Non-uniform Flow Pattern Research Articles

Real-time Bayesian inversion in resin transfer moulding using neural surrogates

In Resin Transfer Moulding (RTM), local variations in reinforcement properties (porosity and permeability) and the formation of gaps along the reinforcement edges result in non-uniform resin flow patterns, which may cause defects in the produced composite component. The ensemble Kalman inversion (EKI) algorithm has previously been used to invert in-process data to estimate local reinforcement properties. However, implementation of this algorithm in some applications is limited by the requirement to run thousands of computationally expensive resin flow simulations. In this study, a machine learning approach is used to train a surrogate model which can emulate resin flow simulations near-instantaneously. A partition of the flow domain into a low-dimensional representation enables an artificial neural network (ANN) surrogate to make accurate predictions, with a simple architecture. When the ANN is integrated within the EKI algorithm, estimates for local reinforcement permeability and porosity can be achieved in real time, as was verified by virtual and lab experiments. Since EKI utilises the Bayesian framework, estimates are given within confidence intervals and statements can be made on-line regarding the probability of defects within sections of the reinforcement. The proposed framework has shown good predictive capabilities for the set of laboratory experiments and estimates for reinforcement properties were always computed within 1 s.

Experimental and numerical investigation of the gap flow between a pusher and a barge in deep and shallow water

The flow in the gap between a pusher boat and a barge of a conventional inland waterway convoy was experimentally and numerically investigated to gain insight into the complex flow pattern and to provide benchmark data for validation of an adequate turbulence model. Two water depths were considered, corresponding to deep water and moderately shallow water conditions. Both cases highlighted the extremely unsteady non-uniform flow pattern in the gap. The collected data were subsequently used to assess a numerical method based on solving the Reynolds-averaged Navier–Stokes (RANS) equations and the Improved Delayed Detached Eddy Simulation (IDDES) technique. Generally, our numerical predictions compared favorably to the experimental data; however, the IDDES method proved to be more accurate, especially in the prediction of the velocity field in the gap region. The IDDES technique was then used to analyze the flow in water depth to draft ratios h/T of 2.14, 1.5, and 1.2. At h/T=1.2, comparatively larger recirculation zones and a massive increase in resistance were observed. Additionally, to quantify the influence of the gap between pusher and barge on resistance in shallow waters, we modified our model by simply covering the gap and then analyzing this modified model by carrying out an additional simulation at h/T=1.2. Covering the gap reduced the overall longitudinal hydrodynamic force acting on the convoy by about 6.5 %.

Improving the Yearly Profit of Wind Farm with Artificial Intelligence Technique

Owing to the escalating environmental and social problems linked to climate change and the hastily depleting stock of hydrocarbon-based fuels, renewable power generation modes have attained massive prominence. Wind power is an important renewable energy generation technology that contributed to 5% of the planet’s power generation in 2020. However, for sustaining the Paris Agreement targets, the global wind power generation sector necessitates evolving at a fleeter pace. To expand the green switch of the worldwide power generation businesses, wind farms are expected to remain financially more advantageous than fossil fuel-based power plants. The present work focused on elevating the annual profit of wind farms by employing an amended genetic algorithm (GA). A fresh approach to dynamically apportioning the crossover and mutation prospects for a GA-enabled profit growth algorithm was suggested to amplify the capability of the GA. Three dissimilar terrain conditions with diverse obstruction configurations and a randomly generated non-uniform wind flow pattern were used for assessing the competence of the proposed algorithm for profit maximization. The results showed that the annual yields for Terrain Layouts 1, 2 and 3 obtained by the amended GA were higher by 10.34, 5.09 and 0.51%, respectively, than the typical one, which substantiated the superior proficiency of the former.

Demonstration of a Three-Dimensional Current Mapping Technique Around a Superconductor in a Prototype of a Conventional Superconducting Fault Current Limiter

Here, we describe a three-dimensional (3-D) current mapping technology developed for a superconductor using an array of Hall sensors distributed around it. We demonstrate this in a prototype similar to a conventional resistive superconducting fault current limiter (SCFCL). By calibrating the Hall sensor voltage, we can directly measure the distribution of the currents in the superconductor and the shunt. Using pulsed measurements, we measure the fractions of current distributed between the superconductor and shunt resistor parallel combination when a fault-like condition is mimicked in the system. Using the Hall array measurements, we generate a real-time 3-D map of local average current distribution around the superconductor used in our prototype of SCFCL. Our measurements show that even for currents less than the critical current a nonuniform current flow pattern exists around the superconductor, which we have used in the prototype. The capability of real-time, 3-D monitoring of the average local current distribution offers a way for the early detection of instabilities like hotspots developing in a superconductor. We discuss the use of this technique to not only show how it offers early detection and protection against instabilities developing in the superconductor, but also how it offers an added flexibility, namely, a user-settable fault current threshold.

