Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/46

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Now showing 1 - 20 of 463

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Development and 3D spatial calibration of a parallel robot for percutaneous needle procedures with 2D ultrasound guidance
(World Scientific, 2017-12-01) Ahmad, Mirza Awais; Orhan, Sabri Orçun; Yıldırım, Mehmet Can; Bebek, Özkan; Mechanical Engineering; BEBEK, Özkan; Ahmad, Mirza Awais; Orhan, Sabri Orçun; Yıldırım, Mehmet Can
Robotic systems are being applied to medical interventions as they increase the operational accuracy. The proposed autonomous and ultrasound guided 5-DOF parallel robot can achieve such accuracy for needle biopsies, which particularly demand precise needle positioning and insertion. In this paper, the robot's mechanical design, system identifications, and the design of its controller are explained. A torque computed controller with gravity compensation and friction models, yielding a 0.678mm RMS position error for the needle tip, was used. A novel method was used for 3D space calibration of the images for detecting the volume of interest in the biopsy procedure by a multipoint crosswire phantom with parallel threads. The calibration technique had a validation RMS error of 0.03mm.
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An integrated design approach for a series elastic actuator: Stiffness formulation, fatigue analysis, thermal management
(IEEE, 2017-12-22) Yıldırım, Mehmet Can; Şendur, Polat; Bilgin, Onur; Gülek, Berk; Yapıcı, Güney Güven; Uğurlu, Regaip Barkan; Mechanical Engineering; YAPICI, Güney Güven; UĞURLU, Regaip Barkan; ŞENDUR, Polat; Yıldırım, Mehmet Can; Bilgin, Onur; Gülek, Berk
This paper presents an integrated mechanical design approach for the long-Term and repetitive use of series elastic actuators (SEAs). Already, computational models for series elastic actuator design have been developed in order to address the challenging weight and volume targets. However, an integrated design method in which the coupling effects between various interacting requirements that are explored at every stage of the design cycle does not exist. In particular, the interactions between the torsional stiffness, strength, fatigue life and thermal performance are not analyzed in-depth. To this end, we propose a comprehensive design approach in which the aforementioned requirements (FEA, stiffness formulation, fatigue analysis, and thermal management) are integrated in a complementary manner. Computer-Aided analyses and experimental results verified the effectiveness of our design approach. The proposed approach is employed to manufacture our SEA module CoEx-SEA.
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Free simulation software and library
(Springer, 2018-01-01) Uğurlu, Regaip Barkan; Ivaldi, S.; Mechanical Engineering; UĞURLU, Regaip Barkan
With the advent of powerful computation technologies and efficient algorithms, simulators became an important tool in most engineering areas. The field of humanoid robotics is no exception; there have been numerous simulation tools developed over the last two decades to foster research and development activities. With this in mind, this chapter is written to introduce and discuss the current-day open-source simulators that are actively used in the field. Using a developer-based feedback, we provide an outline regarding the specific features and capabilities of the open-source simulators, with a special emphasis on how they correspond to recent research trends in humanoid robotics. The discussion is centered around the contemporary requirements in humanoid simulation technologies with regard to the future of the field.
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Flow visualization and LES simulations inside a chevron type plate heat exchanger
(Begell House Inc., 2018) Peçenek, Erdem; Ertunç, Özgür; Senkal, C.; Mechanical Engineering; ERTUNÇ, Özgür
An up-scaled model of a single channel of CPHE was used under dynamically similar conditions for the experiments. In experiments, pressure drop measurements and flow visualizations were conducted with aluminum flitter and dye. For the numerical study, large eddy simulations are preferred in the turbulent regime which has the best fit with experiments. Also mixing inside the channel is analyzed and reported through numerical simulations. Results of this study exhibit flow structures differ from previous visualization studies with corrugated channels. The numerical results exhibit that LES estimates friction factor at high Reynolds numbers with maximum 5% error. Numerical visualizations are close the experimental visualizations in the study. Lastly mixing study exhibits that there is asymmetric mixing inside the channel.
