Yazar "Ozgoren, Muammer" seçeneğine göre listele
Listeleniyor 1 - 16 / 16
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Artificial Frame Filling Using Adaptive Neural Fuzzy Inference System for Particle Image Velocimetry Dataset(SPIE-INT SOC OPTICAL ENGINEERING, 2015) Akdemir, Bayram; Dogan, Sercan; Aksoy, Muharrem Hilmi; Canli, Eyup; Ozgoren, MuammerLiquid behaviors are very important for many areas especially for Mechanical Engineering. Fast camera is a way to observe and search the liquid behaviors. Camera traces the dust or colored markers travelling in the liquid and takes many pictures in a second as possible as. Every image has large data structure due to resolution. For fast liquid velocity, there is not easy to evaluate or make a fluent frame after the taken images. Artificial intelligence has much popularity in science to solve the nonlinear problems. Adaptive neural fuzzy inference system is a common artificial intelligence in literature. Any particle velocity in a liquid has two dimension speed and its derivatives. Adaptive Neural Fuzzy Inference System has been used to create an artificial frame between previous and post frames as offline. Adaptive neural fuzzy inference system uses velocities and vorticities to create a crossing point vector between previous and post points. In this study, Adaptive Neural Fuzzy Inference System has been used to fill virtual frames among the real frames in order to improve image continuity. So this evaluation makes the images much understandable at chaotic or vorticity points. After executed adaptive neural fuzzy inference system, the image dataset increase two times and has a sequence as virtual and real, respectively. The obtained success is evaluated using R-2 testing and mean squared error. R2 testing has a statistical importance about similarity and 0.82, 0.81, 0.85 and 0.8 were obtained for velocities and derivatives, respectively.Öğe AN ASSESSMENT OF WIND ENERGY POTENTIAL TO MEET ELECTRICITY DEMAND AND ECONOMIC FEASIBILITY IN KONYA, TURKEY(TAYLOR & FRANCIS INC, 2014) Kose, Faruk; Aksoy, Muharrem Hilmi; Ozgoren, MuammerIn this study, wind energy potential of Selcuk University campus region was investigated by means of wind data, which were obtained locally from a special observation station. The wind data were collected during the year 2005 at three different heights and were statistically analyzed with the help of MS office, Alwin, Wasp, and Witerm software. It is obtained that yearly averaged wind velocities of the region in 2005 at 10, 20, and 40 m of the mass height were found to be 5.36, 5.40, and 6.05 m/s, respectively. The power density of the region at 40 m was in the range of 260-308 W/m(2) with a medium level. For consideration of the calculation, wind speed frequency histogram, Rayleigh and Weibull distributions, wind direction, and temperature data were also used. The obtained results were used for evaluating electricity production of a 6 MW capacity wind farm composed of 1.0, 1.5, and 2.0 MW wind turbines. In addition, the planned wind farm was economically evaluated by means of the basic payback, the net present value, and the internal rate of return methods. The minimum basic payback period was found to be 6.44 years. The results were discussed and interpreted to encourage the investors for establishing wind farm in the region.Öğe Comparison of flow characteristics around an equilateral triangular cylinder via PIV and Large Eddy Simulation methods(ELSEVIER SCI LTD, 2017) Yagmur, Sercan; Dogan, Sercan; Aksoy, Muharrem Hilmi; Goktepeli, Ilker; Ozgoren, MuammerThe flow structures around an equilateral triangular Cylinder, which is commonly used as a vortex shedder in the vortex flowmeter, were investigated experimentally and numerically. Flow characteristics such as voracity contours, patterns of sectional streamlines, velocity vectors, velocity fields, Reynolds stress correlations, Strouhal numbers and drag coefficients were examined using the Particle Image Velocimetry (PIV) technique and the Large Eddy Simulation (LES) turbulence model. Experimental studies were performed in an open water channel for Re= 2.9 x 10(3), Re= 5.8 x 10(3) and Re = 1.16 x 10(4) based on the equilateral triangle edge. A sharp-tip corner of the cylinder with a triangle cross-section was exposed to the upstream side while the other two sharp -tip corners were placed on the downstream side. Numerical studies were also completed at Reynolds numbers in the range of 2.9 x 103 <= Re <= 1.16 x 10(5) to obtain the changes in the Strouhal numbers and drag coefficients. When the results of PIV and LES are considered in the same interval of Reynolds numbers, the maximum and minimum values of each flow pattern were nearly the same. The time -averaged patterns had considerable symmetry with respect to the axis line passing through the sharp -tip corner of the cross-section of the triangular cylinder. The Strouhal number was independent of the Reynolds number and was found to be approximately 0.22. The drag coefficient decreased with increasing Reynolds numbers while increasing the Power Spectral Density (PSD) and the vortex shedding frequency. For the same Reynolds numbers, the experimental and numerical results were in good agreement. Therefore, the LES turbulence model is recommended for applications of flow around this type of bluff body that is generally used in the design of vortex flowmeters to generate vortex shedding.