Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Refinement of field-measured velocity profiles via CFD comparison: A case study on single-phase flow in aeration tanks
Yilmaz Çelik, Damla; Vaheddoost, Babak; Aras, Egemen; Şibil, Rahim
The accuracy of field measurements obtained from aeration tanks is of critically important for the validation of Computational Fluid Dynamics (CFD) models. In many cases, the employed validation metrics serve as a fundamental keystone for evaluating both the credibility of experimental data and the accuracy of numerical simulations. In this study, a novel data refinement approach is developed to assess the physical plausibility of velocity measurements collected from a full-scale aeration tank. Unlike conventional validation approaches, the CFD model is utilized as a reference framework within a reverse-approach perspective to evaluate the reliability of field data. Measurement points affected by acoustic noise, surface sludge interference, and turbulence near static structures were identified and excluded through curve-fitting and statistical filtering techniques. Velocity data obtained with the help of an Acoustic Doppler Current Profiler (ADCP) across six lateral and 53 vertical layers were evaluated using the Coefficient of Determination (R2), Relative Error (RE), and Performance Index (PI) metrics. The maximum-elimination combined with polynomial fitting notably enhanced the model accuracy, reducing RE from −123 % to 20 %, increasing R2from 0.054 to 0.96, and improving PI from 2.6 to 1.16. As a result, the refined dataset provided a more consistent and realistic representation of the flow structure and established a robust observational basis for the future calibration.
- MakaleAçık Erişim2025Hydrodynamic optimization of full-scale aeration tanks using field measurements and computational fluid dynamics modeling
Yılmaz Çelik, Damla; Yılmaz, Naz; Şibil, Rahim; Aras, Egemen; Vaheddoost, Babak
Improving energy efficiency and operational performance in wastewater treatment plants largely relies on precise hydrodynamic analysis. In this context, field-based studies are essential for understanding system behavior under real operational conditions. This study was conducted at a full-scale wastewater treatment plant, where flow dynamics in the aeration tank were evaluated through extensive field measurements and computational fluid dynamics modeling. Data were collected from 98 locations across 15 different depth levels using an Acoustic Doppler Current Profiler and a Hach FH950 velocity meter. The numerical model was initially validated with the help of experimental field data, enabling an accurate assessment of flow characteristics at varying depths. Results revealed that the low-velocity zones and non-uniform velocity distributions negatively affect system performance. It is also concluded that the inlet and outlet positions disturb the favorable circulation patterns and flow uniformity. Geometric optimization strategies were implemented to develop solutions, which led to a more uniform velocity distribution and improved hydraulic efficiency. By integrating detailed field measurements with numerical modeling, this study provides a comprehensive understanding of aeration tank hydrodynamics and offers practical design recommendations for improving overall system performance.
- MakaleYalnız künye2021Comparison of various turbulence model performance in computational fluid dynamics analyses of the oxidation ditches with experimental validation
Şibil, Rahim; Aras, Egemen; Kankal, Murat
Experimental and numerical studies were carried out to determine the full-scale Oxidation Ditch (OD) hydrodynamics considering various turbulence models. Firstly, the experimental work was carried out in a full-scale plant by Acoustic Doppler Velocimeter (ADV) for field-measurements. Secondly, the experimental data was used to validate numerical models by using Computational Fluid Dynamics (CFD) software Ansys Fluent. Eight different turbulence models were compared in the numerical study to predict full-scale hydrodynamics. Results showed that standard k-ε, renormalization group k-ε, realizable k-ε turbulence models gave more accurate prediction results with relative errors of 13 %, 17 %, and 18 % respectively, whereas the standard k-ω turbulence model gave the worst prediction results with 39 % relative error. This study also shows that the velocities in the ODs are very low without external force such as air diffusers, rotors, and mixer and there is no homogeneous flow field distribution in the ODs. Moreover, the maximum wastewater velocities occurred at the inlet and outlet.
- MakaleAçık Erişim2021Experimental and numerical studies on predicting and improving the full-scale wastewater treatment plant hydrodynamics
Şibil, Rahim; Aras, Egemen; Kankal, Murat
This paper presents the results of both experimental and numerical studies on biological wastewater treatment plant (WWTP), oxidation ditches (OD) hydrodynamics to design and develop the desired flow conditions of the WWTP. Computational fluid dynamics (CFD) models were developed using CFD software, ANSYS Fluent (V13) with the three-dimensional, steady, incompressible flow based on the Reynolds-Averaged Navier-Stokes equations for flow field calculations in the combined ODs. Also, three different turbulence models [standard k–ε (ske), renormalization group k–ε (RNG), and realizable k–ε (real)] were performed for a comparative study. The numerical model was verified based on the experimental data in the relative errors for ske, RNG, and real 13%, 17%, and 18%, respec-tively. According to the parametric studies, the hydrodynamic characteristics of the existing WWTP were investigated. The maximum wastewater velocity occurred at the inlet and outlet, affecting the flow field in ODs. Moreover, the water velocity decreased as it moved away from the inlet and outlet locations at vertical and horizontal. It can also be noted that there was no homogeneous flow field distribution in ODs. Because the current OD model needs improvement hydrodynamically, a new original OD geometry was presented to eliminate the hydraulic weakness of existing WWTP by CFD analysis. The new original geometry provides a more homogeneous flow field in ODs that mean it will also help treatment efficiency and energy saving according to the operating principles of this facility.
- MakaleYalnız künye2011Solid waste management practices in Turkey
Berkun, Mehmet; Aras, Egemen; Anılan, Tugce
As an economically developing country, Turkey has very well operated integrated solid waste management applications structured on modern facilities, besides over 2,000 scattered open dump areas in the country. Integrated waste management applications seem eligible for the metropolitan cities like Istanbul and Izmit (Kocaeli). Attempts have not been encouraging for the scattered regional settlements using central storage sites due to financial shortages and received rejections from nearby settlements. Small-scale compact solid waste management systems with materials recycling and composting can be more suitable alternatives in the small-scale regional settlements. The major constituents of municipal solid waste are organic in nature and approximately a quarter of municipal solid waste is recyclable. Although paper, including cardboard, is the main constituent, the composition of recyclable waste varies strongly by the source or the type of collection point. Solid wastes need primary treatment in order to be suitable for incineration and composting. Turkey needs to give more emphasis on the usage of modern solid waste removal technologies to overcome the overgrowing solid waste disposal problems.
- MakaleYalnız künye2010Comparison of stepped and smooth spillway effects on stream reaeration
Aras, Egemen; Berkun, Mehmet
The oxygen transfer at a hydraulic structure happens by self-aeration through the spillway and by flow aeration in the hydraulic jump downstream of the hydraulic structure. Spillways with their water-air controlling mechanisms are important not only for their structural properties but also for their effects on stream ecology. Spillway types also affect the efficiency of aeration. Decisions on the types of spillway should be made by taking the environmental conditions and flow rates into consideration. This paper compares the aeration efficiency of stepped and smooth spillways. Empirical correlations predicting length of the non-aerated flow region and aeration efficiency are developed. Smooth and stepped spillways cause increased dissolved oxygen (DO) concentrations at the downstream part of the channel. DO concentration changes are shown to depend on the flow types, discharge rates, tail-water depth and travelling times.