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A high-torque density compliant actuator design for physical robot environment interaction
(IEEE, 2020) Dunwoodie, E.; Mutlu, R.; Uğurlu, Regaip Barkan; Yıldırım, Mehmet Can; Uzunovic, T.; Sariyildiz, E.; Mechanical Engineering; UĞURLU, Regaip Barkan; Yıldırım, Mehmet Can
Compared to the traditional industrial robots that use rigid actuators, the advanced robotic systems are mobile and physically interact with unknown and dynamic environments. Therefore, they need intrinsically safe and compact actuators. In the last two decades, Series Elastic Actuators (SEAs) have been one of the most popular compliant actuators in advanced robotic applications due to their intrinsically safe and compact mechanical structures. The mobility and functionality of the advanced robotic systems are highly related to the torque-density of their actuators. For example, the amount of assistance an exoskeleton robot can provide is determined by the trade-off between the weight and output-torque, i.e., torque-density, of its actuators. As the torque outputs of the actuators are increased, the exoskeleton can expand its capacity yet it generally becomes heavier and bulkier. This has significant impact on the mobility of the advanced robotic systems. Therefore, it is essential to design light-weight actuators which can provide high-output torque. However, this still remains a big challenge in engineering. To this end, this paper proposes a high-torque density SEA for physical robot environment interaction (pREI) applications. The continuous (peak) output-torque of the proposed compliant actuator is 147Nm (467 Nm) and its weight is less than 2.5kg. It is shown that the weight can be lessened to 1.74, but it comes at cost. The performance of the proposed compliant actuator is experimentally verified.
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Numerical analysis of solar radiation effects at indoors with internal partitions and external solar shades
(International Solar Energy Society, 2020) Yelekci, Ali Can; Keskin, Cem; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar; Yelekci, Ali Can; Keskin, Cem
A numerical study is conducted to couple natural convection in an office space with thermal radiation due to solar radiation. The study specifically investigates the effect of partitions located between desks of the office space to develop a tool-box to determine the effect of windows on thermal and visual comfort of occupants. Three different partition cases (according to the aspect ratio of the partition to the ceiling height, which are 0.3, 0.5 and 1.0) were studied. Moreover, the effects of different designs of solar shades in front of windows were investigated. All walls other than the facade of the enclosure are assumed adiabatic, and the enclosure has a single window, which acts as a thermal radiative heat source. All surfaces are assumed to be gray-diffuse surfaces for calculation of thermal radiation. The solar radiation is analyzed for a perfect sunny day with both diffuse and direct sunlight, and for an overcast day with only diffuse sunlight. Based on the choice of partitions geometry, solar shade aspect ratios and the weather conditions, variations on the surface temperature distribution inside the office are analyzed.
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Computational and experimental investigation of vibration characteristics of variable unit-cell gyroid structures
(International Center for Numerical Methods in Engineering, 2019) Şimşek, Uğur; Gayir, C.; Kavas, B.; Şendur, Polat; Mechanical Engineering; ŞENDUR, Polat; Şimşek, Uğur
Triply periodic minimal surface (TPMS) based geometries exhibit extraordinary mechanical, thermal, electrical and acoustic properties thanks to their unique topologies. There are various types of structures in the TPMS family. One of the most well-known TPMS structures is the gyroid structure. This paper focuses on the vibrational behavior of a novel sandwiched gyroid structure in terms of their natural frequencies and mode shapes with three different feasible unit sizes at same volume ratio. Powder bed fusion technology is employed to fabricate gyroid porous specimens made of HS188 material. Modal testing is performed to deduce the vibration characteristics of aforementioned cellular structures. Besides the experimental study, the dynamic performance of the considered structures is investigated computationally by performing modal analysis using Finite Element (FE) models. A key challenge facing FE modelling of large scale gyroid structure is computation time and accuracy. For that reason, small size of gyroid lattices are utilized for compression tests in order to extract elastic properties. Then sandwiched gyroid plate is modelled as solid body with calculated elastic properties instead of complex gyroid topology and analyzed. Finally correlation level between experimental and FE results are presented.
Open Access
The effect of interface gradient distribution on unrealistic flow in 3D droplet simulations
(Europe, Institute for Liquid Atomization and Spray Systems, ILASS, 2021-08-31) Yılmaz, Anıl; Kayansalçik, Gökhan; Ertunç, Özgür; Mechanical Engineering; ERTUNÇ, Özgür; Yılmaz, Anıl; Kayansalçik, Gökhan
The purpose of this study is to investigate the origin of the parasitic current to provide accurate prediction of droplet surface interactions in Volume of Fluid (VOF) framework. The deformation of the droplet due to parasitic current has been the most important problem in 3D simulations. Parasitic current is influenced by curvature and surface normal estimation in the Continuum Surface Force (CSF) model. It has been shown that the number of neighboring cells of the central cell influences the gradient calculations regarding the generation of parasitic current. It has been observed that the polyhedral cell structure delivers a smoother interface gradient distribution than the cartesian cell structure. To examine the dynamics in different physical conditions, we compared simulations with base experiments to understand whether those models work. We then simulated droplet cases on stationary and moving wall conditions, and simulation results were consistent with experimental results.
