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Copyright of Transactions of Nanjing University of Aeronautics & Astronautics is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Climate changes and their effect worldwide point toward high need of renewable energy resources exploitation and, consequently, adequate policies on regulation for efficient energy consumption. Wind has been used since ancient times for producing energy and this is why research on wind turbine design and performances has been carried on since. This article is aimed to present new mechanical system for variable pitch vertical axis four blades wind turbine. The pitch angle varies depending on wind flow direction due to cam and follower, linked to a four bar mechanism. [ABSTRACT FROM AUTHOR]

Turbo machines develop faults in the rotating blades during operation in undesirable conditions. Such faults in the rotating blades are fatigue cracks, mechanical looseness, imbalance, misalignment, etc. Therefore, it is crucial that the blade faults should be detected and diagnosed in order to minimize the severe damage of such machines. In this paper, vibration analysis of the rotating blades is conducted using an experimental laboratory setup in order to develop a methodology to detect faults in the rotating blades. The faults considered for the study include cracks and mechanical looseness for which dynamic responses are recorded using a laser vibrometer. Analysis has been carried out by comparing the frequency response function spectrums of the fault blade with those of the healthy blade related to the resonance frequency. The Internet of Things and wireless sensor networks are implemented to transmit the measured data to the cloud platform. A support vector machine algorithm is used for preparing the learning model in order to extract and classify the faults of the rotating blades. It can be clearly seen from the results that there is variation in the frequency response function spectrums of healthy and faulty conditions of the rotating blades. [ABSTRACT FROM AUTHOR]

The essence of the definition of "battle axe" has been investigated. It is determined, that it is an axe, intended for use as a cutting, chopping-stabbing, chopping-slicing and chopping-stabbing-cutting cold weapon, and consists of an iron (percussive part with a blade) and a hatchet (handle). The history of the development of battle axes - from stone to modern ones - has been studied. The material for making axes has been determined - stone, metal and other materials. For foot soldiers, a battle ax was often the main weapon, for horsemen - an auxiliary one. Battle axes were used mainly for close combat. Some types of axes were used for throwing. Axes were also widely used as ceremonial weapons. The battle ax has spread all over the world, different modifications of it have appeared in different regions. The reasons for the spread of the battle ax were the relative cheapness compared to the sword and the personal preferences of the owner. The purpose of the study was the formation of a forensic battle axes classification. The materials of the research were literary sources, scientific works and expert conclusions on the studied issues. On the basis of the conducted research, a forensic classification of battle axes is proposed. The main characteristics of battle axes include their type; method of action; application method; iron manufacturing technology; number of blades; blade shape; blade width; the presence of additional striking elements; iron material; the shape (cross-section) of the eyelet; the method of attaching the iron to the ax; ax length; ax shape; ax material; the way of holding (grasping) the ax; availability of additional accessories, tuning; the method of making an ax; time of manufacture; construction decoration. [ABSTRACT FROM AUTHOR]

As a destructive process, scouring exposes bridge foundations to failure and disastrous consequences. Control structures of various arrangements are capable to change and manage the adverse effects. The present work aims to probe the response of submerged vanes of a quasitriangular arrangement (of heights 0, 4, and 6 cm), eppi, and sills (of height 4.5 and 9 cm) on scour development. All tests were executed in a rectangular slope-less flume covered with sediments of D50=1.8 mm. Temporal and equilibrium scour depth were mapped for Froude numbers: 0.15, 0.2, 0.25, and 0.6. Results clarified the aggregate effect of the eppies on the scour depth due to section contraction. Submerged vanes and sill were set up to deteriorate sediment transport. Although the vane of height 4 cm had the most superior performance, but the sill installation of height 4.5 cm greatly increased vane's effect, so that a remarkable reduction of scour was occurred at the first pier foundation. [ABSTRACT FROM AUTHOR]

