Hydrostatic Pressure Variation Research Articles

Mitsui model with diagonal strains: A unified description of external pressure effect and thermal expansion of Rochelle salt NaKC_4H_4O_6·4H_2O

We elaborate a modification of the deformable two-sublattice Mitsui model of [Levitskii R.R. et al., Phys. Rev. B. 2003, 67, 174112] and [Levitskii R.R. et al., Condens. Matter Phys., 2005, 8, 881] that consistently takes into account diagonal components of the strain tensor, arising either due to external pressures or due to thermal expansion. We calculate the related to those strains thermal, piezoelectric, and elastic characteristics of the system. Using the developed fitting procedure, a set of the model parameters is found for the case of Rochelle salt crystals, providing a satisfactory agreement with the available experimental data for the hydrostatic and uniaxial pressure dependences of the Curie temperatures, temperature dependences of spontaneous diagonal strains, linear thermal expansion coefficients, elastic constants c_ij^E and c_i4^E, piezoelectric coefficients d_1i and g_1i (i=1,2,3). The hydrostatic pressure variation of dielectric permittivity is described using a derived expression for the permittivity of a partially clamped crystal. The dipole moments and the asymmetry parameter of Rochelle salt are found to increase with hydrostatic pressure.

Impact of seasonal temperature and pressure changes on methane gas production, dissolution, and transport in unfractured sediments

A one‐dimensional reaction‐transport model is used to investigate the dynamics of methane gas in coastal sediments in response to intra‐annual variations in temperature and pressure. The model is applied to data from two shallow water sites in Eckernforde Bay (Germany) characterized by low and high rates of upward fluid advection. At both sites, organic matter is buried below the sulfate‐reducing zone to the methanogenic zone at sufficiently high rates to allow supersaturation of the pore water with dissolved methane and to form a free methane gas phase. The methane solubility concentration varies by similar magnitudes at both study sites in response to bottom water temperature changes and leads to pronounced peaks in the gas volume fraction in autumn when the methanic zone temperature is at a maximum. Yearly hydrostatic pressure variations have comparatively negligible effects on methane solubility. Field data suggest that no free gas escapes to the water column at any time of the year. Although the existence of gas migration cannot be substantiated by direct observation, a speculative mechanism for slow moving gas is proposed here. The model results reveal that free gas migrating upward into the undersaturated pore water will completely dissolve and subsequently be consumed above the free gas depth (FGD) by anaerobic oxidation of methane (AOM). This microbially mediated process maintains methane undersaturation above the FGD. Although the complexities introduced by seasonal changes in temperature lead to different seasonal trends for the depth‐integrated AOM rates and the FGD, both sites adhere to previously developed prognostic indicators for methane fluxes based on the FGD.

Subharmonic Contrast Microbubble Signals for Noninvasive Pressure Estimation under Static and Dynamic Flow Conditions

Our group has proposed the concept of subharmonic aided pressure estimation (SHAPE) utilizing microbubble-based ultrasound contrast agent signals for the noninvasive estimation of hydrostatic blood pressures. An experimental system for in vitro SHAPE was constructed based on two single-element transducers assembled confocally at a 60 degree angle to each other. Changes in the first, second and subharmonic amplitudes of five different ultrasound contrast agents were measured in vitro at static hydrostatic pressures from 0-186 mmHg, acoustic pressures from 0.35-0.60 MPa peak-to-peak and frequencies of 2.5-6.6 MHz. The most sensitive agent and optimal parameters for SHAPE were determined using linear regression analysis and implemented on a Logiq 9 scanner (GE Healthcare, Milwaukee, WI). This implementation of SHAPE was then tested under dynamic-flow conditions and compared to pressure-catheter measurements. Over the pressure range studied, the first and second harmonic amplitudes reduced approximately 2 dB for all contrast agents. Over the same pressure range, the subharmonic amplitudes decreased by 9-14 dB and excellent linear regressions were achieved with the hydrostatic pressure variations (r = 0.98, p < 0.001). Optimal sensitivity was achieved at a transmit frequency of 2.5 MHz and acoustic pressure of 0.35 MPa using Sonazoid (GE Healthcare, Oslo, Norway). A Logiq 9 scanner was modified to implement SHAPE on a convex transducer with a frequency range from 1.5-4.5 MHz and acoustic pressures from 0-3.34 MPa. Results matched the pressure catheter (r2 = 0.87). In conclusion, subharmonic contrast signals are a good indicator of hydrostatic pressure. Out of the five ultrasound contrast agents tested, Sonazoid was the most sensitive for subharmonic pressure estimation. Real-time SHAPE has been implemented on a commercial scanner and offers the possibility of allowing pressures in the heart and elsewhere to be obtained noninvasively.