Nickel removal by biogenic selenium nanoparticles (SeNPs): Characterization and simulation of non-symmetric breakthrough curves in continuous-flow packed-bed columns

Nanoparticles offer an alternative mean for heavy metals removal from aquatic environment. In this work we study the sequestering of nickel by biogenic selenium nanoparticles (SeNPs) both in native and in immobilized form in alginate matrix (alginate-SeNPs). The apparent sorption like process is attributed to the coordination chemistry of Ni with the functional groups of the extracellular polymeric substances (EPS) covering the SeNPs. The kinetics and the equilibrium of the process are presented, while the morphology and the properties of the adsorption beads are studied by SEM, FTIR and rheological analysis. Langmuir isotherm describes the adsorption equilibrium with maximum loading Q0 29.411 mg Ni/g SeNPs and 0.651 mg Ni/g alginate-SeNPs. The adsorption of nickel is fast and equilibrium is attained within one hour. Continuous flow experiments in packed beds reveal early elution patterns and non-symmetric sigmoidal profiles due to the reduced adsorption capacity of the immobilized SeNPs, the short depth of the beds and the apparent non-uniform flow pattern. The Bohart-Adams equation fits adequately the main sigmoidal part of the breakthrough curves, however fails to predict the early breakthrough data. By using the advection–dispersion-reaction equation (ADR) under two novel aspects: (a) the rapid equilibrium model with the introduction of an efficiency coefficient accounting for all the kinetic and sorption limitations and (b) the split flow model accounting for any non-uniform flow conditions in the column, the model accuracy is significantly improved. Repeated sorption–desorption experiments show that alginate-SeNPs retain 59% of the original adsorption capacity even after eight cycles.

Effect of impeller inlet diameter on saddle-shaped positive slope and non-uniform flow patterns at low flow rates of a mixed-flow pump

Most mixed-flow pumps obtain a saddle-like Q-P curve with a backflow, owing to the increased incidence angle at low flow rates. The backflow was developed near the shroud and followed downstream again at its end to form a recirculating flow. The rotating stall, which could be a part of the recirculating flow, followed the impeller’s rotational direction, and its properties affected the local stability. The reattaching flow became strong when the upstream flow from the blade leading edge deviated from the same circumferential degree as the dominant flow of the rotating stall heading downstream. The fluctuation in the total pressure rise decreased when the average incidence angle was smaller than that of the design flow rate. As a passive control to suppress the saddle and the above flow patterns, the impeller inlet diameter was reduced from the shroud, and the inlet blade angle was further adjusted to maintain the incidence angle. From the reduced inlet diameter, the backflow was mostly suppressed, and the saddle was improved with a wider operating range. Here, the performance near the design flow rate was almost maintained. The stability was evaluated using the fast Fourier transform, and the numerical method was validated through experimental tests.

Impact of ablation cell design in LA-ICP-MS quantification

The correlation between non-uniform gas flow patterns in large ablation cells and the resulting elemental fractionation is investigated and compared to two-volume ablation cells.

3D visualization of tectonic coal microstructure and quantitative characterization on topological connectivity of pore-fracture networks by Micro-CT

Research on the connectivity characteristics and topological relationships of pore-fracture networks is crucially significant for systematic understanding the microstructure evolution on original and tectonic coals. From the aspects of digitization, visualization, non-destruction, topologization and quantitation, Micro-CT is adopted to characterize the microstructure of original, tectonic and reconstructed coals. The results indicate that the roughly vertical distribution among cleat system in original coal microstructure regularly splits coal matrix into several cubic blocks. Tectonism induces the fundamental transformation on microstructure, associated with well-developed micro-fractures and sporadic pores distributed in spatial scale. With external stress loading, the internal micro-fractures of reconstructed coal sharply decline and gradually evolves into widely-distributed pore connectivity with locally disorderly and dispersed micro-fractures. Following morphological thinning algorithm, skeletonization models were created to demonstrate that the mean tortuosity of original coal has the highest value of 1.2213, followed by reconstructed and tectonic coals of 1.1741 and 1.1205, respectively. Based on skeletonization, the topological “ball-rod” model and its quantitative connectivity parameters reveal that the equivalent structure of pore space for tectonic coal significantly increases, compared to original coal; however, the reconstructed coal after stress loading decreases slightly to 37.75%. Tectonism may facilitate coal microstructure to generate a high coordination number >10, enhancing the connectivity of tectonic coal; nevertheless, the coordination number of reconstructed coal dropped dramatically due to stress loading. Based on the mentioned above, the pore-scale flow simulation of micro-topological equivalent PNMs was conducted for discovering that pressure distributions of tectonic coal in different directions are more concentrated and uniform than original coal while the latter has a non-uniform flow pattern due to its structural anisotropy and heterogeneity. The aforementioned results have guiding significance for revealing the micro-topological connectivity of pore-fracture network in coal, as well as the pore-scale fluid transporting visualization. • 3D visualization models of coal microstructure were non-destructively established. • 3D skeletonization and PNM were created based on morphological simplification. • Pore-scale flow simulation was conducted by micro-topological equivalent PNMs.

