Inflow Zone Research Articles

Seasonal growth pattern of Phalaris arundinacea in constructed wetlands with horizontal subsurface flow

Plants play import role in constructed wetlands (CWs) with horizontal subsurface flow. It has been well documented that planted constructed wetlands are more efficient that filters with vegetation. Also, it has been found that plant species may differ in their effect on wastewater treatment. However, there has been little attention paid to the management of vegetation with the focus on enhanced nutrient removal. During the period April 2012–March 2013 seasonal development of aboveground biomass of Phalaris arundinacea (Reed canarygrass) has been evaluated at two constructed wetlands in the Czech Republic. Both systems were sampled on a monthly basis and triplicate samples were taken in both inflow and outflow zones. It has been found that the aboveground biomass was substantially higher in the inflow zone in both surveyed CWs and this phenomenon was also found in six other CWs where aboveground biomass was sampled during the peak biomass period. Besides that, it has been found that the peak biomass in the outflow zone occurred about two months later than in the inflow zone. This information could be used for biomass harvest management aimed at enhancing nutrient removal. The results of this study revealed that if inflow and outflow zones are harvested separately at different periods of the growing season, the amount of nitrogen and phosphorus removed via harvesting may increase up to 42% and 43%, respectively as compared to a single harvest of the whole surface of the filtration beds.

Identification of the Inflow Zone of Unruptured Cerebral Aneurysms: Comparison of 4D Flow MRI and 3D TOF MRA Data

The hemodynamics of the inflow zone of cerebral aneurysms may be a key factor in coil compaction and recanalization after endovascular coil embolization. We performed 4D flow MR imaging in conjunction with 3D TOF MRA and compared their ability to identify the inflow zone of unruptured cerebral aneurysms. This series comprised 50 unruptured saccular cerebral aneurysms in 44 patients. Transluminal color-coded 3D MRA images were created by selecting the signal-intensity ranges on 3D TOF MRA images that corresponded with both the luminal margin and the putative inflow. 4D flow MR imaging demonstrated the inflow zone and yielded inflow velocity profiles for all 50 aneurysms. In 18 of 24 lateral-projection aneurysms (75%), the inflow zone was located distally on the aneurysmal neck. The maximum inflow velocity ranged from 285 to 922 mm/s. On 4D flow MR imaging and transluminal color-coded 3D MRA studies, the inflow zone of 32 aneurysms (64%) was at a similar location. In 91% of aneurysms whose neck section plane angle was <30° with respect to the imaging section direction on 3D TOF MRA, depiction of the inflow zone was similar on transluminal color-coded 3D MRA and 4D flow MR images. 4D flow MR imaging can demonstrate the inflow zone and provide inflow velocity profiles. In aneurysms whose angle of the neck-section plane is obtuse vis-a-vis the imaging section on 3D TOF MRA scans, transluminal color-coded 3D MRA may depict the inflow zone reliably.

Inviscid limit for Navier–Stokes equations in domains with permeable boundaries

Abstract This work is concerned with 2D-Navier Stokes equations in a multiply-connected bounded domain with permeable walls. The permeability is described by a Navier type condition. Our aim is to show that the inviscid limit is a solution of the Euler equations, satisfying the Navier type condition on the inflow zone of the walls.

The Pipeline embolization device for treatment of intracranial aneurysms

Flow diversion is a new endovascular technique developed for treatment of intracranial aneurysms. It is based on stent-induced modification of blood flow within and around an aneurysm inflow zone, leading to gradual intra-aneurysmal thrombosis and subsequent atrophy, while preserving flow into the parent vessel and perforating branches. Flow-diversion technique is well-suited for the treatment of large, giant, wide-necked, and fusiform intracranial aneurysms because it does not rely on endosaccular packing with coils but rather on the strategy of placing a stent across the aneurysm “neck” or across the diseased segment of a vessel in case of a fusiform aneurysm. Over time, neointimal endothelium covers the flow diverter such that it becomes incorporated into the parent vessel wall and occludes the aneurysm from the circulation, effectively repairing the diseased parent vessel segment. This report describes in detail the Pipeline embolization device (ev3-Covidien, Irvine, California, USA), its mechanism of action and deployment technique, and reviews the pertinent literature regarding safety, efficacy and potential risks and complications associated with the use of this flow diverter.