Tidal variability of salinity and velocity fields related to intense point‐source submarine groundwater discharges into the coastal ocean

Velocity and hydrography measurements were used to determine the tidal variability and detailed structure of an intense (~ 43,200 m3 d−1) point‐source submarine groundwater discharge from a spring located in the coastal ocean of the Yucatán peninsula, Mexico. Measurements were obtained during a dry season with a combination of towed, profiling, and fixed instrumentation. The goal of these observations was to understand the effects of tides on the velocity and salinity structure of the water column that determine mixing and dispersion processes at spatial scales from meters to kilometers. Tidally averaged flows were characterized by an upward jet flanked by asymmetric downdrafts. The asymmetry was caused by a ~ 0.1 m s−1 ambient horizontal flow and by the ~ 40° angle (relative to the vertical) of discharge. The spatially averaged salinity distributions exhibited lowest values at low tides and highest values at high tides. This was attributed to tidal variations of hydrostatic pressure acting on the spring outflow, which allowed ∼1 m s−1 vertical flows at low tides and &lt; 0.05 m s−1 vertical velocities at high tides. The vertical momentum balance consisted of upward accelerations produced by buoyancy and inertia from the spring and downward accelerations from gravity. On the basis of this balance and of energetic considerations, the vertical extent of the spring discharge likely depends on the density contrast between ambient and discharge waters (buoyancy forces), the upward speed of the spring (inertia forces), and the depth of the water column (hydrostatic pressure force), all of which vary with tides.

Effect of Hydrostatic Pressure on the Microstructure and Mechanical Properties during and after High Pressure Torsion

The presence of a hydrostatic pressure as a general feature of SPD methods is essential for achieving the high strains and the introduction of the high amount of lattice defects, which are necessary to establish new grain boundaries. Systematic investigations of High Pressure Torsion (HPT)-deformed Cu under variation of strain and hydrostatic pressure revealed marked differences between the in-situ torsional stress (torque measurement) and the post-HPT strength of the ultrafine-grained materials. These facts let assume the occurrence of relaxation processes (recovery/recrystallisation) of static character with respect to the release of the hydrostatic pressure after straining. In order to gain insight into the processes behind, a special experimental procedure was designed to simulate the hydrostatic pressure release. Investigations by X-ray line profile analysis and hardness measurement show marked influences of the pressure release on microstructure and strength. While the size of the coherently scattering domains is not strongly affected, the dislocation density decreases drastically and the arrangement of the dislocations within the subgrain structure changes to a less stress intensive one, upon the pressure release. In parallel the hardness decreases significantly and confirms the discrepancy between in-situ torque-stress and post-HPT strength.

A simple approach to water and plankton sampling for water microbiological and physicochemical characterizations at various depths in aquatic ecosystems

Water microbiological and physicochemical characterizations at various depths of aquatic ecosystems are basic requirements in several fields of research. A chief difficulty in hydrobiology, limnology, biological oceanography and water environmental microbiology is that of taking accurate field collections that are representative of the natural environment and population at various depths of aquatic ecosystems. Gathering water/plankton samples in a level just below the surface of the water body upon rising in columns from various depths due to hydrostatic pressure variations provided a simple approach for water and plankton sampling. Based on this approach, several forms of simple devices for water and plankton sampling were developed for water microbiological and physicochemical characterizations at various depths of aquatic ecosystems. The described approach showed less sampling errors in comparison to Van Dorn bottle and was comparable to water pumping but requires no external source of power. The described samplers are inexpensive and can be self constructed.

