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This work presents a thermodynamic evaluation of an operating geothermal ORC power plant. The model is realized by using measured data of AFJET geothermal power plant which has 3MWe net power output capacity. Thermodynamic assessment of the system is conducted to see the energy and exergy efficiencies of each component, and the whole plant. Additionally, a parametric study is conducted to understand the effects of various operating conditions on the system performance. Different from previous studies, daily and annual net power output profile of the plant was investigated with considering ambient temperature fluctuations. Results revealed that net power output can drop as significant as 36% from winter to summer months. Also, between nighttime to daytime, the net power expectation may decrease by 5%. The exergy destruction rate of re-injection process constitutes the most significant part (38.1%) of the total exergy destruction of the plant. The conversion and exergy efficiencies of the system are calculated as 11.24% and 39.03%, respectively. Also, to enhance the performance of the plant, an internal heat recovery system is recommended. The analyses show that the implementation of an internal heat recovery system improves the energy and exergy efficiencies of the plant by 15%.

Gears are one of the most important power transmission elements in every area of the industry. Because of its importance, the gear design must be carefully performed. Unfortunately, due to the changing of the boundary conditions, gears are exposed to failures such as cracks, pitting, tooth missing etc. during the operation. Thus the gear diagnostic and monitoring become a very critical phenomenon for the gearboxes. A dynamic transmission error (DTE) based numerical fault detection model is proposed. Firstly, numerical finite element model is created to calculate single tooth stiffness with different crack levels. Furthermore, the model is used for the asymmetric gear profile which has a great importance nowadays for different areas. After that, the time-varying mesh stiffness is calculated by using single tooth stiffness with different crack levels for both symmetric and asymmetric types of the gears. To understand the effects of the gear cracks along the tooth thickness on dynamic transmission error of the gear system and to detect the gear crack faults for symmetric and asymmetric gear profiles, a four-degree of freedom dynamic model is created. The results show that with the increment of the crack level, the mesh stiffness of the gears is decreased.

In this study, some well-known experimental studies related to forced, natural, and mixed convections were used for validation of k-epsilon and k-omega turbulence models. For this purpose ANSYS-Fluent 16.0 is used. International Energy Agency IEA Annex20 room, a tall differentially heated rectangular cavity, and a mixed convective air flow within a square chamber with a heated bottom wall were considered for forced, natural, and mixed convection respectively. Standard, RNG and Realizable models of k-epsilon group, and Standard, SST and BSL models of k-omega group with enhanced wall treatment for near wall modeling were tested by comparing the velocity and temperature distributions with available measurement values of employed geometries. In total, the results of Standard and RNG k-epsilon models are in good agreement with experimental measurements. Although the performance of k-omega group models is well in natural convection, some results of these models do not agree well with test data in forced and mixed convection cases.

Continuously variable transmissions (CVT) have been widely used in many different areas such as automotive, robotics, manufacturing and aerospace industry. In CVT drives, a properly designed control strategy is needed to ensure the precise control of the speed ratio, and a deep knowledge of the steady-state and transient behavior of the drive is necessary to this purpose. In the framework of belt and chain CVT drives, model-based approaches developed for this purpose are mainly of two types: continuous models and multibody models. Continuous models are much less costly from a computation point of view, while multibody models are usually believed to be more accurate. The aim of this paper is twofold: first the CMM continuum model [Carbone G., Mangialardi L., Mantriota G., ASME Journal of Mechanical Design, 127, 103-113 (2005)] is compared with a multibody model of the chain-CVT variator. Secondly, the CMM model is proposed for a fast and enhanced characterization of the shifting dynamics of chain CVT. The analysis shows that, except for dynamical effects due to the intermittent contact of the chain pins with the pulleys and caused by the polygonal action of the chain, the CMM and multibody models provide very similar results. Moreover, this study shows, by exploiting the CMM model, that the overall dynamics of the CVT can be described by a relatively simple first order nonlinear differential equation, which can be very easily implemented for CVT real-time control applications. The accuracy of such a simplified approach is then tested against some preliminary shifting experiments under torque load conditions. Results show a very good agreement between theoretical predictions and experimental outcomes, thus making this simplified approach a promising tool to develop advanced real-time control of CVT transmissions for automotive applications. (C) 2016 Elsevier Ltd. All rights reserved.

