Progress in Computational Fluid Dynamics, An International Journal (12 papers in press)

Regular Issues

• Impact of a Four-Hydrofoil Configuration on Trimaran Resistance: Two Angled Bow Foils on Longer Struts and Two Stern Foils on Shorter Struts  
  by Aliakbar Ghadimi, Hassan Ghassemi, Parviz Ghadimi 
  Abstract: This study investigates how installing four NACA0015 hydrofoils to a trimaran hull affects performance, aiming to reduce fuel consumption by minimizing resistance. Using Star-CCM+ and URANS equations, the research analyzed the impact of two angled hydrofoils at the bow and two angled at the stern on a trimaran's performance. The methodology involved modeling the trimaran, hydrofoils, and struts, creating a computational domain with appropriate boundary conditions, and performing mesh independence testing. Validation was achieved through a catamaran simulation. Results at Froude numbers ranging from 0.8 to 1.5 showed improved CL/CD ratios with hydrofoils. Meanwhile, trim improved at lower speeds but decreased at higher speeds. Pressure resistance increased, while frictional drag was significantly reduced at high speeds. Overall, total resistance increased at lower speeds but decreased at higher speeds, notably a 44.8% reduction at Froude number 1.5, demonstrating the potential of these hydrofoil configurations for improved high-speed efficiency.
  Keywords: Trimaran; hydrofoil; resistance reduction; CFD; High-speed planing hull; numerical analysis; Star-CCM+.
  DOI: 10.1504/PCFD.2025.10072680
   
  
• A Systematic Review on Aerodynamics and Aero-Acoustics of Supersonic Jets  
  by Amiruzzahan Mondal, Shashi Kant Verma, Saif Akram 
  Abstract: This study presents a comprehensive review of the aerodynamics and aero-acoustics of supersonic jets, with an emphasis on active and passive flow controls that improve mixing effectiveness and noise reduction. The study explores the impact of various control techniques, such as tabs, grooves, and fluid injectors, on noise reduction, shock structures, and jet core dynamics. The impact of Mach numbers, Strouhal numbers, NPRs, overexpanded and under-expanded conditions on jet flow properties is assessed using both experimental and numerical data. The research attempts to provide a coherent knowledge of jet behaviour and its underlying mechanisms by combining data from multiple investigations. By comparing the results of different active and passive flow control techniques, ventilated and delta tabs are found to be the best methods for attaining exceptional performance. The best control technique, which enhances the jet mixing and noise reduction, is identified, and the schematic of the proposed tab is presented.
  Keywords: Supersonic Jet; Aero-Acoustics; Flow Control; Nozzle pressure ratio; Mach number.
  DOI: 10.1504/PCFD.2025.10073607
   
  
• Investigation using a One-Way Coupled FE-Structural and FV-Hemodynamic Simulation for Identifying the Factors causing the Progression of a Saccular Aneurysm Model  
  by Suraj Raj, ANIL L.A.L. S, Anjan R. Nair 
  Abstract: Rupture risk assessment of cerebral aneurysms through computational modelling has gained importance due to the absence of objective clinical methods and challenges in experimental approaches. This study uses a one-way FSI approach with a non-Newtonian Carreau viscosity model on an idealized 3D saccular aneurysm in a curved artery to analyse key hemodynamic and structural parameters. Velocity magnitude, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), vorticity magnitude, von-Mises stress, and total displacement were evaluated across the cardiac cycle. A low-velocity stagnation zone was observed within the aneurysm sac. TAWSS was lower inside the sac but peaked near the distal end, where OSI values exceeded 0.2, reaching up to 0.45, indicating vulnerable regions. Vorticity and q-criterion analyses highlighted disturbed, vorticity-dominated flow regions. Maximum von Mises stress and displacement were observed near the distal regions, suggesting that shape distortions contribute significantly to aneurysm progression and rupture risk.
  Keywords: Cerebral aneurysm; rupture risk assessment; computational modelling; fluid-structure interaction (FSI); non-Newtonian; Carreau model;wall shear stress (WSS); oscillatory shear index (OSI); vorticity.
  DOI: 10.1504/PCFD.2025.10073915
   
