Varying Flow Conditions Research Articles

Numerical modelling of downstream scour in circular culverts: Impact of inlet blockages and variable flow conditions.

An accurate estimate of scour depth downstream of culvert outlets is essential for culvert design integrity. Inadequate designs can result in structural failures, leading to increased costs for maintenance and rehabilitation. The present research evaluates the efficacy of numerical models in predicting scour depth and its location downstream of circular culverts under variable flow conditions. Two hydrographs were created for unsteady flow, featuring nine different flow discharges, while steady flow conditions were analysed at flow rates of 14 l/s and 22 l/s. The study investigated circular culverts with inlet blockages of 0%, 15%, and 30%, comparing outcomes with predictions from the Flow-3D software using the renormalisation group (RNG) turbulence model. Extensive experimental data on circular culverts were utilised, with simulations performed using commercial software. This involved analysing the scour's downstream profile, its maximum depth, and its location, and comparing these metrics with actual observed data. The results revealed that the numerical model predictions closely corresponded to the experimental data, even though the simulated scour was generally less than that observed for steady and unsteady flows. The results showed that in unsteady flow conditions and for the discharge of 22 l/s, 30% blockage increased scour by 6.8% and 14.2%, respectively, compared to 15% blockage and non-blocked flow. This increase was 22% and 9.5% for the discharge of 14 l/s, respectively. In the steady case, when the flow rate was adjusted from 14 l/s to 22 l/s, there was a noticeable increase in scour depth downstream of the culvert. While blockage rates impacted the scour patterns significantly in unsteady flow scenarios, escalating blockage percentages did not lead to uniformly proportional increases in scour depth within steady flow environments.

Morphological properties of two-dimensional and three-dimensional bedforms in open channel flow: A flume experiments study

Bedforms are formed by sediment particles under the action of flow, which in turn affect flow and sediment movement. However, the fundamental mechanisms behind the formation and development of bedforms under varying flow conditions, the interconnection between sediment particle movement and bed morphology development, as well as the influence of bedforms on flow and sediment transport, are still not well understood. In the current study, the moveable bed load transport flume experiments under different flow conditions were done, and the development processes of two-dimensional and three-dimensional dunes formed under different flow intensities were simulated. The detailed structure of the bedforms was measured by laser scanning technology, the characteristics of the bedforms were analyzed in detail, and the relations between the formation of the bedforms and the movement of sediment particles are discussed. The results found that the correlation coefficients of the longitudinal profile curve can serve as a quick reference for distinguishing two-dimensional and three-dimensional dunes. When the crestline ratio is used as the criterion for two-dimensional and three-dimensional dunes, the relative amplitude of the dune crestline and the included angle with the flow direction should also be comprehensively considered. The lee side angles of dunes calculated using the triangle generalization method and local section tangent method are compared and show that the values obtained by the former method are only about half of that of the latter. It is also found that the lee side angles of dunes are related to the dune height. The superimposed dunes generally exist in the downstream area of the stoss side of the dunes. The local bed slopes on the stoss side of the dunes show reverse slopes. The superimposed dunes improve the local bed height and further increase the reverse slope degree of the stoss side. A streamwise ridge is an important form located in the upstream area of the dunes stoss side, and they are symmetrically distributed on both sides. Multiple streamwise ridges divide the stoss side of the dunes into relatively independent movement areas, restricting the movement of sediment particles to specific regions. According to the distribution characteristics of bed morphologies, the effects of dunes on sediment particle movement and flow energy consumption are analyzed.

