Progress in Computational Fluid Dynamics, An International Journal (14 papers in press)

Regular Issues

• Computational Analysis of High Speed Super-Cavitating Projectiles for Reduction of Hydrodynamic Drag Using Cavitator Optimisation  
  by Rohini D, Amarkarthik A, Sivaraj G, Haran A.P 
  Abstract: The goal of the paper is the computational analysis of cavitator shape with respect to the forebody of the projectile, which recommends the supercavitation phenomenon. The main target is to provide a phase-changing mechanism for two-phase fluid flow simulation. By employing ANSYS Fluent for disk cavitator, a steady and incompressible two-phase fluid has been analysed, and during the simulation, cavitation is observed. For the designed geometry of the forebody of the projectile, multiphase flow has been chosen, for varying cavitation number of 0.10.01, to optimise the disk cavitators diameter to begin an effective creation of supercavity. The computational analysis of the result displays about the cavity formation, cavity growth, cavity body, and drag prediction for the projectile. To optimise the cavitator diameter, which plays a key role in the formation of supercavitation, 3 mm cavitator disk diameter with a disk to projectile diameter ratio of 0.375 generates the minimum hydrodynamic drag.
  Keywords: super-cavitation projectile; disk cavitator; hydrodynamics; skin friction drag; multiphase flow.
  DOI: 10.1504/PCFD.2024.10064808
   
  
• Analysis of Flow and Thermal Characteristics of a Hybrid Nanofluids within a Microchannel under Magnetic Field  
  by Hakan Türker, Elif Ogut, Erman Aslan 
  Abstract: The study investigates the flow and thermal characteristics of microchannels with varying geometries and boundary conditions. Water is used as the base fluid, with Al2O3 and CuO nanoparticles as additives. The analysis begins with a straight microchannel, followed by comparisons with sinusoidal or sine wave-shaped channels. Additionally, the effects of a magnetic field on a straight microchannel are explored. The numerical simulations, conducted using ANSYS Fluent software, cover Reynolds numbers (Re) of 100, 300, 700, and 1000 in laminar flow, along with volume fractions of 1%, 2%, 3%, 4%, and 5%. A magnetic field intensity of 0.1T is applied for the magnetohydrodynamic (MHD) effect. The results, presented as Nusselt numbers, pressure drop, and thermal performance factor graphs, indicate an increase in Nusselt number with rising Reynolds number and decreasing volume fractions. Pressure drop also rises with increasing Reynolds number and volume fractions.
  Keywords: finite volume method; laminar flow; microchannel; nanofluid; magnetohydrodynamics; convective heat transfer; pressure drop.
  DOI: 10.1504/PCFD.2024.10065361
   
  
• The Optimum Nozzle Exit Position and the Behaviour of a Turbulent Flow in an Ejector Designed for Natural Draft Burner  
  by Chukwunonso. F. Nwoye, Chukwunenye A. Okoronkwo, Godswill Nwaji, Humphrey Okoro, Olisaemeka Nwufor, Emanuel Anyanwu 
  Abstract: This study investigated the near and far stream behaviour of a turbulent flow through an ejector at different axial positions of the nozzle. The study was conducted numerically for a throat-to-nozzle exit axial distance of 5 mm20 mm. The secondary to the primary stream velocity ratio and the magnitude of the boundary layer fluctuation at the nozzle exit increased with the reducing axial distance. The potential core decayed as the flow approached a critical Reynolds number, and the increase in boundary layer fluctuation suppressed the near stream turbulence and momentum transfer by turbulent eddies. The model of the core length as a function of the throat-to-nozzle exit distance revealed a linear profile. Two models described the species concentration along the jet axis as a function of the root mean squared value of the fluctuating velocity because the flow behaved differently near and far streams due to the different controlling mechanisms.
  Keywords: venturi jet; turbulence; nozzle position; velocity ratio; species mixing; initial conditions.
  DOI: 10.1504/PCFD.2024.10065410
   
  
• Multi-Objective Optimisation Approach to Design Passive Micromixers: Taguchi-Based Grey Relational Analysis  
  by Digvijay Ronge, Prashant Pawar 
  Abstract: Micromixers play a crucial role within microfluidic devices to facilitate diffusion mixing. The present study examines the impact of five distinct design parameters of a T-shaped serpentine micromixer namely mixing area shape, micromixer area, channel width, channel spacing, and channel orientation on its mixing efficiency and the pressure drop. Using the Taguchi method of design of experiments (DoE), an orthogonal array (OA) of 27 was constructed, and each experiment was numerically modelled and solved using a computational fluid dynamics (CFD) solver. Signal-to-noise ratio analysis and analysis of variance (ANOVA) were conducted to quantify the impact of each individual parameter. Grey relational analysis (GRA) was employed to optimise the micromixer geometry such that a higher mixing performance is achieved at a lower pressure drop. The optimal micromixer fabricated from Polydimethylsiloxane (PDMS) utilising soft lithography techniques was subjected to experimental validation, showcasing a deviation of 10% from the numerical results
  Keywords: Micromixing; Optimization; Taguchi; ANOVA; Soft Lithography.
  DOI: 10.1504/PCFD.2024.10065412
   