Interaction of Thioether Groups at the Open Coordination Sites of Palladium(II) and Platinum(II) Complexes Probed by Luminescence Spectroscopy at Variable Pressure

The crystal structures of [PtCl(2)(ttcn)], [PdCl(2)(ttcn)], [Pt(ethylenediamine)(ttcn)](PF(6))(2), and [Pd(ethylenediamine)(ttcn)](PF(6))(2) (ttcn = 1,4,7-trithiacyclononane) show short apical metal---S(ttcn) distances, qualitatively indicating an interaction. Luminescence spectroscopy was used to study these crystalline complexes at room temperature and variable hydrostatic pressure. The luminescence band maximum of [PdCl(2)(ttcn)] shows a pressure-induced blue shift of +6 cm(-1)/kbar, while the platinum(II) compounds show a red shift of approximately -20 cm(-1)/kbar. This difference is rationalized in terms of a competition between blue shifts due to pressure-induced metal-ligand bond shortening in the equatorial plane and increasing out-of-plane distance of the metal center, and a red shift due to the approach of the apical sulfur donor to the metal center. Density functional theory (DFT) calculations indicate d-d luminescence transitions and a different nature of the highest occupied molecular orbital (HOMO) for [PdCl(2)(ttcn)] than for [PtCl(2)(ttcn)], while the lowest unoccupied molecular orbitals (LUMOs) are identical in character. This electronic structure difference is used to rationalize the different pressure effects.

Investigation of detention pond outflow characteristics

Detention ponds are important units of drainage system for managing excess rainfall and runoff quality. To design detention ponds the outflow characteristic must be accurately known. Perforated riser pipes are a popular outlet control structure for stormwater detention basins. This study examines the discharge characteristics of a circular orifice cut into a vertical riser pipe as an outflow mechanism for the detention pond. In particular, the effects of the head above the orifice, the size of the orifice and the size of the riser pipe on the discharge coefficient are evaluated. A physical model is built and various size riser pipes are installed in the tank to simulate a detention basin. The discharge through the orifice is determined by measuring the rate of change of the water level in the tank against time. A water level against volume drained calibration is used to find the rate of change of volume over time, and hence the discharge coefficient. The study shows that the discharge coefficient increases as the head and the ratio of the orifice diameter to pipe diameter decreases. It is found that the hydrostatic pressure variation across the orifice at the small head has a minimum impact on the discharge. A generalised function is developed to estimate discharge under a varying head over the orifice and for different ratios of orifice diameter to riser pipe diameter, which can be used for the design of detention ponds.

Overview of natural cross-ventilation studies and the latest simulation design tools used in building ventilation-related research

High-performance insulation, draught stripping and double glazing have effectively sealed off the fresh air routes and have made adequate natural ventilation impossible inside the modern energy-efficient home nowadays. Cross ventilation, a passive cooling method for buildings, is a major type of natural ventilation. Various study approaches have been reported; however, there is still no appropriate simulation tool that can predict the indoor thermal environment of natural ventilation. The typical building energy simulation for investigating a naturally ventilated building adopts thermal simulation and an airflow network. However, the airflow network approach for airflow estimation in building energy simulation cannot accurately predict indoor airflow by solving the pressure-flow algebraic equation, the mass balance equation and hydrostatic pressure variations. Recent advances in computer performance and computational fluid dynamics (CFD) software integrated with building energy simulation have made it possible to improve the accuracy to assess the performance of natural ventilation and also to give more realistic predictions of airflow in buildings. This chapter overviews and discusses various network airflow models integrated with CFD in the natural ventilation of buildings. Examples of results obtained with this approach are given to demonstrate the significant effects of such a coupling programme on natural ventilation prediction accuracy.

Vibrational properties of grain boundaries in nanocrystalline Ni using second moment potentials

The high frequency phonon properties of a computer-generated nanocrystalline (nc) Ni are investigated by directly calculating the onsite phonon Green function using a recursion technique based on a continued fraction representation. Past work found that a high frequency enhancement of the vibrational density of states exists and arises from localised vibrational modes forming within the nc grain boundary regions at atoms of reduced coordination [Phys. Rev. Lett. 92 (2004) p.035505]. In the present work, the positron wave function for such nanocrystalline grain boundaries was calculated and used to identify regions of localised free volume that, in turn, were found to correlate well with the localised vibrational modes. The work also demonstrates that, irrespective of the form of the central-force inter-atomic potential used, the observed effect can be more generally understood with respect to local variations in hydrostatic pressure within the grain boundary.