Quantifying the Importance of Preferential Flow in a Riparian Buffer

HighlightsRiparian buffers and vegetative filter strips are uniquely susceptible to preferential flow.An innovative method is proposed to partition infiltration into matrix and macropore domains.Riparian buffer matrix and plot-scale infiltration experiments were simulated with HYDRUS-1D and VFSMOD.Preferential flow accounted for 32% to 47% of infiltration depending on hydrologic conditions.Preferential flow mechanisms should be incorporated into riparian buffer design tools and models.Abstract. Riparian buffers are uniquely susceptible to preferential flow due to the abundance of root channels, biological activity, and frequent wetting and drying cycles. Previous research has indicated such susceptibility and even measured the connectivity of preferential flow pathways with adjacent streams and rivers. However, limited research has attempted to partition the riparian buffer infiltration between matrix and preferential flow domains. The objectives of this research were to develop an innovative method to quantify soil matrix infiltration at the plot scale, develop a method to partition infiltration into matrix and macropore infiltration at the plot scale, and then use these methods to quantify the significance of macropore infiltration at a riparian buffer site. This research further demonstrated the importance of considering preferential flow processes in design tools and models to evaluate riparian buffer effectiveness. Sprinkler and runon field experiments were conducted at an established riparian buffer site with sandy loam soil. Trenches were installed and instrumented with soil moisture sensors along the width of the riparian buffer (i.e., along the flow path toward the stream) for detecting non-uniform flow patterns due to preferential flow. Riparian buffer parameters, including soil hydraulic parameters, were estimated using HYDRUS-1D for the sprinkler experiments and VFSMOD for the runon experiments. This research partitioned the infiltration into matrix and preferential flow domains by assuming negligible exchange of water between the soil matrix and preferential flow pathways in comparison to the magnitude of soil matrix flow. For these experimental conditions with 0.20 to 0.48 L s-1 of runon and initial soil water contents of 0.29 to 0.32 cm3 cm-3, preferential flow accounted for at least 27% to 32% of the total runon water entering the riparian buffer. This corresponded to approximately 32% to 47% of the total infiltration. While increasing the riparian buffer plot soil hydraulic conductivity in single-porosity models can adequately predict the total infiltration and therefore the surface outflow from the buffer, design tools and models should specifically consider preferential flow processes to improve predictive power regarding the actual infiltration processes and correspondingly the non-equilibrium flow and solute transport mechanisms. Keywords: Flow partitioning, HYDRUS, Matrix flow, Preferential flow, Riparian buffer, VFSMOD.

Structure and arrangement of perforated plates for uniform flow distribution in an electrostatic precipitator

ABSTRACT A wide-angle diffuser installed at the entrance of an electrostatic precipitator (ESP) causes a non-uniform flow distribution due to the boundary layer separation. Because a non-uniform flow pattern decreases the particulate matter control efficiency of an ESP, it is important to maintain a uniform flow distribution. The objective of this study is therefore to understand flow distribution with the conditions of perforated plates placed in the diffuser and then to design an ESP to obtain uniform flow. Discharge coefficients were determined varying the porosity, thickness, and number of holes of the perforated plate inside the lab-scale duct system. The test results suggest that the perforated plate with a porosity of 50%, a thickness of 5 mm, and 0.104 hole/m2 perforated plate is most acceptable. This perforated plate was placed in the diffuser of the lab-scale ESP system. Velocity profiles in the body of the ESP were obtained depending on the number and arrangement of perforated plates in the diffuser. One perforated plate placed in the diffuser did not improve the flow distribution. Although more uniform flow distribution was found with two perforated plates, stalled flow regions still existed at the top and bottom of the ESP body. When three perforated plates were placed in the diffuser, the 2nd and 3rd perforated plates were important to obtain uniform flow distribution. When the 2nd and 3rd perforated plates were placed at the inlet side and outlet of the diffuser, respectively, the most uniform flow distribution was obtained in the body of the ESP. Implications: In order to determine the optimal perforated plate for Electrostatic Precipitator (ESP), we investigated the discharge coefficient depending on the structure of the perforated plate in a square duct. We measured the velocity distribution in a laboratory ESP with perforated plates and found the effect of the number and arrangement of perforated plates on the flow distribution in the collection region. Based on the test results, we found the configuration of perforated plates for uniform flow distribution in the body of the ESP.

