

    2007-08-23

    One of the goals of the Saltstone Variability Study is to identify the operational and compositional variables that control or influence the important processing and performance properties of Saltstone mixes. One of the key performance properties is porosity which is a measure of the volume percent of a cured grout that is occupied by salt solution (for the saturated case). This report presents (1) the results of efforts to develop a method for the measurement of porosity of grout samples and (2) initial results of porosity values for samples that have been previously produced as part of the Saltstone Variability Study. A cost effective measurement method for porosity was developed that provides reproducible results, is relatively fast (30 to 60 minutes per sample) and uses a Mettler Toledo HR83 Moisture Analyzer that is already operational and routinely calibrated at Aiken County Technology Laboratory. The method involves the heating of the sample at 105 C until no further mass loss is observed. This mass loss value, which is due to water evaporation, is then used to calculate the volume percent porosity of the mix. The results of mass loss for mixes at 105 C were equivalent to the results obtained using thermal gravimetric analysis. The method was validated by comparing measurements of mass loss at 105 C for cured portland cement in water mixes to values presented in the literature for this system. A stereopycnometer from Quantachrome Instruments was selected to measure the cured grout bulk densities. Density is a property that is required to calculate the porosities. A stereopycnometer was already operational at Aiken County Technology Laboratory, has been calibrated using a solid stainless steel sphere of known volume, is cost effective and fast ({approx}15 minutes per sample). Cured grout densities are important in their own right because they can be used to project the volume of waste form produced from a given amount of salt feed of known composition. For

  2. Drop foot corrective device

    NASA Technical Reports Server (NTRS)

    Deis, B. C. (Inventor)

    1986-01-01

    A light weight, economical device to alleviate a plurality of difficulties encountered in walking by a victim suffering from a drop foot condition is discussed. A legband girdles the leg below the knee and above the calf providing an anchor point for the upper end of a ligament having its lower end attached to a toe of a shoe or a toe on the foot. The ligament is of such length that the foot is supported thereby and retained in a normal position during walking.

  3. High=porosity Cenozoic carbonate rocks of South Florida: progressive loss of porosity with depth

    USGS Publications Warehouse

    Halley, Robert B.; Schmoker, James W.

    1983-01-01

    Porosity measurements by borehole gravity meter in subsurface Cenozoic carbonates of South Florida reveal an extremely porous mass of limestone and dolomite which is transitional in total pore volume between typical porosity values for modern carbonate sediments and ancient carbonate rocks. A persistent decrease of porosity with depth, similar to that of chalks of the Gulf Coast, occurs in these rocks. Carbonate strata with less than 20% porosity are absent from the rocks studied here. Aquifers and aquicludes cannot be distinguished on the basis of porosity. Aquifers are not exceptionally porous when compared to other Tertiary carbonate rocks in South Florida. Permeability in these strata is governed more by the spacial distribution of pore space and matrix than by total volume of porosity present. Dolomite is as porous as, or slightly less porous than, limestones in these rocks. This observation places limits on any model proposed for dolomitization and suggests that dolomitization does not take place by a simple ion-for-ion replacement of magnesium for calcium. Dolomitization may be selective for less porous limestone, or it may involve the incorporation of significant amounts of carbonate as well as magnesium into the rock. The great volume of pore space in these rocks serves to highlight the inefficiency of early diagenesis in reducing carbonate porosity and to emphasize the importance of later porosity reduction which occurs during the burial or late near-surface history of limestones and dolomites.

  4. Empirical relation between carbonate porosity and thermal maturity: an approach to regional porosity prediction.

    USGS Publications Warehouse

    Schmoker, J.W.

    1984-01-01

    Carbonate porosity can be predicted approximately on a regional scale as a function of thermal maturity. Thus: theta = a (TTI) b, where theta = regional porosity, a = a constant for a given region and varies by an order of magnitude, TTI = Lopatin's time-T index of thermal maturity and b approx -0.372. -K.A.R.

  5. Low blood pressure

    MedlinePlus

    Hypotension; Blood pressure - low; Postprandial hypotension; Orthostatic hypotension; Neurally mediated hypotension; NMH ... Blood pressure varies from one person to another. A drop as little as 20 mmHg, can cause problems for ...

  6. Graded-porosity heat-pipe wicks

    NASA Technical Reports Server (NTRS)

    Eninger, J. E.

    1976-01-01

    To maximize the capacity of a nonarterial heat pipe, a wick is considered whose porosity is allowed to vary axially along its length. At every axial location the porosity is set no lower than required to maintain the wick in a nearly saturated state under the maximum heat-transport rate. The result is a wick whose permeability is everywhere as high as possible. The differential equation that governs the optimum porosity variation is solved numerically between a condenser-end boundary condition that just prevents a liquid slug or puddle in the vapor spaces and an evaporator-end boundary condition that just prevents circumferential groove dry-up. Experimental performance measurements for an ammonia heat pipe are presented.

  7. Coalescence of Liquid Drops

    NASA Technical Reports Server (NTRS)

    Yao, Wei-Jun

    2003-01-01

    When two liquid drops come into contact, a neck forms between them and grows rapidly. We are interested in the very early stage of the coalescence process, which can be characterized by the time dependence of the radius of the neck. The functional dependence of the size of the neck on time depends on the properties of the liquid. Experimentally, we are investigating a liquid in Stokes flow regime where the viscosity provides the principal retarding force to the surface tension. Recently, it has been predicted that the neck radius should change as t ln|t| in this regime. Theoretically, we have studied the situation when the velocity at each point on the surface is proportional to the local curvature and directed normal to the surface. This is the case that should be applicable to superfluid helium at low temperature when the mean free path of the thermal excitations are comparable to the size of liquid drops. For this system, the radius of the neck is found to be proportional to t(sup 1/3). We are able to find a simple expression for the shape of the interface in the vicinity of the neck.

  8. Packing Bunker and Pile Silos to Minimize Porosity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This article discusses the issue of porosity (i.e., the portion of volume filled with gas) in silages. As porosity increases, the silage is subject to greater losses. Porosity can be reduced by adequately packing the crop at ensiling. To keep porosity below 40% a minimum bulk density of 44 lbs./cu. ...

  9. Automated single cell sorting and deposition in submicroliter drops

    NASA Astrophysics Data System (ADS)

    Salánki, Rita; Gerecsei, Tamás; Orgovan, Norbert; Sándor, Noémi; Péter, Beatrix; Bajtay, Zsuzsa; Erdei, Anna; Horvath, Robert; Szabó, Bálint

    2014-08-01

    Automated manipulation and sorting of single cells are challenging, when intact cells are needed for further investigations, e.g., RNA or DNA sequencing. We applied a computer controlled micropipette on a microscope admitting 80 PCR (Polymerase Chain Reaction) tubes to be filled with single cells in a cycle. Due to the Laplace pressure, fluid starts to flow out from the micropipette only above a critical pressure preventing the precise control of drop volume in the submicroliter range. We found an anomalous pressure additive to the Laplace pressure that we attribute to the evaporation of the drop. We have overcome the problem of the critical dropping pressure with sequentially operated fast fluidic valves timed with a millisecond precision. Minimum drop volume was 0.4-0.7 μl with a sorting speed of 15-20 s per cell. After picking NE-4C neuroectodermal mouse stem cells and human primary monocytes from a standard plastic Petri dish we could gently deposit single cells inside tiny drops. 94 ± 3% and 54 ± 7% of the deposited drops contained single cells for NE-4C and monocytes, respectively. 7.5 ± 4% of the drops contained multiple cells in case of monocytes. Remaining drops were empty. Number of cells deposited in a drop could be documented by imaging the Petri dish before and after sorting. We tuned the adhesion force of cells to make the manipulation successful without the application of microstructures for trapping cells on the surface. We propose that our straightforward and flexible setup opens an avenue for single cell isolation, critically needed for the rapidly growing field of single cell biology.

  10. Controlled porosity solubility modulated osmotic pump tablets of gliclazide.

    PubMed

    Banerjee, Arti; Verma, P R P; Gore, Subhash

    2015-06-01

    A system that can deliver drug at a controlled rate is very important for the treatment of various chronic diseases such as diabetes, asthma, and heart disease. Poorly water-soluble drug with pH-dependent solubility such as gliclazide (GLZ) offers challenges in the controlled-release formulation because of low dissolution rate and poor bioavailability. Solid dispersion (SD) of GLZ consisted of hydroxypropyl cellulose (HPC-SSL) as a polymeric solubilizer was manufactured by hot melt extrusion (HME) technology. Then, controlled porosity osmotic pump (CPOP) tablet of gliclazide was designed to deliver drug in a controlled manner up to 16 h. The developed formulation was optimized for type and level of pore former and coating weight gain. The optimized formulation was found to exhibit zero order kinetics independent of pH and agitation speed but depends on osmotic pressure of dissolution media indicated that mechanism of drug release was osmotic pressure. The in vivo performance prediction of developed formulation using convolution approach revealed that the developed formulation was superior to the existing marketed extended-release formulation in terms of attaining steady state plasma levels and indicated adequate exposure in translating hypoglycemic response. The prototype solubilization method combined with controlled porosity osmotic pump based technique could provide a unique way to increase dissolution rate and bioavailability of many poorly water-soluble, narrow therapeutic index drugs used in diabetes, cardiovascular diseases, etc.

  11. Mechanically-Excited Sessile Drops

    NASA Astrophysics Data System (ADS)

    Chang, Chun-Ti; Bostwick, Joshua; Daniel, Susan; Steen, Paul

    2010-11-01

    The volume and contact-line mobility of a sessile drop determine the frequency response of the drop to mechanical excitation. A useful signature of the drop is its response to a sweep of frequency. At particular frequencies the drop exhibits standing wave patterns of different mode numbers and/or azimuthal, spinning motion. We report observations of the spectrum of standing wave patterns and compare to predictions of a linear stability theory. On the side of application, the results suggest how to tune the pinning-unpinning of a sessile drop in order to maximize its translation.

  12. Multiphase flow of carbon dioxide and brine in dual porosity carbonates

    NASA Astrophysics Data System (ADS)

    Pentland, Christopher; Oedai, Sjaam; Ott, Holger

    2014-05-01

    The storage of carbon dioxide in subsurface formations presents a challenge in terms of multiphase flow characterisation. Project planning requires an understanding of multiphase flow characteristics such as the relationship between relative permeability and saturation. At present there are only a limited number of relative permeability relations for carbon dioxide-brine fluid systems, most of which are measured on sandstone rocks. In this study coreflood experiments are performed to investigate the relative permeability of carbon dioxide and brine in two dual porosity carbonate systems. Carbon dioxide is injected into the brine saturated rocks in a primary drainage process. The rock fluid system is pre-equilibrated to avoid chemical reactions and physical mass transfer between phases. The pressure drop across the samples, the amount of brine displaced and the saturation distribution within the rocks are measured. The experiments are repeated on the same rocks for the decane-brine fluid system. The experimental data is interpreted by simulating the experiments with a continuum scale Darcy solver. Selected functional representations of relative permeability are investigated, the parameters of which are chosen such that a least squares objective function is minimised (i.e. the difference between experimental observations and simulated response). The match between simulation and measurement is dependent upon the form of the functional representations. The best agreement is achieved with the Corey [Brooks and Corey, 1964] or modified Corey [Masalmeh et al., 2007] functions which best represent the relative permeability of brine at low brine saturations. The relative permeability of carbon dioxide is shown to be lower than the relative permeability of decane over the saturation ranges investigated. The relative permeability of the brine phase is comparable for the two fluid systems. These observations are consistent with the rocks being water-wet. During the experiment

  13. Permeability-porosity relationships in sedimentary rocks

    USGS Publications Warehouse

    Nelson, Philip H.

    1994-01-01

    In many consolidated sandstone and carbonate formations, plots of core data show that the logarithm of permeability (k) is often linearly proportional to porosity (??). The slope, intercept, and degree of scatter of these log(k)-?? trends vary from formation to formation, and these variations are attributed to differences in initial grain size and sorting, diagenetic history, and compaction history. In unconsolidated sands, better sorting systematically increases both permeability and porosity. In sands and sandstones, an increase in gravel and coarse grain size content causes k to increase even while decreasing ??. Diagenetic minerals in the pore space of sandstones, such as cement and some clay types, tend to decrease log(k) proportionately as ?? decreases. Models to predict permeability from porosity and other measurable rock parameters fall into three classes based on either grain, surface area, or pore dimension considerations. (Models that directly incorporate well log measurements but have no particular theoretical underpinnings from a fourth class.) Grain-based models show permeability proportional to the square of grain size times porosity raised to (roughly) the fifth power, with grain sorting as an additional parameter. Surface-area models show permeability proportional to the inverse square of pore surface area times porosity raised to (roughly) the fourth power; measures of surface area include irreducible water saturation and nuclear magnetic resonance. Pore-dimension models show permeability proportional to the square of a pore dimension times porosity raised to a power of (roughly) two and produce curves of constant pore size that transgress the linear data trends on a log(k)-?? plot. The pore dimension is obtained from mercury injection measurements and is interpreted as the pore opening size of some interconnected fraction of the pore system. The linear log(k)-?? data trends cut the curves of constant pore size from the pore-dimension models

  14. The effect of GASAR processing parameters on porosity and properties in aluminum alloy

    SciTech Connect

    Paradies, C.J.; Tobin, A.; Wolla, J.

    1998-12-31

    The GASAR process involves the dissolution of hydrogen in a molten metal or alloy by controlling the hydrogen pressure and the temperature in a high pressure chamber. The difference between the hydrogen solubility in the melt and the solid is used to control the growth of hydrogen pores within the solidifying structure. Designed experiments have been performed to determine the relative effects of the saturation pressure, temperature, casting pressure, mold temperature and cooling rate on the total porosity, pore size, distribution and shape in pure nickel and aluminum alloys. The shape and distribution of pores was found to depend upon the structure of the primary solid pore nucleation and growth. Reducing the casting pressure had the strongest effect on increasing the total porosity and pore size.

  15. Controlling charge on levitating drops.

    PubMed

    Hilger, Ryan T; Westphall, Michael S; Smith, Lloyd M

    2007-08-01

    Levitation technologies are used in containerless processing of materials, as microscale manipulators and reactors, and in the study of single drops and particles. Presented here is a method for controlling the amount and polarity of charge on a levitating drop. The method uses single-axis acoustic levitation to trap and levitate a single, initially neutral drop with a diameter between 400 microm and 2 mm. This drop is then charged in a controllable manner using discrete packets of charge in the form of charged drops produced by a piezoelectric drop-on-demand dispenser equipped with a charging electrode. The magnitude of the charge on the dispensed drops can be adjusted by varying the voltage applied to the charging electrode. The polarity of the charge on the added drops can be changed allowing removal of charge from the trapped drop (by neutralization) and polarity reversal. The maximum amount of added charge is limited by repulsion of like charges between the drops in the trap. This charging scheme can aid in micromanipulation and the study of charged drops and particles using levitation. PMID:17580951

  16. Electrical properties of geothermal reservoir rocks as indicators of porosity distribution

    SciTech Connect

    Duba, A.; Roberts, J.; Bonner, B.

    1997-03-01

    Measurements of the electrical resistivity of metashales from borehole SB-15-D in The Geyers geothermal area at a variety of conditions in the laboratory provide information regarding the distribution of porosity as interpreted from observations of boiling as downstream pore pressure. Electrical resistivity measurements on core,with and without pore pressure control, to confining pressures up to 100 bars and temperatures between 20 and 150 C allow assessment of the separate and combined effects of confining pressure, pore pressure and temperature for rocks from this borehole.

  17. [The abdominal drop flap].

    PubMed

    Bodin, F; Liverneaux, P; Seigle-Murandi, F; Facca, S; Bruant-Rodier, C; Dissaux, C; Chaput, B

    2015-08-01

    The skin between the mastectomy scar and the future infra-mammary fold may be managed in different ways in delayed breast reconstruction using a DIEP (deep inferior epigastric perforator). Conserving this skin and positioning the flap skin paddle in the middle of the breast usually highlights skin color disparity because of two visible transition zones. Resection of the entire skin under the scar may be more aesthetic but limits direct closure possibility in case of flap failure. In order to benefit from both aesthetic result and safe surgical method, we propose the abdominal drop flap. The inferior thoracic skin flap is detached from the thoracic wall beyond the future infra-mammary fold, preserved and pushed under the breast.

  18. Reduction of porosity in aluminum weldments

    NASA Technical Reports Server (NTRS)

    Lee, W. S.

    1972-01-01

    Method is described for elimination of porosity of aluminum weldments by replacing polyvinyl chloride tubing (used to connect welder to gas source, and is permeable to moisture at high humidity) with copper tubing. In addition liquid argon gas is used at weld stations.

  19. Porosity Log Prediction Using Artificial Neural Network

    NASA Astrophysics Data System (ADS)

    Dwi Saputro, Oki; Lazuardi Maulana, Zulfikar; Dzar Eljabbar Latief, Fourier

    2016-08-01

    Well logging is important in oil and gas exploration. Many physical parameters of reservoir is derived from well logging measurement. Geophysicists often use well logging to obtain reservoir properties such as porosity, water saturation and permeability. Most of the time, the measurement of the reservoir properties are considered expensive. One of method to substitute the measurement is by conducting a prediction using artificial neural network. In this paper, artificial neural network is performed to predict porosity log data from other log data. Three well from ‘yy’ field are used to conduct the prediction experiment. The log data are sonic, gamma ray, and porosity log. One of three well is used as training data for the artificial neural network which employ the Levenberg-Marquardt Backpropagation algorithm. Through several trials, we devise that the most optimal input training is sonic log data and gamma ray log data with 10 hidden layer. The prediction result in well 1 has correlation of 0.92 and mean squared error of 5.67 x10-4. Trained network apply to other well data. The result show that correlation in well 2 and well 3 is 0.872 and 0.9077 respectively. Mean squared error in well 2 and well 3 is 11 x 10-4 and 9.539 x 10-4. From the result we can conclude that sonic log and gamma ray log could be good combination for predicting porosity with neural network.