We present a systematic numerical study on temperature dependent fracture mode change in small punch tests. Following Needleman and Tvergaard (2000), we model the material as thermo-inelastic, where the ductile fracture mode, by void nucleation, growth and coalescence is accounted for by Gurson׳s porous metal plasticity (Gurson, 1977). The brittle fracture mode by cleavage is accounted for by Ritchie–Knott–Rice׳s deterministic maximum principal stress criterion (Ritchie et al., 1973). The well-known problem of mesh dependence associated with softening material behavior is remedied by using an integral type nonlocal formulation similar to that presented in Tvergaard and Needleman (1995). Two length scales are incorporated into the constitutive relations: the ductile fracture length scale is based on the average inclusion distance and associated with the nonlocal evolution equation for the porosity. The brittle fracture length scale is based on the average grain size and associated with the material region at which the maximum principal stress is averaged out. The material model is used to simulate small punch tests at View the MathML source−196°C, View the MathML source−158°C and View the MathML source25°C of notched and unnotched specimens of P91 steel representative for small- and large-scale yielding conditions, respectively. The simulated fracture modes and patterns show a very good agreement with experiments: for View the MathML source−196°C brittle fracture propagating normal to the maximum (tensile) principal stress prevails. For View the MathML source25°C ductile fracture is governed by shear localization with voidage. The simulations also show that the deformation energy is considerably higher for the upper shelf tests compared to the lower shelf tests.

This study presents the application of seven recent meta-heuristic optimization algorithms to automate design of disk cam mechanism with translating roller follower regarding four follower motion laws. The algorithms are: salp swarm algorithm (SSA), moth–flame optimization (MFO), ant lion optimizer (ALO), multi verse optimizer (MVO), grey wolf optimizer (GWO), evaporation rate water cycle algorithm (ER-WCA), and mine blast algorithm (MBA). The optimum cam design problem is formulated with three objectives including the minimum congestion, maximum performance, and maximum strength resistance of the cam. Moreover, the effect of selecting follower motion law on the optimal design of mechanism is investigated. The computational results clearly indicate that the utilized algorithms are very competitive in structural design optimization, especially MBA, ER-WCA, MFO and GWO techniques. Among the four follower motion laws, the polynomial 3-4-5 degree is the best one.

The study was conducted to investigate the microstructure and mechanical properties of the hard zone in friction stir welded X80 pipeline steel at different heat inputs. Microstructural analysis of the welds was carried out using optical microscopy, transmission electron microscopy, and microhardness. Heat input during friction stir welding process had a significant influence on the microstructure and mechanical properties in the hard zone along the advancing side of the weld nugget. Based on the results, the linear relationships between heat input and post-weld microstructures and mechanical properties in the hard zone of friction stir welded X80 steels were established. It can be concluded that with decrease in heat input the bainitic structure in the hard zone becomes finer and so hard zone strength increases. (C) 2013 Elsevier B.V. All rights reserved.

Small Punch fracture tests were carried out in order to determine low temperature mechanical behaviour of a P91 steel weldment: weld metal, base metal, Heat Affected Zone-Fine Grained and Heat Affected Zone-Coarse Grained. The Heat Affected Zone-Fine Grained showed superior tensile properties in terms of displacement at fracture (ductility) and strength (maximum force) compared to the other zones, which became more pronounced at lower temperatures, whilst the weld metal exhibited inferior behaviour. Ductile Brittle Transition Temperatures were evaluated from Small Punch results for all zones and the results of base metal and weld metal were correlated with the transition temperatures obtained from Charpy V notch tests according to the CEN Code of Practice for Small Punch testing. Heat Affected Zone-Fine Grained with its finest structure exhibited the lowest transition temperature and the weld metal the highest. Heat Affected Zone-Coarse Grained and base metal were found to have quite similar transition temperature values. (C) 2013 Elsevier Ltd. All rights reserved.

