Direct Flow Measurements Research Articles

Discharge estimation using a rating curve developed for the Upper Erer River, Wabisheble River Basin, Ethiopia

ABSTRACT The measurement of a stream flow is a vital component of water quality monitoring, geomorphology, and flooding investigations. However, the direct measurements of stream flow can be costly and challenging. To obtain a continuous record of discharge, typically the recorded stage and discharge are computed from the correlation of stage and discharge in the form of a rating curve. This study focused on the estimation of flow discharges using a rating curve equation based on data recorded at the Erer-Jijiga Bridge hydrometric station at the outlet of the upper Erer Sub-basin in Ethiopia for 2020–2021. The fitted rating curve was then used to estimate discharges from continuously recorded stages. The installation and operation of a gauging station in the Upper Erer Sub-basin will provide local and regional water sector administrators with more reliable estimates of discharge than would be available if the sub-basin was ungauged. This will also assist the local water sector to undertake water resource planning in the Upper Erer River Basin to better use the limited water resources in the region.

Bedside 3D ultrasound fistula maturation assessment by non-expert sonographers provides equivalent accuracy to formal duplex sonography: A prospective clinical trial.

EchoSure is an automated point-of-care 3D ultrasound (3DUS) designed to be used by dialysis technicians without advanced ultrasound training. The EchoMark/EchoSure System is a two-part system comprised of a bioresorbable implant, EchoMark, and a diagnostic ultrasound imaging platform, EchoSure. EchoSure was designed to enable any healthcare personnel in a dialysis clinic setting to obtain non-invasive, direct measurements of flow and vessel parameters that are critical quantifications used in the assessment of AVF maturation and readiness for hemodialysis cannulation. In this pilot feasibility study, we sought to explore whether use of an automated 3DUS could enable fistula assessment by non-experts and obtain measurement accuracy comparable to expert sonographer Duplex. This was a 20 subject prospective multicenter trial conducted at four sites in the United States. All subjects had an EchoMark implanted under their AVF during the fistula creation procedure. Subjects were evaluated at 2-weeks post-op with EchoSure and Duplex, followed by monthly assessments until either the 4-month visit or until radiographic maturation was achieved, whichever was longer. Beyond monthly ultrasound assessments, clinical follow-up continued every 6 months between months 6 and 24. Technical success of EchoMark implantation was demonstrated in 100% of subjects. Technical success of EchoSure was 99% across all scans. The mean percent difference in flow rate measurements between EchoSure and Duplex was -9.2% with a standard deviation of 38.1% compared to a mean percent difference of -15.7% with a standard deviation of 35.5% between Duplex measurements taken at the cannulation zone and brachial artery. Pearson correlation between EchoSure and Duplex was 0.708 versus 0.716 for the two Duplex measurements. Radiographic maturation was achieved in 70% of study subjects by 30 days and continued to rise to 90% through 90 days and 95% through 180 days after baseline. This study demonstrates the feasibility and accuracy of an automated 3D ultrasound system for assessment of maturation at the dialysis bedside by non sonographers.

Short communication: Characterizing arterial and venous blood gases over the gas exchange surface, the chorioallantoic membrane, of embryonic American alligators (Alligator mississippiensis) at two points of development

Assessments of arterial and venous blood gases are required to understand the function of respiratory organs in animals at different stages of development. We measured blood gases in the arteries entering and veins leaving the chorioallantoic membrane (CAM) in embryonic alligators (Alligator mississippiensis). The CAM accounts for virtually all gas exchange in these animals, and we hypothesized that the CAM vasculature would be larger in eggs incubated in hypoxia (10% O2 for 50% or 70% of incubation), which would be reflected in a lower partial pressure of CO2 (PCO2). Contrary to this hypothesis, our measurements revealed no effects of hypoxic incubation on PCO2, and seemingly no increase in vascularization of the CAM in response to incubation in 10% O2. PCO2 was lower on the venous side, but only significantly different from arterial blood at 70% of incubation. The calculated blood flow to the CAM increased with development and was lower in both groups of alligators that had been incubated in hypoxia. Future studies should include measurements of blood parameters taken from embryos held in conditions that mirror incubation O2 levels, in combination with direct measurements of CAM artery blood flow.