Laboratory study on fish behavioral response to meandering flow and riffle-pool sequence driven by deflectors in straight concrete flood channels

Sectional channelization of natural rivers for flood mitigation causes discontinuity of the riverine corridor, leading to unfavorable conditions for fish movement in the longitudinal direction. To minimize the negative effects, hydraulic structures (e.g. deflectors) are proposed as potential restoration measures in concrete flood channels. In this study, indoor flume experiments were carried out to assess the variation of flow field (velocity magnitude, turbulent kinetic energy, and Reynolds stress) and bed morphology with the inclusion of deflectors. The flow and sediment regimes were then compared in the presence or absence of deflectors. The experimental results indicated that deflectors triggered a non-uniform flow pattern and stimulated riffle-pool sequence formation through local scouring and subsequent deposition. To better understand the response of predaceous chub (Parazacco spilurus) and mud carp (Cirrhinus molitorella) to deflectors, fish trajectories, distribution, and number of transits were analyzed using a video monitoring system. The results suggested that fish responded differently to the baseline (without deflector) and deflector scenarios: (1) fish struggled against the oncoming current when crossing the physical barrier in the channelized section; (2) fish moved and rested in the diverse habitats created by deflectors. Additionally, the presence of sediments in the channel bed was essential in attracting fish to the channelized section. Therefore, it was concluded that using deflectors at appropriate intervals and allowing the existence of sediments in flood channel sections can benefit fish movement and enhance channel naturalization.

CFD와 실증실험 적용을 통한 최적혼화 방법 도출 및 수리구조개선으로 정수장 혼화방법 개선

The existing mixing basin is comprised of 16 basins and each basin has different inflow flux and input chemical flow rate. Therefore, the mixing efficiency of the existing mixing basin was very lower due the inappropriate distribution channel and the nonuniform flow pattern, In this study, in order to investigate the flow pattern and the mixing efficiency, there were simulated the flow patten, the flow stability, and the mixing pattern by using the CFD analysis and experiment for the previous model and the advanced model. As a result of the numerical calculation, CFD results confirm that the weir height is increased to 0.2m from the existing model to obtain the most optimal flow. Because the head water level was more than 0.7m, which showed sufficient mixing strength. Also, in the verification test, the zeta potential, the flow current, the cohesive floc size, and the filtration time were compared with mechanical mixing, showing superiority in all items. By replacing the existing mechanical mixing with a head water level, reducing the number of used mixing basin from 16 to 2, and improving the weir drop height, the length from the mixing basin to the coagulation basin could be reduced by approximately 30m and the flocculation efficiency was improved.

Performance analysis of finned-tube CO2 gas cooler with advanced 1D-3D CFD modelling development and simulation

Due to natural refrigerant applied, CO2 transcritical refrigeration and heat pump systems have been widely applied and attracted more attentions. As a main component, CO2 gas cooler plays an important role in the system performance and thus requires further development for design and control optimizations with advanced technology. Correspondingly, a new coupled 1D and 3D Computational Fluid Dynamics (CFD) model on a finned-tube CO2 gas cooler has been proposed and developed. The CFD model has been validated by comparing with literatures for parameters including airside heat transfer coefficient, refrigerant side temperature profile as well as heating capacity. The model has been applied to predict the heat exchanger performance at different operating conditions of both air and refrigerant sides and maldistributions of air flow inlet. It is found from the simulation results that the refrigerant temperature decreases abruptly in the first coil row and the refrigerant temperature profile along the heat exchanger tubes is affected by thermal conduction between two adjacent tube rows through fins. In addition, the higher air flow inlet velocity can reduce greatly the coil approach temperature and thus improve the system efficiency. Similar effect can also be found from refrigerant pressure. Furthermore, the non-uniform air flow patterns can affect considerably the coil performance in terms of the refrigerant temperature profile, coil approach temperature, coil heating capacity and system energy efficiency. The developed CFD model can be an efficient tool for the performance evaluation and optimisation of the CO2 gas cooler and its associated system.