This paper presents the design and performance characteristics of a new type cyclone separator. The design of this cyclone is based on the idea of improving cyclone efficiency by increasing the vortex length. This cyclone differs from a classical cyclone with the separation space. Instead of conical part, the separation space of this cyclone consists of an outer cylinder and a vortex limiter. A model of this cyclone has been manufactured and tested. Collection efficiency and pressure drop of this cyclone were measured under different operational conditions. Experimental results were compared with the conventional cyclones. The effects of the position of the vortex limiter on the cyclone performance were also investigated. (C) 2013 Elsevier Ltd. All rights reserved.

In this study, a four-stroke carburettor spark-ignition (SI) engine was run using a specially designed, electronically controlled gas-phase manifold liquefied petroleum gas (LPG) injection system in a set of experiments conducted to compare the performance of different fuels and mixing systems. Experiments were carried out at 2000–4000 rpm and fixed throttle positions of 25% and 50% of full opening to determine performance parameters. During the tests, carried out in a test bed with a specially designed, electronically controlled LPG injection unit, the excess air coefficient was maintained within the range of 0.95–1.05 because the best emissions results are generally obtained in this range. The results obtained with LPG injection were compared with the results obtained for gasoline and LPG carburetion. The test results showed that the LPG gas injection system developed in this study can help to achieve higher engine power outputs, lower specific fuel consumption and lower exhaust emissions.

This study is devoted to the natural vortex length which is one of the most important parameters for the performance of a reversed flow cyclone separator. A mathematical model was developed to estimate the natural vortex length and was applied to a newly designed cyclone which has a cylindrical body with sudden enlargement instead of a conical part. Special attention was given to the effects of inlet gas velocity, diameter and insertion length of the vortex finder and length of the frictional surface. A number of tests were also performed and the experimental data were compared with the model results. Experimental and model results show that, compared to the influence of the other parameters, the height of the frictional surface and inlet velocity affect the natural vortex length considerably. It was also observed that the vortex length increases up to a certain point with increasing the diameter of the vortex finder and then decreases after that. The results also showed that the present model is more successful in predicting the vortex length than the other models reported in the literature. (C) 2012 Elsevier B.V. All rights reserved.

An experimental failure analysis has been carried out to determine the effects of thermal condition and tightening torque on the failure load and failure behavior of single lap double serial fastener glass fiber/epoxy composite joints. 40, 50, 60, 70, and 80 degrees C temperatures were exposed to the specimens during tensile tests. It was seen that, the load-carrying capacity of the joint is decreased gradually by increasing temperature level. In proportion to the room temperature, the maximum decrease of failure loads occurs at 70 degrees C and 80 degrees C with the rate of nearly 55% and 70% respectively, because of the heat damage to the resin matrix. Besides thermal effects, 0 and 6 Nm tightening torques were applied to observe how clamping forces affect the joint strength. The results proved that, tightening torque is effective not only at room temperature, but also at elevated temperatures and contributes to the joint strength. (c) 2012 Elsevier Ltd. All rights reserved.

