Irregular Flow Research Articles

Evaluation of mechanical properties of friction stir welded commercially pure aluminium

In this study, friction stir welding (FSW) of commercially pure aluminium is carried out. The main defects existing in this process are cavity, irregular material flow due to unsuitable selection of welding parameters. In this study, to reduce the defects by selecting suitable parameter and welding quality determined by mechanical testing methods and non-destructive testing methods. Welding is done with preheating the base metals and without preheating the base metals and their effects are analyzed with similar parameter. The parameters considered for this work are spindle rotational speed (rpm), tool travel speed (mm/min) and axial force (kN). The experimental results are evaluated by Destructive Test and Non-destructive test methods. The characterization study is performed by Optical microscope and Scanning Electron microscopy (SEM).

DyCache: Dynamic Multi-Grain Cache Management for Irregular Memory Accesses on GPU

GPU utilizes the wide cache-line (128B) on-chip cache to provide high bandwidth and efficient memory accesses for applications with regularly-organized data structures. However, emerging applications exhibit a lot of irregular control flows and memory access patterns. Irregular memory accesses generate many fine-grain memory accesses to L1 data cache. This mismatching between fine-grain data accesses and the coarse-grain cache design makes the on-chip memory space more constrained and as a result, the frequency of cache line replacement increases and L1 data cache is utilized inefficiently. Fine-grain cache management is proposed to provide efficient cache management to improve the efficiency of data array utilization. Unlike other static fine-grain cache managements, we propose a dynamic multi-grain cache management, called DyCache, to resolve the inefficient use of L1 data cache. Through monitoring the memory access pattern of applications, DyCache can dynamically alter the cache management granularity in order to improve the performance of GPU for applications with irregular memory accesses while not impact the performance for regular applications. Our experiment demonstrates that DyCache can achieve a 40% geometric mean improvement on IPC for applications with irregular memory accesses against the baseline cache (128B), while for applications with regular memory accesses, DyCache does not degrade the performance.

The Study of Sand-blocking Characteristic and Flow Field Simulation Analysis of the Ring-shaped Sand-barrier

Aiming at the complexity of wind direction and irregular sand flow in a desert area, a combinatorial ring-shaped sand barrier is used. Stokes law of inertia force and centrifugal force and gravity sedimentation are used. With CFD fluid software Fluent, laminar flow model Equation and κ-ε turbulence model, the wind speed of the sand in the sand-gas-solid two-phase flow passing through the circular sand barrier is studied at different distances and different altitudes after the sand barrier, the wind speeds before and after the sand barrier are compared and analyzed . The mean minimum wind speed behind the single sand barrier was reduced by 32.5% -49.4% compared with that before the sand barrier. The wind speed at different height of the composite sand barrier was reduced by 30% -58.3% compared with the inlet wind speed, which solved the problem of irregular wind and sand control in the desert wind direction.

Stochastic Bifurcation Analysis of an Elastically Mounted Flapping Airfoil

The present paper investigates the effects of noisy flow fluctuations on the fluid-structure interaction (FSI) behaviour of a span-wise flexible wing modelled as a two degree-of-freedom elastically mounted flapping airfoil. In the sterile flow conditions, the system undergoes a Hopf bifurcation as the free-stream velocity exceeds a critical limit resulting in a stable limit-cycle oscillation (LCO) from a fixed point response. On the other hand, the qualitative dynamics changes from a stochastic fixed point to a random LCO through an intermittent state in the presence of irregular flow fluctuations. The probability density function depicts the most probable system state in the phase space. A phenomenological bifurcation (P-bifurcation) analysis based on the transition in the topology associated with the structure of the joint probability density function (pdf) of the response variables has been carried out. The joint pdf corresponding to the stochastic fixed point possesses a Dirac delta function like structure with a sharp single peak around zero. As the mean flow speed crosses the critical value, the joint pdf bifurcates to a crater-like structure indicating the occurrence of a P-bifurcation. The intermittent state is characterized by the co-existence of the unimodal as well as the crater like structure.

Active Control of Thermal Convection in a Rectangular Loop by Changing its Spatial Orientation

The problem of the automatic control of the fluid flow in a rectangular convective loop heated from below is studied theoretically and experimentally. The control is performed by using a feedback subsystem which changes the convection regimes by introducing small discrete changes in the spatial orientation of the loop with respect to gravity. We focus on effects that arise when the feedback controller operates with an unavoidable time delay, which is cause by the thermal inertia of the medium. The mathematical model of the phenomenon is developed. The dynamic regimes of the convection in the thermosyphon loop under control are studied. It is shown that the proposed control method can successfully stabilize not only a no-motion state of the fluid, but also time-dependent modes of convection including the irregular fluid flow at high values of the Rayleigh number. It is shown that the excessive gain of the proportional feedback can result in oscillations in the loop orientation exciting the unsteady convection modes. The comparison of the experimental data obtained for dielectric oil and dodecane with theory is given, and their good agreement is demonstrated.