Öğe Daily total global solar radiation modeling from several meteorological data(SPRINGER WIEN, 2011) Bilgili, Mehmet; Ozgoren, MuammerThis paper investigates the modeling of the daily total global solar radiation in Adana city of Turkey using multi-linear regression (MLR), multi-nonlinear regression (MNLR) and feed-forward artificial neural network (ANN) methods. Several daily meteorological data, i.e., measured sunshine duration, air temperature and wind speed and date of the year, i.e., monthly and daily, were used as independent variables to the MLR, MNLR and ANN models. In order to determine the relationship between the total global solar radiation and other meteorological data, and also to obtain the best independent variables, the MLR and MNLR analyses were performed with the "Stepwise" method in the Statistical Packages for the Social Sciences (SPSS) program. Thus, various models consisting of the combination of the independent variables were constructed and the best input structure was investigated. The performances of all models in the training and testing data sets were compared with the measured daily global solar radiation values. The obtained results indicated that the ANN method was better than the other methods in modeling daily total global solar radiation. For the ANN model, mean absolute error (MAE), mean absolute percentage error (MAPE), correlation coefficient (R) and coefficient of determination (R (2)) for the training/testing data set were found to be 0.89/1.00 MJ/m(2) day, 7.88/9.23%, 0.9824/0.9751, and 0.9651/0.9508, respectively.Öğe Estimation of global solar radiation using ANN over Turkey(PERGAMON-ELSEVIER SCIENCE LTD, 2012) Ozgoren, Muammer; Bilgili, Mehmet; Sahin, BesirThe main objective of the present study is to develop an artificial neural network (ANN) model based on multi-nonlinear regression (MNLR) method for estimating the monthly mean daily sum global solar radiation at any place of Turkey. For this purpose, the meteorological data of 31 stations spread over Turkey along the years 2000-2006 were used as training (27 stations) and testing (4 stations) data. Firstly, all independent variables (latitude, longitude, altitude, month, monthly minimum atmospheric temperature, maximum atmospheric temperature, mean atmospheric temperature, soil temperature, relative humidity, wind speed, rainfall, atmospheric pressure, vapor pressure, cloudiness and sunshine duration) were added to the Enter regression model. Then, the Stepwise MNLR method was applied to determine the most suitable independent (input) variables. With the use of these input variables, the results obtained by the ANN model were compared with the actual data, and error values were found within acceptable limits. The mean absolute percentage error (MAPE) was found to be 5.34% and correlation coefficient (R) value was obtained to be about 0.9936 for the testing data set. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.Öğe Experimental and CFD investigation of a multistage centrifugal pump including leakages and balance holes(DESALINATION PUBL, 2017) Babayigit, Osman; Ozgoren, Muammer; Aksoy, Muharrem Hilmi; Kocaaslan, OsmanThe aim of this study is to analyze numerically a multistage pump with some new approaches and compare the results with experimental data. A centrifugal pump, consisting of six backward curved blades, ten vane diffusers and two stages, was used. First, models of an impeller, a diffuser, suction and discharge sections of the centrifugal pump were separately designed by empirical equations. The flow volume of the pump was numerically solved by different turbulence models. Thus, the most accurate results in comparison with experimental data were obtained for the realizable k-epsilon turbulence model. For the purposes of this study, the effect of balance holes and leakages (clearances) on the performance was scrutinized. In most studies, it is not taken into consideration in computational fluid dynamics (CFD) analyses due to the difficulty of meshing these regions. The experimental studies were performed at a computer controlled pump test rig that was established according to the standard TS EN ISO 9906. The results of CFD/experimental analyses for the pump head, hydraulic efficiency and hydraulic power on the design point, having the flow rate of 80 m(3)/h and the revolution of 2,975 rpm, were found to be 81.47/80.70 m, 51.98%/51.42% and 17.94/17.77 kW, respectively. The obtained CFD and experimental results were found to be close agreement for the design flow rate as well as for all tested flow rates. Other characteristics of the pump such as velocity, static pressure, streamline patterns and turbulence kinetic energy were also investigated. In addition, the leakages and balance holes have significantly affected the pump characteristics, which must be considered in CFD analyses in order to find more precise results for true-to-life simulations.