Numerical Reliability Study Based on Rheological Input for Bingham Paste Pumping Using a Finite Volume Approach in OpenFOAM

Rheological quantification is important in many industries, the concrete industry in particular, e.g., pumping, form filling, etc. Instead of performing expensive and time-consuming experiments, numerical simulations are a powerful means in view of rheological assessment. However, due to the unclear numerical reliability and the uncertainty of rheological input data, it is important for the construction industry to assess the numerical outcome. To reduce the numerical domain of cementitious suspensions, we assessed the numerical finite volume simulations of Bingham paste pumping flows in OpenFOAM. We analysed the numerical reliability, first, irrespective of its rheological input by comparison with the literature and theory, and second, dependent on a certain rheological quantification by comparison with pumping experiments. Irrespective of the rheological input, the numerical results were significantly accurate. Dependent on the rheological input, a numerical mismatch, however, existed. Errors below 1% can be expected for proposed numerical rules of thumb: a bi-viscous regularisation, with pressure numbers higher than 5/4. To improve bias due to uncertain rheology, a rheological configuration close to the engineer’s aimed application should be used. However, important phenomena should not be overlooked. Further assessment for lubrication flows, in, e.g., concrete pumping, is still necessary to address concerns of reliability and stability.

Dynamics of salt intrusion in the Mekong Delta: results of field observations and integrated coastal–inland modelling

On the list of challenges facing the world largest deltas, increased saline water intrusion (SWI) in the surface water system and its role in jeopardizing freshwater supply are often ranked very high. Yet, detailed process-based studies of SWI at the whole delta scale are limited, and the trends are regularly associated with global sea level rise. Here, using field measurements and a sophisticated 3D model that integrates the riverine, rural, estuarine, and coastal dynamics within one numerical domain, we study SWI at the scale of the Mekong Delta in extensive detail. While many studies downscale the SWI problem to a topic within an estuary, we show that the physical processes on the continental shelf, such as monsoon-driven ocean surge, directly influence salinity dynamics within the delta. Typical values of 20–40 cm surge over the continental shelf contribute to up to 10 km of further SWI. The delta's estuarine system is also more sensitive than many other systems to variations of river discharge. Furthermore, spring–neap variability plays a key role in SWI in the delta. The estuarine variability from a stratified to a mixed system between neap and spring tides develops 3D processes such as estuarine circulation and tidal straining that become the main upstream salt transport mechanisms. The 3D nature of salinity dynamics, and the role of upstream and downstream processes, suggests that compromising on dimension or extent of the numerical domain can limit the accuracy of predictions of SWI in the delta. The study also showcases the fact that riverbed incision in response to anthropogenic sediment starvation in the last 2 decades has increased stratification and activated or magnified 3D salt transport subprocesses that amplify upstream salt transport. With all the external forces on the delta, namely climate change and an altered hydrological regime by the upstream dams, due to deeper estuarine channels (driven by sand mining and upstream impoundments) compared to its near past, the delta itself has become far more vulnerable to even mild natural events. This exemplifies the fundamental importance of preserving the sediment budget and riverbed levels in protecting the world's deltas against SWI.

Dynamics of salt intrusion in the Mekong Delta; results of field observations and integrated coastal-inland modelling

In the list of challenges facing the world largest deltas, increased salt intrusion and its role in jeopardizing freshwater supply is often ranked very high. Yet, detailed process-based studies of salt intrusion at the whole delta scale are limited and the trends are regularly associated to global sea level rise. Here, using field measurements and a sophisticated 3D model that integrates the riverine, rural, estuarine, and coastal dynamics within one numerical domain, we study salt intrusion at the scale of the Mekong Delta in extensive detail. While many studies down-scale the salt intrusion problem to a topic within an estuary, we show that the continental shelf is an intrinsic component of the delta, and its physical processes, such as monsoon-driven ocean surge, directly influence salinity dynamics within the delta. Typical values of 20–40 cm surge over the continental shelf contribute to up to 10 km of further salt intrusion. The delta's estuarine system is also more sensitive than many other systems to upstream discharge variations. Furthermore, spring-neap variability plays a key role in salt intrusion in the delta. The estuarine variability from a stratified to a mixed system between neap and spring tides develops 3D processes such as estuarine circulation and tidal straining that become the main upstream salt transport mechanisms. The 3D nature of salinity dynamics, and the role of upstream and downstream processes, suggests that compromising on dimension or extent of the numerical domain, can limit the accuracy of predictions of salt intrusion in the delta. The study also showcases that riverbed incision in response to anthropogenic sediment starvation in the last two decades, has increased stratification, and activated or magnified 3D salt transport sub-processes that amplify upstream salt transport. With all the external forces on the delta namely climate change and altered hydrological regime by the upstream dams, due to deeper estuarine channels (driven by sand mining and upstream impoundments), the delta itself is far more vulnerable to even mild natural events. This exemplifies the fundamental importance of preserving the sediment budget and riverbed levels in protecting the world's deltas against salt intrusion.