  20. Coatings with controlled porosity and chemical properties

    DOEpatents

    Frye, G.C.; Brinker, C.J.; Doughty, D.H.; Bein, T.; Moller, K.

    1993-07-06

    Coatings and sensors are described having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided.

  1. Coatings with controlled porosity and chemical properties

    DOEpatents

    Frye, Gregory C.; Brinker, C. Jeffrey; Doughty, Daniel H.; Bein, Thomas; Moller, Karin

    1993-01-01

    Coatings and sensors having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided.

  2. Coatings with controlled porosity and chemical properties

    DOEpatents

    Frye, Gregory C.; Brinker, C. Jeffrey; Doughty, Daniel H.; Bein, Thomas; Moller, Karin

    1996-01-01

    Coatings and sensors having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided.

  3. Coatings with controlled porosity and chemical properties

    DOEpatents

    Frye, G.C.; Brinker, C.J.; Doughty, D.H.; Bein, T.; Moller, K.

    1996-12-31

    Coatings and sensors are disclosed having both steric and chemical selectivity. Controlled porosity provides the steric selectivity, whereas chemically tailored film properties, using controlled composition or modification by coupling agents, chemical species replacement, or chemical species within pores, provide the chemical selectivity. Single or multiple layers may be provided. 7 figs.

  4. Determination of Meteorite Porosity Using Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    Kohout, T.; Kletetschka, G.; Pesonen, L. J.; Wasilewski, P. J.

    2005-01-01

    We introduce a new harmless method for porosity measurement suitable for meteorite samples. The method is a modification of the traditional Archimedean method based on immersion of the samples in a liquid medium like water or organic liquids. In our case we used liquid nitrogen for its chemically inert characteristics.

  5. Trapped liquid drop at the end of capillary.

    PubMed

    Wang, Zhengjia; Yen, Hung-Yu; Chang, Cheng-Chung; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2013-10-01

    The liquid drop captured at the capillary end, which is observed in capillary valve and pendant drop technique, is investigated theoretically and experimentally. Because of contact line pinning of the lower meniscus, the lower contact angle is able to rise from the intrinsic contact angle (θ*) so that the external force acting on the drop can be balanced by the capillary force. In the absence of contact angle hysteresis (CAH), the upper contact angle remains at θ*. However, in the presence of CAH, the upper contact angle can descend to provide more capillary force. The coupling between the lower and upper contact angles determines the equilibrium shape of the captured drop. In a capillary valve, the pinned contact line can move across the edge as the pressure difference exceeds the valving pressure, which depends on the geometrical characteristic and wetting property of the valve opening. When CAH is considered, the valving pressure is elevated because the capillary force is enhanced by the receding contact angle. For a pendant drop under gravity, the maximal capillary force is achieved as the lower contact angle reaches 180° in the absence of CAH. However, in the presence of CAH, four regimes can be identified by three critical drop volumes. The lower contact angle can exceed 180°, and therefore the drop takes on the shape of a light bulb, which does not exist in the absence of CAH. The comparisons between Surface Evolver simulations and experiments are quite well. PMID:24004041

  6. A simple procedure for estimating soil porosity

    NASA Astrophysics Data System (ADS)

    Emmet-Booth, Jeremy; Forristal, Dermot; Fenton, Owen; Holden, Nick

    2016-04-01

    Soil degradation from mismanagement is of international concern. Simple, accessible tools for rapidly assessing impacts of soil management are required. Soil structure is a key component of soil quality and porosity is a useful indicator of structure. We outline a version of a procedure described by Piwowarczyk et al. (2011) used to estimate porosity of samples taken during a soil quality survey of 38 sites across Ireland as part of the Government funded SQUARE (Soil Quality Assessment Research) project. This required intact core (r = 2.5 cm, H = 5cm) samples taken at 5-10 cm and 10-20 cm depth, to be covered with muslin cloth at one end and secured with a jubilee clip. Samples were saturated in sealable water tanks for ≈ 64 hours, then allowed to drain by gravity for 24 hours, at which point Field Capacity (F.C.) was assumed to have been reached, followed by oven drying with weight determined at each stage. This allowed the calculation of bulk density and the estimation of water content at saturation and following gravitational drainage, thus total and functional porosity. The assumption that F.C. was reached following 24 hours of gravitational drainage was based on the Soil Moisture Deficit model used in Ireland to predict when soils are potentially vulnerable to structural damage and used nationally as a management tool. Preliminary results indicate moderately strong, negative correlations between estimated total porosity at 5-10 cm and 10-20 cm depth (rs = -0.7, P < 0.01 in both cases) and soil quality scores of the Visual Evaluation of Soil Structure (VESS) method which was conducted at each survey site. Estimated functional porosity at 5-10 cm depth was found to moderately, negatively correlate with VESS scores (rs = - 0.5, P < 0.05). This simple procedure requires inexpensive equipment and appears useful in indicating porosity of a large quantity of samples taken at numerous sites or if done periodically, temporal changes in porosity at a field scale

  7. Seismic velocities in unconsolidated sands: Measurements of pressure, sorting, and compaction effects

    NASA Astrophysics Data System (ADS)

    Zimmer, Michael Andrew

    This dissertation presents measurements of compressional- and shear-wave velocities made on unconsolidated sand and glass-bead samples over a pressure range from 100 kPa to 20 MPa. These measurements demonstrate that the shear-wave velocity varies with the fourth root of the effective pressure over the entire pressure range, while the compressional-wave velocity demonstrates a slightly lower pressure dependence. These pressure dependences show no systematic variation with the porosity for porosities from 25 to 44%. The porosity-velocity trend at a given pressure is described by the isostress average between the moduli of the highest porosity sample and the moduli of quartz. The significant porosity dependence of the water-saturated, compressional-wave velocities, as modeled with Gassmann fluid substitution, is mostly contained in the zero-pressure bulk modulus. Preconsolidation produces only a slight increase in the velocities and a slight reduction in the pressure dependence. A comparison of the velocities measured at 150 kHz in water-saturated samples of four natural sands to velocities predicted by Biot and Mavko-Jizba models demonstrates that the squirt mechanism is the primary dispersion mechanism active in these sands at this frequency. The dispersion in the velocities demonstrates no significant change with compaction. The static bulk modulus calculated from the volumetric strains observed in the dry samples of these four natural sands and one glass bead sample is shown to be from 2 to 10 times lower than the dynamic bulk modulus for the normally consolidated samples, and drops from being equal to the dynamic modulus on the first unloading step to being approximately 3 times lower on complete unloading. A Preisach-Mayergoyz space analysis adapted to include plastic-strain effects demonstrates that both the strain-magnitude dependence of elastic strains and the occurrence of plastic strain contribute to these differences between the static and dynamic moduli

  8. Neutron porosity logging and core porosity measurements in the Beauvoir granite, Massif Central Range, France

    NASA Astrophysics Data System (ADS)

    Gallé, C.

    1994-08-01

    A large suite of geophysical logs have been run in the Beauvoir granite. The drillhole (900 m deep), first target of the French Deep Geology programme, is located in the Hercynian bedrock of Echassières in central France (Massif Central Range). After geochemical and petrological studies, the batholith was used for experiments pertaining to the storage of radioactive wastes. With its low porosity, its weak fracturing and its high homogeneity, the Beauvoir granite was chosen for the analysis of the relationship between logged data and the properties measured in the core. The study focused on neutron porosity and core water porosity. The Beauvoir granite has a total free water porosity of around 2% (average value of 54 core samples of rock mass) and an average neutron porosity of around 10%. We show that the origin of this significant difference is related to the neutron matrix effect of the granite. This phenomenon is partly due to the slowing-down effect of the combined water of clays and micas but also to the neutronic capture effect linked with the relatively high lepidolite (lithium mica) content of the granite. The Li 2O content controls 85% of the granite macroscopic capture cross-section. These two factors represent around 75% of the global neutron porosity of the Beauvoir granite. They have to be taken into consideration to get representative water contents of a low-porosity igneous rock from a neutron porosity log. Further investigations also demonstrated the necessity of choosing a better adapted neutron tool calibration for crystalline rocks. Instead of a standard calibration with limestone blocks, a calibration in granite blocks was simulated in order to obtain a better evaluation of the global neutron response of the granite. Then, by correcting this new neutron porosity for the matrix effect, it has been possible to determine water contents in accordance with laboratory water porosity values measured on core samples (2% average porosity). This

  9. Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

    SciTech Connect

    B.M. Freifeild

    2001-10-18

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  10. Control of Interacting Vortex Flows at Subsonic and Transonic Speeds Using Passive Porosity

    NASA Technical Reports Server (NTRS)

    Erickson, Gary E.

    2003-01-01

    A wind tunnel experiment was conducted in the NASA Langley Research Center (LaRC) 8-foot Transonic Pressure Tunnel (TPT) to determine the effects of passive surface porosity on vortex flow interactions about a general research fighter configuration at subsonic and transonic speeds. Flow- through porosity was applied to a wind leading-edge extension (LEX) mounted to a 65 deg cropped delta wind model to promote large nose-down pitching moment increments at high angles of attack. Porosity decreased the vorticity shed from the LEX, which weakened the LEX vortex and altered the global interactions of the LEX and wing vortices at high angles of attack. Six-component forces and moments and wing upper surface static pressure distributions were obtained at free- stream Mach numbers of 0.50, 0.85, and 1.20, Reynolds number of 2.5(10(exp-6) per foot, angles of attack up to 30 deg and angles of sideslip to plus or minus 8 deg. The off-surface flow field was visualized in selected cross-planes using a laser vapor screen flow visualization technique. Test data were obtained with a centerline vertical tail and with alternate twin, wing-mounted vertical fins having 0 deg and 30 deg cant angles. In addition, the porosity of the LEX was compartmentalized to determine the sensitivity of the vortex- dominated aerodynamics to the location and level of porosity applied to the LEX.

  11. Anomalous diffusion of fluid momentum and Darcy-like law for laminar flow in media with fractal porosity

    NASA Astrophysics Data System (ADS)

    Balankin, Alexander S.; Valdivia, Juan-Carlos; Marquez, Jesús; Susarrey, Orlando; Solorio-Avila, Marco A.

    2016-08-01

    In this Letter, we report experimental and theoretical studies of Newtonian fluid flow through permeable media with fractal porosity. Darcy flow experiments were performed on samples with a deterministic pre-fractal pore network. We found that the seepage velocity is linearly proportional to the pressure drop, but the apparent absolute permeability increases with the increase of sample length in the flow direction L. We claim that a violation of the Hagen-Poiseuille law is due to an anomalous diffusion of the fluid momentum. In this regard we argue that the momentum diffusion is governed by the flow metric induced by the fractal topology of the pore network. The Darcy-like equation for laminar flow in a fractal pore network is derived. This equation reveals that the apparent absolute permeability is independent of L, only if the number of effective spatial degrees of freedom in the pore-network ν is equal to the network fractal (self-similarity) dimension D, e.g. it is in the case of fractal tree-like networks. Otherwise, the apparent absolute permeability either decreases with L, if ν < D, e.g. in media with self-avoiding fractal channels, or increases with L, if ν > D, as this is in the case of the inverse Menger sponge.

  12. Porosity and the ecology of icy satellites

    NASA Technical Reports Server (NTRS)

    Croft, Steven K.

    1993-01-01

    The case for a significant role for porosity in the structure and evolution of icy bodies in the Solar System has been difficult to establish. We present a relevant new data set and a series of structure models including a mechanical compression, not thermal creep, model for porosity that accounts satisfactorily for observed densities, moments of inertia, geologic activity, and sizes of tectonic features on icy satellites. Several types of observational data sets have been used to infer significant porosity, but until recently, alternative explanations have been preferred. Our first area of concern is the occurrence of cryovolcanism as a function of satellite radius; simple radiogenic heating models of icy satellites suggest minimum radii for melting and surface cryovolcanism to be 400 to 500 km, yet inferred melt deposits are seen on satellites half that size. One possible explanation is a deep, low conductivity regolith which lowers conductivity and raises internal temperatures, but other possibilities include tidal heating or crustal compositions of low conductivity. Our second area of concern is the occurrence and magnitude of tectonic strain; tectonic structures have been seen on icy satellites as small as Mimas and Proteus. The structures are almost exclusively extensional, with only a few possible compression Al features, and inferred global strains are on the order of 1 percent expansion. Expansions of this order in small bodies like Mimas and prevention of late compressional tectonics due to formation of ice mantles in larger bodies like Rhea are attained only in structure models including low-conductivity, and thus possibly high porosity, crusts. Thirdly, inferred moments of inertia less than 0.4 in Mimas and Tethys can be explained by high-porosity crusts, but also by differentiation of a high density core. Finally, the relatively low densities of smaller satellites like Mimas and Miranda relative to larger neighbors can be explained by deep porosity

  13. Hayward Fault rocks: porosity, density, and strength measurements

    USGS Publications Warehouse

    Morrow, C.A.; Lockner, D.A.

    2001-01-01

    Porosity, density and strength measurements were conducted on rock samples collected from the Hayward Fault region in Northern California as part of the Hayward Fault Working Group’s efforts to create a working model of the Hayward Fault. The rocks included in this study were both fine and coarse grained gabbros, altered keratophyre, basalt, sandstone, and serpentinite from various rock formations adjacent to the Hayward Fault. Densities ranged from a low of 2.25 gm/cc (altered keratophyre) to 3.05 gm/cc (fine gabbro), with an average of 2.6 gm/cc, typical of many other rocks. Porosities were generally around 1% or less, with the exception of the sandstone (7.6%) and altered keratophyre (13.5%). Failure and frictional sliding tests were conducted on intact rock cylinders at room temperature under effective pressure conditions of up to 192 MPa, simulating depths of burial to 12 km. Axial shortening of the samples progressed at a rate of 0.1 µm/sec (fine samples) or 0.2 µm/sec (porous samples) for 6 mm of displacement. Velocity stepping tests were then conducted for an additional 2 mm of displacement, for a total of 8 mm. Both peak strength (usually failure strength) and frictional strength, determined at 8 mm of displacement, increased systematically with effective pressure. Coefficients of friction, based on the observed fracture angles, ranged from 0.6 to 0.85, consistent with Byerlee’s Law. Possible secondary influences on the strength of the Hayward rock samples may be surface weathering, or a larger number of pre-existing fractures due to the proximity to the Hayward Fault. All samples showed velocity strengthening, so that the average a-b values were all strongly positive. There was no systematic relation between a-b values and effective pressure. Velocity strengthening behavior is associated with stable sliding (creep), as observed in the shallow portions of the Hayward Fault.

  14. Porosity and permeability evolution of clay faults: in situ experiments

    NASA Astrophysics Data System (ADS)

    Henry, P.; Guglielmi, Y.; Seguy, S.; Lefevre, M.; Ghani, I.; Gent, G.; Castilla, R.; Gout, C.; Dick, P.; Nussbaum, C.; Durand, J.

    2015-12-01

    Fault models associating low permeability cores with high permeability damage zones are widely accepted, however, constitutive laws relating permeability with fault structure, stress, and strain remain poorly constrained. We here present preliminary results of hydromechanical experiments performed at the 10 m scale in fault zones in Toarcian and Aalenian black shale formations. Intact formations have a very low permeability (10-19 to 10-22 m2). One case (in IRSN's Tournemire Underground Research Laboratory) displays a porosity increase in and around the fault core and abundant veins and calcite cemented small faults in the damage zone. The other case (Mont Terri Swisstopo Underground Research Laboratory) displays a porosity decrease in the fault core zone and few veins. However, under the present stress state, the static permeability of the fractured zones at both locations is higher than that of the intact formation by up to 3 orders of magnitude. During borehole pressurization tests three regimes of permeability variations are observed. (1) Fracture permeability first increases progressively as a function of fluid pressure (2) When a threshold is reached, permeability further increases by 100 or more, but strain as well as permeability variations remain in most part reversible. (3) When a steady pressure is maintained in the injection borehole (from 20 minutes to several days) flow rate tends to decrease with time. These results show that high transient permeability may locally occur in a fault zone under conditions when most of the deformation is reversible, opening the possibility of transient fluid migration decoupled from slip along faults that are not favorably oriented. However, during one test, more than 1 mm of irreversible slip occurred along one of the main interfaces, associated with a sudden increase in flow rate (from 11 to more than 40 l/min). This suggests that when slip occurs, it could result in permeability variations that may remain difficult

  15. Multi-Rate Mass Transfer (MRMT) models for general diffusive porosity structures

    NASA Astrophysics Data System (ADS)

    Babey, Tristan; de Dreuzy, Jean-Raynald; Casenave, Céline

    2015-02-01

    We determine the relevance of Multi-Rate Mass Tansfer (MRMT) models (Haggerty and Gorelick, 1995) to general diffusive porosity structures. To this end, we introduce Structured INteracting Continua (SINC) models as the combination of a finite number of diffusion-dominated interconnected immobile zones exchanging with an advection-dominated mobile domain. It directly extends Multiple INteracting Continua framework (Pruess and Narasimhan, 1985) by introducing a structure in the immobile domain, coming for example from the dead-ends of fracture clusters or poorly-connected dissolution patterns. We demonstrate that, whatever their structure, SINC models can be made equivalent in terms of concentration in the mobile zone to a unique MRMT model. We develop effective shape-free numerical methods to identify its few dominant rates, that comply with any distribution of rates and porosities. We show that differences in terms of macrodispersion are not larger than 50% for approximate MRMT models with only one rate (double porosity models), and drop down to less than 0.1% for five rates MRMT models. Low-dimensional MRMT models accurately approach transport in structured diffusive porosities at intermediate and long times and only miss early responses.

