Vertical Flow Component Research Articles

Investigating Water Movement Within and Near Wells Using Active Point Heating and Fiber Optic Distributed Temperature Sensing.

There are few methods to provide high-resolution in-situ characterization of flow in aquifers and reservoirs. We present a method that has the potential to quantify lateral and vertical (magnitude and direction) components of flow with spatial resolution of about one meter and temporal resolution of about one day. A fiber optic distributed temperature sensor is used with a novel heating system. Temperatures before heating may be used to evaluate background geothermal gradient and vertical profile of thermal diffusivity. The innovation presented is the use of variable energy application along the well, in this case concentrated heating at equally-spaced (2 m) localized areas (0.5 m). Relative to uniform warming this offers greater opportunity to estimate water movement, reduces required heating power, and increases practical length that can be heated. Numerical simulations are presented which illustrate expected behaviors. We estimate relative advection rates near the well using the times at which various locations diverge from a heating trajectory expected for pure conduction in the absence of advection. The concept is demonstrated in a grouted 600 m borehole with 300 heated patches, though evidence of vertical water movement was not seen.

Characterising the dynamics of surface water-groundwater interactions in intermittent and ephemeral streams using streambed thermal signatures

Ephemeral and intermittent flow in dryland stream channels infiltrates into sediments, replenishes groundwater resources and underpins riparian ecosystems. However, the spatiotemporal complexity of the transitory flow processes that occur beneath such stream channels are poorly observed and understood. We develop a new approach to characterise the dynamics of surface water-groundwater interactions in dryland streams using pairs of temperature records measured at different depths within the streambed. The approach exploits the fact that the downward propagation of the diel temperature fluctuation from the surface depends on the sediment thermal diffusivity. This is controlled by time-varying fractions of air and water contained in streambed sediments causing a contrast in thermal properties. We demonstrate the usefulness of this method with multi-level temperature and pressure records of a flow event acquired using 12 streambed arrays deployed along a ∼ 12 km dryland channel section. Thermal signatures clearly indicate the presence of water and characterise the vertical flow component as well as the occurrence of horizontal hyporheic flow. We jointly interpret thermal signatures as well as surface and groundwater levels to distinguish four different hydrological regimes: [A] dry channel, [B] surface run-off, [C] pool-riffle sequence, and [D] isolated pools. The occurrence and duration of the regimes depends on the rate at which the infiltrated water redistributes in the subsurface which, in turn, is controlled by the hydraulic properties of the variably saturated sediment. Our results have significant implications for understanding how transitory flows recharge alluvial sediments, influence water quality and underpin dryland ecosystems.

Tritium Tracers of Rapid Surface Water Ingression into Arsenic-bearing Aquifers in the Lower Mekong Basin, Cambodia

Arsenic (As) contamination of groundwaters in South and Southeast Asia is a major threat to public health in these areas. Understanding the source and age of the groundwaters is critically important to understanding the controls on As mobilization in these aquifers. Using tritium (3H) and noble gas (He and Ne) signatures, model groundwater ages and dominant hydrological controls were identified in a transect oriented broadly parallel to inferred groundwater flowpaths in Kandal Province, Cambodia in the lower Mekong Basin. Apparent 3H-3He ages showed that most groundwaters are modern (< 55 years), indicating relatively fast recharge even in the absence of large-scale groundwater abstraction. The age-depth relationship indicates a strong vertical component of groundwater flow and allows for recharge rates to be estimated. Vertical and horizontal flow velocities are heterogeneous and site-specific. The conceptual framework will be used to better understand As mobilization and subsequent transport with these and similar aquifers.

A Reappraisal of the Hydrogeology of the Western Margin of the Great Artesian Basin: Chemistry, Isotopes and Groundwater Flow

The combination of hydrochemistry with other environmental tracers such as noble gases and uranium series dating of travertine deposits are providing new insights into the hydrogeology of the western margin of the GAB. Previous conceptual models of simple geology and geochemical evolution along flow paths have been re-examined. Our results show that a far more complex model is evolving involving complex hydrogeology, faulting and sub-basins as well as a significant vertical flow component.

