Gökhan Kirkil

Kirkil, Gökhan

Name Variants

K.,Gokhan
G. Kirkil
Kirkil,Gokhan
Kirkil,G.
GÖKHAN KIRKIL
Kirkil, Gokhan
K., Gokhan
Kirkil, G.
Gökhan KIRKIL
Kirkil G.
Gökhan Kirkil
Gokhan, Kirkil
KIRKIL, Gökhan
K., Gökhan
KIRKIL, GÖKHAN
Kirkil, GÖKHAN
Kirkil, Gökhan
Kirkil, Gökhan
Kirkil, Gökhan

Job Title

Doç. Dr.

Email Address

gokhan.kirkil@khas.edu.tr

ORCID ID

0000-0001-9213-007X

Scopus Author ID

12039334900

Full item page

Scholarly Output

32

Articles

13

Citation Count

358

Supervised Theses

8 Scholarly Output Search Results

Now showing 1 - 10 of 31

Development of a Parallel 3d Navier–stokes Solver for Sediment Transport Calculations in Channels
(MDPI AG, 2020) Kirkil, Gökhan; Kirkil, Gökhan
We propose a method to parallelize a 3D incompressible Navier–Stokes solver that uses a fully implicit fractional-step method to simulate sediment transport in prismatic channels. The governing equations are transformed into generalized curvilinear coordinates on a non-staggered grid. To develop a parallel version of the code that can run on various platforms, in particular on PC clusters, it was decided to parallelize the code using Message Passing Interface (MPI) which is one of the most flexible parallel programming libraries. Code parallelization is accomplished by “message passing” whereby the computer explicitly uses library calls to accomplish communication between the individual processors of the machine (e.g., PC cluster). As a part of the parallelization effort, besides the Navier–Stokes solver, the deformable bed module used in simulations with loose beds are also parallelized. The flow, sediment transport, and bathymetry at equilibrium conditions were computed with the parallel and serial versions of the code for the case of a 140-degree curved channel bend of rectangular section. The parallel simulation conducted on eight processors gives exactly the same results as the serial solver. The parallel version of the solver showed good scalability.
Turkish Public Preferences for Energy
(Elsevier Science, 2018) Ediger, Volkan S.; Kirkil, Gökhan; Kirkil, Gökhan; Ediger, Şevket Volkan; Çelebi, Emre; Ucal, Meltem; Ucal, Meltem Şengün; Kentmen-Cin, Çiğdem
Public concern over energy supplies prices sustainability and efficiency has emerged as a major issue around the world. Yet most of what we know regarding public opinion on energy comes from North America and Europe. This paper presents the results from the 2016 Turkish Public Preferences for Energy Survey which included 1204 respondents and examined Turkish residents' household energy consumption energy policy preferences and environmental concerns. The main findings were that Turkish citizens consider natural gas and electricity highly expensive view dependence on imported energy as Turkey's most pressing energy challenge and recognize the problem of climate change. This lends public support for wind and solar power but at the same time energy issues and the environment policies of political parties do not affect voting choices and political preferences.
Potential and Status of Renewable Energy Development in Energy Import-Dependent Countries Turkey and Pakistan
(Kadir Has Üniversitesi, 2021) Majeed, Mohsina; Kirkil, Gökhan; Ediger, Şevket Volkan; Kirkil, Gökhan
Human life cannot be imagined without the use of energy. Demand for energy, meanwhile, is increasing daily across the globe, while the uses and sources of energy have changed over time. Fossil fuels have dominated other energy sources since the 19th century but began causing problems such as climate change. In order to address these problems, renewable energy sources (RES) were accepted as an alternative energy sources in recent years and technical and economic developments make possible the energy transition from fossil fuels to renewables at an accelerated rate. Turkey and Pakistan are both developing countries with large populations and high levels of energy-import dependency, 77% and 80%, respectively. At the same time, Turkey and Pakistan both have enormous potential for RE such as solar, wind, hydro, biomass and geothermal, according to the validated RE-potential maps of these countries. Turkey and Pakistan are realizing renewable energy transition and seeking to shape their current energy structure in the favor of RES. The factors affecting RED in Turkey and Pakistan are enormous RE potential, supportive RE policies by government and energy security issues. There are some political, economic, technical and social problems for RED in Turkey and Pakistan that include lack of proper RE policies, extended and time-consuming governmental procedures, the lack of domestic production of goods, and other financing problems for RE projects. If proper policy support and efficient investment become available, RES can provide enough power to fulfill the country's energy demand and bring prosperity and sustainability to both countries. Current RED in these countries is not sufficient for complete energy transition from fossil fuels to renewables. However, RE potential in these countries is enough for complete energy transition. According to SWOT analysis Pakistan's RE sector has various investment opportunities for Turkish investors. It has a validated RE source mapping system and untapped highly potential solar and windy areas. Mini-hydro plants is also a successful RE business model in Pakistan. The government of Pakistan is also offering various incentives for RE investors. Keywords: Renewable energy transition, sustainability, solar, wind, fossil fuel
