Progress in Computational Fluid Dynamics, An International Journal (17 papers in press)

Regular Issues

• Dynamic Simulation of Centrifugal Compressor System Based on the Semi-Mechanism Modelling  
  by Xuejiang Chen, Zhijie Jia, Yang Su, Mingshun Yan 
  Abstract: There are many transient changes in the operation of the centrifugal compressor system, so it is very important to study the dynamic characteristics of the centrifugal compressor system. In this study, a semi-mechanism dynamic simulation method based on the Greitzer model is proposed to study the dynamic characteristics of centrifugal compressor systems. The steady-state performance curves of the compressor and valve are obtained through CFD simulation. Using the established simulation model in Matlab/Simulink, the dynamic characteristics of the compressor system's outlet pressure under typical working conditions were analysed. Furthermore, typical surge phenomena are simulated, revealing a main vibration frequency of approximately 4 Hz in the inlet pressure, outlet pressure, and mass flow rate. This semi-mechanism simulation model demonstrates high reliability and can replace complex transient testing processes, offering a novel approach for studying the dynamic characteristics of centrifugal compressor systems.
  Keywords: Compressor; dynamic modeling; CFD; compressor surge.
  DOI: 10.1504/PCFD.2024.10067927
   
  
• Numerical and Statistical Analysis of the Influence of a Stern Wedge on Running Attitudes of Non-Stepped and Stepped Hulls  
  by Mohammad Sheikholeslami, Parviz Ghadimi, Farzan Kiani 
  Abstract: The effects of a stern wedge on the running attitudes of a baseline and stepped planing hull are hereby investigated. Four planing models including the baseline, wedge-mounted, stepped, and wedge-mounted stepped are simulated and the linearity of the total drag with speed is statistically analysed. This study demonstrates that the stern wedge reduces the trim angle by up to 37% in the baseline model and 41% in the stepped model. It increases friction drag by 20% in the baseline and 15% in the stepped model, while its impact on total and pressure drag is similar for both. The only running attitude of these two models that is differently affected by the stern wedge is the rise-up. Statistical analysis indicates that limiting the model to the planing regime and excluding data taken from the displacement and semi-planing regimes, can make the linear model more reliable.
  Keywords: planing hull; transverse step; stern wedge; drag components; cougar; statistical analysis.
  DOI: 10.1504/PCFD.2024.10068075
   
  
• Flow Control around a Square Cylinder Using the Flexible Plate  
  by Xiangdong Deng 
  Abstract: This paper explores the flow control mechanism of a flexible plate at the trailing edge of a square cylinder using the immersed boundary finite element-finite difference method (IFED). The flexible plate and the background flow field are simulated using the finite element method and finite difference method, respectively, with a Lagrangian-Eulerian coupling operator for joint mesh resolution. Parameter analysis and mechanism research are performed on plates with varying elastic moduli at Re = 200. Results indicate that a rigid plate reduces mean drag but increases lift fluctuations. Conversely, the flexible plate mitigates these lift fluctuations, making it a superior passive flow control method. The control mechanism involves preventing shear layer contact on both sides and enlarging the wake vortex street spacing, thus reducing the pressure difference both vertically and horizontally around the square cylinder structure.
  Keywords: Flow control; Immersed boundary method; Fluid-Structure Interaction.
  DOI: 10.1504/PCFD.2024.10068329
   
  
• Streamlining Fluid Flow: Injection Slot Optimisation for Coflow Jet Airfoil  
  by Cm Vigneswaran, Inamul Hasan, Srinath R, Somashekar V 
  Abstract: This research explores the strategic optimisation of injection slot placement on a NACA 0018 co-flow jet (CFJ) airfoil, to enhance aerodynamic efficiency while mitigating energy consumption. The precise location of the injection slot is pivotal, as it governs the effectiveness of boundary layer control, augmenting lift and delaying separation, while simultaneously influencing the power demands of the CFJ system's pump. A comprehensive computational analysis is conducted using a pressure-based solver, resolving the Reynolds-Averaged Navier-Stokes (RANS) equations for two-dimensional, incompressible flow. The simulations are performed under sea-level boundary conditions, with a Mach number of 0.1 and a Reynolds number of 0.65 million, utilising the Spalart-Allmaras turbulence model. The results demonstrate that optimal injection slot placement enhances the lift coefficient (CL) by up to 30.1% while concurrently reducing power consumption. This research articulates a refined aerodynamic optimisation framework for CFJ systems, advancing both lift and energy efficiency for broader aviation applications.
  Keywords: Aerodynamics; Flow control; Boundary layer; Lift; Drag; CFJ airfoil.
  DOI: 10.1504/PCFD.2024.10068365
   
