http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Thu, 30 May 2013 08:36:02 +0000 http://www.hindawi.com/journals/ijrm/2013/985943/ The Darrieus turbine is a suitable power generation in free stream flow because it is simple in construction, but it has the disadvantage of its small starting torque. The Savonius turbine has a high starting torque but the efficiency is smaller than that of Darrieus turbine. To improve the starting torque of Darrieus turbine, the Savonius buckets are introduced into the Darrieus turbine and the combined turbine is called Darrieus-Savonius turbine. In this study, three semielliptic sections of aspect ratio 0.8 were used for Savonius bucket while the Darrieus blade used three wings of airfoil NACA 0015. The Darrieus-Savonius turbine’s performances were studied experimentally in an irrigation canal of South Sumatera, Indonesia. The results show that the distance of Savonius buckets from the shaft centre influences performance of combined turbine, and the attachment angle of Savonius rotor made important variation of turbine performance. Kaprawi Sahim, Dyos Santoso, and Agus Radentan Copyright © 2013 Kaprawi Sahim et al. All rights reserved. Mon, 20 May 2013 14:41:25 +0000 http://www.hindawi.com/journals/ijrm/2013/512674/ This paper shows a theoretical vibration analysis regarding the controller’s parameters and the gyroscopic effect, based on a simplified rotordynamic model. Combined with 600 Wh energy storage flywheel rotor system mathematical model, the Campbell diagram of the rotor system was obtained by the calculation of the whirl frequency under different parameters of the controller in MATLAB to analyze the effect of the controller parameter on the whirl frequency and to limit the operating speed and acceleration or deceleration of the rotor. The result of the analysis can be used to set the support position of the rotor system, limit the ratio of transverse moment of inertia and the polar moment of inertia, and direct the flywheel prototype future design. The presented simplified rotordynamic model can also be applied to rotating machines. Jing-na Liu, Zheng-yi Ren, Shan-wei Wu, and Yin-long Tang Copyright © 2013 Jing-na Liu et al. All rights reserved. Sun, 31 Mar 2013 17:41:14 +0000 http://www.hindawi.com/journals/ijrm/2013/275653/ To provide an overview of the current state of the art of heat transfer augmentation schemes employed for internal cooling of turbine blades and components, results from an extensive literature review are presented with data from internal cooling channels, both with and without rotation. According to this survey, a very small number of existing investigations consider the use of combination devices for internal passage heat transfer augmentation. Examples are rib turbulators, pin fins, and dimples together, a combination of pin fins and dimples, and rib turbulators and pin fins in combination. The results of such studies are compared with data obtained prior to 2003 without rotation influences. Those data are comprised of heat transfer augmentation results for internal cooling channels, with rib turbulators, pin fins, dimpled surfaces, surfaces with protrusions, swirl chambers, or surface roughness. This comparison reveals that all of the new data, obtained since 2003, collect within the distribution of globally averaged data obtained from investigations conducted prior to 2003 (without rotation influences). The same conclusion in regard to data distributions is also reached in regard to globally averaged thermal performance parameters as they vary with friction factor ratio. These comparisons, made on the basis of such judgment criteria, lead to the conclusion that improvements in our ability to provide better spatially-averaged thermal protection have been minimal since 2003. When rotation is present, existing investigations provide little evidence of overall increases or decreases in overall thermal performance characteristics with rotation, at any value of rotation number, buoyancy parameter, density ratio, or Reynolds number. Comparisons between existing rotating channel experimental data and the results obtained prior to 2003, without rotation influences, also show that rotation has little effect on overall spatially-averaged thermal performance as a function of friction factor. Phil Ligrani Copyright © 2013 Phil Ligrani. All rights reserved. Wed, 20 Mar 2013 16:12:38 +0000 http://www.hindawi.com/journals/ijrm/2013/189359/ The paper illustrates the design and the implementation of a Fault Detection and Isolation (FDI) system to a rotary machine like a multishaft centrifugal compressor. A model-free approach, that is, the Principal Component Analysis (PCA), has been employed to solve the fault detection issue. For the fault isolation purpose structured residuals have been adopted while an adaptive threshold has been designed in order to detect and to isolate the faults. To prove the goodness of