CFD Analysis in Subsea and Marine Technology

Computational Fluid Dynamics (CFD) is established in design and analysis for a range of industries, but its use in Marine and Naval Hydrodynamics is behind the trend. This can be attributed to the complexity of modelling needs, including presence of free surface,irregular transient flows, fluid-structure coupling and presence of established modelling tools based on potential theory.In this paper, state-of-the-art of CFD in Naval Hydrodynamics, wave and offshore applications is given, with an update of recent advances, validation and computing requirements for typical simulation cases.

Identifying migrants in anthropology: The few cases from Portugal

In opposition to other European countries such as Greece and Italy, Portugal is not directly suffering the effects of the migration crisis due to its geographic position. There are no irregular migration flows or other cross-border crime at specific border crossing points and the stories of successfully relocated migrants are very scarce since they simply do not stay in Portugal. This situation is reflected in the requests for age estimation of sub adults to the National Institute of Legal Medicine and Forensic Sciences. The number of requests is low. Yet, there is a protocol, which in principle follows the recommendations of the Study Group on Forensic Age Diagnostics of the German Society of Legal Medicine. Additionally, some research is ongoing, facing the Portuguese reality where the unidentified individuals arrive mainly from Africa, Brazil and the Middle-East. As well as presenting a typical case, we introduce the research project, which is just starting. Namely, we propose to estimate the age of majority through the retrospective analyses of the third molar in orthopantomographs from Portuguese, Brazilian and Angolan individuals, aiming to improve the precision and accuracy of the methodology. Thus, even with the scarce number of cases in Portugal, efforts are made to maintain a forefront response to the needs of the forensic experts.

Post-Disaster Risk Financing Instruments as a Strategic Financing Option for Disaster Risk Reduction in the Kenyan National Disaster Platform

Mobilization of financial resources for disaster risk reduction represent value for money because for every dollar invested in disaster risk reduction, between four and seven dollars are saved in the long run. The reactive emergency aid business model commonly applied is not helping much in disaster risk reduction because it suffers from irregular flow of funds making it unpredictable and complex in its arrangement for acquisition as well as eventual disbursement. Disaster risk financing instruments are increasingly at the centre of this nuxes since there exists an inseparable relationship between disaster risk financing instruments on one hand and disaster risk reduction activities on the other hand. Post-disaster risk financing instruments are budgetary reallocations, domestic credit, external credit, donor assistance and tax increase. Disasters pose daunting barriers to development in developing countries because they are inadequately prepared due to weaknesses of their economies, high level of indebtedness and rigid budgetary processes which do not allow them to reallocate budget post-disaster. This article analyzes the cause effect relationship between post-disaster risk financing instruments and risk reduction in the Kenya national platform. The primary data used in the analysis is based principally on a survey of 60 respondents interviewed in 2016 in the public and private organizations. Secondary data attained from archival records, UNDP and Development Initiatives documentation centres were used to cross-validate primary data. Correlational research design was adopted while statistical analysis employed was Pearson’s co-efficient of correlation and multiple regression analysis. The results show that there is a positive and significant relationship between post-disaster risk financing instruments and disaster risk reduction in Kenyan national disaster platform (r=0.286, p=0.000<0.01). The findings point to the need for the establishment of a disaster risk revolving fund in Kenya which is structured along the post-disaster risk financing sources. Keywords: Post-disaster risk financing instruments, Strategic financing option, Risk reduction and Kenyan national disaster platform.

Spatial filtering velocimetry for surface velocity measurement of granular flow

In this study, we develop the spatial filtering velocimetry (SFV) technique to measure the velocity distribution of small spherical and irregular particle flows using a linear CCD camera. In addition, energy barycentre correction algorithm is used to enhance the measurement accuracy. A constantly running conveyor belt is used to test the accuracy of this SFV system. Furthermore, the velocity distributions of the spherical and irregular particle flows in a rotating drum are measured to demonstrate the usability of this method in a granular system. We further discuss the effect of the key system parameters on the results of the measurement, and the optimal thresholds of the parameters are given in this paper.

