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\"Exploring the concept of homotopy from topology, different kinds of homotopy-based methods have been proposed for analytically solving nonlinear differential equations, given by approximate series solutions. Homotopy-Based Methods in Water Engineering attempts to present the wide applicability of these methods to water engineering problems. It solves all kinds of nonlinear equations, namely algebraic/transcendental equations, ordinary differential equations (ODEs), systems of ODEs, partial differential equations (PDEs), system of PDEs, and integro-differential equations using the homotopy-based methods\"-- Provided by publisher.

With a view towards modelling the foam improved oil recovery process, fractional flow theory is used to study the dynamics of a foam as it propagates in a porous medium that is initially filled with liquid. In particular, a case is studied whereby, at a certain time, the net pressure driving the foam is decreased below the hydrostatic pressure at depth, leading to a local change in the flow direction. This is known as flow reversal. In both forward and reverse flow, the boundary between foamed gas and liquid is found as a discontinuous jump in liquid saturation. Over a certain thickness in the neighbourhood of this discontinuity, foam is finely textured, and the mobility of foamed gas drops by orders of magnitude relative to either pure gas or pure liquid. In reverse flow, however, the foam mobility itself and also the thickness over which low mobilities apply might differ from the forward flow case. Fractional flow theory reveals that the thickness of the low mobility region, and hence the resistance to motion that it presents, increases directly proportional to the distance travelled. Previous studies recognised this, but assumed the thickness of this region to be just a small fraction of the distance travelled by the discontinuity. Here, however, we demonstrate that the extent of the low mobility region, in both forward and reverse flow, accounts for a considerable fraction of the distance travelled by the foam, despite what was assumed in previous works. Article Highlights Flow of finely textured, low mobility foam in a porous medium is studied under forward and then reverse flow conditions Foam is even less mobile in reverse flow than forward flow, but low mobility regions cover a comparable spatial extent Low mobilities confined to small domain of liquid saturations, but not a small spatial domain in the medium

To achieve sustainable tourism, the tourism development authorities have used advanced technologies to promote destinations, attract visitors, and protect the environment. Accordingly, while the available research on tourism technologies indicates that virtual reality (VR) matters in the visit intention of potential tourists, the mechanism of their inner senses when experiencing VR technologies is overlooked. To fill in this void, this study develops a comprehensive conceptual model for investigating the influence of VR technological features on tourists’ minds, and consequently, their destination visit intention. This study integrates the technology acceptance model, stimuli-organism-response model, and flow theory into a unified conceptual model for a comprehensive understanding of tourists’ behavior. By focusing on tourists’ decision-making and behavior processes, this study sheds new light on how VR stimuli (i.e., vividness and interactivity) could translate into tourists’ attitudes and visiting intentions. This conceptual model is then tested and validated using structural equation modeling on survey data collected from 311 VR users after experiencing virtual tours designed for destinations in Vietnam. The findings indicate that virtual tours affect tourists’ psychological well-being, which translates into visiting intention. Based on the results, this study emphasizes the role of VR as a powerful marketing tool to promote a destination. Furthermore, approaches to enhance the effectiveness of VR tours, particularly, for tourism developers, are proposed. This study thus contributes to the literature in the area of VR tourism, contributing both theoretical and practical knowledge.

CO 2 flood is one of the most successful and promising enhanced oil recovery technologies. However, the displacement is limited by viscous fingering, gravity segregation and reservoir heterogeneity. Foaming the CO 2 and brine with a tailored surfactant can simultaneously address these three problems and improve the recovery efficiency. Commonly chosen surfactants as foaming agents are either anionic or cationic in class. These charged surfactants are insoluble in either CO 2 gas phase or supercritical phase and can only be injected with water. However, some novel nonionic or switchable surfactants are CO 2 soluble, thus making it possible to be injected with the CO 2 phase. Since surfactant could be present in both CO 2 and aqueous phases, it is important to understand how the surfactant partition coefficient influences foam transport in porous media. Thus, a 1-D foam simulator embedded with STARS foam model is developed. All test results, from different cases studied, have demonstrated that when surfactant partitions approximately equally between gaseous phase and aqueous phase, foam favors oil displacement in regard to apparent viscosity and foam propagation speed. The test results from the 1-D simulation are compared with the fractional flow theory analysis reported in the literature.