Periodic Behavior of the Bubble Jet (Geyser) in the Taketomi Submarine Hot Springs of the Southern Part of Yaeyama Archipelago, Japan

AbstractThe periodicity of the bubble jet that spouts intermittently from the Taketomi submarine hot spring in Yaeyama archipelago, Japan, was measured for the first time using an acoustic current meter. The time series analysis of the upward velocity for the data, without a spiky signal, indicates that the cycle fluctuates between 38 and 85 s. Focusing on the period of high and low tide, the dominant time cycles were 66 and 41 s, respectively. These results show that the fluctuation of pressure with tide affected the eruption period of the bubble jet. In accordance with the vertical tube theory, estimations of thermal source and recharge water temperatures were carried out by taking into account the boiling point change due to the tidal variation in hydrostatic pressure. The result indicated that if the heat source temperature was higher than 200.0 °C and recharge water temperature was preheated to 117.96 °C, the observed eruption time cycles at high and low tide were stable.

Implementation of baroclinic terms in a three-dimensional hydrodynamic model and its application to Anzali Port, Iran

Baroclinic terms have been implemented in a three-dimensional fully hydrodynamic model developed by Badiei et al. [2008. A three-dimensional non-hydrostatic boundary fitted model for free surface flows. International Journal for Numerical Methods in Fluids, 56(6), 607–627] modifying its momentum equations to account for density gradients and utilizing the scalar (salinity, temperature, etc.) conservation equation (SCE) and a state equation for the calculation of density. In the solution of advection–diffusion terms of the governing Navier–Stokes equations (NSE) and SCE, a symmetric splitting method was applied to ensure the long-term stability of simulations. Correction terms proposed by Ruddic et al. (1995) were applied to SCE to ensure the conservation of the scalar quantity. In the presence of baroclinic terms, the zero gradient pressure in the vertical direction in the vicinity of surface and bottom boundaries assumed by Badiei et al. [2008. A three-dimensional non-hydrostatic boundary fitted model for free surface flows. International Journal for Numerical Methods in Fluids, 56(6), 607–627] created spurious currents. This problem was solved by assuming a hydrostatic pressure variation at those boundaries. The ability of extended model was validated by comparing its results with an experimental test case. The simulation of hydrodynamic and salt intrusion at Anzali Port located at the southern coasts of Caspian Sea in Iran was carried out by the model with both barotropic and baroclinic modes. The simulated results with baroclinic mode show a better agreement with measured data as compared to the results of barotropic mode that clearly demonstrate the significance of baroclinic terms in the simulation of cyclic intrusion of salt wedge into the Port Basin.

Solutions for cylindrical cavity in saturated thermoporoelastic medium

Based on the thermodynamics of irreversible processes, the mass conservation equation and heat energy balance equation are established. The governing equations of thermal consolidation for homogeneous isotropic materials are presented, accounting for the coupling effects of the temperature, stress and displacement fields. The case of a saturated medium with a long cylindrical cavity subjected to a variable thermal loading and a variable hydrostatic pressure (or a variable radial water flux) with time is considered. The analytical solutions are derived in the Laplace transform space. Then, the time domain solutions are obtained by a numerical inversion scheme. The results of a typical example indicate that thermodynamically coupled effects have considerable influences on thermal responses.

Abstract 5960: Implementation of Noninvasive Subharmonic Pressure Estimation on a Commercial Ultrasound Scanner

This project aims to monitor and quantify intra-cardiac pressures via contrast-enhanced subharmonic imaging. We have proposed subharmonic aided pressure estimation (SHAPE; U.S. Patent 6,302,845) utilizing microbubble-based contrast agent signals for the noninvasive estimation of hydrostatic blood pressures in the heart cavities and in this study implemented real-time SHAPE on a commercial US scanner. An experimental pulse-echo system for SHAPE was constructed based on two single element transducers assembled confocally at a 60° angle to each other. A transducer with a bandwidth of 38% and a center frequency of 2.2 MHz (Staveley, East Hartford, CT) was used as the transmitter and a second transducer with a bandwidth of 86% and a center frequency of 3.6 MHz (Etalon Inc., Lebanon, IN) was the receiver. Changes in first, second, and subharmonic amplitudes of 6 different US contrast agents were measured in vitro at hydrostatic pressures from 0 –186 mmHg, acoustic pressures from 0.35– 0.60 MPa and frequencies of 2.5– 6.6 MHz. The optimal parameters for SHAPE were determined using linear regression analysis and implemented on a Sonix RP scanner (Ultrasonix Medical Corp, Richmond, Canada). The real-time implementation of SHAPE was tested in vitro. Over the pressure range studied the 1st and 2nd harmonic amplitudes reduced ~2 dB for all US contrast agents. Over the same pressure range, the subharmonic amplitudes decreased by 10 –14 dB and excellent linear regressions were achieved with the hydrostatic pressure variations (r 2 &gt;0.98, p &lt; 0.001). The optimal sensitivity for SHAPE was achieved at a transmit frequency of 2.5 MHz (i.e., receiving at 1.25 MHz) at a 0.35 MPa acoustic pressure using Sonazoid (GE Healthcare, Oslo, Norway) which declined ~14.4 dB in vitro. A Sonix RP scanner was modified to implement SHAPE on a phased array transducer PA4 –2 with a frequency range from 1.5– 4.5 MHz. A pulse inversion technique was used and the subharmonic signals are displayed in real-time and can also be stored for off-line analysis. SHAPE offers the possibility of allowing pressure gradients in the heart to be obtained noninvasively. Future studies will include in vivo pressure measurements. Supported by AHA grant no 06554414 and NIH HL081892. This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania &amp; West Virginia).

