Akay, Hasan Umur

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Profile URL
https://hdl.handle.net/20.500.14411/6751
Name Variants
Akay, Hasan
Hasan, Akay
Akay,Hasan
Hasan Akay
A.,Hasan
H., Akay
A., Hasan
Akay,H.
Akay H.
H.,Akay
Akay, Hasan U.
Akay, H. U.
Akay, Hasan U. U.
Job Title
Profesör Doktor
Email Address
hasan.akay@atilim.edu.tr
Main Affiliation
Automotive Engineering
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Website
https://atilim.edu.tr/en/ae/page/2279/academic-staff
ORCID ID
0000-0003-2574-9942
Scopus Author ID
24532717000
Turkish CoHE Profile ID
Google Scholar ID
DLU2bk4AAAAJ
WoS Researcher ID
ABI-3992-2020

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11

SUSTAINABLE CITIES AND COMMUNITIES
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14

LIFE BELOW WATER
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5

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INDUSTRY, INNOVATION AND INFRASTRUCTURE
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16

PEACE, JUSTICE AND STRONG INSTITUTIONS
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PARTNERSHIPS FOR THE GOALS
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LIFE ON LAND
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REDUCED INEQUALITIES
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AFFORDABLE AND CLEAN ENERGY
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DECENT WORK AND ECONOMIC GROWTH
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Documents

131

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1286

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Scholarly Output

15

Articles

9

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Supervised PhD Theses

1

WoS Citation Count

85

Scopus Citation Count

109

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4

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WoS Citations per Publication

5.67

Scopus Citations per Publication

7.27

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3

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JournalCount
8th International Conference on Education and New Learning Technologies (EDULEARN) -- JUL 04-06, 2016 -- Barcelona, SPAIN2
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering2
International Journal of Computational Fluid Dynamics2
ARPN Journal of Engineering and Applied Sciences1
Computers & Fluids1
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Item Type: Scholarly Output