Cloud cavitation usually appears on impeller blades of hydraulic machinery. When unsteady cloud cavitation travels downstream to a high-pressure region and collapses, performance drops and cavitation erosion appears. It is important to develop effective methods to mitigate the undesirable effects. By million years of natural selection, bird feather has presented excellent flow performance. As typical characteristic structure of bird feather, a number of barbs are supported by a central hollow shaft. Under inspiration of bird feathers, we presented a method of passive cavitation control. This method of passive cavitation control uses biomimetic protuberant stripes (PSs) mounted on a NACA66 hydrofoil. The effects of various biomimetic PS arrangements on the cavitation pattern, pressure fluctuation, and hydrodynamic load are numerically studied. Then, the cavitation control mechanism of the biomimetic PS is analyzed in detail. We observe that the biomimetic PSs not only inhibit the shedding of large-scale cloud cavitation but also reduce the cavitation size. Moreover, analysis shows that turbulence velocity fluctuation may be mitigated and boundary layer thickness is reduced with biomimetic PSs, which enhances the flow intensity in the main flow direction. [ABSTRACT FROM AUTHOR]

Cavitation erosion is a fundamental concern in many fields of engineering, e.g. the flow separation zone in high speed flow and the blade area of hydraulic machinery. However, the influence of the physical characteristics of the environmental medium in these engineering facilities on cavitation erosion is still unclear. In this paper, we adopted underwater low-voltage discharge technology to generate cavitation bubbles, and studied the mesoscale causes of material erosion in solutions with different surface tensions. It is found that with the decrease of liquid surface tension, the radial velocity of cavitation bubbles decreases significantly during the shrinkage of the cavitation bubble and the minimum radius to which the cavitation bubble shrinks increases, the micro-jet generated by the cavitation bubble develops more slowly, and the impact strength of cavitation bubble collapses on the wall decreases. The findings reveal new physical mechanisms of the cavitation-induced material erosion in liquids with different surface tensions at the macroscopic level. These will provide significant guidance for cavitation prevention in various applications such as aeration cavitation-alleviation, hydraulic machinery, ultrasonic cleaning and the medical industry. [ABSTRACT FROM AUTHOR]

The crown-post roof appeared in England in the second half of the thirteenth century and persisted until the early sixteenth century in the south-east of England. Rafter holes are found in these roofs near to the feet of the rafters on their lower faces. They are blind holes typically 75 mm to 100 mm deep by about 25 mm in diameter. Various theories have been put forward over the years to explain their function. This paper reviews the evidence found on the rafters and integrates it into a revision of one of the earlier theories which suggested that rafter holes formed part of a jig or templet. This jig was used to ensure that the collars were at the correct height relative to the crown plate (or collar purlin). These ideas have been applied in the prefabrication of a new crown-post roof. Evidence is also presented showing how the practice of using jigs to help prefabricate rafter cross-frames may also have been applied to some other roof types such as scissor-braced and side-purlin roofs, in south-east England. [ABSTRACT FROM AUTHOR]

Four Cornish buildings with base-cruck trusses are described, part of a distinctive group that share the feature of having the blades passing the tiebeams to clasp the arcade plates. They have been dated, using a combination of ring-width and stable-isotope dendrochronology, to between the late thirteenth and late fourteenth centuries, making them the earliest known secular buildings in Cornwall. The paper discusses how these trusses relate to the development of the base-cruck form nationally and sets the buildings into their broader historical context. [ABSTRACT FROM AUTHOR]

The main problem encountered in natural stone cutting has been how to ensure clean and efficient production conditions that minimize saw blade wear and energy consumption, while maximizing production/cutting quantities, involving the finding of a balance between cutting costs and sales price. This study analyzes cutting data from more than 400 cutting cycles in an industrial granite-cutting process, obtained at different feed rates and cutting depths using a two-column block cutter with 23 x 1200 mm saw blades. Of the cutting parameters, feed rate and cutting depth values were varied, and power consumption values were measured using a mobile power analyzer, after which recommendations have been made for efficient cutting. Cutting tests have been conducted under conditions in which the feed rates were 8, 10, 15 and 20 m/min, and the depth of cuts were 3, 4, 6, 8 and 12 mm. The changes in energy consumption values at different depth of cut values and feed rateshave been evaluated under actual production conditions. According to the results of the study, changes in power consumption under shallow and deep cutting conditions were analyzed in detail, and an empirical model is proposed to explain the relationship between power consumption, production speed and saw blade costs. [ABSTRACT FROM AUTHOR]

