bluuebunny/crossref_metadata_2025 huggingface dataset:
INTERACTING RELATIVISTIC PARTICLE: TIME–SPACE NONCOMMUTATIVITY AND SYMMETRIES
Authors: MALIK R. P.
Published: March 2007

We discuss the symmetry properties of the reparametrization invariant model of an interacting relativistic particle where the electromagnetic field is taken as the constant background field. The direct coupling between the relativistic particle and the electromagnetic gauge potential is a special case of the above with a specific set of subtleties involved in it. For the above model, we demonstrate the existence of a time–space noncommutativity (NC) in the space–time structure from the symmetry considerations alone. We further show that the NC and commutativity properties of this model are different aspects of a unique continuous gauge symmetry that is derived from the nonstandard gauge-type symmetry transformations by requiring their consistency with (i) the equations of motion, and (ii) the expressions for the canonical momenta, derived from the Lagrangians. We provide a detailed discussion on the noncommutative deformation of the Poincaré algebra.
AMOEBAS AND INSTANTONS
Authors: MAEDA TAKASHI , NAKATSU TOSHIO
Published: March 2007

We study a statistical model of random plane partitions. The statistical model has interpretations as five-dimensional [Formula: see text] supersymmetric SU (N) Yang–Mills on ℝ4× S1and as Kähler gravity on local SU (N) geometry. At the thermodynamic limit a typical plane partition called the limit shape dominates in the statistical model. The limit shape is linked with a hyperelliptic curve, which is a five-dimensional version of the SU (N) Seiberg–Witten curve. Amoebas and the Ronkin functions play intermediary roles between the limit shape and the hyperelliptic curve. In particular, the Ronkin function realizes an integration of thermodynamical density of the main diagonal partitions, along one-dimensional slice of it and thereby is interpreted as the counting function of gauge instantons. The radius of S1can be identified with the inverse temperature of the statistical model. The large radius limit of the five-dimensional Yang–Mills is the low temperature limit of the statistical model, where the statistical model is frozen to a ground state that is associated with the local SU (N) geometry. We also show that the low temperature limit corresponds to a certain degeneration of amoebas and the Ronkin functions known as tropical geometry.
Molecular mechanism of rat NHE3 gene promoter regulation by sodium butyrate
Authors: Kiela Pawel R. , Kuscuoglu Nesrin , Midura Anna J. , Midura-Kiela Monica T. , Larmonier Claire B. , Lipko Maciej , Ghishan Fayez K.
Published: March 2007

Sodium butyrate (NaB) stimulates sodium and water absorption by inducing colonic Na+/H+ exchange. NaB induces Na+/H+ exchanger (NHE)3 activity and protein and mRNA expression both in vivo and in vitro. Our previously published observations indicated that this induction is Ser/Thr kinase dependent and that NaB-responsive elements were localized within −320/−34 bp of the rat NHE3 promoter. Here we further delineate the mechanism of NaB-mediated NHE3 gene transcription. Transient and stable transfection of Caco-2 cells with NHE3 gene reporter constructs identified Sp binding site SpB at position −58/−55 nt as critical for NaB-mediated induction. Gel mobility shift (GMSA) and DNA affinity precipitation assays indicated NaB-induced binding of Sp3 and decreased binding of Sp1 to SpB element. While no changes in expression of Sp1 or Sp3 were noted, NaB induced phosphorylation of Sp1 and acetylation of Sp3. Sp3 was a more potent inducer of NHE3 gene transcription, which suggested that change in balance, favoring binding of Sp3 to the SpB site, would result in significant increase in NHE3 promoter activity. Small interfering RNA studies in Caco-2 cells and data from NaB-treated SL2 cells used as a reconstitution model confirmed this hypothesis. In addition to the SpB site, which played a permissive role, an upstream novel butyrate response element located at −196/−175 nt was necessary for maximal induction. GMSA identified a protein-DNA complex with a −196/−175 nt probe; this interaction was not affected by NaB treatment, thus suggesting that in response to NaB Sp3 binding to site SpB precedes and results in recruitment of the putative factor to this upstream site.
Autoactivation of matriptase in vitro: requirement for biomembrane and LDL receptor domain
Authors: Lee Ming-Shyue , Tseng I-Chu , Wang Youhong , Kiyomiya Ken-ichi , Johnson Michael D. , Dickson Robert B. , Lin Chen-Yong
Published: March 2007