In traffic flow theory, there is a relationship between the number of vehicles in a certain area and their average speed, the so-called macroscopic fundamental diagram (MFD). Related control concepts involve limiting the inflow into an area, so-called perimeter control. This may increase both the flow inside the controlled area and the outflow rate, reducing overall delays. This control concept is taught in classes on traffic flow theory around the globe. This paper presents an experiment that can be run in class to create the MFD with a group of students. The basic idea is that we have a confined area where participating students have to walk a predefined route. We repeat this experiment several times (runs of 2–4 minutes each), each time with a different, pre-defined number of students being simultaneously in the area (the accumulation). The number of students is controlled by metering the inflow of participants. Exit flow rates are determined for each run by dividing the number of exiting participants by the run time. One run will hence yield one observed combination of number of participants and run time. From this, an accumulation and exit flow rate can be computed. The Macroscopic Fundamental Diagram (MFD) is then created by plotting the exit flow rates and accumulation of all runs. Students can this way derive this MFD from data. Moreover, they also experience during the walking how delays change with accumulation, and thereby the experiment intuitively teaches them the concepts of the MFD and perimeter control. The paper describes the experiment, and provides tools (software, routes) for repeating the experiment with other groups.

The application of vehicle-to-everything (V2X) technology has resulted in the traffic environment being different from how it was in the past. In the V2X environment, the information perception ability of the driver–vehicle unit is greatly enhanced. With V2X technology, the driver–vehicle unit can obtain a massive amount of traffic information and is able to form a connection and interaction relationship between multiple vehicles and themselves. In the traditional car-following models, only the dual-vehicle interaction relationship between the object vehicle and its preceding vehicle was considered, making these models unable to be employed to describe the car-following behavior in the V2X environment. As one of the core components of traffic flow theory, research on car-following behavior needs to be further developed. First, the development process of the traditional car-following models is briefly reviewed. Second, previous research on the impacts of V2X technology, car-following models in the V2X environment, and the applications of these models, such as the calibration of the model parameters, the analysis of traffic flow characteristics, and the methods that are used to estimate a vehicle’s energy consumption and emissions, are comprehensively reviewed. Finally, the achievements and shortcomings of these studies along with trends that require further exploration are discussed. The results that were determined here can provide a reference for the further development of traffic flow theory, personalized advanced driving assistance systems, and anthropopathic autonomous-driving vehicles.

Purpose This study aims to validate the linear flow theory with computational fluid dynamics (CFD) simulations and to propose a novel shape for the airfoil that will improve supersonic aerodynamic performance compared to the National Advisory Committee for Aeronautics (NACA) 64a210 airfoil. Design/methodology/approach To design the new airfoil shape, this study uses a convex optimization approach to obtain a global optimal shape for an airfoil. First, modeling is conducted using linear flow theory, and then numerical verification is done by CFD simulations using ANSYS Fluent. The optimization process ensures that the new airfoil maintains the same cross-sectional area and thickness as the NACA 64a210 airfoil. This study found that an efficient way to obtain the ideal airfoil shape is by using linear flow theory, and the numerical simulations supported the assumptions inherent in the linear flow theory. Findings This study’s findings show notable improvements (from 4% to 200%) in the aerodynamic performance of the airfoil, especially in the supersonic range, which points to the suggested airfoil as a potential option for several fighter aircraft. Under various supersonic conditions, the optimized airfoil exhibits improved lift-over-drag ratios, leading to improved flight performance and lower fuel consumption. Research limitations/implications This study was conducted mainly for supersonic flow, whereas the subsonic flow is tested for a Mach number of 0.7. This study would be extended for both subsonic and supersonic flights. Practical implications Convex optimization and linear flow theory are combined in this work to create an airfoil that performs better in supersonic conditions than the NACA 64a210. By closely matching the CFD results, the linear flow theory's robustness is confirmed. This means that the initial design phase no longer requires extensive CFD simulations, and the linear flow theory can be used quickly and efficiently to obtain optimal airfoil shapes. Social implications The proposed airfoil can be used in different fighter aircraft to enhance performance and reduce fuel consumption. Thus, lower carbon emission is expected. Originality/value The unique aspect of this work is how convex optimization and linear flow theory were combined to create an airfoil that performs better in supersonic conditions than the NACA 64a210. Comprehensive CFD simulations were used for validation, highlighting the optimization approach's strength and usefulness in aerospace engineering.