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Now showing 1 - 10 of 15
  • Thumbnail Image
    Article
    Citation - WoS: 7
    Citation - Scopus: 7
    A New Strategy for Solving Store Separation Problems Using Openfoam
    (Sage Publications Ltd, 2022) Abuhanieh, Saleh; Akay, Hasan U.; Bicer, Baris
    The ability of OpenFOAM to solve the problem of a store separating from an air vehicle (store separation problem) has been evaluated using a dynamic mesh (Overset/Chimera) technique for an industry-class (transonic and generic) benchmark test case. The major limitations of the standard libraries have been determined. To tackle these challenges, a new strategy has been proposed and implemented using only open-source libraries and tools. The strategy combines porting, modifying, and adapting an overset library from the OpenFOAM fork platform (foam-extend) to the standard OpenFOAM platform (ESI). Furthermore, in order to overcome the well-known weakness of the standard OpenFOAM compressible solvers, the newly adapted overset library was integrated with an open-source, density-based, and coupled solver (HiSA), which uses the OpenFOAM technology. Additionally, a force restrained model was developed to consider the externally applied forces on the store by the store ejectors. The accuracy of the developed strategy has been compared with wind tunnel tests and the solutions of two well-known commercial codes, showing good agreements with them. While the study has focused on simulations with inviscid Euler equations (typical of the test case considered here), the viscosity effect on the solution has also been studied with Navier-Stokes equations and compared with other results in the literature, showing minor differences. To the best of the authors' knowledge, this is the first work which studies and validates the store separation problem in transonic regime with OpenFOAM.
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    Article
    A Phenomenological Study of Instructors’ Experiences on an Open Source Learning Management System
    (Procedia - Social and Behavioral Sciences, 2011) Çiğdemoğlu, Ceyhan; Arslan, Harika Özge; Akay, Hasan
    This paper focuses on instructors’ experiences on usage of an open-source Learning Management System (LMS), Moodle in their courses. The study was conducted in a private university in Ankara, Turkey where the widespread use of the Moodle has only recently started. The phenomenological design has been utilized as qualitative research method for this paper. The Participants comprised in structures from different faculties who are new users of the Moodle. Open-ended interviews were carried out, and the data was transcribed into codes and themes. The research findings indicate that instructors have different impressions from the system in terms of their effort and expectation.
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    Article
    Citation - Scopus: 1
    Improved Parallel Preconditioners for Multidisciplinary Topology Optimisations
    (Taylor & Francis Ltd, 2016) Akay, H. U.; Oktay, E.; Manguoglu, M.; Sivas, A. A.
    Two commonly used preconditioners were evaluated for parallel solution of linear systems of equations with high condition numbers. The test cases were derived from topology optimisation applications in multiple disciplines, where the material distribution finite element methods were used. Because in this optimisation method, the equations rapidly become ill-conditioned due to disappearance of large number of elements from the design space as the optimisations progresses, it is shown that the choice for a suitable preconditioner becomes very crucial. In an earlier work the conjugate gradient (CG) method with a Block-Jacobi preconditioner was used, in which the number of CG iterations increased rapidly with the increasing number processors. Consequently, the parallel scalability of the method deteriorated fast due to the increasing loss of interprocessor information among the increased number of processors. By replacing the Block-Jacobi preconditioner with a sparse approximate inverse preconditioner, it is shown that the number of iterations to converge became independent of the number of processors. Therefore, the parallel scalability is improved.
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    Conference Object
    Effects of Chamber Pressure Variation on Pollutant Formation in Cryogenic Combustion
    (Ieee, 2021) Omair, Muhammad; Akay, Hasan U.
    Liquid rocket engines have played a major role in enabling the pursuit of space exploration. Cryogenic propellants have simplified the storage in liquid rocket engines with higher densities and lower pressures. One of the main driving forces in today's engine research is the reduction of pollutants while keeping the fuel consumption as low as possible. In this study cryogenic combustion has been simulated using the `Steady Laminar Flamelet' approach. Pollutant concentrations have been evaluated at different chamber pressures. It has been shown that combustion at higher chamber pressures results in less pollutant formation.
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    Article
    A Gradient Enhanced Efficient Global Optimization-Driven Aerodynamic Shape Optimization Framework
    (MDPI, 2025) Senol, Niyazi; Akay, Hasan U.; Yigit, Sahin
    The aerodynamic optimization of airfoil shapes remains a critical research area for enhancing aircraft performance under various flight conditions. In this study, the RAE 2822 airfoil was selected as a benchmark case to investigate and compare the effectiveness of surrogate-based methods under an Efficient Global Optimization (EGO) framework and an adjoint-based approach in both single-point and multi-point optimization settings. Prior to optimization, the computational fluid dynamics (CFD) model was validated against experimental data to ensure accuracy. For the surrogate-based methods, Kriging (KRG), Kriging with Partial Least Squares (KPLS), Gradient-Enhanced Kriging (GEK), and Gradient-Enhanced Kriging with Partial Least Squares (GEKPLS) were employed. In the single-point optimization, the GEK method achieved the highest drag reduction, outperforming other approaches, while in the multi-point case, GEKPLS provided the best overall improvement. Detailed comparisons were made against existing literature results, with the proposed methods showing competitive and superior performance, particularly in viscous, transonic conditions. The results underline the importance of incorporating gradient information into surrogate models for achieving high-fidelity aerodynamic optimizations. The study demonstrates that surrogate-based methods, especially those enriched with gradient information, can effectively match or exceed the performance of gradient-based adjoint methods within reasonable computational costs.