Evaluation of the highly sinuous bend sequences using an ecohydraulic model to ascertain the suitability of fish habitats for river ecological conservation

The spatial and temporal patterns of river meanders play a crucial role not only in shaping the hydrogeomorphic properties of channels and floodplains but also in ascertaining the suitability of fish habitats for river ecological conservation. This study evaluates hydrodynamic features and fish habitat quality in six highly sinuous bend sequences along the Black River in China’s Qinghai plateau. The ecohydraulic model system was used to simulate hydrodynamics, habitat suitability, and sediment transport to determine the habitat quality of the highly sinuous bend sequences. The results have successfully identified differences in the suitability of various bends for fish spawning. Bend 1 was found to be the most suitable among all bends, while bends 5 and 6 were deemed unsuitable specifically during higher flood flows. Cases 3 and 4 were discovered to be highly suitable for fish habitat under normal discharge scenarios. Conversely, cases 5 and 6 were the least suitable, with cases 5 and 6 exhibiting the worst habitat quality, with HSI values nearing zero under high discharge. The study concluded that regulated discharge conditions could support fish spawning in these sinuous bends, with lower flood flows promoting habitat suitability and higher flood flows fragmenting habitat quality. The findings highlight the importance of diverse hydrodynamic and geomorphic conditions in creating suitable fish habitats across varying flow conditions, offering insights into the conservation and management of mountain rivers to protect endangered fish species and aquatic organisms.

Double-diffusive convection in flow of Carreau fluid with variable density inside converging and diverging channels of rectilinear walls

In this article, the effects of double-diffusive convection have been seen on the flow of Carreau fluid of variable density, maintained inside straight and converging (diverging) channels. Note that the channel walls exhibit variable porosity and undergo stretching or shrinking at non-uniform velocities. In the flow domain, we have taken into account the convective transport of both heat and species mass concentrations. The pseudo-similarity solutions of previous investigation for such type flows are not used here; however, a new set of similarity transformations has been formed, which reduced the governing system (PDEs) into an exact set of ordinary differential equations (ODEs), whereas the longstanding issues of semi-similarity solutions have been successfully resolved in this particular case and in general for all situations of Carreau fluid flow. In a nutshell, a unified mathematical approach has been devised in this paper. We strictly emphasized the simulation of flow of Carreau fluid and double diffusive convection in flow inside a channel with multiple dynamical behaviours and structures (both Jeffery Hammel and Poissuielle flow types) of walls. The boundary layer approximation and stream function assumptions have not been used in the study's execution. The shear thinning and shear thickening features of Carreau fluids with variable density cause them to exhibit lower axial velocity in the centre of a horizontal channel than Newtonian fluids due to variable wall configurations and complex flow conditions. By enhancing buoyancy driven convection, which promotes effective heat dispersion, increasing the solutal and thermal Grashof numbers (GrS=GrT>0) lowers the temperature field. It has been found that in channel with diverging walls (a1=2.0), increasing the modified Reynolds numbers (σ1,σ2>0) increases concentration profiles, i.e. ϕ(η), while decreasing them in channel with rectilinear walls (a1=0.0).

Optimizing Aerofoil Design: A Comprehensive Analysis of Aerodynamic Efficiency through CFD Simulations and Wind Tunnel Experiments

This study explores the aerodynamic properties of different aerofoil shapes and their performance under varying flow conditions to identify the most efficient design based on lift-to-drag ratio, stall behaviour, and overall aerodynamic efficiency. Using Computational Fluid Dynamics (CFD) simulations, several aerofoil profiles were analysed at different angles of attack and flow speeds. These simulations were validated through wind tunnel experiments, offering a comprehensive understanding of aerofoil performance in real-world scenarios. The combination of CFD analysis and wind tunnel testing enabled a thorough assessment of each aerofoil shape, leading to the discovery of a specific aerofoil with a high lift-to-drag ratio and stable performance at high angles of attack. These results have significant implications for the design of wings and blades in aerospace and aeronautical applications, improving fuel efficiency and performance in both aviation and wind energy sectors. Additionally, dynamic roughness shows potential in reducing separation bubbles, but further investigation is needed to assess its effectiveness at higher angles of attack and elevated Reynolds numbers. Understanding the scalability and practical application of dynamic roughness in real-world scenarios is essential. Current research on surface modifications like dimples and riblets lacks optimized configurations for varying conditions. More research is needed to understand the interaction between surface geometries and the boundary layer, particularly at higher angles of attack and Reynolds numbers. Combining experimental and numerical methods can provide a comprehensive understanding of flow control techniques. The limited research on applying flow control strategies to wind turbine blades indicates a significant opportunity to improve wind energy efficiency. Future studies should focus on optimizing multiple techniques and addressing practical challenges, such as durability, cost-effectiveness, and integration into existing systems. Investigating the cost-effectiveness and durability of these modifications for long-term use will be vital for their successful adoption in the industry. Expanding research to include the effects of environmental factors like temperature and humidity will offer a more complete understanding of flow control in various operating conditions. By addressing these gaps, advancements in aerodynamic performance can be achieved, benefiting the aerospace and wind energy sectors.

