Forthcoming and Online First Articles

Progress in Computational Fluid Dynamics, An International Journal

Progress in Computational Fluid Dynamics, An International Journal (PCFD)

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Progress in Computational Fluid Dynamics, An International Journal (16 papers in press)

Regular Issues

  • Investigations on the use of URANS equations to characterize the wind turbine wake in a non-neutral boundary layer   Order a copy of this article
    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 modeling 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 characterize wind turbine wakes in a non-neutral ABL.
    Keywords: wind turbine wake; non-neutral boundary layer; ABL; CFD; URANS.

  • Three-dimensional Flow Evaluation of Monarch Butterfly Wing   Order a copy of this article
    by Fadile Yudum Comez, Nevsan Sengil, Kurtulus Dilek Funda 
    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 [0, 40
    Keywords: CFD; Monarch Butterfly; Micro Air Vehicles; leading-edge vortex; unsteady aerodynamics.
    DOI: 10.1504/PCFD.2023.10058561
     
  • RANS simulation of wind pressure development on mono-slope canopy roofs   Order a copy of this article
    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
    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 modeling of anode flow distributor in PEM electrolysis cell   Order a copy of this article
    by Safiye Nur Ozdemir, 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
     
  • Flow separation control in a three-element airfoil system at moderate Reynolds number   Order a copy of this article
    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
    Keywords: high-lift system; boundary layer separation; active flow control.
    DOI: 10.1504/PCFD.2023.10058988
     
  • Integrated Approach for Geometric and Kinematic Design of Centrifugal Compressor Impellers   Order a copy of this article
    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 impeller's 1D Meridional plane is critical for sizing and operational characteristics. This study establishes an analytical design methodology to determine impeller parameters, meeting pressure ratio, efficiency, and mass flow rate requirements. 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 optimizing analytical compressor design methodologies.
    Keywords: Computational Fluid Dynamics Centrifugal Compressor Impeller Meridional Plane.
    DOI: 10.1504/PCFD.2023.10059900
     
  • Numerical study of liquid imbibition and contact line pinning in a sealing gap for corrosion protection of metal housings   Order a copy of this article
    by Daniel Hagg, Alexander Eifert, Torsten Troßmann, Bettina Frohnapfel, Holger Marschall, Martin Wörner 
    Abstract: Sealing gaps are common in housings that protect sensitive assemblies from potential damage by the environment. A prevalent measure to prevent water from reaching the sealing ring are pinning grooves. In this work, the influence of material wettability on the capillary-driven penetration of water into a generalised sealing gap geometry with pinning groove is investigated numerically for the first time. Interface-resolving two-phase flow simulations are performed with a diffuse-interface phase-field method solving the coupled Cahn-Hilliard Navier-Stokes equations. In the simulations of a gap geometry with pinning groove, the imbibition process is slowed down but not stopped for contact angles up to about 50°, while imbibition is prevented for contact angles larger than about 55°. The different behaviour is explained by the edge effect in wetting which interacts with liquid inertia. Volume-of-fluid simulations performed for comparison show similar behaviour with slight differences in imbibition speed and much higher spurious currents.
    Keywords: Cahn-Hilliard; capillarity; diffuse interface; edge effect in wetting; electronic housing; imbibition; phase-field method; sealing gap; two-phase simulation; volume-of-fluid; VOF.
    DOI: 10.1504/PCFD.2023.10055191
     
  • Study of the separation characteristics of gas-liquid-solid multiphase flow in the impeller of a helical axial flow oil-gas pump   Order a copy of this article
    by Haozhi Nan, Rennian Li, Weiwei Zhou 
    Abstract: During oil and gas transportation, due to transport mixed media, phase separation is easy to occur, which reduces the efficiency of the multiphase pump and may cause 'gas blockage' in serious cases. In this paper, the self-designed single stage helical axial flow compression unit was used as the research object to explore the separation characteristics of the fluid medium in the impeller of the pump. Based on computational fluid dynamic (CFD), the Euler multiphase fluid model and the SST k-ω turbulence model were used to calculate the flow in impeller. By setting monitoring points in the flow channel, the force movement of bubbles and solid particles is analysed. The results show that the radial velocities of bubbles and solid particles suddenly change in the middle of the channel. By analysing the pressure on the impeller surface, the coincidence area and non-coincidence area are defined. The results show that in the overlapping area when λ > 0.5, GVF is basically consistent with the inlet and the maximum GVF is 0.8. In the non-overlapping area, when λ > 0.5, the maximum GVF is 1, indicating complete gas-liquid separation.
    Keywords: helical axial flow oil-gas multiphase pump; multiphase flow; separation characteristics; computational fluid dynamic; CFD.
    DOI: 10.1504/PCFD.2024.10061297
     