  
• The Paradigm Shift of Convective Instability in Pipe Flow: a Comprehensive Review  
  by Saurabh Kapoor, Durgaprasad Nayak 
  Abstract: This article provides a comprehensive overview of various methods used to enhance the thermal performance of heat exchangers, along with the stability mechanisms of convective flows. Heat transfer occurs through three primary modes: radiation, conduction and convection. Among these, convection is one of the most significant and can be categorised as free, forced, granular, gravitational or thermomagnetic. Over the past few decades, numerous studies have investigated convective heat transfer in pipes. This paper presents a detailed review of fluid flow in pipes, aiming not only to evaluate previous research comprehensively but also to provide readers with valuable existing knowledge that may facilitate future studies. The effects of key dimensionless parameters such as the Rayleigh, Reynolds, Prandtl, Grashof, Nusselt and Darcy numbers, as well as pipe length, on heat transfer are also discussed. Additionally, the paper includes a brief discussion on the instability mechanisms of mean flow in pipes based on recent stability analyses.
  Keywords: Porous Medium; Poiseuille Flow; Convection; Heat Transfer; Double Diffusion; Stability Analysis.
  DOI: 10.1504/PCFD.2025.10074278
   
  
• Optimisation of Drag reduction for Passive flow Control based on a Notchback MIRA model  
  by Xingren Zheng, Lingxi Deng, Zihou Yuan, Yanming Du, Hongwei Zhang 
  Abstract: This paper investigates the application of passive flow control for optimising automotive aerodynamic drag reduction, based on a notchback MIRA model. The study uses a computational fluid dynamics (CFD) simulation, a neural network prediction model and a genetic algorithm to optimise and combine the body geometry features and duckwing add-ons in a step-by-step manner. The results show that optimising the body independently reduces the drag coefficient (CD) by 12.4%, while optimising the duckwing independently reduces it by 21.109%. Combining the optimal parameters of the body and the duckwing in a composite optimisation scheme reduces the drag coefficient of the whole vehicle to 0.24509 up to 24.09% less than the original model. Flow field analysis shows that composite optimisation significantly improves rear flow field structure, effectively compresses the low-speed region and significantly reduces turbulence intensity while enhancing tail pressure recovery. This study provides an efficient optimisation strategy for the design of automotive aerodynamic drag reduction, which is important for improving vehicle energy efficiency and reducing emissions.
  Keywords: computational fluid dynamics; CFD; artificial neural network; ANN; genetic algorithm; GA; automotive aerodynamics; passive flow control; parameter optimisation.
  DOI: 10.1504/PCFD.2025.10074740
   
  
• Numerical Investigation on Head-On Droplet Collisions based on Modified Coupled Level Set-VOF  
  by Xiaohang Qu, Qianjian Guo, Xiaoni Qi 
  Abstract: Seawater droplet collision phenomenon exists widely in marine environments. A model is developed for the collision process of seawater droplets composed of various salts. The head-on collision of binary equal-sized seawater droplets has been investigated based on the phase interface tracing method of coupled level set-VOF with the adaptive mesh refinement. The initialisation method of phase function, the solution method of convection transport equation of the phase function, the construction and realisation method of phase interface and the method of function re-initialisation are developed. The tetradecane droplet collisions are numerically studied to validate the numerical method. The results show good agreement with experimental data from the literature. The head-on collisions of seawater droplet are first numerically investigated at various Weber numbers (from 0.5 to 200). Different collision outcomes have been observed for various parameters, such as coalescence and reflection separation. The critical Weber number of separation is obtained. The evolution of the droplets kinetic energy, the surface energy and the dissipation energy as well as the maximum deformation for seawater droplets is also evaluated. This work contributes to a fundamental understanding of the mechanism of seawater droplet collision and the application of droplet collision models to related processes.
  Keywords: Droplets collision; Seawater; Numerical investigation; Modified Coupled Level Set-VOF (M-CLSVOF).
  DOI: 10.1504/PCFD.2025.10075233
   