The paper discusses the performance of the pump in relation to the impeller. The impeller section is determined by the number and angle of the blades. Therefore, the purpose of this study was to analyze the role of the number and angle of impeller blades on the performance (discharge and discharge pressure) of centrifugal pumps based on experiments and simulations. The method used is experiment and simulation. Using a centrifugal pump type GWP 20/4 SW, Maximum Output: 6.5 HP/3500 rpm, Inlet/Outlet: 2 Inch, Dimensions: 475x375x370 mm. Experiments and simulations by varying the number of blades 2, 4, and 6 with a blade tilt angle of 130°, 150°, and 160°. For flow simulation using solid works program. The results show that pump performance is related to discharge pressure, impeller with 2-blades and an angle of 130° the pressure increases 0.45-2.45 bar, for 150° increases 0.14-2.96 bar, and 160° increases 0.29-3.07 bars. For a 4-blade impeller and an angle of 130°, the pressure increases by 0.48-3.12 bar, for 150° it increases by 0.39-3.39 bar, and for 160° it increases by 0.36-3.48 bar. While the impeller for 6-blades with an angle of 130° the pressure increases from 0.6 bar to 3.72 bar, for 150° increases from 1.36 to 4.34 bar, and 160° increases by 0.36-4.74 bar. While it related pump performance to flow rate, increasing the number of blades causes a decrease in flow rate. The highest flow rate is in a 2-blade impeller with a blade angle of 130° is 404.91 l/s. The lowest flow rate is on a 6-blade impeller with an angle of 160° is 279.66 l/s. [ABSTRACT FROM AUTHOR]

The paper presents a detailed analysis of particle image velocimetry (PIV) measurements performed in a turbine cascade representative of highly accelerated low-pressure turbine (LPT) blades. Two cameras have been simultaneously used to observe a great portion of the suction side boundary layer with the highest possible spatial resolution, thus allowing us to solve the interaction process between impinging upstream wakes and the blade boundary layer. Four unsteady inflow conditions, characterized by different incoming wake reduced frequencies and flow coefficients, have been examined at fixed Reynolds number. The highly resolved flow fields have been processed to explore reduced frequency and flow coefficient effects on the boundary layer unsteady transition process and, consequently, on loss production. For a deep physical insight on the mechanisms responsible for loss generation, proper orthogonal decomposition (POD) has been applied at different phases of the wake passing period. This has provided the dominant structures affecting the cascade aerodynamics during the wake period. Moreover, the examination of POD modes has allowed us to show the effects induced by the parameter variation on the turbulent kinetic energy production and thus to the unsteady loss production mechanisms. [ABSTRACT FROM AUTHOR]

Aeroelastic instabilities such as flutter have a crucial role in limiting the operating range and reliability of turbomachinery. This paper offers an alternative approach to aeroelastic analysis, where the sensitivity of aerodynamic damping with respect to main flow and structural parameters is quantified through a surrogate-model-based investigation. The parameters are chosen based on previous studies and are represented by a uniform distribution within applicable intervals. The surrogate model is an artificial neural network, trained and tested to achieve an error within 1% of the test data. The quantity of interest is aerodynamic damping and the datasets are obtained from a linearised aeroelastic solver. The sensitivity of aerodynamic damping with respect to the input variables is obtained by calculating normalised gradients from the surrogate model at specific operating conditions. The results show a quantitative comparison of sensitivity across the different input parameters. The outcome of the sensitivity analysis is then used to decide the most appropriate action to take in order to induce stability in unstable operating conditions. The work is a preliminary study, carried out on a simplified two dimensional compressor cascade and it is aimed at proving the validity of a data-driven approach in studying the aeroelastic behaviour of turbomachinery. To the best of the authors' knowledge, this is the first time a data-driven flutter model has been investigated. The initial results are encouraging, indicating that this approach is worth pursuing in the future. The presented framework can be used as a redesign tool to enhance the flutter stability of an existing blade. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the influence of different subgrid-scale (SGS) closure models and inflow turbulence conditions on the boundary layer transition on the suction side of a highly loaded transonic turbine cascade in the presence of high free-stream turbulence using large eddy simulations (LES) of the MUR237 test case. For the numerical simulations, the MUR237 flow case was considered and the incoming free-stream turbulence was reproduced using the synthetic eddy method (SEM). The boundary layer transition on the blade suction side was found to be significantly influenced by the choice of the SGS closure model and the SEM parameters. These two aspects were carefully evaluated in this work. Initially, the influence of three different closure models (Smagorinsky, WALE, and subgrid-scale kinetic energy model) was evaluated. Among them, the WALE SGS closure model performed best compared to the Smagorinsky and KEM models and, for this reason, was used in the following analysis. Finally, different values of the turbulence length scale, eddies density, and inlet turbulence for the SEM were evaluated. As shown by the results, among the different parameters, the choice of the turbulence length scale plays a major role in the transition onset on the blade suction side. [ABSTRACT FROM AUTHOR]