Tracer-based Quantification of Individual Frac Discharge in Single-well Multiple-frac Backflow: Sensitivity Study

The use of artificial tracers as a tool for matrix and fracture (-network) characterization is examined in conjunction with a variety of geothermal-related fracturing operations in Germany, either chemical-based or plain-hydraulic, with or without proppants, both with short-term tracings (during and immediately after fracturing) and for long-term production monitoring, in sedimentary and crystalline formations in the N-German Basin, at the sites Horstberg and Groß Schönebeck. As an outcome of tracer test analysis for the latter site, a tool for the tracer-based quantification of individual frac discharge in single-well multiple-frac backflow and production can be derived, whose major advantage consists in using only stable conservative tracers, and in its independence from hydrogeological a priori knowledge. This tool can also be applied in unconventional hydrocarbon reservoir development and operation, where assessing the uniformity of multiple inflow zones is crucial to reservoir economics; complimentary use of reactive alongside with conservative tracers, with dual partitioning behavior for source and daughter species, enables to further determine the relevant hydrogeologic parameters of producing fracs or matrix ‘damage’ zones, independently of their productivity.

Stent recanalization of carotid tonsillar loop dissection using the Enterprise vascular reconstruction device

Although advances in endovascular techniques have permitted reconstruction of intimal dissections and related pseudoaneurysms of the extracranial cervical internal carotid artery, highly tortuous tonsillar loop anatomic variants still pose an obstacle to conventional extracranial self-expanding carotid stents. During a 12year period, nine of 48 cases with cervical carotid dissections were associated with a tonsillar loop. Five patients required endovascular treatment, which was performed using a microcatheter-based technique with the low-profile Enterprise vascular reconstruction device (Codman Neurovascular, Raynham, MA, USA). Technical, radiographic, and clinical outcomes were analyzed for each patient. Dissection etiology was spontaneous in three patients, iatrogenic in one, and traumatic in one. Four near-occlusive tonsillar loop dissections were successfully recanalized during the acute phase. Dissection-related stenosis improved from 90±22% to 31±13%, with tandem stents needed in three instances to seal the inflow zone. There were no procedure-related transient ischemic attacks (TIA), minor/major strokes, or deaths. Angiographic follow-up for a mean of 28.0±21.6months showed all stents were patent, with average stenosis of 25.2±12.2%. Focal ovalization and kinking of the closed-cell design was noted at the sharpest curve in one patient. Clinical outcome (follow-up of 28.1±21.5months) demonstrated overall improvement with no clinical worsening, new TIA, or stroke. Tonsillar loop-associated carotid dissections can be successfully and durably recanalized using the low-profile Enterprise stent with an excellent long-term patency rate and low procedural risk. The possibility of stent kinking and low radial force should be considered when planning reconstruction with this device.

Vegetation development in subsurface flow constructed wetlands in the Czech Republic

Wetland macrophytes play many important indirect roles in constructed wetlands with horizontal subsurface flow (HF CWs) including insulation of the bed surface during winter, provision of substrate for attached bacteria in the rhizosphere or oxygen leakage into anoxic rhizosphere. In the Czech Republic, HF CWs are mostly planted with Phragmites australis (Common reed) or Phalaris arundinacea (Reed canarygrass) or with a combination of these two species. The early systems were planted only with Phragmites according to the then available information from abroad. Later, Phalaris was used because of easy planting and fast growth. In 2011, macrophyte survey of 55 HF CWs in the Czech Republic was carried out with the aim to identify “weedy” species, i.e., species which were not originally planted. During the survey, 83 macrophyte “weedy” species were recorded with more species being found in the outflow zone (74) as compared to inflow zone (46). However, most species were found only as individual plants in the filtration bed margins with the exception of Urtica dioica (Stinging nettle) in the inflow zone and Epilobium hirsutum (Hairy willowherb) in the outflow zone of several systems. It has been found that the number of “weedy” species decreases with increasing length of operation. In systems, where “weedy” species overgrew the originally planted species, treatment efficiency was not affected.

E-062 Coiling Cost per Volume Analysis and Strategy for Cost Reduction

Introduction/PurposeAneurysm treatment is a major revenue driver of neurointerventional surgery. The cost of devices used during treatment has a direct effect on the profitability and financial sustainability of a given...

