Experimental investigation of flow characteristics of corrugated channel flow us ing PIV

The aim of the study is to determine the flow characteristics of corrugated duct. The whole study has been conducted for Reynolds numbers, Re=4000 and 6000. The corrugated duct geometry was designed for aspect ratios, s/H=0.3 and phase shift angle, ?=180°. Variations in flow characteristics of corrugated duct were investigated using the Particle Image velocimetry (PIV) technique. Time-averaged velocity distributions, patterns of streamline and corresponding turbulent statistics were determined. Augmentation of the Reynolds number leads to an increase in velocity due to the sharp corner edges of cavity. Dimensionless turbulent kinetic energy, contours indicate that the magnitude of turbulent kinetic energy, increases as a result of sharp corner edges of the cavities. High rate of momentum transfer is expected due to an increase of turbulence intensity

Investigation of flow characteristics and heat transfer enhancement of corrugated duct geometries

The objective of this study was to determine the flow characteristics and thermal efficiency in various ducts geometries numerically and experimentally. The whole studies were conducted for Reynolds numbers in the range of 3 × 103 ? Re ? 6 × 103. Firstly, effects of the aspect ratio, S/H on flow structures and heat transfer enhancement were aimed to be examined. Therefore, the corrugated duct geometries were designed for three different aspect ratios such as S/H = 0.1, 0.2, 0.3. Thermal efficiency of these geometries were examined numerically in order to optimize the aspect ratio, S/H. By increasing the corrugation height, the rate of turbulence intensity on the axis of corrugated channel increases as expected. Heat transfer rate increases with the rise of the aspect ratio, S/H and shows a maximum value at S/H = 0.3 that corresponds to the highest aspect ratio. The highest friction factor, f occurs in the corrugated channel with aspect ratio of S/H = 0.3 and it is followed by S/H = 0.2, and 0.1, respectively. Afterwards, experimental studies were conducted in order to identify hydrodynamic structures and verify findings of numerical solution using the Particle Image Velocimetry (PIV) technique. Velocity distributions, patterns of streamline and corresponding turbulent statistics were determined experimentally and numerically in order to reveal hydrodynamics characteristics and thermal performance of the corrugated channel flow. © 2017 Elsevier Lt

Covid-19 transmission risk minimization at public transportation stops using differential evolution algorithm

2-s2.0-85104339150Public transportation vehicles, with their confined spaces and limited ventilation, are considered among the primary factors in the spread of COVID-19. As a measure to slow the spread of the virus during the pandemic, governments have applied passenger capacity restrictions to ensure physical distancing. On the other hand, the increase in the risk of disease transmission associated with passengers waiting together at stops is omitted. In this study, we consider the risk of disease transmission as a travel cost and formulate a risk minimization problem as a transit network frequency setting problem. We develop a bi-level optimization model minimizing the total infection risk occurring at stops, namely, the cumulative disease transmission risk cost. The Differential Evolution algorithm is employed to cope with the NP-hard bi-level transportation network design problem. We propose a novel objective function for the upper-level model, considering the infection risk cost based on passenger traffic at public transportation stops. A congested user-equilibrium transit assignment model is utilized to determine passenger movement. The proposed model is applied to a small-size hypothetical network, and a mid-size test network. Experimental studies provide evidence that the model can produce optimal solutions. Optimization results show significant improvements in the reduction of disease transmission risk compared to the optimizations depending on the traditional practice of transportation network planning based on user and operator costs. The proposed model provides risk cost reductions of 51% and 22% compared to the optimal solutions based on user cost minimization in the hypothetical network and Mandl’s network, respectively. © 2021, TU Delft. All rights reserved

The effect of manganese on the microstructure and mechanical properties of leaded-tin bronze

In this work, the effect of manganese (Mn) on microstructure and mechanical properties of leaded-tin bronze was studied by using scanning electron microscopy and energy dispersive spectroscopy techniques, and tensile, fatigue and adhesive wear tests. It was observed that Mn decreased the wear resistance at the beginning stage of wear and markedly increased the fatigue life by preventing the formation of brittle and fragile (Zn, Cu)S phase, but it did not affect importantly the yield point, tensile strength, elongation and hardness. It was concluded that leaded-tin bronzes containing Mn can be preferred in manufacturing of machine elements in which fatigue is important. © 2001 Elsevier Science B.V

Utility of MARS algorithm for describing non-genetic factors affecting pasture revenue of Morkaraman breed and Romanov × Morkaraman F1 crossbred sheep under semi intensive conditions