  
• Numerical investigation for the flow past a single, and in-line stick-slip cylinder in a planar flow  
  by Manish Dhiman  
  Abstract: Flow past bluff bodies is a fundamental problem in fluid mechanics. Recently, the influence of confinement on such flows has gained significant attention, as nearby no-slip walls can markedly alter phenomena like flow separation and stagnation points. Concurrently, the development of Janus cylinders materials with distinct surface properties have shown considerable promise in various applications. In this study, flow structures and hydrodynamic forces on a circular stick-slip (Janus) cylinder, centrally placed within a confined channel, are investigated at low cylinder Reynolds numbers (Rep = 1100) for different channel-to-cylinder diameter ratios (H/D). Comparisons are made with conventional uniform-surface (stick) cylinders. Results show that the recirculation zone enlarges with increasing H/D, and shear stress distributions indicate that separation points shift further downstream. Empirical correlations for drag, lift, and moment coefficients are proposed. Additionally, the flow over two in-line stick-slip cylinders is analysed, revealing significant alterations in streamline patterns and hydrodynamic forces.
  Keywords: Stick-slip cylinders; confinement; in-line array.
  DOI: 10.1504/PCFD.2025.10075737
   
  
• Swimming Performance of Two-Dimensional Undulating Fins with Different Wavelengths in Near-Wall Environment  
  by Xiangxiang Wang, Hualong Xie, Jialin Li 
  Abstract: To investigate the ability of undulating fins with different wavelengths to utilise the wall effect to enhance swimming efficiency, this paper simulates the forward motion of undulating fin models with different wavelengths at different distances from the wall, using a two-dimensional cutaway model of the pectoral fin of the skate as an object of study. The authors find that the swimming speed and propulsive force of the long-wavelength model are significantly better than those of the shorter-wavelength model. Moreover, the kinematic states of the undulating fin models with different wavelengths are more obviously changed when they swim near the wall, and the longer the wavelength is, the greater the gain in swimming performance obtained by swimming near the wall. This paper explains why the longer the wavelength, the more affected by the wall effect through the change of the wake vortex, and explains the phenomenon that the lateral input power becomes larger near the wall through the change of the pressure.
  Keywords: wall effect;undulating fin;vortex structure ;Promoting efficiency.
  DOI: 10.1504/PCFD.2025.10075887
   
  
• Simulation of Mixed Convection in a Modified T-Shaped Enclosure with an Insulated Vertical Strip  
  by Hamza Khan, Humayoun Shahid, Yasir Nadeem, Salman Arif Cheema, Fayyaz Ahmed 
  Abstract: This study explores the influence of a centrally located insulated strip in a reverse T-shaped enclosure on fluid flow and heat transfer using the Multi-Relaxation-Time Lattice Boltzmann Method (MRT-LBM). The bottom wall is uniformly heated and driven by a moving lid at velocity $u=u_0$, while the remaining walls are cold, except for insulated bottom shoulder segments with $frac{partial T}{partial y}=0$. The vertical insulated strip allows flow near both the top and bottom walls, acting as a passive thermal barrier. Simulations are conducted for Grashof numbers from $10^4-10^6$, Richardson numbers from $0.01-100$, and Prandtl numbers from $0.7-70$. The geometric influence is examined by varying $frac{L_1}{L}$ and $frac{L_2}{L}$. Results include streamlines, isotherms, and local Nusselt number profiles, revealing that the strip significantly modifies convective structures and enhances heat transfer behaviour.
  Keywords: Heat transfer; Mix-Convection; Reverse T-Shaped; lattice-Boltzmann method; Multi-relaxation-time.
  DOI: 10.1504/PCFD.2025.10075941
   