  • Numerical analysis on prediction and attenuation of low-speed cavity noise   Order a copy of this article
    by S. Soma Sundaram 
    Abstract: Prediction and attenuation of noise generated in the cavity with an overhang has been numerically studied. Simulations are carried out such that two-dimensional, unsteady, turbulent, compressible equations are solved. The geometry considered for the simulations is a deep cavity with an overhang. The dimensions of the cavity and the wind tunnel are obtained from literature. Unsteady pressure data has been collected from the walls of the cavity and discrete Fourier transform (DFT) analyses of these data have been carried out. The predicted frequencies are found to match with the experimentally measured values. Proper orthogonal decomposition (POD) analyses of the data collected indicate the presence of longitudinal duct mode and vortices in the shear layer. The attenuation studies have been carried out by providing a chamfer in the trailing edge. The results indicate the amplitude of the noise has been reduced by five times for a chamfer of 45°.
    Keywords: cavity with overhang; noise attenuation; numerical simulation; DFT analysis; POD analysis; hydrodynamic mode; duct mode.
    DOI: 10.1504/PCFD.2024.10061298
     
  • Investigation of upper airway changes in orthognathic surgery with computational fluid dynamics analysis   Order a copy of this article
    by Ilker Inan, Erman Aslan, Frantzeska Karkazi, Yasemin Bahar Acar, Banu Korbahti, Hasan Riza Guven 
    Abstract: In this retrospective study, computational fluid dynamics (CFD) simulation was used to observe changes in airway in a patient (20-year-old male) who underwent bimaxillary surgery with maxillary advancement and mandibular setback. Bimaxillary orthognathic surgery is an invasive approach that is used for the correction of skeletal class III malocclusion related with dental surgery. In order to perform CFD analysis, at the first stage cone-beam computed tomography (CBCT) data from preoperative (2 months before surgery) and postoperative (6 months after surgery) were used to build the numerical domain at three different volumetric flow rates of 30 L/min, 15 L/min and 7.5 L/min. In addition to volume changes in the airway, pressure drop, shear stress, streamlines were analysed for inhalation and exhalation phases at different volumetric flow rates. The total upper airway volume after the operation narrowed by 13.69% compared to the pre-operation. Upper respiratory tract nasal resistance decreased. In the post-operative condition, a pressure drop was observed between the nostrils and hypopharynx region for all volumetric flow rates. This demonstrates that the patient breathes easier after the bimaxillary orthognathic surgery operation.
    Keywords: finite volume method; FVM; turbulent flow; upper airway change; upper airway flow.
    DOI: 10.1504/PCFD.2023.10054095
     
  • Performance of different wall functions in turbulent flow inside a pipe, a diffuser and behind a backward-facing step   Order a copy of this article
    by M. Mohseni, A. Amini 
    Abstract: In this study, the performance of different wall functions and near wall treatments are investigated numerically. The near wall treatments used are divided into two categories with fine mesh and coarse mesh. The results show that in flow inside the pipe, in general, the performance of the near wall treatments with fine mesh, especially in the entrance region of the pipe, is better than the wall functions with coarse mesh. In addition, the results for the pressure coefficient at points just after the step and at the region of return flow are very different from the experimental results, but they predict the length of the reattachment with good accuracy. Moreover, the results obtained for the diffuser shows the relatively good performance of these functions for estimating the pressure coefficient, although in reproducing the velocity profiles in different sections of the channel, they have significant errors compared to the experimental values.
    Keywords: wall function; near-wall treatments; turbulent flow; pipe; step; diffuser; numerical simulation.
    DOI: 10.1504/PCFD.2023.10054194
     
  • Eliminating the residual velocity divergence of spectral methods in channel turbulence   Order a copy of this article
    by Zehao Chen, Le Fang 
    Abstract: The problem of residual velocity divergence exists in numerical simulations of channel flows which use spectral methods. The present contribution analyses the source of the residual velocity divergence, and introduce a new correction method by adding a new pressure correction substep and using ghost grids. The new method can completely eliminate the residual velocity divergence without breaking the non-slip condition. Numerical results show that the residual velocity divergence is well eliminated, while a-posteriori results are not becoming worse. We then conclude that the numerical simulations by using the present method are more close to the incompressible N-S equations, but the influence to a-posteriori statistical quantities is still worth to be investigated in the future.
    Keywords: channel turbulence; Chebyshev discretisation; spectral method; residual velocity divergence.
    DOI: 10.1504/PCFD.2024.10062357
     