This study was conducted on indigenous Morkaraman breed and Romanov × Morkaraman F1 Crossbreed sheep reared under semi-intensive conditions in order to determine the influence of dam age, genotype, birth weight, year, sex and birth type at lambing, weaning weight, weaning age, grazing period and weight at the end of the grazing period on pasture revenue, which is defined as the obtained revenue per lamb from weaning period to the end of the grazing period. Multivariate adaptive regression splines (MARS) data mining algorithms in addition to least squares method were scrutinized comparatively in the prediction of weight at the end of grazing period. The best statistical approach was selected based on goodness of fit criteria viz. determination coefficient (R 2 ), adjusted coefficient of determination (R 2 ADJ ), and Pearson correlation coefficient between the actual and the predicted values in the response trait handled. The greatest importance order was obtained for age at the end of grazing period (100%), followed by weight at the end of grazing period, weaning age, birth weight and grazing period. To obtain the pasture revenue, weight at the end of grazing period was required to be heavier than 26.2 kg, and age at the end of the grazing period was needed to be longer than 173 days. Average weaning weight of the lambs (15.7 kg) contributed the pasture revenue of 106.08 TL. When the weaning weights increased from 17.0 to 21.5 kg, the pasture revenue reduced from 79.56 to 7.34 TL. As a result, MARS algorithm may be a good approach to predict pasture revenue and to capture ideal cut-off values of significant factors affecting the revenue for increasing profitability of lamb meat production in the sheep. Copyright 2019 Zoological Society of Pakistan

Estimation of honey production in beekeeping enterprises from eastern part of Turkey through some data mining algorithms

The aim of this study was to develop a honey production model for 180 beekeeping enterprises at Agri, Kars and Erzurum provinces of Turkey and to identify factors affecting honey production through CART, CHAID and MARS data mining algorithms, which are more flexible compared to classical approaches. Several potential predictors in the survey were age of enterprise, province of enterprise (Agri, Kars and Erzurum), educational level, membership status of enterprise to an association of beekeepers (member and nonmember), other activities except for beekeeping (yes and no), number of full beehives, bee race (Caucasian, Carniolan, Italian and Crossbred), and frequency of changing queen bee. MARS outperformed multiple linear regression, and CART in honey yield per hive. No solution for CHAID was generated. In CART algorithm, the highest honey yield per hive (51.250 kg) was obtained from the 33.5 or younger enterprises that performed only beekeeping activity. The four most influential predictors in the MARS were age of enterprise (100%), number of full beehives (100%), other races (97%), and other works except for beekeeping (90%). The best performance order was MARS (r=0.920) > CART (r=0.619) > multiple linear regression (r=0.286), which indicated that MARS outperformed other approaches. MARS reflected that the main and interaction effects of socioeconomic (age of enterprise, province of enterprise, educational level, membership status, other works except for beekeeping and number of full beehives), biological predictors (bee race and frequency of changing queen bee) affected honey yield per hive. As a result, it is recommended that the effect of socioeconomic and biological predictors on the yield should be assessed jointly for further studies. © 2018 Zoological Society of Pakista

PIV measurement downstream of perforated cylinder in deep water

The flow structure of perforated circular cylinders was thoroughly scrutinized by using the technique of high-image-density Particle Image Velocimetry (PIV). The perforated circular cylinder diameter (D=100 mm), was kept constant during the experimental investigation and corresponding Reynolds number was Re=10000 based on the cylinder diameter. Turbulent statistics e.g., planar turbulent kinetic energy, stream-wise Reynolds normal stress, transverse Reynolds normal stress and Reynolds shear stress were computed in the wake region in order to reveal the differences among various porosities in the range of 0.25?ß?0.80. It would be noted that by increasing porosity, ß the flow fluctuations are substantially reduced in the wake region according to the PIV results. As a result, the prevention of Karman Vortex Street was accomplished by the use of perforated cylinders because of elongated and fragmented shear layers and reduced magnitudes of vortices. © 2018 Elsevier Masson SASNational Council for Scientific Research: 109R001The authors greatly acknowledge the contribution of the Scientific and Technological Research Council of Turkey to the funding of this research under contract no. 109R001

Vortex street suppression of a circular cylinder using perforated semi-circular fairing in shallow water

In this study, the effect of perforated fairing on vortex street suppression of a circular cylinder was investigated experimentally in shallow water. In order to investigate the effect of arc angle, ? and porosity, ß which are the main parameters of the study, three different arc angles (? = 120°, 150° and 180°) and six different porosities (ß = 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were examined. Perforated fairing was concentrically located with respect to the circular cylinder along its downstream direction. Turbulent statistics (turbulent kinetic energy, TKE and Reynolds shear stress, ) in the wake region were obtained by employing particle image velocimetry (PIV) technique at a Reynolds number of ReD = 5 × 103 based on the circular cylinder diameter, D. The results depicted that the flow structure downstream of bare cylinder was significantly affected by the presence of perforated fairing for the porosity, ß values, in the range of ß = 0.3–0.6. It is found that the wake region of the cylinder was elongated substantially along the main flow direction and the vortex shedding frequency, was reduced substantially. Moreover, opposing shear layers lost their strength considerably compared with the bare cylinder case. The peak magnitude of Reynolds shear stress, was reduced up to 75% for the arc angle of ? = 180° and the location of peak magnitude of Reynolds shear stress, moved further downstream regions for all cases. Compared to the bare cylinder case, the most effective flow control was obtained for the case having ß = 0.6 porosity and ? = 180° arc angle. © 2016109R001This study was supported by the funding of the Scientific and Technological Research Council of Turkey under contract no. 109R001