the proposed FDI system, historical data of a nitrogen centrifugal compressor employed in a refinery plant are considered. Tests results show that detection and isolation of single as well as multiple faults are successfully achieved. Silvia M. Zanoli and Giacomo Astolfi Copyright © 2013 Silvia M. Zanoli and Giacomo Astolfi. All rights reserved. Thu, 21 Feb 2013 08:47:44 +0000 http://www.hindawi.com/journals/ijrm/2013/856865/ Diagnosis and condition monitoring in rotating machinery has been a subject of intense research for the last century. Recent developments indicate the drive towards integration of diagnosis and prognosis algorithms in future integrated vehicle health management (IVHM) systems. With this in mind, this paper concentrates on highlighting some of the latest research on common faults in rotating machines. Eight key faults have been described; the selected faults include unbalance, misalignment, rub/looseness, fluid-induced instability, bearing failure, shaft cracks, blade cracks, and shaft bow. Each of these faults has been detailed with regard to sensors, fault identification techniques, localization, prognosis, and modeling. The intent of the paper is to highlight the latest technologies pioneering the drive towards next-generation IVHM systems for rotating machinery. Ryan Walker, Sureshkumar Perinpanayagam, and Ian K. Jennions Copyright © 2013 Ryan Walker et al. All rights reserved. Wed, 30 Jan 2013 19:00:39 +0000 http://www.hindawi.com/journals/ijrm/2013/857616/ An unsteady analysis of the MIT counterrotating aspirated compressor (CRAC) has been conducted using the Numeca FINE/Turbo 3D viscous turbulent flow solver with the Nonlinear Harmonic (NLH) method. All three blade rows plus the aspiration slot and plenum were included in the computational domain. Both adiabatic and isothermal solid wall boundary conditions were applied and simulations with and without aspiration were completed. The aspirated isothermal boundary condition solutions provide the most accurate representation of the trends produced by the experiment, particularly at the endwalls. These simulations provide significant insight into the flow physics of the aspiration flow path. Time histories and spanwise distributions of flow properties in the aspiration slot and plenum present a flow field with significant temporal and spatial variations. In addition, the results provide an understanding of the aspiration flow path choking mechanism that was previously not well understood and is consistent with experimental results. The slot and plenum had been designed to aspirate 1% of the flow path mass flow, whereas the experiment and simulations show that it chokes at about 0.5% mass flow. Robert D. Knapke and Mark G. Turner Copyright © 2013 Robert D. Knapke and Mark G. Turner. All rights reserved. Wed, 30 Jan 2013 17:05:08 +0000 http://www.hindawi.com/journals/ijrm/2013/372181/ N. Sitaram, K. Funazaki, and Seyed G. Saddoughi Copyright © 2013 N. Sitaram et al. All rights reserved. Tue, 25 Dec 2012 07:54:54 +0000 http://www.hindawi.com/journals/ijrm/2012/248082/ Passive flow control techniques are used to improve the flow field and efficiency of centrifugal pumps and turbomachines, in general. An important phenomenon that mechanical engineers have to take into account is cavitation. It leads to the decrease of the pump performance and total head. In the present experimental study, a centrifugal pump is investigated in cavitating conditions. A passive flow control is realized using three different blade leading edge angles in order to reduce the cavitation development and enhance the pump performance. The experiments are carried out in a pump test rig specially designed and constructed, along with the impellers. The head drop and total efficiency curves are presented in order to examine the effect of the blade leading edge angle on the cavitation and pump performance. Finally, the vapour distribution along with the blades is illustrated for the tested blade leading edge angles. Spyridon D. Kyparissis and Dionissios P. Margaris Copyright © 2012 Spyridon D. Kyparissis and Dionissios P. Margaris. All rights reserved. Thu, 13 Dec 2012 11:44:35 +0000 http://www.hindawi.com/journals/ijrm/2012/902548/ Active flow control using dielectric barrier discharge (DBD) plasma actuators was investigated to reattach the simulated boundary layer separation on the suction surface of a turbine blade at low Reynolds number, Re = 1.7 × 104. The flow separation is induced on a curved plate installed in the test section of a low-speed wind tunnel. Particle image velocimetry (PIV) was used to obtain instantaneous and time-averaged two-dimensional velocity measurements. The amplitude of input voltage for the plasma actuator was varied from ±2.0 kV to ±2.8 kV. The separated flow reattached on the curved wall when the input voltage was ±2.4 kV and above. The displacement thickness of the boundary layer near the trailing