Papers by Levent A Kavurmacioglu
Journal of Fluids Engineering-transactions of The Asme, Jun 29, 2018
The aim of the current study is to investigate the effect of inlet blade angles on cavitation per... more The aim of the current study is to investigate the effect of inlet blade angles on cavitation performance in a centrifugal pump. In order to reveal this relationship, both hub and shroud blade angles are considered and a two-phase three-dimensional computational fluid dynamics (CFD) study is carried out. Shear stress transport (SST) turbulence and Rayleigh–Plesset cavitation models are used in simulations. Inlet blade angles for both hub and shroud are changed and pump performance (head-discharge) and cavitation (head-inlet pressure) graphs are obtained for eight different designs. Afterward, numerical cavitation tests are conducted, required net positive suction head values of the each design are calculated, and variations are demonstrated. Results show that hub and shroud blade angle variations have no significant effect on the pump characteristic curves excluding for shroud blade angle at high discharge values. However, cavitation performance of the pump is excessively affected for both hub and shroud blade angle alterations. Increasing hub blade angle has slightly negative effect on cavitation performance of the pump. On the other hand, while increasing shroud blade angle from 20 deg to 30 deg have positive effect on cavitation performance, it is negatively affected from 30 deg to 50 deg.
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Journal of Craniofacial Surgery, Nov 1, 2009
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The two-dimensional incompressible non-isothermal confined twin-jet flow has been numerically stu... more The two-dimensional incompressible non-isothermal confined twin-jet flow has been numerically studied in the transitional flow regime by a finite volume technique. Results have been obtained for the velocity and temperature distributions close to the onset of temporal oscillations. Next, the proper orthogonal decomposition (POD) is applied to the instantaneous flow and temperature data to obtain POD-based basis functions for both velocity and temperature fields. These basis functions are capable to identify the coherent structures in the velocity and temperature fields. The low-dimensional Galerkin models of the full Navier-Stokes and energy equations are constructed by the Galerkin projection onto basis functions. Since the low-dimensional Galerkin models are much easier to analyze than the full governing equations, basic insights into important mechanisms of dynamically complex flow and heat transfer (e.g. flow instabilities) can be easily studied by these models. The numerical implications, the validity of the models and their performance characteristics are discussed.
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Gazi Üniversitesi Mühendislik Mimarlık Fakültesi Dergisi
Eksenel türbinlerin kanat kökü ve kanat uç bölgelerinde oluşan karmaşık üç boyutlu ikincil akış y... more Eksenel türbinlerin kanat kökü ve kanat uç bölgelerinde oluşan karmaşık üç boyutlu ikincil akış yapılarının ana akış ile etkileşimi sonucunda yüksek oranda aerodinamik kayıplar oluşmaktadır. Bu çalışmada gaz türbini kanatları arasındaki akışta oluşan ikincil akış kaynaklı aerodinamik kayıpların azaltılmasına yönelik olarak literatürde bağımsız olarak kullanılan iki yöntem birleştirilerek incelenmiştir. Bu yöntemler kanatlar arası bölgeye bariyer ilave edilmesi ve literatürde kompresör kanatları için uygulanan kasa geometrisinin yivlenmesi yöntemleridir. Bu doğrultuda öncelikle bariyer ve yiv uygulanmamış rotor hali incelenmiş, ardından beş farklı geometride bariyer uygulanmış durum ve son olarak her bir bariyerle birlikte olmak üzere iki farklı yiv geometrisi birleştirilerek oluşan geometriler için akış alanları ve kayıplar incelenmiştir. Kayıpların değerlendirilmesinde kanatlar arası bölge giriş ve çıkış toplam basınçlarında görülen farklar ve bu farkların kütle ortalamalı toplam b...