Unveiling the inherent physical-chemical dynamics: Direct measurements of hydrothermal fluid flow, heat, and nutrient outflow at the Tagoro submarine volcano (Canary Islands, Spain)

Tagoro is one of the few submarine volcanoes in the world that has been monitored since its early eruptive stage in 2011 to present day. After six multidisciplinary oceanographic cruises conducted between 2014 and 2023 to gather a comprehensive dataset of georeferenced video-imagery and in situ measurements of hydrothermal flow velocities and hydrothermal fluid samples, we provide a robust characterization of the ongoing hydrothermal fluid velocity, heat flux, and nutrient release, along with an accurate delimitation of the hydrothermal field area. Our results reveal that Tagoro hydrothermal system extends from the main hydrothermal crater up to the summit, covering an area of 7600 m2. This hydrothermal field comprises thousands of small individual vents, displaying diverse morphologies such as crevices and delicate chimney-like structures, irregularly scattered across the dominant diffuse venting surface. Hydrothermal fluid temperatures and velocities at the substratum level reveal a clustered spatial distribution, ranging from 21.0 to 33.3 °C and 1.6–26.8 cm min−1, respectively. Furthermore, our findings indicate a discernible correlation between hydrothermal fluid temperature and vent density, while significant differences were observed between velocities from diffuse and focused areas. Additionally, heat fluxes exceed 200 MW across the entire active region, with heat flux values ranging from 6.06 to 146.87 kW m−2 and dissolve inorganic nutrient concentrations exhibit significant enrichments, comparable to the magnitude of important nutrient sources in the area as upwelling systems or mesoscale structures.

Curie point depth from airborne magnetic data analysis for geothermal exploration in southern Thailand

Southern Thailand is a high heat flow region, which implies to high-potential area of geothermal resources. Direct heat flow measurements are only available from petroleum wells in Gulf of Thailand. Therefore, indirect method of Curie Point Depth (CPD) calculation has been used to evaluate the heat flow on land of southern Thailand. CPD is the theoretical depth at which subsurface temperature reaches the value of the Curie point of magnetite, which is 578 °C. CPD can be calculated by deriving the depth of the bottom of the magnetic body to the surface using spectral analysis from airborne magnetic data, and the calculated values can produce the CPD map of southern Thailand. The results show that CPD ranges from 7.88 to 19.75 km with an average of 13.74 km, and heat flow ranges from 61.54 to 154.25 mW/m2 with an average of 90.36 mW/m2. This study suggests that the high heat flow in southern Thailand, which is higher than the regular continental crust heat flow of 65 mW/m2, is possibly caused by a high heat anomaly from mantle upwelling and expressed through weak zones of faults and sutures in extensional tectonic regimes. The high heat from mantle has elevated by five zones: (1) Ranong faults zone, (2) Khlong Marui faults zone, (3) Coastline of Surat Thani and Nakhon Si Thammarat, (4) Trang and Satun zone, and (5) Bentong-Roab suture. These five zones are considered to be high-potential areas for future geothermal resources exploration.

Функционально-экологическая оценка и моделирование транспирации древостоя лесной экосистемы в условиях Москвы по данным IoT-систем мониторинга

The priority tasks of ecology include the development of modern systems of ecological monitoring and modeling of forest ecosystems, one of the main integral indicators of the functioning of which is the seasonal dynamics of stand transpiration. Most modern transpiration models are based on remote sensing data and operate on a very large scale. There are single models based on direct measurement of sap flow, which are difficult for ecologically sound geoinformation extrapolation on the territory of forest biogeocenoses with an area of several hectares, which is especially important for urban forest parks. The model we are planning should overcome these shortcomings. The article presents an approach to the assessment and modeling of the transpiration of the forest ecosystem stand according to the data of IoT monitoring systems in the Petrovsko-Razumovskoye integrated Nature reserve. Keywords: TRANSPIRATION, IOT, EDDY COVARIANCE, ENVIRONMENTAL MONITORING

The first direct measurements of ventilatory flow and oxygen utilization after exhaustive exercise and voluntary feeding in a teleost fish, Oncorhynchus mykiss.