Results on overall pump head and efficiency performance, pressure pulsation and high speed camera visualization of flow patterns behavior are presented for different inlet air-water void fractions at a given rotational speed. With the increase of inlet void fractions and decrease of the flow rates, the size of bubbles increase and tend to agglomerate in specific impeller passage locations along the blade chord. The starting point of pump breakdown is related to a strong inward reverse flow occurring in a specific location near the shroud gap of the impeller and volute tongue region. Using a constant air void fraction value of 2%, pressure pulsation frequency results are analyzed in relation with local flow mixture patterns and flow rate modification. [ABSTRACT FROM AUTHOR]

Variable inlet guide vanes (VIGVs) are most commonly used as the major control unit of integrally geared centrifugal compressors (IGCCs). In order to enhance the efficient operating range of the compressor, the loss mechanisms and utilization limits of state-of-the-art VIGVs need to be better understood. Field measurements in the wake of a typical, commercially used configuration were therefore conducted at the VIGV test facility of the Bundeswehr University Munich. The investigations were carried out at application oriented subsonic flow conditions and stagger angles from 50° to 90° covering the full low-loss operating range, including the limits of efficient operation. For a precise local loss characterization, an inflow correlation was developed and applied to consider total pressure inhomogeneities caused by the radial inflow velocity profile and minor circumferential velocity deviations. Contrary to previous research efforts, not only the profile losses, but also the secondary flow losses induced by the open blade tips and wall-blade interactions were resolved in full detail. For this reason, a more precise and comprehensive loss assessment of realistic VIGV cascades is acquired. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates a highly-loaded 1.5-stage transonic axial compressor, which comprises a variable inlet guide vane, a BLISK rotor, and a variable stator in tandem arrangement. A detailed comparison between the newly designed compressor stage and a reference stage with a conventional stator design was conducted by using extensive instrumentation. Thus, steady and unsteady phenomena--focusing on the aerodynamic and aeroelastic behavior--were analyzed. Due to the new stator vane design, a higher aerodynamic stator vane loading was pursued, while the vane count was reduced. This, in turn, allowed a rotor design with an increased work coefficient. This experimental study revealed several effects of the optimized compressor stage in terms of both performance and the corresponding aerodynamics, as well as the aeroelastic behavior. [ABSTRACT FROM AUTHOR]

This paper concentrates on temperature distribution in the gas turbine blade equipped by the cooling holes system on transient heat transfer. The present study requires the specification of internal and external boundary conditions. The calculations had been done using both Crank-Nicolson algorithm, explicit and implicit methods, in which different heat transfer coefficients on internal cooling surfaces of the holes were applied. The value of coefficients has a direct and crucial impact on the final result. The heat transfer coefficient of cooling the working surface of the of heat pipes was 1600 W/(m2K). It was found that there were no significant differences of temperature distribution in comparison of results from explicit method in the Ansys analysis, Crank-Nicolson algorithm and implicit method in Matlab. The simulation is based on Finite Element Method, which uses the Crank Nicolson algorithm. [ABSTRACT FROM AUTHOR]