Karst groundwater source protection based on the time-dependent vulnerability assessment model: Crnica springs case study, Eastern Serbia

The implementation of sanitary protection zones is one of the most widely used approaches for preventive groundwater protection. Current regulations are usually based on the determination of the horizontal groundwater travel time component, while the vertical component is commonly neglected. Karst aquifers are especially sensitive to contamination through the unsaturated zone, and consequently numerous methods for determining intrinsic vulnerability have been developed. Many of these methods take into account the effects in the unsaturated zone, but mostly by indirect means. Vulnerability assessment methods do not fully reflect the component of groundwater residence time, making groundwater delineation zoning more difficult, with possible ambiguous and subjective results. Therefore, a method that incorporates the two equally important components (horizontal and vertical) is needed to facilitate groundwater protection zoning. The time-dependent model represents a redesigned vulnerability assessment method, created for karst aquifers, to incorporate the travel time component. This model incudes horizontal and vertical groundwater flow components and also considers a surface component toward ponor zones. The baseline for groundwater travel time through the unsaturated zone was adopted from the Time–input method. The estimation of the horizontal travel time component was based on the conceptual duality of flow in karst aquifers, which has fast and slow components. For the allogenic part of the karst aquifer catchment area (subcatchments of the ponor zone) travel time components were estimated according to different influencing factors e.g. slope, soil type, vegetation, and rainfall intensity. This methodology was tested on the case example of the Crnica karst source located at the western part of the Kucaj anticline in Eastern Serbia. The methodology was shown to be more accurate and appropriate for the delineation of the groundwater protection zones than existing approaches.

LPMLE3: A novel 1‐D approach to study water flow in streambeds using heat as a tracer

AbstractWe introduce LPMLE3, a new 1‐D approach to quantify vertical water flow components at streambeds using temperature data collected in different depths. LPMLE3 solves the partial differential equation for coupled water flow and heat transport in the frequency domain. Unlike other 1‐D approaches it does not assume a semi‐infinite halfspace with the location of the lower boundary condition approaching infinity. Instead, it uses local upper and lower boundary conditions. As such, the streambed can be divided into finite subdomains bound at the top and bottom by a temperature‐time series. Information from a third temperature sensor within each subdomain is then used for parameter estimation. LPMLE3 applies a low order local polynomial to separate periodic and transient parts (including the noise contributions) of a temperature‐time series and calculates the frequency response of each subdomain to a known temperature input at the streambed top. A maximum‐likelihood estimator is used to estimate the vertical component of water flow, thermal diffusivity, and their uncertainties for each streambed subdomain and provides information regarding model quality. We tested the method on synthetic temperature data generated with the numerical model STRIVE and demonstrate how the vertical flow component can be quantified for field data collected in a Belgian stream. We show that by using the results in additional analyses, nonvertical flow components could be identified and by making certain assumptions they could be quantified for each subdomain. LPMLE3 performed well on both simulated and field data and can be considered a valuable addition to the existing 1‐D methods.

A three‐dimensional analysis on the role of atmospheric waves in the climatology and interannual variability of stratospheric final warming in the Southern Hemisphere

AbstractStratospheric final warming (SFW) in the Southern Hemisphere is examined in terms of their interannual variability and climatology using reanalysis data from January 1979 to March 2014. First, it is shown from a two‐dimensional transformed Eulerian mean (TEM) analysis that a time‐integrated vertical component of Eliassen‐Palm flux during the spring is significantly related with SFW date. To clarify the role of residual mean flow in the interannual variability of the SFW date, SFWs are categorized into early and late groups according to the SFW date and their differences are examined. Significant difference in potential temperature tendency is observed in the middle and lower stratosphere in early October. Their structure in the meridional cross section accords well with that of vertical potential temperature advection by the residual mean flow. Difference in heating rate by shortwave radiation is minor. These results suggest that the adiabatic heating associated with the residual mean flow largely affects polar stratospheric temperature during austral spring and SFW date. The analysis is extended to investigate the longitudinal structure by using a three‐dimensional (3‐D) TEM theory. The significant difference in potential temperature tendency is mainly observed around the Weddell Sea at 10 hPa. Next, climatological 3‐D structure of a vertical component of the residual mean flow in association with SFW is examined in terms of the effect on the troposphere. The results suggest that a downward residual mean flow from the stratosphere penetrates into underlying troposphere over East Antarctica and partly influences tropospheric temperature there.