Flow Performance Analysis of Non-Return Multi-Door Reflux Valve: Experimental Case Study

Non-return multi-door reflux valves are essential in fluid control systems to prevent reverse flow and maintain system integrity. This study experimentally analyzes the flow performance of multi-door check valves under different operating conditions, focusing on pressure testing and evaluating their effectiveness in preventing backflow. A wide-ranging experimental setup was designed and implemented to simulate real-world scenarios, facilitating accurate measurement of flow rates, pressure differences, and valve response times. The collected experimental data were analyzed to evaluate the valve’s performance in terms of flow capacity, pressure drop, and hydraulic efficiency. Additionally, the effects of factors such as valve size, valve configuration, and fluid properties (water) on performance were considered. It was found that the non-return multi-door reflux valve has been proven effective and reliable in preserving system integrity and maintaining unidirectional flow at the same time during pressure testing. It exhibits no backflow, remains stable and constant across varied flow conditions, and demonstrates a low pressure drop and high flow capacity, making it suitable for critical pressure testing applications. The response curve revealed that valve opening takes longer to reach higher flow rates than closing, indicating pressure instability during transition periods. This non-linear relationship indicates possible irregularities in pressure drop response to flow rate changes, highlighting potential areas for further investigation.

Spatio-temporal trends in microplastic presence in the sediments of the River Thames catchment (UK)

This study investigated the spatio-temporal variability of microplastics (MPs) in the sediments of the River Thames (UK) catchment over 30 months (July 2019 – Dec 2021). The average MP concentration was 61 items kg−1 d.w., with fragments <1 mm being dominant and polyethylene (PE) the most common polymer. Adjacent land use influenced MP concentrations and types, with industrial sites showing particularly high levels and a prevalence of small beads and industrial polymers. MP concentrations generally decreased after higher winter flows, likely due to sediment rearrangement or winnowing. This study describes the seasonal concentrations and characteristics of MPs present in sediment from the River Thames catchment, and attempts to identify their likely origin. Further, the study provides new insights into the mobility and fate of MPs in riverine settings under varying flow conditions, which is vital given the predicted increases in flooding under various global heating scenarios.

Application of an energy recovery device with RO membrane for wave powered desalination

A Wave-Driven Desalination System (WDDS) represents an efficient method for harnessing wave energy to facilitate water desalination. Nonetheless, various challenges impede its path to commercial viability. There is a requirement to connect the WDDS to an Energy Recovery Device (ERD), but this is challenging due to the inherent variations in pressure and flow. This unique study demonstrates the working of a small scale WDDS system using a Spiral Wound Reverse Osmosis (SWRO) membrane with a permeate capacity of ∼2 m3/day. The study demonstrates the possibilities to reduce high specific energy consumption (SEC) in WDDS by incorporating a Clark pump as an ERD. The study is the first time an evaluation of an SWRO membrane and Clark pump in-the-loop has been evaluated using variable feed flow and pressure. The utilization of the Clark pump notably reduces SEC to about 3.5 kWh/m3, which is comparable to that of commercial desalination plants. Furthermore, the Clark pump aids in maintaining a consistent permeate recovery rate of 10 % under rectified sinusoidally varying flow conditions – representing the operating conditions more closely to that of practical devices.

