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Wake Dynamics and Vortex Synchronization in Multi-Cylinder Arrays: A Computational Insight into Aerodynamic Performance and Flow Interference
(2025-11-01)
Chamoli, Sunil
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Mangrulkar, Chidanand K.
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Uniyal, Anirudh
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Bhatt, Mohit
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Joshi, Nikhil
This study presents a detailed computational investigation of unsteady laminar flow around two-dimensional square cylinders arranged in multiple configurations. Simulations were performed using ANSYS Fluent 2019 at Reynolds numbers ranging from 50 to 200, with three geometric layouts as follows: two vertically aligned cylinders, three inline cylinders, and three staggered cylinders. Center-to-center spacing ratios of 1.5D, 2.5D, and 3.5D were evaluated to assess wake interference, vortex shedding behavior, and aerodynamic force fluctuations. Results reveal that a close spacing (1.5D) causes strong wake coupling and highly irregular flow behavior, especially with inline configurations, leading to amplified drag and suppressed vortex shedding with downstream cylinders. In contrast, a staggered three-cylinder arrangement at 3.5D spacing exhibits regular vortex shedding, uniform force distribution, and minimized flow-induced oscillations, indicating aerodynamic stability. The Strouhal number, computed using FFT analysis, confirms the onset of periodic shedding at higher Reynolds numbers and highlights optimal synchronization at wider spacings. The study concludes that staggered configurations with appropriate spacing outperform inline setups in terms of flow control, dynamic stability, and reduced aerodynamic interference, offering insights relevant to high-rise building clusters and industrial heat exchanger design.
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Investigations on thermal profiles and flow structures in a square channel equipped with staggered vortex turbulators
(2024-09-01)
Boonloi, Amnart
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Lewpiriyawong, Nuttawut
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Jedsadaratanachai, Withada
Given the escalating energy demands today, improving the efficiency of engineering equipment is crucial for optimizing energy use. This study focuses on enhancing heat exchanger performance through passive methods, particularly by installing vortex turbulators. Passive techniques can effectively manage energy costs while enhancing efficiency. The research examines thermal profiles and airflow structures within a square channel heat exchanger (SCHE) equipped with staggered vortex turbulators (SVTs). SVTs feature a unique design combining rectangular winglets and V-pattern baffles. The installation of SVTs aims to intensify vortex strength, thereby increasing SCHE efficiency, convective heat transfer coefficients, and overall heat transfer potential. The study investigates the effects of SVT dimensions (b<inf>1</inf>/H and b<inf>2</inf>/H), airflow directions (+x and -x), installation patterns (pattern no. 1 and 2), pitch to height ratios (P/H = 1, 1.5, and 2), and flow attack angles (α = 20°, 30°, and 45°). Computational simulations using the finite volume method with a commercial code (FLUENT) under laminar flow conditions (Reynolds number of 100–2000) provide insights into thermal profiles, fluid temperature distributions, and flow configurations within the SCHE. Staggered arrangement and gap spacing are employed to reduce pressure loss and enhance airflow strength. The results highlight flow structures and heat transfer characteristics in the heat exchanger channels, elucidating the underlying mechanisms of the heat exchange process. Understanding these behaviors is crucial for developing more efficient heat exchangers and vortex generators in the future. Simulation findings demonstrate that SVTs significantly enhance convective heat transfer over smooth channels due to increased vortex strength. Notably, pattern no. 2 SVTs (b<inf>1</inf>/H = b<inf>2</inf>/H = 0.20) achieve the highest Nu/Nu<inf>0</inf> of 19.21 in the +x flow direction at Re = 2000, α = 30°, and P/H = 1. In conclusion, the study identifies a maximum thermal enhancement factor of 4.38. It underscores the potential of pattern no. 2 SVTs for optimizing heat exchanger performance, offering valuable insights for future developments in thermal management technologies.