Investigations of electrically driven liquid metal flows using an ultrasound Doppler flow mapping system

This paper presents a combined experimental and numerical study of the properties of a liquid metal flow inside a cylinder driven by the application of a strong electrical current. The interaction between the electric current running through the melt and the corresponding induced magnetic field produces so-called electro-vortex flows. We consider here a configuration of two parallel pencil electrodes immersed at the free surface. Velocity measurements were performed by means of the Ultrasound Doppler method. A linear array of 25 singular transducers was used to determine the two-dimensional pattern of the vertical flow component. Numerical simulations of the magnetohydrodynamic (MHD) problem were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. Experimental and numerical results reveal a complex three-dimensional flow structure of the liquid metal flow. In particular, two pronounced downward jets are formed below both electrodes. The flow structure appears to be symmetrical with respect to two vertical cross sections being perpendicular to each other and one of the two planes contains the electrodes. The comparison between the experimental data and the numerical results shows a very good agreement.

The effect of particle shape on mixing in a high shear mixer

Discrete element method modelling is used to study the effect of particle shape on the flow dynamics and mixing in a high shear mixer. The blade generates strong flow over its top surface while compacting and pushing forward particles that are directly in front of the blade. A complex three dimensional flow is established with vertical and radial flow components that are shape dependent and which control the nature of the mixing. Mixing was found to be fast in the azimuthal direction, of intermediate speed in the vertical direction and comparatively slow in the radial mixing. Diffusive mixing is characterised using the granular temperature which shows that the regions of higher granular temperature are larger for round particles than non-round ones leading to stronger diffusive mixing. The spatial distribution of the convective component of mixing is identified using novel calculation of shear strain rate. This size and shape of the high shear region is found to be only slightly sensitive to the particle shape indicating that the convective mixing is relatively independent of shape, except in the middle of the mixer. The blockiness of the particles has the strongest impact on flow and mixing while the mixing has only a weak dependence on the particle aspect ratio.

Origin and recharge mechanisms of groundwater in the upper part of the Awaj River (Syria) based on hydrochemistry and environmental isotope techniques

The Barada and Awaj basin is the most important and extensively used water basin in Syria. Chemical and isotopic data of groundwater have been used to determine the spatial distribution of hydrogeological features in the upper part of Awaj River catchment area located southwest of this basin. Hydrogeochemical evolution of groundwater reveals the domination of dissolution/precipitation mechanisms in these very complex stratigraphic sequences. The dissolution of carbonate rocks as well as reverse cation exchange processes seem to be the main factors controlling groundwater mineralization. The isotopic composition of precipitation and groundwater indicate that the modern-day atmospheric precipitation is the main source of groundwater recharge before an important evaporation occurred. The isotopic data also imply an existence of hydraulic connection between the different aquifers system. The results obtained allowed us to delineate two main spatial groundwater zones within the study area with different flow components. The south, central and eastern parts are considered to be one zone which is characterised by a shallow horizontal flow associated with active interaction between groundwater and hosting rocks. The nitrate concentrations in this zone are attributed to anthropogenic sources. The second zone consists in south-western, western and north-western parts where the karstic features are well developed mainly in the Jurassic strata. This zone is characterized by a high vulnerability to pollution confirmed by high values of nitrate coming from sewage water. The deep vertical groundwater flow component seems to be dominant in this zone and is controlled by fractures and geological structures.

Lowermost mantle flow at the eastern edge of the African Large Low Shear Velocity Province

Observations of seismic anisotropy in the lowermost mantle are plentiful, but their interpretation in terms of mantle flow remains challenging. Here we interrogate the anisotropic structure of the lowermost mantle beneath the Afar region, just outside the edge of the African Large Low Shear Velocity Province, using a combination of shear wave splitting techniques applied to phases propagating at five distinct raypath orientations. We then model the resulting data set by testing various candidate mechanisms for anisotropy. The observations are best fit by a model that invokes the lattice preferred orientation (LPO) of post-perovskite, with the [100] crystallographic axis oriented either nearly vertically or highly obliquely to the horizontal plane. Plausible corresponding mantle flow scenarios involve a significant vertical flow component, which suggests that the African Large Low Shear Velocity Province edge may deflect ambient mantle flow upwards or may be associated with a sheet-like upwelling.

Calibration and application of an automated seepage meter for monitoring water flow across the sediment-water interface.