Energy Conversion by Helical Hydrokinetic Turbine in A Pipe

Hydrokinetic turbines are mechanisms designed for the purpose of utilizing the kinetic energy present in the movement of water bodies like rivers, tidal currents, or ocean currents, and transforming it into electrical power. These turbines function based on a principle akin to that of wind turbines; however, they are positioned underwater to harness the energy of the water flow. This study focuses on the fundamentals of hydrokinetic turbines and presents existing research. Additionally, simulations have been conducted to observe how the hydrokinetic turbine responds hydrodynamically inside a pipe. A three-bladed vertical-axis helical hydrokinetic turbine was installed within a circular conduit and subjected to analysis under varying flow conditions. The k-ω SST turbulence model was employed in the analyses. The results indicated that increasing the turbine's angular velocity initially raises the torque and the power coefficient until a peak is reached, after which the power coefficient decreases. The highest power coefficient was observed at a flow velocity of 2 m/s. Additionally, consistent with previous studies, the hydrokinetic turbine within the pipe surpassed the Betz limit.

Impact of non-axisymmetric tip clearance on the aerodynamic and aeroelastic stabilities of a transonic compressor

The aerodynamic and flutter effects caused by the circumferential non-uniform tip clearances from the non-axisymmetric casing geometry, which are more representative of real operational conditions, should receive more attention. In this paper, sensitivity analyses on clearance and non-uniformity regarding rotor performance are conducted. The isentropic efficiency, total pressure ratio and stability margin of the rotor are reduced by 1.96%, 1.06% and 6.76% for an increase of tip clearance by 1% tip chord, respectively. The non-axisymmetric configuration reconfigures the interaction between leakage flow and mainstream in each rotor passage and alters the strength and influence range of the low-speed separation region generated by shock wave. The phase lag phenomenon observed in the aerodynamics of the non-axisymmetric layout also manifests in the aeroelastic effects but requires a larger phase shift at the maximum clearance sector, owing to the longer timescales for flow adjustment relative to the local tip gap considering the flow-induced vibration. Clearance sensitivity on flutter stability varies with the direction of the traveling wave: under forward traveling conditions, damping values initially decrease and then increase with increasing rotor tip clearance; while under backward traveling condition, blade damping linearly decreases with increasing rotor tip clearance. Additionally, variations in flow conditions and nodal diameters affect flutter stability by altering the position of shock waves and their work on the suction surface of the rotors. The mechanism responsible for unsteady flows induced by non-axisymmetric clearances from the casing ovalization on flutter stability is discussed for the first time in this paper, which can guide the industry to evaluate its impact.

Abstract Mo089: Fontan-Associated Liver Disease On A Chip

Introduction: The Fontan procedure is performed in children with single ventricle physiology, and has led to excellent short-term palliation and survival rates but at the cost of long-term complications. Fontan-associated liver disease (FALD) results from hemodynamic changes following the Fontan procedure, leading to elevated central venous pressures, chronic alterations in hepatic perfusion, and resultant hepatic fibrosis. Improved understanding of FALD pathophysiology, which may provide insights for prevention and treatment is challenged by the lack of experimental models. Current in vitro liver models, mostly 2D or suspension hepatic cell cultures, lack biomimicry. This study presents a 3D bioprinted perfusable human liver model for in vitro study of hepatic fibrosis in response to altered flow conditions in FALD patients. Methods: Vascular 3D model of hepatic sinusoid was biofabricated using hybrid bioinks in two distinct peripheral layers and a central lumen. The outer layer was cast with hepatic (HepG2) cells encapsulated in a mixture of gelatin methacrylate (GelMA) and collagen type I. The inner layer consisted of hepatic stellate cells (HSCs) in GelMA. Human endothelial cells (ECs) were seeded onto the central lumen. 3D cellular constructs were cultured in vitro for three weeks in static or dynamic conditions, by circulating the culture media at varying flow conditions to simulate sinusoid pressure characteristic of healthy vs. disease state. Using Volcano system in cath lab, we invasively measured the pressure in mid-channel. Cell viability, proliferation, maturation into functional liver tissue, and tissue stiffness were evaluated via microindentation, flow hemodynamics assays, metabolomic assays, and immunohistochemistry analyses. Results: Bioengineered liver constructs cultured under static and dynamic conditions demonstrated high cell viability and growth and full endothelialization of the sinusoid channel. HepG2 cells exhibited long-term function and maturation, forming clusters. Under FALD flow conditions, there were notable changes in EC-HepG2 cell morphology compared to dynamic flow in the healthy range, accompanied by reduced levels of functional markers. Conclusion: This proof-of-principle study introduces an innovative and highly biomimetic 3D model of hepatic sinusoid, which can serve as a robust platform for in vitro investigations of complex cell-microenvironment interactions in the context of FALD as well as other hepatic disorders.

