Large eddy simulation of a square cylinder flow: Modelling of inflow turbulence

Tutar, M.,Celik, I. Techno-Press 2007 Wind and Structures, An International Journal (WAS Vol.10 No.6

The present study aims to generate turbulent inflow data to more accurately represent the turbulent flow around a square cylinder when the inflow turbulence level is significant. The modified random flow generation (RFG) technique in conjunction with a previously developed LES code is successfully adopted into a finite element based fluid flow solver to generate the required inflow turbulence boundary conditions for the three-dimensional (3-D) LES computations of transitional turbulent flow around a square cylinder at Reynolds number of 22,000. The near wall region is modelled without using wall approximate conditions and a wall damping coefficient is introduced into the calculation of sub-grid length scale in the boundary layer of the cylinder wall. The numerical results obtained from simulations are compared with each other and with the experimental data for different inflow turbulence boundary conditions in order to discuss the issues such as the synthetic inflow turbulence effects on the 3-D transitional flow behaviour in the near wake and the free shear layer, the basic mechanism by which stream turbulence interacts with the mean flow over the cylinder body and the prediction of integral flow parameters. The comparison among the LES results with and without inflow turbulence and the experimental data emphasizes that the turbulent inflow data generated by the present RFG technique for the LES computation can be a viable approach in accurately predicting the effects of inflow turbulence on the near wake turbulent flow characteristics around a bluff body.

Large eddy simulation of a square cylinder flow: Modelling of inflow turbulence

M. Tutar,I. Celik 한국풍공학회 2007 Wind and Structures, An International Journal (WAS Vol.10 No.6

The present study aims to generate turbulent inflow data to more accurately represent the turbulent flow around a square cylinder when the inflow turbulence level is significant. The modified random flow generation (RFG) technique in conjunction with a previously developed LES code is successfully adopted into a finite element based fluid flow solver to generate the required inflow turbulence boundary conditions for the three-dimensional (3-D) LES computations of transitional turbulent flow around a square cylinder at Reynolds number of 22,000. The near wall region is modelled without using wall approximate conditions and a wall damping coefficient is introduced into the calculation of sub-grid length scale in the boundary layer of the cylinder wall. The numerical results obtained from simulations are compared with each other and with the experimental data for different inflow turbulence boundary conditions in order to discuss the issues such as the synthetic inflow turbulence effects on the 3-D transitional flow behaviour in the near wake and the free shear layer, the basic mechanism by which stream turbulence interacts with the mean flow over the cylinder body and the prediction of integral flow parameters. The comparison among the LES results with and without inflow turbulence and the experimental data emphasizes that the turbulent inflow data generated by the present RFG technique for the LES computation can be a viable approach in accurately predicting the effects of inflow turbulence on the near wake turbulent flow characteristics around a bluff body.

Computational study of a small scale vertical axis wind turbine (VAWT): comparative performance of various turbulence models

Aresti, Lazaros,Tutar, Mustafa,Chen, Yong,Calay, Rajnish K. Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.6

The paper presents a numerical approach to study of fluid flow characteristics and to predict performance of wind turbines. The numerical model is based on Finite-volume method (FVM) discretization of unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The movement of turbine blades is modeled using moving mesh technique. The turbulence is modeled using commonly used turbulence models: Renormalization Group (RNG) k-${\varepsilon}$ turbulence model and the standard k-${\varepsilon}$ and k-${\omega}$ turbulence models. The model is validated with the experimental data over a large range of tip-speed to wind ratio (TSR) and blade pitch angles. In order to demonstrate the use of numerical method as a tool for designing wind turbines, two dimensional (2-D) and three-dimensional (3-D) simulations are carried out to study the flow through a small scale Darrieus type H-rotor Vertical Axis Wind Turbine (VAWT). The flows predictions are used to determine the performance of the turbine. The turbine consists of 3-symmetrical NACA0022 blades. A number of simulations are performed for a range of approaching angles and wind speeds. This numerical study highlights the concerns with the self-starting capabilities of the present VAWT turbine. However results also indicate that self-starting capabilities of the turbine can be increased when the mounted angle of attack of the blades is increased. The 2-D simulations using the presented model can successfully be used at preliminary stage of turbine design to compare performance of the turbine for different design and operating parameters, whereas 3-D studies are preferred for the final design.