  
• Comparative Study of Flow past a Square Cylinder using Three Viscous Schemes for Vortex Method in Laminar Conditions  
  by Golnesa Karimizindashti, Ozgur Kurc 
  Abstract: Numerical simulations of two-dimensional flow passing a stationary square cylinder for moderate Reynolds numbers (Re = 200, 500, 1000) are performed using a mesh-free method, the Discrete Vortex Method (DVM). To simulate the vorticity gradient, three diffusion schemes, Random Walk, Particle Strength Exchange, and Vorticity Redistribution methods, are utilised. The results are compared against each other and previous numerical and experimental studies. These results are presented in terms of RMS lift and mean drag coefficients, Strouhal number, and base pressure coefficient. Also presented are the wake characteristics, as well as the mean and fluctuations of pressure distribution around the body surface. All cases are in reasonable agreement with the literature, although the simulations with the Vorticity Redistribution method tend to underestimate these parameters. To the best of the authors' knowledge, this is the first comprehensive comparison carried out of the DVM-based diffusion schemes.
  Keywords: discrete vortex method; diffusion; square cylinders; unsteady flow; incompressible flow; two-dimensional flow; CFD; computational fluid dynamics; mesh-free methods.
  DOI: 10.1504/PCFD.2024.10069031
   
  
• SuperElliptical Wing Platforms for Induced Drag Reduction  
  by Daniel Raymer, Kurtulus Dilek Funda, Berkan An?l?r, Alexis Lapouille, Mathieu Passe, Louis Le Strat, Sina Golshany, Chris Holtorf, Charles Peot 
  Abstract: A parametric CFD investigation into SuperElliptical Wing Planforms is presented. By defining a wing planform using a superellipse with exponent slightly greater than two, it was speculated that a more-elliptical lift distribution may be obtained that from an actual elliptical wing, resulting in a reduction in induced drag. CFD analysis by three organizations seems to confirm this speculation and points to a superellipse exponent of 2.3 as offering the lowest drag. The slight weight increase for this superelliptical planform wing is approximated using standard quasi-empirical equations. Comments are made about accuracy of results and a compari-son to a previous wing optimization study. The use of superellipse mathematics to define smooth crescent wings is also presented.
  Keywords: Elliptical wing; Oswald’s efficiency factor; Computational Fluid Dynamics.
  DOI: 10.1504/PCFD.2024.10069140
   
  
• Hydrodynamic Effects of Strut on 3D Hydrofoils Near Free Surface in Cavitating and Non-Cavitating Conditions at Various Velocities and Angles of Attack  
  by Aliakbar Ghadimi, Hassan Ghassemi, Parviz Ghadimi, Alireza Pourmansour 
  Abstract: Hydrofoils are connected to vessels through geometrically complex struts to reduce resistance while maintaining vessel performance. This study explores the effects of various factors, including the presence of struts, on the hydrodynamic behavior of hydrofoils near free surface under both cavitating and non-cavitating conditions. Using the RANS solver and VOF model in StarCCM+ software with the Saur model for cavitation, the performance of two 3D hydrofoil cross-sections, NACA0012 (symmetric) and NACA6612 (asymmetric), was analyzed. Simulations indicate that the lift-to-drag ratio decreases with increasing angles of attack and immersion ratios for both hydrofoil types, though asymmetric hydrofoils consistently achieve higher lift-to-drag ratios than symmetric ones. Additionally, the inclusion of a strut significantly enhances the lift-to-drag ratio in both cavitating and non-cavitating conditions, with the asymmetric NACA6612 showing superior performance compared to the symmetric NACA0012.
  Keywords: Hydrodynamic performance; Hydrofoils; Strut; NACA6612; NACA0012; Cavitation; Numerical simulation.
  DOI: 10.1504/PCFD.2025.10069237
   