A new "less invasive" device incorporating an ultrasonic flow probe and a divided chamber, but no stitching of membranes to the fish, was employed to make the first direct measurements of ventilatory flow rate (V̇w) and % O2 utilization (%U) in juvenile rainbow trout (37g, 8ºC) after exhaustive exercise (10-min chasing) and voluntary feeding (2.72% body mass ration). Under resting conditions, the allometrically scaled V̇w (300mlkg-1min-1 for a 37-g trout = 147mlkg-1min-1 for a 236-g trout exhibiting the same mass-specific O2 consumption rate, ṀO2) and the convection requirement for O2 (CR = 4.13 L mmol-1) were considerably lower, and the %U (67%) was considerably higher than in previous studies using surgically attached masks or the Fick principle. After exhaustive exercise, V̇w and ṀO2 approximately doubled whereas frequency (fr) and %U barely changed, so increased ventilatory stroke volume (Vsv) was the most important contributor to increased ṀO2. CR declined slightly. Values gradually returned to control conditions after 2-3h. After voluntary feeding, short-term increases in V̇w, Vsv and ṀO2 were comparable to those after exercise, and fr again did not change. However, %U increased so CR declined even more. The initial peaks in V̇w, Vsv and ṀO2, similar to those after exercise, were likely influenced by the excitement and exercise component of voluntary feeding. However, in contrast to post-exercise fish, post-prandial fish exhibited second peaks in these same parameters at 1-3h after feeding, and %U increased further, surpassing 85%, reflecting the true "specific dynamic action" response. We conclude that respiration in trout is much more efficient than previously believed.

Comparing direct and indirect glottal flow waveform measurements in excised canine larynges and synthetic vocal fold models

Despite being considered the gold standard technique for delineating the flow glottogram during phonation, the inverse filtering technique has never been validated against actual volume flow measurements. This signal-processingtechnique uses the speech signal with vocal tract estimates to calculate the glottal flow waveform. The lack of validation stems from the difficulty of obtaining in-vivo flow measurements at the glottal exit. The current study aims to assess the accuracy of the inverse filtering technique by comparing its flow glottograms with direct, simultaneous volume flow measurement. A vocal tract with varied constrictions that mimic its shape according to specific vowels was connected to either an excised canine larynx or a synthetic vocal fold model. Direct volume flow measurements at the glottal exit were done using tomographic particle image velocimetry. Indirect measurements were obtained by fitting the known Rothenberg mask to the vocal tract and estimating the glottal flow waveform using the Glottal Enterprise system. Preliminary results indicate that the accuracy of the inverse filtering technique relies on the degree of vocal tract constriction. The flow glottogram aligns well with front, lax, and unrounded lip vowels, but its accuracy diminishes with tense and round vowels, particularly noticeable with the excised canine larynx.

Statistical and machine learning application approach to predict mass flowrate

Flow measurement is one of the critical points in the industrial process measurement. Mass flow measurement, as an alternative flow measuring method, is usually chosen to prevent temperature effects to the density that would be impacted directly to the flow measurement. One of the most popular direct mass flow measurements is Coriolis Mass Flowmeter (CMF). CMF which has an accuracy of mass flow measurement up to 0.1% of reading, recently became widely used for valuable fluids mass flowrate measurement. The challenge of the flow measurement will not stop in the selection and the smart capabilities of the flow instrument itself; another issue that appears during process measurement is the absence of the installed CMF as a mandatory installed, local pressure measurement could be a physical parameter that could be used to predict the mass flowrate using statistical and machine learning algorithms. This virtual flow measurement method will be an approach to face the absence of physical flowmeter issues, especially in critical or remote operation processes.

