CFD Letters

Numerical Simulation of Droplet Coalescence Using Meshless Radial Basis Function and Domain Decomposition Method

Eko Prasetya Budiana — 2024-10-31

The present investigation of the dynamic two-binary droplet interactions has gained attention since its use to expand and improve several numerical methods. Generally, its interactions are classified into coalescence, bouncing, reflective, and stretching separation. This study simulated droplet coalescence using the meshless radial basis function (RBF) method. These methods are used to solve the Navier-Stokes equations combined with the Cahn-Hilliard equations to track the interface between two fluids. This work uses the fractional step method to calculate the pressure-velocity coupling in the Navier-Stokes equations. The numerical results were compared with the available data in the literature to validate the proposed method. Based on the validation, the proposed method conforms well with the literature. To identify further coalescence characteristics, the model considered different values in viscosity (2, 4, and 8 cP), collision velocity (1.5 m/s and 3 m/s), and surface tension (0.014, 0.028, and 0.056 N/m) parameters. The increasing viscosity was linearly proportional to the collision time, whereas increased surface tension and collision velocity shortened the collision time.

Numerical Study on the Effect of Installing Circular Cylinders in Front of the Returning Blade and Beside the Advancing Blade of the Savonius Wind Turbine

Rusydi Furqon Syahrillah Gusti — 2024-10-31

Previous research has proven that placing a disruptive cylinder in front of the Savonius wind turbine’s returning blade can significantly increase the performance of the Savonius turbine. In this study, two-dimensional unsteady simulations with a quadratic pave-type structured mesh showed that the circular cylinder placed in front of the returning blade and next to the advancing blade provides the best performance results at a free flow speed of 5 m/s and a Reynolds number of 100,000. In this study, the comparison with experimental data from another study is utilized. The Savonius turbine is installed with an interfering cylinder in front of the returning blade and next to the advancing blade; the air is tighter on the concave side of the advancing blade. The coefficient pressure difference between the convex and concave sides of the blade increases. The maximum moment is achieved in the turbine with a disturbance cylinder at a configuration distance of S/D 1.4 – Y/D 1.61. The maximum moment coefficient is obtained at the position θ = 15°. The placement of two cylinders with a ratio variation of 0.5 D can significantly influence turbine performance. Results show the turbine provides the highest Power Coefficient when TSR = 0.6. The power coefficient increased by 25.11% compared with that of conventional Savonius turbines. Therefore, it can be concluded that the turbine is the optimal configuration for generating the highest power.

Unsteady MHD Rotating Jeffreys Fluid Flow Embedded in a Porous Medium Over an Infinite Perpendicular Plate

M. Harikrushna — 2024-10-31

The analysis of the rotation outcomes for the viscous, incompressible, electrically conducting Jeffreys fluid in an infinite vertical plate through the revolution impacts has been explored. This is owing to the exponential exciting perpendicular absorbent plate embedded in the permeable medium by allowing for ramped surface temperature into the endurances of thermal radiation. The essential governing sets of equations for the flow are translated into non-dimensional form with insert appropriate parameters as well as variables; therefore the resultant equations are computationally resolved by the well-organizing Laplace transform methodology. The influences of numerous significant considerable parameters for the modelling on the velocity, temperature and concentration of the liquid, and the skin friction coefficient, Nusselt number and Sherwood number for together thermal conditions have been deliberated and exploring strongly by producing of graphical profiles and tabular format. This is determined that, with increasing quantities of the rotation, thermal radiation parameters, the fluid temperature as well as velocity enhances. Similarly, this is notified that, a mounting in porous parameter reasons to escalate fluid velocity in addition to concentration reversal results are noticed by the chemical reaction parameter.

Exergy Efficiency and Energy Efficiency of Double Air Pass Solar Tunnel Air Dryer: A CFD Analysis

Dagim Kebede Gari — 2024-10-31

This work presents, the computational fluid dynamics simulation of a forced convection double air pass solar tunnel drying system to study the temperature distribution, the flow behaviour of the air stream, and the exergy performance. Realizable k-epsilon non-equilibrium wall function turbulence model, discrete ordinate radiation model, and species transport were used. The average temperature, thermal efficiency, and exergy efficiency were found to 59.2 ^oC, 30%, and 9.41%, respectively. The result revealed that the uniform temperature and velocity distribution throughout the heating and drying chamber. Therefore, the newly developed double air pass solar tunnel dryer enhances the air temperature and the exergy performance leads to the increment of drying rate and reduction of drying period.

