Progress in Computational Fluid Dynamics, An International Journal (15 papers in press)

Regular Issues

• Implementation of a New Actuator Disk Model based on BEM Theory in SU2 CFD SOFTWARE  
  by Kaan Yenipazar, Dilek Funda Kurtulus 
  Abstract: The aim of the current study is to develop an alternative actuator disc model in the SU2 (Stanford University Unstructured) software using the blade element theory (BEM) approach. The objective is to reduce computational costs and save time with accurate results. The integrated model has applications in optimizing rotating components such as propellers, wind turbines, axial turbines, etc., as well as accurately predicting wake structures. The new actuator disc model proposed in this study is a steady-state model that assumes an infinite number of blades within the disc domain, making it applicable to varying flow conditions, such as the forward flight of helicopters or aircraft experiencing an angle of attack. The new model was validated by comparing it with experimental data and another high-fidelity tool, which is the rotating frame approach. These comparisons demonstrated that the new model performs accurately and can be a better option than the rotating frame.
  Keywords: SU2; blade element theory; BEM; computational fluid dynamics; CFD; actuator disc; propeller; wind turbine; impeller.
  DOI: 10.1504/PCFD.2024.10064025
   
  
• Numerical Investigation of the Effect of Radiator Placement on Temperature Distribution in a Room  
  by Hande Ufat 
  Abstract: This study analyses the impact of radiator placement on temperature distribution in a room using CFD analysis. Radiators are typically placed under windows or on outer walls. However, in the area under study, where there are large windows extending to the floor on the outer walls, the radiator was positioned on the empty inner wall. Two variations of the analysis were conducted using the ANSYS Fluent program. One variation involved a vertical installation of an aluminium panel radiator of the same length as the existing radiator on the outer wall next to one of the two windows. The other variation involved the installation of two radiators of the same length as the existing radiator next to the windows. The results showed that the room heated up faster when two radiators were used compared to other alternatives. Heating a room with two radiators of equal length and surface temperature results in a faster temperature increase. When a radiator is positioned vertically, the average temperature remains the same as the current situation. Using multiple smaller radiators instead of a single large one that provides the same amount of heat allowed the environment to warm up more quickly.
  Keywords: CFD analysis; thermal comfort; panel radiator; temperature distribution.
  DOI: 10.1504/PCFD.2024.10064248
   
  
• Comparative Analysis on Heat Transfer, between a Steady and Oscillating Jet in a Cavity  
  by Farida Iachachene, Amina Mataoui 
  Abstract: This paper numerically investigates the cooling of a heated rectangular cavity by a cold slot jet. The study aims to examine the effect of the jet location inside the cavity (Lf and Lh) and Reynolds number on heat transfer, using URANS turbulence modelling. Different flow behaviours, including oscillatory and steady flows, are generated depending on the jet location inside the cavity. The study identifies and discusses the optimal jet locations for achieving optimal cavity cooling. The results indicate that the lateral placement of the jet has a negligible effect on heat transfer across all cavity walls. Additionally, oscillatory flow consistently expands the heat exchange zone along all three walls, resulting in a wider effective exchange area compared to steady flow conditions. The study proposes optimised jet positions within the cavity for specific wall cooling requirements. By considering the optimal combination of jet height and impinging distance, the cooling performance can be optimised.
  Keywords: jet-cavity interaction; heat transfer; URANS; finite volume method; oscillatory flow; steady flow; slow jet; CFD; jet location; optimal jet locations.
  DOI: 10.1504/PCFD.2024.10064417
   