Investigation of the Proton Exchange Membrane Fuel Cell System Cathode Exhaust Gas Composition Based on Test Bed Measurements

Proton exchange membrane fuel cells are gaining increasing importance in vehicle applications. The exhaust gas composition regarding the water and oxygen content and the mass flow are important parameters in fuel cell research (e.g., for designing the test bed, quantifying the hydrogen loss in the exhaust, performing experiments with air pollutants, and monitoring degradation). The exhaust gas composition is also important for vehicle applications (e.g., ensuring safe hydrogen levels in the exhaust). Performing direct measurements of the exhaust mass flow and the relative humidity is challenging due to the high-humidity environment. This article presents a mathematical thermodynamic model used to calculate the exhaust gas mass flow and relative humidity, validated by balancing the gas species composition between cathode inlet and exhaust and by using data measured at the fuel cell system test bed. Four calculation model variations and their analyses are discussed. Furthermore, the exhaust gas composition throughout the fuel cell system operating range is presented. The results of air pollutant experiments provide comprehensive examples for the application of the calculation model. These results demonstrate the suitability of the model for its application in fuel cell system research.

Assessment of renal sympathetic control using invasive pressure and flow velocity measurements in humans.

Renal sympathetic innervation is important in the control of renal and systemic hemodynamics and is a target for pharmacological and catheter-based therapies. The effect of a physiological sympathetic stimulus using static handgrip exercise on renal hemodynamics and intraglomerular pressure in humans is unknown. We recorded renal arterial pressure and flow velocity in patients with a clinical indication for coronary or peripheral angiography using a sensor-equipped guidewire during baseline, handgrip, rest, and hyperemia following intrarenal dopamine (30 μg/kg). Changes in perfusion pressure were expressed as the change in mean arterial pressure, and changes in flow were expressed as a percentage with respect to baseline. Intraglomerular pressure was estimated using a Windkessel model. A total of 18 patients (61% male and 39% female) with a median age of 57 yr (range: 27-85 yr) with successful measurements were included. During static handgrip, renal arterial pressure increased by 15.2 mmHg (range: 4.2-53.0 mmHg), whereas flow decreased by 11.2%, but with a large variation between individuals (range: -13.4 to 49.8). Intraglomerular pressure increased by 4.2 mmHg (range: -3.9 to 22.1 mmHg). Flow velocity under resting conditions remained stable, with a median of 100.6% (range: 82.3%-114.6%) compared with baseline. During hyperemia, maximal flow was 180% (range: 111%-281%), whereas intraglomerular pressure decreased by 9.6 mmHg (interquartile range: 4.8 to 13.9 mmHg). Changes in renal pressure and flow during handgrip exercise were significantly correlated (ρ = -0.68, P = 0.002). Measurement of renal arterial pressure and flow velocity during handgrip exercise allows the identification of patients with higher and lower sympathetic control of renal perfusion. This suggests that hemodynamic measurements may be useful to assess the response to therapeutic interventions aimed at altering renal sympathetic control.NEW & NOTEWORTHY Renal sympathetic innervation is important in the homeostasis of systemic and renal hemodynamics. We showed that renal arterial pressure significantly increased and that flow decreased during static handgrip exercise using direct renal arterial pressure and flow measurements in humans, but with a large difference between individuals. These findings may be useful for future studies aimed to assess the effect of interventions that influence renal sympathetic control.

Intra-Cardiac Flow from Geometry Prescribed Computational Fluid Dynamics: Comparison with Ultrasound Vector Flow Imaging.

This paper investigates the accuracy of blood flow velocities simulated from a geometry prescribed computational fluid dynamics (CFD) pipeline by applying it to a dynamic heart phantom. The CFD flow patterns are compared to a direct flow measurement by ultrasound vector flow imaging (VFI). The hypothesis is that the simulated velocity magnitudes are within one standard deviation of the measured velocities. The CFD pipeline uses computed tomography angiography (CTA) images with 20 volumes per cardiac cycle as geometry input. Fluid domain movement is prescribed from volumetric image registration using the CTA image data. Inlet and outlet conditions are defined by the experimental setup. VFI is systematically measured in parallel planes, and compared to the corresponding planes in the simulated time dependent three dimensional fluid velocity field. The measured VFI and simulated CFD have similar flow patterns when compared qualitatively. A quantitative comparison of the velocity magnitude is also performed at specific regions of interest. These are evaluated at 11 non-overlapping time bins and compared by linear regression giving R2 = 0.809, SD = 0.060 m/s, intercept = -0.039 m/s, and slope = 1.09. Excluding an outlier at the inlet, the correspondence between CFD and VFI improves to: R2 = 0.823, SD = 0.048 m/s, intercept = -0.030 m/s, and slope = 1.01. The direct comparison of flow patterns shows that the proposed CFD pipeline provide realistic flow patterns in a well-controlled experimental setup. The demanded accuracy is obtained close to the inlet and outlet, but not in locations far from these.