  16. Simulations of Coulombic Fission of Charged Inviscid Drops

    NASA Astrophysics Data System (ADS)

    Burton, J. C.; Taborek, P.

    2011-04-01

    We present boundary-integral simulations of the evolution of critically charged droplets. For such droplets, small perturbations are unstable and eventually lead to the formation of a lemon-shaped drop with very sharp tips. For perfectly conducting drops, the tip forms a self-similar cone shape with a subtended angle identical to that of a Taylor cone, and quantities such as pressure and velocity diverge in time with power-law scaling. In contrast, when charge transport is described by a finite conductivity, we find that small progeny drops are formed at the tips, whose size decreases as the conductivity is increased. These small progeny drops are of nearly critical charge, and are precursors to the emission of a sustained flow of liquid from the tips as observed in experiments of isolated charged drops.

  17. Visualization and prediction of porosity in roller compacted ribbons with near-infrared chemical imaging (NIR-CI).

    PubMed

    Khorasani, M; Amigo, J M; Sonnergaard, J; Olsen, P; Bertelsen, P; Rantanen, J

    2015-05-10

    The porosity of roller compacted ribbon is recognized as an important critical quality attribute which has a huge impact on the final product quality. The purpose of this study was to investigate the use of near-infrared chemical imaging (NIR-CI) for porosity estimation of ribbons produced at different roll pressures. Two off-line methods were utilized as reference methods. The relatively fast method (oil absorption) was comparable with the more time-consuming mercury intrusion method (R(2)=0.98). Therefore, the oil method was selected as the reference off line method. It was confirmed by both reference methods that ribbons compressed at a higher pressure resulted in a lower mean porosity. Using NIR-CI in combination with multivariate data analysis it was possible to visualize and predict the porosity distribution of the ribbons. This approach is considered important for process monitoring and control of continuously operating roller compaction line. PMID:25746502

  18. Dolomite reservoirs: Porosity evolution and reservoir characteristics

    SciTech Connect

    Sun, S.Q.

    1995-02-01

    Systematic analyses of the published record of dolomite reservoirs worldwide reveal that the majority of hydrocarbon-producing dolomite reservoirs occurs in (1) peritidal-dominated carbonate, (2) subtidal carbonate associated with evaporitic tidal flat/lagoon, (3) subtidal carbonate associated with basinal evaporite, and (4) nonevaporitic carbonate sequence associated with topographic high/unconformity, platform-margin buildup or fault/fracture. Reservoir characteristics vary greatly from one dolomite type to another depending upon the original sediment fabric, the mechanism by which dolomite was formed, and the extent to which early formed dolomite was modified by post-dolomitization diagenetic processes (e.g., karstification, fracturing, and burial corrosion). This paper discusses the origin of dolomite porosity and demonstrates the porosity evolution and reservoir characteristics of different dolomite types.

  19. Calorific and porosity development in carbonized wood

    SciTech Connect

    Baileys, R.T.; Blankenhorn, P.R.

    1982-07-01

    Wood of four species (red oak, southern yellow pine, black cherry, and hybrid poplar) were carbonized in a flowing nitrogen atmosphere at an average heating rate of 3 degrees Centigrade/minute to selected final temperatures up to 700 degrees Centigrade. The effects of final carbonization temperature on selected properties of the char were obtained using an adiabatic oxygen bomb calorimeter to investigate heat of combustion and a mercury porosimeter to investigate total porosity, real density, apparent density, and pore size distribution. Pore characteristics of carbonized wood developed before 300 degrees Centigrade in southern yellow pine and before 400 degrees Centigrade in red oak, black cherry, and hybrid poplar. Statistical analysis established linear relationships between heat of combustion versus final carbonization temperature in the carbonization temperature ranges investigated. The results of this study will aid in understanding optimum pryrolysis conditions for the development of calorific and porosity values. (Refs. 22).

  20. Gas bubble transport and emissions for shallow peat from a northern peatland: The role of pressure changes and peat structure

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Slater, Lee

    2015-01-01

    Gas bubbles are an important pathway for methane release from peatlands. The mechanisms controlling gas bubble transport and emissions in peat remain uncertain. The effects of hydrostatic pressure and peat structure on the dynamics of gas bubbles in shallow peat were therefore tested in laboratory experiments. A peat monolith was retrieved from a raised bog and maintained in a saturated state. Three distinct layers were identified from noninvasive permittivity measurements supported by soil physical properties (porosity, bulk density). Phase I of the experiment involved monitoring for the accumulation of gas bubbles under steady pressure and temperature conditions. The data showed evidence for gas bubbles being impeded by a shallow semiconfining layer at depths between 10 and 15 cm. Visible gas bubbles observed on the side of the sample box were recorded over time to estimate changes in the vertical distribution of volumetric gas content. Porosity estimates derived using the Complex Refraction Index Model (CRIM) suggest that gas bubbles enlarge the pore space when the exerted pressure is high enough. Phase II involved triggering release of trapped bubbles by repeatedly increasing and decreasing hydrostatic pressure in an oversaturated condition. Comparison of changes in pressure head and methane density in the head space confirmed that the increasing buoyancy force during drops in pressure is more important for triggering ebullition than increasing mobility during increases in pressure. Our findings demonstrate the importance of changes in hydrostatic pressure on bubble size and variations in resistance of the peat fabric in regulating methane releases from peatlands.

  1. Effect of Pellet Coatings on PETN Porosity and Slapper Detonator Efficacy

    NASA Astrophysics Data System (ADS)

    Brown, Kathryn; Haroz, Erik; Brown, Geoff; Monroe, Deirdre

    2015-06-01

    PETN is well known to have a high vapor pressure and tends to sublime when heated. Preliminary experiments suggest that this phenomenon results in increased porosity and may decrease sensitivity to shock initiation by a chip slapper detonator. In this study, PETN pellets were coated on the flyer impact surface with various materials. The pellets were subjected to heating over several days, and the surfaces were analyzed for porosity and recrystallization. We attempted to shock initiate each using a chip slapper detonator, and the timing and voltages required were noted.

  2. Numerical investigations of the porosity effect on the shock focusing process

    NASA Astrophysics Data System (ADS)

    Balasubramanian, K.; Eliasson, V.

    2013-11-01

    The effect of cylindrical obstacles and the porosity in between them along the path of a converging cylindrical shock is studied through numerical simulations. An initially cylindrical converging shock wave is perturbed by cylindrical obstacles placed radially in its path. High pressures and temperatures are achieved as the shock wave is focused. Results show that the shape of the shock wave close to the point of convergence as well as the porosity and type of shock wave reflection the converging shock undergoes influence the peak values. Various configurations of the obstacle size and number are considered. The Guderley constant for each case is compared with previous reported experimental values.

  3. Proton transport in ice at 30–140 K: Effects of porosity

    SciTech Connect

    Bu, Caixia Baragiola, Raúl A.

    2015-08-21

    We examined the role of porosity, a crucial characteristic of amorphous solid water (ASW), on electrostatic charging and discharging of ASW films with 500 eV He{sup +} and Xe{sup +} ions, by measuring the surface potentials with a Kelvin probe. When a charged ASW film is heated, its surface potential decreases sharply, at temperatures that depend on the maximum temperature the film was once subject to. This sharp decrease of the surface potential is not due to a large thermally induced increase of the dielectric constant ε as proposed in other studies, since measurements of ε yielded a value of ∼3 below ∼100 K. Rather, the potential drop can be explained by the transport of the surface charge to the substrate, which depends on film porosity. We propose that the charge migrates along the walls of the pores within the ASW film, facilitated by the thermally induced reorientation of the incompletely coordinated molecules on the pore walls.

  4. Diagenesis and porosity development in Oriskany sandstone of West Virginia

    SciTech Connect

    Bruner, K.R.; Heald, M.T. )

    1988-08-01

    Petrographic investigation of 12 Oriskany cores from West Virginia and surrounding states shows a complex relationship between diagenesis and porosity development. Deposited as a fossiliferous marine sandstone, the Oriskany is cemented by calcium carbonate and/or quartz, depending on the predominant clastic material (fossils or quartz). Porosity ranges from less than 2% to approximately 8%, and pore types vary across the state. Primary-intergranular and fracture are the major porosity types observed in all cores. Primary porosity is best developed in central and western areas where cementation is incomplete. Petroleumlike materials (paraffin in nature) commonly occur as pore linings or inclusions in secondary quartz. To the east, fracture porosity dominated in tightly cemented sandstones, but vertical and horizontal fractures are observed in all cores. Many fractures, however, have been healed with quartz and calcite. Minor amounts of carbonate leaching supplements primary porosity. In Marion County, partial replacement of carbonate fossils by fringing microcrystalline quartz, along with recrystallization and subsequent leaching of the carbonate, has produced distinctive secondary pores. Porosity increases dramatically in western areas of the state. In addition to primary and secondary porosity, microcrystalline porosity within chert and phosphatic zones is present. Other minor and relatively insignificant porosity types in the Oriskany from all regions include intraskeletal, intragranular quartz and feldspar, and intercrystalline dolomite. Although overall porosity is low, intergranular porosity and fracture porosity are best developed in quartz-rich zones.

  5. Porosity evolution in a creeping single crystal

    NASA Astrophysics Data System (ADS)

    Srivastava, A.; Needleman, A.

    2012-04-01

    Experimental observations on tensile specimens in Srivastava et al (2012 in preparation) indicated that the growth of initially present processing induced voids in a nickel-based single crystal superalloy played a significant role in limiting creep life. Also, creep tests on single crystal superalloy specimens typically show greater creep strain rates and/or reduced creep life for thinner specimens than predicted by current theories. In order to quantify the role of void growth in single crystals in creep loading, we have carried out three-dimensional finite deformation finite element analyses of unit cells containing a single initially spherical void. The materials are characterized by a rate-dependent crystal plasticity constitutive relation accounting for primary and secondary creep. Two types of imposed loading are considered: an applied true stress (force/unit current area) that is time independent; and an applied nominal stress (force/unit initial area) that is time independent. Isothermal conditions are assumed. The evolution of porosity is calculated for various values of stress triaxiality and of the Lode parameter. The evolution of porosity with time is sensitive to whether constant true stress or constant nominal stress loading is applied. However, the evolution of porosity with the overall unit cell strain is insensitive to the mode of loading. At high values of stress triaxiality, the response is essentially independent of the value of the Lode parameter. At sufficiently low values of the stress triaxiality, the porosity evolution depends on the value of the Lode parameter and void collapse can occur. Also, rather large stress concentrations can develop which could play a role in the observed thickness dependence.

  6. Reducing the open porosity of pyroboroncarbon articles

    NASA Astrophysics Data System (ADS)

    Martyushov, G. G.; Zakharevich, A. M.; Pichkhidze, S. Ya.; Koshuro, V. A.

    2016-02-01

    It is established that a decrease in the open porosity of pyroboroncarbon, a pyrolytic glassy composite material of interest for manufacturing prosthetic heart valves (PHVs), can be achieved via impregnation of articles with an alcohol solution of 3-aminopropyltriethoxysilane and subsequent thermal treatment. The maximum roughness height and linear size of open pores on the surface of PHV parts made of pyroboroncarbon can additionally be reduced by final mechanical processing of a silicon oxide film formed on the surface.

  7. Effect of porosity and NaCl concentration on the osmotic efficiency of a sodium bentonite membrane

    SciTech Connect

    Fritz, S.J.; Marine, I.W.

    1982-01-01

    Osmosis has been cited as a mechanism for explaining anomalously high fluid pressures in the subsurface. Clays and shales act as membranes, and osmotic flux across these units may result in pressures sufficiently high to explain these anomalies. The theoretical osmotic pressures as calculated solely from solution properties can be quite large; however, it is not yet resolved whether these geologic membranes are sufficiently ideal to generate such pressures. Osmotic efficiencies of a Na-bentonite were measured by a series of hyperfiltration experiments using various molarities of NaCl at two different porosities. The highest osmotic efficiency (0.8912) occurred at the lower porosity and the lowest NaCl input solution. The lowest measured osmotic efficiency (0.0423) occurred at the higher porosity and the highest NaCl input concentration. 26 references, 2 figures, 2 tables.

  8. The porosity of the upper lunar regolith

    NASA Astrophysics Data System (ADS)

    Hapke, Bruce; Sato, Hiroyuki

    2016-07-01

    The porosity of the upper centimeter or so of the lunar regolith strongly affects several properties that are commonly studied remotely. Hence, it is important to determine its value. We have reanalyzed the data of Ohtake et al. (Ohtake et al. [2010]. Space Sci. Rev., 154, 57-77), who used spacecraft and laboratory reflectance measurements of the Moon by Kaguya Multiband Imager instruments and an Apollo sample to infer a lunar regolith porosity of 74-87%. Our analysis was augmented by using Lunar Reconnaissance Orbiter Wide and Narrow Angle Camera images. We confirm the Ohtake et al. (Ohtake et al. [2010]. Space Sci. Rev., 154, 57-77) estimate and refine it to 83 ± 3%. However, depending on the validity of key assumptions, this value could be a lower limit, so that the actual porosity could be somewhat higher. Even though the magnetic resonance index of the sample indicates that it is mature, it is appears to be optically less mature than a standard photometric site near the sample collection site.

  9. A growing-drop technique for measuring dynamic interfacial tension

    SciTech Connect

    MacLeod, C.A.; Radke, C.J.

    1993-10-01

    A novel, growing-drop technique is described for measuring dynamic interfacial tension due to sorption of surface-active solutes. The proposed method relates the instantaneous pressure and size of expanding liquid drops to interfacial tension and is useful for measuring both liquid/gas and liquid/liquid tensions over a wide range of time scales, currently from 10 ms to several hours. Growing-drop measurements on surfactant-free water/air and water/octanol interfaces yield constant tensions equal to their known literature values. For surfactant-laden, liquid drops, the growing-drop technique captures the actual transient tension evolution of a single interface, rather than interval times as with the classic maximum-drop-pressure and drop.-volume tension measurements. Dynamic tensions measured for 0.25 mM aqueous 1-decanol solution/air and 0.02 kg/m{sup 3} aqueous Triton X-100 solution/dodecane interfaces show nonmonotonic behavior, indicating slow surfactant transport relative to the imposed rates of interfacial dilatation. The dynamic tension of a purified and fresh 6 mM aqueous sodium dodecyl sulfate (SDS) solution/air interface shows only a monotonic decrease, indicating rapid surfactant transport relative to the imposed rates of dilatation. ConverselY, an aged SDS solution, naturally containing trace dodecanol impurities, exhibits dynamic tensions which reflect a superposition of the rapidly equilibrating SDS and the slowly adsorbing dodecanol.

  10. Theoretical Exploration of Barrel-Shaped Drops on Cactus Spines.

    PubMed

    Luo, Cheng

    2015-11-01

    To survive an arid environment, desert cacti are capable of harvesting water from fog by transporting condensed water drops using their spines. Cactus spines have a conical shape. In this work, on the basis of the difference of liquid pressure, a new theoretical model has been developed for a barrel-shaped liquid drop on a conical wire. This model is further simplified to interpret the effects of contact angles, conical angle, surface microgrooves, and gravity on the drop movement along a cactus spine.

  11. Theoretical Exploration of Barrel-Shaped Drops on Cactus Spines.

    PubMed

    Luo, Cheng

    2015-11-01

    To survive an arid environment, desert cacti are capable of harvesting water from fog by transporting condensed water drops using their spines. Cactus spines have a conical shape. In this work, on the basis of the difference of liquid pressure, a new theoretical model has been developed for a barrel-shaped liquid drop on a conical wire. This model is further simplified to interpret the effects of contact angles, conical angle, surface microgrooves, and gravity on the drop movement along a cactus spine. PMID:26473466

  12. Hanging drop crystal growth apparatus

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J. (Inventor); Witherow, William K. (Inventor); Carter, Daniel C. (Inventor); Bugg, Charles E. (Inventor); Suddath, Fred L. (Inventor)

    1990-01-01

    This invention relates generally to control systems for controlling crystal growth, and more particularly to such a system which uses a beam of light refracted by the fluid in which crystals are growing to detect concentration of solutes in the liquid. In a hanging drop apparatus, a laser beam is directed onto drop which refracts the laser light into primary and secondary bows, respectively, which in turn fall upon linear diode detector arrays. As concentration of solutes in drop increases due to solvent removal, these bows move farther apart on the arrays, with the relative separation being detected by arrays and used by a computer to adjust solvent vapor transport from the drop. A forward scattering detector is used to detect crystal nucleation in drop, and a humidity detector is used, in one embodiment, to detect relative humidity in the enclosure wherein drop is suspended. The novelty of this invention lies in utilizing angular variance of light refracted from drop to infer, by a computer algorithm, concentration of solutes therein. Additional novelty is believed to lie in using a forward scattering detector to detect nucleating crystallites in drop.

