CFD Letters

CFD Analysis of the Choledynamic Flow Characteristics of a Patient with Gallbladder Carcinoma

Francis Dominic Lavilles — 2024-11-30

Gallbladder carcinoma (GBC) is a rare malignancy with a low detection rate due to non-specific symptoms, complicating early diagnosis and treatment. This study aims to improve pre-operative and post-operative surgical analysis using patient-specific CFD analysis. CT scan images of a male patient with GBC were segmented using 3D Slicer software, and the biliary tree geometry was imported into ANSYS Workbench for fluid and solid meshing. The mechanical properties of the biliary tree and the rheological properties of bile were determined, with an LRN k-ω model used for simulating the gallbladder refilling stage. Results indicate that unhealthy bile flows slower than healthy bile, suggesting a link between obstructed bile flow and tumors or stones. Tumor-induced blockages cause pressure accumulation in the gallbladder neck, unlike the minimum pressure in healthy cases. These findings highlight the complex interplay between bile rheology, tumor development, and pressure dynamics, suggesting the model’s potential use in surgical planning.

U-Turn Shape Effect on Effective Thermal Conductivity of Double Pass Photovoltaic Thermal (PVT) Systems Configuration

Ahmad Rajani — 2024-11-30

This study explores the thermal performance of double-pass photovoltaic thermal (PVT) systems by investigating the influence of turn shape on heat transfer characteristics using computational fluid dynamics (CFD) simulations. The aim is to evaluate various turn shapes, including half-circle, triangle, half-hexagon, half-octagon, and box, to determine their impact on turbulent intensity, effective thermal conductivity, and outlet temperature in PVT systems. The investigation reveals significant variations in heat transfer efficiency among the different turn shapes, with the triangle-shaped turn demonstrating superior performance across multiple parameters. The findings highlight that the triangle-shaped turn exhibits enhanced turbulence generation and heat exchange efficiency compared to other shapes. Specifically, the triangle-shaped turn achieves a maximum turbulent intensity of approximately 70%, surpassing other shapes which achieve around 60%. Moreover, the triangle-shaped turn displays a longer and more substantial area of high heat exchange, resulting in an effective thermal conductivity improvement of up to 20% compared to alternative shapes. Furthermore, the analysis indicates that the triangle-shaped turn exhibits a faster increase in outlet temperature, reaching steady-state conditions within 15 seconds, while other shapes require up to 19 seconds. These results underscore the significance of turn shape in optimizing the thermal efficiency of PVT systems.

Aerodynamic Drag Reduction using a Conduit in the Ahmed Body

Amine Agriss — 2024-11-30

In this study, the focal challenge is reducing drag around the Ahmed body, a critical concern in aerodynamics. The approach involves perforating a rectangular conduit inside the body, redirecting part of the airflow from the front to the rear end to minimize drag. Using Ansys Fluent CFD software and the SST k-w turbulence model, a numerical model for turbulent flow around a 3D body has been developed. Through a series of numerical simulations, variations in the conduit’s position relative to the lowest slanted edge of the body have been explored. At the optimal position with the lowest drag, an examination has been conducted on the narrowing of the conduit outlet dimensions. Results indicate that, with a suitable conduit position and an appropriate exit narrowing, a decrease in drag of up to 3% could be achieved. Ongoing work involves the examination of the conduit’s tilt at the outlet to determine the optimal arrangement for further drag reduction. This research offers practical insights for drag reduction and contributes to the broader field of aerodynamics.

Numerical Investigation of Underwater Vehicle Maneuvering under Static Drift Conditions

Muhammad Sajjad Ahmad — 2024-11-30

The hydrodynamic behavior of underwater vehicles is crucial for achieving optimal maneuverability and energy efficiency in various underwater environments, thereby ensuring effective underwater operations. This research addresses the drift characteristics of an underwater vehicle by conducting Computational Fluid Dynamics (CFD) simulations. DARPA Suboff model was used to analyze its maneuvering characteristics under static drift conditions at a velocity of 3.34 m/s and drift angles ranging from 0 to 18 degrees with 2-degree intervals. The simulations replicate actual sea conditions using the Reynolds-Averaged Navier-Stokes (RANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. The computational domain and boundary conditions are carefully defined to optimize the computational cost. The results revealed a significant decrease in longitudinal force when the drift angle increased, while the lateral force and yaw moment showed substantial increases, indicating the complex interactions between drift angles and hydrodynamic performance. This research provides valuable insights into the hydrodynamic forces and moments acting on underwater vehicles, contributing to their design optimization for improved stability and efficiency.

Numerical Model Parameters Impact on Savonius Wind Rotor Performance

Mariem Lajnef — 2024-11-30

Global greenhouse gas emissions are mostly caused by the production of energy extracted from fossil fuels sources. Indeed, the use of renewable clean energy has become crucial to supply the world demand while protecting the planet. For many years, there has been a great deal of interest in wind energy because it is a clean, sustainable energy source. Because of its cheaper cost and independence from wind direction, the Savonius vertical axis wind rotor has the advantage of being suitable for certain implementations as an energy converter. Several studies have been carried out to increase its efficiency from this angle. This research work emphasizes on the Savonius wind rotor numerical model performances. The main goal is to explore the impact of setting the numerical model parameters on its aerodynamic and performance characteristics. Ansys Fluent software 17.0 was utilized to perform numerical simulations utilizing the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. The mesh sizing, the turbulence model as well as the time step parameters were investigated. The numerical model validation was realized through published experimental findings available in the literature for an inlet wind velocity of 6 ms^-1. Good accordance was obtained. Thus the numerical model with the selected parameters was relevant for further investigations. For a tip speed ratio λ=0.64 it gave a torque and power coefficients equal to 0.328 and 0.2, respectively.

