Experimental and numerical studies of the flow around the Ahmed body

Tunay, Tural,Sahin, Besir,Akilli, Huseyin Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.5

The present study aims to investigate characteristics of the flow structures around the Ahmed body by using both experimental and numerical methods. Therefore, 1/4 scale Ahmed body having $25^{\circ}$ slant angle was employed. The Reynolds number based on the body height, H and the free stream velocity, U was $Re_H=1.48{\times}10^4$. Investigations were conducted in two parts. In the first part of the study, Large Eddy Simulation (LES) method was used to resolve the flow structures around the Ahmed body, numerically. In the second part of the study the particle image velocimetry (PIV) technique was used to measure instantaneous velocity fields around the Ahmed body. Time-averaged and instantaneous velocity vectors maps, streamline topology and vorticity contours of the flow fields were presented and discussed in details. Comparison of the mean and turbulent quantities of the LES results and the PIV results with the results of Lienhart et al. (2000) at different locations over the slanted surface and in the wake region of the Ahmed body were also given. Flow features such as critical points and recirculation zones in the wake region downstream of the Ahmed body were well captured. The spectra of numerically and experimentally obtained stream-wise and vertical velocity fluctuations were presented and they show good consistency with the numerical result of Minguez et al. (2008).

Experimental and numerical studies of the flow around the Ahmed body

Tural Tunay,Besir Sahin,Huseyin Akilli 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.17 No.5

The present study aims to investigate characteristics of the flow structures around the Ahmed body by using both experimental and numerical methods. Therefore, ¼ scale Ahmed body having 25o slant angle was employed. The Reynolds number based on the body height, H and the free stream velocity, U was ReH=1.48x104. Investigations were conducted in two parts. In the first part of the study, Large Eddy Simulation (LES) method was used to resolve the flow structures around the Ahmed body, numerically. In the second part of the study the particle image velocimetry (PIV) technique was used to measure instantaneous velocity fields around the Ahmed body. Time-averaged and instantaneous velocity vectors maps, streamline topology and vorticity contours of the flow fields were presented and discussed in details. Comparison of the mean and turbulent quantities of the LES results and the PIV results with the results of Lienhart et al. (2000) at different locations over the slanted surface and in the wake region of the Ahmed body were also given. Flow features such as critical points and recirculation zones in the wake region downstream of the Ahmed body were well captured. The spectra of numerically and experimentally obtained stream-wise and vertical velocity fluctuations were presented and they show good consistency with the numerical result of Minguez et al. (2008).

The presence of MEFV gene mutations in patients with primary osteoarthritis who require surgery

( Sedat Yilmaz ),( Hakan Erdem ),( Servet Tunay ),( Deniz Torun ),( Halil Genc ),( Yusuf Tunca ),( Omer Karadag ),( Ismail Simsek ),( Muhterem Bahce ),( Salih Pay ),( Ayhan Dinc ) 대한내과학회 2013 The Korean Journal of Internal Medicine Vol.28 No.5

Background/Aims: Chronic arthritis of familial Mediterranean fever (FMF) involves weight-bearing joints and can occur in patients without a history of acute attack. Our aim was to investigate a possible causal relationship between FMF and osteoarthritis in a population in which FMF is quite common. Methods: Patients with late stage primary osteoarthritis were enrolled, and five MEFV gene mutations were investigated. The frequency of MEFV gene mutations was compared among patients with osteoarthritis and a previous healthy group from our center. Results: One hundred patients with primary osteoarthritis and 100 healthy controls were studied. The frequency of MEFV gene mutations was significantly lower in the osteoarthritis group (9% vs. 19%). M694V was the most frequent mutation (5%) in the osteoarthritis group, whereas in the control group, E148Q was the most common (16%). In subgroup analyses, the mutation frequency of patients with hip osteoarthritis was not different from that of patients with knee osteoarthritis and controls (7.1%, 9.7%, and 19%, respectively). There were no differences among the three groups with respect to MEFV gene mutations other than E148Q (8.1% vs. 3.6%). E148Q was significantly lower in the osteoarthritis group than in the controls (16% vs. 1%), although the mutations did not differ between patients with knee osteoarthritis and controls. Conclusions: In a population with a high prevalence of MEFV gene mutations, we did not find an increased mutation rate in patients with primary osteoarthritis. Furthermore, we found that some mutations were significantly less frequent in patients with osteoarthritis. Although the number of patients studied was insufficient to claim that E148Q gene mutation protects against osteoarthritis, the potential of this gene merits further investigation.

Friction and Wear Properties of Cu and Fe-based P/M Bearing Materials

Tufekci Kenan,Kurbanoglu Cahit,Durak Ertugrul,Tunay R. Fatih The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4

The performances of porous bearings under different operating conditions were experimentally investigated in this study. Material groups studied are 90%Cu + 10%Sn bronze and 1%C + % balance Fe iron-based self-lubricating P/M bearings at constant (85%) density. In the experiments, the variation of the coefficient of friction and wear ratio of those two different group materials for different sliding speeds, loads, and temperatures were investigated. As a result, the variation of the friction coefficient-temperature for both constant load, and constant sliding speed, friction coefficient-average bearing pressure, PV-wear loss and temperature-wear loss curves were plotted and compared with each other for two materials, separately. The test results showed that Cu-based bearings have better friction and wear properties than Fe-based bearings.