Integrated positron emission particle tracking (PEPT) and X-ray computed tomography (CT) imaging of flow phenomena in twisted tape swirl flow

A combined positron emission particle tracking (PEPT) and X-ray computed tomography (CT) technique is presented, and its utility is demonstrated through investigation of flow in a pipe with twisted tape swirl insert with varying flow conditions (diameter-based Reynolds numbers 16,300–63,300). A description of this technique is given, as well as data handling practices used to relate geometric information captured by CT to fluid flow data gathered via PEPT. It is found that the CT component is readily capable of capturing the stainless steel insert geometry in this present system, but the use of combined plastic and metal materials leads to artifacts in imaging of the plastic surface. Nonetheless, CT data are related to PEPT flow measurements, and average velocity fields are calculated via a pseudo-framing and interpolation scheme and used to visualize and interrogate key flow phenomena within the system. Radial velocity profiles of the mean flow characteristics are seen to collapse to a nearly common form across all flow conditions considered. Helical vortices are seen propagating through the flow field, generated by bypass flow around the gap between the insert and pipe wall, with additional coherent secondary flow structures seen in the higher Reynolds number cases. These findings enhance the understanding of the mixing mechanisms in these swirl flows and encourage the continued development of PEPT-CT methodologies for 3D flow measurements in optically inaccessible systems.

Identifying manning roughness coefficient using automatic calibration method and simulation of pollution incidents in the Nile River, Egypt

Study regionA reach of the Nile River located between Naga Hammadi barrage and Asyut barrage, Egypt Study focusAn accurate representation of hydrodynamics of an important water source helps cope with expected future climate changes, pollution incidents and water quality problems. Here, a comparison between HEC-RAS 1D and TELEMAC-2D model was conducted by identifying different Manning coefficients. Moreover, an automatic calibration using Dual-Annealing optimization method was applied for first time to calibrate the model with non-uniform Manning coefficients. The transport of tracer (pollution) was simulated by computing tracer residence times. Pollution transport scenarios were discussed to draw a picture of pollution incidents which will continue to happen in the future. An equation indicating the relation between flow discharge and residence time was derived to hurriedly help decision makers in water management during sudden pollution incidents. New hydrological insights for the regionA model with spatially variable Manning coefficients using TELEMAC-2D was set up and calibrated achieving good accuracyies with average errors of approximately 4 cm and 7 cm between field and simulated water levels for two different discharge scenarios. Moreover, an equation for relation between flow discharge and residence time was derived producing a strong correlation coefficient of 0.95. This study, integrating advanced hydrodynamic models and automatic calibration techniques, provides a robust framework for assessing and managing water resource challenges under varying flow conditions.

Adaptive management of borehole heat exchanger fields under transient groundwater flow conditions

Uncontrolled heat extraction by multiple interacting borehole heat exchangers (BHEs) in high-density energy-use districts can lead to undesirable thermal conditions in the subsurface which can affect both system performance and regulatory compliance. The difficulty in controlling heat extraction arises in particular from predictive uncertainties, such as when forecasting trends in energy demand or groundwater flow. In this study, a combined simulation-calibration-optimization framework is introduced to consider BHE fields with the presence of a transient groundwater flow regime. In the first part, a semi-analytical modeling technique is proposed based on temporal superpositioning of variable flow conditions. Two synthetic case studies verify its accuracy under different groundwater fluctuation patterns. The mean absolute error of the proposed model in comparison to numerical calculation does not exceed 0.18 K over ten years of operation. In the second part, the model is augmented by a parameter estimation algorithm that is employed for continuous model updating. The benefit of resolving transient flow conditions is demonstrated by using this approach for monthly optimization of individual BHE heat extraction. The result of dynamic optimization compared to a synthetic case without calibration shows a 10 % lower imposed temperature change in the subsurface.