Clinical implications of coronary microvascular dysfunction in patients with non-obstructive coronary artery disease and role of the thermodilution method.

More than 60% of patients undergoing coronary angiography present no coronary artery disease (CAD). Angina and myocardial ischemia are classically determined by epicardial vascular obstruction, but coronary microvascular dysfunction (CMD) may also represent a possible cause for these phenomena. Two endotypes of CMD have been recognized, with two different pathophysiological mechanisms: structural CMD, characterized by low coronary flow reserve (CFR) and high microvascular resistance (MVR) values; and functional CMD, characterized by low CFR and normal MVR values. According to the present data, almost half of patients with non-obstructive CAD have shown signs of CMD. For this reason, further investigations for microvascular function assessment should be considered when evaluating no-CAD patients complaining of angina or presenting signs of myocardial ischemia. The thermodilution method is currently becoming a widespread invasive technique due to its feasibility and high reproducibility for coronary physiology evaluation. Furthermore, a recently introduced technique - called continuous thermodilution - allows for direct measurement of absolute coronary flow and resistances. The role of this brand-new technique in the clinical scenario is however still to be fully investigated and its use is at present limited to research purposes only. Among no-CAD patients, both structural and functional CMD are related to a worse prognosis in term of mortality and major adverse cardiovascular events (MACE). In this review, we will discuss the present evidence supporting the definition, prevalence and clinical implication of the different forms of CMD and the technical aspects of its invasive assessment.

In‐Room Direct Nidal Flow Measurement by Digital Subtraction Angiography to Estimate Hemorrhage Risk in Brain Arteriovenous Malformations: A Pilot Study

Background Noninvasive direct flow measurement from digital subtraction angiography (DSA) is challenging in brain arteriovenous malformations (BAVMs). We devised a method to estimate the blood volume flow rate of BAVM nidus using DSA, and assessed its association with angioarchitecture features in hemorrhagic presentation. Methods A total of 24 patients with BAVMs (10 controls and 14 with hemorrhage) who underwent DSA and magnetic resonance (MR) were retrospectively recruited. Fifteen patients underwent additional phase contrast MR imaging. The nidus volume was contoured on the MR time‐of‐flight data set. From DSA, flow velocities and volume flow rate were estimated along calibrated vascular center lines. The BAVM nidus volume flow rate was computed by adding feeding volume flow rate of arteries confirmed on DSA and then normalizing them with nidus volume to yield the nidus flow index. The correspondent phase‐contrast MR‐estimated nidus flow index was evaluated in each BAVM for comparison. Comparisons of hemodynamic parameters of the control and hemorrhage groups were conducted using the Wilcoxon rank sum test. A support vector machine was used for classifying BAVM patients using angioarchitectures and the nidus flow index. Results For the DSA results, the nidus flow index was higher in the hemorrhagic group than in the control group ( P =0.0272). The flow index determined using phase‐contrast MR and nidus volume were not significant. The classification accuracy was higher when the DSA nidus flow index was added into angioarchitecture. Conclusion The BAVM nidus flow index can be directly estimated from DSA and may be associated with hemorrhagic BAVM. Peritherapeutic hemodynamic assessment of BAVMs inside the angio‐suite is feasible.

Wave reflection quantification analysis and personalized flow wave estimation based on the central aortic pressure waveform.