  13. Binary drop coalescence in liquids

    NASA Astrophysics Data System (ADS)

    Kim, Jungyong

    Experiments on binary drop collisions within an index-matched liquid were conducted for Weber numbers (We) of 1-50 and collision angles of 15-80° below the horizontal. Drop pairs of water/glycerin mixture were injected into silicone oil and, due to gravitational effects, traveled on downward trajectories before colliding. A dual-field high-speed PIV measurement system was employed to quantify drop trajectories and overall collision conditions while simultaneously examining detailed velocity fields near the collision interface. In the We range examined, for equal size drops, both rebounding and coalescing behavior occurred. The drops coalesced for We > 10 and rebounded for We < 10, and this boundary was found to be insensitive to collision angle. Coalescence was found to result from a combination of vortical flow within drops and strong drop deformation characteristic of higher We. Flow through the centers of opposing ring vortices, strengthened by drop deformation, enhanced drainage of the thin film in the impact region, leading to film rupture and coalescence. The collision angle affected the eventual location of film rupture, with the rupture location moving higher in the thin film region as the collision angle increased. The film rupture location correlated closely with the location of maximum downward velocity in the thin film. The time between collision and rupture increases with We until We = 30. For We > 30, the time decreases as We increases. Unequal size drop collisions with drop size ratios (Ds/D L) of 0.7 and 0.5 were also examined. Coalescence occurs above We* = 11 similar to equal size drops. As drop size ratio decreases, the intervening film deforms more. If the velocity ratio uL/u s < 1, the deformed interface becomes flat before coalescence. The rupture location varies due to the asymmetry of the drops. As collision offset increases (B > 0), the film rupture time is shortened and mixing of the fluid from both drops is enhanced after coalescence

  14. On the tensorial nature of advective porosity

    NASA Astrophysics Data System (ADS)

    Neuman, Shlomo P.

    2005-02-01

    Field tracer tests indicate that advective porosity, the quantity relating advective velocity to Darcy flux, may exhibit directional dependence. Hydraulic anisotropy explains some but not all of the reported directional results. The present paper shows mathematically that directional variations in advective porosity may arise simply from incomplete mixing of an inert tracer between directional flow channels within a sampling (or support) volume ω of soil or rock that may be hydraulically isotropic or anisotropic. In the traditional fully homogenized case, our theory yields trivially a scalar advective porosity equal to the interconnected porosity ϕ, thus explaining neither the observed directional effects nor the widely reported experimental finding that advective porosity is generally smaller than ϕ. We consider incomplete mixing under conditions in which the characteristic time tD of longitudinal diffusion along channels across ω is much shorter than the characteristic time tH required for homogenization through transverse diffusion between channels. This may happen where flow takes place preferentially through relatively conductive channels and/or fractures of variable orientation separated by material that forms a partial barrier to diffusive transport. Our solution is valid for arbitrary channel Peclet numbers on a correspondingly wide range of time scales tD ⩽ t ≪ tH. It shows that the tracer center of mass is advected at a macroscopic velocity which is generally not collinear with the macroscopic Darcy flux and exceeds it in magnitude. These two vectors are related through a second-rank symmetric advective dispersivity tensor Φ. If the permeability k of ω is a symmetric positive-definite tensor, so is Φ. However, the principal directions and values of these two tensors are generally not the same; whereas those of k are a fixed property of the medium and the length-scale of ω, those of Φ depend additionally on the direction and magnitude of the

  15. The origin of star-shaped oscillations of Leidenfrost drops

    NASA Astrophysics Data System (ADS)

    Ma, Xiaolei; Burton, Justin C.

    We experimentally investigate the oscillations of Leidenfrost drops of water, liquid nitrogen, ethanol, methanol, acetone and isopropyl alcohol. The drops levitate on a cushion of evaporated vapor over a hot, curved surface which keeps the drops stationary. We observe star-shaped modes along the periphery of the drop, with mode numbers n = 2 to 13. The number of observed modes is sensitive to the properties of the liquid. The pressure oscillation frequency in the vapor layer under the drop is approximately twice that of the drop frequency, which is consistent with a parametric forcing mechanism. However, the Rayleigh and thermal Marangoni numbers are of order 10,000, indicating that convection should play a dominating role as well. Surprisingly, we find that the wavelength and frequency of the oscillations only depend on the thickness of the liquid, which is twice the capillary length, and do not depend on the mode number, substrate temperature, or the substrate curvature. This robust behavior suggests that the wavelength for the oscillations is set by thermal convection inside the drop, and is less dependent on the flow in the vapor layer under the drop

  16. Matrix-fracture interactions in dual porosity simulation

    SciTech Connect

    Shook, G.M.

    1996-01-01

    A new method for simulating flow in fractured media is presented which uses a truncated version of the analytical solution to resolve pressure transients in the rock matrix. The point at which the series solution may be truncated is a known function of the problem, and may therefore be readily determined. Furthermore, the functional form of the method is essentially dimension-independent, and implementation of the method requires only minimal modification to an existing dual porosity simulator. Three test cases are presented comparing results from fine grid simulations, Warren and Root simulations, and the new formulation. In each of the three cases presented, excellent agreement with the fine grid simulations is obtained using the new method. The W&R formulation exhibits excessive error throughout the simulated time, first underpredicting outflow rates, and then overpredicting rates. The error using the W&R formulation is largest for 3-D fracture networks, but is large for all cases tested.

  17. Spark plasma sintering and porosity studies of uranium nitride

    NASA Astrophysics Data System (ADS)

    Johnson, Kyle D.; Wallenius, Janne; Jolkkonen, Mikael; Claisse, Antoine

    2016-05-01

    In this study, a number of samples of UN sintered by the SPS method have been fabricated, and highly pure samples ranging in density from 68% to 99.8%TD - corresponding to an absolute density of 14.25 g/cm3 out of a theoretical density of 14.28 g/cm3 - have been fabricated. By careful adjustment of the sintering parameters of temperature and applied pressure, the production of pellets of specific porosity may now be achieved between these ranges. The pore closure behaviour of the material has also been documented and compared to previous studies of similar materials, which demonstrates that full pore closure using these methods occurs near 97.5% of relative density.

  18. The Effect of Porosity on Fatigue of Die Cast AM60

    NASA Astrophysics Data System (ADS)

    Yang, Zhuofei; Kang, Jidong; Wilkinson, David S.

    2016-07-01

    AM60 high-pressure die castings are known to contain significant porosity which can affect fatigue life. We have studied this using samples drawn from prototype AM60 shock towers by conducting strain-controlled fatigue tests accompanied by X-ray computed tomography analysis. The results show that the machined surface is the preferential location for fatigue crack development, with pores close to these surfaces serving as initiation sites. Fatigue life shows a strong inverse correlation with the size of the fatigue-crack-initiating pore. Pore shape and pore orientation also influence the response. A supplemental study on surface roughness shows that porosity is the dominant factor in fatigue. Tomography enables the link between porosity and fatigue crack initiation to be clearly identified. These data are complemented by SEM observations of the fracture surfaces which are generally flat and full of randomly oriented serration patterns but without long-range fatigue striations.

  19. A boundary-integral model for drop deformation between two parallel plates with non-unit viscosity ratio drops

    NASA Astrophysics Data System (ADS)

    Janssen, P. J. A.; Anderson, P. D.

    2008-10-01

    A boundary-integral method is presented for drop deformation between two parallel walls for non-unit viscosity ratio systems. To account for the effect of the walls the Green's functions are modified and all terms for the double-layer potential are derived. The full three-dimensional implementation is validated, and the model is shown to be accurate and consistent. The method is applied to study drop deformation in shear flow. An excellent match with small-deformation theory is found at low capillary numbers, and our results match with other BIM simulations for pressure-driven flows. For shear flow with moderate capillary numbers, we see that the behavior of a low-viscosity drop is similar to that of drop with a viscosity ratio of unity. High-viscosity drops, on the other hand, are prevented from rotating in shear flow, which results in a larger deformation, but less overshoot in the drop axes is observed. In contrast with unconfined flow, high-viscosity drops can be broken in shear flow between parallel plates; for low-viscosity drops the critical capillary number is higher in confined situations.

  20. Instant freezing of impacting wax drops

    NASA Astrophysics Data System (ADS)

    Ponomarenko, Alexandre; Virot, Emmanuel; Rubinstein, Shmuel

    2015-11-01

    We present the impact of hot liquid drops of wax on surfaces whose temperature is below the solidifying temperature of the drops. During the fall the drops remain mostly liquid, but upon impact, their temperature quickly decreases resulting in the solidification of the drop. Depending on the impact energy, drops size and the temperature difference between the drop and the surface this results in plethora of solid shapes: simple lenses, triangular drops, spherical caps and popped popcorn shapes.

  1. Pool impacts of Leidenfrost drop

    NASA Astrophysics Data System (ADS)

    Darbois Texier, Baptiste; Maquet, Laurent; Dorbolo, Stephane; Dehandschoewercker, Eline; Pan, Zhao; Truscott, Tadd

    2015-11-01

    This work concerns the impact of a droplet made of a volatile liquid (typically HFE) on a pool of an other liquid (typically silicone oil) which temperature is above the boiling point of the drop. Depending on the properties of the two liquids and the impacting conditions, four different regimes are observed. For low impacting speeds, the droplet bounces on the surface of the bath and finally levitates above it in a Leidenfrost state. Such a regime occurs as soon as the pool temperature exceeds the boiling point of the drop. This observation means that there is no threshold in temperature for a Leidenfrost effect on a liquid surface contrary to the case of a solid substrate. For intermediate impacting velocities, the pinch-off of the surface of the pool entraps the drop in the liquid bulk. The entrapped drop is separated from the pool by a layer of its own vapour in a similar way of antibulles. For increasing impacting speeds, the vapour layer between the drop and the pool does not hold during the pinch-off event. The contact of the drop with the hot liquid provokes a sudden and intense evaporation. At very large impacting speeds, the drop rapidely contacts the pool, spreads and finally induces a hemi-spherical cavity. In the end, these four different regimes are summarized in a Froud-Weber diagram which boundaries are discussed.

  2. Electrokinetics of isolated electrified drops.

    PubMed

    Pillai, Rohit; Berry, Joseph D; Harvie, Dalton J E; Davidson, Malcolm R

    2016-04-14

    Using a recently developed multiphase electrokinetic model, we simulate the transient electrohydrodynamic response of a liquid drop containing ions, to both small and large values of electric field. The temporal evolution is found to be governed primarily by two dimensionless groups: (i) Ohnesorge number (Oh), a ratio of viscous to inertio-capillary effects, and (ii) inverse dimensionless Debye length (κ), a measure of the diffuse regions of charge that develop in the drop. The effects of dielectric polarization dominate at low Oh, while effects of separated charge gain importance with increase in Oh. For small values of electric field, the deformation behaviour of a drop is shown to be accurately described by a simple analytical expression. At large electric fields, the drops are unstable and eject progeny drops. Depending on Oh and κ this occurs via dripping or jetting; the regime transitions are shown by a Oh-κ phase map. In contrast to previous studies, we find universal scaling relations to predict size and charge of progeny drops. Our simulations suggest charge transport plays a significant role in drop dynamics for 0.1 ≤ Oh ≤ 10, a parameter range of interest in microscale flows.

  3. Relationship between the consolidation parameter, porosity and aspect ratio in microporous carbonate rocks

    NASA Astrophysics Data System (ADS)

    de Ceia, Marco A. R.; Misságia, Roseane M.; Neto, Irineu Lima; Archilha, Nathaly

    2015-11-01

    The estimation of dry bulk modulus is required for the successful application of the Biot-Gassmann theory to forecast fluid changes within a reservoir. The Pride model is one of the several models described in the literature for predicting the dry elastic moduli of rocks. However, the accuracy of the Pride model depends on the estimation of the consolidation parameter. In this paper, the consolidation parameter was estimated using the pore stiffness, mineral bulk modulus and porosity. That approach allowed calculating the dry bulk modulus of a set of microporous carbonate rocks according to the Pride model and compare those estimates to the results obtained using the elastic velocities. The change in the consolidation parameter over a range of pressures suggests that the relationship between this parameter and the unconfined porosity increases at high effective pressure. Statistical analyses of the distribution of those consolidation parameter values were performed to verify how the effective pressure influences the mean value and variance. Mean pore aspect ratios were estimated using Kuster-Toksoz methodology to establish a relationship with the consolidation parameter and the unconfined porosity. Such relationship also accounts for pressure-dependence within the studied pressure range. Although only 20 samples were analyzed, those studies can contribute to advise the estimation of the consolidation parameter in this type of carbonate rocks.

  4. Instabilities of volatile films and drops

    NASA Astrophysics Data System (ADS)

    Murisic, Nebojsa

    2008-12-01

    We report on instabilities during spreading of volatile liquids, with emphasis on the novel instability observed when isopropyl alcohol (IPA) is deposited on a monocrystalline silicon (Si) wafer. This instability is characterized by emission of drops ahead of the expanding front, with each drop followed by smaller, satellite droplets, forming the structures which we nickname "octopi" due to their appearance. A less volatile liquid, or a substrate of larger heat conductivity, suppress this instability. In addition, we examine the spreading of drops of water (DIW)-IPA mixtures on both Si wafers and plain glass slides, and describe the variety of contact line instabilities which appear. We find that the decrease of IPA concentration in mixtures leads to transition from "octopi" to mushroom-like instabilities. Through manipulation of our experimental set up, we also find that the mechanism responsible for these instabilities appears to be mostly insensitive to both the external application of convection to the gas phase, and the doping of the gas phase with vapor in order to create the saturated environment. In order to better understand the "octopi" instability, we develop a theoretical model for evaporation of a pure liquid drop on a thermally conductive solid substrate. This model includes all relevant physical effects, including evaporation, thermal conductivity in both liquid and solid, (thermocapillary) Marangoni effect, vapor recoil, disjoining pressure, and gravity. The crucial ingredient in this problem is the evaporation model, since it influences both the motion of the drop contact line, and the temperature profiles along the liquid-solid and liquid-gas interfaces. We consider two evaporation models: the equilibrium "lens" model and the non-equilibrium one-sided (NEOS) model. Along with the assumption of equilibrium at the liquid-gas interface, the "lens" model also assumes that evaporation proceeds in a (vapor) diffusion-limited regime, therefore bringing

  5. [Development of intranasal lactocin (oxytocin) drops technology].

    PubMed

    Klimas, Rimantas; Baranauskas, Algirdas; Gendrolis, Antanas

    2002-01-01

    Pure oxytocin substance was obtained from posterior part of cattle pituitary gland by high pressure liquid chromatography. Biological activity of the substance--450-500 IU/mg. Chromatographically pure Oxytocin substance was used in developing two different compositions of Lactocin intranasal drops (40 IU/ml). Stability evaluation was performed for 2 year period. The technical documentation was prepared on the basis of the research results. Lactocin is active preparation helping lactation and is indicated for lactostasis treatment and its prophylaxis after delivery. PMID:12474675

  6. Porosity in plasma sprayed alumina coatings

    SciTech Connect

    Ilavsky, J.; Herman, H.; Berndt, C.C.; Goland, A.N.; Long, G.G.; Krueger, S.; Allen, A.J.

    1994-03-01

    Small-angle neutron scattering (SANS) was used to study the porosity of plasma sprayed deposits of alumina in as-sprayed and heat-treated conditions. SANS results were compared with mercury intrusion porosimetry (MIP) and water immersion techniques. Multiple small-angle neutron scattering yields a volume-weighted effective pore radius (R{sub eff}), for pores with sizes between 0.08 and 10{mu}m, the pore volume in this size region, and from the Porod region, the surface area of pores of all sizes.

  7. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Kalatur, Ekaterina Narikovich, Anton; Buyakova, Svetlana E-mail: kulkov@ispms.tsc.ru; Kulkov, Sergey E-mail: kulkov@ispms.tsc.ru

    2014-11-14

    The article studies the porous ceramics consisting of ultra-fine ZrO{sub 2} powders. The porosity of ceramic samples varied from 15% to 80%. The structure of the ceramic materials had a cellular configuration. The distinctive feature of all experimentally obtained strain diagrams is their nonlinearity at low deformations characterized by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations shown in strain diagrams is due to the mechanical instability of cellular elements of the ceramic framework.

  8. Determination of effective porosity of mudrocks: a feasibility study

    SciTech Connect

    Dorsch, J.

    1995-11-01

    Matrix diffusion is believed to be an important transport process within the double-porosity (primary sedimentary porosity and secondary fracture porosity) mudrock-dominated stratigraphic units on the Oak Ridge Reservation (ORR). Effective porosity is identified as an important parameter for evaluating and modeling matrix diffusion as a transport process. This report identifies, summarizes and evaluates petrophysical techniques, which can be used to determine the effective porosity of mudrock. Most of the techniques found their original application in the petroleum industry for the evaluation of reservoir rocks.

  9. Leidenfrost drops: Effect of gravity

    NASA Astrophysics Data System (ADS)

    Maquet, L.; Brandenbourger, M.; Sobac, B.; Biance, A.-L.; Colinet, P.; Dorbolo, S.

    2015-04-01

    A specific experimental set-up has been installed in a large centrifuge facility in order to study different aspects of Leidenfrost drops under high-gravity conditions (5, 10, 15 and 20 times the Earth gravity). In particular, the drop lifetime and more precisely the variations of drop diameter vs. time have shown to be in good agreement with previous experiments and scaling analysis (Biance A.-L. et al., Phys. Fluids, 15 (2003) 1632). Moreover, so-called chimneys are expectedly observed in the large puddles, the distance between two chimneys depending linearly on the capillary length. Finally, the Leidenfrost point, i.e. the temperature above which the Leidenfrost effect takes place, was unexpectedly found to increase slightly with gravity. A qualitative explanation based on a refined model (Sobac B. et al., Phys. Rev. E, 90 (2014) 053011) recognizing the non-trivial shape of the vapor film under the drop is proposed to explain this observation.

  10. Orion Capsule Mockup is Dropped

    NASA Video Gallery

    An Orion capsule mockup is dropped from a plane 25,000 feet above the Arizona desert to test its parachute design. Orion will return to Earth at speeds faster than previous human spacecraft, and wi...

  11. Porosity of additive manufacturing parts for process monitoring

    SciTech Connect

    Slotwinski, J. A.; Garboczi, E. J.