Öğe FLOW STRUCTURE FROM A HORIZONTAL CYLINDER COINCIDENT WITH A FREE SURFACE IN SHALLOW WATER FLOW(VINCA INST NUCLEAR SCI, 2012) Kahraman, Ali; Ozgoren, Muammer; Sahin, BesirVortex formation from a horizontal cylinder coincident with a free surface of a shallow water flow having a depth of 25.4 mm was experimentally investigated using the particle image velocimetry technique. Instantaneous and time-averaged flow patterns in the wake region of the cylinder were examined for three different cylinder diameter values under the fully developed turbulent boundary layer condition. Reynolds numbers were in the range of 1124 <= Re <= 3374 and Froude numbers were in the range of 0.41 <= Fr <= 0.71 based on the cylinder diameter. It was found that a jet-like flow giving rise to increasing the flow entrainment between the core and wake regions depending on the cylinder diameter was formed between the lower surface of the cylinder and bottom surface of the channel. Vorticity intensity, Reynolds stress correlations, and the primary recirculating bubble lengths were grown to higher values with increasing the cylinder diameter. On the other hand, in the case of the lowest level of the jet-like flow emanating from the beneath of the smallest cylinder, the variation of flow characteristics were attenuated significantly in a shorter distance. The variation of the reattachment location of the separated flow to the free-surface is a strong function of the cylinder diameter and the Froude number.Öğe Flow structures around an equilateral triangle arrangement of three spheres(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Ozgoren, MuammerThis paper represents the results of an experimental study on the flow structure around a single sphere and three spheres in an equilateral-triangular arrangement. Flow field measurements were performed using a Particle Image Velocimetry (PIV) technique and dye visualization in an open water channel for a Reynolds number of Re = 5 x 10(3) based on the sphere diameter. The distributions and flow features at the critical locations of the contours of the velocity fluctuations, the patterns of sectional streamlines, the vorticity contours, the turbulent kinetic energy, the Reynolds stress correlations and shedding frequency are discussed. The gap ratios (G/D) of the three spheres were varied in the range of 1.0 <= G/D <= 2.5 where G was the distance between the sphere centers, and D was the sphere diameter which was taken as 30 mm. Due to the interference of the shedding shear layers and the wakes, more complex features of the flow patterns can be found in the wake region of the two downstream spheres behind the leading sphere. For G/D = 1.25, a jet-like flow around the leading sphere through the gap between the two downstream spheres occurred, which significantly enhanced the wake region. It was observed that a continuous flow development involving shearing phenomena and the interactions of shedding vortices caused a high rate of fluctuations over the whole flow field although most of the time-averaged flow patterns were almost symmetric about the two downstream spheres. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Hourly cooling load prediction of a vehicle in the southern region of Turkey by Artificial Neural Network(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Solmaz, Ozgur; Ozgoren, Muammer; Aksoy, Muharrem HilmiIn this study, Artificial Neural Networks (ANNs) method for prediction hourly cooling load of a vehicle was implemented. The cooling load of the vehicle was calculated along the cooling season (1 May-30 September) for Antalya, Konya, Mersin, Mugla and Sanliurfa provinces in Turkey. For ANN model, seven neurons determinated as input signals of latitude, longitude, altitude, day of the year, hour of the day, hourly mean ambient air temperature and hourly solar radiation were used for the input layer of the network. One neuron producing an output signal of the hourly cooling load was utilized in the output layer. All data were divided into two categories for training and testing of the ANN. The 80% of the data was reserved to training and the remaining was used for testing of the model. Neuron numbers in the hidden layer from 7 to 40 were tested step by step to find the best matching ANN structure. The obtained results for different numbers of neurons were compared in terms of root mean squared error (RMSE), coefficient of determination (R-2) and mean absolute error (MAE). The best matching results for the training and testing were obtained as 8 neurons for the minimum testing RMSE value for the prediction of cooling load by the ANN model on the 23rd day of each month along the cooling season. For the model with 8 neurons RMSE, R-2 and MAE (Training/Testing) were found to be 0.0128/0.0259, 0.9959/0.9818 and 78.81/174.71 W/m(2), respectively. It is shown that the cooling load of a vehicle can be successfully predicted by means of the ANNs from geographical characteristics and meteorological data. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Large eddy simulation of flow around two side-by-side spheres(KOREAN SOC MECHANICAL ENGINEERS, 2013) Hassanzadeh, Rahim; Sahin, Besir; Ozgoren, MuammerLarge eddy simulation, using a dynamic Smagorinsky sub-grid scale, is used for the prediction of flow structures around two identical spheres fixed side-by-side at a subcritical flow regime with the Reynolds number equal to 5,000. The QUICK discretization method is applied to discretize the convection terms of the Navier-Stokes equation by means of the finite volume approach. This work focuses mainly on the wake structures downstream of the two interactive spheres located at three various dimensionless separation distances between spheres such as G/D = 1.50, 2.00, and 3.00. The obtained results revealed that the interaction between wakes affects the flow structures downstream of spheres. The rate of this interaction is strongly altered as a function of separation distance. On the other hand, some flow data such as mean drag and mean lift coefficients are affected due to the wake interactions. Finally, examination of the Reynolds stress variation along the different lateral axis, L/D, revealed that the nozzle effect does not play a significant role on the turbulence characteristics beyond the G/D = 3.00.Öğe Numerical identification of blade exit angle effect on the performance for a multistage centrifugal pump impeller(E D P SCIENCES, 2015) Babayigit, Osman; Kocaaslan, Osman; Aksoy, Muharrem Hilmi; Guleren, Kursad Melih; Ozgoren, MuammerNowadays, single and multistage centrifugal pumps are widely used in industrial and mining enterprises. One of the most important components of a centrifugal pump is the impeller. The performance characteristics are related to the pump comprising the head and the overall efficiency rely a great deal on the impeller geometry. In this work, effects of blade exit angle change on hydraulic efficiency of a multi stage pump impeller are investigated via Ansys-Fluent computational fluid dynamics software for constant width impeller entrance and exit gates, blade numbers and blade thickness. Firstly, the flow volume of a centrifugal pump impeller is generated and then mesh structure is formed for the full impeller flow volume. Secondly, rotational periodic flow model are adopted in order to examine the effect of periodic flow assumption on the performance predictions. Corresponding to the available experimental data, inlet mass flow rate, outlet static pressure and rotation of impeller are taken as 0.02m(3)s(-1), 450 kPa and 2950 rpm, respectively for the water fluid. No slip boundary condition is exposed to all solid of surface in the flow volume. The continuity and Navier-Stokes equations with the k-epsilon turbulence model and the standard wall functions are used. During the study, numerical analyses are conducted for the blade exit angle values of 18 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees. In consequence of the performed analyses, it is determined that hydraulic efficiency of the pump impeller value is changed between 81.0-84.6%. The most convenient blade exit angle that yields 84.6% hydraulic efficiency at is 18 degrees. The obtained results show that the blade exit angle range has an impact on the centrifugal pump performance describing the pump head and the hydraulic efficiency.Öğe Numerical investigation of flow structures around a sphere(TAYLOR & FRANCIS LTD, 2011) Hassanzadeh, Rahim; Sahin, Besir; Ozgoren, MuammerA numerical investigation of flow around a sphere is performed and compared with previous studies. Here, a second-order accurate, finite volume method is used in order to predict the instantaneous and time-averaged flow characteristics using large eddy simulation (LES) on the multi-block grid system. Namely, the objectives of this article are: (i) the presentation of flow structures in the wake region downstream of the sphere with a wide variety of flow properties such as the distribution of velocity vectors, patterns of streamlines, Reynolds stress correlations, root mean square of velocity components and other time-averaged flow data in order to reveal the vortical flow structures in detail and (ii) to demonstrate the abilities of computational methods in simulation of vortical flow data. Finally, it has been concluded that there are good agreements between the experimental results and numerical predictions.