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Ventilation improvement for effective protection of healthcare workers in negative pressure airborne infectious isolation room from viral aerosols
(2024-07-01)
Kaeophet, Thanchanok
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Dejchanchaiwong, Racha
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Tekasakul, Perapong
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Phonsahwat, Thongchai
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Khongprom, Parinya
A negative pressure airborne infectious isolation room (AIIR) is the primary healthcare air contamination control system used for the treatment of severe respiratory infectious patients. Effects of the ventilation system configuration and conditions on airflow pattern, aerosol distribution and ventilation performance were investigated using computational fluid dynamics (CFD). The field measurement by SARS-CoV-2 environmental surface test was also conducted. The cycle threshold values from transcription polymerase chain reaction (RT-PCR) method showed inverse relation to the simulated number of particles trapped on the surfaces indicating a good agreement. Modification of the present AIIR to have alignment between air inlet and outlet where the aspect ratio of the air outlet, Width (W): Height (H) = 1:1 (Improved case: IC#1) showed a 78 % reduction of aerosol concentration in healthcare workers (HCWs) zones. Aerosol concentrations were increased when the openings of the air outlet were enlarged. Addition of air outlet led to large swirling air, resulting in more aerosols being trapped and suspended in the air. Results suggested that AIIR with alignment air inlet on the ceiling and air outlet at the wall over the patient's head with W:H = 1:1 be the most suitable configuration to maximize the ventilation performance and minimize exposure risk to aerosolized viral infection for HCWs. Air change rate plays a more important role than the differential pressure on the removal efficiency. The differential pressure value should be at least −2.5 Pa and the air supply rate 12 ACH for effective protection of HCWs in the negative pressure AIIR.
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On the Semi-Analytical Solution of Displacement Thickness in a Laminar Streamwise Corner Flow Assisted by Computational Fluid Dynamics Simulation
(2023-01-01)
Bumrungthaichaichan, Eakarach
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Unaprom, Prajaree
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Sathianchok, Pakapong
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Wattananusorn, Santi
In this paper, the new semi-analytical correlation for displacement thickness of laminar fluid flow along an arbitrary-angle corner formed by the intersection of two plates has been proposed because of the discrepancy in displacement thickness for strong interference corner between the present computational fluid dynamics simulation and previous analytical correlation.
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NUMERICAL STUDY AND DESIGN OF SIDE-DIFFUSERS FOR FORMULA-SAE CAR
(2022-03-31)
Chatpattanasiri, C.
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Bunpapong, K.
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Sahastharachai, M.
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Puangkird, B.
This research focuses on designing side-diffusers for Formula Student race car. The aim is to reduce the lap time in a circular track called Skid-pad event by mean of increasing downforce generated by the diffusers, a ground effect aerodynamic device. Utilizing three-dimensional CFD simulation via cloud computing to obtain the most optimal design among the studied parameters. The study employs SST k-omega turbulence model with an incompressible flow and isothermal assumptions and the CFD model is validated via wind tunnel testing. Finally, the results show that the optimal outlet angle of 32 degrees due to the behavior vortex above the diffuser and the higher the outlet to inlet height, the lesser downforce.
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TWO-DIMENSIONAL AXISYMMETRIC NUMERICAL STUDY OF THE PREMIXED COMBUSTION INSIDE THE POROUS MEDIA BURNER
(2021-01-04)
Vithean, K.
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Charoensuk, J.
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Hanamura, K.
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Sesuk, T.
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Lilavivant, V.
Porous media combustion is one of the most efficient and has a wide-ranging application. Despite this, more investigation needs to be done in order to improve its efficiency and pollutant emission. In this research, the commercial simulation software is used to model and couple together the significant phenomena such as combustion, heat transfer, and fluid flow in porous media, which occur in this type of system. The free and porous media flow module was used to estimate fluid flow inside both fluid and porous media. Species formation and heat release during combustion were modeled by the transport of concentrated species module. Local thermal equilibrium was assumed for the energy equation and calculated by heat transfer in porous media module. Each physic was coupled together by two mechanisms—first, reaction flow, which coupled together between free and porous media flow and transport of concentrated species. Finally, nonisothermal flow coupled free and porous media flow with heat transfer in porous media. The combustion chamber, which is entirely filled with aluminum oxide pellets, is created for two dimensional axisymmetric. Physics-controlled mesh with finer element size is applied to generate mesh by the software to meet the specified need for each physic. Combustion behavior, velocity and temperature profile, and species formation are achieved from this simulation study.