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Conference proceedings, 2017
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Journal of marine science and technology, Jul 11, 2022
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International Journal of Aerospace Engineering, May 2, 2018
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Progress in Computational Fluid Dynamics, 2007
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International Journal of Heat and Mass Transfer, Nov 1, 2019
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International Journal of Heat and Mass Transfer, May 1, 2018
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Aerospace Science and Technology, May 1, 2018
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HAL (Le Centre pour la Communication Scientifique Directe), Apr 10, 2016
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Social Science Research Network, 2022
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Politeknik dergisi, Dec 1, 2021
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A parametric computational study has been conducted in order to investigate the effect of a squea... more A parametric computational study has been conducted in order to investigate the effect of a squealer geometry in axial flow gas turbines. Although the present investigation deals with the conventional squealer tip design, the main goal of the parametric approach is to obtain significant time savings in the computational analysis of future tip mitigation schemes. At this preliminary stage, both width and height of the conventional squealer tip have been introduced as design parameters. Computational Fluid Dynamics (CFD) analysis has been conducted for a linear turbine cascade arrangement. Computations have been performed for a single blade passage considering periodicity in the tangential direction with no relative motion between blade and the casing. In order to generate the mesh, an effective parametric grid generation has been performed using a multizone structured mesh. Numerical solutions have been obtained by solving the 3D, incompressible, steady and turbulent form of the Reynolds-Averaged Navier-Stokes (RANS) equations using the general purpose solver ANSYS CFX. Two equation turbulence model, Shear Stress Transport (SST) has been used. Sixteen different squealer tip geometries were modeled parametrically and their performance has been compared in terms of both aerodynamic loss and heat transfer to blade tip. In addition to significant time savings for the squealer tip modeling and gridding, the specific parametric approach paves the way for aerothermal optimization of advanced squealer geometries such as optimized tip carving based geometries. Results obtained in this study are going to be used for the aerothermal optimization of the squealer blade tip geometry.
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European Journal of Mechanics B-fluids, Mar 1, 2022
This study presents the hydrodynamic characteristics around a torpedo-like geometry under the fre... more This study presents the hydrodynamic characteristics around a torpedo-like geometry under the freesurface effect at different angles of attack using preliminary dye visualization and Particle Image Velocimetry (PIV). The optimized torpedo-like geometry is placed at submersion ratios between 0.5≤h/D≤3.50 where h is the distance to the free-surface from its centerline and D is the diameter. Throughout the experiments, angles of attack were taken as 0 • ≤ α ≤12 • for two Reynolds numbers, Re = 2.0 × 10 4 and 4.0 × 10 4. The PIV method provided instantaneous vorticity and time-averaged velocity components, vorticity, streamline topology, fluctuating velocity components, Reynolds stress correlation, and the turbulent kinetic energy. This study focused on the stern section and the wake structures at h/D = 1.0. It is demonstrated that a jet-like flow region occurred between the model and the free-surface for all angles of attack at small submersion ratios of 0.5≤h/D≤1.0 while it is observed at h/D = 1.5 for α = 8 • , a jet-like flow region occurred between the model and the free-surface. The impact of the jet-like flow was more noticeable for α = 4 • and 8 • with velocity fluctuations in lower magnitudes. The nose section partially pierced the free-surface for h/D = 0.5, 0.75, and 1.0 in the range of 4 • ≤ α ≤12 • and it prevented the wake region from connecting with the free-surface by directing the separated flow region toward the stern section. Pointwise variations of the turbulence data extracted from vertical lines within the wake region for all cases revealed that the effect of the free-surface on the turbulence statistics was negligible beyond h/D=2.0.
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International Journal of Thermal Sciences, 2016
Abstract While studies concerning heat transfer due to oscillating air (and few other gases) flow... more Abstract While studies concerning heat transfer due to oscillating air (and few other gases) flow in metal foam are available, heat transfer due to oscillating water flow in metal foam has not been offered in the literature. This paper presents characteristics of heat transfer of oscillating water flow in commercial open-cell metal-foam pipe that were obtained experimentally, most likely for the first time. One main difference between gas and liquid flows in porous media is that dispersion is far more significant in the latter. Another difference is the length of the entrance region, which depends strongly on the Prandtl number. The trends in the cycle-averaged wall temperature, length-averaged wall temperature and cycle-averaged Nusselt number were similar to those for oscillating water flow in packed spheres and for oscillating air flow in aluminum, copper and graphite foams in a rectangular channel. For the higher flow frequency of the current study, the cycle-averaged Nusselt number was higher for higher flow displacement amplitude.
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Journal of Thermal Engineering, 2016
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Papers by Levent A Kavurmacioglu