  
• Numerical investigation of lucid spherical cross-axis flow turbine concerning changeover on its geometrical parameters in a pipeline compared to a channel  
  by Hamidreza Zarei, Mahmoud Pasandidehfard 
  Abstract: This paper presents an investigation on the performance of a lucid spherical turbine. To verify the numerical predictions the experimental results of Bachant and Wosnik have been used. Drag and power coefficients have been used to compare with the data for the water inlet velocity 1m/s and different non-dimensional tip-speed-ratio. Two airfoil sections, NACA 2412 and NACA 64(3)418, have been selected to design the turbine blades. The impact of four effective blade parameters, inclusive of profile section, chord length, number of blades, and blade twist angels, on turbine performance, is investigated. It can deduce that the power coefficient has increased up to 22% for NACA 2412 compared to the experimental test. Also, the three-bladed turbine possesses the best results among all models. The twist of the blades caused to increase in the power coefficient by 19% and 31% for NACA 2412 and NACA 64(3)418 sections inside the channel respectively.
  Keywords: lucid turbine; asymmetric hydrofoils; lift coefficient; power coefficient; pipeline.
  DOI: 10.1504/PCFD.2024.10064482
   
  
• 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
   
  
• Three-dimensional flow evaluation of monarch butterfly wing  
  by Fadile Yudum Comez, Nevsan Sengil, Dilek Funda Kurtulus 
  Abstract: The current study aims to examine the flow field around a monarch butterfly wing at different angles of attack. A fully opened forewing configuration for the monarch butterfly wing has been selected for analysis at a maximum chord length. To mimic the membrane of the real monarch butterfly wing, the thickness of the wings has been taken as 0.15 mm. In this study, the Reynolds number is calculated as 9,724 for a 5 m/s freestream velocity. The effect of the angle of attack has been investigated between α ∈ [0, 40°] with a 2° increment from 0° to 10°, and a 10° increment from 10° to 40°. The aerodynamic coefficients are compared with the experimental and numerical results available in the literature. Furthermore, the vortex dynamics for different angles of attack are investigated to understand leading-edge vortex deformation.
  Keywords: computational fluid dynamics; CFD; monarch butterfly; micro air vehicles; leading-edge vortex; LEV; unsteady aerodynamics.
  DOI: 10.1504/PCFD.2023.10058561
   
  
• Flow separation control in a three-element airfoil system at moderate Reynolds number  
  by Deepak Kumar Singh, Dilip Lalchand Parmar, Arjun Sharma 
  Abstract: The flow past a three-element, high-lift system is studied using Reynolds-averaged Navier-stokes simulations at Reynolds number of 1.5 × 10⁵. Two values of free-stream angles of attack, 5° and 13°, are considered that correspond to linear-lift and post-stall limits, respectively, for the main element plus flap system. The effects of increase in camber of slat geometry are examined at different deflection angles in terms of an effective angle of incoming stream towards the slat. Viscous effects including boundary layer separation on slat, emergence of a thick wake from slat and rapid merging of slat wake with boundary layer on main element are observed to adversely impact the net lift coefficient for values of deflection angle below a certain threshold. In the presence of slat, a lift coefficient of 1.5, an increase of 7% above the value corresponding to the main element plus flap configuration, is obtained at α = 5°.
  Keywords: high-lift system; boundary layer separation; active flow control.
  DOI: 10.1504/PCFD.2023.10058988
   
  
• Investigations on the use of URANS equations to characterise the wind turbine wake in a non-neutral boundary layer  
  by Siheme Guezmir, Amina Mataoui, Ouahiba Guerri 
  Abstract: The aim of this paper is to show to what extent unsteady Reynolds averaged Navier-Stokes (URANS) equations, coupled to the actuator disk (AD) theory, could simulate the flow in the wake of wind turbines, taking into account atmospheric boundary layer (ABL) thermal stratification. First, the URANS/AD model is validated by the computation of the flow in the wake of a porous disk modelling a small wind turbine. Then, the investigations are applied to a large wind turbine in a neutral and non-neutral ABL. The obtained velocity contours and profiles are compared to available LES results. The effects of the thermal stratification on the added turbulence and expected turbine power are evaluated. The results obtained show the ability of URANS/AD calculations to characterise wind turbine wakes in a non-neutral ABL.
  Keywords: wind turbine wake; non-neutral boundary layer; atmospheric boundary layer; ABL; CFD; unsteady Reynolds averaged Navier-Stokes; URANS.
  DOI: 10.1504/PCFD.2024.10063291
   