The advective flow of sediment pore water is an important parameter for understanding natural geochemical processes within lake, river, wetland, and marine sediments and also for properly designing permeable remedial sediment caps placed over contaminated sediments. Automated heat pulse seepage meters can be used to measure the vertical component of sediment pore water flow (i.e., vertical Darcy velocity); however, little information on meter calibration as a function of ambient water temperature exists in the literature. As a result, a method with associated equations for calibrating a heat pulse seepage meter as a function of ambient water temperature is fully described in this paper. Results of meter calibration over the temperature range 7.5 to 21.2 °C indicate that errors in accuracy are significant if proper temperature-dependence calibration is not performed. The proposed calibration method allows for temperature corrections to be made automatically in the field at any ambient water temperature. The significance of these corrections is discussed.

Scale-resolving simulation to predict the updraught regions over buildings for MAV orographic lift soaring

Birds have been observed to soar over ridges, mountains and cliffs to extend their flight duration with minimal energy expenditure. There is an opportunity to replicate this behavior to enhance the flight duration of Micro Aerial Vehicles (MAVs) which operate in urban environments by exploiting the vertical flow component (orographic lift) of flow over buildings. This paper therefore studies the flow field in a representative urban environments to enhance the operational capability of MAV platforms by increasing range and endurance. The feasibility and benefits of employing Computational Fluid Dynamics (CFD) are investigated, to simulate the turbulent wind flow conditions around a building configuration. A three-dimensional, scale-resolving simulation, utilizing a derivative of the Detached Eddy Simulation approach was considered. The atmospheric boundary layer velocity and turbulent intensity profiles were calibrated at the inlet boundary of the computational domain, to replicate nominal operating conditions. Recent validation of the Improved Delayed Detached Eddy Simulation (IDDES) approach has shown excellent agreement for a number of relevant flows. This provided the motivation for the study of a full-scale multi-building configuration, and suggests that the use of high-fidelity turbulence modeling is able to predict updraught regions of buildings in an urban environment.

Performance of three pilot-scale hybrid constructed wetlands for total coliforms and Escherichia coli removal from primary effluent - a 2-year study in a subtropical climate.

Three pilot-scale two-stage hybrid constructed wetlands were evaluated in order to compare their efficiency for total coliforms (TCol) and Escherichia coli removal and to analyze their performances in two 1-year periods of experimentation. System I consisted of a horizontal flow (HF) constructed wetland (CW) followed by a stabilization pond. System II was also configured with a HF CW as a first stage which was then followed by a vertical flow (VF) CW as a second stage. System III was configured with a VF CW followed by a HF CW. In the first year of evaluation, the HF-VF system was the most effective for TCol removal (p < 0.05) and achieved a reduction of 2.2 log units. With regard to E. coli removal, the HF-VF and VF-HF systems were the most effective (p < 0.05) with average reductions of 3.2 and 3.8 log units, respectively. In the second year, the most effective were those with a VF component for both TCol and E. coli which underwent average reductions of 2.34-2.44 and 3.44-3.74 log units, respectively. The reduction achieved in E. coli densities, in both years, satisfy the World Health Organization guidelines that require a 3-4 log unit pathogen reduction in wastewater treatment systems.

Comparative Study of Three Two-Stage Hybrid Ecological Wastewater Treatment Systems for Producing High Nutrient, Reclaimed Water for Irrigation Reuse in Developing Countries

In this study, three different two-stage hybrid ecological wastewater treatment systems (HEWTS) with combinations of horizontal flow (HF) constructed wetlands (CWs), vertical flow (VF) CWs and stabilization ponds (SP) were evaluated for the removal of Organic-N, NH4+, NO3−, Total N, Total P, Total Coliforms (TCol) and Escherichia Coli, BOD, COD and TSS. The overall goal of the study was novel in comparison to most other studies in that we sought to evaluate and compare the efficiency of the three HEWTSs for water quality improvements, while minimizing nutrient removal from the wastewater in order to generate high quality reclaimed water for reuse for irrigation of crops. The most effective systems were those systems containing a vertical flow component, either HF-VF or VF-HF. In these two HEWTS, NH4+ was reduced by 85.5% and 85.0% respectively, while NO3− was increased to 91.4 ± 17.6 mg/L and to 82.5 ± 17.2 mg/L, respectively, an artifact of nitrification. At the same time, E. coli was reduced by 99.93% and 99.99%, respectively. While the goal of most wastewater treatment is focused on reducing nutrients, the results here demonstrate that two-stage HEWTSs containing VF components can be used to produce a high quality effluent while retaining inorganic nutrients, thereby conserving this valuable resource for reuse as irrigation water for agriculture in subtropical developing countries where water and fertilizer resources are scarce or expensive.