Pulse wave reflections reflect cardiac afterload and perfusion, which yield valid indicators for monitoring cardiovascular status. Accurate quantification of pressure wave reflections requires the measurement of aortic flow wave. However, direct flow measurement involves extra equipment and well-trained operator. In this study, the personalized aortic flow waveform was estimated from the individual central aortic pressure waveform (CAPW) based on pressure-flow relations. The separated forward and backward pressure waves were used to calculate wave reflection indices such as reflection index (RI) and reflection magnitude (RM), as well as the central aortic pulse transit time (PTT). The effectiveness and feasibility of the method were validated by a set of clinical data (13 participants) and the Nektar1D Pulse Wave Database (4,374 subjects). The performance of the proposed personalized flow waveform method was compared with the traditional triangular flow waveform method and the recently proposed lognormal flow waveform method by statistical analyses. Results show that the root mean square error calculated by the personalized flow waveform approach is smaller than that of the typical triangular and lognormal flow methods, and the correlation coefficient with the measured flow waveform is higher. The estimated personalized flow waveform based on the characteristics of the CAPW can estimate wave reflection indices more accurately than the other two methods. The proposed personalized flow waveform method can be potentially used as a convenient alternative for the measurement of aortic flow waveform.

A portable feedback-controlled pump for monitoring eye outflow facility in conscious rats.

Intraocular pressure (IOP) is heavily influenced by the resistance of trabecular outflow pathways through which most of the aqueous humor produced by the eye continuously drains. The standard method of quantifying outflow resistance and other aspects of ocular fluid dynamics is eye cannulation, which allows for direct measurement and manipulation of IOP and flow in animal models. Since the method is invasive, indirect techniques that are slower and less accurate must be used for chronological studies. A novel technology is introduced that can autonomously measure outflow facility in conscious rats multiple times a day. A smart portable micropump infuses fluid into the eye through a permanently-implanted cannula and dynamically adjusts flow rate using a unique proportional feedback algorithm that sets IOP to a target level, even though IOP fluctuates erratically in awake free-moving animals. Pressure-flow data collected by the system from anesthetized rats were validated against intraocular recordings with commercial pressure and flow sensors. System and sensor estimates of outflow facility were indistinguishable, averaging 23 ± 3 nl·min-1·mmHg-1 across animals (n = 11). Pressure-flow data were then collected round-the-clock for several days from conscious rats, while outflow facility was measured every few hours. A significant diurnal facility rhythm was observed in every animal (n = 4), with mean daytime level of 22 ± 10 nl·min-1·mmHg-1 and mean nighttime level of 15 ± 7 nl·min-1·mmHg-1. The rhythm correlated with diurnal changes in IOP and likely contributed prominently to those changes based on the day-night swing in facility magnitude. Hence, the portable smart pump offers a unique tool for repeated long-term monitoring of outflow facility and other possible parameters of ocular health. It could also be useful in animal glaucoma studies for reversibly inducing acute or chronic ocular hypertension without explicitly damaging trabecular outflow pathways.

Validation of a novel numerical model to predict regionalized blood flow in the coronary arteries.

Ischaemic heart disease results from insufficient coronary blood flow. Direct measurement of absolute flow (mL/min) is feasible, but has not entered routine clinical practice in most catheterization laboratories. Interventional cardiologists, therefore, rely on surrogate markers of flow. Recently, we described a computational fluid dynamics (CFD) method for predicting flow that differentiates inlet, side branch, and outlet flows during angiography. In the current study, we evaluate a new method that regionalizes flow along the length of the artery. Three-dimensional coronary anatomy was reconstructed from angiograms from 20 patients with chronic coronary syndrome. All flows were computed using CFD by applying the pressure gradient to the reconstructed geometry. Side branch flow was modelled as a porous wall boundary. Side branch flow magnitude was based on morphometric scaling laws with two models: a homogeneous model with flow loss along the entire arterial length; and a regionalized model with flow proportional to local taper. Flow results were validated against invasive measurements of flow by continuous infusion thermodilution (Coroventis™, Abbott). Both methods quantified flow relative to the invasive measures: homogeneous (r 0.47, P 0.006; zero bias; 95% CI -168 to +168 mL/min); regionalized method (r 0.43, P 0.013; zero bias; 95% CI -175 to +175 mL/min). During angiography and pressure wire assessment, coronary flow can now be regionalized and differentiated at the inlet, outlet, and side branches. The effect of epicardial disease on agreement suggests the model may be best targeted at cases with a stenosis close to side branches.