Deflection and control of the mixing region in membraneless vanadium micro redox flow batteries: Modeling and experimental validation

Membraneless micro redox flow batteries operate within the laminar flow regime to mitigate the convective mixing between catholyte and anolyte. The absence of an ion-exchange membrane reduces manufacturing costs and overall cell resistance, thereby enhancing battery performance. However, it also poses a new challenge: the precise control of the thin mixing layer established between the two co-flowing electrolytes. Undesired displacements of the mixing region lead to increased crossover losses and significant liquid transfer between tanks. This work addresses the deflection of the mixing region under varying flow conditions, considering electrolyte viscosity variations due to the changes in the local state of charge arising during battery operation. This is achieved through a combination of mathematical analysis, numerical simulations, and experimental results. The conservation equations and non-dimensional parameters governing the problem are first written and discussed. The model is then integrated numerically incorporating different inlet and outlet boundary conditions to simulate the effect of various flow control strategies. Next, the numerical results are validated against experimental realizations of the flow. Finally, three case studies are presented and discussed. This work highlights the relevance of variable viscosity in the operation of co-laminar membraneless micro redox flow batteries, and proposes for the first time feasible control methods to mitigate undesired disturbances in the hydraulic circuit, thereby minimizing crossover losses.

A dynamic compartmental model of a sequencing batch reactor (SBR) for biological phosphorus removal

ABSTRACT Bioreactors are usually modelled as continuous stirred tank reactors (CSTRs) or CSTRs connected in series (Tanks-In-Series configuration). In large systems with non-ideal mixing, such approaches do not sufficiently capture the complex hydrodynamics, leading to model inaccuracies due to the lumping of spatial gradients. Highly detailed computational fluid dynamics (CFD) models provide insight into complex hydrodynamics but are computationally too expensive for flow-sheet models and digital twin applications. A compartmental model (CM) can be a middle-ground by providing a more realistic representation of the hydrodynamics and still being computationally affordable. However, the hydrodynamics of a plant can be very different under varying flow conditions. Dynamic CMs can capture these changes in an elegant way. So far, the application of CMs has been limited mostly to continuous flow systems. In this study, a dynamic CM of a sequencing batch reactor (SBR) is developed for a bio-P removal process. The SBR comes with challenges for CM development due to its distinct operational stages. The dynamic CM shows significant improvements over the CSTR model (using the same biokinetic parameters) for dissolved oxygen and phosphate predictions reducing the need for model recalibration that can lead to over-fitting and limited extrapolation capability of the model.

An experimental study of fluid–structure interaction and self-excited oscillation in thin-walled collapsible tube

Flow through thin-walled collapsible tubes often exhibits a complex nonlinear interplay between fluid dynamics and structural mechanics. This paper presents findings from an experimental investigation employing quantitative analyses of structural deformation and flow fields through image analysis and particle image velocimetry (PIV) measurements. The results suggest that as Reynolds number (Re) increases, the tube experiences buckling and collapses under greater negative transmural pressures (Ptm) compared with no flow condition, indicating that increasing flow inertia delays the onset of collapse. The onset of self-excited oscillation is marked by a Re threshold. Beyond this threshold, self-excited oscillations occur within a specific range of Ptm. Small-amplitude, chaotic oscillations emerge at relatively low Re or when Ptm approaches the upper limit of the oscillation-inducing regime. Conversely, large-amplitude, periodic oscillations arise as Re increases and Ptm decreases. The frequency of oscillation escalates with increasing Re and decreasing Ptm, while amplitude peaks near the midpoint of the oscillation-inducing Ptm range. PIV results indicate that large-amplitude, periodic oscillations correlate with asymmetric jet flows that switch directions from cycle to cycle. Furthermore, self-excited oscillations reduce overall flow resistance, thereby mitigating flow limitations under highly negative Ptm. These findings contribute to a deeper understanding of collapsible tube dynamics under varying flow conditions, with implications for diverse fields ranging from biomedical engineering to space physiology.