Numerical and Experimental Validation of a New Methodology for the Design of Michel-Banki Turbine

Steven Galvis Holguin — 2024-11-30

Michell-Banki cross-flow turbines (MBT) are low-cost turbines that are easy to manufacture and maintain, which makes them ideal for implementation in small-scale hydroelectric projects. Although the MBT has lower efficiencies than turbines such as the Pelton and Francis, it maintains its efficiency stable in the face of fluctuations in flow conditions. The objective of this study is to validate, both numerically and experimentally, a new design methodology that allows the construction of an MBT based on site conditions. For this purpose, the design of the different components of an MBT was implemented according to the site conditions. The experimentation was carried out in a hydraulic test bench, which consists of a water tank, a centrifugal pump, a piping system, a PMAG SGM LEKTRA magnetic flow meter, a TRS605 FUTEK torque sensor, a pressure gauge, and a model of MBT designed and manufactured from scratch. It was concluded that the proposed methodology allows for obtaining experimental and numerical efficiencies of and, respectively. Thus, a numerical-experimental validation of the MBT design and manufacturing methodology could be carried out.

CFD Investigation of Toluene Emission in a Printing Room

Ahmad Amirul Aiman Mohd Khalid — 2024-11-30

Volatile organic compounds (VOCs) comprise several harmful chemical such as benzene and toluene, that can cause acute and chronic health effects for individuals. One of contributors of VOC are printers, photocopiers, and fax machine that use ink that when it is heated during printing operations will emit VOC. Printing shops heavily operate these devices (machines) and often several of them at the same time and this will cause the VOC level inside the premises to be higher compared to home and offices that have similar equipment. This study estimates the VOC, particularly toluene, concentration, and distribution inside a printing room, by using Computer Fluid Dynamic (CFD) analysis approach software. The software aid in physical modelling of the emission flow based on copiers machine numbers and influence of parameters like concentration levels and anthropometric data. Despite implementing ventilation and at a minimum number of operating copiers, the study reveals that toluene emissions exceed the recommended limit, particularly among females who have higher exposure than males due to height. The quantity of copiers and the positioning influenced the dispersion of toluene in the investigated area.

CFD Analysis into the Breakdown of Catamaran Resistance Based on the Original Formula by Insel and Molland

Amalia Ika Wulandari — 2024-11-30

Over the last 40 years, the use of fast catamaran has progressively developed attributed to its unique characteristics on resistance and seakeeping. The advantages have also been applied to military vessels to gain both resistance and seakeeping benefits. The current study focuses on the resistance of catamaran warships to provide less resistance, therefore, the size of engine and emission of toxic gases to the atmosphere. The total resistance of a catamaran will be different from a monohull of equal displacement. There are several factors including viscous interference factors such as φ, which is introduced to take account of the pressure field change around the hull, σ takes account of the velocity augmentation between the two hulls and calculated from an integration of local frictional resistance over the wetted surface, and τ is the wave resistance interference factor change. Those resistance components were developed by Insel and Molland in the 1990s. The investigation discusses the derivation of those components numerically using Computational Fluid Dynamics (CFD) approach. The speeds (hence, the Froude numbers) are varied from 0.2 to 0.6 and the separations between the hulls (S/L) are made between 0.2 and 0.4 so the comparative purposes can be done against the classical work of Insel and Molland and other published data.

Numerical Comparison of Three Rotors For Gravitational Water Vortex Turbine

Alejandro Ruiz Sánchez — 2024-11-30

Renewable energy sources have gained significant attention due to the increasing demand for clean energy production. The gravitational vortex turbine (GVT) is one of the emerging technologies in the field of renewable energy that has gained attention for its simple and low-cost manufacturing process. The turbine operates by utilizing the energy of wastewater or other liquid flows to generate power on-site, making it a potentially viable solution for small-scale power generation. However, the optimization of the turbine's design is necessary to improve its efficiency and to make it a more competitive source of renewable energy. Previous research on GVT has mainly focused on the chamber's design to improve the formation of the vortex. However, little attention has been paid to the rotor design, which is also a critical parameter affecting the turbine's performance. The current study aimed to investigate the performance of three different rotors for the turbine, including the Savonius, H-Darrieus, and a standard rotor with straight blades, using numerical simulations. The numerical simulations were performed using ANSYS software, with ICEM modules for discretization and CFX for simulation. The results showed that the straight-bladed rotor outperformed the other two rotors, with an increase in efficiency of 40% and 79% compared to the Savonius and H-Darrieus geometry blades, respectively. The study highlights the importance of considering the rotor design in the optimization of the gravitational vortex turbine. The results provide valuable insights into the design parameters that can be used to enhance the turbine's performance. These findings can contribute to the development of more efficient and cost-effective gravitational vortex turbines for on-site power generation and consumption.

Contribution of Soret and Dufour Aspects on Hybrid Nanofluid over 3D Magneto Radiative Stretching Surface with Chemical Reaction

Bhavanam Naga Lakshmi — 2024-11-30

This study analyzes Soret and Dufour impacts on 3-dimensional, rotating HNF (CuO-Ag/Water) flow over a linearly stretchable surface that contains a mixture of Ag and CuO nanoparticles with H₂O acting as the base fluid. Flow of governing PDEs is transformed into a system of ODEs, by using the bvp5c approach. Analysis and graphical presentation were made of the effect of the parameters included. The present study reveals that the Soret factor affects the surface's thermal efficiency whereas the Dufour impact lessens the surface mass transfer. The present work 99.9% compatible with previous work for stretching sheet parameter values are 0, 0.1, 0.2, 0.3, 0.4, 0.5. This conclusion may be employed in a variety of nanofluid cooling systems. This study may be used to inform future numerical and experimental studies.