Purpose The purpose of this paper is to apply the Peridynamic differential operator (PDDO) to incompressible inviscid fluid flow with moving boundaries. Based on the potential flow theory, a Lagrangian formulation is used to cope with non-linear free-surface waves of sloshing water in 2D and 3D rectangular and square tanks. Design/methodology/approach In fact, PDDO recasts the local differentiation operator through a nonlocal integration scheme. This makes the method capable of determining the derivatives of a field variable, more precisely than direct differentiation, when jump discontinuities or gradient singularities come into the picture. The issue of gradient singularity can be found in tanks containing vertical/horizontal baffles. Findings The application of PDDO helps to obtain the velocity field with a high accuracy at each time step that leads to a suitable geometry updating for the procedure. Domain/boundary nodes are updated by using a second-order finite difference time algorithm. The method is applied to the solution of different examples including tanks with baffles. The accuracy of the method is scrutinized by comparing the numerical results with analytical, numerical and experimental results available in the literature. Originality/value Based on the investigations, PDDO can be considered a reliable and suitable approach to cope with sloshing problems in tanks. The paper paves the way to apply the method for a wider range of problems such as compressible fluid flow.

Researchers are increasingly turning to roadway traffic flow theory to propose effective solutions for challenges such as traffic congestion and low efficiency in waterway transportation. However, since roadway traffic flow theory was originally developed for highway transportation, its direct application to waterways raises questions due to the inherent differences between the two modes of transportation. Meanwhile, research results and methodologies from other transportation modes can provide valuable insights for studying waterway traffic flow theory. Addressing these questions is essential for advancing research in this field. This research conducts a comparative analysis to explore the similarities and differences between typical transportation modes and waterway transportation, examining how these distinctions affect the application of existing traffic flow theories. It also categorizes recent research outcomes related to traffic flow theories from various transportation modes based on their relevance to waterway traffic flow theory. The discussion includes the applicability of these models and methods in the context of waterway transportation, considering the unique characteristics of waterway traffic. Finally, this study highlights current challenges in applying traffic flow theories to waterways and offers suggestions for future research.

The deployment of floating offshore wind turbines (FOWTs) in deep, typhoon-prone waters like the South China Sea requires platforms with exceptional stability. However, the performance validation of novel Tension Leg Platform (TLP) concepts under such extreme metocean conditions remains a significant research gap. This study addresses this by numerically evaluating a novel TLP design, including a regular hexagonal topology, a unique bracing structure and heave plates, and an increased ballast-tank height. A coupled numerical framework, integrating potential-flow theory and blade element momentum (BEM) theory within ANSYS-AQWA (2023), was established to simulate the TLP’s dynamic response to combined irregular wave, current, and turbulent wind loads. The resulting time-series data were analyzed using the Continuous Wavelet Transform (CWT) to investigate non-stationary dynamics and capture transient peak loads critical for fatigue sizing, which demonstrated the platform’s superior stability. Under a significant wave height of 11.4 m, the platform’s maximum heave was limited to 0.86 m and its maximum pitch did not exceed 0.3 degrees. Crucially, the maximum tension in the tendons remained below 22% of their minimum breaking load. The primary contribution of this work is the quantitative validation of a novel TLP design’s resilience in an understudied, harsh deep-water environment, confirming the feasibility of the concept and presenting a viable pathway for FOWT deployment in challenging offshore regions.