Geochemistry and geochronology of the Jim Sage volcanic suite, southern Idaho: Implications for Snake River Plain magmatism and its role in the history of Basin and Range extension

The Jim Sage volcanic suite (JSVS) exposed in the Jim Sage and Cotterel Mountains of southern Idaho (USA) consists of two volcanic members composed of ∼240 km3 of Miocene rhyolite lavas separated by an interval of lacustrine sediments. It is capped by rheomorphic ignimbrite and as much as 100 m of basaltic lava flows probably derived from the central Snake River Plain (SRP) province to the north. The occurrence of volcanic vents in the JSVS links the lava flows to their local eruptive centers, while the adjacent Albion–Raft River–Grouse Creek metamorphic core complex exposes ∼3000 km2 of once deep-seated rocks that offer constraints on the composition of the potential crustal sources of these rhyolites. U-Pb zircon ages from the rhyolite lavas of the JSVS range from 9.5 to 8.2 Ma. The Miocene basalt of the Cotterel Mountains has an 87Sr/86Sri composition of 0.7066–0.7075 and ɛNd(i) = –3.7, and the rhyolite lavas of the JSVS have 87Sr/86Sri = 0.7114–0.7135 and eNd(i) values that range from –6.7 to –7.1. Zircon from the rhyolites of the JSVS range in δ18Ozr (Vienna standard mean ocean water, VSMOW) from –0.5‰ to 5.7‰ and have eHf(i) values ranging from –0.8 to –6.8. Based on geochronology, whole-rock major elements, trace elements, isotopes (Sr and Nd), and in situ zircon O and Hf isotopic compositions, we infer that the JSVS is genetically related to the central SRP province. The eruption of the low-δ18O rhyolites of the JSVS, outside of the main topographic extent of the SRP province (without the large calderas inferred for the SRP rhyolites) implies that there might be an alternative mechanism for the formation of the low-δ18O signature other than the proposed assimilation of hydrothermally altered caldera blocks. One suggestion is that the north to south propagation of SRP-type low-δ18O rhyolitic melt along the Albion fault led to off-axis magmatism. Another possibility is that there was prior and widespread (across a region wider than the SRP) hydrothermal alteration of the crust related to its earlier magmatic and faulting history. The eruption of SRP-type lavas in the hanging wall of an evolving metamorphic core complex helps us outline the role of the SRP magmatic province in the extensional evolution of the northeastern Basin and Range. The lavas of the JSVS imply the addition of basalt, related to the SRP hotspot, to the crust beneath the Raft River Basin that provided a heat source for crustal melting and weakening of the deep crust; this led to a vertical component of crustal flow and doming during extension, after the eruption of the 9.5–8.2 Ma JSVS rhyolites. This younger than 8.2 Ma component of vertical motion during faulting of the Miocene stratified sequence of the Raft River Basin and the rotation of the Albion fault to shallower angles collectively resulted in the subhorizontal detachment structure imaged seismically beneath the Raft River Basin.

Low head hyperfiltration through intact Burlington Limestone and Jefferson City Dolomite discs