edge decreased by 20% at ±2.0 kV. The displacement thickness was suddenly reduced as much as 56% at ±2.2 kV, and it was reduced gradually from ±2.4 kV to ±2.8 kV (77% reduction). The total pressure loss coefficient, estimated from the boundary layer displacement thickness and momentum thickness, was 0.172 at the baseline (actuator off) condition. The total pressure loss was reduced to 0.107 (38% reduction) at ±2.2 kV and 0.078 (55% reduction) at ±2.8 kV. Takayuki Matsunuma and Takehiko Segawa Copyright © 2012 Takayuki Matsunuma and Takehiko Segawa. All rights reserved. Wed, 12 Dec 2012 09:40:11 +0000 http://www.hindawi.com/journals/ijrm/2012/549048/ The aim of the present study is to evaluate the efficiency of a boundary layer suction technique in case of a centrifugal compressor stage in order to extend its stable operating range. First, an analysis of the flow pattern within the radial vaned diffuser is presented. It highlights the stall of the diffuser vanes when reaching a low massflow. A boundary layer separation in the hub-suction side corner grows when decreasing the massflow from the nominal operating point to the surge and finally leads to a massive stall. An aspiration strategy is investigated in order to control the stall. The suction slot is put in the vicinity of the saddle that originates the main separating skin-friction line, identified thanks to the analysis of the skin-friction pattern. Several aspiration massflow rates are tested, and two different modelings of the aspiration are evaluated. Finally, an efficient control is reached with a removal of only 0,1% of the global massflow and leads—from a steady-state calculations point of view—to an increase by 40% of the compressor operating range extent. Aurélien Marsan, Isabelle Trébinjac, Sylvain Coste, and Gilles Leroy Copyright © 2012 Aurélien Marsan et al. All rights reserved. Tue, 11 Dec 2012 15:26:51 +0000 http://www.hindawi.com/journals/ijrm/2012/619459/ Helical groove seal is designed in reactor coolant pump to control the leakage along the front surface of the impeller face due to its higher resistance than the circumferentially grooved seal. The flow and the friction factors in helical groove seals are predicted by employing a commercial CFD code, FLUENT. The friction factors of the helical groove seals with helix angles varying from 20 deg to 50 deg, at a range of rotational speed and axial Reynolds number, were, respectively, calculated. For the helically grooved stator with the helix angle greater than 20 deg, the leakage shows an upward trend with the helix angle. The circumferentially grooved stator has a lower resistance to leakage than the 20 deg and 30 deg stators. It can be predicated that, for a bigger helix angle, the friction factor increases slightly with an increase in high axial Reynolds number, which arises from the high-pressure operation condition, and the friction factor is generally sensitive to changes in the helix angle in this operation condition. The study lays the theoretical foundation for liquid seal design of reactor coolant pump and future experimental study to account for the high-pressure condition affecting the leakage characteristic. Meng Zhang, Xiao-fang Wang, Sheng-li Xu, and Shuo Yin Copyright © 2012 Meng Zhang et al. All rights reserved. Tue, 11 Dec 2012 12:43:18 +0000 http://www.hindawi.com/journals/ijrm/2012/370425/ Ryoichi S. Amano, Abraham Engeda, Ashwani K. Gupta, Bengt Sunden, and Cheng Xu Copyright © 2012 Ryoichi S. Amano et al. All rights reserved. Tue, 11 Dec 2012 09:25:06 +0000 http://www.hindawi.com/journals/ijrm/2012/823831/ Ducted propellers, in decelerating duct configuration, may represent a possible solution for the designer to reduce cavitation and its side effects, that is, induced pressures and radiated noise; however, their design still presents challenges, due to the complex evaluation of the decelerating duct effects and to the limited amount of available experimental information. In the present paper, a hybrid design approach, adopting a coupled lifting line/panel method solver and a successive refinement with panel solver and optimization techniques, is presented. In order to validate this procedure and provide information about these propulsors, experimental results at towing tank and cavitation tunnel are compared with numerical predictions. Moreover, additional results obtained by means of a commercial RANS solver, not directly adopted in the design loop, are also presented, allowing to stress the relative merits and shortcomings of the different numerical approaches. Stefano Gaggero, Cesare M. Rizzo, Giorgio Tani, and Michele Viviani Copyright © 2012 Stefano Gaggero et al. All rights reserved. Wed, 05 Dec 2012 13:11:51 +0000 http://www.hindawi.com/journals/ijrm/2012/518381/ Centrifugal compressor developments are interested in using optimization procedures that enable compressor high efficiency and wide operating ranges. Recently, high