Seasonal variations in groundwater upwelling zones in a Danish lowland stream analyzed using Distributed Temperature Sensing (DTS)

The distribution of groundwater inflows in a stream reach plays a major role in controlling the stream temperature, a vital component shaping the riverine ecosystem. In this study, the Distributed Temperature Sensing (DTS) system was installed in a small Danish lowland stream, Elverdamsåen, to assess the seasonal dynamics of groundwater inflow zones using high spatial (1 m) and temporal (3 minutes) resolution of water temperature measurements. Four simple criteria consisting of 30 min average temperature at 16:00, mean and standard deviation of diurnal temperatures, and the day–night temperature difference were applied to three DTS datasets representing stream temperature responses to the variable meteorological and hydrological conditions prevailing in summer, winter and spring. The standard deviation criterion was useful to identify groundwater discharge zones in summer and spring conditions, while the mean temperature criterion was better for the winter conditions. In total, 20 interactions were identified from the DTS datasets representing summer, 16 in winter and 19 in spring, albeit with only two interactions contributing in all three seasons. Higher baseflow to streamflow ratio, antecedent precipitation and presence of fractured clayey till in the stream reach were deemed as the vital factors causing apparent seasonal variation in the locations of upwelling zones, prompting use of DTS not only in preconceived scenarios of large diurnal temperature change but rather a long-term deployment covering variable meteorological and hydrological scenarios. Copyright © 2012 John Wiley & Sons, Ltd.

The Development of a New Methodology to Interpret Run oi River Salinity Data to Assess Salt Inflow to The River Murray

In addition to the threat posed by high salinity to drinking water, increased salinity in the River Murray also represents a threat to the health of floodplains, wetlands and may increase the costs of infrastructure maintenance. In the Lower Murray Basin most of the salts in the river originate from groundwater. Run of river salinity surveys are used to measure salt inflow. They measure electrical conductivity every kilometre over five consecutive days, at low and steady river flows. For a robust interpretation of salt inflow, the background electrical conductivity has to be removed from the measurements. The existing methodology is robust for analysing cumulative salt inflows over river reaches but assigns salt inflows up to several kilometres downstream from where they actually occur. A new method has therefore been developed to assign the salt inflow more closely to the location where it actually occurs and at the correct rate. The new methodology is based on the assumptions that salt inflow is the function of space only (during the survey) and the background conductivity can be described by the temporal variations observed at a fixed location. These in turn allow better targeting of the high salt inflow zones for salt interception.

The development of a new methodology to interpret run of river salinity data to assess salt inflow to the River Murray

In addition to the threat posed by high salinity to drinking water, increased salinity in the River Murray also represents a threat to the health of floodplains, wetlands and may increase the costs of infrastructure maintenance. In the Lower Murray Basin most of the salts in the river originate from groundwater. Run of river salinity surveys are used to measure salt inflow. They measure electrical conductivity every kilometre over five consecutive days, at low and steady river flows. For a robust interpretation of salt inflow, the background electrical conductivity has to be removed from the measurements. The existing methodology is robust for analysing cumulative salt inflows over river reaches but assigns salt inflows up to several kilometres downstream from where they actually occur. A new method has therefore been developed to assign the salt inflow more closely to the location where it actually occurs and at the correct rate. The new methodology is based on the assumptions that salt inflow is the function of space only (during the survey) and the background conductivity can be described by the temporal variations observed at a fixed location. These in turn allow better targeting of the high salt inflow zones for salt interception.

Selective Endovascular Aneurysm Neck Ligation to Treat Compressive Cranial Neuropathy

To report a novel endovascular coiling technique for ligation of aneurysms presenting with cranial neuropathy. We describe three patients (all female, median age: 57) presenting with unruptured, mass effect producing, aneurysms. All three were treated with coiling of the aneurysm inflow zone without deploying coils in the dome or fundus. Their clinical manifestations, the radiologic features of the aneurysms, and details of endovascular inflow zone ligation are presented. Clinical and radiological improvement was seen in all three patients after 6-12 months follow-up. This technique may be considered in patients presenting with compressive cranial neuropathy and an aneurysm configuration that allows selective coiling of the inflow zone.

Turbulence measurements in spatially-varied flow with increasing discharge

This experimental study explores the distribution of Reynolds shear stresses and turbulence intensities for a flume receiving lateral inflow via a set of vertical nozzles. The data set allows for developing turbulence models to describe a wider range of spatially-varied flow conditions. The turbulent flow structures are detailed both in the near-field close to where the flow enters the flume, and in the far-field. It was found that a lateral inflow increases the turbulence level, but it decreases in the transverse direction towards the side walls. As the lateral inflow rate increases, the turbulence parameters increase only slightly. The turbulence parameters also increase from the upstream end of the lateral inflow zone towards the downstream end. The turbulent kinetic energy (TKE) production was estimated. Small regions of negative TKE production exist, which are typically near the lateral inflow addition.