  
• RANS simulation of wind pressure development on mono-slope canopy roofs  
  by Ajay Pratap, Neelam Rani 
  Abstract: This study examines the effect of various roof slopes of mono-slope canopy roofs (MCRs) on wind pressure distribution under various wind directions. The wind tunnel experiment is carried out on a 15° roof slope at 0° to 180° wind incidence (@30° interval) angle and validated using a 3D steady Reynolds-averaged Navier-Stokes (RANS) simulation. Further, sensitivity analysis pertaining to grid resolution and different turbulence models are performed to improve the RANS simulations at 15° MCR. It is found that the realisable k-ε turbulence model depicts more accurately and captures the flow separation, stagnation point, downstream and upstream flow. Under the parametric study, the RANS simulations are extended for (5°, 15°, 25°, 35°, and 45°) roof slopes for the exact wind directions. Mono-slope canopy with roof slope between 0° to 25° are found to be critical at 150° wind incidence angle due to higher wind pressure.
  Keywords: mono-slope canopy roof; computational fluid dynamics; CFD; pressure coefficient; Reynolds-averaged Navier-Stokes; RANS; overall coefficient; drag and lift coefficient.
  DOI: 10.1504/PCFD.2023.10058679
   
  
• Unsteady three-dimensional multiphase modelling of anode flow distributor in PEM electrolysis cell  
  by Safiye Nur Özdemir, Imdat Taymaz 
  Abstract: A polymer electrolyte membrane electrolysis cell (PEMEC) is a system in which water is oxidised at an oxygen electrode, producing oxygen gas on the anode electrode and hydrogen gas on the cathode electrode, respectively. In this study, we aim to develop a three-dimensional, unsteady numerical model of the anode flow field plate (AFFP) for the PEMEC system that focuses on two main objectives: the first objective is to characterise the two-phase flow distribution. The second purpose is to change the channels in the AFFP, analyse their effect on pressure drop, velocity, and oxygen gas distribution, and determine the appropriate number of channels. The three-dimensional, single-domain, and isothermal model of an AFFP was applied in the commercial computational fluid dynamics (CFD) code; it was well-validated with the experimental results of a PEMEC with a parallel flow field. Numerical results show that the pressure gradient decreases diagonally from the inlet port to the outlet port along with the AFFP. It was recorded that when the number of electrode channels was increased from 4 to 16, the pressure drop decreased by 33% but also increased by approximately 73 Pa when it was increased from 16 to 20.
  Keywords: green hydrogen production; PEM electrolysis cell; anode flow field plate; AFFP; computational fluid dynamics; CFD modelling; two-phase flow.
  DOI: 10.1504/PCFD.2023.10058697
   
  
• Modelling of multi-species thin film flows based on the transport of ions including conjugate heat transfer applied to corrosion testing  
  by Uwe Janoske, Steffen Seifritz 
  Abstract: Corrosion tests are standardised test procedures where specimen is subjected to different climates in test chambers with defined test cycles. The cycles are a complex scenario of spraying, drying and condensation phases. Aqueous sprays with different salts lead to liquid films and corrosion processes on the specimen. As there are various kinds of salts present which will deposit based on the local concentration of the ions, the stoichiometry and the solubility, the conventional modelling with a given number of species is extremely difficult. Therefore, the modelling approach for handling species was changed to the modelling of the transport of ions in the film including condensation and evaporation. The verification is reported on a simple U-shaped specimen whereas a more complex specimen was used for the validation with experimental results on the basis of a standardised test cycle in corrosion testing.
  Keywords: multi-species; computational fluid dynamics; CFD; fluid films; droplets; dissolution; condensation; evaporation; conjugate heat transfer; corrosion; testing.
  DOI: 10.1504/PCFD.2023.10063153
   
