Akşit, Serhat
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Aksit, Serhat
Aksıt, Serhat
Akşit, S.
Aksıt, Serhat
Akşit, S.
Job Title
Arş. Gör.
Email Address
serhat.aksit@agu.edu.tr
Main Affiliation
02.03. İnşaat Mühendisliği
Status
Current Staff
Website
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Sustainable Development Goals
SDG data is not available
Documents
3
Citations
13
h-index
2
Documents
3
Citations
11
Scholarly Output
4
Articles
4
Views / Downloads
16/3
Supervised MSc Theses
0
Supervised PhD Theses
0
WoS Citation Count
11
Scopus Citation Count
13
WoS h-index
2
Scopus h-index
2
Patents
0
Projects
0
WoS Citations per Publication
2.75
Scopus Citations per Publication
3.25
Open Access Source
1
Supervised Theses
0
| Journal | Count |
|---|---|
| Ocean Engineering | 2 |
| Modeling Earth Systems and Environment | 1 |
| Niğde Ömer Halisdemir Üniversitesi Mühendislik Bilimleri Dergisi | 1 |
Current Page: 1 / 1
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4 results
Scholarly Output Search Results
Now showing 1 - 4 of 4
Article Effect of Different Pitch Ratios on the Flow Around Tandem Circular Cylinders with Spoilers(Elsevier Ltd, 2025) İlkentapar, M.; Akşit, S.; Öner, A.A.; Genç, M.S.This study experimentally investigates the unsteady aerodynamic characteristics of two tandem circular cylinders subjected to various pitch ratios and spoiler configurations in a controlled wind tunnel environment. The primary objective is to understand how the placement and presence of spoiler's influence flow separation, wake interference, surface pressure distributions, and overall aerodynamic performance. The experiments were conducted for three pitch ratios (2D, 4D, and 7D) and four spoiler configurations: NN (no spoilers on either cylinder), NS (spoiler on the downstream cylinder only), SN (spoiler on the upstream cylinder only), and SS (spoilers on both cylinders). Measurements included surface pressure, velocity distribution via hot-wire anemometry, and aerodynamic forces, while qualitative flow patterns were assessed using smoke-wire visualization. The results indicate that the usage of spoilers substantially alters the wake structure and pressure profiles, especially in closely spaced configurations. In the NN configuration, increasing the pitch ratio led to a progressive decoupling of the flow between the cylinders, transitioning from a merged wake to more isolated vortex shedding. In the SN and NS configurations, the asymmetrical placement of spoilers induced unsteady wake interactions and altered reattachment dynamics on the downstream body. The SS configuration exhibited the most disturbed flow regime at low pitch ratios, which gradually stabilized as the spacing increased. Violin plots derived from velocity measurements provided statistical insight into flow symmetry and turbulence intensity, while smoke visualizations captured coherent structures and transition zones across the configurations. The combined analysis demonstrates that both pitch ratio and spoiler configuration are critical parameters in controlling aerodynamic interference and unsteady wake behavior in tandem arrangements. These findings offer valuable implications for flow management and control strategies in offshore structures, cylindrical risers, and heat exchanger tube banks, where vortex-induced vibrations and flow separation play crucial roles. © 2025 Elsevier B.V., All rights reserved.Article Citation - WoS: 7Citation - Scopus: 9The Effect of Spoilers on Flow Around Tandem Circular Cylinders(Pergamon-Elsevier Science Ltd, 2023) Ilkentapar, Mucella; Aksit, Serhat; Acikel, Halil Hakan; Oner, Ahmet AlperExamining the flow characteristics around the cylindrical elements, such as offshore (submarine) pipelines which can be used in single or multiple arrangements, has a prominent place in fluid mechanics. The use of spoilers for self-embedding of these structures has been a subject that researchers have studied for many years. In this study, (a) the flow around a cylinder without and with a spoiler and (b) the effect of adding spoiler(s) to the tandem cylinders on the flow was experimentally investigated. In these experiments, where the ratio of the distance between the cylinders to the cylinder diameter is 2, the Reynolds number is 14000, which remains in the subcritical region. Four experiments were performed: the smoke-wire method was used for flow visualization, aerodynamic force measurement, velocity measurement by hot-wire anemometer, and pressure measurement to determine the pressure distribution on the cylinders. Pressure, velocity, and force results were recorded with the time histories in this study for the first time. Experimental studies show that when