The effects of blockage on the hydrodynamic, thermal and mass transfer characteristics of a circular cylinder (CC) and their association with each other are investigated numerically, by considering the influence of blockage (beta=0.333-0.800) on the flow and heat transfer mechanisms in conjunction with moisture diffusivity (D=1 x 10(-8)-1 x 10(-5) m(2)/s) to show how much mass transfer behavior and phenomena are affected. As some comprehensive ANSYS-CFX runs are performed in the hydrodynamic and thermal fields around the CC, the moisture distributions within the CC are evaluated by Alternating Direction implicit method. It is determined that blockage causes thinner hydrodynamic and thermal boundary layers, rises the frictional and thermal activities, and shifts the separation locations (theta(s)) downstream to theta(s)=50.20 degrees, 41.98 degrees and 37.30 degrees for beta=0.333, 0.571 and 0.800. In the complete blockage scenario set, stagnation point heat transfer values are evaluated to be above those of the back-face, signifying the superior heat transfer enhancing capability of the stagnation point momentum activity when compared with the impact of downstream vortex system. The influence of moisture diffusivity on the overall drying times is determined to advance with stronger blockage. As the back face mass transfer coefficients (h(m-bf)) rise with a high beta, the contrary is valid for front face values (h(m-ff)), with the interpreting ratios of (h) over bar (m-bf)/(h) over bar (m)=0.51 and 0.57 and (h) over bar (m-ff)/(h) over bar (m)=1.49 and 1.43 for beta=0.333 and 0.800.

This paper describes an innovative optimization approach that offers significant improvements in performance over existing methods to solve shape optimization problems. The new approach is based on two-stages which are (1) Taguchi's robust design approach to find appropriate interval levels of design parameters (2) Immune algorithm to generate optimal solutions using refined intervals from the previous stage. A benchmark test problem is first used to illustrate the effectiveness and efficiency of the approach. Finally, it is applied to the shape design optimization of a vehicle component to illustrate how the present approach can be applied for solving shape design optimization problems. The results show that the proposed approach not only can find optimal but also can obtain both better and more robust results than the existing algorithm reported recently in the literature.

This paper presents a new hybrid optimization approach based on immune algorithm and hill climbing local search algorithm. The put-pose of the present research is to develop a new optimization approach for solving design and manufacturing optimization problems. This research is the first application of immune algorithm to the optimization of machining parameters in the literature. In order to evaluate the proposed optimization approach, single objective test problem, multi-objective 1-beam and machine-tool optimization problems taken from the literature are solved. Finally, the hybrid approach is applied to a case study for milling operations to show its effectiveness in machining operations. The results of the hybrid approach for the case Study are compared with those of genetic algorithm, the feasible direction method and handbook recommendation.

The focus of this research is on a hybrid method combining immune algorithm with a hill climbing local search algorithm for solving complex real-world optimization problems. The objective is to contribute to the development of more efficient optimization approaches with the help of immune algorithm and hill climbing algorithm. The hybrid algorithm combines the exploration speed of immune algorithm with the powerful ability to avoid being trapped in local minimum of hill climbing. This hybridization results in a solution that leads to better parameter values. This research is the first application of immune algorithm to the optimization of machining parameters in turning and also shape design optimization problems in the literature. The results of single-objective benchmark problem, multi-objective disc-brake problem, an automobile shape design optimization problem taken from the literature and case studies for multi-pass turning operation have demonstrated the superiority of the proposed hybrid over the other techniques in terms of solution quality and convergence rates.

The work presented in this paper examines the effects of cutting parameters (cutting speed, feed rate and depth of cut) onto the surface roughness through the mathematical model developed by using the data gathered from a series of turning experiments performed. An additional investigation was carried out in order to evaluate the influence of two well-known coating layers onto the surface roughness. For this purpose, the experiments were repeated for two CNMG 120408 (with an ISO designation) carbide inserts having completely the same geometry and substrate but different coating layers, in a manner that identical cutting conditions would be ensured. The workpiece material machined was cold-work tool steel AISI P20. Of the two types of inserts employed; Insert 1 possesses a coating consisting of a TiCN underlayer, an intermediate layer of Al 2 O 3 and a TiN outlayer, all deposited by CVD; whilst Insert 2 is PVD coated with a thin TiAlN layer (3 ± 1 μm). The total average error of the model was determined to be 4.2% and 5.2% for Insert 1 and Insert 2, respectively; which proves the reliability of the equations established.