Numerical Investigation on Photovoltaic Thermal Panel Using Various Nanofluids Concentrations

kai xiang Cheah — 2024-10-31

Increasing the efficiency of solar panels is crucial for effective use of renewables. The present numerical study deals with improving the performance of a PVT system with nanofluid using CFD FLUENT software. ZnO-water and SiO₂-water nanofluids are investigated and correlation are established between the PVT efficiency and various nanofluid volumetric concentrations ranging from 1% to 10%. Validation of the present results is verified by comparison with experimental data. Comprehensive research is conducted to evaluate the correlation between the thermophysical properties of nanofluids such as density, thermal conductivity, specific heat capacity and dynamic viscosity. The results demonstrate that the overall efficiency of the ZnO-water nanofluid and -water nanofluid increases by 0.44% and 0.24%, respectively, as the volumetric concentration of the nanofluid rises from 1% to 10%. The ZnO-water nanofluid reveals enhanced thermal and electrical efficiency compared to the -water nanofluid due to its superior thermal conductivity and enhanced heat transfer capabilities along the absorber tube. The ZnO-water nanofluid exhibits a greater heat transfer coefficient, thereby facilitating the cooling mechanism of the PV panel and reducing the PV cell temperature, hence enhancing power generation.

Computational Prediction of Co-firing with Various Biomass Waste Using Turbulent Non-Premixed Combustion

Agus Nuryadi — 2024-10-31

Co-firing in coal power plants has limitations because the existing combustion systems are designed to provide optimal performance only with coal. Therefore, investigating the combustion aspects of co-firing by mixing coal with biomass before applying it to existing coal power plants is necessary. To address this, a new numerical model was developed to predict the co-firing behavior of coal with various types of biomass waste, specifically focusing on temperature and pollutant behavior. This study developed a co-firing model in a Drop Tube Furnace (DTF) using a composition of 25% Wood Chips (WC), 25% Solid Recovered Fuel (SRF), 25% Empty Fruit Bunch Fibers (EFFR), and 25% Rice Husk (RH). A structured grid arrangement and the Probability Density Function (PDF) were utilized to depict the relationship between chemical combustion and turbulence. The distributions of temperature and mass fractions of pollutants along the furnace axis were predicted. The highest temperature was observed with 25% EFFR, attributed to its highest volatile matter content. The simulation predicted that 25% RH would be the lowest SO₂ emitter. However, it also showed a slight increase in NO and CO levels due to the increased oxygen content when coal was mixed with biomass. The simulation with 25% EFFR predicted a decrease in CO₂ emissions compared to other biomass types. The results of this parametric investigation could support the implementation of biomass co-firing technology in existing coal-fired power plants.

Computational Fluid Dynamics (CFD) Evaluation of a Horizontal-axis Wind Turbine with a Bionic Blade

Russel Tapa Musa — 2024-10-31

With the world's energy supply becoming increasingly scarce, wind power is gaining popularity as a clean source of renewable energy which is good for the environment. Thus, it is an alternative to burning fossil fuels such as coal, which may have an environmental impact during operations due to the emissions of unwanted gases. Wind turbines are the devices used to produce power by moving a turbine's propeller-like blades around a rotor, which spins a generator that generates energy as air passes through them. However, existing wind turbines still suffer from low conversion efficiencies. Therefore, in this current study, the bionic blade design has been used to enhance the performance of a horizontal axis wind turbine utilizing a computational simulation approach while seeking to improve its efficiency. The blade profile of the model used was based on the NACA 0012 airfoil with the modified angle of attack. The hybrid shear stress transport (SST) k-omega was used as the turbulence model. The computational procedures involved the use of various inlet velocities while maintaining a constant rotational speed. The results show that the bionic design was found to improve the overall performance of the standard NACA0012 blade design. Moreover, both power and torque coefficient outputs increase as the tip speed ratio (TSR) increases. However, the torque decreases as the TSR increases. In terms of power coefficient, the highest conversion efficiency was about 28% and it was achieved at 3.7 TSR.