Influence the loading conditions and the stress concentrators on the spatial-time inhomogeneity due to the yield delay and the jerky flow: study by using the digital image correlation and the infrared analysis

The paper deals with the investigation of the temporal instabilities and spatial localization due to the Lüders behavior and the Portevin–Le Chatelier effect in the carbon steel C1010 and the aluminummagnesium alloy AA5052, which manifest the unstable plastic flow. The digital image correlation technique and the infrared thermography were used to capture and study the processes of the initiation and propagation of the deformation bands. The main part of the research focuses on the estimation of the influence of the loading system’s stiffness on the irregular plastic flow, which was carried out on flat specimens with complicated geometry and on specimens with additional deformable parts.

Randomness Representation of Turbulence in Canopy Flows Using Kolmogorov Complexity Measures

Turbulence is often expressed in terms of either irregular or random fluid flows, without quantification. In this paper, a methodology to evaluate the randomness of the turbulence using measures based on the Kolmogorov complexity (KC) is proposed. This methodology is applied to experimental data from a turbulent flow developing in a laboratory channel with canopy of three different densities. The methodology is even compared with the traditional approach based on classical turbulence statistics.

Online sequential condition prediction method of natural circulation systems based on EOS-ELM and phase space reconstruction

Natural circulation design is widely used in the passive safety systems of advanced nuclear power reactors. The irregular and chaotic flow oscillations are often observed in boiling natural circulation systems so it is difficult for operators to monitor and predict the condition of these systems. An online condition forecasting method for natural circulation system is proposed in this study as an assisting technique for plant operators. The proposed prediction approach was developed based on Ensemble of Online Sequential Extreme Learning Machine (EOS-ELM) and phase space reconstruction. Online Sequential Extreme Learning Machine (OS-ELM) is an online sequential learning neural network algorithm and EOS-ELM is the ensemble method of it. The proposed condition prediction method can be initiated by a small chunk of monitoring data and it can be updated by newly arrived data at very fast speed during the online prediction. Simulation experiments were conducted on the data of two natural circulation loops to validate the performance of the proposed method. The simulation results show that the proposed predication model can successfully recognize different types of flow oscillations and accurately forecast the trend of monitored plant variables. The influence of the number of hidden nodes and neural network inputs on prediction performance was studied and the proposed model can achieve good accuracy in a wide parameter range. Moreover, the comparison results show that the proposed condition prediction method has much faster online learning speed and better prediction accuracy than conventional neural network model.

Key hydraulic drivers and patterns of fine sediment accumulation in gravel streambeds: A conceptual framework illustrated with a case study from the Kiewa River, Australia

Fine sediment processes in gravel beds may have significant impacts to overall river ecosystem function. In addition to gravitational deposition, horizontal intragravel transport has been recognized to influence fine sediment accumulation. However, the specific hydraulic mechanisms and origin of fine sediment movement are not clearly identified. The purpose of this study was to investigate key hydraulic drivers and patterns of fine sediment accumulation. Using a conceptual framework to set the scene, we implemented an experimental setup in a gravel lateral bar subject to irregular flow fluctuations in the Kiewa River (Australia). We installed nine sets of sediment collector pairs and piezometers into the gravel. Each pair included one horizontally and one horizontally-vertically perforated collector. Mid-range, rather than peak flows, covering the site in water drove fine sediment deposited in the collectors. We estimated horizontal contribution to final deposition as 59%. Such contribution resulted from shear stresses >3Nm−2 promoting streamwise near-bed turbulence at the water-sediment interface during flooded conditions. Despite high subsurface hydraulic gradients, intragravel transport in the lower sediment layers via Darcy flow did not show any influence to fine sediment deposition. Our findings contribute to an improved understanding of fine sediment accumulation processes, key for overall river ecosystem functioning, particularly in regulated rivers.

Analysis of pore scale fluid migration in a porous medium- application to coal rock seam