New gear designs are needed because of the increasing performance requirements, such as high load capacity, high endurance, low cost, long life, and high speed. In some applications, such as in wind turbines, the gears experience only uni-directional loading. In these instances, the geometry of the drive side does not have to be symmetric to the coast side. This allows for the designing of gears with asymmetric teeth. In previous studies related to bending stress and load capacity, high performance has been achieved for gears with asymmetric teeth. These gears provide flexibility to designers due to their non-standard design. If they are correctly designed, they can make important contributions to the improvement of designs in aerospace industry, automobile industry, and wind turbine industry. At high operation speeds, there is always a concern of dynamic loads and vibrations of equipment. Therefore, there is a need to fully understand the dynamic behavior of gears with asymmetric teeth. Thus, the primary objective of this paper is to use dynamic analysis to compare conventional spur gears with symmetric teeth and spur gears with asymmetric teeth. The secondary objective is to optimize the asymmetric tooth design in order to minimize dynamic loads. This study offers preliminary results to designers for understanding dynamic behavior of spur gears with asymmetric teeth. For this study, a dynamic model was developed, using MATLAB, and used for the prediction of the instantaneous dynamic loads of spur gears with symmetric and asymmetric teeth. Furthermore, a 2-D three-tooth model was developed for finite element analysis. Fast Fourier transform was used for the frequency analysis of the static transmission errors. It is shown that generally, the dynamic factor, for spur gears with asymmetric teeth, increases with increasing pressure angles on the drive side. For asymmetric teeth, increasing the addendum leads to a significant decrease in the dynamic factor. The static transmission error, at the center of the single tooth contact zone, decreases with increasing pressure angle. The first two harmonics slightly increase with increasing pressure angle. It is further shown that the amplitudes of harmonics of the static transmission errors are significantly reduced when asymmetric teeth with long addendum providing high gear contact ratio close to 2.0 are used.

In this study a combined computational model of a room with virtual thermal manikin with real dimensions and physiological shape was used to determine heat and mass transfer between human body and environment. Three dimensional fluid flow, temperature and moisture distribution, heat transfer (sensible and latent) between human body and ambient, radiation and convection heat transfer rates on human body surfaces, local and average convection coefficients and skin temperatures were calculated. The radiative heat transfer coefficient predicted for the whole-body was 4.6 W m(-2) K-1, closely matching the generally accepted whole-body value of 4.7 W m(-2) K-.(-1) Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.8 W m(-2) K-1. Results of calculations were in agreement with available experimental and theoretical data in literature. (C) 2008 Elsevier Ltd. All rights reserved.

In metal cutting, the problems need to be well analyzed in order to take precautions before any unexpected results are encountered. This process plays a significant role in achieving consistent quality and in controlling the overall cost of manufacturing. However, it is a difficult task that needs an expert who has a great deal of information and experience in metal cutting. In the present paper, a knowledge-based expert system (COROSolve) that investigates problems that are encountered in three main metal cutting areas: turning, milling and drilling is developed. A great deal of metal cutting operations such as external/internal turning with negative/positive inserts, aluminum turning, parting bars/tubes, grooving, profiling, recessing and threading operations in turning; face milling, square shoulder milling, end milling, multi-purpose milling and side and face milling operations in milling; and drilling operations that use solid drills or drills with indexable inserts in drilling are taken into consideration. COROSolve gives recommendations for the cutting data (i.e., cutting speed, depth of cut, and feed) and updates the problem, cause and remedy database, thus the number of problems that the system can handle is increased.

