Mechanical Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/9145

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    ReviewPublicationOpen Access
    Critical review of the parameters affecting the effectiveness of moisture absorption treatments used for natural composites
    (MDPI AG,, 2019) Al-Maharma, Ahmad Yousef Mohammad; Al-Huniti, N.; Al-Maharma, Ahmad Yousef Mohammad
    Natural composites can be fabricated through reinforcing either synthetic or bio-based polymers with hydrophilic natural fibers. Ultimate moisture absorption resistance at the fiber–matrix interface can be achieved when hydrophilic natural fibers are used to reinforce biopolymers due to the high degree of compatibility between them. However, the cost of biopolymers is several times higher than that of their synthetic counterparts, which hinders their dissemination in various industries. In order to produce economically feasible natural composites, synthetic resins are frequently reinforced with hydrophilic fibers, which increases the incompatibility issues such as the creation of voids and delamination at fiber–matrix interfaces. Therefore, applying chemical and/or physical treatments to eliminate the aforementioned drawbacks is of primary importance. However, it is demonstrated through this review study that these treatments do not guarantee a sufficient improvement of the moisture absorption properties of natural composites, and the moisture treatments should be applied under the consideration of the following parameters: (i) type of hosting matrix; (ii) type of natural fiber; (iii) loading of natural fiber; (iv) the hybridization of natural fibers with mineral/synthetic counterparts; (v) implantation of nanofillers. Complete discussion about each of these parameters is developed through this study.
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    Conference paperPublicationOpen 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.
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    Conference paperPublicationOpen 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.