Turkish Version of Kolcaba's Immobilization Comfort Questionnaire: A Validity and Reliability Study

Betül Tosun,Ozlem Aslan,Servet Tunay,Aygül Akyüz,Hüseyin Ozkan,Dogan Bek,Semra Açıksoz 한국간호과학회 2015 Asian Nursing Research Vol.9 No.4

Purpose: The purpose of this study was to determine the validity and reliability of the Turkish version of the Immobilization Comfort Questionnaire (ICQ). Methods: The sample used in this methodological study consisted of 121 patients undergoing lower extremity arthroscopy in a training and research hospital. The validity study of the questionnaire assessed language validity, structural validity and criterion validity. Structural validity was evaluated via exploratory factor analysis. Criterion validity was evaluated by assessing the correlation between the visual analog scale (VAS) scores (i.e., the comfort and pain VAS scores) and the ICQ scores using Spearman's correlation test. The Kaiser-Meyer-Olkin coefficient and Bartlett's test of sphericity were used to determine the suitability of the data for factor analysis. Internal consistency was evaluated to determine reliability. The data were analyzed with SPSS version 15.00 for Windows. Descriptive statistics were presented as frequencies, percentages, means and standard deviations. A p value .05 was considered statistically significant. Results: A moderate positive correlation was found between the ICQ scores and the VAS comfort scores; a moderate negative correlation was found between the ICQ and the VAS pain measures in the criterion validity analysis. Cronbach a values of .75 and .82 were found for the first and second measurements, respectively. Conclusions: The findings of this study reveal that the ICQ is a valid and reliable tool for assessing the comfort of patients in Turkey who are immobilized because of lower extremity orthopedic problems.

$H_2O_2$/UV-C oxidation of potential endocrine disrupting compounds: a case study with dimethyl phthalate

Olmez-Hanci, Tugba,Imren, Ceren,Arslan-Alaton, Idil,Kabdasli, Isik,Tunay, Olcay Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.5

This paper discusses the feasibility of the ultraviolet radiation-hydrogen peroxide ($H_2O_2$/UV-C) process as an advanced oxidation process (AOP) in the treatment of endocrine disrupting compounds (EDC). Dimethyl phthalate (DMP) was chosen as the model compound owing to its classification as an EDC. Experiments have been conducted at various pH values (3.5, 6.0 and 9.0) and initial $H_2O_2$ concentrations (0-60 mM) in a batch reactor equipped with a low-pressure mercury UV-C lamp in order to evaluate the optimal operation conditions of the $H_2O_2$/UV-C process. The most effective pH value for the degradation of DMP by $H_2O_2$/UV-C treatment was found as 6.0. DMP abatement increased with increasing $H_2O_2$ concentrations from 5 to 30 mM. Further increase in initial $H_2O_2$ concentration, however, reduced both the rate and extent of DMP removal as well as chemical oxygen demand (COD) and total organic carbon (TOC) removals. A simple kinetic model was proposed for DMP, COD and TOC abatements confirmed pseudo-first-order reaction. The electrical energy per order (EE/O) values for DMP oxidation and TOC mineralization were calculated as 3.3 and $19\;kWh\;m^{-3}\;order^{-1}$ respectively for the optimum treatment conditions ($H_2O_{2,o}$ = 30 mM, $pH_o$ = 6.0, $DMP_{o}\;=\;100\;mg\;L^{-1}$). Inhibition of oxygen uptake rate by activated sludge (ISO 8192) was evaluated as a tool for assessing the acute toxicity of untreated and $H_2O_2$/UV-C treated DMP. According to the results obtained in this work, the use of the $H_2O_2$/UV-C process is recommended to achieve a complete DMP oxidation and high mineralization degree of aqueous solution of DMP.

Friction and Wear Properties of Cu and Fe-based P/M Bearing Materials

Kenan TUFEKCI,Cahit KURBANO?LU,Ertu?rul DURAK,R. Fatih TUNAY 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4

The performances of porous bearings under different operating conditions were experimentally investigated in this study. Material groups studied are 90%Cu+10%Sn bronze and 1%C+% balance Fe iron-based self-lubricating P/M bearings at constant (85%) density. In the experiments, the variation of the coefficient of friction and wear ratio of those two different group materials for different sliding speeds, loads, and temperatures were investigated. As a result, the variation of the friction coefficient - temperature for both constant load, and constant sliding speed, friction coefficient - average bearing pressure, PV - wear loss and temperature-wear loss curves were plotted and compared with each other for two materials, separately. The test results showed that Cu-based bearings have better friction and wear properties than Fe-based bearings.