Numerical Prediction of Wind Flow Around Irregular Models

This paper presents numerical predictions of flow around irregular-plan buildings (S-, R-, L- and U-shaped models) in high Reynolds number. The adopted computational approach and numerical models are described firstly. Then comparative analysis with the numerical and experimental data has been conducted to verify the reliability of the numerical predictions. Finally, characteristics of mean and fluctuating pressure distributions and vertical and lateral velocity profiles of the flow around the four models have been investigated and assessed thoroughly. The study shows that satisfactory results can be obtained by large eddy simulation (LES), especially when fluctuating wind velocity is considered in the inflow boundary. Distribution of mean pressure coefficients on front faces is relatively regular. Large fluctuating pressure coefficients are induced by strong vortex motion. Velocity profiles of wind flow are disturbed obviously among the four building models, especially in weak flow. The disturbed intensity decreases with increasing of the distance away from bluff body. The suggested MDS (Maximum Disturbance Scopes) away from bluff body are generally 0.25H in inflow zones, 0.4H in roof zones, 0.5H in both side zones and 3H in weak zones.

Iron and manganese in sediments of constructed wetlands with horizontal subsurface flow treating municipal sewage

In 2008, concentrations of iron and manganese in the sediments of seven constructed wetlands (CWs) with horizontal subsurface flow in the Czech Republic were evaluated. The surveyed constructed wetlands varied in the length of operation between 2 and 16 years at the time of sampling. In each constructed wetland three samples of sediment were taken in the inflow, middle and outflow zones to the depth of 0.6m. The sample was divided into top (0–20cm) and bottom (20–60cm) sections, resulting in a total number of 18 samples in each system. In each sample the amount of sediment on dry mass basis was evaluated and concentrations of Fe and Mn in the sediment were determined using ICP-MS. The survey revealed that the amount of sediments in the filtration bed increases with the length of operation. In general, more sediments were located at the bottom layers due to the wastewater distribution near the bottom. Concentrations of manganese in the sediment were highest in the new systems and decreased with length of operation. With the exception of one CW, in all other constructed wetlands Mn concentration in the sediment was significantly higher within the top layer. Mn concentrations in sediments found in this study were found within the concentration range commonly occurring in natural unpolluted wetlands. Iron concentration in the sediment also decreased with the increasing length of operation but the dependence on the operation time was not as clear as for manganese. The concentration of iron was comparable with other studies from constructed wetlands treating sewage but higher as compared to polluted sediments which are usually highly anaerobic. The results clearly demonstrated that in order to evaluate the amount of iron and manganese in the filtration beds it is necessary to take into consideration both concentration of the elements and the amount of sediment accumulated in the filtration bed. Despite the lowest concentrations in the sediment the highest accumulated amount of both iron and manganese was found in the oldest CW Spálené Poříčí because of the highest concentration of sediment in the filtration bed.

A Modeling Study on the Development of a Bowing Structure and Associated Rear Inflow within a Squall Line over South China

Abstract Through convection-permitting simulations, this study examines a large bowing structure within a squall line that occurred during the rainy season in South China. The bowing structure is closely associated with a local enhancement of (and balance between) the cold pool and the line-normal environmental low-level vertical shear. Rear inflow plays an essential role in the formation and evolution of this large bowing structure. It is found that the low-level rear inflow is largely a natural consequence of the baroclinically generated horizontal vorticity near the surface, while the midtropospheric rear inflow is forced by several pairs of bookend vortices. Vorticity budget and vortex-line analyses show that the bookend vortices form mainly through the tilting of horizontal vorticity. Consolidation of these pairs of bookend vortices forms a broad zone of contiguous rear inflow. The environmental flow and horizontal pressure gradient force associated with the midlevel pressure deficit induced by the rearward-tilting buoyant updrafts, on the other hand, are not primarily responsible for the formation of the rear inflow.

Radiatively inefficient accretion: breezes, winds and hyperaccretion

We reformulate the adiabatic inflow-outflow (ADIOS) model for radiatively inefficient accretion flows, treating the inflow and outflow zones on an equal footing. For purely adiabatic flows (i.e., with no radiative losses), we show that the mass flux in each zone must satisfy Mdot ~ R^n with n=1, in contrast to previous work in which 0<n< 1 is a free parameter but in rough agreement with numerical simulations. We also demonstrate that the resulting two-zone ADIOS models are not dynamically self-consistent without the introduction of an energy source close in to the central regions of the flow; we identify this with the energy liberated by accretion. We explore the parameter space of non-radiative models and show that both powerful winds and gentle breezes are possible. When small radiative losses (with fixed efficiency) are included, any centrally injected energy flux is radiated away and the system reverts to a power-law behavior with n < 1, where n falls in a small range determined by the fractional level of radiative losses. We also present an ADIOS model for hypercritical (super-Eddington) disk accretion, in which the radiative losses are closely related to the flow geometry. We suggest that hyperaccretion can lead to either winds or breezes.