Flow Structure in a Mixing Layer Developing Over Flat Bed at High Reynolds Numbers
(Iahr-int Assoc Hydro-environment Engineering Research, 2015) Kirkil, Gokhan; Kirkil, Gökhan
Results of a high resolution Detached Eddy Simulation (DES) are used to characterize the evolution of a shallow mixing layer developing between two parallel streams in a long open channel with a flat bed at a high Reynolds number (ReD= 160,000). The influence of Reynolds number on the development of the mixing layer as well as the vertical nonuniformity in the mixing layer structure is discussed. The numerical results show that as Reynolds number increases, the mixing layer development ceases earlier. Mixing layer growth rate and its change in the vertical direction at ReD= 160,000 are compared with experiments and a simulation at ReD= 16,000. Passive scalar is introduced at the tip of the splitter plate close to the free surface to estimate the size of the mixing structures based on mass transport. The effect of the Reynolds number on the shift of the centerline of the mixing layer is quantified.
Genesys-Mod Turkey: Quantitative Scenarios for Low Carbon Futures of the Turkish Energy System
(IEEE Computer Society, 2022) Hasturk, I.S.; Kirkil, Gökhan; Celebi, E.; Yucekaya, A.D.; Kirkil, G.
This paper examines the quantitative scenarios for low-carbon futures of the Turkish energy system at aggregated (country level) and regionally disaggregated (NUTS-1 level) levels. We have employed four different storylines for the future European energy system. They are quantified and implemented for the European energy system (30 regions, mostly single countries, including Turkey) using the open-source global energy system model, GENeSYS-MOD v3.0. We have compared the results of all scenarios at aggregated and disaggregated levels and found that there are significant differences among them. Specifically, the hydrogen production (and its use) has increased considerably in the disaggregated model when compared to the aggregated level results. The major reason for these differences is found to be the better estimation of regional renewable capacity factors (wind and solar) in the disaggregated level compared to aggregated level. © 2022 IEEE.
A Numerical Study of Shallow Mixing Development Over Flat Surface and Dunes
(TSINGHUA UNIV, 2013) Kirkil, Gökhan; Kirkil, Gökhan; Constantinescu, George
Results of a high resolution Detached Eddy Simulation (DES) are used to characterize the evolution of a shallow mixing layer developing between two parallel streams in a long open channel with a smooth flat bed and dunes. The study discusses the vertical non-uniformity in the mixing layer structure and provides a quantitative characterization of the growth of the large-scale quasi two-dimensional (2D) coherent structures with the distance from the splitter plate. Results show that in streamwise sections situated between 75D (D is the channel depth) and 150D from the splitter plate the width of the mixing layer close to the free surface is 20-30% more than the width in the near-bed region in the case in which the channel bed is flat. This is mostly because of the tilting of the mixing layer interface on the low-speed side toward the low speed stream as the free surface is approached. Power spectra of the horizontal velocity components show the presence of a -3 subrange at streamwise locations situated more than 10D from the splitter plate consistent with the presence of large-scale quasi 2D horizontal eddies and the transfer of energy (inverse energy cascade) from the smaller scales toward these eddies. Consistent with visualizations of the mass transport of a passive scalar within the mixing layer close to the free surface the estimated streamwise length of the quasi 2D mixing layer eddies is about 2.5 to 3.0 times larger than the local width of the mixing layer. The presence of large-scale roughness elements in the form of an array of two-dimensional dunes with a maximum height of 0.25D (D is the channel depth) induces a much more rapid and larger shift of the centerline of the mixing layer due to the increased influence of the bottom roughness.
Resolved Turbulence Characteristics in Large-Eddy Simulations Nested Within Mesoscale Simulations Using the Weather Research and Forecasting Model
(2014) Mirocha, Jeff; Kirkil, Gökhan; Kosovic, Branko; Kirkil, Gökhan