pressure ratio and efficiency of the centrifugal compressors require impeller design to pay attention to both the blade angle distribution and the meridional profile. The geometry of the blades and the meridional profile are very important contributions of compressor performance and structure reliability. This paper presents some recent studies of meridional impacts of the compressor. Studies indicated that the meridional profiles of the impeller impact the overall compressor efficiency and pressure ratio at the same rotational speed. Proper meridional profiles can improve the compressor efficiency and increase the overall pressure ratio at the same blade back curvature. C. Xu and R. S. Amano Copyright © 2012 C. Xu and R. S. Amano. All rights reserved. Tue, 04 Dec 2012 11:45:01 +0000 http://www.hindawi.com/journals/ijrm/2012/687354/ The ability to predict the nature of instabilities is highly important from the compressor design point of view since their consequences could result in widely varying difficulties with the fluid dynamic performance of the systems. Even though the behavior of surge and rotating stall is reported in many literatures, it is noticed that an in-depth analysis is not undertaken. Hence in view of the importance for a deeper understanding, the present paper is aimed at tracking the chaos of these instabilities in a more detailed manner. Primarily the influence of geometric parameters on the nature of surge and rotating stall is investigated. The effect of each of the major geometric parameters such as compressor effective length, annulus area, and plenum volume is discussed. The physical reason for the onset of instabilities is also explained in each case, and the well-accepted Moore-Greitzer model has been used for the present study. The combined effect of physical parameters is determined through the Greitzer parameter. The results shown in this paper clearly elucidate the dominating effect of the geometric parameters on the development of flow instabilities like rotating stall and surge and hence can serve as a design guideline to avoid such instabilities. Ananth Sivaramakrishnan Malathi and A. Kushari Copyright © 2012 Ananth Sivaramakrishnan Malathi and A. Kushari. All rights reserved. Tue, 27 Nov 2012 11:54:41 +0000 http://www.hindawi.com/journals/ijrm/2012/142595/ Yin Lu Young, Moustafa Abdel-Maksoud, Jules W. Lindau, Francesco Salvatore, and Moon Chan Kim Copyright © 2012 Yin Lu Young et al. All rights reserved. Thu, 22 Nov 2012 15:19:52 +0000 http://www.hindawi.com/journals/ijrm/2012/601837/ A combined experimental and computational study was conducted to investigate the erosion of thermal barrier coated (TBC) blade surfaces by alumina particles ingestion in a single-stage turbine. In the experimental investigation, tests were performed to determine the erosion rates and particle restitution characteristics under different impact conditions. The experimental results show that the erosion rates increase with increased impingement angle, impact velocity, and temperature. In the computational simulations, an Euler-Lagrangian two-stage approach is used in obtaining numerical solutions to the three-dimensional compressible Reynolds-Averaged Navier-Stokes equations and the particles equations of motion in each blade passage reference frame. User defined functions (UDFs) were developed to represent experimentally based correlations for particle surface interaction models and TBC erosion rates models. UDFs were employed in the three-dimensional particle trajectory simulations to determine the particle rebound characteristics and TBC erosion rates on the blade surfaces. Computational results are presented in a commercial turbine and a NASA-designed automotive turbine. The similarities between the erosion patterns in the two turbines are discussed for uniform particle ingestion and for particle ingestion concentrated in the inner and outer 5% of the stator blade span to represent the flow cooling of the combustor liner. Rohan Swar, Awatef Hamed, Dongyun Shin, Nathanial Woggon, and Robert Miller Copyright © 2012 Rohan Swar et al. All rights reserved. Thu, 22 Nov 2012 14:52:29 +0000 http://www.hindawi.com/journals/ijrm/2012/640794/ Fault detection and isolation (FDI) in rotor systems often faces the problem that the system dynamics is dependent on the rotor rotary frequency because of the gyroscopic effect. In unbalance excited rotor systems, the continuously distributed unbalances are hard to be determined or estimated accurately. The unbalance forces as disturbances make fault detection more complicated. The aim of this paper is to develop linear time invariant (LTI) FDI methods (i.e., with constant parameters) for rotor systems under consideration of gyroscopic effect and disturbances. Two approaches to describe the gyroscopic effect, that is, as unknown inputs and as model uncertainties, are investigated. Based on these two approaches, FDI