Open Access
Validation and comparison of 2D and 3D numerical simulations of flow in simplex nozzles
(Europe, Institute for Liquid Atomization and Spray Systems, ILASS, 2021-08-31) Bal, M.; Kayansalçik, Gökhan; Ertunç, Özgür; Böke, Y. E.; Mechanical Engineering; ERTUNÇ, Özgür; Kayansalçik, Gökhan
Numerical simulations of pressure swirl atomizers are computationally expensive due to transient and multiphase flow behavior. In this study, 2D and 3D VOF simulations are performed for a geomerty which has high swirl chamber length-to-diameter ratio of 1.33. discharge coefficient (CD) and spray angle values are compared to the experimental data. Moreover, a benchmark study is conducted between 2D and 3D methods in terms of accuracy, computational cost and flow variables such as orifice exit axial and tangential velocity. The simulations are performed using a hybrid RANS-LES approach, IDDES model. It is observed that 2D simulation has lower accuracy in the validation parameters such as discharge coefficient and spray angle as compared to the 3D simulation. The main reason for 2D simulation inaccuracy might be the tangential port inlet effects and wrong estimation of the loss of swirl inside the swirl chamber. On the other hand, 2D simulations have approximately 1000 times lower computational cost than 3D simulations.
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Design and development of a torsion-based series elastic actuator with nested encoders for a wearable exoskeleton robot
(IEEE, 2022) Kuru, Alihan; Uğurlu, Regaip Barkan; Bebek, Özkan; Mechanical Engineering; UĞURLU, Regaip Barkan; BEBEK, Özkan; Kuru, Alihan
This paper presents the design of a high torque-to-mass ratio series elastic actuator (SEA) for wearable powered exoskeletons. Nonbackdrivable actuators are ideal for applications that require high torque. Commonly, active exoskeleton robots are powered by actuators that are nonbackdrivable. Due to the high gear ratio, the output mechanical impedance of these actuators is quiet high which renders their force/torque control challenging. To provide torque controllability a custom torsional spring has been produced and placed at the output side of the series elastic actuator. In addition, the measurement of the angular displacement of this elastic element is challenging in terms of mechanical design. To prevent this design challenge a double shaft mechanism was proposed. In this mechanism, the first shaft, which connects the spring and the spring encoder, goes through the second shaft, which is connected to the motor and the motor encoder. This way both encoders are placed on a the same side of the SEA. In addition to explaining this compact spring shaft mechanism, this article presents the results of the cascaded PID controller with a disturbance observer (DoB) applied on the actuator.
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Topology optimization-based design and development of a compact actuator with a high torque-to-weight ratio for quadrupeds
(IEEE, 2022) Akın, Barış; Özçınar, Erim Can; Balcı, Barış; Emre, Sinan; Şendur, Polat; Bebek, Özkan; Ünal, Ramazan; Uğurlu, Regaip Barkan; Mechanical Engineering; ŞENDUR, Polat; BEBEK, Özkan; ÜNAL, Ramazan; UĞURLU, Regaip Barkan
This paper presents the design, development, and testing procedures for a compact actuator with a high torque-to-weight ratio, generally aimed to actuate legged robots, e.g., quadrupeds. The main goal of designing the actuator was to keep its total weight minimum while ensuring a high torque output. Therefore, the following design steps were implemented: i) the actuator was designed in accordance with the torque output requirement and the stress distribution that was mapped on actuator frames, ii) topology optimization was conducted on the initial design and it is modified in accordance with optimization results, and iii) the optima actuator design was built and tested on in a realistic scenario in which it powered an actual quadruped robot for validation. As the result, the proposed actuators could track the desired walking trajectory with a relatively low error. In conclusion, continuous torque output of 48 Nm was obtained via a lightweight (1.6-1.7 kg) actuator design.