  
• Reduced Frequency Effect on Longitudinal Stability Derivatives Prediction of a Rectangular Wing by Using High Fidelity Computational Method  
  by Novita Atmasari, Mochammad Agoes Moelyadi 
  Abstract: This research utilises high-fidelity computational methods to analyse the reduced frequency effect in predicting the dynamic stability derivatives, revealing critical insights into aerodynamic performance. The rectangular wing is analysed through the simulation of three oscillatory motion relative to the freestream, specifically plunging, pitching, and flapping. This study applies a CFD-based transient simulation method that is capable of simulating unsteady flow around complex geometries, which acts as a bridge between the shortcomings of analytical methods with low accuracy and experimental methods with high costs. Unsteady flow simulation is solved by the time-dependent RANS and SST governing equations. Aerodynamic force and moment resulting from the simulations are then processed and analysed using Fourier Series approach to obtain the stability derivatives. For comparison, simulations were carried out using other methods, Datcom and XFLR5. The stability derivatives with low reduced frequency are show good agreement to Datcom and XFLR5 compared to high reduced frequency.
  Keywords: stability derivatives; unsteady simulation; reduced frequency; CFD; sinusoidal motion; Fourier.
  DOI: 10.1504/PCFD.2024.10069265
   
  
• Computational Study of Shock Tube using Baffle to Enhance the Performance for Biomedical Application  
  by Zeyaullah Ansari, Koushik Das, Ramesh Babu Pallekonda 
  Abstract: A shock tube is a pressure vessel commonly used to study the flow dynamics of a shock wave. The present work focuses on enhancing shock tube performance for needleless drug delivery by incorporating a baffle. A two-dimensional axis-symmetry shock tube with a converged opening of a baffle is modelled using ANSYS Fluent 2020 to improve the reflected shock pressure. A detailed parametric study of the system has been performed using different geometrical and physical parameters. The proposed modification in the shock tube improves performance with reduced initial driver pressure, to obtain a particular microjet velocity. It is desirable to use a baffle with higher inlet and lower outlet openings placed closest to the end wall of the driven section for better performance. The helium outperforms nitrogen as a driver gas to yield 2.17 times higher reflected pressure and enables a reduction of 66% in the initial driver pressure.
  Keywords: Shock tube; Baffle; Shock wave; Needle-less drug delivery; Compressible flow.
  DOI: 10.1504/PCFD.2024.10069269
   
  
• Comparing Single vs. Two-Phase Models for Al2O3-H2O Nanofluid in Minichannels  
  by Abdelkader Mahammedi, Driss Meddah Medjahed, Abderrahmane Amari 
  Abstract: CFD predictions of a steady laminar forced convective heat transfer of a nanofluid ?AL?_2 O_3-water mixture in a horizontal 2D minichannel was studied numerically. The governing equations for the classical Newtonian nanofluid and the approach founded on the two-phase models had been numerically solved using fluent cfd Software. The impacts of the Nusselt number, volume concentration, coefficient of heat transfer, Wall temperature, pressure drop also hydrodynamic flow were studied via single-phase fluid and two-phase (Eulerian, Mixture) models. A numerical process comparison with available numerical and experimental data was done to ensure the validity and reliability of the models, where a satisfactory agreement was found. Heat transfer efficiency raises as the nanoparticle volume concentration and Reynolds number rise, and the results of two-phase modeling demonstrate a larger enhancement of heat transfer compared to those from a single phase model.
  Keywords: CFD predictions Nanofluid Two-phase model Laminar forced convection Heat transfer.
  DOI: 10.1504/PCFD.2025.10069525
   
