Yildirim Suzen - Academia.edu (original) (raw)

Papers by Yildirim Suzen

Journal of turbomachinery, Mar 1, 2004

A new correlation-based transition model has been developed, which is built strictly on local var... more A new correlation-based transition model has been developed, which is built strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) methods using unstructured grids and massive parallel execution. The model is based on two transport equations, one for the intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models), but form a framework for the implementation of correlation-based models into general-purpose CFD methods. Part I of this paper (Menter, F. R., Langtry, R. B., Likki, S. R., Suzen, Y. B., Huang, P. G., and Völker, S., 2006, ASME J. Turbomach., 128(3), pp. 413–422) gives a detailed description of the mathematical formulation of the model and some of the basic test cases used for model validation. Part II (this part) details a significant number of test cases that have been used to validate the transition model for turbomachinery and aerodynamic applications, including the drag crisis of a cylinder, separation-induced transition on a circular leading edge, and natural transition on a wind turbine airfoil. Turbomachinery test cases include a highly loaded compressor cascade, a low-pressure turbine blade, a transonic turbine guide vane, a 3D annular compressor cascade, and unsteady transition due to wake impingement. In addition, predictions are shown for an actual industrial application, namely, a GE low-pressure turbine vane. In all cases, good agreement with the experiments could be achieved and the authors believe that the current model is a significant step forward in engineering transition modeling.

33rd AIAA Fluid Dynamics Conference and Exhibit, Jun 23, 2003

38th Aerospace Sciences Meeting and Exhibit, Jan 10, 2000

AIAA SCITECH 2022 Forum, Jan 3, 2022

SAE technical paper series, Aug 19, 2008

46th AIAA Aerospace Sciences Meeting and Exhibit, Jan 7, 2008

A recently introduced phenomenological model to simulate flow control applications using plasma a... more A recently introduced phenomenological model to simulate flow control applications using plasma actuators has been employed in numerical simulation of a low pressure turbine flow separation control experiment. Due to the tran sitional nature of these flowfields the simulations incorporated the transition model based on local variables. The effectiveness of plasma actuators in flow separation control are demonstrated numerically and the flexibility and capabilities of the new simulation methodology coupling the plasma actuator model with transition model are illustrated.

Journal of Turbomachinery-transactions of The Asme, Jun 1, 2006

44th AIAA Aerospace Sciences Meeting and Exhibit, Jan 9, 2006

A systematic approach of testing and validating transition models is developed and employed in te... more A systematic approach of testing and validating transition models is developed and employed in testing of a recently developed transition model. The testing methodology uses efficient computational tools and a wide range of test cases. The computational tools include a boundary layer code, single zone Navier Stokes solver, and a multi-block Navier Stokes solver which uses MPI and is capable of handling complex geometries and moving grids. Test cases include simple flat plate experiments, cascade experiments, and unsteady wake/blade interaction experiments. The test cases are used to test the predicting capabilities of the transition model under various effects such as free stream turbulence intensity, Reynolds number variations, pressure gradient, flow separation, and unsteady wake/blade interaction. Using the above test cases and computational tools a method is developed to validate transition models. The transition model is first implemented in boundary layer code and tested for simple flat plate cases. Then the transition model is implemented in single zone Navier Stokes solver and tested for hysteresis effects for flat plate cases. Finally the transition model is implemented in multi zone Navier Stokes solver and tested for compressor and turbine cascade cases followed by unsteady wake/blade interaction experiments. Using the method developed a new correlation based transition model (Menter et al. 2004) which uses local variables is tested and validated. The new model predicted good results for high free stream turbulence and high Reynolds number cases. For low free stream turbulence and low Reynolds number cases, the results were satisfactory.

Journal of Fluids Engineering-transactions of The Asme, Feb 8, 2000

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37th AIAA Fluid Dynamics Conference and Exhibit, Jun 15, 2007

The use of actuators has been seen as an effective means for controlling flow over plates, airfoi... more The use of actuators has been seen as an effective means for controlling flow over plates, airfoils, and turbine blades. The use of plasma actuators is attractive since they lack moving parts and can be easily integrated onto different geometries. The potential capabilities of plasma actuators for boundary layer control have been demonstrated in numerous experiments. This boundary layer control is driven by a body force vector nearly tangent to the surface above the embedded electrode of the actuator. To study the effects of these actuators numerically, the computational model must solve both the electromagnetic and Navier–Stokes equations. Such a model has been inserted into an unstructured computational fluid dynamics code and initial tests conduced on linear plasma actuators.