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CFD Simulations of High Efficiency Gas Cyclones: An Influence of Dustbin Geometry
(2021-01-01)
Pechmanee, Pitiwat
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Namkanisorn, Apinan
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Wattananusorn, Santi
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Bumrungthaichaichan, Eakarach
The unsteady state simulation of gas-solid cyclone separator was carried out to investigate the performances of 0.29 m diameter (D<inf>B</inf>) cyclones with five different dustbin geometries, including dustbin without dipleg (cylindrical bin) and dustbins with 0.5D<inf>B</inf>, 1.0D<inf>B</inf>, 1.5D<inf>B</inf>, and 2.0D<inf>B</inf> (divergent conical bin) height divergent conical diplegs. The diameter and total height of five dustbins were 1D<inf>B</inf> and 2D<inf>B</inf>, respectively. The gas flow and turbulence fields inside the cyclones with the Reynolds number of 280,000 were simulated by Reynolds averaged Navier-Stokes equations (RANS) with Reynolds stress model (RSM). The collection efficiencies were investigated by using discrete phase model (DPM). For model validation, the simulated velocity profiles of the cyclone with cylindrical dustbin have been compared to the previous experimental data available in literature and were in good agreement with the previous results. Further, the simulated results revealed that the Stairmand cyclone with divergent conical and simple cylindrical dustbins respectively represented the highest and lowest collection efficiencies indicated by 50% cut-off diameter, which corresponded to the diameters of 1.692 and 1.744 microns, respectively.
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CFD based Improvement of Thai Irrigation Pump
(2020-08-31)
Wasinarom, Kittipass
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Boonchauy, Dachdanai
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Charoensuk, Jarruwat
Evaluation phase which was partial fulfilment of the beginning phase of "Development of Performance test rig and Efficiency improvement of impeller in Thai irrigation pump project" is presented in this paper. Overall flow field in the pump system that consisted of inlet, impeller and stator vane of the available pump was analyzed using commercial Computational Fluid Dynamics (CFD) code. The goal of this investigation is to obtain more understanding of energy dissipation which results from shear stress that developed within the flow field in each section of the pump. The improvement measure is then conducted with the concern of manufacturing difficulties. High dissipation flow structure was observed around the impeller outlet. Jet-wake and recirculation flow were observed. The first improvement measure was conducted by adding the bluff body in the flow channel to alleviate jet-wake structure and delay flow separation. After the implementation of the optimized bluff body around the impeller exit, CFD results indicated around 3-8% improvement compared with the CFD results of the available pump for the entire range of operating conditions.
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A review of air pollution and solutions way management related to ribbed smoked sheets (RSS) production of community-level rubber cooperatives in thailand: Smoke, soot and PAHs particles
(2020-06-01)
Kalasee, W.
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Teekapakvisit, C.
In Thailand, RSS chamber of community-level rubber cooperatives can be classified into two models: old and new model, named after the years of their establishment. Hot gas as a heat supply from Para-rubber (PR) wood (Hevea brasiliensis) combustion is used for removing moisture from the natural rubber (NR) sheets. Smoke and soot particles from PR wood burning has effected to the quality of the NR sheet and the pollution in the workplace area and lead to health problems of the worker. Cascade impactors are equipment for measuring the smoke and soot particles size distribution from PR wood combustion. PAHs compounds from PR wood combustion were found 15 different PAHs components (Tekasakul et al., 2005; Furuuchi et al., 2006). Important methods in decreasing smoke and soot particles from combustion of PR wood for rubber smoking chamber are separation equipment and ventilation designed by computational fluid dynamics (CFD) technique. In this article, the separation method is focused on smoke and soot particle collection to maintain the quality of the NR sheet. This equipment is reviewed both indoor and outdoor, for example, an impaction wall, electrostatic precipitator, stainless-wire, etc. This review indicates that the ESP installing between the furnace and the smoking chamber is suitable to eliminate aerosol particles at the rubber smoking industry. In addition, CFD technique reports is aimed at collecting aerosol particles for decreasing smoke and soot particles emission from rubber smoking chamber is presented.
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Experimental and numerical characterization of airflow in a closed refrigerated display cabinet using PIV and CFD techniques
(2020-03-01)
Chaomuang, Nattawut
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Flick, Denis
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Denis, Alain
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Laguerre, Onrawee
Air velocity measurements were carried out using the Particle Image Velocimetry (PIV) technique in a display cabinet under two configurations: closed and open doors. Two conditions (refrigeration system turned “on” and turned “off”) were studied in the closed configuration. The airflow pattern was almost the same for both conditions. The air curtain was quite stable. In the upper part of the cabinet, air recirculation occurred, and this phenomenon induces external air infiltration through the door gaps. The air curtain in the open configuration (refrigeration system turned “off”) was less stable than the closed configuration. Large unsteady eddies developed in the mixing layers, thereby promoting greater external air infiltration. A two-dimensional computational fluid dynamic (2D-CFD) model was developed and showed the ability to reproduce the main flow phenomena observed in the experiment. The trend of predicted product temperature profile was also in agreement with the experimental values, despite slight underestimation.

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