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Automated flow rate control of extrusion for 3D concrete printing incorporating rheological parameters
(Elsevier, 2024-04) Ahi, Oğulcan; Ertunç, Özgür; Bundur, Zeynep Başaran; Bebek, Özkan; Civil Engineering; Mechanical Engineering; ERTUNÇ, Özgür; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Ahi, Oğulcan
The use of inline quality assessment technologies is of great importance in meeting the consistent extrusion requirements of 3D concrete printing (3DCP) applications. This paper presents a system to regulate extrusion speed and maintain the flow rate at a target value during 3DCP processes. The system is based on a new equation that combines printing parameters and the material's rheological properties in the printing process. The proposed control strategy is designed to effectively function with various cement-based mixtures. Validation tests demonstrate that the proposed system can maintain an instantaneous flow rate within a certain range and eventually achieve a constant flow rate. During operation, the flow rate is consistently maintained around the targeted value with an average error rate of 6.7 percent. The flow rate control mechanism shows promise as a reliable and efficient solution for achieving precise and constant flow rates, regardless of the cement mix design used.
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Microstructural examination of black seawater mixed sulfate-resistant cement concrete
(ASCE, 2024-01-01) Aydoǧan, O. G.; Akca, A. H.; Bilici, S.; Öztürk, Hande; Dilber, A. A.; Özyurt, N.; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk
The use of seawater as the mix water has been thought to be inevitable for the near future as a result of increasing water scarcity. Hundreds of papers related to seawater mixed cement-based materials were published in recent years. Even though sulfate-resistant cement can be beneficial for internal sulfate attack and binding chloride ions, there is no related study on the sulfate-resistant cement together with seawater. In this study, the microstructure of seawater mixed sulfate-resistant pozzolanic cement was studied for the first time to understand possible reactions. Tap water and seawater mixes were designed by using Portland cement and sulfate-resistant cement with and without fibers. To examine the effect of seawater as the mix water on the microstructure quantitatively and to construct bridge between mechanical properties and microstructure, Rietveld refinements were performed on the obtained X-ray diffraction patterns. Thermogravimetric analyses were also carried out to correctly interpret and verify X-ray diffraction data. The possibility of internal sulfate attack, possible reactions and resulting hydration products were discussed. The results showed that internal sulfate attack is not a threat for seawater mixed concrete and sulfate-resistant cement can be a better alternative than portland cement owing to more chloride binding ability for seawater-mixed concretes.
Open Access
Numerical analysis and diffuser vane shape optimization of a radial compressor with the open-source software su2
(Turk Isi Bilimi ve Teknigi Dernegi, 2023) Uzuner, Mustafa Kürşat; Başol, Altuğ Melik; Mischo, B.; Jenny, P.; Mechanical Engineering; BAŞOL, Altuğ Melik; Uzuner, Mustafa Kürşat
In recent years, the usage of open-source computational fluid dynamics tools is on a rise both in industry and academia. SU2 is one of these open-source tools. Unlike other open-source alternatives, SU2 is equipped with boundary condition types, solvers and methods that are especially developed for the analysis and design of turbomachinery. The aim of this work is to explore and investigate the capabilities of SU2 in the prediction of performance parameters of radial compressors. Two different single stage shrouded compressor geometries, one with a vaneless diffuser and the other with a vaned diffuser have been investigated with steady state CFD. The compressors were designed by MAN Energy Solutions Schweiz AG. Computational results with SU2 showed a satisfactory agreement with both the experimental data and reference CFD solutions obtained with Fidelity Flow, which is formerly known as Numeca Fine TURBO. Only at the relatively higher mass flow rates the difference between references and SU2 were higher compared to other operating points. After performance parameters were successfully calculated with SU2, the optimization tools that come with SU2 were also used. A 2D adjoint optimization study on the vane of the vaned diffuser was carried out. The study was carried out at a single operating point that is close to choke conditions. The loss generated by the large separated flow region at the suction side of the diffuser vane was reduced by 0.55 % in the optimized geometry using minimal modifications on the existing vane geometry to keep the performance of the compressor intact at other operating points. However, the resulting modification increased the total pressure loss by 0.86 % at one of the design operating points. This performance penalty could be due to the discontinuity in the vane geometry generated by the optimizer. Overall, the study shows that SU2 has the basic numerical schemes and models that are required for the analysis of radial turbomachinery flows and geometry optimization.
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Reducing charging costs for electric vehicles with bi-directional charging
(IEEE, 2023) Zincircioğlu, Emircan; Bebek, Özkan; Mechanical Engineering; BEBEK, Özkan; Zincircioğlu, Emircan
Electric vehicles (EVs) have gained popularity as eco-friendly and energy-efficient modes of transportation. How-ever, the high cost of charging infrastructure remains a significant barrier to the widespread adoption of EVs. Bidirectional charging (BDC) is a promising solution that allows EVs to charge from the grid and supply excess power back to the grid. In this paper, we present a simulation-based study of BDC using MATLAB/Simulink and Simscape to explore the potential of BDC to reduce charging costs. We modeled an EV charging station equipped with BDC capabilities and evaluated the cost savings achieved through BDC under two different scenarios. Our findings suggest that BDC has the potential to reduce charging costs significantly, making EVs more economically viable.