Experimental study on improving the performance of dry evaporator with rectifying nozzle type critical distributor

In order to ensure uniform distribution of dry evaporator under various operating conditions, two novel distributors based on the distribution concept of ``flow pattern setting & critical distribution'' are proposed. The theoretical analysis and structure design of rectifying nozzle type critical distributor (RD) based on the distribution principle of ``swirling setting & critical distribution'' are carried out. And the mechanism of swirling setting and critical flow of gas-liquid two-phase refrigerant is expounded. The flow pattern setting is to adjust the up-flow non-uniform and asymmetrical flow pattern to ideal annular flow by rectifying elements, to overcome the influence of up-flow flow state on distribution characteristics. The critical distribution is to make the two-phase flow reach the local sound velocity by sonic nozzle, to overcome the influence of the non-uniform heat transfer of each branch of the downflow on distribution characteristics, and solve the influence of inconsistent resistance of each breach, pressure wave oscillation and other unfavorable factors on the heat transfer performance of the dry evaporator. Based on the results of theoretical analysis, the RD is designed, and tested on the performance test system of dry evaporator. The experimental research results show that the distribution effect of RD is the best. The cooling capacity of the dry evaporator with the RD is increased by 22.7% or more, compared with Venturi distributor. The results show that the use of RD restrain the problem of gas-liquid two phase refrigerant mal-distribution in dry evaporator.

Design of Two Experimental Mock-Ups as Proof-of-Concept and Validation Test Rigs for the Enhanced EU DEMO HCPB Blanket

Within the framework of EUROfusion activities, the helium cooled pebble bed (HCPB) breeding blanket is under development in Karlsruhe Institute of Technology (KIT). The enhanced HCPB, using a fissionlike fuel breeder pin assembly configuration, is proposed as the near-term breeding blanket for the European Union DEMOnstration power plant (EU DEMO). The helium gas with a pressure of 8 MPa is used as the coolant, EUROFER is used as the structural material, advanced ceramic breeder pebbles are used as the tritium breeder, and Be12Ti is used as the neutron multiplier material. In contrast to the former HCPB cooling plate configuration, the fuel breeder pin assemblies greatly reduce the pressure drop, reducing the circulating power to the level where state-of-the-art helium turbomachinery can be used. However, because of the reduced coolant velocity in the breeder zone, the heat transfer performance is compromised, especially in the annular channel of the fuel breeder pins. An increased surface roughness is therefore proposed as a heat transfer augmentation technique for the fuel breeder pins. Although heat transfer augmentation using artificial roughness is common, it is relatively novel for small annular gaps with moderate velocity as the ones in the fuel breeder pins. Currently, a dedicated correlation for the small annular rough-wall channel is available to predict the Nu number. This correlation is wished here to be benchmarked and validated experimentally. Therefore, an experimental investigation on a fuel breeder pin mock-up (mock-up 1) is planned. Additionally, based on computational fluid dynamics calculation, unsteady, nonuniform flow patterns were found at the return flow after the jet impingement in the first-wall region. Another upscaled mock-up (mock-up 2) to investigate the nonuniform flow patterns of the return flow in the annular channel of the fuel breeder pin is planned. The dedicated experimental campaigns are foreseen at the Helium Loop Karlsruhe (HELOKA) in KIT as validation and proof-of-concept test rigs for this enhanced pin design. In this paper, the motivation and the preliminary design of these two mock-ups of the enhanced EU DEMO HCPB blanket are shown, together with the plan for the foreseen experiments.

Computational investigation of bounded domain with different orientations using CPCM

Abstract The present work deals with the composite phase change material (CPCM) of 98% paraffin wax and 2% copper nanoparticle, filled into the bounded domain. Effects of orientation (45°, 90°, 135° and 180°) with different wall heating conditions (base, left and top wall) are analyzed numerically to understand the flow patterns and interface morphology developed during melting/solidification processes. The melting/solidification mechanism exhibited non-uniform flow patterns and irregular morphology which are dependent on geometrical orientations and different wall heating conditions. The results revealed that the bounded domain with different orientations have significant effect on natural convection current formation. As the orientation changes, the heat transfer rate gets influenced significantly and convection currents amplifies. Top wall heating arrangement of 180° orientation shows competence in achieving better thermal performance.