Hyperfiltration is the ability of a membrane to retard the passage of a solute under a hydraulic head in excess of osmotic pressure. Disaggregated and recompacted shales, mudstones, clays and tuff have been shown to exhibit hyperfiltration-induced membrane effects in past experiments. However, limestone and dolomite have not previously been tested. Therefore, eight hyperfiltration experiments were performed on intact Burlington Limestone and Jefferson City Dolomite to assess the membrane properties of these lithologies. Four experiments were conducted on each lithology using 0.0050 and 0.0100M Cl− solutions at heads of 0.50 and 1.00m. Reflection coefficients, a measure of osmotic efficiency, ranged from 0.34 to 0.39 for the Burlington Limestone and 0.32 to 0.40 for the Jefferson City Dolomite. At the end of the hyperfiltration experiments, Cl− was concentrated within the cell above input concentrations by 85–95% for the Burlington Limestone and 79–105% for the Jefferson City Dolomite. An additional experiment passed 0.0020M dissolved silica solution through the Burlington Limestone at a head of 0.965bar (14psi). The final concentration of silica within the cell was 0.0043M dissolved silica at steady-state; a concentration 114% higher than the original input solution concentration. The reflection coefficient for this experiment was calculated to be 0.33. The results of these experiments suggest that membrane properties in these lithologies may be worthy of consideration in some geologic scenarios, including: (1) shallow or perched aquifers bounded by thin limestone or dolomite strata, (2) overpressured aquifers bounded by limestone or dolomite, (3) limestone or dolomite bounded aquifers with significant vertical components of flow, and (4) facies changes with significant lateral component of flow bounded by either lithology. Furthermore, the results suggest that silica cementation may be possible even under relatively low head conditions. Cementation due to hyperfiltration, even at shallow depths and low pressures should be further investigated. Similarly, other low permeability lithologies lacking a charged surface could potentially function as geologic membranes.

A 3D analysis algorithm to improve interpretation of heat pulse sensor results for the determination of small-scale flow directions and velocities in the hyporheic zone

The hyporheic zone is strongly influenced by the adjacent surface water and groundwater systems. It is subject to hydraulic head and pressure fluctuations at different space and time scales, causing dynamic and heterogeneous flow patterns. These patterns are crucial for many biogeochemical processes in the shallow sediment and need to be considered in investigations of this hydraulically dynamic and biogeochemical active interface. For this purpose a device employing heat as an artificial tracer and a data analysis routine were developed. The method aims at measuring hyporheic flow direction and velocity in three dimensions at a scale of a few centimeters. A short heat pulse is injected into the sediment by a point source and its propagation is detected by up to 24temperature sensors arranged cylindrically around the heater. The resulting breakthrough curves are analyzed using an analytical solution of the heat transport equation. The device was tested in two laboratory flow-through tanks with defined flow velocities and directions. Using different flow situations and sensor arrays the sensitivity of the method was evaluated. After operational reliability was demonstrated in the laboratory, its applicability in the field was tested in the hyporheic zone of a low gradient stream with sandy streambed in NE-Germany. Median and maximum flow velocity in the hyporheic zone at the site were determined as 0.9×10−4 and 2.1×10−4ms−1 respectively. Horizontal flow components were found to be spatially very heterogeneous, while vertical flow component appear to be predominantly driven by the streambed morphology.

Subsurface Supergranular Vertical Flows as Measured Using Large Distance Separations in Time–Distance Helioseismology

As large-distance rays (say, 10 – 24°) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large-separation travel times associated with supergranulation cannot be studied using the standard phase-speed filters of time–distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations, reduce the resultant travel-time signal by at least an order of magnitude at some distances. More effective filters are derived. Modeling suggests that the center–annulus travel-time difference [δt oi] in the separation range Δ=10 – 24∘ is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a constant signal from the vertical flow. Our measurement of this quantity, 5.1±0.1 seconds, is constant over the distance range. This magnitude of the signal cannot be caused by the level of upflow at cell centers seen at the photosphere of 10 m s−1 extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of 240 m s−1 at a depth of 2.3 Mm and a peak horizontal flow of 700 m s−1 at a depth of 1.6 Mm.

Photoresist Spray Coating Using a Shield Plate with an Aperture for Uniform Deposition onto Trench-Type Three-Dimensional Microdevice Structures

The spray coating of a photoresist using a shield plate with an aperture is carried out for uniform deposition onto three-dimensional (3D) trench structures. The shield plate set over a sample blocks resist deposition onto the sample, except in the aperture area. Numerical analysis reveals that the vertical velocity component of gas flow is enhanced in the aperture area. In experiments on spray coating, the difference between the thicknesses of resist films deposited on top and bottom trench surfaces is decreased. On the trench sidewall, resist bump formation, which is frequently observed in spray coating, is suppressed. The profile of the resist film becomes conformal and uniform. Such resist deposition is necessary to realize 3D microdevices. In microfluidic devices using dielectrophoresis, aside from the top and bottom trench surfaces, the trench sidewall can be used for preparing device structures such as electrode. Electric interaction is enhanced for controlling the transport of micro-/nano-scale objects in micro-trench structures.