NMR investigation of water and methanol mobility in nanocomposite fuel cell membranes

Water and methanol transport behavior, morphology, and solvent adsorption of filler-free Nafion membrane, Nafion–SiO2, Nafion–TiO2, and two Nafion–Zr(HPO4)2 composites were investigated using nuclear magnetic resonance methods, including spin-lattice relaxation and pulsed-field-gradient spin-echo diffusion conducted under both variable temperature and variable hydrostatic pressure conditions and scanning electron microscopy analysis. A comparison between water and methanol self-diffusion coefficients reveals that the water mobility is higher than the methanol mobility in all the membranes. Additionally, the inclusion of inorganic fillers improves both the solvent uptakes and the transport properties of the composite membranes relative to filler-free Nafion, with the exception of one of the Nafion–Zr(HPO4)2 composite. Nafion–Zr(HPO4)2 composites were prepared by two different procedures, in situ and ex situ. Although phosphorus-31 magic-angle spinning nuclear magnetic resonance spectra show the same structures of the particles in both kinds of membranes, the morphology, solvent absorption properties, and solvent mobilities are very different.

Angiopoietin-1 Requires p190 RhoGAP to Protect against Vascular Leakage in Vivo

Angiopoietin-1 (Ang-1), a ligand of the endothelium-specific receptor Tie-2, inhibits permeability in the mature vasculature, but the mechanism remains unknown. Here we show that Ang-1 signals Rho family GTPases to organize the cytoskeleton into a junction-fortifying arrangement that enhances the permeability barrier function of the endothelium. Ang-1 phosphorylates Tie-2 and its downstream effector phosphatidylinositol 3-kinase. This induces activation of one endogenous GTPase, Rac1, and inhibition of another, RhoA. Loss of either part of this dual effect abrogates the cytoskeletal and anti-permeability actions of Ang-1, suggesting that coordinated GTPase regulation is necessary for the vessel-sealing effects of Ang-1. p190 RhoGAP, a GTPase regulatory protein, provides this coordinating function as it is phosphorylated by Ang-1 treatment, requires Rac1 activation, and is necessary for RhoA inhibition. Ang-1 prevents the cytoskeletal and pro-permeability effects of endotoxin but requires p190 RhoGAP to do so. Treatment with p190 RhoGAP small interfering RNA completely abolishes the ability of Ang-1 to rescue endotoxemia-induced pulmonary vascular leak and inflammation in mice. We conclude that Ang-1 prevents vascular permeability by regulating the endothelial cytoskeleton through coordinated and opposite effects on the Rho GTPases Rac1 and RhoA. By linking Rac1 activation and RhoA inhibition, p190 RhoGAP is critical to the protective effects of Ang-1 against endotoxin. These results provide mechanistic evidence that targeting the endothelium through Tie-2 may offer specific therapeutic strategies in life-threatening endotoxemic conditions such as sepsis and acute respiratory distress syndrome.

Effect of physical variables on particle critical erosion shear stress: Hydrostatic pressure, slope and changes in water density

In recent years, the importance of organo-mineral aggregates (OMAs) in the transport of organic material from the continental shelf to the deep ocean floor has been recognized. Attempts to model the transport of these OMAs rely on measurements of several physical parameters, such as the critical erosion shear stress. However, due to technical constraints, such measurements are not done in situ, making it difficult to assess the impact of environmental parameters on the measurements made, and their accuracy in representing the study site. Changes in hydrostatic pressure, slope angle and water density potentially can affect the critical erosion shear stress of OMAs. Using new methodologies, we found no measurable effect of hydrostatic pressure variation on the OMAs' resuspension behavior. Changes in slope angle resulted in the decrease of u∗ cri up to 35%. The u∗ cri decreased by 9% with an exchange with denser water, and it increased by 6% with an exchange with lighter water. These changes were temporary, and after a 3-h stabilization the u∗ cri returned to the original value. We will discuss the future applications of these results on modeling of particle transport.