Experimental Investigation of Inlet Distortion Effect on Performance of a Micro Gas Turbine

An experimental study has been carried out to determine how inlet total-pressure distortion affects the performance of a micro gas turbine. An inlet simulator is designed and developed to produce and measure distortion patterns at the inlet to the gas turbine. An air jet distortion generator (AJDG) is used to produce nonuniform flow patterns and total pressure probes are installed to measure steady-state total-pressure distribution at the inlet. A set of wind tunnel tests have been performed to confirm the fidelity of distortion generator and measuring devices. Tests are carried out with the gas turbine exposed to inlet flow with 60 deg, 120 deg, and 180 deg circumferential distortion patterns with different distortion intensities. The performance of the gas turbine has been measured and compared with that of clean inlet flow case. Results indicate that the gas turbine performance can be affected significantly facing with intense inlet distortions.

Non-uniform ground-level wind patterns in a heat dome over a uniformly heated non-circular city

Urban heat island-induced circulation, or urban heat dome flow, significantly influences urban thermal environments and air quality in calm wind conditions with stable stratification. An urban heat dome is characterized by convergent inflow at the ground level, divergent outflow at the upper level and upward flow over the city center in calm conditions. We report a new city-shape effect on heat dome flow patterns in a laboratory modeling experiment. For a circular city, both the inflow at the lower level and the outflow at the upper level are axisymmetric. For a square urban area, a non-uniform flow pattern was observed with four dominant diagonal inflows at the ground level and four dominant side outflows (perpendicular to city edges) at the upper level, indicating that the inflow changes direction as it rises over the urban area. The experiments were carried out in two water tank models with stable stratification, using thermal image velocimetry and particle image velocimetry. “Cell-like” and “stripe-like” eddy structures were identified over the modeled urban area, depending on the mean flow speed. To the best of our knowledge, this study reveals for the first time that in calm conditions the shape of an urban area may significantly affect the winds within a city, and thus the local heat transfer coefficients, urban air temperature and urban haze distribution will not be uniform under such conditions. Results on the eddy structures and mean flow fields can provide insights for theoretical analysis on heat transfer models in future studies.

Influence of the hole geometry on the flow distribution in ventricular catheters for hydrocephalus.

Background Hydrocephalus is a medical condition consisting of an abnormal accumulation of cerebrospinal fluid within the brain. A catheter is inserted in one of the brain ventricles and then connected to an external valve to drain the excess of cerebrospinal fluid. The main drawback of this technique is that, over time, the ventricular catheter ends up getting blocked by the cells and macromolecules present in the cerebrospinal fluid. A crucial factor influencing this obstruction is a non-uniform flow pattern through the catheter, since it facilitates adhesion of suspended particles to the walls. In this paper we focus on the effects that tilted holes as well as conical holes have on the flow distribution and shear stress.Methods We have carried out 3D computational simulations to study the effect of the hole geometry on the cerebrospinal fluid flow through ventricular catheters. All the simulations were done with the OpenFOAM® toolbox. In particular, three different groups of models were investigated by varying (i) the tilt angles of the holes, (ii) the inner and outer diameters of the holes, and (iii) the distances between the so-called hole segments.ResultsThe replacement of cylindrical holes by conical holes was found to have a strong influence on the flow distribution and to lower slightly the shear stress. Tilted holes did not involve flow distribution changes when the hole segments are sufficiently separated, but the mean shear stress was certainly reduced.ConclusionsThe authors present new results about the behavior of the fluid flow through ventricular catheters. These results complete earlier work on this topic by adding the influence of the hole geometry. The overall objective pursued by this research is to provide guidelines to improve existing commercially available ventricular catheters.

Effect of non-uniform inlet flow rate on the heat-up process of a solid oxide fuel cell unit with cross-flow configuration

This study simulates the heat-up process of a solid oxide fuel cell unit with the cross-flow configuration, and investigates the effect of the non-uniform inlet flow pattern and the non-uniform deviation on the maximum temperature gradient and preheating time. The numerical method is precise and reliable through the comparison with the analytical solution of previous literature. The results show that the effect of non-uniform inlet flow pattern on the maximum temperature gradient is obvious, and the effect in the fuel side is more obvious than that in the air side. The best choice of the inlet flow pattern is C, which the fuel side is uniform and the air side is the progressively increasing profile. Additionally, the effect of non-uniform inlet flow pattern on the preheating time can not be neglected, and this effect becomes larger when the non-uniform deviation increases.