Blades play an important role in aviation engine, gas turbine and jet engine. Inspecting the blade by optical method is a meaningful work in manufacturing industry. During optical inspecting process, one common problem encountered is that the scanned point cloud is large scale and noisy. In this paper, we present a systematic introduction of simplification, smoothing and parameter extraction with respect to point-sampled blades. First, the moving least square surface is applied to create a geometric deviation, which is used to subdivide and cluster the point cloud. Then, the information entropy in k-neighbourhood is defined to smooth point-sampled surface, meanwhile preserving high curvature feature. Furthermore, the computation method of single/multi section parameters is presented, and test experiments are performed in iCloud3D Blade V1.0. Experimental results demonstrate the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Airfoil blades are typically inspected in sections to verify their conformance to the geometric tolerances specified on their nominal design. To maintain the accuracy of geometric error evaluation, in particular, for the position and orientation errors of the airfoil sections, sectional airfoil profiles should be reconstructed from the inspection data points. This paper presents a new method to automatically reconstruct the airfoil profile from unorganized noisy sectional data points of 3D scanned blades. A three-step airfoil profile reconstruction approach is presented. First, the algorithm thins the scattered set of sectional data points by projecting them onto the local curves fitted to them. For this purpose, a recursive weighted local least-squares scheme is proposed to fit local curves within the measurement uncertainty constraint of inspection data. Then, to order the thinned set of data points, the profile polygon is generated and imperfect nodes are modified by evaluation of the angular deviation of edges. Finally, a closed nonperiodic B-spline curve is fitted to the thinned and ordered set of data points to construct the smooth airfoil profile. A series of case studies have been carried out to demonstrate the effectiveness of the proposed airfoil profile reconstruction method. Implementation results have demonstrated that the proposed method is accurate and robust to noise. In addition to blade inspection, other applications such as repair and adaptive machining of aero-engine blades can equally benefit from the proposed method for automatic airfoil profile reconstruction. [ABSTRACT FROM AUTHOR]

• Large eddy simulation method provides high precision numerical results of cavitation flow. • The bionic leading-edge protuberances induce reverse rotating vortex pairs and deflect the flow. • The bionic fin spine structure blocks the development of the attached cavitation and re-entrant jets. • The novel bionic combined structure exhibited a well cavitation inhibition effect and flow stability. Cavitation limits the efficient and stable operation of rotating machinery. The exploration of control methods for hydrofoil cavitation is important for improving the performance of hydraulic machinery. The leading-edge protuberances of the humpback flipper and the spine structure of the tail fin of sailfish are two common bionic structures for cavitation control; however, the control effects of both have limitations. Accordingly, in this study, a passive control method for hydrofoil cavitation was developed by combining the two bionic structures. With the large eddy simulation method, the cavitation processes of wavy leading-edge hydrofoil, bionic fin spine structure hydrofoil, and novel bionic combined structure hydrofoil were studied under a cavitation number of σ = 0.8. The control mechanisms of the three bionic structures for the hydrofoil cavitation were investigated. The results indicated that the novel bionic combined hydrofoil realised the superposition and complementation of the control effects of the two single bionic structures and achieved a better cavitation inhibition effect, reducing the total volume of cavitation by 43 %. In addition, it enhanced the stability of the flow field and reduced the standard deviation of the pressure coefficient on the suction surface by up to 46.55 %. This research provides theoretical support for the optimisation and modification of the blades of hydraulic machinery, such as propellers and pump turbines. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of Nanjing University of Aeronautics & Astronautics is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The work is based on experiments made in the wind tunnel on experimental models of Savonius type wind turbines with blades in the shape of a semicylindrical cup. The number of blades changes: 2, 3, 4, 5 and 6. The experimental model allows the addition / removal of blades in the form of a semi-cylindrical cup followed by static balancing. The wind tunnel used has the measuring area 0.5m x0.5m and the length of 1.25 m and the experimental models have the interception surface at a maximum value of 10% of the cross-sectional area of the wind tunnel (diameter 158mm and height 158 mm). The experiments were performed at wind speeds between 0...9.7 m/s between peaks and no (mechanical and / or electrical) loads. The results confirm the influence of the number of semi-cylindrical cups on the rotational speed and other factors over experimental model of Savonius type turbines in no load conditions. [ABSTRACT FROM AUTHOR]