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    Article
    Citation - Scopus: 1
    Prediction of Ice Accretion Shapes on Aircraft Wings Using Open-Source Software
    (Asian Research Publishing Network, 2021) Edeeb,S.; Akay,H.U.; Ozgen,S.
    Ice accretion on aircraft components starts when an aircraft flies through atmospheric clouds containing supercooled liquid droplets, which have a temperature below freezing point but are still in a liquid state. Ice accretion occurs when water droplets impinge and freeze on the unprotected frontal regions of aircraft surfaces. The accumulated ice on aircraft components degrades the aircraft performance and causes serious flight problems. In this study, a computational fluid dynamics package is developed using open-source software. The created package is used to predict rime and glaze ice shapes on a wing airfoil for different icing condition cases. The results show a satisfactory agreement in ice shape prediction obtained using the OpenFOAM and Octave software with the corresponding data in the literature © 2006-2021 Asian Research Publishing Network (ARPN). All rights reserved.
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    Doctoral Thesis
    Mühimmat Ayrılması Problemlerinin Openfoam ile Çözümü
    (2022) Abuhanıeh, Saleh; Akay, Hasan; Biçer, Barış
    Bu tezde, OpenFOAM'un bir hava aracından ayrılan mühimmatı (mühimmat ayrılması problemi) dinamik bir çözüm ağı (Overset/Chimera) tekniği kullanarak çözme yeteneği endüstriyel (transonik/süpersonik ve jenerik) bir kıyaslama test durumu için ele alınmıştır. Standart kütüphanelerin temel kısıtları saptanmıştır. Bu zorlu problemin üstesinden gelebilmek için, yalnızca açık kaynaklı kütüphaneler ve araçlar kullanılarak yeni bir strateji önerilmiştir ve ygulanmıştır. Bu strateji overset kütüphanesinin OpenFOAM platformunun bir çatalından (foam-extend) standart OpenFOAM platformuna (ESI) taşınması, değiştirilmesi ve uyarlanmasının birleşiminden oluşmaktadır. Bunun yansıra, standart OpenFOAM sıkıştırılabilir çözücülerinin iyi bilinen zayıflıklarının üstesinden gelebilmek için, yeni uyarlanmış overset kütüphanesi, OpenFOAM teknolojisini kullanan bir açık kaynaklı basınç tabanlı ve bağlaşık çözücü olan HiSA ile entegre edilmiştir. Gerekli doğrulama ve sağlama süreçlerinin ardından, durağan ve zamana bağlı simülasyonlar için HiSA çözücüsü kullanılmıştır. Doğrulama çalışmalarının bir kısmı bu tezde sunulmuştur. Ek olarak, mühimmat ejektörleri tarafından mühimmata dışarıdan uygulanan kuvvetleri dikkate almak için kuvvet kısıtlamalı bir model geliştirilmiştir. Geliştirilen bu stratejinin doğruluğu, rüzgâr tüneli testleri ve iyi bilinen iki ticari hesaplamalı akışkanlar dinamiği (HAD) kodunun çözümleri ile karşılaştırılmıştır ve bu sonuçlarla oldukça uyumlu olduğu gösterilmiştir. Bu çalışma viskoz olmayan Euler denklemi ile yapılan simülasyonlara odaklanırken (burada ele alınan test durumunun karakterıstiği), çözüm üzerindeki viskozite etkisi de ayrıca Navier-Stokes denklemi ile incelenmiş ve literatürdeki diğer sonuçlar ile karşılaştırılmıştır ve kayda değer bir farklılık gözlemlenmemiştir. Ek olarak, aynı test durumu için zamansal ve uzaysal bağımsızlık çalışması yapılmıştır. Bilindiği kadarıyla bu çalışma transonik ve süpersonik rejimlerde mühimmat ayrılması problemini OpenFOAM ile inceleyen ve doğrulayan ilk çalışmadır.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Numerical Investigation of Store Separation From Cavity Problems at High Speeds
    (Sage Publications Ltd, 2023) Abuhanieh, Saleh; Akay, Hasan U.
    In this work, the ability of open-source CFD tools to conduct store separation simulations from cavities is evaluated and validated using a generic test case from the literature. Firstly, the ability and accuracy of these tools for solving cavity flows at high speeds are evaluated. Secondly, their competence in predicting the trajectory of a generic store from a generic deep cavity is checked. Finally, and in order to reduce the associated computational costs, a release-time dependability factor from the recent literature is studied and evaluated. The obtained results using the selected open-source CFD tools matched quite well with the wind tunnel results. Furthermore, the results show that predicting the release-time dependability using a quantified index/factor can be a potential remedy for reducing the computational cost for this type of CFD simulations.
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    Article
    Improved Simulation of Cryogenic Fluid Mixing at Supercritical Pressures
    (Public Library Science, 2023) Omair, Muhammad; Akay, Hasan U. U.
    The combustion chamber pressure of rockets, gas turbines and diesel engines is known to be above the critical pressure of fuel and oxidizers. In the case of rocket engines the fuel and/or oxidizer is often injected at cryogenic temperatures. This elevated combustion chamber pressure and low temperature demands special treatment for numerical analysis of mixing. Thus a novel implementation of an improved equation of state has been proposed which provides better estimation of densities. Experimental and numerical data from literature has been used for validation of the analysis methodology.
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    Article
    Citation - WoS: 6
    Flows Around Moving Bodies Using a Dynamic Unstructured Overset-Grid Method
    (Taylor & Francis Ltd, 2010) Liu, Jingxin; Akay, Hasan U.; Ecer, Akin; Payli, Resat U.
    In this article, a computational fluid dynamics algorithm is presented for simulations of complex unsteady flows around rigid moving bodies using an unstructured overset-grid method. For this purpose, a highly automated, three-dimensional, tetrahedral, unstructured overset-grid method is developed with one-cell-width overlapping zone in order to model the arbitrary geometries for steady and unsteady flow simulations. A method has been described to obtain the inter-grid boundaries of the one-cell-wide overlapping zone shared by a background grid and a minor grid. In the overset-grid methodology, vector intersection algorithm and bounding box techniques have been utilised. The mesh refinement and overset-scheme conservation studies proved the accuracy and efficiency of the method developed here. The applications of the developed algorithms were also performed through simulations that included complex internal flows around a flow-control butterfly valve as well as flows in an internal combustion engine with a moving piston. Lastly, validations with experimental data were conducted for both steady and unsteady flows around rigid bodies with relative motions.