Papers by Keyword: CFD

Abstract: This study investigates riparian vegetation as a mitigation measure for overflow and bank erosion in the Jumman Shah Canal, Pakistan, using Computational Fluid Dynamics (CFD) with the Volume of Fluid (VOF) method for free-surface flow simulation. Three cases were modeled: bare floodplain (existing condition), submerged vegetation, and emergent vegetation. Vegetation was represented as uniformly spaced cylinders to maintain consistent porosity, with a 1:100 geometric scale replicating prototype peak-flow conditions. Field velocity measurements validated the model, showing strong agreement with simulations. Results showed submerged vegetation induced moderate backwater effects and broader low-velocity zones, while emergent vegetation produced greater upstream water level rise, higher momentum attenuation, and a delayed, confined high-velocity core. Both vegetation types increased hydraulic resistance and improved flow uniformity compared to the bare channel, with emergent vegetation offering the highest flood energy dissipation. The findings advocate vegetation-based stabilization as a sustainable, cost-effective approach for enhancing canal resilience.

Abstract: This work numerically studies the water-in-oil (W/O) droplet formation inside a flow focusing on the micro junction formed by rectangular channels with dimensions of 390 × 190 μm² using OpenFoam. An automatic algorithm was developed to assess the effect of key parameters such as water viscosity, restriction ratio and water mass flow rate ratio on the droplet size. A total of 96 simulations, with different parameter combinations, were conducted to train a Machine Learning (ML) algorithm capable of predicting the droplet dimensions based on the key parameters mentioned. The ML algorithm was also compared to a Newtonian-based optimization method, where the geometry is iteratively adjusted to produce droplets of a fixed size. Results reveal that both methods appear valid in the prediction of droplet dimensions.

Abstract: Turbulent flow characteristics through a three-dimensional annular diffuser having a rectangular twisted hub RTH are investigated. The numerical analyses are performed to have more understanding of the physical behavior of the fluid flow. The numerical work is conducted using the RTH with three twist ratios (y/w = 0.6, 0.7, and 1) for a Reynolds number 128069. In the present study, the air is used as a working fluid. Computational Fluid Dynamics CFD, based on a finite volume method, is completed by utilizing the standard k-ε turbulence model. Velocity streamlines, velocity contours, and pressure contours plots are described to study the flow characteristics by utilizing different twist ratios (y\w). The analytical results reveal that RTH has a significant effect on the velocity and pressure characteristics. Findings show that the diffuser with the twist ratio (y\w = 0.6) produces more swirling and recirculation than (y\w = 0.7 and 1). Therefore, the RTH with a small twist ratio significantly enhances the distribution of the velocity and pressure because of the strong swirling generated through the flow.

Abstract: In this study, CFD simulations were conducted to investigate the optimal design parameters for the diffuser vane slit, which is one of the means to suppress diffuser rotating stall (DRS), in terms of slit width, height, and position, to maximize the DRS suppression effect while maintaining diffuser performance. The investigated pump is a centrifugal pump with a specific speed of Ns = 138 m³/min, m, rpm and the diffuser is an axial-flow type. The simple prediction method of DRS by CFD simulation used in the previous study was applied and evaluated in terms of the coefficient of variation C.V., static pressure recovery coefficient C_P, and total pressure loss coefficient C_T in the diffuser flow channel. As a result, it was found that the slit position was the best at 18% of the vane axial chord length regardless of the slit width, and that the slit height from the hub to the tip provided the best DRS suppression. A wider slit width increases the flow rate through the slit and enhances the DRS suppression effect, but it causes lower diffuser performance and results in a trade-off relationship. Therefore, the slit width should be set to an appropriate value depending on the required operating range.

Abstract: This study investigates the aerodynamic performance of the NACA 2412 airfoil using Computational Fluid Dynamics (CFD) to provide cost-effective and accurate alternatives to traditional wind tunnel testing. The research focuses on comparing the Shear Stress Transport (SST) and k-epsilon turbulence models to optimize airfoil designs for unmanned aerial vehicles (UAVs). The findings indicate that the SST model exhibits superior accuracy in predicting lift coefficients, while the k-epsilon model tends to yield conservative trends. Future research will aim to enhance mesh quality and calibrate turbulence models for improved predictions.