methods are developed and the results are compared regarding the resulting FDI performances. Results are obtained by the application in a rotor test rig. Restrictions for the application of these methods are discussed. Zhentao Wang, Arne Wahrburg, and Stephan Rinderknecht Copyright © 2012 Zhentao Wang et al. All rights reserved. Wed, 14 Nov 2012 13:14:06 +0000 http://www.hindawi.com/journals/ijrm/2012/259293/ The passive control method for surge and rotating stall in centrifugal compressors by using a nozzle injection system was proposed to extend the stable operating range to the low flow rate. A part of the flow at the scroll outlet of a compressor was recirculated to an injection nozzle installed on the inner wall of the suction pipe of the compressor through the bypass pipe and injected to the impeller inlet. Two types of compressors were tested at the rotational speeds of 50,000 rpm and 60,000 rpm with the parameter of the circumferential position of the injection nozzle. The present experimental results revealed that the optimum circumferential position, which most effectively reduced the flow rate for the surge inception, existed at the opposite side of the tongue of the scroll against the rotational axis and did not depend on the compressor system and the rotational speeds. Toshiyuki Hirano, Takanori Uchida, and Hoshio Tsujita Copyright © 2012 Toshiyuki Hirano et al. All rights reserved. Wed, 14 Nov 2012 08:25:45 +0000 http://www.hindawi.com/journals/ijrm/2012/928623/ Experiments were conducted on the flow through a transonic turbine cascade. Secondary flows and a wide range of vortex types were encountered, including horseshoe vortices, shock-induced passage vortices, and streamwise vortices on the suction surface. In the separation region on the suction surface, a large rollup of passage vorticity occurred. The blunt leading edge gave rise to strong horseshoe vortices and secondary flows. The suction surface had a strong convex curvature over the forward portion and was quite flat further downstream. Surface flow visualization was performed and this convex surface displayed coherent streamwise vorticity. At subsonic speeds, strong von Kármán vortex shedding resulted in a substantial base pressure deficit. For these conditions, time-resolved measurements were made of the Eckert-Weise energy separation in the blade wake. At transonic speeds, exotic shedding modes were observed. These phenomena all occurred in experiments on the flow around one particular turbine nozzle vane in a linear cascade. J. P. Gostelow, A. Mahallati, W. E. Carscallen, and A. Rona Copyright © 2012 J. P. Gostelow et al. All rights reserved. Mon, 12 Nov 2012 08:35:01 +0000 http://www.hindawi.com/journals/ijrm/2012/246031/ This study presents the numerical fluid-structure interaction (FSI) modelling of a vibrating turbine blade using the commercial software ANSYS-12.1. The study has two major aims: (i) discussion of the current state of the art of modelling FSI in gas turbine engines and (ii) development of a “tuned” one-way FSI model of a vibrating turbine blade to investigate the correlation between the pressure at the turbine casing surface and the vibrating blade motion. Firstly, the feasibility of the complete FSI coupled two-way, three-dimensional modelling of a turbine blade undergoing vibration using current commercial software is discussed. Various modelling simplifications, which reduce the full coupling between the fluid and structural domains, are then presented. The one-way FSI model of the vibrating turbine blade is introduced, which has the computational efficiency of a moving boundary CFD model. This one-way FSI model includes the corrected motion of the vibrating turbine blade under given engine flow conditions. This one-way FSI model is used to interrogate the pressure around a vibrating gas turbine blade. The results obtained show that the pressure distribution at the casing surface does not differ significantly, in its general form, from the pressure at the vibrating rotor blade tip. Osama N. Alshroof, Gareth L. Forbes, Nader Sawalhi, Robert B. Randall, and Guan H. Yeoh Copyright © 2012 Osama N. Alshroof et al. All rights reserved. Thu, 08 Nov 2012 11:28:46 +0000 http://www.hindawi.com/journals/ijrm/2012/103583/ Heat transfer and pressure drop for a representative part of a turbine active cooling system were numerically investigated by means of an in-house code. This code has been developed in the framework of an internal research program and has been validated by experiments and CFD. The analysed system represents the classical open bird cage arrangement that consists of an air supply pipe with a control valve and the present system with a collector box and pipes, which distribute cooling air in circumferential direction of the casing. The cooling air leaves the ACC system through small holes at the bottom of the tubes. These tubes extend at about 180° around the casing and