    2014-02-18

    Some metal additive manufacturing processes can produce parts with internal porosity, either intentionally (with careful selection of the process parameters) or unintentionally (if the process is not well-controlled.) Material porosity is undesirable for aerospace parts - since porosity could lead to premature failure - and desirable for some biomedical implants, since surface-breaking pores allow for better integration with biological tissue. Changes in a part's porosity during an additive manufacturing build may also be an indication of an undesired change in the process. We are developing an ultrasonic sensor for detecting changes in porosity in metal parts during fabrication on a metal powder bed fusion system, for use as a process monitor. This paper will describe our work to develop an ultrasonic-based sensor for monitoring part porosity during an additive build, including background theory, the development and detailed characterization of reference additive porosity samples, and a potential design for in-situ implementation.

  12. Porosity, permeability, and their relationship in granite, basalt, and tuff

    SciTech Connect

    Not Available

    1983-04-01

    This report discusses the porosity, storage, and permeability of fractured (mainly crystalline) rock types proposed as host rock for nuclear waste repositories. The emphasis is on the inter-relationships of these properties, but a number of reported measurements are included as well. The porosity of rock is shown to consist of fracture porosity and matrix porosity; techniques are described for determining the total interconnected porosity through both laboratory and field measurement. Permeability coefficient, as obtained by experiments ranging from laboratory to crustal scale, is discussed. Finally, the problem of determining the relationship between porosity and permeability is discussed. There is no simple, all encompassing relationship that describes the dependence of permeability upon porosity. However, two particular cases have been successfully analyzed: flow through a single rough fracture, and flow through isotropic porous rock. These two cases are discussed in this report.

  13. Porosity of additive manufacturing parts for process monitoring

    NASA Astrophysics Data System (ADS)

    Slotwinski, J. A.; Garboczi, E. J.

    2014-02-01

    Some metal additive manufacturing processes can produce parts with internal porosity, either intentionally (with careful selection of the process parameters) or unintentionally (if the process is not well-controlled.) Material porosity is undesirable for aerospace parts - since porosity could lead to premature failure - and desirable for some biomedical implants, since surface-breaking pores allow for better integration with biological tissue. Changes in a part's porosity during an additive manufacturing build may also be an indication of an undesired change in the process. We are developing an ultrasonic sensor for detecting changes in porosity in metal parts during fabrication on a metal powder bed fusion system, for use as a process monitor. This paper will describe our work to develop an ultrasonic-based sensor for monitoring part porosity during an additive build, including background theory, the development and detailed characterization of reference additive porosity samples, and a potential design for in-situ implementation.

  14. Alleviation of side force on tangent-ogive forebodies using passive porosity

    NASA Technical Reports Server (NTRS)

    Bauer, Steven X. S.; Hemsch, Michael J.

    1992-01-01

    An experimental investigation to determine the effectiveness of porosity for alleviating side forces on forebodies was conducted in the NASA Langley Research Center 7 x 10 ft High-Speed Wind Tunnel. The study consisted of a comparison of experimental force, moment, and surface pressure results obtained on a fineness ratio 5.0 tangent-ogive porous forebody with 0.020 in. hole diameter and 22 percent porosity with results obtained on a solid forebody. The forebodies were tested with cylindrical afterbodies. The solid forebody was tested with transition grit to simulate fully turbulent conditions and without transition grit to simulate free transition conditions. The extent of porosity on the forebody was varied to determine the extent of porosity needed to alleviate side forces. Static longitudinal and lateral-directional stability and surface pressure data were obtained at Mach numbers of 0.2, 0.5, and 0.8. The angle of attack range was from 5 to 45 deg and roll angles from -90 to 180 deg. The solid forebody exhibited large asymmetries at moderate to high angles of attack causing large side forces and yawing moments. The porous forebody exhibited no significant side forces or yawing moments at any angle of attack tested.

  15. Coalescence of Drops of a Power-law Fluid

    NASA Astrophysics Data System (ADS)

    Kamat, Pritish; Thete, Sumeet; Basaran, Osman

    2014-11-01

    Drop coalescence is crucial in a host of industrial, household, and natural processes that involve dispersions. Coalescence is a rate-controlling process in breaking emulsions and strongly influences drop-size-distributions in sprays. In a continuum approach, coalescence begins by the formation of a microscopic, non-slender bridge connecting the two drops. Indefinitely large axial curvature at the neck results in local lowering of pressure that drives fluid from the bulk of the drops toward the neck, thereby causing the bridge radius r (t) and height z (t) to increase in time t. The coalescence of Newtonian drops in air has heretofore been thoroughly studied. Here, we extend these earlier studies by analyzing the coalescence of drops of power-law fluids because many fluids encountered in real applications, including cosmetic creams, shampoos, grease, and paint, exhibit power-law (deformation-rate thinning) rheology. On account of the non-slender geometry of the liquid bridge connecting the two drops (z << r) , we analyze the resulting free surface flow problem by numerical simulation. Among other results, we present and discuss the nature of flows and scaling behaviors for r and z as functions of the initial viscosity and power-law index (0 < n <= 1) .

  16. Compaction and porosity prediction in Chert-Rich sandstones and conglomerates

    SciTech Connect

    Cochran, A. )

    1991-03-01

    Chert-rich sandstones and conglomerates are volumetrically important oil and gas reservoir units in western and northern Canada and in Alaska. Unlike quartzofeldspathic sandstones, chert-rich sandstones are highly susceptible to intergranular pressure solution resulting in dramatic loss of intergranular volume (IGV) and porosity with burial. Thin-section petrographic data were used to develop a suite of IGV-decline curves for chert-rich sandstones and conglomerates as the basis for porosity prediction algorithms. The samples studied range in composition from chert-quartz litharenites (Viking Formation, Paddy-Cadotte and Falher members, western Canada basin) to chert-rich litharenites containing appreciable feldspars and volcanic grains (Clearwater and Belly River formations, western Canada basin, and Reindeer Sequence, Mackenzie Delta). Physical characteristics of chert, such as the degree of microcrystallinity or the presence of impurities and micropores, in part, determine chert's susceptibility to dissolution. Where chert and quartz grains are compacted together, chert is typically penetrated by quartz. Pressure-solution features of chert, such as pocked or dimpled clasts and microstylolitic textures, can be observed in core and cuttings, thin sections, and SEM samples. Early cementation in chert-rich sandstones can limit the effects of compaction. For example, quartz overgrowths in the Viking Formation inhibit later intergranular pressure solution. Formation inhibit later intergranular pressure solution. In chert-rich sandstones and conglomerates, porosity and permeability prediction is complicated by cement timing, cement type and distribution, degree of leaching, and grain textural variety.

  17. Computational analysis of drop-on-demand drop formation

    NASA Astrophysics Data System (ADS)

    Xu, Qi; Basaran, Osman A.

    2007-10-01

    Motivated by the desire to improve the theoretical understanding of drop-on-demand (DOD) ink-jet printing, a computational analysis is carried out to simulate the formation of liquid drops of incompressible Newtonian fluids from a simple capillary tube by imposing a transient flow rate upstream of the nozzle exit. Since the flow in a typical ink-jet nozzle is toward the nozzle outlet during part of the time and away from the nozzle outlet at other times, an inflow rate is adopted here that captures the essential physics and is given in dimensionless form by Q =(π√We /2)sinΩt, where We is the Weber number (inertial/surface tension force), Ω is the frequency, and t is time. The dynamics are studied as functions of We, Ω, and the Ohnesorge number Oh (viscous/surface tension force). For a common ink forming from a nozzle of 10μm radius, Oh =0.1. For this typical case, a phase or operability diagram in (We,Ω)-space is developed that shows that three regimes of operation are possible. In the first regime, where We is low, breakup does not occur, and drops remain pendant from the nozzle and undergo time periodic oscillations. Thus, the simulations show that fluid inertia, and hence We, must be large enough if a DOD drop is to form, in accord with intuition. A sufficiently large We causes both drop elongation and onset of drop necking, but flow reversal is also necessary for the complete evacuation of the neck and capillary pinching. In the other two regimes, at a given Ω, We is large enough to cause drop breakup. In the first of these two regimes, where Wec1drops do form but have negative velocities, i.e., they would move toward the nozzle upon breakup, which is undesirable. In the second breakup regime, where We >Wec2, not only are DOD drops formed, but they do so with positive velocities.

  18. The stability of the axially symmetric pendent drop

    NASA Technical Reports Server (NTRS)

    Wente, H. C.

    1982-01-01

    The axially symmetric pendent drop as it occurs in three different physical settings is analyzed: Problem A with constant pressure and a fixed circular opening (the siphon); Problem B with constant volume and a fixed circular opening (the medicine dropper); and Problem C with prescribed volume and a constant angle of contact with a horizontal plate. As examples, the results are verified. For Problem B it is shown that if the opening is small enough to support a stable pendent drop with a bulge, then as the exposed volume is increased, stable pendent drops with both a neck and a bulge will be formed. For Problem C it is shown that with increasing volume the profile curves for the family of stable pendent drops will develop an inflection point before instability arises.

  19. Electrostatic Liquid-Drop-Levitation System

    NASA Technical Reports Server (NTRS)

    Rhim, Won Kyu; Chung, San Kun; Hyson, Michael T.; Elleman, Daniel D.

    1988-01-01

    Electrostatic levitator has levitated drops of liquid up to 4 mm in diameter while maintaining spherical drop shapes. Stable levitation of spherical drops valuable in experiments involving super-cooling, solidification, and crystal growth.

  20. Forced Oscillations of Supported Drops

    NASA Technical Reports Server (NTRS)

    Wilkes, Edward D.; Basaran, Osman A.

    1996-01-01

    Oscillations of supported liquid drops are the subject of wide scientific interest, with applications in areas as diverse as liquid-liquid extraction, synthesis of ceramic powders, growing of pure crystals in low gravity, and measurement of dynamic surface tension. In this research, axisymmetric forced oscillations of arbitrary amplitude of viscous liquid drops of fixed volume which are pendant from or sessile on a rod with a fixed or moving contact line and surrounded by an inviscid ambient gas are induced by moving the rod in the vertical direction sinusiodally in time. In this paper, a preliminary report is made on the computational analysis of the oscillations of supported drops that have 'clean' interfaces and whose contact lines remain fixed throughout their motions. The relative importance of forcing to damping can be increased by either increasing the amplitude of rod motion A or Reynolds number Re. It is shown that as the ratio of forcing to damping rises, for drops starting from an initial rest state a sharp increase in deformation can occur when they are forced to oscillate in the vicinity of their resonance frequencies, indicating the incipience of hysteresis. However, it is also shown that the existence of a second stable limit cycle and the occurrence of hysteresis can be observed if the drop is subjected to a so-called frequency sweep, where the forcing frequency is first increased and then decreased over a suitable range. Because the change in drop deformation response is abrupt in the vicinity of the forcing frequencies where hysteresis occurs, it should be possible to exploit the phenomenon to accurately measure the viscosity and surface tension of the drop liquid.

  1. Porosity evolution of upper Miocene reefs, Almeria Province, Southern Spain

    SciTech Connect

    Armstrong, A.K.; Snavely, P.D. Jr.; Addicott, W.O.

    1980-02-01

    In the reef cores and fore-reef breccia beds, porosity in both primary and postdepositional. Primary porosity is of three types: (a) boring clam holes in the scleractinian coral heads, cemented reef rocks, and breccias; (b) intraparticle porosity within the corals, Halimeda plates, and vermetid worm tubes; and (c) interparticle porosity between bioclastic fragments and in the reef breccia. Postdepositional moldic porosity was formed by the solution of aragonitic material such as molluscan and coral fragments. The Polomo reef carbonate rocks have high porosity and permeability, and retain a great amount of depositional porosity. Pores range in size from a few micrometers to 30 cm. The extensive intercrystalline porosity and high permeability resulted from dolomitization of micritic matrix. Some porosity reduction has occured by incomplete and partial sparry calcite infilling of interparticular, moldic, and intercrystalline voids. The high porosity and permeability of these reefs make them important targets for petroleum exploration in the western Mediterranean off southern Spain. In these offshore areas in the subsuface the volcanic ridge and the Plomo reef complex are locally onlapped or overlapped by 350 m or more of Miocene and Pliocene fine-grained sedimentary rocks. The possibility exists that the buried Plomo reef deposits may form traps for oil and gas in the offshore areas southwest of the type locality. Stratigraphic traps also may occur where the Neogene sequence above the Plomo reef complex onlaps the volcanic ridge. 17 figures.

  2. Solidification of Drops in the MSFC Drop Tube

    NASA Technical Reports Server (NTRS)

    Brush, Lucien N.

    1998-01-01

    Silver drops (99.9%, 7 mm diameter) were levitated, melted, and released to fall through the Marshall Space Flight Center's 105 m drop tube in an He-6% H atmosphere at 170 degrees superheat. The extent of solidification during the approx. 4.6 s of free fall time prior to impact was measured experimentally and computed numerically using a newly developed solidification heat transfer model. Comparison of the experimental observation of the fraction of liquid transformed with the numerical solutions showed reasonable agreement. Possible modifications of the model, in an attempt to close the gap between the experiment and the model comparison are discussed.

  3. Review on drop towers and long drop tubes

    NASA Technical Reports Server (NTRS)

    Bayuzick, R. J.; Hofmeister, W. H.; Robinson, M. B.

    1987-01-01

    A drop tube is an enclosure in which a molten sample can be solidified while falling; three such large tubes are currently in existence, all at NASA research facilities, and are engaged in combustion and fluid physics-related experiments rather than in materials research. JPL possesses smaller tubes, one of which can be cryogenically cooled to produce glass and metal microshells. A new small drop tube will soon begin operating at NASA Lewis that is equipped with four high-speed two-color pyrometers spaced equidistantly along the column.

  4. Designed porosity materials in nuclear reactor components

    DOEpatents

    Yacout, A. M.; Pellin, Michael J.; Stan, Marius

    2016-09-06

    A nuclear fuel pellet with a porous substrate, such as a carbon or tungsten aerogel, on which at least one layer of a fuel containing material is deposited via atomic layer deposition, and wherein the layer deposition is controlled to prevent agglomeration of defects. Further, a method of fabricating a nuclear fuel pellet, wherein the method features the steps of selecting a porous substrate, depositing at least one layer of a fuel containing material, and terminating the deposition when the desired porosity is achieved. Also provided is a nuclear reactor fuel cladding made of a porous substrate, such as silicon carbide aerogel or silicon carbide cloth, upon which layers of silicon carbide are deposited.

  5. Surfactant and nonlinear drop dynamics in microgravity

    NASA Astrophysics Data System (ADS)

    Jankovsky, Joseph Charles

    2000-11-01

    Large amplitude drop dynamics in microgravity were conducted during the second United States Microgravity Laboratory mission carried onboard the Space Shuttle Columbia (20 October-5 November 1995). Centimeter- sized drops were statically deformed by acoustic radiation pressure and released to oscillate freely about a spherical equilibrium. Initial aspect ratios of up to 2.0 were achieved. Experiments using pure water and varying aqueous concentrations of Triton-X 100 and bovine serum albumin (BSA) were performed. The axisymmetric drop shape oscillations were fit using the degenerate spherical shape modes. The frequency and decay values of the fundamental quadrupole and fourth order shape mode were analyzed. Several large amplitude nonlinear oscillation dynamics were observed. Shape entrainment of the higher modes by the fundamental quadrupole mode occurred. Amplitude- dependent effects were observed. The nonlinear frequency shift, where the oscillation frequency is found to decrease with larger amplitudes, was largely unaffected by the presence of surfactants. The percentage of time spent in the prolate shape over one oscillation cycle was found to increase with oscillation amplitude. This prolate shape bias was also unaffected by the addition of surfactants. These amplitude-dependent effects indicate that the nonlinearities are a function of the bulk properties and not the surface properties. BSA was found to greatly enhance the surface viscoelastic properties by increasing the total damping of the oscillation, while Triton had only a small influence on damping. The surface concentration of BSA was found to be diffusion-controlled over the time of the experiments, while the Triton diffusion rate was very rapid. Using the experimental frequency and decay values, the suface viscoelastic properties of surface dilatational viscosity ( ks ) and surface shear viscosity ( ms ) were found for varying surfactant concentrations using the transcendental equation of Lu

  6. Carbonate porosity versus depth: a predictable relation for south Florida.

    USGS Publications Warehouse

    Schmoker, J.W.; Halley, R.B.

    1982-01-01

    Examines the porosity of limestones and dolomites in the south Florida basin. Porosity data are derived from wire-line measurements which sample large volumes of rock, relative to petrographic methods, and can be examined at vertical scales approaching those of aquifers and hydrocarbon reservoirs. Investigation depths range from the surface to about 5500m. Curves of porosity versus depth, reflecting large-scale porosity-loss processes in the subsurface, are derived for a composite carbonate section and for carbonate strata of different ages and compositions.-from Authors

  7. EFFECTIVE POROSITY IMPLIES EFFECTIVE BULK DENSITY IN SORBING SOLUTE TRANSPORT

    SciTech Connect

    Flach, G.

    2012-02-27

    The concept of an effective porosity is widely used in solute transport modeling to account for the presence of a fraction of the medium that effectively does not influence solute migration, apart from taking up space. This non-participating volume or ineffective porosity plays the same role as the gas phase in single-phase liquid unsaturated transport: it increases pore velocity, which is useful towards reproducing observed solute travel times. The prevalent use of the effective porosity concept is reflected by its prominent inclusion in popular texts, e.g., de Marsily (1986), Fetter (1988, 1993) and Zheng and Bennett (2002). The purpose of this commentary is to point out that proper application of the concept for sorbing solutes requires more than simply reducing porosity while leaving other material properties unchanged. More specifically, effective porosity implies the corresponding need for an effective bulk density in a conventional single-porosity model. The reason is that the designated non-participating volume is composed of both solid and fluid phases, both of which must be neglected for consistency. Said another way, if solute does not enter the ineffective porosity then it also cannot contact the adjoining solid. Conceptually neglecting the fluid portion of the non-participating volume leads to a lower (effective) porosity. Likewise, discarding the solid portion of the non-participating volume inherently leads to a lower or effective bulk density. In the author's experience, practitioners virtually never adjust bulk density when adopting the effective porosity approach.