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Growth of NGVs and comparative study of cylinder material for CNG storage
(Springer, 2023) Azeem, M.; Haji Ya, H.; Azad Alam, M.; Sadique, M. R.; Mustapha, M. B.; Akmar Bin Mokhtar, A.; Ahmed, Tauseef; Sultan, M. T. H.; Khan, R.; Ahmed, Tauseef
In the present paper, the growth of Natural Gas Vehicles (NGVs) and the various pressure vessels used for storing compressed natural gas (CNG) is discussed.Also, the comparison of Von-mises stress in pressure vessels (PVs) due to internal pressure with different materials has been investigated numerically.Substantial use of natural gas is recorded as an alternative fuel, and the high-pressure storage of natural gas has resulted in using various types of cylinders in automobiles.Metal cylinders are extensively used in NGVs and are fabricated with different materials to satisfy services, safety and related factors.Metals and their alloys are often employed to make type I cylinders.It is important to calculate the failure pressure limit for a particular geometry of the tank against the yield strength of the material in case of metallic cylinders. An axisymmetric finite element model was made using the ABAQUS finite element platform to mimic the stress levels for two materials, viz steel alloy, and an aluminium alloy.The internal test pressure and geometric details of the cylinder were kept constant.The yield stress of material and numerical results have been compared.It was found that the steel alloy has outperformed the aluminium alloy for the given thickness of the cylinder.In contrast, the aluminium alloy failed to sustain the test pressure of 25 MPa.
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Numerical study of the intensification of single-phase heat transfer in a sandwich-like channel using staggered miniature-pin fins
(Taylor & Francis, 2023-04) Gemici, Z.; Budaklı, Mete
This study presents the numerical analysis of single-phase forced convection heat transfer and pressure drop during internal flow in a shallow, rectangular sandwich-like copper channel heated from both the top and the bottom. Simulations were conducted using a commercial finite volume solver that solves governing continuity, momentum, and energy equations simultaneously. The bottom side of the channel was considered with arrays of rectangular miniature-pin fins. The miniature-pin fin geometry was modeled in a staggered configuration with tip clearance from the opposite surface while the orientation of the fins was directed parallel to the flow direction of the working fluid. Water was used as a working fluid with a fully developed velocity profile at the channel entry. Simulations were carried out for varying inlet temperatures and mass flow rates. All calculations were performed with the RNG k-ε model to model complex turbulent flows appropriately. Grid independence and validation analyses were also conducted. With the validated model, additional analyses were performed for 0, 0.1, 0.3, 0.6, and 1 mm tip clearances, and correlations were proposed after performing regression analyses for the friction factor and heat transfer coefficient. The calculations revealed that in contrast to a straight (nonfinned) surface, up to 220% larger heat transfer coefficients could be obtained for the finned surfaces under comparable operating conditions. It was also shown that tip clearance in turbulent flow affects heat transfer negatively. With increasing clearance, the Nusselt number decreased; in other words, heat transfer worsened. On the other hand, the use of miniature-pin fins led to a rise in the pressure drop over the entire heated length. For the Reynolds number spectrum of 4000–20000, the ratio of the friction coefficient of the finned surface to the friction coefficient of the nonfinned surface varied from 6 to 5 while with a further reduction in pressure loss a value of approximately 4 could be obtained for larger tip clearances. Hence, with larger tip clearances, the friction factor decreased, reflecting the abatement of pressure loss.
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Impact of oxidation on pool boiling heat transfer performance over flat plates exposed to extended operating conditions
(IEEE, 2023) Emir, Tolga; Budaklı, Mete; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet; Emir, Tolga; Budaklı, Mete
Phase change heat transfer is utilized in a number of high heat flux applications. In order to ensure reliable functionality at moderate temperatures, one has to guarantee a stable long-term operation. In this experimental study, boiling heat transfer (BHT) performances of several substrates under continuous operation at pre-determined heat fluxes were studied. Tests were performed on bare copper surfaces in saturated deionized (DI) water and HFE-7100 under atmospheric conditions. Measurements were conducted at heat fluxes of 30 W/cm2 and 60 W/cm2 for DI water, whereas at 6 W/cm2 and 12 W/cm2 for HFE-7100. In order to identify the temporal change in surface conditions for each substrate, subsequently repeated heating tests were conducted before a 24-hour operation at constant heat flux. Besides the computation of heat transfer coefficients, contact angle (CA) measurements, high-resolution microscopic images, and scanning electron microscope (SEM) analyses were carried out to characterize the impact over surfaces. Microscopic images showed that the use of DI water leads to an intensified oxidization on the test surface. HFE-7100 does not allow oxide layer formation on the copper surfaces. Critical heat flux (CHF) at the surface operated only at 60 W/cm2 in DI water increased, while the boiling curves shifted to the left by decreasing surface temperatures over time. The surfaces immersed in HFE-7100 showed a great consistency with preliminary tests on heat transfer and repeatability tests.