  
• A computational study of air film evolution during droplet impact on a flat solid surface  
  by Umesh, N.K. Singh 
  Abstract: The present study employs the volume of fluid (VOF) method to meticulously resolve the phenomenon of air trapping, capturing its evolution all the way into a spherical air bubble. The impact of velocity and droplet size on the air films progression is investigated; findings reveal that the micro bubble remains detached from the surface for lower impact velocity while it settles down on the surface for higher impact velocities. This outcome holds potential for practical applications requiring air bubble elimination by optimising the impact velocity. Furthermore, the presence of an air film impedes surface-to-droplet heat transfer. The solid surface experiences an increase in wall heat flux where the droplet contacts it, compared to air-solid contact regions due to waters superior thermal conductivity. Notably, maximum wall heat flux occurs at higher impact velocities, amplifying convection heat transfer.
  Keywords: drop impact; two phase simulation; VOF method; air entrapment; impact velocity; droplet size.
  DOI: 10.1504/PCFD.2024.10063785
   
  
• Integrated approach for geometric and kinematic design of centrifugal compressor impellers  
  by Ashwin Shelke, Ashok Mache, Aditya Shelke, Pradyumn Chiwhane, Viral Patel 
  Abstract: Centrifugal compressors are widely used across industries like oil and gas, chemicals, energy generation, and HVAC systems. They convert gas kinetic energy into high-pressure energy. The impeller and diffuser play key roles in this process. Designing the impellers 1D Meridional plane is critical for sizing and operational characteristics. This study establishes an analytical design methodology to determine impeller parameters, satisfying the pressure ratio, efficiency, and mass flow rate requirements. Further, Blade parameters to withstand operational stresses are also determined. Computational fluid dynamics (CFD) validates the model using the SST k- model, ensuring reliable results through mesh convergence. The simulation aligns well with analytical parameters. This study provides a strong foundation for optimising analytical compressor design methodologies.
  Keywords: centrifugal compressor; impeller; preliminary design; meridional plane.
  DOI: 10.1504/PCFD.2023.10059900
   
  
• Hydrothermal performance of Al₂O₃/water nanofluid in a vented cavity including hot cylinder covered by a porous layer utilising LTNE approach  
  by Farrokh Mobadersani, Amirreza Jamshid Malekara 
  Abstract: This paper aims to examine the heat transfer rate and flow characteristics of Al₂O₃/water nanofluid in a vented cavity containing a hot square cylinder covered by a layer of porous media. The local thermal non-equilibrium (LTNE) model is employed to couple heat transfer in the solid matrix and nanofluid of the porous domain. The governing equations are numerically solved using the finite element method. Effects of thermal conductivity ratio, Darcy number, Reynolds number, porous layer thickness, dimensionless heat transfer coefficient, and cylinder size, are investigated. The outcomes reveal that at Re = 50, inserting the porous layer can enhance the average Nusselt number by 122% compared to the non-porous case. Furthermore, based on the calculated performance evaluation criterion, the use of a porous layer provides effective hydrothermal performance in low Reynolds numbers. The results indicated that implementing local thermal equilibrium in higher Reynolds and Darcy numbers leads to unreliable results.
  Keywords: vented cavity; mixed convection; nanofluid; local thermal non-equilibrium; LTNE; performance evaluation criteria; PEC.
  DOI: 10.1504/PCFD.2024.10063442
   
  
• Numerical study for separation of particles in helical microchannel  
  by U.D. Nimbalkar, Apoorv Sureshkumar Mishra, Pankaj E. Rawool, V.K. Agrawal 
  Abstract: The present work was aimed at studying the Dean flow pattern in the cross-section of the helical microchannel and its effect on the inertial focusing of bloodstream particles. The Dean flow, a fundamental phenomenon in fluid dynamics, illustrates fluid flow through curved geometries where centrifugal force interacts with pressure gradient. The rectangular, aspect ratio 0.8 and 0.6, and circular 80 μm diameter cross-sections of same axial pitch were analysed for Reynolds number ~ 40, Dean number ~ 9 and Ratio of lift-to-drag forces ~ 0.5. Appreciable focusing was observed as a part of numerical studies, leading to a fine stream of particles at the outlet. The results were analysed and compared with the previous studies. Hence, a rectangular cross-section helical microchannel design is proposed for particle separation that can be fabricated with any suitable polymer.
  Keywords: particle separation; inertial focusing; helical microchannel; microfluidics; Dean flow.
  DOI: 10.1504/PCFD.2024.10064022