  8. Porosity, permeability and fluid flow in the YellowstoneGeothermal System, Wyoming

    SciTech Connect

    Dobson, Patrick F.; Kneafsey, Timothy J.; Hulen, Jeffrey; Simmons, Ardyth

    2002-03-29

    Cores from two of 13 U.S. Geological Survey (USGS) research holes at Yellowstone National Park (Y-5 and Y-8) were evaluated to characterize lithology, texture, alteration, and the degree and nature of fracturing and veining. Porosity and matrix permeability measurements and petrographic examination of the cores were used to evaluate the effects of lithology and hydrothermal alteration on porosity and permeability. The intervals studied in these two core holes span the conductive zone and the upper portion of the convective geothermal reservoir. Variations in porosity and matrix permeability observed in the Y-5 and Y-8 cores are primarily controlled by lithology. Y-8 intersects three distinct lithologies: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous ash-flow tuff. The sandstone typically has high permeability and porosity, and the tuff has very high porosity and moderate permeability, while the perlitic lava has very low porosity and is essentially impermeable. Hydrothermal self-sealing appears to have generated localized permeability barriers within the reservoir. Changes in pressure and temperature in Y-8 correspond to a zone of silicification in the volcaniclastic sandstone just above the contact with the perlitic rhyolite; this silicification has significantly reduced porosity and permeability. In rocks with inherently low matrix permeability (such as densely welded ash-flow tuff), fluid flow is controlled by the fracture network. The Y-5 core hole penetrates a thick intracaldera section of the0.6 Ma Lava Creek ash-flow tuff. In this core, the degree of welding appears to be responsible for most of the variations in porosity, matrix permeability, and the frequency of fractures and veins. Fractures are most abundant within the more densely welded sections of the tuff. However, the most prominent zones of fracturing and mineralization are associated with hydrothermal breccias within densely welded portions of the tuff. These breccia

  9. Electrode porosity and effective electrocatalyst activity in electrode-membrane-assemblies (MEAs) of PEMFCs

    SciTech Connect

    Fischer, A.; Wendt, H.

    1996-12-31

    New production technologies of membrane-electrode-assemblies for PEWCs which ensure almost complete catalyst utilization by {open_quotes}wetting{close_quotes} the internal catalyst surface with the ionomeric electrolyte, allow for a reduction of Pt-loadings from prior 4 mg cm{sup -2} to now less than 0.5 mg cm{sup -2}. Such electrodes are not thicker than from 5 to 10 {mu}m. Little has been published hitherto about the detailed micromorphology of such electrodes and the role of electrode porosity on electrode performance. It is well known, that the porosity of thicker fuel cell electrodes, e.g. of PAFC or AFC electrodes is decisive for their performance. Therefore the issue of this investigation is to measure and to modify the porosity of electrodes prepared by typical MEA production procedures and to investigate the influence of this porosity on the effective catalyst activity for cathodic reduction of oxygen from air in membrane cells. It may be anticipated that any mass transfer hindrance of gaseous reactants into porous electrodes would manifest itself rather in the conversion of dilute gases than in the conversion of pure gases (e.g. neat oxygen). Therefore in this investigation the performance of membrane cell cathodes with non pressurized air had been compared to that with neat oxygen at cathodes which had a relatively low Pt-loading of 0.15 mg cm{sup -2}.

  10. A Quantitative Model of Keyhole Instability Induced Porosity in Laser Welding of Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Chen, Weidong; Wang, Wen

    2014-06-01

    Quantitative prediction of the porosity defects in deep penetration laser welding has generally been considered as a very challenging task. In this study, a quantitative model of porosity defects induced by keyhole instability in partial penetration CO2 laser welding of a titanium alloy is proposed. The three-dimensional keyhole instability, weld pool dynamics, and pore formation are determined by direct numerical simulation, and the results are compared to prior experimental results. It is shown that the simulated keyhole depth fluctuations could represent the variation trends in the number and average size of pores for the studied process conditions. Moreover, it is found that it is possible to use the predicted keyhole depth fluctuations as a quantitative measure of the average size of porosity. The results also suggest that due to the shadowing effect of keyhole wall humps, the rapid cooling of the surface of the keyhole tip before keyhole collapse could lead to a substantial decrease in vapor pressure inside the keyhole tip, which is suggested to be the mechanism by which shielding gas enters into the porosity.

  11. 49 CFR 178.810 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.810 Section 178.810 Transportation... Drop test. (a) General. The drop test must be conducted for the qualification of all IBC design types... the drop test. (1) Metal, rigid plastic, and composite IBCs intended to contain solids must be...

  12. 49 CFR 178.1045 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.1045 Section 178.1045... Containers § 178.1045 Drop test. (a) General. The drop test must be conducted for the qualification of all... subpart. (b) Special preparation for the drop test. Flexible Bulk Containers must be filled to...

  13. 49 CFR 178.965 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.965 Section 178.965 Transportation... Packagings § 178.965 Drop test. (a) General. The drop test must be conducted for the qualification of all...) Special preparation for the drop test. Large Packagings must be filled in accordance with § 178.960....

  14. 49 CFR 178.603 - Drop test.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Drop test. 178.603 Section 178.603 Transportation... Packagings and Packages § 178.603 Drop test. (a) General. The drop test must be conducted for the... than flat drops, the center of gravity of the test packaging must be vertically over the point...

  15. Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former

    NASA Astrophysics Data System (ADS)

    Medřický, Jan; Curry, Nicholas; Pala, Zdenek; Vilemova, Monika; Chraska, Tomas; Johansson, Jimmy; Markocsan, Nicolaie

    2015-04-01

    Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

  16. Ultrasonic atomization of liquids in drop-chain acoustic fountains

    PubMed Central

    Simon, Julianna C.; Sapozhnikov, Oleg A.; Khokhlova, Vera A.; Crum, Lawrence A.; Bailey, Michael R.

    2015-01-01

    When focused ultrasound waves of moderate intensity in liquid encounter an air interface, a chain of drops emerges from the liquid surface to form what is known as a drop-chain fountain. Atomization, or the emission of micro-droplets, occurs when the acoustic intensity exceeds a liquid-dependent threshold. While the cavitation-wave hypothesis, which states that atomization arises from a combination of capillary-wave instabilities and cavitation bubble oscillations, is currently the most accepted theory of atomization, more data on the roles of cavitation, capillary waves, and even heat deposition or boiling would be valuable. In this paper, we experimentally test whether bubbles are a significant mechanism of atomization in drop-chain fountains. High-speed photography was used to observe the formation and atomization of drop-chain fountains composed of water and other liquids. For a range of ultrasonic frequencies and liquid sound speeds, it was found that the drop diameters approximately equalled the ultrasonic wavelengths. When water was exchanged for other liquids, it was observed that the atomization threshold increased with shear viscosity. Upon heating water, it was found that the time to commence atomization decreased with increasing temperature. Finally, water was atomized in an overpressure chamber where it was found that atomization was significantly diminished when the static pressure was increased. These results indicate that bubbles, generated by either acoustic cavitation or boiling, contribute significantly to atomization in the drop-chain fountain. PMID:25977591

  17. Getting the Drop on Sediment

    ERIC Educational Resources Information Center

    Galindez, Peter

    1977-01-01

    In this exercise, students examine Aristotle's weight hypothesis by testing variously shaped marble chips. These chips are weighed and dropped down a water tube. Average fall times and weights are recorded and graphed. Students are asked to apply this information to rock and soil deposition by streams. (MA)

  18. Egg Drop: An Invention Workshop

    ERIC Educational Resources Information Center

    McCormack, Alan J.

    1973-01-01

    Describes an activity designed to stimulate elementary and junior high students to become actively engaged in thinking creatively rather than only analytically, convergently, or repetitively. The activity requires students to devise means of dropping an egg from a height without it breaking. (JR)

  19. ``Quantum'' interference with bouncing drops

    NASA Astrophysics Data System (ADS)

    Bohr, Tomas; Andersen, Anders; Madsen, Jacob; Reichelt, Christian; Lautrup, Benny; Ellegaard, Clive; Levinsen, Mogens

    2013-11-01

    In a series of recent papers (most recently) Yves Couder and collaborators have explored the dynamics of walking drops on the surface of a vibrated bath of silicon oil and have demonstrated a close analogy to quantum phenomena. The bouncing drop together with the surface wave that it excites seems to be very similar to the pilot wave envisaged by de Broglie for quantum particles. In particular, have studied a double slit experiment with walking drops, where an interference pattern identical to the quantum version is found even though it is possible to follow the orbits of the drops and unambigously determine which slit it goes through, something which in quantum mechanics would be ruled out by the Heisenberg uncertainly relations. We have repeated the experiment and present a somewhat more complicated picture. Theoretically, we study a Schrödinger equation with a source term originating from a localised ``particle'' being simultaneously guided by the wave. We present simple solutions to such a field theory and discuss the fundamental difficulties met by such a theory in order to comply with quantum mechanics.

  20. Combining spray nozzle simulators with meshes: characterization of rainfall intensity and drop properties

    NASA Astrophysics Data System (ADS)

    Carvalho, Sílvia C. P.; de Lima, João L. M. P.; de Lima, M. Isabel P.

    2013-04-01

    Rainfall simulators can be a powerful tool to increase our understanding of hydrological and geomorphological processes. Nevertheless, rainfall simulators' design and operation might be rather demanding, for achieving specific rainfall intensity distributions and drop characteristics. The pressurized simulators have some advantages over the non-pressurized simulators: drops do not rely on gravity to reach terminal velocity, but are sprayed out under pressure; pressurized simulators also yield a broad range of drop sizes in comparison with drop-formers simulators. The main purpose of this study was to explore in the laboratory the potential of combining spray nozzle simulators with meshes in order to change rainfall characteristics (rainfall intensity and diameters and fall speed of drops). Different types of spray nozzles were tested, such as single full-cone and multiple full-cone nozzles. The impact of the meshes on the simulated rain was studied by testing different materials (i.e. plastic and steel meshes), square apertures and wire thicknesses, and different vertical distances between the nozzle and the meshes underneath. The diameter and fall speed of the rain drops were measured using a Laser Precipitation Monitor (Thies Clima). The rainfall intensity range and coefficients of uniformity of the sprays and the drop size distribution, fall speed and kinetic energy were analysed. Results show that when meshes intercept drop trajectories the spatial distribution of rainfall intensity and the drop size distribution are affected. As the spray nozzles generate typically small drop sizes and narrow drop size distributions, meshes can be used to promote the formation of bigger drops and random their landing positions.

  1. Ultrahigh porosity in metal-organic frameworks.

    PubMed

    Furukawa, Hiroyasu; Ko, Nakeun; Go, Yong Bok; Aratani, Naoki; Choi, Sang Beom; Choi, Eunwoo; Yazaydin, A Ozgür; Snurr, Randall Q; O'Keeffe, Michael; Kim, Jaheon; Yaghi, Omar M

    2010-07-23

    Crystalline solids with extended non-interpenetrating three-dimensional crystal structures were synthesized that support well-defined pores with internal diameters of up to 48 angstroms. The Zn4O(CO2)6 unit was joined with either one or two kinds of organic link, 4,4',4''-[benzene-1,3,5-triyl-tris(ethyne-2,1-diyl)]tribenzoate (BTE), 4,4',44''-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate (BBC), 4,4',44''-benzene-1,3,5-triyl-tribenzoate (BTB)/2,6-naphthalenedicarboxylate (NDC), and BTE/biphenyl-4,4'-dicarboxylate (BPDC), to give four metal-organic frameworks (MOFs), MOF-180, -200, -205, and -210, respectively. Members of this series of MOFs show exceptional porosities and gas (hydrogen, methane, and carbon dioxide) uptake capacities. For example, MOF-210 has Brunauer-Emmett-Teller and Langmuir surface areas of 6240 and 10,400 square meters per gram, respectively, and a total carbon dioxide storage capacity of 2870 milligrams per gram. The volume-specific internal surface area of MOF-210 (2060 square meters per cubic centimeter) is equivalent to the outer surface of nanoparticles (3-nanometer cubes) and near the ultimate adsorption limit for solid materials. PMID:20595583

  2. Porosity and mechanical properties of zirconium ceramics

    NASA Astrophysics Data System (ADS)

    Buyakova, S.; Sablina, T.; Kulkov, S.

    2015-11-01

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO2(MgO), ZrO2(Y2O3) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO2 powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO2 grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  3. Whisker Formation in Porosity in Al Alloys

    NASA Astrophysics Data System (ADS)

    Griffiths, William David; Elsayed, Ahmed; El-Sayed, Mahmoud Ahmed

    2016-09-01

    An examination of the fracture surfaces of tensile test bars from Al alloy castings held in the liquid state for up to 20 minutes revealed porosity which in some cases contained whisker-like features. Energy-dispersive X-ray analysis in a SEM suggested that these might be oxide whiskers forming in an oxide-related pore or double oxide film defect. Such entrainment defects (also known as bifilms) may entrap a small amount of the local atmosphere when they form and become incorporated into the liquid metal. This atmosphere may be predominantly air, which then subsequently reacts with the surrounding melt, firstly by reaction with oxygen and secondly by reaction with nitrogen. A CFD model of the heat distribution associated with the reactions between the interior atmosphere of a double oxide film defect and the surrounding liquid alloy suggested that highly localized increases in temperature, up to about 2000 K to 5000 K (1727 °C to 4727 °C), could occur, over a scale of a few hundred micrometers. Such localized increases in temperature might lead to the evaporation or disassociation of oxide within the pore, followed by condensation, to form the whisker structures observed. Hydrogen might also be expected to diffuse into the bifilm and may play a role in the chemical reactions associated with the development of the bifilm.

  4. Tunable-Porosity Membranes From Discrete Nanoparticles

    PubMed Central

    Marchetti, Patrizia; Mechelhoff, Martin; Livingston, Andrew G.

    2015-01-01

    Thin film composite membranes were prepared through a facile single-step wire-wound rod coating procedure in which internally crosslinked poly(styrene-co-butadiene) polymer nanoparticles self-assembled to form a thin film on a hydrophilic ultrafiltration support. This nanoparticle film provided a defect-free separation layer 130–150 nm thick, which was highly permeable and able to withstand aggressive pH conditions beyond the range of available commercial membranes. The nanoparticles were found to coalesce to form a rubbery film when heated above their glass transition temperature (Tg). The retention properties of the novel membrane were strongly affected by charge repulsion, due to the negative charge of the hydroxyl functionalized nanoparticles. Porosity was tuned by annealing the membranes at different temperatures, below and above the nanoparticle Tg. This enabled fabrication of membranes with varying performance. Nanofiltration properties were achieved with a molecular weight cut-off below 500 g mol−1 and a low fouling tendency. Interestingly, after annealing above Tg, memory of the interstitial spaces between the nanoparticles persisted. This memory led to significant water permeance, in marked contrast to the almost impermeable films cast from a solution of the same polymer. PMID:26626565

  5. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Buyakova, S. Kulkov, S.; Sablina, T.

    2015-11-17

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO{sub 2}(MgO), ZrO{sub 2}(Y{sub 2}O{sub 3}) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO{sub 2} powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO{sub 2} grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  6. Tunable-Porosity Membranes From Discrete Nanoparticles

    NASA Astrophysics Data System (ADS)

    Marchetti, Patrizia; Mechelhoff, Martin; Livingston, Andrew G.

    2015-12-01

    Thin film composite membranes were prepared through a facile single-step wire-wound rod coating procedure in which internally crosslinked poly(styrene-co-butadiene) polymer nanoparticles self-assembled to form a thin film on a hydrophilic ultrafiltration support. This nanoparticle film provided a defect-free separation layer 130-150 nm thick, which was highly permeable and able to withstand aggressive pH conditions beyond the range of available commercial membranes. The nanoparticles were found to coalesce to form a rubbery film when heated above their glass transition temperature (Tg). The retention properties of the novel membrane were strongly affected by charge repulsion, due to the negative charge of the hydroxyl functionalized nanoparticles. Porosity was tuned by annealing the membranes at different temperatures, below and above the nanoparticle Tg. This enabled fabrication of membranes with varying performance. Nanofiltration properties were achieved with a molecular weight cut-off below 500 g mol-1 and a low fouling tendency. Interestingly, after annealing above Tg, memory of the interstitial spaces between the nanoparticles persisted. This memory led to significant water permeance, in marked contrast to the almost impermeable films cast from a solution of the same polymer.

  7. Tunable-Porosity Membranes From Discrete Nanoparticles.

    PubMed

    Marchetti, Patrizia; Mechelhoff, Martin; Livingston, Andrew G

    2015-12-02

    Thin film composite membranes were prepared through a facile single-step wire-wound rod coating procedure in which internally crosslinked poly(styrene-co-butadiene) polymer nanoparticles self-assembled to form a thin film on a hydrophilic ultrafiltration support. This nanoparticle film provided a defect-free separation layer 130-150 nm thick, which was highly permeable and able to withstand aggressive pH conditions beyond the range of available commercial membranes. The nanoparticles were found to coalesce to form a rubbery film when heated above their glass transition temperature (Tg). The retention properties of the novel membrane were strongly affected by charge repulsion, due to the negative charge of the hydroxyl functionalized nanoparticles. Porosity was tuned by annealing the membranes at different temperatures, below and above the nanoparticle Tg. This enabled fabrication of membranes with varying performance. Nanofiltration properties were achieved with a molecular weight cut-off below 500 g mol(-1) and a low fouling tendency. Interestingly, after annealing above Tg, memory of the interstitial spaces between the nanoparticles persisted. This memory led to significant water permeance, in marked contrast to the almost impermeable films cast from a solution of the same polymer.

