16.Ulusal SÄ±vÄ±hal FiziÄi Sempozyumu - Piri Reis Ãniversitesi

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Incompressible Smoothed Particle Hydrodynamics Modeling of Three Phase Flow Nima Tofighi, Mehmet Yıldız Sabancı University, Faculty of Engineering and Natural Sciences, Advanced Composites and Polymer Processing Laboratory, Turkey In this study, a two dimensional Incompressible Smoothed Particle Hydrodynamics (ISPH) method for modeling incompressible, immiscible three phase fluid flows has been developed. Surface tension coefficients are decomposed into phase specific coefficients and surface tension force is exerted by implementing continuum surface force (CSF) model. To complement this, a unique color function is associated with each phase and then smoothed out to improve the robustness of the method while a threshold has been implemented for choosing reliable normals to increase the accuracy of computed surface tension force. Furthermore, artificial particle displacement has been employed to ensure uniform spread of particles throughout the computational domain. Several test cases have been simulated to ensure the capability of the method in handling various three phase flow combinations. Having an analytical solution, the formation of a lens shape from a circular droplet under surface tension forces has been studied to facilitate testing the accuracy of the proposed method. Results show that this test case is highly sensitive to initial particle positioning, favoring an arrangement obtained from two phase diamond droplet relaxation over a droplet simply carved out of an equally spaced particle arrangement. Simulations have been carried out in three different resolutions, revealing that an abrupt cut at the tip of the lens is responsible for the inaccuracies incurred at low resolutions. The results obtained from high resolution simulations at different surface tension ratios using improved initial condition are found to be compatible with analytical solution of the equilibrium lens length. To further test the capabilities of the proposed method in handling dynamic problems, a droplet levitation test case has been simulated for different surface tension ratios. It is observed that, higher surface tension ratios result in faster break up from surface due to larger force exerted at triple junction. Furthermore, higher surface tension ratio resulted in larger maximum droplet velocity and higher stopping height. As the last test case, droplet spreading with a contact angle of 90◦ has been considered. With minor modifications, the method has been able to simulate contact line dynamics for a variety of Eotvos (Eo) numbers, demonstrating the flexibility of the method and its capability in handling density and viscosity differences between phases. Results obtained for Eo > 1 are compatible with analytical results available for these two extremes while a transition form spherical cap to puddle shape occurs for Eo values in between. The simulations conducted and the comparison of the results show that the proposed ISPH method is capable of handling different three phase flow problems common to many natural phenomena and engineering problems.
Mc30 Asfalten Süspansiyonlarında Dinamik Nükleer Polarizasyon Ahmet Peksöz, Aytaç Yalçıner Uludağ Üniversitesi, Fen-Edebiyat Fakültesi, Fizik Bölümü, Bursa %50 Ġran+%50Kazakistan kaynaklı MC30 sıvı asfaltından elde edilen MC30 asfalteninin toluene, 2-iodotoluene 2-bromotoluene, 2- chlorotoluene ve 2-fluorotoluene çözgen ortamlarında üç farklı konsantrasyonda (1.5, 3.0 ve 6.0 mg/cc) hazırlanan çözeltilerinde 1.44 mT’lık zayıf alan çift rezonans spektrometresinde dinamik nükleer polarizasyon deneyleri gerçekleĢtirildi. Doyma deneyleri 45 MHz’lik ESR frekansında yapıldı. Difüzyona uğrayan çözgen moleküllerindeki çekirdek spinleri ile asfalten misellerinde bulunan çiftlenmemiĢ elektron spinleri manyetik olarak etkileĢirler. Oda sıcaklığında yapılan deneyler, bu etkileĢmelerde MC30 asfalteninin tüm çözgen ortamlarında dipolar etkin bir davranıĢ sergilediğini gösterdi. Çekirdek-elektron çiftlenme parametresi ρ, toluene, 2-chlorotoluene, 2-fluorotoluene, 2- bromotoluene ve 2-iodotoluene ortamları için sırasıyla 0.063 * , 0.054, 0.050, 0.030 ve 0.015 olarak bulundu. Çekirdek sinyal büyümeleri daha fazla olan çözgenler asfalten moleküllerini daha iyi çözer. Toluen molekülünde meta pozisyonuna gelen atomlar Cl>F>Br>I sıralamasına göre NMR sinyal büyümelerini azaltmıĢtır yani çözgen ortamın asfalteni çözme yeteneğini bu sıralamaya göre azaltmıĢtır. MC30 asfaltenin moleküler yapısının tayinine yönelik IR spektroskopik incelemeleri, Thermo Nicolet FT-IR-6700 spekrometresi ile 400-4000 cm -1 aralığında ATR tekniği kullanılarak gerçekleĢtirildi. MC30 asfalteninin içerdiği fonksiyonel gruplar: 2954cm -1 ’de -CH 3 eğilme titreĢimleri, 2926 cm -1 ’de CH 2 gerilme titreĢimleri, 1600 cm -1 ’de C=C gerilme titreĢimleri, 1029 cm -1 ’de C 2 S=O, 721, 752 ve 802 cm -1 ’de aromatik düzlem dıĢı eğilmeler olarak belirlendi. * Toluene örneği için ρ değeri, M. Akif Çimenoğlu’nun çalıĢmasından alınmıĢtır. ( M.Akif Çimenoğlu, Fuel, 80 (2001) 2041-2047).
Page 2 and 3: SEMPOZYUM BĠLĠM KURULU Prof. Dr.
Page 4 and 5: 16. ULUSAL SIVIHAL FĠZĠĞĠ SEMPO
Page 6 and 7: 14:10-14:30 Kübik GaAs/AlAs Kuantu
Page 8 and 9: Nano-TiO 2 ve Nano-TiO 2 /Aktif Kar
Page 10 and 11: The effect of anions on the cloud p
Page 14 and 15: Calculation of Intermolecular Coulo
Page 16 and 17: AC Conduction Mechanism in Nafion E
Page 18 and 19: Amilorid Molekülünün Konformasyo
Page 20 and 21: Kübik GaAs/AlAs Kuantum Noktasın
Page 22 and 23: Structural Investigation of Biologi

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16.Ulusal SÄ±vÄ±hal FiziÄi Sempozyumu - Piri Reis Ãniversitesi