Heat treating the ductile cast iron produced austempered ductile iron (ADI), which has outstanding mechanical properties that can be varied over a wide range by varying the heat treatment parameters. In the present work a series of test were conducted and the effects of austempering temperature and times onto the material properties was investigated. The machinability of ADI was evaluated by comparing tool life, tool wear rate, cutting forces, and surface finish produced on a job as general criteria. Machinability tests were carried out following ISO 3685: 1993 (E) standard “Tool Life Testing with Single Point Turning Tools”. The cutting force data used in the analyses were gathered by a tool breakage detection system that detects the variations of the cutting forces measured by a three-dimensional force dynamometer. Six pairs of ductile iron specimens, austempered at 300, 350 and 400 °C for 1 and 2 h were tested. The cutting tools used in the tests were coated carbide inserts, ISO SNMG 120408 (K10), clamped on tool holders CSBNR 2525 M12. No cutting fluid was used during the turning operations. During the experiments cutting forces, flank wear and surface roughness values were measured throughout the tool life and the machining performance of ADI having different structures were compared.

In this paper, the coupled flexural–torsional free and forced vibrations of a beam with tip and/or in-span attachments are studied. First, a mathematical model is established, which consists of a beam with several tip attachments, i.e, a tip mass of non-negligible dimensions, a linear spring grounding the tip mass, and a torsional spring connected at the end of the beam. The modal functions of this model and the orthogonality condition among them are derived. For the purpose of verification the properties of the tip attachments are changed, and the numerical results obtained are compared with those given in the relevant literature. Effects of tip mass and distributed mass in-span on natural frequencies and modes are investigated for two cantilever beams with different cross sections. An application of the orthogonality condition in the case of a beam with tip mass is also presented for a forced vibration example.

In this work cutting FEA of cutting tools prior to fracture is investigated. Fracture is the catastrophic end of the cutting edge that should be avoided for the cutting tool in order to have a longer tool life. This paper presents finite element modelling of a cutting tool just before its fracture. The data used in FEA are gathered from a tool breakage system that detects the fracture according to the variations of the cutting forces measured by a three-dimensional force dynamometer. The workpiece material used in the experiments is cold work tool steel, AISI O1 (60 HRC) and the cutting tool material is uncoated tungsten carbide (DNMG 150608). In order to investigate the cutting tool conditions in longitudinal external turning operations prior to fracture, static and dynamic finite element analyses are conducted. After the static finite element analysis, the modal and harmonic response analyses are carried on and the dynamic behaviours of the cutting tool structure are investigated. All FE analyses were performed using a commercial finite element package ANSYS.

Tool life and condition monitoring systems can be used effectively in cutting processes. Since no exact and reliable mathematical models exist for the cutting process which are able to predict tool wear, tool breakage, cutting temperature and forces, the development of tool condition monitoring systems are highly requested by industry, especially in recent years. The purpose of this research is to develop a tool condition monitoring and a real-time tool life detection system in turning processes. The software and hardware generated for this research is based on the characteristic variations of the cutting forces. When a tool wears or breaks, cutting forces increase slightly right after the tool breakage and then decrease sharply. The change of cutting forces can itself be a good indicator to detect the tool failure. The experimental set-up developed in this research consists of a dynamometer, a pre-amplifier, an A/D converter, and a personal computer. The workpiece material is AISI 1050 steel and the tool material is coated and uncoated tungsten carbide (ISO P25). The type of insert that is used is DNMG 150608. No cutting fluid was used during the turning operations. The performance of the system has been tested experimentally for certain machining conditions and the experimental results showed that the system was being successful in tool breakage detection.

An experimental investigation of the performance of a commercially available vapor absorption refrigeration (VAR) system is described. The natural gas-fired VAR system uses aqua-ammonia solution with ammonia as the refrigerant and water as the absorbent and has a rated cooling capacity of 10 kW. The unit was extensively modified to allow fluid pressures and temperatures to be measured at strategic points in the system. The mass flow rates of refrigerant, weak solution, and strong solution were also measured. The system as supplied incorporates air-cooled condenser and absorber units. Water-cooled absorber and condenser units were fitted to extend the VAR unit's range of operating conditions by varying the cooling water inlet temperature and/or flow rates to these units. The response of the refrigeration system to variations in chilled water inlet temperature, chilled water level in the evaporator drum, chilled water flow rate, and variable heat input are presented. (C) 2003 Elsevier Ltd and IIR. All rights reserved.