  8. Porosity control in mesoporous polymers using CO2-swollen block copolymer micelles as templates and their use as catalyst supports.

    PubMed

    Peng, Li; Zhang, Jianling; Yang, Shuliang; Han, Buxing; Sang, Xinxin; Liu, Chengcheng; Yang, Guanying

    2014-10-14

    Mesoporous polymers with tunable large mesopores and thin mesopore walls were synthesized through a CO2-swollen micelle templating route. The mesopore size and porosity properties of the polymers can be easily modulated by adjusting CO2 pressure. The as-synthesized mesocellular polymers are excellent candidate supports for preparing heterogeneous catalysts.

  9. Casting Porosity-Free Grain Refined Magnesium Alloys

    SciTech Connect

    Schwam, David

    2013-08-12

    The objective of this project was to identify the root causes for micro-porosity in magnesium alloy castings and recommend remedies that can be implemented in production. The findings confirm the key role played by utilizing optimal gating and risering practices in minimizing porosity in magnesium castings. 

  10. The Porosity of Eros and Implications for Its Internal Structure

    NASA Technical Reports Server (NTRS)

    Wilkison, S. L.; Robinson, M. S.; Thomas, P. C.; Veverka, J.; McCoy, T. J.; Murchie, S. L.; Prockter, L.; Yeomans, D.

    2001-01-01

    We estimate the porosity of Eros to be between 21-33%. Based on this porosity range and morphologic observations of the surface, we suggest that the asteroid is heavily fractured (but not a rubble pile). Additional information is contained in the original extended abstract.

  11. Water uptake in biochars: The roles of porosity and hydrophobicity

    EPA Science Inventory

    We assessed the effects of porosity and hydrophobicity on water uptake by biochars. Biochars were produced from two feedstocks (hazelnut shells and Douglas fir chips) at three production temperatures (370 °C, 500 °C, and 620 °C). To distinguish the effects of porosity from the ...

  12. Modeling variations of medium porosity in rotating drum biofilter.

    PubMed

    Yang, Chunping; Chen, Hong; Zeng, Guangming; Yu, Guanlong; Liu, Xianfeng; Zhang, Xiaoming

    2009-01-01

    Rotating drum biofilters (RDBs) mounted with reticulated polyurethane sponge media has showed high removal efficiencies over a long period of time when used for volatile organic compound (VOC) removal. Due to the accumulation of biomass within the sponge medium, the porosity of a filter bed usually changes dynamically, which makes it difficult to predict and to control. In this paper, the porosity of a multi-layer RDB bed was investigated by a diffusion-reaction model in which biofilm growth and decay were taken into account at the pore scale of the sponge medium. Temporal and spatial changes of porosity were studied under various organic loadings and gas empty bed contact times (EBCTs). The porosity of the biofilter bed was assumed to be a function of biofilm thickness, and all the pores were assumed to be uniform. Toluene was selected as the model VOC. The model was solved using numerical methods through the MATLAB software. Results show that the porosity decreased with increased time of operation, increased toluene loading, or decreased gas EBCT value. The porosity in the outermost medium layer was less than that in the inner medium layers. Toluene removal efficiencies and porosities calculated from this model correlated with the experimental data well. Porosity variation was proposed to be an indicator for prediction of biofilter performance in biofilters as a consequence. PMID:18951611

  13. Self-assembly of nanoparticles in evaporating particle-laden emulsion drops

    NASA Astrophysics Data System (ADS)

    Pack, Min; Yang, Xin; Sun, Ying

    2014-11-01

    In this study, we demonstrate the scalable fabrication of nanostructures (e.g., nanomesh and nanoring arrays) via inkjet printing of oil-in-water emulsion drops containing nanoparticles in water. Nanoscale oil drops dispersed in water are used here as templates for assembly of nanoparticles on a substrate. The effect of oil vapor pressure on particle deposition morphologies is studied by using a variety of oils. For oil drops with a lower vapor pressure, non-uniform evaporation rate along the air-water interface drives dispersed oil drops to move and accumulate near the air/water/substrate contact line. These oil drops remain on the substrate while water is evaporating enabling nanoparticles to self-assemble into nanomeshes. While keeping the same oil concentration, oil drops with a higher vapor pressure completely evaporates near the contact line before water dries out, leading to nanoparticle deposition of coffee-ring structures. If nanoparticles are confined inside the dispersed oil drops, nanoring arrays are formed as the emulsion evaporates. The characteristics of the nanomeshes and nanorings are controlled by tuning the size and concentration of oil drops and nanoparticles, substrate wettability, surfactant concentration, and vapor pressure of oil.

  14. Horizontal Drop of 21- PWR Waste Package

    SciTech Connect

    A.K. Scheider

    2007-01-31

    The objective of this calculation is to determine the structural response of the waste package (WP) dropped horizontally from a specified height. The WP used for that purpose is the 21-Pressurized Water Reactor (PWR) WP. The scope of this document is limited to reporting the calculation results in-terms of stress intensities. This calculation is associated with the WP design and was performed by the Waste Package Design group in accordance with the ''Technical Work Plan for: Waste Package Design Description for LA'' (Ref. 16). AP-3.12Q, ''Calculations'' (Ref. 1 1) is used to perform the calculation and develop the document. The sketches attached to this calculation provide the potential dimensions and materials for the 21-PWR WP design.

  15. Bubble and Drop Nonlinear Dynamics experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Bubble and Drop Nonlinear Dynamics (BDND) experiment was designed to improve understanding of how the shape and behavior of bubbles respond to ultrasound pressure. By understanding this behavior, it may be possible to counteract complications bubbles cause during materials processing on the ground. This 12-second sequence came from video downlinked from STS-94, July 5 1997, MET:3/19:15 (approximate). The BDND guest investigator was Gary Leal of the University of California, Santa Barbara. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced fluid dynamics experiments will be a part of investigations plarned for the International Space Station. (189KB JPEG, 1293 x 1460 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300163.html.

  16. Probing soil and aquifer material porosity with nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Hinedi, Z. R.; Kabala, Z. J.; Skaggs, T. H.; Borchardt, D. B.; Lee, R. W. K.; Chang, A. C.

    1993-12-01

    Nuclear magnetic resonance relaxation measurements were used to identify different characteristic porosity domains in soil and aquifer materials. The porosity distribution can be inferred from these measurements by a regularization method applicable to any nuclear magnetic resonance (NMR) relaxation, or by an analytic method applicable only to multiexponential relaxations (D. Orazio et al., 1989). The porosity distribution obtained from NMR relaxation measurements strongly depends on the pore shape factor. For the Borden aquifer material, both the regularized and the analytic pore size distribution obtained from NMR relaxation measurements are consistent with those obtained by Ball et al. (1990) using Hg porosimetry and N2 adsorption. For the Eustis and the Webster soils, the measured porosity domains are qualitatively consistent with those expected based on their respective composition. Our findings suggest that due to the long time required to saturate fine pores, NMR measurements of porosity distribution that are collected at short saturation times are biased toward larger pore sizes.

  17. Advanced Aerodynamic Design of Passive Porosity Control Effectors

    NASA Technical Reports Server (NTRS)

    Hunter, Craig A.; Viken, Sally A.; Wood, Richard M.; Bauer, Steven X. S.

    2001-01-01

    This paper describes aerodynamic design work aimed at developing a passive porosity control effector system for a generic tailless fighter aircraft. As part of this work, a computational design tool was developed and used to layout passive porosity effector systems for longitudinal and lateral-directional control at a low-speed, high angle of attack condition. Aerodynamic analysis was conducted using the NASA Langley computational fluid dynamics code USM3D, in conjunction with a newly formulated surface boundary condition for passive porosity. Results indicate that passive porosity effectors can provide maneuver control increments that equal and exceed those of conventional aerodynamic effectors for low-speed, high-alpha flight, with control levels that are a linear function of porous area. This work demonstrates the tremendous potential of passive porosity to yield simple control effector systems that have no external moving parts and will preserve an aircraft's fixed outer mold line.

  18. Results from a new Cocks-Ashby style porosity model

    NASA Astrophysics Data System (ADS)

    Barton, Nathan

    2015-06-01

    A new porosity evolution model will be described, along with preliminary results. The formulation makes use of a Cocks-Ashby style treatment of porosity kinetics that includes rate dependent flow in the mechanics of porosity growth. The porosity model is implemented in a framework that allows for a variety of strength models to be used for the matrix material, including ones with significant changes in rate sensitivity as a function of strain rate. Results of the effect of changing strain rate sensitivity on porosity evolution will be shown. The overall constitutive model update involves the coupled solution of a system of nonlinear equations - efficiency and robustness of the numerical implementation are significant issues. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-ABS-666658).

  19. Noninvasive porosity measurement of biconvex tablets using terahertz pulses.

    PubMed

    Bawuah, Prince; Ervasti, Tuomas; Tan, Nicholas; Zeitler, J Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik

    2016-07-25

    Biconvex pharmaceutical microcrystalline cellulose (MCC) compacts were investigated by the detection of terahertz (THz) pulse delay in the transmission measurement mode. The dimensions of the tablets were kept as constants but the porosity was a priori known variable. It is shown that the porosity of the biconvex compact has a linear correlation with the THz pulse delay. By constructing a calibration line between these two parameters (i.e. porosity and THz pulse delay), it is possible to non-invasively detect porosity of biconvex tablets. We suggest that this preliminary study could be the starting point of in-depth future studies on the screening of porosity and related properties of real biconvex pharmaceutical tablets using terahertz sensing techniques. PMID:27289013

  20. Changes in pit membrane porosity due to deflection and stretching: the role of vestured pits.

    PubMed

    Choat, Brendan; Jansen, Steven; Zwieniecki, Maciej A; Smets, Erik; Holbrook, N Michele

    2004-07-01

    The effect of increasing pressure difference (DeltaP) on intervessel pit membrane porosity was studied in two angiosperm tree species with differing pit architecture. Fraxinus americana L. possesses typical angiosperm bordered pit structure while Sophora japonica L. exhibits well-developed vestures in intervessel pit chambers. It was hypothesized (a) that large DeltaP across intervessel pits would cause the deflection of pit membranes in the stems of F. americana resulting in significant increases in porosity and thus lower cavitation thresholds, and (b) that the presence of vestures would prevent the deflection of pit membranes in S. japonica. To determine if the porosity of pit membranes increased under mechanical stress, suspensions of colloidal gold, 5 nm and 20 nm in diameter, were perfused across intervessel pit membranes at DeltaP ranging from 0.25 MPa to 6.0 MPa. The effect of increasing DeltaP on membrane porosity was also tested by comparing air seeding thresholds (Pa) in stems perfused with water or a solution with lower surface tension. Air seeding and colloidal gold experiments indicated that pit membrane porosity increased significantly with DeltaP in F. americana. In S. japonica, increases in permeability to colloidal gold with DeltaP were small and maximum pore diameters predicted from Pa were independent of DeltaP, suggesting that vestures limited the degree to which the membrane can be deflected from the centre of the pit cavity. This provides the first experimental evidence that vestures reduce the probability of air seeding through pit membranes. PMID:15181107

  1. The secondary porosity trick: Arkose to quartzite in the North Sea

    SciTech Connect

    Haszeldine, S.; Wilkinson, M.; Darby, D.

    1996-12-31

    Observations of mineralogy, texture, poroperm, stratigraphy and overpressure compiled from major reservoirs of the North Sea at different burial, structural and pressure settings, indicate to us that secondary porosity has continued to form at depths of 10-18,000ft (3-6km). This has resulted in strata-bound economic improvements to reservoir quality by as much as 8% and 2,000mD. The Brent Sandstone Group shows a decrease of feldspar with depth from 20% to 5%; clay content does not increase; identifiable secondary porosity does not increase. The HPHT Fulmar Sandstone shows a decrease of feldspar from 40% to 10%; aluminum (clay) content decreases; identifiable secondary porosity does not increase. Differences within these two sandstone Groups can not be explained by depositional variations. The Brea Formation shows loss of feldspar and calcite from 10% to 5%; only minimal clay is present; secondary porosity is often present, and is strata-bound. In this last case, an adjacent oilfield contains oil leaked up-dip from the deeper sandstones. This West Brae oilfield contains up to 13% kaolin clay, a big excess over the usual 2% expected for its present depth. The deep sand has lost clay, the shallow sand has imported clay. We conclude that feldspars continue to dissolve below 10,000ft. The liberated aluminum is not precipitated locally, but can be transported for distances of at least 5 miles (7km) to form clay. Poroperm in the deeper sandstones is improved selectively along routes of overpressured fluid expulsion; these can become quartzites. Secondary porosity must also compact during burial to trick petrographers into textural mis-identification.

  2. The secondary porosity trick: Arkose to quartzite in the North Sea

    SciTech Connect

    Haszeldine, S.; Wilkinson, M.; Darby, D. )

    1996-01-01

    Observations of mineralogy, texture, poroperm, stratigraphy and overpressure compiled from major reservoirs of the North Sea at different burial, structural and pressure settings, indicate to us that secondary porosity has continued to form at depths of 10-18,000ft (3-6km). This has resulted in strata-bound economic improvements to reservoir quality by as much as 8% and 2,000mD. The Brent Sandstone Group shows a decrease of feldspar with depth from 20% to 5%; clay content does not increase; identifiable secondary porosity does not increase. The HPHT Fulmar Sandstone shows a decrease of feldspar from 40% to 10%; aluminum (clay) content decreases; identifiable secondary porosity does not increase. Differences within these two sandstone Groups can not be explained by depositional variations. The Brea Formation shows loss of feldspar and calcite from 10% to 5%; only minimal clay is present; secondary porosity is often present, and is strata-bound. In this last case, an adjacent oilfield contains oil leaked up-dip from the deeper sandstones. This West Brae oilfield contains up to 13% kaolin clay, a big excess over the usual 2% expected for its present depth. The deep sand has lost clay, the shallow sand has imported clay. We conclude that feldspars continue to dissolve below 10,000ft. The liberated aluminum is not precipitated locally, but can be transported for distances of at least 5 miles (7km) to form clay. Poroperm in the deeper sandstones is improved selectively along routes of overpressured fluid expulsion; these can become quartzites. Secondary porosity must also compact during burial to trick petrographers into textural mis-identification.

  3. Dolomite diagenesis and porosity preservation in lithic reservoirs: Carmopolis member, Sergipe-Alagoas Basin, northeastern Brazil

    SciTech Connect

    Souza, R.S. de; De Ros, L.F.; Morad, S.

    1995-05-01

    The lithic sandstones and conglomerates of the Carmopolis Member of the Muribeca Formation (Aptian) were deposited by fan deltas, alluvial fans, and braid deltas that prograded from low-grade metamorphic terrains into the Sergipe-Alagoas rift basin during the opening of the South Atlantic. Initial carbonates in the Carmopolis reservoirs (presently at depths of 180-2200 m) were marine (high-Mg calcite/aragonite) grain rims, allochems, stromatolitic laminites, and meteoric calcite. These carbonates were subsequently replaced by dolomite/ankerite ({delta}18O{sub PDB} = -7.3 to -4.1{per_thousand}; {delta}{sup 13}C{sub PDB} = -15 to +16.2{delta}) derived from ascending thermobaric fluids prior to oil emplacement. These fluids also caused the direct precipitation of dolomite/ankerite cements and the replacement of dolomite/ankerite cements and the replacement of nonferroan dolomite by ferroan dolomite/ankerite. Rocks lacking early cements were strongly compacted, losing their primary intergranular porosity and permeability, whereas massively cemented rocks show only minor compaction and further diagenetic modifications. Partial cementation has greatly limited the compaction and preserved intergranular porosity, allowing the partial dissolution of carbonates and framework grains and the precipitation of replacive ferroan dolomite/ankerite and pyrite. Offshore reservoirs show late porosity reduction by the precipitation of quartz, kaolinite/dickite, saddle dolomite, and ferroan calcite. Experimental analyses of porosity and permeability reduction under pressure confirmed the importance of early cementation in the preservation of porosity in lithic rocks with ductile framework.

  4. The Stability of Two Connected Pendant Drops

    NASA Technical Reports Server (NTRS)

    Slobozhanin, Lev A.; Alexander, J. Iwan

    2004-01-01

    The stability of an equilibrium system of two drops suspended from circular holes is examined. The drop surfaces are disconnected surfaces of a connected liquid body. For holes of equal radii and identical pendant drops axisymmetric perturbations are always the most dangerous. The stability region for two identical drops differs considerably from that for a single drop. Loss of stability leads to a transition from a critical system of identical drops to a stable system of axisymmetric non-identical. This system of non-identical drops reaches its own stability limit (to isochoric or non-isochoric paturbations). For non-identical drops, loss of stability results in dripping or streaming from the holes. Critical volumes for non-identical drops have been calculated as functions of the Bond number, B. For unequal hole radii, stability regions have been constructed for a set of hole radius, K. The dependence of critical volumes on K and B is analyzed.

  5. Drop impact on a fiber

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Gil; Kim, Wonjung

    2016-04-01

    We present the results of a combined experimental and theoretical investigation of drop impact on a thin fiber. Using high-speed videography, we analyze the dynamics of droplet collision with a fiber. Based on the systematic experiments, we identify three outcomes of collision: capturing, single drop falling, and splitting. The outcomes are presented in a regime map, where the regime boundaries are explained through a scale analysis of forces. We also measure the liquid retention on the fiber after the droplet impact. By considering a liquid film on the fiber, we develop a mechanical model that predicts the residual water mass. Our model reveals that the residual mass depends critically on the fiber thickness and less on the impact speed. Our study can be extended to predicting the remaining droplet, critical problems in air filtration, water collection, and fiber coating.