One-way concurrent nesting within the Weather Research and Forecasting Model (WRF) is examined for conducting large-eddy simulations (LES) nested within mesoscale simulations. Wind speed spectra and resolved turbulent stresses and turbulence kinetic energy from the nested LES are compared with data from nonnested simulations using periodic lateral boundary conditions. Six different subfilter-scale (SFS) stress models are evaluated using two different nesting strategies under geostrophically forced flow over both flat and hilly terrain. Neutral and weakly convective conditions are examined. For neutral flow over flat terrain turbulence appears on the nested LES domains only when using the two dynamic SFS stress models. The addition of small hills and valleys (wavelengths of 2.4 km and maximum slopes of ±10°) yields small improvements with all six models producing some turbulence on nested domains. Weak convection (surface heat fluxes of 10 Wm-2) further accelerates the development of turbulence on all nested domains. However considerable differences in key parameters are observed between the nested LES domains and their nonnested counterparts. Nesting of a finer LES within a coarser LES provides superior results to using only one nested LES domain. Adding temperature and velocity perturbations near the inlet planes of nested domains shows promise as an easy-to-implement method to accelerate turbulence generation and improve its accuracy on nested domains. © 2014 American Meteorological Society.
Flow Structure in a Shallow Mixing Layer Developing Over 2-D Dunes
(E D P Sciences, 2018) Kirkil, Gökhan; Kirkil, Gökhan
A high resolution Detached Eddy Simulation (DES) are used to characterize the evolution of a shallow mixing layer developing between two parallel streams in a long open channel over two-dimensional (2D) dunes. The study discusses the vertical non-uniformity in the mixing layer and provides a quantitative characterization of the growth of the large-scale quasi 2D coherent structures with the distance from the splitter plate. The presence of large-scale roughness elements in the form of an array of two-dimensional dunes with a maximum height of 0.25D (D is the channel depth) induces a very rapid and larger shift of the centerline of the mixing layer due to the increased influence of the bottom roughness. Results show that in streamwise sections situated after 100D (D is the channel depth) from the splitter plate, the width of the mixing layer close to the free surface stays constant. The tilting of the mixing layer interface toward the low speed stream is observed as the free surface is approached in all vertical sections.
Exploring Non-Linear Relationships Between Perceived Interactivity or Interface Design and Acceptance of Collaborative Web-Based Learning
(Springer, 2023) AL-Sayid, Fareed; Kirkil, Gökhan; Kirkil, Gokhan
The novelty of this study is in developing a conceptual model for predicting the non-linear relationships between human-computer interaction factors and ease of use and usefulness of collaborative web-based learning or e-learning. Ten models (logarithmic, inverse, quadratic, cubic, compound, power, s-curve, growth, exponential, and logistic) were examined as functions of effects compared to linear relationships to see which was the most appropriate, based on R-2, adjusted R-2 and SEE values. To answer the addressed questions, the researcher surveyed 103 students from Kadir Has University about the perceived interface and interactivity of e-learning. The results show that most of the hypotheses formulated for this purpose have been proven. Our analysis shows that cubic models (the relationship between ease of use and usefulness, visual design, course environment, learner-interface interactivity, and course evaluation system and ease of use), quadratic models (the relationship between visual design, and system quality and usefulness, course structure and content, course environment, and system quality and ease of use), logarithmic model (the relationship between course evaluation system and usefulness), and s-curve models (learner-interface interactivity, navigation, and course structure and content and usefulness) performed better in the description for the correlations.
Flow Structure in a Mixing Layer Developing Over Flat Bed at High Reynolds Numbers
(CRC Press/Balkema, 2016) Kirkil, G.; Kirkil, Gökhan
Results of a high resolution Detached Eddy Simulation (DES) are used to characterize the evolution of a shallow mixing layer developing between two parallel streams in a long open channel with a flat bed at a high Reynolds number (ReD = 160,000). The influence of Reynolds number on the development of the mixing layer as well as the vertical non-uniformity in the mixing layer structure is discussed. The numerical results show that as Reynolds number increases, the mixing layer grows rapidly but also stabilizes more quickly. The shift of the centerline of the mixing layer is toward the low-speed side is less for high Reynolds number simulation than low Reynolds number simulation. Mixing layer growth rate and its change in the vertical direction are compared with experiments and a simulation at ReD = 16,000. Passive scalar is introduced at the tip of the splitter plate close to the free surface to estimate the size of the mixing structures based on mass transport. © 2016 Taylor & Francis Group, London.