Effects of cyclic hydrostatic pressure on the brain biogenic amines concentrations in the flounder, Platichthys flesus

The present study evaluated the effects of cyclic variations of hydrostatic pressure (HP) on neurotransmitters in the whole brain of flounder. The concentrations of the biogenic amines L-3,4-dihydroxyphenylalanine (L-DOPA), dopamine (DA), norepinephrine (NE), epinephrine (E), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 3-methoxytyramine (3-MT), 5-hydroxytryptamine (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) were measured. Fish were subjected to HP cyclic variations which mimic naturally occurring conditions for a period of 14 days. DA, NE and 5-HT concentrations were significantly smaller by 21, 24 and 36%, respectively, compared to control fish. The concentrations of monoamine metabolites HVA, 3-MT and 5-HIAA were also smaller than those in control fish. These results suggest that central monoaminergic systems were influenced during long exposure to cyclic HP. The decreases of central neurotransmitters content might be involved in the physiological and behavioral responses to intermittent HP in fish.

Comparación de las variaciones de presión abdominal en medio acuático y aéreo durante la realización de cuatro ejercicios abdominales hipopresivos

Objective To analize the effects of submersion in abdominal pressure and determine the effectiveness of hipopressive gymnastic in acuatic enviroment. Material To carry out the analysis an indoor-pool was used. Meassurements of abdominal pressure variations have been taken using a manometer connected to a pressure sensor located in the anus. Method Comparison between abdominal pressure variations obtained in four different positions: stand up, crouching, knneling and quadrupedic position and in four different situations: aerial with and without typical corrective factors of hipopressive postures and submersed in the same situations. The analysis has been carried out within a group of eighteen young women. Results Variations in abdominal pressure have been compared using the Wilcoxon test. It has been found a statistically significant decrease in abdominal pressure in each aerial position, without hipopressive corrective factors applied in relation to the reference position. These deviations become remarked with corrective factors applied (specially in quadrupedic position). In acuatic enviroment, an increase of abdominal pressure has been detected in every functional situation, corresponding to hydrostatic pressure variation induced by water. Conclusions Acuatic Hipopressive Gymnastic offers no cuantitative significant advantage attending to abdominal pressure decrease (in absolute values). Nevertheless, hydrostatic pressure effect (with or without hipopressive exercise) at this specific depth results quite useful to reduce muscular tone and improve diaphragmatic domes mobility.

Determination of ozone mass transfer coefficient in a tall continuous flow counter-current bubble contactor

Abstract Preliminary experiments in a continuous flow counter-current bubble type ozone contactor, 3 m in length and 25 mm diameter, indicated that the gas phase hold-up ( ɛ G ) in the contactor increased linearly from 8 to 15% when gas flow rate ( Q g ) was increased from 500 to 1000 mL min −1 (8.33 × 10 −6 to 1.67 × 10 −5 m 3 s −1 ). The liquid phase dispersion coefficient ( D L ) in the contactor increased from (2.02 ± 0.83) × 10 −3 to (2.34 ± 0.46) × 10 −3 m 2 s −1 when Q g was increased from 500 to 1000 mL min −1 (8.33 × 10 −6 to 1.67 × 10 −5 m 3 s −1 ). The contactor was mathematically modeled considering the hydrostatic pressure variation along reactor height, and assuming the gas and liquid phases in the reactor to be plug flow and mixed flow, respectively. Using this model, aqueous ozone concentration was simulated at various reactor heights as a function of time. The simulation results using an ozone mass transfer coefficient ( K L a ) of 0.025 s −1 matched well with the corresponding experimental data. Experimental data on gaseous ozone concentration effluent from the reactor was also obtained as a function of time. This data also matched well with corresponding simulation results for a K L a value of 0.025 s −1 . Sensitivity analysis indicated that the model simulation results were relatively insensitive to changes in K L a value in the range of 0.015–0.035 s −1 . The work described in this paper is the first part of a continuing study to develop a fully mechanistic model of a tall ozone contactor for degradation of micro-pollutants in water.