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Saturated and superheated water vapor condensation on a custom micro-textured surface
(IEEE, 2023) Budaklı, Mete; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet
Condensation has a great importance for a large number of technologies such as heat exchangers, distillation columns, heat pipes, and thermal management systems. Vapor changes its phase into liquid when it contacts a surface exhibiting a lower temperature than the saturation temperature of the vapor for a given pressure. In most of those cases, systems are designed in order to achieve the phase-change process at saturated conditions over the entire heat transfer area. However, in some devices, there are sections over which prior the actual condensation occurs, the vapor flows at superheated conditions and needs to be cooled down to saturation. Thereby, one can expect that the heat transfer performance is low and the mode of condensation far away from that of saturated vapor. In this work, heat transfer and wetting characteristics during water vapor condensation at saturated and superheated conditions has been experimentally studied over a certain range of pressure and temperature. Two latter parameters were varied from 1.02 to 1.40 bar and 100{circ} mathrm{C} to 125{circ} mathrm{C}. The phase-change phenomenon has been realized on an unstructured reference surface as well as on a hexagonally micro-structured surface which was produced by laser-manufacturing. High-speed imaging technique and high-resolution temperature measurements have been adopted in order to identify the wetting behavior of the liquid on the surface and the heat transfer rate during condensation, respectively. The experiments revealed that vapor condensation on an unstructured surface at saturated conditions follows the trend of the well-known Nusselt theory for film-wise condensation. It is observed that an excess of 40 % larger heat transfer coefficients than those predicted by the Nusselt theory was achieved, and heat transfer coefficients (HTC) decrease with increasing vapor-to-surface temperature difference (T-{V}-Ts) from 4 to 24 K for both, unstructured and the micro-structured surface. In contrast, at comparable operating conditions (1.10 bar), the heat transfer coefficient for superheated (110°C) vapor condensation is remarkably lower than those for saturated vapor (sim 100{circ} mathrm{C}) and describes a considerably distinct trend. The HTC first sharply increases starting at T-{V}-T-{S}=12 mathrm{K} and shows a decreasing gradient up to a T-{V}-T-{S} text{of}22.5 mathrm{K}.
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Direct numerical simulation of synthetic jet coupled to forced convection cooling in a channel flow
(IEEE, 2023) Azarifar, M.; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet
A synthetic jet (SJ) is a microfluidic device that uses the 'zero-net-mass-flux' concept to create a compact cooling solution and provide a net positive momentum flux to the local environment. SJs have been studied extensively for natural convection heat transfer, but there is a limited data available for SJs in cross flow regimes. This paper presents results based on direct numerical simulation of a SJ in a confined heat transfer channel with and without cross flow. Studied SJ had a deforming boundary that oscillated at 1000 Hz and was placed at a high orifice-to-plate distance ratio of 20. The flow field inside the device with a moving boundary was modeled in a coupled manner to the flow field outside of the device for 80 oscillation cycles. The coupled study of the flow fields inside and outside of the cavity revealed their interaction towards an unstable flow field. Moreover, comparison between SJ's and continuous jet's (CJ) cooling performance was performed with the same net mass flow rate and identical jet outlet temperatures. Without cross flow, CJ, and with cross flow, SJ outperformed in terms of heat removal. The remarkable difference in spatial evolution of CJ and SJ explains the better performance of SJ in cross flow regime. In the studied high orifice-to-plate distance, CJ stream was unable to penetrate effectively through the crossflow, while the vortical structures created by SJ were able to do so and impinge on the target surface with heat transfer augmentation at upstream. Furthermore, the SJ's cavity heating was found to be a limiting factor in its capability to achieve high heat transfer coefficients in confined channels, which needs to be addressed to maintain its reliable heat removal performance.

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