Abstract: Gas-liquid two phase flow of blast furnace taphole stream into the main trough is studied through computational fluid dynamics (CFD) method. Tapping process of blast furnace with different taphole angles is simulated by volume of fluid model of CFD. The velocity and region of taphole stream into flow within the main trough is analyzed. It is concluded that the tophole case with bigger angle is conducive to slag-metal separation in the main trough.

Abstract: Turbulence is a highly complex and challenging phenomenon to study, especially in the field of fluid dynamics, where many applications rely on accurate predictions of turbulent flow behavior. Due to its random and chaotic nature, turbulence is difficult to model precisely, but achieving reliable results is essential for solving numerous engineering problems. Various turbulence models, each with specific strengths and limitations, have been developed to address this challenge. This study focuses on comparing three widely used turbulence models (k−ϵ, k−ω, and the Reynolds Stress Model (RSM)) to evaluate their accuracy in simulating turbulent flow within a corrugated channel. The aim of this study is to simulate and achieve better result accuracy while minimizing computational cost in this geometry, both with and without vortex generators. The investigation begins with a trapezoidal channel, after which vortex generators are introduced to assess their impact on flow behavior. Vortex generators are known to enhance heat transfer by promoting flow separation and modifying the flow direction, making their effect critical in such simulations. The computational analysis is conducted using ANSYS Fluent, a commercial software for computational fluid dynamics (CFD) and heat transfer modeling, which operates on the finite volume method to ensure conservation of physical properties. Results will be presented through detailed graphical representations and contour plots, followed by a comprehensive discussion of the comparative performance of each model.

Abstract: The current research paper presents an investigation into the behavior of two-phase flow of liquid-vapour R134a within vertical circular channels with a 1 mm diameter, utilizing the Volume of Fluid (VOF) method. The main objective of these simulations was to create a numerical flow regime map to delineate the boundaries of different flow patterns for liquid-gas R134a. The injection of vapor was performed through an annular (concentric) nozzle configuration. To optimize computational efficiency, a two-dimensional axisymmetric assumption was made. The results of this study led to the identification of four fundamental flow patterns: bubbly flow/confined bubble flow, slug flow, churn flow, and annular flow. The accuracy of these findings was confirmed by comparing them with experimental flow visualization results, demonstrating a strong agreement. This study highlights the effectiveness of Computational Fluid Dynamics in establishing a reliable two-phase flow pattern map.

Abstract: The increasing demand for clean and renewable energy has led researchers to focus on the development of vertical-axis wind turbines. This paper aims to compare the flow field and performance of the Tornado wind turbine with those of Savonius, Darrieus, and hybrid wind turbines at different tip speed ratios. A two-dimensional, incompressible, turbulent, and unsteady flow model was created using ANSYS Fluent 21 and verified through grid independence studies. The Tornado wind turbine demonstrates enhanced aerodynamic efficiency and reduced negative torque. The results show that the Tornado model achieves a peak power coefficient at a TSR of around 1.1. The model's validity was confirmed by comparing simulation results with experimental data for the model TN-2000 VW4, indicating its potential for real-world applications.

Abstract: Source identification techniques can provide source parameters estimations when sudden releases occur or the origin of long-term emissions. These methodologies can be based on optimization techniques or statistical inference, in the framework of the inverse problems. In this work, we propose a methodology based on the minimization of the Tikhonov-type functional, which accounts for the discrepancy between the observed and calculated concentrations also considering information about the source parameters for estimation. This functional is minimized to provide the source parameters using the Particle Swarm Optimization technique. A non-standard k−ϵ model was applied to solve the forward problem. The flow simulation emulated the Cedval A1-1 single-building experiment and the concentration distribution for two scenarios was synthetically produced by simulation. The proposed methodology was effective in identifying the source locations.