Flow characteristics in a canine aneurysm model: A comparison of 4D accelerated phase‐contrast MR measurements and computational fluid dynamics simulations

Our purpose was to compare quantitatively velocity fields in and around experimental canine aneurysms as measured using an accelerated 4D PC-MR angiography (MRA) method and calculated based on animal-specific CFD simulations. Two animals with a surgically created bifurcation aneurysm were imaged using an accelerated 4D PC-MRA method. Meshes were created based on the geometries obtained from the PC-MRA and simulations using "subject-specific" pulsatile velocity waveforms and geometries were then solved using a commercial CFD solver. Qualitative visual assessments and quantitative comparisons of the time-resolved velocity fields obtained from the PC-MRA measurements and the CFD simulations were performed using a defined similarity metric combining both angular and magnitude differences of vector fields. PC-MRA and image-based CFD not only yielded visually consistent representations of 3D streamlines in and around both aneurysms, but also showed good agreement with regard to the spatial velocity distributions. The estimated similarity between time-resolved velocity fields from both techniques was reasonably high (mean value >0.60; one being the highest and zero being the lowest). Relative differences in inflow and outflow zones among selected planes were also reasonable (on the order of 10%-20%). The correlation between CFD-calculated and PC-MRA-measured time-averaged wall shear stresses was low (0.22 and 0.31, p < 0.001). In two experimental canine aneurysms, PC-MRA and image-based CFD showed favorable agreement in intra-aneurismal velocity fields. Combining these two complementary techniques likely will further improve the ability to characterize and interpret the complex flow that occurs in human intracranial aneurysms.

Removal of Nonionic Surfactants from Wastewater Using a Constructed Wetland

Removal of nonionic surfactants from municipal wastewater using a constructed wetland with a horizontal subsurface flow was studied in 2009 and 2010. Extraction spectrophotometry with 3',3″,5',5″-tetrabromophenolphthalein ethyl ester and KCl served to determine the analyte concentrations. Triton(®) X-100 was used as a standard to express the nonionic-surfactant concentrations. Anionic and cationic surfactants were shown not to interfere during the determination. Nonionic surfactants were degraded (to products undeterminable by the method) with a high average efficiency that reached 98.1% in 2009 and 99.1% in 2010, respectively. The average concentration of nonionic surfactants at the inflow was 0.978 mg/l, while it was close to the limit of quantification at the outflow (0.014 mg/l). A significant fraction of nonionic surfactants (38.7%) was already degraded during the pretreatment, and only 14.0% of the nonionic surfactants remained in the interstitial H(2) O taken in the vegetation bed at a distance of 1 m from the inflow zone at a 50-cm depth. Nonionic surfactants were degraded both under aerobic and anaerobic conditions.

The adverse effects of flow-diverter stent-like devices on the flow pattern of saccular intracranial aneurysm models: computational fluid dynamics study

Stent deployment across the aneurysmal neck has been established as one of the endovascular methods to treat intracranial aneurysms with or without coils. The purpose is to study the possible adverse effects of deployment of the new flow-diverter stent-like devices (FD) on the flow characteristics of saccular aneurysm models. Numerical simulations of the blood flow patterns in the artificial models of three aneurysms were studied. One model was designed without an FD stent, the second model with one FD stent, and the third model with two stents. Numerical simulation for incompressible laminar blood flow was conducted in the three artificial cerebral aneurysm models by means of computational fluid dynamics. There was a noticeable increase in the values of the circumferential pressure distributed on the walls of the aneurysm after stent deployment; this led to an increase the tension of the aneurysm surface and was considered to be an adverse effect. This pressure increase was further aggravated by the deployment of another stent. However, there is a beneficial effect of using FD stents, translating into the reduction of the flow velocity inside the aneurysm and wall shear stress at the inflow zone. This reduction decreases further with the deployment of another stent. Aneurysms become tenser after the deployment of one flow-diverter stent and (more tense still) after after the deployment of another stent. This principle should be kept in mind when choosing which group of aneurysms is the best candidate for such a treatment strategy. This study recommends deploying several FD stents during endovascular procedures until complete arrest of the blood flow occurs during the procedure; otherwise, the aneurysm may become tenser and dangerous if a slow blood flow jet still exists inside it at the end of the procedure.