PurposeThe purpose of this study is to digitize the porous structure and reconstruct the geometry of the rock by using the image processing software photoshop (PS) and ant colony algorithm coded with compiler Fortran PowerStation (fps) 4.0 based on the microscopic image of a typical rock mass.Design/methodology/approachThe digital model of the microstructure of the porous coal rock was obtained, and imported into the numerical simulation software to build the finite element model of microstructure of the porous coal rock. Creeping flow equations were used to describe the fluid flow in the porous rock.FindingsThe simulation results indicate that the method utilized for reconstructing the microstructure of the porous coal rock proposed in this work is effective. The results demonstrate that the transport of fluid in a porous medium is significantly influenced by the geometric structure of the pore and that the heterogeneous porous structure would result in an irregular flow of the fluid.Research limitations/implicationsThe authors did not experience a limitation.Practical implicationsThe existence of the pores with dead ends would hinder the fluid to flow through the coal rock and reduce the efficiency of extracting fluid from the porous coal rock. It is also shown that the fluid first enters the large pores and subsequently into the small pore spaces.Social implicationsThe paper provides important and useful results for several industries.Originality valueImage processing technology has been utilized to incorporate the micro image of the porous coal rock mass, based on the characteristics of pixels of the micro image. The ant colony algorithm was used to map out the boundary of the rock matrix and the pore space. A FORTRAN code was prepared to read the micro image, to transform the bmp image into a binary format, which contains only two values. The digital image was obtained after analyzing the image features. The geometric structure of the coal rock pore was then constructed. The flow process for the micro fluid in the pore structure was illustrated and the physical process of the pore scale fluid migration in the porous coal seam was analyzed.

Remediation of Thiothrix spp. associated bulking problems by raw wastewater feeding: A full-scale experience

An industrial wastewater treatment plant (WWTP) in Australia has long suffered from bulking problems associated with the proliferation of Thiothrix spp. The WWTP consists of a covered anaerobic lagoon (CAL) followed by a sequencing batch reactor (SBR). The CAL functions as both an anaerobic digester and surge lagoon for the irregular flow of wastewater generated from the production of seasonal products. Chemical analysis of the raw influent showed it was composed of a mixture of organic acids, phenols and alcohols. The CAL effluent was characterised by high acetic acid and phenolic concentrations. An attempt was made to manipulate the SBR microbial community to improve settling by direct feeding small volumes of raw influent into the SBR. After raw feeding, the plant ceased bulking as the settled sludge volume reduced from 930 to 200mLL−1. 16S rRNA gene profiling and biovolumes of SBR samples revealed major changes in the microbial community. The Thiothrix spp. population decreased from 36.8% to 0.2%, and Zoogloea spp. dominated all samples after raw feeding. Therefore, direct feeding is proposed as a control method for industrial plants with surge/anaerobic lagoons in order to manage the bulking problems caused by Thiothrix spp. in downstream SBRs.

PageRank versatility analysis of multilayer modality-based network for exploring the evolution of oil-water slug flow

Numerous irregular flow structures exist in the complicated multiphase flow and result in lots of disparate spatial dynamical flow behaviors. The vertical oil-water slug flow continually attracts plenty of research interests on account of its significant importance. Based on the spatial transient flow information acquired through our designed double-layer distributed-sector conductance sensor, we construct multilayer modality-based network to encode the intricate spatial flow behavior. Particularly, we calculate the PageRank versatility and multilayer weighted clustering coefficient to quantitatively explore the inferred multilayer modality-based networks. Our analysis allows characterizing the complicated evolution of oil-water slug flow, from the opening formation of oil slugs, to the succedent inter-collision and coalescence among oil slugs, and then to the dispersed oil bubbles. These properties render our developed method particularly powerful for mining the essential flow features from the multilayer sensor measurements.