Effect of Water-based Alumina-Copper MHD Hybrid Nanofluid on a Power-Law Form Stretching/Shrinking Sheet with Joule Heating and Slip condition: Dual Solutions Study

adnan asghar — 2024-10-31

The application of hybrid nanofluid is now being employed to augment the efficiency of heat transfer rates. A numerical study was conducted to investigate the flow characteristics of water-based-alumina copper hybrid nanofluids towards a power-law form stretching/shrinking sheet. This study also considered the influence of magnetic, Joule heating, and thermal slip parameters. This study is significant because it advances our understanding of hybrid nanofluids in the presence of magnetic fields, power-law form stretching/shrinking sheet, and heat transfer mechanisms, providing valuable insights for optimizing and innovating thermal management systems in various industrial applications such as polymers, biological fluids, and manufacturing processes like extrusion, plastic and metal forming, and coating processes. The main objective of this study is to examine the impact of specific attributes, including suction and thermal slip parameters on temperature and velocity profiles. In addition, this exploration examined the reduced skin friction and reduced heat transfer in relation to the solid volume fraction copper and magnetic effects on shrinkage sheet and thermal slip parameter on suction effect. To facilitate the conversion of a nonlinear partial differential equation into a collection of ordinary differential equations, it is necessary to incorporate suitable similarity variables into the transformation procedure. The MATLAB bvp4c solver application is utilized in the conclusion process to solve ordinary differential equations. No solution was found in the sort of when , and . As the intensity of the Eckert number increases, the temperature profile and boundary layer thickness also increase. The reduced heat transfer rate upsurged in both solutions for solid volume fraction copper for shrinking sheet, while the opposite actions can be noticed in both solutions for thermal slip parameter for suction effect. Finally, the study conducted an analysis to identify two distinct solutions for shrinking sheet and suction zone, while considering different parameter values for the copper volume fractions, magnetic and thermal slip condition effect.

Meteotsunami Impact in Indonesia Due to the Shockwave of the Hunga Tonga Volcanic Eruption on January 15, 2022

Januar Arifin — 2024-10-31

This paper presents the impact of a meteotsunami resulting from the shockwave of the underwater volcanic eruption of Hunga Tonga–Hunga Ha'apai (HTHH) on January 15, 2022.The tsunami was detected in various locations in Indonesia through a network of water level sensors monitored by the Meteorology, Climatology, and Geophysics Agency (BMKG). The tsunami wave heights varied significantly and exhibited a non-linear relationship with the distance from the volcano. The heights of detected tsunami ranged from 2.8 to 22.6 cm, with the highest recorded at the water level sensor south of Java Island. The heights of waves are believed influenced by Proudman resonance in the Indian Ocean waters beside the local amplification effect. The average period of the tsunami waves was approximately 40 minutes, exceeding five days. The tsunami was triggered by the coupling effect between the shockwave with a velocity of 312 m/s and the sea surface. The air pressure anomalies due to the shockwave ranging from 1.2 to 2.2 hPa. Throughout Indonesian waters, this meteotsunami phenomenon did not have a significant impact.

Numerical Solution of Burgers Equation Using Finite Difference Methods: Analysis of Shock Waves in Aircraft Dynamics

Hashim Abada — 2024-10-31

In this research, the Lax, the Upwind, and the MacCormack finite difference methods are applied to the experimental solving of the one-dimensional (1D) unsteady Burger's Equation, a Hyperbolic Partial Differential Equation. These three numerical analysis-solving methods are implemented for accurate modeling of shock wave behavior high-speed flows that are necessary for aerospace engineering design. This research analysis proves that the MacCormack technique is the one that treats the differential equations with second-order accuracy. This method is quite preferred when it comes to numerical simulations because of its advanced level of accuracy. Although the Upwind and Lax methods are slightly less accurate, they show the development of shock waves that give visualizations to better understand the flow dynamics. Also, in this study, the impact of varying viscosity coefficients on fluid flow characteristics by using the lax (a numerical method for solving the viscous Burgers equation) is investigated. This identification of the phenomenon sheds light on the behavior of boundary layers, which, in turn, can be used to improve the design of high-speed vehicles and lead to a greater understanding of the area of fluid dynamics.