Resolução de sistemas de equações lineares por um sujeito cego: um experimento com foco na exploração das variáveis de Coulange

ResumoO objetivo deste trabalho é apresentar a resolução de dois problemas envolvendo sistemas de equações lineares por um sujeito cego do 9º ano do ensino fundamental II. A metodologia adotada para coleta e análise dos dados foi o Design Experiments. Utilizamos os estudos de Coulange sobre variáveis para nortear nossas análises. Segundo ela, é possível identificar 8 variáveis em problemas envolvendo sistemas de equações lineares. No experimento de ensino aplicado, destacamos duas variáveis: V4 que se refere ao domínio numérico de medida de grandezas desconhecidas: conjunto numérico dos naturais, inteiros, reais, entre outros (problema 1) e V6 que trata da natureza redundante ou contraditória das informações a respeito das grandezas desconhecidas (problema 2). Nosso sujeito participante da investigação resolveu, facilmente, os dois problemas algebricamente, porém houve dificuldade para determinar a resposta do problema 2, que envolvia informações contraditórias. Palavras-chave: Sistemas de equações lineares; sujeito cego; variáveis de Coulange.AbstractThe objective of this work is to present the resolution of two problems involving systems of linear equations by a blind subject in the 9th grade of elementary school. The methodology adopted for data collection and analysis was Design Experiments. We used Coulange's studies on variables to guide our analyzes. According to her, it is possible to identify 8 variables in problems involving systems of linear equations. In the applied teaching experiment, we highlight two variables: V4 which refers to the numerical domain of measurement of unknown quantities: numerical set of naturals, integers, reals, among others, (problem 1) and V6 that deals with the redundant or contradictory nature of the information regarding unknown quantities (problem 2). Our subject easily solved both problems algebraically, but it was difficult to determine the answer to problem 2, which involved contradictory information.Keywords: Systems of linear equations; blind subject; Coulange variables.

Numerical Simulation of River Inflows in Rijeka Bay Coastal Area

In this paper, a model of water flow in the Porto Baroš has been developed, which is the part of the Rijeka coastal area, for the purpose of its renovation and conversion. For numerical simulation purposes, the depth of the seabed of Port was previously performed, based on which the geometry and numerical domain of Port were made. By conducting the flow simulation, the analysis was carried out, after which the analyses of the conceptual solutions with the introduction of the pipe discharge were performed with the aim of reducing the water pollution of the Porto Baroš area. Port geometry will be made in commercial SMS software and numerical domains and simulations in OpenFOAM open-source software.

Semiconservative reduced speed of sound technique for low Mach number flows with large density variations

Context. The reduced speed of sound technique (RSST) has been used for efficient simulation of low Mach number flows in solar and stellar convection zones. The basic RSST equations are hyperbolic and are suitable for parallel computation by domain decomposition. The application of RSST is limited to cases in which density perturbations are much smaller than the background density. In addition, nonconservative variables are required to be evolved using this method, which is not suitable in cases where discontinuities such as shock waves coexist in a single numerical domain. Aims. In this study, we suggest a new semiconservative formulation of the RSST that can be applied to low Mach number flows with large density variations. Methods. We derive the wave speed of the original and newly suggested methods to clarify that these methods can reduce the speed of sound without affecting the entropy wave. The equations are implemented using the finite volume method. Several numerical tests are carried out to verify the suggested methods. Results. The analysis and numerical results show that the original RSST is not applicable when mass density variations are large. In contrast, the newly suggested methods are found to be efficient in such cases. We also suggest variants of the RSST that conserve momentum in the machine precision. The newly suggested variants are formulated as semiconservative equations, which reduce to the conservative form of the Euler equations when the speed of sound is not reduced. This property is advantageous when both high and low Mach number regions are included in the numerical domain. Conclusions. The newly suggested forms of RSST can be applied to a wider range of low Mach number flows.

NUMERICAL MODELLING METHODOLOGY FOR TSUNAMI FLOOD RISK ASSESSMENT IN URBAN AREAS

Several recent tsunami events worldwide have increased the general public´s awareness of the inherent risk many coastal communities face. Accordingly, academics and professionals have sought to acquire a better understanding of the underlying physical processes involved, and have developed increasingly sophisticated numerical tools to simulate them. One important characteristic of the tsunami flood tragedies that must be acknowledged is that they occur in urban areas, where the built environment is likely to determine the flow, and hence, the flood risk. Despite this fact, relatively little literature covers the particular challenges of modelling the hydrodynamic interactions of the tsunami flood and the buildings and infrastructure. In this work we propose the indirect inclusion of the built environment's effect by actually excluding every building from the numerical domain, enclosing them in an internal reflective boundary condition. The objective is two-fold: it allows a reasonable inclusion of the flow funneling, and it reduces the number of cells in the numerical domain, allowing the use of a higher grid resolution in the expected wet domain, and to achieve shorter simulation runtimes. The methodology was validated against measurements of flow depth, velocity, and momentum on a scale model of the city of Seaside, Oregon. The model and methodology were subsequently used to produce flood depth and velocity maps for 11 coastal cities in Chile, caused by the likely maximum mega-thrust earthquake for each of them.

Verbal structure of numerals and digits handwriting: New evidence from kinematics

Two experiments used a digitizing tablet to analyse the temporal, spatial, and kinematic characteristics of handwritten production of arabic numbers. They addressed a specific issue of the numerical domain: Does the lexical and syntactic structure of verbal numerals influence the production of arabic numerals (Experiments 1 and 2), even after enforced semantic processing in a comparison task (Experiment 2)? Subjects had to write multi-digit arabic numerals (e.g., 1200) presented in two different verbal structures: a multiplicative one (e.g., teen-hundred, douze cents (twelve hundred)) or an additive one (e.g., thousand-unit-hundred, mille deux cents (one thousand two hundred)). Results show differences in the inter-digit jumps that reflect the influence of the structure of verbal numerals, even after the semantic task. This finding is discussed with regard to different models of number transcoding (McCloskey, Caramazza, & Basili, 1985; Power & Dal Martello, 1990, 1997).