may involve a huge number of impinging holes; as a consequence, the impinging jets mass flow rate may vary considerably along the feeding manifold with a direct impact on the achievable heat transfer levels. This study focuses on the performance, in terms of heat transfer coefficient and pressure drop, of several impinging tube geometries. As a result of this analysis, several design solutions have been compared and discussed. Riccardo Da Soghe, Bruno Facchini, Mirko Micio, and Antonio Andreini Copyright © 2012 Riccardo Da Soghe et al. All rights reserved. Tue, 30 Oct 2012 10:47:25 +0000 http://www.hindawi.com/journals/ijrm/2012/847203/ This paper deals with the maintenance technique for industrial machinery using the artificial neural network so-called self-organizing map (SOM). The aim of this work is to develop intelligent maintenance system for machinery based on an alternative way, namely, thermal images instead of vibration signals. SOM is selected due to its simplicity and is categorized as an unsupervised algorithm. Following the SOM training, machine fault diagnostics is performed by using the pattern recognition technique of machine conditions. The data used in this work are thermal images and vibration signals, which were acquired from machine fault simulator (MFS). It is a reliable tool and is able to simulate several conditions of faulty machine such as unbalance, misalignment, looseness, and rolling element bearing faults (outer race, inner race, ball, and cage defects). Data acquisition were conducted simultaneously by infrared thermography camera and vibration sensors installed in the MFS. The experimental data are presented as thermal image and vibration signal in the time domain. Feature extraction was carried out to obtain salient features sensitive to machine conditions from thermal images and vibration signals. These features are then used to train the SOM for intelligent machine diagnostics process. The results show that SOM can perform intelligent fault diagnostics with plausible accuracies. Achmad Widodo, Djoeli Satrijo, Toni Prahasto, Gang-Min Lim, and Byeong-Keun Choi Copyright © 2012 Achmad Widodo et al. All rights reserved. Thu, 18 Oct 2012 16:01:47 +0000 http://www.hindawi.com/journals/ijrm/2012/408135/ The main theoretical and numerical aspects of a design method for optimum contrar-rotating (CR) propellers for fast marine crafts are presented. We propose a reformulated version of a well-known design theory for contra-rotating propellers, by taking advantage of a new fully numerical algorithm for the calculation of the mutually induced velocities and introducing new features such as numerical lifting surface corrections, use of an integrated modern cavitation/strength criteria, a modified method to consider different numbers of blades among the two propellers, and to allow for an unloading function in the search for the optimal circulation distribution. The paper first introduces the main theoretical principles of the new methods and then discusses the influence of the main design parameters on an emblematic example of application in the case of counter rotating propellers for a pod propulsor designed for fast planing crafts (35 knots and above). Stefano Brizzolara, Davide Grassi, and Emilio P. Tincani Copyright © 2012 Stefano Brizzolara et al. All rights reserved. Thu, 16 Aug 2012 16:21:51 +0000 http://www.hindawi.com/journals/ijrm/2012/589720/ Due to increased demands for improved fuel economy of passenger cars, low-end and part-load performance is of key importance for the design of automotive turbocharger turbines. In an automotive drive cycle, a turbine which can extract more energy at high pressure ratios and lower rotational speeds is desirable. In the literature it is typically found that radial turbines provide peak efficiency at speed ratios of 0.7, but at high pressure ratios and low rotational speeds the blade speed ratio will be low and the rotor will experience high values of positive incidence at the inlet. Based on fundamental considerations, it is shown that mixed flow turbines offer substantial advantages for such applications. Moreover, to prove these considerations an experimental assessment of mixed flow turbine efficiency and optimal blade speed ratio is presented. This has been achieved using a new semi-unsteady measurement approach. Finally, evidence of the benefits of mixed flow turbine behaviour in engine operation is given. Regarding turbocharged engine simulation, the benefit of wide-ranging turbine map measurement data as well as the need for reasonable turbine map extrapolation is illustrated. Bernhardt Lüddecke, Dietmar Filsinger, and Jan Ehrhard Copyright © 2012 Bernhardt Lüddecke et al. All rights reserved. Mon, 13 Aug 2012 13:04:22 +0000 http://www.hindawi.com/journals/ijrm/2012/618180/ The numerical predictions of the cavitating flow around two model scale propellers in uniform inflow are presented and