a spoiler is added to a single cylinder, an opposing lift force acts on that and the drag force increases due to the enlargement of the lowpressure region at the wake of the cylinder. In a tandem situation, when the upstream cylinder has a spoiler, no drag force acts on the downstream cylinder. The forces exerted on the upstream cylinder are not affected by whether the downstream cylinder has a spoiler. In the case of the downstream cylinder with the spoiler, the fluctuations in the aerodynamic forces of the upstream cylinder decrease owing to the downstream cylinder with the spoiler. The force fluctuations are more in the downstream cylinder, and unlike other tandem and singlecylinder cases, the vortex shedding becomes complex.Article Citation - WoS: 4Citation - Scopus: 4Advanced Hybrid Machine Learning Methods for Predicting Rainfall Time Series: The Situation at the Kütahya Station in Türkiye(Springer Heidelberg, 2025) Ilkentapar, Mucella; Citakoglu, Hatice; Talebi, Hamed; Akturk, Gaye; Spor, Pinar; Caglar, Yasin; Aksit, SerhatLong-term variations in rainfall patterns, known as rainfall variability, have increasingly impacted ecological and socioeconomic systems, particularly in regions with high sensitivity. Consequently, accurate forecasting of rainfall at both short- and long-term time scales is essential, necessitating a comprehensive analysis of historical rainfall time series data collected from meteorological stations. In this study, K & uuml;tahya Province was selected as the study area, utilizing monthly rainfall data from its sole meteorological station spanning the period from 1960 to 2023. The dataset was partitioned into a training set (January 1960-March 2008) and a test set (April 2008-December 2023). Lagged rainfall values at t-1, t-2, and t-3 were used as input variables to predict rainfall at time t. The primary objective of this research is to assess the effectiveness of various preprocessing techniques in developing hybrid machine learning models for rainfall prediction. Gaussian Process Regression (GPR), Support Vector Machines, and Adaptive Neuro-Fuzzy Inference System were employed as machine learning methods. Furthermore, multiple signal decomposition techniques, including Complete Ensemble Empirical Mode Decomposition (CEEMD), Tunable Q-Factor Wavelet Transform, Empirical Mode Decomposition, Robust Empirical Mode Decomposition, Variational Mode Decomposition, Empirical Wavelet Transform, and Ensemble Empirical Mode Decomposition (EEMD), were utilized as preprocessing steps to enhance model performance. The predictive performance of the developed hybrid models was evaluated using various statistical measures. Among the evaluated models, the CEEMD-GPR hybrid model exhibited the best prediction performance with Coefficient of Determination (R2 = 0.998) and Nash-Sutcliffe Efficiency (NSE = 0.998) values close to 1, Mean Absolute Error (MAE = 1.42) and Mean Squared Error (RMSE = 1.79) values close to zero. These findings indicate that CEEMD demonstrated superior decomposition efficiency compared to the other six decomposition techniques. Additionally, the Kruskal-Wallis test conducted during the analysis phase yielded a statistical significance level of p > 0.05, confirming that the observed and predicted rainfall data originated from the same distribution. Consequently, the effectiveness and reliability of the proposed hybrid models for rainfall prediction were validated.Article Computational and Experimental Investigation of Water Surface Around Bridge Piers(2025) Çelik, Ahmet Mesut; İlkentapar, Mücella; Aksıt, Serhat; Öner, Ahmet AlperKöprü ayakları etrafındaki serbest yüzeyli akım, açık kanal hidroliğinin en önemli problemlerinden biridir. Köprünün yapısal tasarımı, köprü ayakları etrafında oluşacak oyulma ve köprü ayakları etrafındaki su hareketini simüle eden hidrolik tasarım ile birlikte doğru bir şekilde yapılmalıdır. Köprü ayaklarının hidrolik tasarımı yeterince iyi değilse, sel ve taşkın gibi durumlarda çok ciddi hasarlara neden olabilir. Bu çalışmanın amacı köprü ayaklarının su yüzeyine etkisini deneysel ve sayısal olarak analiz etmektir. Sayısal analiz için hesaplamalı akışkanlar dinamiği ile 3 boyutlu çözüm yapan FLOW-3D paket programı ile HEC-RAS paket programı kullanılmış ve sonuçlar karşılaştırılmıştır. Çalışmada farklı köprü açıklık sayıları için aynı hızda akışlar incelenmiş ve deneysel sonuçlarla karşılaştırılmıştır. Ayrıca sonlu hacimler yöntemi ile çözüm yapan FLOW 3D paket programında farklı mesh boyutları ile çözüm yapılarak deneysel sonuçlar ile karşılaştırılmıştır. Sonuç olarak FLOW-3D paket programı ile gerçekleştirilen çözümlerin deneysel veriler ile oldukça yakın sonuçlar gösterdiği gözlemlenmiştir.
