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
   
  
• Development and application of fourth-order-accurate semi-implicit scheme for Navier-Stokes equations  
  by Hao Wang, Yanming Liu 
  Abstract: This paper presents a semi-implicit time discretisation scheme with fourth-order accuracy for the compressible Navier-Stokes equations. The scheme integrates an explicit basis framework with implicit components to enhance stability while maintaining the accuracy of the original explicit scheme. Combining Runge-Kutta and linear multi-step methods, the explicit basis is designed to meet underdetermined equations with free parameters optimised for implicit requirements. An implicit term adjustable by parameter γ is added at each stage to modify implicitness. The resulting implicit scheme is A-stable, verified through linear stability analysis. Applied to space-time decoupled compressible N-S equations, the LU-SGS method is utilised for the implicit operator matrix to reduce computational cost and improve stability, in conjunction with dual-time stepping. Classical test cases demonstrate that the scheme effectively captures shock waves, low-speed turbulence, and shock wave/boundary layer interactions, ensuring accuracy and stability with large time steps, offering higher efficiency than traditional approaches.
  Keywords: semi-implicit; fourth-order accuracy; compressible; A-stability; LU-SGS.
  DOI: 10.1504/PCFD.2024.10067255
   
  
• Arterial mechanical effects of fluid-structure interaction on a stenosed carotid blood pulsatile flow under pressure conditions of normal and hypertension  
  by Md. Jashim Uddin, M.Z.I. Bangalee 
  Abstract: A preceding pathology named atherosclerosis, the most common cardiovascular disease (CVD) involves several hemodynamic factors affecting the arterial wall endothelium cells with increasing morbidity. The fluid-structure interaction technique has been adopted for concurrently confiscating the interaction between the anatomical blood flow dynamics and the properties of wall mechanics with COMSOL multi-physics software that is employed under normal blood pressure (NBP) and high blood pressure (HBP) to detect the significant impacts on hemodynamics in a stenotic carotid artery. The present research intends to explore that von Mises stress across the artery wall has significantly increased in HBP compared to that in NBP. Results indicate that the variations of wall displacement and recirculation length occur due to the elastic model under pressure conditions. The time-averaged wall shear stress, oscillatory shear index and relative residence time suggest that the potential risk parameters due to atherosclerotic thrombus deposition have a sequentially reduced separation length with an increase of mechanical elastic modulus.
  Keywords: fluid-structure interaction; FSI; mechanical elasticity; pressure gradient; recirculation length; von Mises stress; wall displacement.
  DOI: 10.1504/PCFD.2024.10067087
   
  
• Flow sensitivity to trailing edge design for a two-element airfoil at low Reynolds numbers  
  by Dilip Lalchand Parmar, Deepak Kumar Singh, Arjun Sharma 
  Abstract: The sensitivity of flow past a two-element airfoil to changes in the geometry of trailing segment of the main element is studied using Reynolds-averaged-Navier-Stokes simulations at Reynolds numbers, 5 × 10⁴ and 1.5 × 10⁵ and angles of attack in the range 0 to 7 degrees. Adjoint-based gradient data are used to make systematic changes to the shape in a localised region around the trailing edge of the main element with the objective of maximising the lift-to-drag ratio. The introduced shape changes tend to modify the converging-diverging flow passage that forms in the overlap region between main element and flap such that separation on the flap suction surface is delayed. Improvements in lift-to-drag ratio of 28% and 10% are obtained at angles of attack 0 and 5 degrees respectively at lower Reynolds number of 5 × 10⁴ whereas the improvements at higher Reynolds number are comparatively lower.
  Keywords: high-lift system; boundary layer separation; boundary layer reattachment; passive flow control; shape modification; adjoint-based gradient.
  DOI: 10.1504/PCFD.2024.10067168
   
  
• Effect of centred hole angular ribs roughness on the solar collector performance in a square tube  
  by Suvanjan Bhattacharyya, Kunal Dey, Devendra Kumar Vishwakarma, Varun Goel, Mohsen Sharifpur 
  Abstract: The numerical study assessed the heat transfer and pressure drop in an evenly heated square duct with plane and perforated ribs. Working fluid is air with Reynolds number (Re) 10,000-80,000. The pitch ratio (y), the dimensionless spacing between ribs relative to hydraulic diameter, is 0.5, 1.0, and 1.5. Rib inclination angles (θ) from the downstream duct wall range from 30° to 60°. The hole ratio (h) is 0.1 to 0.2, depending on perforation size and hydraulic diameter. In all configurations, the heat transfer improvement is maximum at Re = 10,000 and gradually decreases with rising Re. The thermal performance factors (η) for Re = 10,000 vary between 1.4 and 2.2, depending on configuration. The highest η is found at θ = 60°, y = 0.5, h = 0.2. At Re = 40,000, all configurations have η values over 1. The thermal performance for Re = 80,000 is moderate (η ≈ 1.03) for θ = 60°, y = 0.5, h = 0.2. Other configurations provide lower values that are barely over unity.
  Keywords: rib roughness; solar collector; square channel; inclination angle; pitch ratio.
  DOI: 10.1504/PCFD.2024.10069033