This research is focused on the effects of large changes in Reynolds number that typically occurs... more This research is focused on the effects of large changes in Reynolds number that typically occurs during the flight of high altitude UAV’s. This paper documents the influence of Reynolds number, turbulence level, and exit Mach number on the vane surface Stanton number. Reynolds number is based on true chord and exit conditions and ranges from 90,000 through 1,000,000. Low and high inlet turbulence levels were developed for the study and determined to be 0.8% and 9.0%. Tests were run at exit Mach numbers of 0.7, 0.8 and 0.9. These surface heat transfer measurements were acquired in the University of North Dakota’s transonic cascade test facility. This facility uses a closed loop to allow the regulation of system pressure to control the test condition Reynolds number. The Mach number is adjusted using a “roots” blower driven by a variable frequency drive. Heat transfer measurements were acquired using a constant heat flux foil fabricated using a 0.023 mm Inconel foil backed with 0.05 mm of Kapton and adhered to the heat transfer vane using a high temperature acrylic adhesive. The linear cascade is configured in a four vane three full passage arrangement. The low turbulence condition is developed using the existing flow conditioning section coupled to a 4.7 to 1 area ratio nozzle. The high turbulence condition uses a mock aero combustor to generate a turbulence level of around 9.0%. These data show the influence of Mach number, Reynolds number and turbulence level on transition and heat transfer augmentation and are expected to be useful in grounding heat transfer predictive methods applicable to small or high altitude gas turbine engines.

The influence of low to moderate Reynolds number and low to moderate turbulence level on aerodyna... more The influence of low to moderate Reynolds number and low to moderate turbulence level on aerodynamic losses is investigated in an incidence tolerant turbine blade cascade for a variable speed power turbine. This work complements midspan heat transfer and blade loading measurements which are acquired in the same cascade at the same conditions. The aerodynamic loss measurements are acquired to quantify the influence of Reynolds number and turbulence level on blade loss buckets over the wide range of incidence angles for the variable speed turbine. Eight discrete incidence angles are investigated ranging from +5.8° to −51.2°. Noting that the design inlet angle of the blade is 34.2° these incidence angles correspond to inlet angles ranging from +40° to −17°. Exit loss surveys, presented in terms of local total pressure loss and secondary velocities have been acquired at four exit chord Reynolds numbers ranging from 50,000 to 568,000. These measurements were acquired at both low (∼0.4%) and moderate (∼4.0%) inlet turbulence intensities. The total pressure losses are also presented in terms of cross passage averaged loss and turning angle. The resulting loss buckets for passage averaged losses are plotted at varied Reynolds numbers and turbulence condition. The exit loss data quantify the impact of Reynolds number and incidence angle on aerodynamic losses. Generally, these data document the substantial deterioration of performance with decreasing Reynolds number.

AIAA SCITECH 2023 Forum, Jan 19, 2023

Midspan heat transfer and pressure measurements have been acquired in a steady state transonic li... more Midspan heat transfer and pressure measurements have been acquired in a steady state transonic linear cascade at low to moderate Reynolds numbers. These results were used to investigate boundary layer development and separation on a 2-D variable-speed power turbine rotor blade. These distributions were acquired at 8 separate incidence angles ranging from +5.8 to – 51.2. At each angle measurements were acquired at four Reynolds numbers ranging from 50,000 to 568,000 based on true chord and exit conditions. These four Reynolds number cases were tested at the design exit Mach number of 0.72. Reynolds numbers of 228,000 and 568,000 were also run for selected angles at an exit Mach number of 0.35 to constitute match points for similar measurements which were conducted at NASA Glenn. These measurements were conducted at both a lower (~0.4%) and a higher (~4%) turbulence condition. The surface pressure distributions are plotted in terms of local isentropic Mach number. They show changes in loading, the movement of the stagnation line, and regions of separation with changing incidence angle and Reynolds number. Heat transfer measurements show areas of laminar flow, regions of transition, locations of separation as well as information on reattachment.

Fluids 2000 Conference and Exhibit, Jun 19, 2000

42nd AIAA Aerospace Sciences Meeting and Exhibit, Jan 5, 2004

ABSTRACT