  
• Parametric Vernacular: Decoding Climate-Adaptive Modular Design in Concave-Shaped Huizhou Skywell Dwellings through CFD Simulation  
  by Hui Dai, Mengjun Zhu, Hui Shao, Minghan Yang, Decai Gong 
  Abstract: Huizhou traditional dwellings, exemplifying climate-responsive vernacular architecture, have evolved over centuries into a modular system adapted to local climates. This study examines the concave-shaped plan in Chengkan Village, identifying the stepped column height as the core modular unit for skywell geometry. Using a Ming Dynasty dwelling as a prototype, nine parametric skywell variants were created, and their aerodynamic performance was assessed using computational fluid dynamics (CFD), focusing on the aperture-to-base area ratio. Key findings include: first, skywell height has limited impact on wind dynamics (with an influence coefficient of approximately 0.12), confirming the ecological rationality of vertical expansion; second, depth and aperture ratio optimise spatial efficiency and microclimate; and third, inverted trapezoidal forms enhance passive airflow through Venturi effects. This parametric analysis reveals a framework of parametric dominance, evolutionary optimisation, and modular harmony, illustrating how vernacular modularity enables climate adaptation while balancing heritage conservation and environmental performance.
  Keywords: traditional vernacular dwellings; parametric modular system; wind-driven ventilation; computational fluid dynamics simulation; heritage conservation.
  DOI: 10.1504/PCFD.2025.10076575
   
  
• The Effect of External Fluid Flow Direction on the Rheological Behaviour of Nano-Sized Sand in Hydrated Slurry using Molecular Dynamics Simulation  
  by Milad Jahanbakhsh Ghahjaverestani, Mehdi Jamali Ghahderijani, Arash Karimipour, Davood Toghraie, Mohamad Mehdi Razzaghi 
  Abstract: This study presented molecular dynamics simulations to investigate the rheological and agglomeration behaviours of nano-sized sand in hydrated slurry under horizontal and vertical external flows. The simulations assessed how flow direction affected sand nanoparticle behaviour. A 10 ns simulation duration was sufficient to reach equilibrium, with temperature stabilising at 299.19 K and kinetic energy at 0.89 kcal/mol. Under Earths gravity, flow direction was found to significantly influence structural evolution. Perpendicular external forces caused strong atomic fluctuations, especially in the central region, with a peak temperature of 350.96 K. In side regions, oil molecule agglomeration led to particle velocities of 0.00072
  Keywords: Asphaltene; Agglomeration time; Hydrated slurry; Flow Direction; Molecular Dynamics Simulation.
  DOI: 10.1504/PCFD.2025.10076633
   
  
• Effects of the Overlap Ratio on the Power and Aerodynamic Coefficients of Semi-Circular and newly developed Parabolic Blade Profiles in a Savonius-Style Wind Turbine  
  by Eusebious Theodynosious Chullai, Subhendu Maity, Bikash Sarkar 
  Abstract: The Savonius wind turbine, a vertical-axis wind turbine, is valued for its simplicity and off-grid power potential. To improve its efficiency, various blade configurations have been explored, with scope for further innovation. This study investigates the effect of the overlap ratio (OR) on a newly developed parabolic blade profile and compares it with a traditional semi-circular profile. Using 2-D simulations with the SST k-? model at Reynolds number = 1.12x 105, results show that at OR = 0.0, the parabolic rotor outperforms the semicircular rotor at all tested tip speed ratios (TSRs), achieving an 11% higher in maximum power coefficient. Further analysis at TSR = 0.8 reveals optimal ORs of 0.15 and 0.10 for the semicircular and parabolic rotors, respectively, improving power coefficients by 6% and 2%. Enhanced aerodynamic interactions at these ORs improve energy capture, supported by lift, drag, and velocity contour analysis.
  Keywords: Savonius wind rotor; parabolic profile; overlap ratio; power coefficient; aerodynamic coefficient; SST k-? turbulence model.
  DOI: 10.1504/PCFD.2025.10076692