discussed. The simulations are carried out using a commercial CFD solver. The homogeneous model is used and the influence of three widespread mass transfer models, on the accuracy of the numerical predictions, is evaluated. The mass transfer models in question share the common feature of employing empirical coefficients to adjust mass transfer rate from water to vapour and back, which can affect the stability and accuracy of the predictions. Thus, for a fair and congruent comparison, the empirical coefficients of the different mass transfer models are first properly calibrated using an optimization strategy. The numerical results obtained, with the three different calibrated mass transfer models, are very similar to each other for two selected model scale propellers. Nevertheless, a tendency to overestimate the cavity extension is observed, and consequently the thrust, in the most severe operational conditions, is not properly predicted. Mitja Morgut and Enrico Nobile Copyright © 2012 Mitja Morgut and Enrico Nobile. All rights reserved. Tue, 07 Aug 2012 14:03:19 +0000 http://www.hindawi.com/journals/ijrm/2012/257461/ A boundary element method (BEM) and a vortex-lattice method (VLM) are extended in order to predict the unsteady performance of propellers subject to rigid body motions. The methods are applied in the case of prescribed surge and heave motions, and the results are compared with those from other methods. Spyros A. Kinnas, Ye Tian, and Abhinav Sharma Copyright © 2012 Spyros A. Kinnas et al. All rights reserved. Tue, 07 Aug 2012 09:15:35 +0000 http://www.hindawi.com/journals/ijrm/2012/215678/ The objective of this paper is to evaluate the predictive capability of three popular transport equation-based cavitation models for the simulations of partial sheet cavitation and unsteady sheet/cloud cavitating flows around a stationary NACA66 hydrofoil. The 2D calculations are performed by solving the Reynolds-averaged Navier-Stokes equation using the CFD solver CFX with the k-ω SST turbulence model. The local compressibility effect is considered using a local density correction for the turbulent eddy viscosity. The calculations are validated with experiments conducted in a cavitation tunnel at the French Naval Academy. The hydrofoil has a fixed angle of attack of 𝛼=6° with a Reynolds number of Re = 750,000 at different cavitation numbers 𝜎. Without the density modification, over-prediction of the turbulent viscosity near the cavity closure reduces the cavity length and modifies the cavity shedding characteristics. The results show that it is important to capture both the mean and fluctuating values of the hydrodynamic coefficients because (1) the high amplitude of the fluctuations is critical to capturing the extremes of the loads to ensure structural safety and (2) the need to capture the frequency of the fluctuations, to avoid unwanted noise, vibrations, and accelerated fatigue issues. Antoine Ducoin, Biao Huang, and Yin Lu Young Copyright © 2012 Antoine Ducoin et al. All rights reserved. Tue, 07 Aug 2012 08:41:02 +0000 http://www.hindawi.com/journals/ijrm/2012/340439/ This paper presents a numerical investigation of the effects of a nonuniform tip clearance profile on the performance and flow field in a centrifugal compressor with a vaneless diffuser. This study focuses in particular on the magnitude and location of the wake. Six impellers with different tip clearance profiles were tested in the flow simulations. The accuracy of the numerical simulations was assessed by comparing the experimental data with the computational results for a system characterized by the original tip clearance. Although the performance improved for low tip clearances, a low tip clearance at the trailing edge improved the compressor performance more significantly than a low tip clearance at the leading edge. The flow field calculated for a system characterized by a low tip clearance at the trailing edge produced a more uniform velocity distribution both in the circumferential and in the axial directions at the impeller exit because the wake magnitude was reduced. As a consequence, this impeller provided a better potential for diffusion processes inside a vaneless diffuser. Yohan Jung, Minsuk Choi, Seonghwan Oh, and Jehyun Baek Copyright © 2012 Yohan Jung et al. All rights reserved. Sun, 05 Aug 2012 09:11:35 +0000 http://www.hindawi.com/journals/ijrm/2012/372364/ A low order panel method is used to predict the performance of propellers. A wake alignment model based on a pseudounsteady scheme is proposed and implemented. The results from this full wake alignment (FWA) model are correlated with available experimental data, and results from RANS for some propellers at design and low advance ratios. Significant improvements have been found in the predicted integrated forces and pressure distributions. Ye Tian and Spyros A. Kinnas Copyright © 2012 Ye Tian and Spyros A. Kinnas. All rights reserved.