  
• Multi-Objective Optimisation of Automotive Drag Coefficient and Lift Coefficient via Artificial Neural Network and Genetic Algorithm  
  by Zihou Yuan, Hongwei Zhang, Wangyang Xiang, Yanming Du, Xingren Zheng 
  Abstract: In terms of combining traditional methods with others, group method of data handling and radial basis function neural networks have been applied to the study of automotive aerodynamics. Backpropagation neural networks have relatively few applications. The aerodynamic performance of a vehicle is improved by optimising its shape parameters. In this paper, a shape parameter optimisation method is proposed which employs backpropagation neural network model and genetic algorithm to reduce the air resistance and air lift. Five form parameters of the car are taken as design variables and 50 sets of sample data are designed using optimal Latin hypercube experimental design method. After performing CFD simulation, all the data are used for backpropagation neural network learning. Genetic algorithm is then used to perform multi-objective optimisation on all the data and the Pareto front is developed. The results show that the CD and CL of the optimised car are reduced by about 15.28% and 25.85%, respectively.
  Keywords: shape parameters; computational fluid dynamics; CFD; BP neural network; NSGA-II; multi-objective optimisation; Pareto front.
  DOI: 10.1504/PCFD.2024.10066079
   
  
• Aerodynamic Performance of Dragonfly-Inspired Wings in Gliding Flight for Varying Angle of Attack and Reynolds Number: A Numerical Study  
  by Prathmesh Verekar, Satish B. Shenoy, Hamid Yusoff, Irfan Anjum B. Magami, Sarfaraz Kamangar, Mohammad Zuber 
  Abstract: This paper numerically investigates the aerodynamic performance of dragonfly-inspired wings for gliding flight. Dragonfly hind wing morphology (planform and thickness) is considered to create a three-dimensional model. The morphology was obtained from the Aethriamanta brevipennis (Scarlet Marsh Hawk) species of Odonata using a digital micrometer instrument and Scanning Electron Microscope. Gliding flight is known for energy-saving applications. The present study was conducted to assess the effects of the angle of attack
  Keywords: Dragonfly; Gliding; CFD; Wing Morphology.
  DOI: 10.1504/PCFD.2024.10066254
   
  
• Comparison of Aerodynamic Characteristics of a UAV using DATCOM and CFD Analysis  
  by Mukesh Raju, Theerthamalai P, Praveenkumar M, Prashanth M, Inamul Hasan 
  Abstract: DATCOM is a standard tool used to predict the aerodynamic coefficients and stability derivatives as a function of Mach number and angle of attack. The present work simulates the flow field around an unmanned aerial vehicle (UAV) to calculate the aerodynamic forces and moments at Mach number 0.32 for different angles of attack (AOA) ranging from –6° to 14° with a 2° increment. CATIA V5 is used to design the UAV, Ansys fluent is used to simulate the flow field surrounding the UAV, and DATCOM is used to predict their aerodynamic coefficients. The outcomes of the CFD are contrasted with the DATCOM prediction. The CFD aerodynamic coefficients and the DATCOM results agree well. Results suggest that since CFD analysis is time-consuming, DATCOM prediction can be utilised in place of CFD to predict aerodynamic coefficients in the preliminary design. Once the specific design has been settled, CFD analysis can be used.
  Keywords: DATCOM; CFD; aerodynamic prediction; aerodynamic efficiency.
  DOI: 10.1504/PCFD.2024.10066766
   
  
• 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 multiphysics 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
  Keywords: high-lift system; boundary layer separation; boundary layer reattachment; passive flow control; shape modification; adjoint-based gradient.
  DOI: 10.1504/PCFD.2024.10067168
   
  
• Study the Multi-Size Effect of Bubbles in Multiphase Pump based on a Coupled TFM-PBM Model  
  by Juping Zhou, Wei Han, Li Rennian, Diyi Chen 
  Abstract: The coalescence and breakup of bubbles lead to variations in bubble diameter during the flow within the impeller. This study examines the characteristics of bubble size distribution and internal flow mechanisms in multiphase pumps under diverse operating conditions, employing the Eulerian-Eulerian two-fluid model (TFM) and the population balance model (PBM) for analysis. The results show that the main factor leading to gas-liquid phase separation is the pressure gradient force due to the high-density difference. The bubble coalescence frequency at the impeller hub is higher than the bubble breakup frequency with increasing inlet gas volume fraction (IGVF). The large bubbles begin predominating and become the primary cause of air plugging the impeller channel. Moreover, the capacity of the rotating liquid within the impeller to carry the gas improves with an escalating flow rate, impeding the coalescence of bubbles. This dynamic positively influences the gas-plugging behaviour in the channel.
  Keywords: multiphase flow; TFM-PBM coupling model; pressure gradient; gas phase retention; air blocking phenomenon.
  DOI: 10.1504/PCFD.2024.10067233
   
  
• 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 discretization 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 optimized for implicit requirements. An implicit term adjustable by parameter ? 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 utilized 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
   
  
• A Brief Review on Partitioned Semi-Implicit Coupling Methods in Computational Fluid-Structure Interaction  
  by Tao He 
  Abstract: This brief review summarises the procedure and utilisation of the partitioned semi-implicit coupling methods in computational fluid-structure interaction. The semi-implicit framework enables individual fields to be computed in an explicit-implicit way that takes advantage of traditional partitioned explicit and implicit coupling schemes. Depending on the use of the Chorin-T
  Keywords: fluid-structure interaction; partitioned semi-implicit coupling method; projection method; characteristic-based split; arbitrary Lagrangian-Eulerian; ALE.
  DOI: 10.1504/PCFD.2024.10067744
   
  
• 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.