Neutrophil-lymphocyte Ratio Findings and Larynx Carcinoma: a Preliminary Study in Turkey

Duzlu, Mehmet,Karamert, Recep,Tutar, Hakan,Karaloglu, Furkan,Sahin, Melih,Cevizci, Rasit Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.1

Background: To identify the potential prognostic role of the neutrophil/lymphocyte (N/L) ratio in larynx carcinoma. Materials and Methods: Oncologic archive charts of patients with a larynx carcinoma diagnosis between the years 2010 and 2013 were retrospectively reviewed. The inclusion criterion was to be available with hemogram test prior to diagnostic procedure. Patients undergoing septorinoplasty comprised the control group. Results: There were 65 cases in the study and 42 cases in control group meeting inclusion criteria. In general a non-significant increase in N/L ratio was observed with increasing tumor size and stage (p>0.05) in larynx carcinoma. The N/L ratio was found to be significantly higher in larynx carcinoma compared to control group (p=0.004). Conclusions: In conclusion, the N/L ratio was shown to be significantly increased in larynx carcinomas compared to control group. Further studies are needed to assess any prognostic role.

Computational study of a small scale vertical axis wind turbine (VAWT): comparative performance of various turbulence models

Lazaros Aresti,Mustafa Tutar,Yong Chen,Rajnish K. Calay 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.17 No.6

The paper presents a numerical approach to study of fluid flow characteristics and to predict performance of wind turbines. The numerical model is based on Finite-volume method (FVM) discretization of unsteady Reynolds-averaged Navier- Stokes (URANS) equations. The movement of turbine blades is modeled using moving mesh technique. The turbulence is modeled using commonly used turbulence models: Renormalization Group (RNG) k- turbulence model and the standard k- and k- turbulence models. The model is validated with the experimental data over a large range of tip-speed to wind ratio (TSR) and blade pitch angles. In order to demonstrate the use of numerical method as a tool for designing wind turbines, two dimensional (2-D) and three-dimensional (3-D) simulations are carried out to study the flow through a small scale Darrieus type H-rotor Vertical Axis Wind Turbine (VAWT). The flows predictions are used to determine the performance of the turbine. The turbine consists of 3- symmetrical NACA0022 blades. A number of simulations are performed for a range of approaching angles and wind speeds. This numerical study highlights the concerns with the self-starting capabilities of the present VAWT turbine. However results also indicate that self-starting capabilities of the turbine can be increased when the mounted angle of attack of the blades is increased. The 2-D simulations using the presented model can successfully be used at preliminary stage of turbine design to compare performance of the turbine for different design and operating parameters, whereas 3-D studies are preferred for the final design.

CASE REPORT : Aneurysmal Bone Cyst of Sphenoid Bone and Clivus Misdiagnosed as Chordoma: A Case Report

( Fethi Emre Ustabasioglu ),( Cesur Samanci ),( Murat Asik ),( Inanc Yanik ),( Seyma Ozkanli ),( Onur Tutar ),( Zehra Isik Hasiloglu ) 대한뇌종양학회·대한신경종양학회 2015 Brain Tumor Research and Treatment Vol.3 No.2

Aneurysmal bone cysts (ABCs) are benign and rapidly expanding bone destructive lesions of any bone. They are commonly localized in the metaphysis of long bones, whereas skull base ABCs are rare. We report a case of a 21-year-old man who had been misdiagnosed as chordoma and undergone surgery. However, histopathological examination revealed it to be an ABC.