Browsing by Subject "Computational fluid dynamics"

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Accelerated 3D CFD modeling of multichannel flat grooved heat pipes
(Elsevier, 2024-10-01) Gökçe, Gökay; Çetin, Barbaros; Dursunkaya, Zafer
Flat grooved heat pipes (HPs) have become essential in advanced thermal management solutions across various engineering applications. Modeling these devices, especially multichannel flat grooved HPs, involves significant challenges due to complex phenomena such as phase-change heat transfer and free-surface flow, requiring substantial computational resources, time and expertise. These constraints often limit the full exploration and optimization of HPs’ potential in diverse applications. To address this gap, an accelerated 3D computational fluid dynamics (CFD) modeling approach is presented in this study. This novel method begins with a detailed 3D modeling of a single groove, developed using kinetic theory and facilitated by CFD software. The results from this model are then applied as boundary conditions to simulate the entire HP in a multichannel configuration. The importance of this methodology is further highlighted by the alignment of simulation results with experimental observations. The approach significantly enhances computational efficiency by reducing the number of iterations by 10% and computational time by 80%, resulting in a five-fold speed-up. The methodology enables accelerated, comprehensive modeling of multichannel variations and delivers critical insights for optimizing the design of multichannel flat grooved HPs for various engineering applications.
Open Access
Finite element modeling of micro-particle separation using ultrasonic standing waves
(ASME, 2014) Büyükkoçak, S.; Çetin, Barbaros; Özer, M. B.
Acoustophoresis which means separation of particles and cells using acoustic waves is becoming an intensive research subject. The method is based on inducing an ultrasonic compression standing wave inside a microchannel. A finite element approach is used to model the acoustic and electro-mechanical behavior of the piezoelectric material, the micro-channel geometry as well as the fluid inside the channel. The choices of silicon and PDMS materials are investigated as the chip materials for the resonator. A separation channel geometry which is commonly used in the literature is implemented in this study and the fluid flow inside the microchannel geometry is simulated using computational fluid dynamics. The acoustic field inside the fluid channel is also be simulated using the finite element method. For the separation process to be successful micro-particles of different diameter groups should end up in different channels of the micro-separator. In order to simulate real life scenarios, each particle size group have a size distribution within themselves. For realistic simulation results the particles will be released into the micro separator from a different starting locations (starting location distribution). The results of this Monte-Carlo based finite element simulation approach will be compared with the reported experimental results.
Open Access
Modeling interaction of fluid, fabric, and rigid objects for computer graphics
(IEEE, 2006) Bayraktar, Serkan; Güdükbay, Uğur; Özgüç, Bülent
Simulating every day phenomena such as fluid, rigid objects, or cloth and their interaction has been a challenge for the computer graphics community for decades. In this article techniques to model such interactions are explained briefly and some of the result of applying these tecniques are presented. © 2006 IEEE.
Open Access
Modelling a janus particle activated by an optical potential
(2023-09) Rauf, Umar
The flow around a Janus particle under an optical potential is investigated. The thermal effects are majorly overlooked while studying the Janus particle although fluid heating caused by optical potential might negligible but the fluid heating caused due to Janus particle acting as a heating source is not negligible. The stream function approach is used to model the behavior of an activated Janus particle. The explicit finite difference method (FDM) is used to numerically obtain the solution. BIL-FLOW, an in-house FDM code is developed and validated for flow around a Janus particle under an optical potential. Additionally, The BIL-OP, an in-house optical module based on geometric ray approximation is developed and validated. BIL-OP utilizes linear algebra to calculate three dimensional (3D) optical force.
Open Access
On the performance of linear least-squares estimation in wireless positioning systems
(IEEE, 2008-05) Gezici, Sinan; Güvenç, İ.; Sahinoğlu, Z.
A common technique for wireless positioning is to estimate time-of-arrivals (TOAs) of signals traveling between a target node and a number of reference nodes, and then to determine the position of the target node based on those TOA parameters. In determining the position of the target node from TOA parameters, linear or nonlinear least-squares (LS) estimation techniques can be employed. Although the linear LS techniques are suboptimal in general, they facilitate low-complexity position estimation. In this paper, performance of various linear LS techniques are compared, and suboptimality of the linear approach is quantified in terms of the Cramer-Rao lower bound (CRLB). Simulations are performed to compare the performance of the linear LS approaches versus the CRLBs for linear and nonlinear techniques. ©2008 IEEE.
Open Access
Simulation of an integrated microfluidic device for bioparticle wash, separation and concentration
(American Society of Mechanical Engineers (ASME), 2013) Çetin, Barbaros; Büyükkoçak, S.; Zeinali, Soheila; Özer, B.
Washing, separation and concentration of bioparticles are key operations for many biological and chemical analyses. In this study, the simulation of an integrated microfluidic device is studied. The proposed device has the capability to wash the bioparticles (transferring the bioparticles from one buffer solution to another), to separate the particles based on their dielectric properties and to concentrate the bioparticles. Washing and concentration of bioparticles are performed by acoustophoresis and the separation is performed by dielectrophoresis. For simulating the flow within the microchannel, a computational fluid dynamics model using COMSOL Multiphysics software is implemented. In order to simulate the particle trajectories under ultrasonic and electric field, point-particle assumption is chosen using MATLAB software. To account for the size variation of the bioparticles, particles with normal size distributions are used in-side the microchannel. The effect of the key design parameters such as flow rate, applied voltage etc. on the performance of the device is discussed. Copyright © 2013 by ASME.