  • Improving the quantification of overshooting shock-capturing oscillations   Order a copy of this article
    by Fan Zhang 
    Abstract: An approach for quantitatively evaluating overshooting oscillations is designed to characterise the performance of shock-capturing schemes. Specifically, following our previous work focused on cases with only discontinuities, now we account for the concurrent presences of discontinuities and smooth waves, each with a complete set of supported modes on a given discretisation. The linear advection equation is taken as the model equation, and a standardised measurement is given for overshooting oscillations produced by shock-capturing schemes. Thereby, we can quantitatively reveal the shock-capturing robustness of, for example, weighted essentially non-oscillatory schemes, by comparing and analysing the resulting overshoots. In particular, we are able to find out the ranges of wavenumbers in which the numerical schemes are especially prone to produce overshooting oscillations. While lower dissipation is usually anticipated for high-order schemes, we provide a simple measurement for evaluating the shock-capturing robustness, which was not trivial due to the nonlinearity of shock-capturing computations.
    Keywords: shock-capturing; overshooting oscillation; quantitative measurement; high-order scheme; finite-difference method.
    DOI: 10.1504/PCFD.2023.10060745
     
  • The effect of building layout patterns on the formation of heat islands: a computational study   Order a copy of this article
    by K. Veena, K.M. Parammasivam, T.N. Venkatesh 
    Abstract: Numerical methods are getting high acceptance worldwide for studying heat islands. As most of the existing studies have not investigated the importance of spacing between buildings, the main goal of the current study is to compare the behaviour of wind patterns and heat island formation in building clusters with less spacing and adequate spacing according to National Building Codes of India (NBC 2016). Six building layouts with a combination of high-rise and low-rise buildings are numerically studied using buoyant-Boussinesq solvers. Results show that the near-surface air temperature is higher for less spacing cases than adequate spacing cases. An air temperature higher than the threshold value (ΔT = 0.7 K) was identified at 55% of the area near the ground for less spacing sub-case. In comparison with less spacing cases, the wind velocity near the building cluster was increased by 17.7%, and the temperature spread decreased by 35.04% by following the NBC.
    Keywords: urban heat island; National Building Codes; computational fluid dynamics; near-surface air temperature; thermal comfort; wind environment; temperature distribution.
    DOI: 10.1504/PCFD.2023.10059257
     
  • Numerical investigation of the effect of swirl number on performance, combustion, and emissions characteristics in a converted heavy-duty natural gas engine   Order a copy of this article
    by Fatih Aktas 
    Abstract: In this research, the performance, combustion characteristics, and emission behaviour of a diesel engine converted to a spark ignition engine running on natural gas were investigated. The studies were performed at full load, 2,300 rpm, constant spark ignition time, and seven different swirl ratios. As a result, the homogeneous-air fuel mixture formed in the cylinder due to the swirl ratio rising, and the increased combustion performance dominated the heat loss because of the rise in the swirl number, thereby improving the performance. However, with the increase of in-cylinder temperatures, NOX emissions increased. As the swirl ratio increased from 1.2 to 2.4, the gross indicated power (GIP), indicated mean effective pressure (IMEP), indicated thermal efficiency (ITE), and maximum pressure rise rate (MPRR) values increased by 4.1, 4.13, 3.98, 102.2%, while the gross indicated specific fuel consumption (GISFC) value improved by 3.97%.
    Keywords: natural gas; heat transfer; spark ignition; diesel engine; converted engine; emissions; G-equation; swirl number; combustion; internal combustion engine.
    DOI: 10.1504/PCFD.2023.10056598
     
  • Fin effectivity investigation at solid-liquid phase change in axisymmetric heat exchangers using lattice Boltzmann method   Order a copy of this article
    by Zeinab Hajamini, Hamed Moqtaderi, Sajedeh Kebriti 
    Abstract: The purpose of this article is to analyse the fin parameters in a heat exchanger to optimise the melt rate of PCM. Shell and tube heat exchangers are considered. The shell contains PCM and annular fins placed on the tube wall. The fluid flow, heat transfer, and melting equations were solved using a 2D axisymmetric lattice Boltzmann method (LBM). LBM enthalpy-based method was developed in an axisymmetric form. According to our study of the effect of fin number and length on PCM melting rate, the optimal number of fins for thicknesses of    2𝑅  / 20 ,    2𝑅  / 40 and    2𝑅   / 200 is 3, 2, and 2, respectively, while the optimal length of fins for these thicknesses is 0.8R. Moreover, we also introduced a three-fin arrangement with uneven fin length, which increased melting rate. The effect of the secondary fin on the melting rate of PCM was also studied.
    Keywords: fin effectivity; solid-liquid phase change; lattice Boltzmann method; LBM; axisymmetric heat exchanger.
    DOI: 10.1504/PCFD.2023.10061034