Exploring thermal buoyant flow in urban street canyons: Influence of approaching turbulent boundary layer

Turbulent boundary layer inflow is a critical factor in urban climate research, shaping canyon flow dynamics, air ventilation patterns, and heat flux distribution. In numerical simulation studies, it serves as a fundamental inflow boundary condition, profoundly influencing overall results. In this study, simultaneous Particle Image Velocimetry and Laser-Induced Fluorescence (PIV-LIF) measurements are utilized within a large closed-circuit water tunnel. This approach allows comprehensive flow data to be gathered under varied flow and thermal conditions, encompassing a spectrum of Richardson numbers ranging from 0.01 to 1.34. The investigation aims to elucidate the effects of turbulent boundary layer flows on heat transfer mechanisms and flow behaviours within a two-dimensional street canyon model with a unit aspect ratio. The analysis reveals distinct heat and fluid flow characteristics, highlighting the interplay between thermal conditions and flow dynamics. The three chosen turbulent boundary layer flows demonstrate unique influences on flow characteristics and heat removal capacity. Significant variations in ventilation rates are observed, with a maximum difference of 80% among the tested boundary layer flows. Additionally, the most pronounced variation in heat removal capacity is approximately 45%. Thicker boundary layers with lower velocities near the canyon exhibit reduced ventilation and heat removal capabilities. Furthermore, the investigation reveals that varied turbulence inlet profiles result in diverse fluctuating features at the canyon roof level, with a comparatively lesser impact on the deeper regions of the canyon.

Investigating the utility of satellite-based precipitation products for simulating extreme discharge events: an exhaustive model-driven approach for a tropical river basin in India.

Satellite-based precipitation estimates are a critical source of information for understanding and predicting hydrological processes at regional or global scales. Given the potential variability in the accuracy and reliability of these estimates, comprehensive performance assessments are essential before their application in specific hydrological contexts. In this study, six satellite-based precipitation products (SPPs), namely, CHIRPS, CMORPH, GSMaP, IMERG, MSWEP, and PERSIANN, were evaluated for their utility in hydrological modeling, specifically in simulating streamflow using the Variable Infiltration Capacity (VIC) model. The performance of the VIC model under varying flow conditions and timescales was assessed using statistical indicators, viz., R2, KGE, PBias, RMSE, and RSR. The findings of the study demonstrate the effectiveness of VIC model in simulating hydrological components and its applicability in evaluating the accuracy and reliability of SPPs. The SPPs were shown to be valuable for streamflow simulation at monthly and daily timescales, as confirmed by various performance measures. Moreover, the performance of SPPs for simulating extreme flow events (streamflow above 75%, 90%, and 95%) using the VIC model was assessed and a significant decrease in the performance was observed for high-flow events. Comparative analysis revealed the superiority of IMERG and CMORPH for streamflow simulation at daily timescale and high-flow conditions. In contrast, the performances of CHIRPS and PERSIANN were found to be poor. This study highlights the importance of thoroughly assessing the SPPs in modeling diverse flow conditions.

High-Speed Generation of Microbubbles with Constant Cumulative Production in a Glass Capillary Microfluidic Bubble Generator.

This work reports a simple bubble generator for the high-speed generation of microbubbles with constant cumulative production. To achieve this, a gas-liquid co-flowing microfluidic device with a tiny capillary orifice as small as 5 μm is fabricated to produce monodisperse microbubbles. The diameter of the microbubbles can be adjusted precisely by tuning the input gas pressure and flow rate of the continuous liquid phase. The co-flowing structure ensures the uniformity of the generated microbubbles, and the surfactant in the liquid phase prevents coalescence of the collected microbubbles. The diameter coefficient of variation (CV) of the generated microbubbles can reach a minimum of 1.3%. Additionally, the relationship between microbubble diameter and the gas channel orifice is studied using the low Capillary number (Ca) and Weber number (We) of the liquid phase. Moreover, by maintaining a consistent gas input pressure, the CV of the cumulative microbubble volume can reach 3.6% regardless of the flow rate of the liquid phase. This method not only facilitates the generation of microbubbles with morphologic stability under variable flow conditions, but also ensures that the cumulative microbubble production over a certain period of time remains constant, which is important for the volume-dominated application of chromatographic analysis and the component analysis of natural gas.