Atmospheric turbulence and wildland fires: a review

The behaviour of wildland fires and the dispersion of smoke from those fires can be strongly influenced by atmospheric turbulent flow. The science to support that assertion has developed and evolved over the past 100+ years, with contributions from laboratory and field observations, as well as modelling experiments. This paper provides a synthesis of the key laboratory- and field-based observational studies focused on wildland fire and atmospheric turbulence connections that have been conducted from the early 1900s through 2021. Included in the synthesis are reports of anecdotal turbulence observations, direct measurements of ambient and fire-induced turbulent flow in laboratory and wildland environments, and remote sensing measurements of fire-induced turbulent plume dynamics. Although considerable progress has been made in advancing our understanding of the connections between atmospheric turbulence and wildland fire behaviour and smoke dispersion, gaps in that understanding still exist and are discussed to conclude the synthesis.

Hydrodynamics of Meander Bends in Intertidal Mudflats: A Field Study From the Macrotidal Yangkou Coast, China

AbstractMeandering channels are ubiquitous features in intertidal mudflats and play a key role in the eco‐morphosedimentary evolution of such landscapes. However, the hydrodynamics and morphodynamic evolution of these channels are poorly known, and direct flow measurements are virtually nonexistent to date. Here, we present new hydroacoustic data collected synchronously at different sites along a mudflat meander located in the macrotidal Yangkou tidal flat (Jiangsu, China) over an 8‐day period. The studied bend exhibits an overall dominance of flood flows, with velocity surges of about 0.8 m/s occurring immediately below the bankfull stage during both ebb and flood tides. Unlike salt‐marsh channels, velocities attain nearly constant, sustained values as long as tidal flows remain confined within the channel and reduce significantly during overbank stages. In contrast, curvature‐induced cross‐sectional flows are more pronounced during overbank stages. Thus, a phase lag exists between streamwise and cross‐stream velocity maxima, which limits the transfer of secondary flows and likely hinders the formation of curvature‐induced helical flows along the entire meander length. Our results support earlier suggestions that the morphodynamics of intertidal mudflat meanders does not strongly depend on curvature‐induced helical flows and is most likely driven by high velocities and sustains seepage flows at late‐ebb stages, as well as by other tidally‐mediated processes such as waves and intense rainfall events. By unraveling complex flow structures and intertwined morphodynamic processes, our results provide the first step toward a better understanding of intertidal mudflat meanders, with relevant implications for their planform characteristics and dynamic evolution.

Inverse-forward method for heat flow estimation: case study for the Arctic region

The heat flow data are important in many aspects including interpretation of various geophysical observations, solutions of important engineering problems, modelling of the ice dynamics, and related environmental assessment. However, the distribution of the direct measurements is quite heterogeneous over the Earth. Different methods have been developed during past decades to create continuous maps of the geothermal heat flow (GHF). Most of them are based on the principle of similarity of GHF values for the lithosphere with comparable age and tectonic history or inversion of magnetic field data. Probabilistic approach was also used to realize this principle. In this paper, we present a new method for extrapolating the GHF data, based on the inversion of a geophysical data set using optimization problem solution. We use the results of inversion of seismic and magnetic field data into temperature and data from direct heat flow measurements. We use the Arctic as the test area because it includes the lithosphere of different ages, types, and tectonic settings. In result, the knowledge of GHF is important here for various environmental problems. The resulting GHF map obtained well fits to the observed data and clearly reflects the lithospheric domains with different tectonic history and age. The new GHF map constructed in this paper reveals some significant features that were not identified earlier. In particular, these are the increased GHF zones in the Bering Strait, the Chukchi Sea and the residual GHF anomaly in the area of the Mid-Labrador Ridge. The latter was active during the Paleogene.