Full-coverage film cooling: 3-dimensional measurements of turbulence structure and prediction of recovery region hydrodynamics

Hydrodynamic measurements were made with a triaxial hot-wire in the full-coverage region and the recovery region following an array of injection holes inclined downstream, at 30 degrees to the surface. The data were taken under isothermal conditions at ambient temperature and pressure for two blowing ratios: M = 0.9 and M = 0.4. Profiles of the three main velocity components and the six Reynolds stresses were obtained at several spanwise positions at each of the five locations down the test plate. A one-equation model of turbulence (using turbulent kinetic energy with an algebraic mixing length) was used in a two-dimensional computer program to predict the mean velocity and turbulent kinetic energy profiles in the recovery region. A new real-time hotwire scheme was developed to make measurements in the three-dimensional turbulent boundary layer over the full-coverage surface

Modeling Sulfur Dioxide Capture in a Pulverized Coal Combustor

The formation and capture of sulfur dioxide in a pulverized coal combustor is steady, axisymmetric code

Recovery of wall-shear stress to equilibrium flow conditions after a rough-to-smooth step change in turbulent boundary layers

This paper examines the recovery of the wall-shear stress of a turbulent boundary layer that has undergone a sudden transition from a rough to a smooth surface. Early work of Antonia and Luxton (J. Fluid Mech., vol. 53, 1972, pp. 737–757) questioned the reliability of standard smooth-wall methods for measuring wall-shear stress in such conditions, and subsequent studies show significant disagreement depending on the approach used to determine the wall-shear stress downstream. Here we address this by utilising a collection of experimental databases at Reτ≈4100 that have access to both ‘direct’ and ‘indirect’ measures of the wall-shear stress to understand the recovery to equilibrium conditions of the new surface. Our results reveal that the viscous region ( z+≲4 ) recovers almost immediately to an equilibrium state with the new wall conditions; however, the buffer region and beyond takes several boundary layer thicknesses before recovering to equilibrium conditions, which is longer than previously thought. A unique direct numerical simulation database of a wall-bounded flow with a rough-to-smooth wall transition is employed to confirm these findings. In doing so, we present evidence that any estimate of the wall-shear stress from the mean velocity profile in the buffer region or further away from the wall tends to underestimate its magnitude in the near vicinity of the rough-to-smooth transition, and this is likely to be partly responsible for the large scatter of recovery lengths to equilibrium conditions reported in the literature. Our results also reveal that smaller energetic scales in the near-wall region recover to an equilibrium state associated with the new wall conditions within one boundary layer thickness downstream of the transition, while larger energetic scales exhibit an over-energised state for several boundary layer thicknesses downstream of the transition. Based on these observations, an alternative approach to estimating the wall-shear stress from the premultiplied energy spectrum is proposed

Secondary education teachers’ perception of workplace friendship and its relationship with job satisfaction ( sample of Aydin province )

Araştırmada ortaöğretim öğretmenlerinin iş yeri arkadaşlık algıları ile iş doyumları arasındaki ilişkinin ortaya çıkarılması amaçlanmıştır. Verilerin toplanmasında Kişisel Bilgi Formu, iş Yeri Arkadaşlık Ölçeği ve Minnesota İş Doyum Ölçeği kullanılmıştır. Verilerin analizinde betimsel istatistik teknikleri, parametrik ve parametrik olmayan testler kullanılmıştır. Araştırmanın sonucunda, ortaöğretim öğretmenlerinin en yüksek düzeyde “arkadaşlık fırsatı”, sonra “egemen olan arkadaşlık” algısına sahip oldukları, “genel arkadaşlık” algısının ise ortalamadan yüksek olduğu bulunmuştur. Kadın öğretmenlerin arkadaşlık fırsatı algısının, erkek öğretmenlerden; yine bekâr öğretmenlerin arkadaşlık fırsatı algısının, evli öğretmenlerden anlamlı biçimde daha yüksek olduğu bulunmuştur. Öğretmenlerin en çok içsel doyum sağladığı, bunu genel ve dışsal doyumun takip ettiği saptanmıştır. 35 yaş altı ile 46-50 yaş grubu içinde bulunan öğretmenlerin içsel, dışsal ve genel doyum düzeylerinin, diğer yaş gruplarındaki öğretmenlerden anlamlı şekilde yüksek olduğu ortaya çıkmıştır. 5 yıl ve altında kıdeme sahip olan öğretmenlerle, 11-15 yıl arası kıdeme sahip öğretmenlerin; içsel, dışsal ve genel doyum düzeylerinin, diğer kıdeme sahip olan öğretmenlerden anlamlı şekilde yüksek olduğu bulunmuştur. İş doyumu ile genel iş yeri arkadaşlık algısı ve arkadaşlık fırsatı boyutu arasında pozitif yönde orta düzeyde, egemen olan arkadaşlık ile de yine pozitif yönde düşük düzeyde ilişkiler bulunmuştur. Arkadaşlık fırsatı boyutunun iş doyumunu genel ve boyutlar bazında pozitif yönde yordadığı tespit edilmiştir.The purpose of this research was to find out secondary education teachers‟ perception of workplace friendship and its relationship with job satisfaction. Data was collected by means of Personal Information Form, Workplace Friendship Scale and Minnesota Job Satisfaction Scale. In data analysis, descriptive statistical tecniques, parametric and nonparametric tests were used. According to the findings of the research, secondary education teachers‟ perception of workplace friendship was at the highest level on friendship opportunity and followed by friendship prevalence. General perception of friendship was found relatively higher than the mean. Female teachers‟ level of perception of workplace friendship was found significantly higher than male teachers‟. Single teachers‟ perception of friendship opportunity was found significantly higher than married teachers. It was determined that, teachers‟ internal satisfaction was at the highest level and followed by general and external satisfaction. The teachers who are under the age of 35 and who are between the ages of 46 and 50 had significantly higher internal, external and general job satisfaction than the other groups. It was found that, teachers who have 5 years or less experience, between 11 and 15 years of experience had significantly higher internal, external and general job satisfaction than the other groups. It was found that, there was a pozitive medium level relationship between job satisfaction, perception of general workplace friendship and also friendship opportunity. Besides, there was a pozitive low level relationship between job satisfaction and friendship prevalence. In addition, friendship opportunity dimention pozitively predicted job satisfaction on the basis of both general and the dimentions