  6. Behavior of precipitating water drops under the influence of electrical and aerodynamical forces

    NASA Astrophysics Data System (ADS)

    Coquillat, Sylvain; Chauzy, Serge

    1993-06-01

    The present work performs a realistic modeling of precipitating charged water drops under the influence of electrical and dynamical forces in the vertical and downward electric field of a thundercloud. The following factors which control the shape of an individual raindrop are taken into account: surface tension, internal hydrostatic pressure, aerodynamic pressure, and electrostatic pressure. Unlike a recent and notable work by Chuang and Beard (1990) in which this problem is approached by adjusting an empirical pressure distribution for the distortion, our model considers simple local pressure balance to determine the drop shape. This computation aims at characterizing drop distortion, falling speed modification, and disruption. The overall present results are similar to those of Chuang and Beard's more sophisticated model, and the predicted critical fields are even closer to wind tunnel measurements by Richards and Dawson (1971). The disruption of positively charged drops requires lower ambient fields than that of the negatively charged drops, and for highly charged and large drops they are of the order of those commonly measured within thunderclouds. At last, the terminal velocity is highly affected by net charge and ambient field. These processes are probably important in lightning initiation during drop disruption.

  7. Thermocapillary motion of deformable drops

    NASA Technical Reports Server (NTRS)

    Haj-Hariri, Hossein; Shi, Qingping; Borhan, Ali

    1994-01-01

    The thermocapillary motion of initially spherical drops/bubbles driven by a constant temperature gradient in an unbounded liquid medium is simulated numerically. Effects of convection of momentum and energy, as well as shape deformations, are addressed. The method used is based on interface tracking on a base cartesian grid, and uses a smeared color or indicator function for the determination of the surface topology. Quad-tree adaptive refinement of the cartesian grid is implemented to enhance the fidelity of the surface tracking. It is shown that convection of energy results in a slowing of the drop, as the isotherms get wrapped around the front of the drop. Shape deformation resulting from inertial effects affect the migration velocity. The physical results obtained are in agreement with the existing literature. Furthermore, remarks are made on the sensitivity of the calculated solutions to the smearing of the fluid properties. Analysis and simulations show that the migration velocity depends very strongly on the smearing of the interfacial force whereas it is rather insensitive to the smearing of other properties, hence the adaptive grid.

  8. Piezoelectric Water Drop Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Al Ahmad, Mahmoud

    2014-02-01

    Piezoelectric materials convert mechanical deformation directly into electrical charges, which can be harvested and used to drive micropower electronic devices. The low power consumption of such systems on the scale of microwatts leads to the possibility of using harvested vibrational energy due to its almost universal nature. Vibrational energy harvested using piezoelectric cantilevers provides sufficient output for small-scale power applications. This work reports on vibrational energy harvesting from free-falling droplets at the tip of lead zirconate titanate piezoelectric-based cantilevers. The harvester incorporates a multimorph clamped-free cantilever made of lead zirconate titanate piezoelectric thick films. During the impact, the droplet's kinetic energy is transferred to the form of mechanical stress, forcing the piezoelectric structure to vibrate and thereby producing charges. Experimental results show an instantaneous drop-power of 2.15 mW cm-3 g-1. The scenario of a medium intensity of falling water drops, i.e., 200 drops per second, yielded a power of 0.48 W cm-3 g-1 per second.

  9. Deep to shallow kaolinite relocation generates porosity

    SciTech Connect

    Mc Laughlin, O.M.; Mc Aulay, G.E.; Haszeldine, R.S. )

    1996-01-01

    Eocene and Paleocene sands make up the reservoir in the West Brae Field, which is located on the Fladen Ground Spur, Quadrant 16/7a, UK North Sea. The Tertiary sandstones were derived from a mixed source area of sediments and volcanics. Early carbonate cementation and late dissolution of carbonate cement and feldspars has resulted in sandstones possessing excellent poroperm characteristics, similar to the high quality upper reservoir sandstones described in the South, Central and North Brae fields. The diagenetic feature which most adversely affects these sandstones is the presence of large amounts of authigenic, kaolinite. Quantities of up to 13% kaolinite have been reported for the West Brae reservoir, an unusually high volume considering its current depth of 7,700ft. In contrast, the South, Central and North Brae fields exhibit only 1-3% diagenetic kaolinite, even though up to 8% feldspar dissolution porosity has been recorded. This study tests the hypothesis that feldspar dissolution at 12,000 ft in the Upper Jurassic reservoirs of South, Central and North Brae, has enabled aluminum to be exported from the deep Jurassic sandstones, to form kaolinite in the shallow Tertiary sandstones of West Brae. As Jurassic derived fluids have a distinct radiogenic: strontium signature, in contrast with Paleocene fluids which have an unradiogenic Sr signature, Sr isotope studies provide a test for this hypothesis. [sup 87]Sr/[sup 86]Sr analyses of the clays have been carried out to ascertain if their signature has been derived from dissolution of Jurassic minerals at depth, or if the signature is locally derived from Palaeocene sediments.

  10. Deep to shallow kaolinite relocation generates porosity

    SciTech Connect

    Mc Laughlin, O.M.; Mc Aulay, G.E.; Haszeldine, R.S.

    1996-12-31

    Eocene and Paleocene sands make up the reservoir in the West Brae Field, which is located on the Fladen Ground Spur, Quadrant 16/7a, UK North Sea. The Tertiary sandstones were derived from a mixed source area of sediments and volcanics. Early carbonate cementation and late dissolution of carbonate cement and feldspars has resulted in sandstones possessing excellent poroperm characteristics, similar to the high quality upper reservoir sandstones described in the South, Central and North Brae fields. The diagenetic feature which most adversely affects these sandstones is the presence of large amounts of authigenic, kaolinite. Quantities of up to 13% kaolinite have been reported for the West Brae reservoir, an unusually high volume considering its current depth of 7,700ft. In contrast, the South, Central and North Brae fields exhibit only 1-3% diagenetic kaolinite, even though up to 8% feldspar dissolution porosity has been recorded. This study tests the hypothesis that feldspar dissolution at 12,000 ft in the Upper Jurassic reservoirs of South, Central and North Brae, has enabled aluminum to be exported from the deep Jurassic sandstones, to form kaolinite in the shallow Tertiary sandstones of West Brae. As Jurassic derived fluids have a distinct radiogenic: strontium signature, in contrast with Paleocene fluids which have an unradiogenic Sr signature, Sr isotope studies provide a test for this hypothesis. {sup 87}Sr/{sup 86}Sr analyses of the clays have been carried out to ascertain if their signature has been derived from dissolution of Jurassic minerals at depth, or if the signature is locally derived from Palaeocene sediments.

  11. Diagenesis and porosity evolution of tight sand reservoirs in Carboniferous Benxi Formation, Southeast Ordos Basin

    NASA Astrophysics Data System (ADS)

    Hu, Peng; Yu, Xinghe; Shan, Xin; Su, Dongxu; Wang, Jiao; Li, Yalong; Shi, Xin; Xu, Liqiang

    2016-04-01

    The Ordos Basin, situated in west-central China, is one of the oldest and most important fossil-fuel energy base, which contains large reserves of coal, oil and natural gas. The Upper Palaeozoic strata are widely distributed with rich gas-bearing and large natural gas resources, whose potential is tremendous. Recent years have witnessed a great tight gas exploration improvement of the Upper Paleozoic in Southeastern Ordos basin. The Carboniferous Benxi Formation, mainly buried more than 2,500m, is the key target strata for hydrocarbon exploration, which was deposited in a barrier island and tidal flat environment. The sandy bars and flats are the favorable sedimentary microfacies. With an integrated approach of thin-section petrophysics, constant velocity mercury injection test, scanning electron microscopy and X-ray diffractometry, diagenesis and porosity evolution of tight sand reservoirs of Benxi Formation were analyzed in detail. The result shows that the main lithology of sandstone in this area is dominated by moderately to well sorted quartz sandstone. The average porosity and permeability is 4.72% and 1.22mD. The reservoirs of Benxi Formation holds a variety of pore types and the pore throats, with obvious heterogeneity and poor connection. Based on the capillary pressure curve morphological characteristics and parameters, combined with thin section and phycical property data, the reservoir pore structure of Benxi Formation can be divided into 4 types, including mid pore mid throat type(I), mid pore fine throat type(II), small pore fine throat type(III) and micro pro micro throat type(Ⅳ). The reservoirs primarily fall in B-subsate of middle diagenesis and late diagenesis, which mainly undergo compaction, cmentation, dissolution and fracturing process. Employing the empirical formula of different sorting for unconsolideated sandstone porosity, the initial sandstone porosity is 38.32% on average. Quantitative evaluation of the increase and decrease of

  12. Data Qualification Report: Calculated Porosity and Porosity-Derived Values for Lithostratigraphic Units for use on the Yucca Mountain Project

    SciTech Connect

    P. Sanchez

    2001-05-30

    The qualification is being completed in accordance with the Data Qualification Plan DQP-NBS-GS-000006, Rev. 00 (CRWMS M&O 2001). The purpose of this data qualification activity is to evaluate for qualification the unqualified developed input and porosity output included in Data Tracking Number (DTN) M09910POROCALC.000. The main output of the analyses documented in DTN M09910POROCALC.000 is the calculated total porosity and effective porosity for 40 Yucca Mountain Project boreholes. The porosity data are used as input to Analysis Model Report (AMR) 10040, ''Rock Properties Model'' (MDL-NBS-GS-000004, Rev. 00), Interim Change Notice [ICN] 02 (CRWMS M&O 2000b). The output from the rock properties model is used as input to numerical physical-process modeling within the context of a relationship developed in the AMR between hydraulic conductivity, bound water and zeolitic zones for use in the unsaturated zone model. In accordance with procedure AP-3.15Q, the porosity output is not used in the direct calculation of Principal Factors for post-closure safety or disruptive events. The original source for DTN M09910POROCALC.000 is a Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M&O) report, ''Combined Porosity from Geophysical Logs'' (CRWMS M&O 1999a and hereafter referred to as Rael 1999). That report recalculated porosity results for both the historical boreholes covered in Nelson (1996), and the modern boreholes reported in CRWMS M&O (1996a,b). The porosity computations in Rael (1999) are based on density-porosity mathematical relationships requiring various input parameters, including bulk density, matrix density and air and/or fluid density and volumetric water content. The main output is computed total porosity and effective porosity reported on a foot-by-foot basis for each borehole, although volumetric water content is derived from neutron data as an interim output. This qualification report uses technical assessment and

  13. Universal Behavior of the Initial Stage of Drop Impact

    NASA Astrophysics Data System (ADS)

    Klaseboer, Evert; Manica, Rogerio; Chan, Derek Y. C.

    2014-11-01

    During the early stages of the impact of a drop on a solid surface, pressure builds up in the intervening thin lubricating air layer and deforms the drop. The extent of the characteristic deformation is determined by the competition between capillary, gravitational, and inertial forces that has been encapsulated in a simple analytic scaling law. For millimetric drops, variations of the observed deformation with impact velocity V exhibit a maximum defined by the Weber and Eötvös numbers: We =1 +Eo . The deformation scales as V1 /2 at the low-velocity capillary regime and as V-1 /2 at the high-velocity inertia regime, in excellent agreement with a variety of experimental systems.

  14. Porosity and grain size controls on compaction band formation in Jurassic Navajo Sandstone

    USGS Publications Warehouse

    Schultz, Richard A.; Okubo, Chris H.; Fossen, Haakon

    2010-01-01

    Determining the rock properties that permit or impede the growth of compaction bands in sedimentary sequences is a critical problem of importance to studies of strain localization and characterization of subsurface geologic reservoirs. We determine the porosity and average grain size of a sequence of stratigraphic layers of Navajo Sandstone that are then used in a critical state model to infer plastic yield envelopes for the layers. Pure compaction bands are formed in layers having the largest average grain sizes (0.42–0.45 mm) and porosities (28%), and correspondingly the smallest values of critical pressure (-22 MPa) in the sequence. The results suggest that compaction bands formed in these layers after burial to -1.5 km depth in association with thrust faulting beneath the nearby East Kaibab monocline, and that hardening of the yield caps accompanied compactional deformation of the layers.

  15. Dynamics of a liquid drop in porous medium saturated by another liquid under gravity

    NASA Astrophysics Data System (ADS)

    Ivantsov, A. O.; Lyubimova, T. P.

    2016-02-01

    The work deals with numerical simulations of settling or ascension process of a liquid drop in porous media saturated by another liquid. The calculations were carried out using the Darcy model by Level set method with adaptive mesh refinement algorithm that dynamically refines computational mesh near interface. It is shown that the drop is unstable and the finger instability develops at the forefront of moving drop for any ratio of the viscosities of liquids. Under modulated pressure gradient small-scale perturbations of interface are suppressed and in the case of modulation with large enough intensity drop becomes stable.

  16. Linear tension of two-dimensional drops on planar adsorbent faces

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.; Zaytseva, E. S.; Rabinovich, A. B.

    2016-06-01

    The size dependence of the linear tension of round two-dimensional equilibrium drops in the vapor phase on a homogeneous surface of an adsorbent is studied at the pressure of saturated two-dimensional vapor. The calculations are based on the lattice gas model in a quasi-chemical approximation with allowance for the correlation effects of the nearest interacting molecules. Methods for calculating linear tension using the equimolecular reference line are considered. Temperature dependences of the linear tension are studied for metastable and equilibrium drops. It is found that the differences between the thermodynamic properties of two types of drops are slight over a wide range of variation in drop radii.

  17. Design and implementation of an efficient acoustically levitated drop reactor for in stillo measurements.

    PubMed

    Field, Christopher R; Scheeline, Alexander

    2007-12-01

    We present the details necessary for building an efficient acoustic drop levitator with reduced electrical power consumption and greater drop stability compared to previous designs. The system is optimized so that the levitated drop may be used as a chemical reactor. By introducing a temperature, pressure, and relative humidity sensor for feedback control of a linear actuator for adjusting resonator length, we have built a completely automated system capable of continuous levitation for extended periods of time. The result is a system capable of portable operation and interfacing with a variety of detection instrumentation for in stillo (in drop) measurements. PMID:18163744

  18. Porosity in collapsible Ball Grid Array solder joints

    SciTech Connect

    Gonzalez, C.A. |

    1998-05-01

    Ball Grid Array (BGA) technology has taken off in recent years due to the increased need for high interconnect density. Opposite to all the advantages BGA packages offer, porosity in collapsible BGA solder joints is often a major concern in the reliability of such packages. The effect of pores on the strength of collapsible BGA solder-joints was studied by manufacturing samples with different degrees of porosity and testing them under a shear load. It was found that the shear strength of the solder joints decreased in a linear fashion with increasing porosity. Failure occurred by internal necking of the interpore matrix. It was confirmed that entrapment of flux residues leads to porosity by manufacturing fluxless samples in a specially made furnace, and comparing them with samples assembled using flux. Also, contamination of Au electrodeposits (in substrate metallization) was determined to cause significant porosity. It was found that hard-Au (Co hardened Au) electrodeposits produce high degrees of porosity even in the absence of flux. Finally, increasing the time the solder spends in the molten state was proven to successfully decrease porosity.

  19. Friction Factor Characterization for High-Porosity Random Fiber Regenerators

    NASA Technical Reports Server (NTRS)

    Thieme, Lanny G.

    2001-01-01

    NASA Glenn Research Center, the Department of Energy (DOE), and Stirling Technology Company (STC) of Kennewick, Washington are developing a Stirling convertor for a high-efficiency Stirling Radioisotope Power System to provide electric power for NASA Space Science Missions. STC is developing the 55-We Technology Demonstration Convertor (TDC) under contract to DOE. Steady-flow tests were completed to determine the friction factor for the high-porosity regenerators that are used in the TDC. STC fabricated a flow test fixture and three random fiber regenerator test samples, one each at approximately 80, 88, and 96 percent porosities. The flow tests were then completed by the NASA Glenn Flow Calibration Laboratory, and the data reduced to Reynolds number and friction factor. The results showed that the 80 and 88 percent porosity samples had similar characteristics while the 96 percent porosity sample had significantly higher friction factors for given Reynolds numbers compared to the samples with lower porosities. Comparisons were also made between the test data and existing correlations. STC used this data to derive a modified regenerator friction factor correlation for use in the Stirling design code GLIMPS for porosities greater than 88 percent. Using this new correlation, the final optimized regenerator design porosity was reduced from 96 to 90 percent.

  20. Soil surface roughness and porosity under different tillage systems

    NASA Astrophysics Data System (ADS)

    Rodriguez-Gonzalez, J.; Saa-Requejo, A.; Gómez, J. A.; Valencia, J. L.; Zarco, P.; Tarquis, A. M.

    2012-04-01

    Both soil porosity and surface elevation can be altered by tillage operation. Even though the surface porosity is an important parameter of a tilled field, however, no practical technique for rapid and non-contact measurement of surface porosity has been developed yet. On the contrary, the surface elevation of tilled soil can be quickly determined with a laser profiler. Working under the assumption that the surface elevation of a tilled field is a complicated superposition of the soil terrain profile at a larger-scale and the roughness at a fine-scale, this study included three aspects: (i) to establish an index (Roughness Index, RI) at a fine-scale to associate the surface roughness with porosity; (ii) to examine the correlation between surface porosity and the proposed RI by three types of tillage treatment in the field; and (iii) to check the scaling/multiscaling behavior among different grid sizes of calculating RI on predicting surface porosity. Consequently, the statistical results from each tilled plot show a strong correlation between the surface porosity and the defined RI in an early stage (ca. 2 days) after tillage. Acknowledgements Funding provided by CEIGRAM (Research Centre for the Management of Agricultural and Environmental Risks)and Spanish Ministerio de Ciencia e Innovación (MICINN) through project AGL2010-21501/AGR is greatly appreciated.