  
• Computational Fluid Dynamics-Based Analysis of Seepage Flow Through Concrete Dam  
  by Biri Singh, Anubhav Rawat 
  Abstract: Seepage is an essential aspect of dam structural study. Finite element method (FEM) based models have so far been used to predict seepage behaviour under dams. In the current work, Finite Volume method (FVM) based computational fluid dynamic (CFD) is employed in a novel way because FVM is frequently more computationally efficient for solving the flow problems. The CFD model used in the current work could accurately capture the physics of seepage under concrete dams. A detailed parametric investigation is carried out to establish seepage flow analysis through the dam. The dam's depth and width are inversely proportional to the seepage rate, and seepage velocity varies linearly with the water level head. Further, sand layer arrangements of different porosities are made in the dam at various locations to judge the effect of porosity arrangement on seepage. Analysis of grout curtain width is also done at different positions and angles in the dam. It is found that the upstream side location of the dam is best suited for grout curtains for minimum seepage.
  Keywords: Seepage flow; CFD; Concrete dam; Sand porosity; Grout curtain.
  DOI: 10.1504/PCFD.2025.10069857
   
  
• Effects of Trailing Edge Design on Flow around a Two-Element Airfoil Placed near a Wall  
  by Dilip Lalchand Parmar, Deepak Kumar Singh, Arjun Sharma 
  Abstract: Effects of presence of a wall on aerodynamics of two-element airfoils are studied at Reynolds number of 50000, angle of attack of 5 degrees and varying flap overlap. The primary geometry of airfoil has NACA0012 section as the main element along with a slotted flap. A second geometry for the main element is obtained by local modifications, in the form of downward tilt at the trailing edge and shaping of overlap region. Lift coefficients increase significantly with reduction in wall-distance for both geometries. Geometric modifications at the trailing edge of main element cause higher pressure due to flow blocking on the lower side as well as higher exit speed with flow alignment along the flap surface on the upper side. Improvements in lift coefficients due to geometric changes vary from 7% to 11% when the wall-distance decreases from 1 to 0.15 times the chord length of main element.
  Keywords: High-lift system; two-element airfoil; ground effects; shape modifications; adjoint-based gradient.
  DOI: 10.1504/PCFD.2025.10070014
   
  
• Non-Dimensional Parametric Optimisation of Hydraulic Performance of Centrifugal Pump using Response Surface Analysis  
  by Durvesh Yadav, Raj Singh, Manjunath K. 
  Abstract: In this study, the hydraulic performance of a single-stage centrifugal pump at the rated point was enhanced using the response surface methodology (RSM). By establishing an approximate relationship between the design head coefficient and flow coefficient, key geometric variables such as the number of blades, flow rate, and rotation were selected as decision variables. The head and flow coefficients were considered as responses. Utilising a central composite design (CCD) and computational fluid dynamics (CFD) in Design-Expert software, optimised impeller designs were evaluated. Experimental validation through 20 tests showed an average error of 6.21% for head, 5.77% for efficiency, and 7.13% for output power. The optimised pump model, featuring 7 blades, operating at 1,900 rpm, and delivering 450 m
  Keywords: Optimization technique; Response Surface Methodology; Computational fluid dynamics; number of impeller blades; rotation; Single-stage centrifugal pump.
  DOI: 10.1504/PCFD.2025.10070078
   
  
• Prediction of Pressure Gradient in Gas Liquid Flow based on Meta-Learning Methods  
  by Zhenzhen Dong, Zhanrong Yang, Weirong Li, Xiaowei Zhang, Wei Guo, Tong Hou, Guoqing Dong 
  Abstract: Gas-liquid two-phase flow models in wellbores are crucial across various stages of the petroleum industry. Accurate pressure drop prediction in these flows is vital for optimal production schedules. Traditional models face challenges such as uncertain prediction boundaries and complex parameter computations, lacking universal applicability. Leveraging advances in machine learning, this paper introduces a predictive model for pressure gradients in gas-liquid two-phase flow. Utilising 862 datasets from experimental literature, the data were pre-processed, cleaned, and split into training and validation sets. Employing RR2 and RMSE as evaluation metrics, the optimal model was identified using meta-learning, combining decision tree, random forest, K-nearest neighbours, XGBoost and LightGBM as base models, with XGBoost as the meta-model. The model achieved an R2 of 0.9826 and RMSE of 2.8200, highlighting key factors influencing gas liquid flow and emphasising the models accuracy and significance.
  Keywords: Pressure Gradient; Gas-liquid two-phase flow; Machine learning; Meta-learning.
  DOI: 10.1504/PCFD.2025.10071218
   