A domestic purpose micro wind turbine realised using bamboo blade is tested for the power generation at an interval of two years and compared the performance. A CFD analysis of turbine with five blade system is carried out for an average wind velocity of 2.5m/s and structural integrity of the bamboo blade unit based on the pressure distribution is assessed. For the input wind velocity, a stream lined out flow of 5.9 m/s is found when wind turbine rotates at 300 rpm and corresponding pressure distribution is found to be maximum at the expected location of blade tip as129 Pa. The static analysis shows a good margin. For 2.5 m/s, a wind turbine generates an average value of 3.8V with 0.25A (based on 15 ?/10W load). The wind turbine has produced nearly the same power even after a period of two years. [ABSTRACT FROM AUTHOR]

Introduction: The vibration characteristics of a wide-chord fan blade affect the safety, reliability, and operability of high-bypass ratio turbofan engines. Objectives: In this study, the vibration characteristics of a fan blade were investigated using numerical and experimental methods. Methods: First, the natural frequencies and mode shapes were obtained and verified. Then, the rotating speed and frequency margins were employed to analyze the stability of the blade. The critical crossings in the Campbell diagram were indicated and evaluated. Next, the strain energy density index and weaklink were used to evaluate the dangerous locations for the high-cycle fatigue characteristics of the blade. Finally, single- and multi-axis random-excitation tests were performed. Results: Results indicated that low-order bending modes were dominant under circumferential- and axial-direction excitations, while the torsional mode response was higher under radial-direction excitation. The weaklinks for different excitation directions exhibited different characteristics. Conclusions: This work presents a comprehensive understanding of the fan-blade vibration and response characteristics. [ABSTRACT FROM AUTHOR]

The characteristics of the fluid–structure interaction on the flexible blades of a horizontal-axis water turbine are studied; this bioinspired technology features mechanical simplicity, performance and lifetime improvement, and low fish impact risk, all characteristics of a truly sustainable renewable energy exploitation. A surface-tracking method synchronized with force measurements was applied on a surrogate model of single-bladed, vertical-axis water turbine in a water channel. This allows for the characterization of the structural deformations and their link to the hydrodynamic forces, over a large range of turbine designs and operating points. It is shown that the phase angles of the maxima in blade deformation coincide with those of the load maxima on a rigid blade in identical flow conditions. The influence of the turbine's tip/speed ratio on the blade deformation and blade load is investigated. With the chosen blade design, hydrofoil deformation is found to be maximum in the operating points where the performance improvement is maximized ( k o = 0.3 ). With lower values of reduced frequency (corresponding to lower rotation speed), fluid-induced forces dominate the fluid–structure interaction. Conversely, at higher frequencies, structural inertia dominates the interaction, and blade deformation is again reduced. Results suggest that the optimal blade rigidity may depend on the operating point; nevertheless the potential of the flexible-blade design is demonstrated through clear linking of fluid-induced forces and blade deformation in the complex flow conditions of the Darrieus water turbine. [ABSTRACT FROM AUTHOR]

Improving pressure rise capabilities of axial compressors requires an in-depth understanding of the losses produced in the tip leakage region. Here, a generic setup that magnifies the tip region of an isolated, non-rotating blade is used with the objectives of describing the main flow components and evaluating the related sources of loss. The flow at the tip is structured by the jet flow out of the gap which, under the effect of the main stream, rolls-up into a tip-leakage vortex. The current setup is characterized by the tip gap height and the thickness of the incoming boundary layer at the casing, here a flat plate, for a given incidence of the blade. Measurements are performed using LDV and a multi-port pressure probe. Variations in the tip-leakage flow are found to be mainly driven by gap height. A small, intermediate and large gap regimes are more specifically found, with threshold around 4% and 8% of gap to chord ratio for the present setting. The incoming boundary layer thickness is shown to provoke a notable effect on the vortex lateral position and total pressure losses. The local entropy creation rate is computed from LDV data and used to identify the sources of loss in the flow. A decomposition into wake and vortex losses is further proposed, allowing to relate the contributions of the various flow components to the overall losses. An empirical model of the formation of the tip vortex is developed to account for the increased losses as a function of gap height. The model provides a useful mean for the practical approximation of the gap sensitivity of pressure losses. [ABSTRACT FROM AUTHOR]