Irregular migratory flows

PurposeThe purpose of this study is to navigate the challenges irregular migratory flows generate for cities and urban systems. The migration and refugee crises that challenged Europe in 2015-2016 revealed that the developed world cities and urban areas are largely unprepared to address challenges that irregular migratory flows generate. This paper queries the smart and resilient cities’ debates, respectively, to highlight that migration-related challenges and opportunities have not been explicitly addressed in those deliberations. This creates a disconnect between what these debates promise and what cities/urban systems increasingly need to address on a daily basis. Subsequently, a way of bridging that disconnect is proposed and its policy-making implications discussed.Design/methodology/approachTo suggest ways of navigating irregular migration-inflicted challenges cities/urban areas face, a nexus between the smart cities and resilient cities’ debates is established. By placing advanced sophisticated information and communication technologies (ICTs) at the heart of the analysis, a novel dynamic ICTs’ enabled integrated framework for resilient urban systems is developed. The framework’s dynamics is defined by two hierarchically interconnected levers, i.e. that of ICTs and that of policy-design and policy-making. Drawing from qualitative analysis and process tracing, the cross-section of policy design and policy-making geared towards the most efficient and ethically sensitive use of sophisticated ICTs is queried. Subsequently, options available to cities/urban systems are discussed.FindingsThe ICTs’ enabled integrated framework for resilient urban systems integrates the effectiveness of migrants and refugees’ policy design and policy-making in human-centred thinking, planning and policy-design for resilient urban systems. It places resilient approaches in the spotlight of research and policy-making, naming them the most effective methods for promoting a humanistic smart cities and resilient urban systems vision. It highlights critical junctions that urban systems’ stakeholders must consider if the promise of emerging sophisticated ICTs is to be employed effectively for the entire society, including its most vulnerable members.Research limitations/implicationsFirst, when designing ICTs’ enabled integrated resilient urban systems, the key stakeholders involved in the policy-design and policy-making process, including local, national and regional authorities, must employ a holistic view to the urban systems seen through the lens of hard and soft concerns as well as considerations expressed by the receiving and incoming populations. Second, the third-sector representatives, including non-governmental organizations (NGOs) and other actors, need to be seen as peers in integrated humanistic networks, thereby contributing critical, unbiased knowledge flows to infrastructures, which promote fair and inclusive participation of migrants and refugees in local economies.Practical implicationsThe ICTs’ enabled integrated framework for resilient urban systems promotes a humanistic smart cities’ and resilient urban systems’ vision. It suggests how to design and implement policies apt to meet the needs of both receiving and incoming populations along value chains specific to smart and resilient cities. It promotes emerging sophisticated ICTs as the subtle, yet key, enabler of data ecosystems and customized services capable of responding to critical societal needs of the receiving and the incoming populations. In addition, the framework suggests options, alternatives and strategies for urban systems’ stakeholders, including the authorities, businesses, NGOs, inhabitants and ICTs’ providers and vendors.Originality/valueThe value added of this paper is three-fold. At the conceptual level, by bringing together the smart cities and resilient cities debates, and incorporating sophisticated ICTs in the analysis, it makes a case for their usefulness for cities/urban areas in light of challenges these cities/urban areas confront each day. At the empirical level, this analysis maps the key challenges that cities and their stakeholders face in context of migratory flows and highlights their dual nature. At the policy-making level, this study makes a case for a sound set of policies and actions that boost effective use of ICTs beyond the smart technology hype.

WaterOnto: Ontology of Context-Aware Grid-Based Riverine Water Management System

The management of riverine water always remains a big challenge, because the volatility of water flow creates hurdles to determine the exact time and quantity of water flowing in rivers and available for daily use. The volatile water caused by various water sources and irregular flow pattern generates different kinds of challenges for management. Distribution of flow of water in irrigation network affects the relevant community in either way. In the monsoon seasons, river belt community high risk of flood, while far living community suffering drought. Contemplating this situation, we have developed an ontology for context-aware information representation of riverine water management system abetting the visualization and proactive planning for the complex real-time situation. The purpose of this WaterOnto is to improve river water management and enable for efficient use of this precious natural resource. This would also be helpful to save the extra water being discharged in sea &amp; non-irrigational areas, and magnitude and location of water leakage. We conceptualized stakeholder and relevant entities. We developed a taxonomy of irrigation system concepts in machine process able structure. Being woven these hierarchies together we developed a detailed conceptualization of river flow that helps us to manage the flow of water and enable to extract danger situation.

Controlling irregular immigration at the European Union’s southern maritime border. An emerging system driven by “migration emergencies"

Over the last 25 years the southern maritime border of the European Union witnessed the interaction of considerable and increasingly complex irregular migration flows in the Mediterranean with the progressive construction and implementation of restrictive migration control policies by the European Union and its member states at their external borders. The article describes the evolving migration patterns and changes in migration routes both as a stimulus and a consequence of locally stepping up migration control at the emerging hotspots at different parts of the border, creating deviation effects in migration routes with alternative points of entry and higher costs and risks for migrants. Special attention is given to the impact of the 2015 refugee crisis on border management and the new challenges it poses to the asylum system and the protection of fundamental rights.

Reliability Evaluation of Car Power Module Using Electrical-Thermal-Structural Coupled Analysis Based on Field Driving Data

Power module is a system consisting electronic components to perform the power conversion. Power module is a significant impact on the operation of the equipment and its reliability evaluation is very important. Especially, intermittent electric current flowing in the power module causes repeating the heat generation and cooling. It produces a large thermal stress and cause thermal fatigue failure in the solder part. Car makers usually use the power cycle test to measure the thermal fatigue life. But, it is difficult to simulate the field conditions by this test method. Because, in the actual use environment, the irregular current flows with an irregular cycle. In this research, analysis in the conditions near real usage environment was conducted. It aims at establishment of the reliability assessment method of the power module near a real operating condition.