  
• A Study of Simultaneous Pitching and Plunging Motions of an Airfoil using the Spectral Element Method  
  by J. Gilberto Montiel-Galindo, Ruben Avila, Syed Shoaib-Raza 
  Abstract: In this study, the thermal convection of the laminar flow over a symmetric NACA 0012 airfoil with simultaneous pitching and plunging motions is presented. The non-steady, two dimensional, Navier-Stokes equations coupled with the energy equation, considering the Boussinesq approximation, are numerically solved by using the spectral element method. The influence of the Rayleigh number (the magnitude of the buoyancy force) on the aerodynamic coefficients and the Nusselt number (the heat transfer rate), is analyzed. It is found, for a given value of the Reynolds number (Re = 1000), that an increase of the buoyancy force leads to a decrease of the performance, although increasing the mean geometric angle of attack, ?m, reduces this effect. Moreover, we note that if ?m = 0?, the heat transfer is reduced as the buoyancy force increases; however, if ?m ? 10?, as the buoyancy force gets higher values, the heat transfer also increases.
  Keywords: low Reynolds numbers; Rayleigh number; Nusselt number; pitching motion; plunging motion; heat transfer; buoyancy force; aerodynamic performance; SEM; spectral element method.
  DOI: 10.1504/PCFD.2025.10071544
   
  
• Computational Investigation of Low-Reynolds-Number Unsteady Flows Past NACA0012  
  by Mertcan Güney, Berkan Anilir, Kurtulus Dilek Funda 
  Abstract: The aerodynamic characteristics of airfoils are significantly governed by the Reynolds number, particularly in the low Reynolds number regime (Re < 1
  Keywords: NACA 0012; unsteady aerodynamics; low Reynolds number; computational fluid dynamics.
  DOI: 10.1504/PCFD.2025.10071614
   
  
• Numerical Investigation of an Airfoil using Leading Edge Rotating Cylinder  
  by Dheeraj Minglani, Vandana Saxena, Ritu Dahiya, A. Anu Kuttan, Laviza Aqeel, Yash Mahore 
  Abstract: This study presents a detailed numerical investigation of the aerodynamic performance of a NACA 0015 airfoil enhanced with a leading-edge rotating cylinder. A parametric analysis was conducted to evaluate the effects of rotational speed (10, 50, 100, 150 and 200 rad/s), cylinder diameter (13, 14 and 15 mm), angle of attack (5, 10, 15, 20, 25 and 30), and the Reynolds number varies with free-stream velocities of 15, 30, 50, and 100 m/s, with corresponding values of 152,279, 304,558, 507,597, and 1,015,193, respectively on the lift coefficient. A non-dimensional parameter, the cylinder surface velocity to free-stream velocity ratio was introduced to assess its influence on flow characteristics and lift enhancement. Results reveal that higher rotational speeds and larger cylinder diameters significantly increase lift coefficient, particularly at elevated angles of attack, with peak lift occurring between 15 and 20. Higher Reynolds numbers further amplify aerodynamic efficiency by delaying flow separation. These findings, supported by validated computational simulations and a predictive polynomial model, highlight the leading-edge rotating cylinder potential as an effective active flow control mechanism. This research provides novel insights into optimising airfoil performance for applications in aerospace, unmanned aerial vehicles, and renewable energy systems.
  Keywords: Airfoil; NACA 0015; Leading Edge Rotating Cylinder; lift coefficient; angle of attack; rotational speed.
  DOI: 10.1504/PCFD.2025.10071760