In this study, we propose a new algorithm to solve the rectangular strip packing problem (RSPP), a variant of the cutting stock problem in which the mother materials have a common fixed width and infinite length. Based on the column-generation technique with three improvements, the proposed algorithm can solve large-scale problems involving tens of thousands of materials within a reasonable time, considering practical cutting constraints, i.e., the three-stage guillotine cutting constraint and the limitations of slitter blades. The proposed algorithm is evaluated in terms of its packing efficiency and calculation time. [ABSTRACT FROM AUTHOR]

Currently, 3D-CFD design optimization of centrifugal compressors in terms of the surge margin is one major unresolved issue. On that account, this paper introduces a new kind of objective function. The objective function is based on local flow parameters present at the design point of the centrifugal compressor. A centrifugal compressor with a vaned diffuser is considered to demonstrate the performance of this approach. By means of a variation of the beta angle distribution of the impeller and diffuser blade, 73 design variations are generated, and several local flow parameters are evaluated. Finally, the most promising flow parameter is transferred into an objective function, and an optimization is carried out. It is shown that the new approach delivers similar results as a comparable optimization with a classic objective function using two operating points for surge margin estimation, but with less computational effort since no second operating point near the surge needs to be considered. [ABSTRACT FROM AUTHOR]

Characterization of the shock response of biological materials is required in order to develop an understanding of how such materials behave under high strain-rate loading. In this work, a predominately linear Us-up Hugoniot relationship for a rendered porcine fat has been established using the plate-impact technique. This has been shown to take the form Us=1.58+2.47up (ρ0=0.945 g/cc) and comparison has been made between the dynamic behavior of the adipose material and both 20 wt % ballistic gelatin and water. The adipose material has been shown to behave in likeness with simple polymers such as polyethylene and to strengthen under shock loading, unlike ballistic gelatin, which has been shown to behave hydrodynamically. An experimental design incorporating direct insertion of lateral stress gauges within the rendered fat has given insight into both the behavior of lateral gauges and the lateral stress response of the material under dynamic loading. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to clarify the effects of blade design and oar length on performance in rowing. Biomechanical models and equations of motion were developed to identify the main forces that affect rowing performance. In addition, the mechanical connection between the propelling blade force and the force that the rower applies on the handle was established. On this basis it was found that the blade design and oar dimensions play a significant role on the rowing performance. While rowers have found empirically that larger and/or hydrodynamically more efficient blade shapes need to be rowed with shorter oars, this article explains this tendency from a biomechanical point of view. Based on the presented evidence, it can be concluded that shorter oars will allow rowers to improve the propelling forces without increasing the handle forces. These findings explain tendencies that started with the introduction of new blade shapes in 1991. A 2 × 2 factorial ANOVA was used to test the significance of the oar shortenings that occurred with the introduction of larger blade surfaces while international record times improved during all those years. Consequently, the findings of this investigation encourage coaches to further experiment with shorter oars and oar manufacturers to continue their blade development that would lead to even shorter oars, with the goal of continuous rowing performance improvements. [ABSTRACT FROM AUTHOR]

The Side milling of ruled surfaces using a conical milling cutter was studied. This is a field that has largely been ignored by research scientists, but it is much used in industry, especially to machine turbine blades. In this study, we first suggest an improved positioning with respect to the directrices of the ruled surface. As compared with the methods already developed for the cylindrical cutter, this positioning enables the error between the cutter and the work-piece to be reduced. An algorithm is then introduced to calculate error so one can determine the cutter dimensions (cone radius and angle) in order to respect the tolerance interval imposed by the design office. This study provides an opportunity to determine cutters with greater dimensions, thus alleviating bending problems during milling. [ABSTRACT FROM AUTHOR]

The article discusses La Omaha Mariachi Dyke, which includes three things you need to know when you work the kill floor in a meatpacking plant. One: No one is going to watch your back. Two: No one is going to watch your back. When the swish of the blade comes down, you make sure it's coming down on the rib, the loin, or the shank not on your elbow, wrist, or fingers. Three: The speed of the line will always increase day to day, month to month.