The human thermal environment can be represented by the air temperature, radiant temperature, air velocity, humidity, clothing and activity. This has implications for health, comfort and performance. An understanding of human thermoregulatory processes facilitates the design and development of improved heating and cooling systems. This study presents a computational model of thermal interactions between a human and the interior environment. The model is based on the heat balance equation for human body with different types of clothing ensembles, combined with empirical equations defining the sweat rate and mean skin temperature. Simulation has been performed by the use of steady state conditions, and two different posture positions, namely sitting and standing, are considered in this study. Results are in good agreement with available experimental data. The parametric studies show that the methodology described can provide an effective means for simulating thermal comfort level.

With developing technology and the rapid increase in world population, the demand for energy is ever increasing. Conventional energy will not be enough to meet the continuously increasing need for energy in the future. In this case, renewable energy sources will become important. Solar energy is a very important energy source because of its advantages. Instead of a compressor system, which uses electricity, an absorption cooling system, using renewable energy and kinds of waste heat energy, may be used for cooling. In this study, a solar-powered, single stage, absorption cooling system, using a water–lithium bromide solution, is simulated. A modular computer program has been developed for the absorption system to simulate various cycle configurations and solar energy parameters for Antalya, Turkey. So, the effects of hot water inlet temperatures on the coefficient of performance (COP) and the surface area of the absorption cooling components are studied. In addition, reference temperatures which are the minimum allowable hot water inlet temperatures are determined and their effect on the fraction of the total load met by non–purchased energy (FNP) and the coefficient of performance are researched. Also, the effects of the collector type and storage tank mass are investigated in detail.

Flow and heat transfer characteristics in laminar flows were investigated with pressure gradients, streamwise distance Reynolds number and wall curvature. Measurements were carried out in a low speed wind tunnel with a dimensionless streamwise pressure gradient parameter of k x (= x u m du m dx ) between −4 and 1.0. Results were compared with analytical solutions and numerical predictions and a new empirical equation as a function of kx. It was found that Stanton numbers augmentation with Reynolds number became more pronounced than concave curvature. Favourable pressure gradients caused heat transfer to increase and adverse pressure gradients to decrease. The also results showed that the distribution of Stanton numbers with acceleration has similar trends with analytical solutions and numerical predictions. The proposed equation showed much better agreement with the measured Stanton numbers, in case of both adverse and favourable pressure gradients.

This paper describes a procedure to calculate the machining conditions, such as the cutting speed, feed rate and depth of cut for turning operations with minimum production cost or the maximum production rate as the objective function. The optimum number of machining passes and the depth of cut for each pass is obtained through the dynamic programming technique and optimum values of machining conditions for each pass are determined based on the objective function criteria by search method application to the feasible region. Production cost and production time values are determined for different workpiece and tool material for the same input data. In the optimization procedure, the objective functions are subject to constraints of maximum and minimum feed rates and speeds available, cutting power, tool life, deflection of work piece, axial pre-load and surface roughness. By graphical representation of the objective function and the constraints in the developed software, the effects of constraints on the objective function can be evaluated. The parameters that are assumed to be most effective in determining the optimum point can easily be changed and the revised graph can be inspected for possible improvements in the optimum value.

The purpose of this study is to investigate the unsteady periodic flow near the point of bifurcation in a branching pipe. For this purpose an experimental setup was constructed and a laser light sheet flow visualization technique was used. Experiments were carried out at low Reynolds numbers for branching angles of 30-degrees and 90-degrees. Flow separations and large recirculating regions occurred, especially at the beginning and end of periods of observation. The effects of both the variation of Reynolds number and the branching angle on the flow separation and recirculation are discussed