Faculty of Economics and Administrative Sciences. Activity-based costing method and a current application

Text in Turkish; Abstract: Turkish and EnglishIncludes bibliographical references (leaves: 62-65)x, 66 leavesYükselen rekabet ortamında firmalar, maliyetlerini giderek azaltma eğilimi içeresindedirler. Maliyetlerin azaltılması amacı doğrultusunda ise öncelikle, maliyetlerin doğru olarak tespiti önem taşımaktadır. Maliyetlerin azaltılabilmesi için ayrıca, kaynak verimliliğinin sağlanması da önem taşımaktadır. Günümüz ortamında teknoloji ve iletişimdeki hızlı gelişmeler, maliyet türlerinin oluşumunu da etkilemektedir. Böyle bir ortamda, geleneksel maliyetleme yöntemlerinin yeterli olamadığı anlaşılmıştır. Bu nedenle geliştirilen çeşitli yaklaşımlardan biri de faaliyet tabanlı maliyetlemedir. Tezde faaliyet tabanlı maliyetleme yöntemi geleneksel yöntemle karşılaştırmalı olarak incelenmiştir. Güncel bir uygulama örneğine dayalı olarak da sonuçlar irdelenmiş ve öneriler sunulmuştur.In a rising competitive environment, firms tend to reduce their costs gradually. In order to reduce the costs, firstly, it is important to determine the costs correctly. It is also important to ensure resource efficiency for the goal of reducing costs. In today's environment, rapid developments in technology and communication also affect the formation of cost types. In such an environment it has been understood that traditional costing methods are not sufficient. One of the various approaches developed for this reason is activity-based costing. The activity based costing method in the thesis is examined comparatively with the traditional method. Based on a current application example, the results are discussed and suggestions are presented

Near-Field Simulations of Film Cooling with a Modified DES Model

Modeling the heat transfer characteristics of highly turbulent flow in gas turbine film cooling is important for providing better insights and engineering solutions to the film cooling problem. This study proposes a modified detached eddy simulation (DES) model for better film cooling simulations. First, spatially varying anisotropic eddy viscosity is found from the results of the large eddy simulation (LES) of film cooling. Then the correlation for eddy viscosity anisotropy ratio has been established based on the LES results and is proposed as the modification approach for the DES model. The modified DES model has been tested for the near-field film cooling simulations under different blowing ratios. Detailed comparisons of the centerline and 2D film cooling effectiveness indicate that the modified DES model enhances the spanwise spreading of the temperature field. The DES model leads to deviations of 62.4%, 39.8%, and 33.5% from the experimental centerline effectiveness under blowing ratios of 0.5, 1.0, and 1.5, respectively, while the modified DES reduces the deviations to 51.5%, 26.7%, and 28.9%. The modified DES model provides a promising approach for film cooling numerical simulations. It embraces the advantage of LES in resolving detailed vortical structure dynamics with a moderate computational cost. It also significantly improves the original DES model on the spanwise counter rotating vortex pair (CRVP) spreading, mixing, and effectiveness prediction

THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS EFFECTS OF FREE STREAM TURBULENCE ON THE INSTANTANEOUS HEAT TRANSFER IN A WALL JET FLOW

ABSTRACT This is a preliminary study in order to understand how free stream turbulence increases the heat transfer. Effects of free stream turbulence on the instantaneous heat transfer were investigated in a wall jet flow. Heat transfer traces obtained by a hot film probe flush-mounted with the surface showed an intermittent structure with definite peaks at certain time intervals. Number of peaks per unit time increased with increasing turbulence intensity. A wall jet test rig was designed and built. The initial thickness and the velocity of the wall jet were 10 cm and 24.4 m/s respectively. The hot film probe which was flush with the surfaces was positioned at 10 cm intervals on the surface in the flow direction. The profiles of mean velocity and axial component of the Reynolds stress were measured with a horizontal hot wire probe. Space correlation coefficients for u' and q' were obtained in the vertical direction to the wall. This paper concentrates on the effects of turbulence level on the instantaneous heat transfer at the wall. It is speculated that intermittent structure of the heat transfer traces are related to burst phenomena and increase in heat transfer is due to increased ejections (bursts) at the wall with increasing turbulence levels. INTRODUCTION Free-stream turbulence (FST) is the turbulence in the approach stream. It is experienced in many applications. For example