Öğe Performance of a solar ejector cooling-system in the southern region of Turkey(ELSEVIER SCI LTD, 2007) Ersoy, H. Kursad; Yalcin, Sakir; Yapici, Rafet; Ozgoren, MuammerPerformance variations of a solar-powered ejector cooling-system (SECS) using an evacuated-tube collector are presented for Antalya, Aydin, Konya and Urfa cities located in the southern region of Turkey by means of hourly and monthly average ambient temperature and solar radiation meteorological data. A SECS, based on a constant-area ejector flow model and using R-123, was considered. The cooling season and period were taken into account for the 6 months (May-October) and the hours 8:00-17:00, respectively. It was found that the evacuated-tube collector efficiency depending upon the ambient temperature and solar radiation within the day was remarkably varied. However, for all the cities, the cooling capacities of the SECS were very similar. When generator, condenser, and evaporator temperatures were taken, namely, 85 degrees C, 30 degrees C and 12 degrees C, the maximum 2 overall coefficient of performance and the cooling capacity were obtained as 0.197 and 178.26 W/m(2) respectively, at 12:00 in August for Aydin. The evacuated-tube collector area per ton cooling was found to be around 21 m(2) at. noontime in August for all the cities. Furthermore, at the off-design conditions, a performance map of the system was derived and discussed. It was determined that the SECS could be used for office-cooling purposes during the hours (8:00-15:00) in the southern region of Turkey. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Prediction of Hourly Solar Radiation in Six Provinces in Turkey by Artificial Neural Networks(ASCE-AMER SOC CIVIL ENGINEERS, 2012) Solmaz, Ozgur; Ozgoren, MuammerThe purpose of this study is to apply the method of artificial neural networks (ANNs) to predict the hourly solar radiation of six selected provinces in Turkey. Six neurons-receiving input signals of latitude, longitude, altitude, day of the year, hour of the day, and mean hourly atmospheric air temperature-were used in the input layer of the network. One neuron producing a corresponding output signal of hourly solar radiation was utilized in the output layer of the network. Two different models have been analyzed in the ANNs for training and testing. The results obtained from both models were compared by using different neurons, mean squared error (MSE), coefficient of determination (R-2), and mean absolute error (MAE). According to the results, the MSE value of training data in Model II was better than Model I. DOI: 10.1061/(ASCE)EY.1943-7897.0000080. (C) 2012 American Society of Civil Engineers.Öğe PREDICTION OF HOURLY SOLAR RADIATION USING AN ARTIFICIAL NEURAL NETWORK(BRNO UNIV TECHNOLOGY VUT PRESS, 2011) Solmaz, Ozgur; Ozgoren, MuammerThe aim of the presented study is to apply artificial neural networks (ANNs) method for prediction hourly solar radiation of the selected six provinces of Turkey. Six neurons which receive input signals of latitude, longitude, altitude, day of the year, hour of the day and hourly mean atmospheric air temperature were used in the input layer of the network. One neuron producing corresponding output signal of the hourly solar radiation was utilized in the output layer of the network. The model for training and testing in the formed ANNs was analyzed. Neuron numbers in the hidden layer (from 6 to 30 neurons step by step) and epoch numbers for 100 epochs were tested for different values. The obtained results for this model was compared by using different neurons, mean squared error (MSE), coefficient of determination (R-2), mean absolute error (MAE). The best results for the training were obtained as 25 neurons in terms of minimum MSE value of 0.000607. The R-2 values of the ANN for training and testing data of the 25 neurons are determined as 0.9879 and 0.9891 while the MAE values of which are 18.33 W/m(2) and 18.94 W/m(2), respectively.Öğe QUANTITATIVE FLOW CHARACTERISTICS FOR SIDE-BY-SIDE SQUARE CYLINDERS VIA PIV(E D P SCIENCES, 2012) Ozgoren, Muammer; Dogan, SercanIn this study, instantaneous and time-averaged flow structures downstream of the sharp-edged single and two and three side-by-side square cylinders (SCs) immersed in a uniform open channel water flow were studied by a technique of particle image velocimetry (PIV). Experimental results of wake flow structures were presented for gap ratios (G/D) in the range of 1.0 <= G/D <= 3.0 for Reynolds number values of 1050, 2450 and 3400. Flow structures depending on the square cylinder (SC) configurations and Reynolds number were discussed. It has been found that the development of the vortex shedding as well as the flow structure were substantially altered for side-by-side SCs comparing to the single SC. Asymmetrical and biased wake structures were observed because of the jet-like flow between the SCs for two SCs cases for the gap ratio less than 2.0. Depending on the gap spacing between the SCs, the interaction results of time-averaged vorticity, velocity vector field, Reynolds stress correlations < u'v'/U-infinity(2) > and streamline patterns in the wake region form a distinguished flow structure. Strouhal numbers for the single square cylinder for 1050 <= Re <= 3400 are found in the range of 0.12-0.13. The present results have supported the previous works by providing detailed quantitative experimental information with PIV in the wake region of the SC and might be helpful for validation of numerical studies and designers.