In live cells, autoactivation of matriptase, a membrane-bound serine protease, can be induced by lysophospholipids, androgens, and the polyanionic compound suramin. These structurally distinct chemicals induce different signaling pathways and cellular events that somehow, in a cell type-specific manner, lead to activation of matriptase immediately followed by inhibition of matriptase by hepatocyte growth factor activator inhibitor 1 (HAI-1). In the current study, we established an analogous matriptase autoactivation system in an in vitro cell-free setting and showed that a burst of matriptase activation and HAI-1-mediated inhibition spontaneously occurred in the insoluble fractions of cell homogenates and that this in vitro activation could be attenuated by a soluble suppressive factor(s) in cytosolic fractions. Immunofluorescence staining and subcellular fractionation studies revealed that matriptase activation occurred in the perinuclear regions. Solubilization of matriptase from cell homogenates by Triton X-100 or sonication of cell homogenates completely inhibited the effect, suggesting that matriptase activation requires proper lipid bilayer microenvironments, potentially allowing appropriate interactions of matriptase zymogens with HAI-1 and other components. Matriptase activation occurred in a narrow pH range (from pH 5.2 to 7.2), with a sharp increase in activation at the transition from pH 5.2 to 5.4, and could be completely suppressed by moderately increased ionic strength. Protease inhibitors only modestly affected activation, whereas 30 nM (5 μg/ml) of anti-matriptase LDL receptor domain 3 monoclonal antibodies completely blocked activation. These atypical biochemical features are consistent with a mechanism for autoactivation of matriptase that requires protein-protein interactions but not active proteases.
Diabetes induces sex-dependent changes in neuronal nitric oxide synthase dimerization and function in the rat gastric antrum
Authors: Gangula Pandu R. R. , Maner William L. , Micci Maria-Adelaide , Garfield Robert E. , Pasricha Pankaj Jay
Published: March 2007

Diabetic gastroparesis is a disorder that predominantly affects women. However, the biological basis of this sex bias remains completely unknown. In this study we tested the hypothesis that a component of this effect may be mediated by the nitrergic inhibitory system of the enteric nervous system. Age-matched male and female Sprague-Dawley rats were studied 8 or 12 wk after streptozotocin (55 mg/kg body wt ip)-induced sustained hyperglycemia and compared with controls. Solid gastric emptying (GE) studies were performed in all the groups. Changes in gastric antrum neuronal nitric oxide synthase (nNOS) mRNA and protein levels were analyzed by real-time PCR and Western immunoblotting, respectively. nNOS dimerization studies were performed using low-temperature SDS-PAGE. In vitro nitrergic relaxation (area under curve/mg tissue wt) was studied after the application of electric field stimulation in an organ bath. Changes in intragastric pressure (mmHg·s) in freely moving rats in the presence or absence of NG-nitro-l-arginine methyl ester (nitric oxide synthase inhibitor) were examined by an ambulatory telemetric method. After diabetes induction, GE is delayed in both male and female rats. However, diabetic females exhibited significant delayed GE than in diabetic males. Compared with male controls, gastric nNOS expression and nitrergic relaxation were substantially elevated in healthy female control rats, accompanied by significantly reduced intragastric pressure. The active dimeric form and dimer-to-monomer ratio of nNOSα were also higher in healthy females compared with male rats ( P < 0.05). Diabetic females, but not males, showed significant ( P < 0.05) impairment in both gastric nNOSα dimerization and nitrergic relaxation, accompanied by an increase in intragastric pressure. Our data provide evidence that females may have a greater dependency on the nitrergic mechanisms in health. Furthermore, diabetes seems to affect the nitrergic system to a greater extent in females than in males. Together, these changes may account for the greater vulnerability of females to diabetic gastric dysfunction.
Role of myokines in exercise and metabolism
Authors: Pedersen Bente Klarlund , Åkerström Thorbjörn C. A. , Nielsen Anders R. , Fischer Christian P.
Published: March 2007

During the past 20 yr, it has been well documented that exercise has a profound effect on the immune system. With the discovery that exercise provokes an increase in a number of cytokines, a possible link between skeletal muscle contractile activity and immune changes was established. For most of the last century, researchers sought a link between muscle contraction and humoral changes in the form of an “exercise factor,” which could mediate some of the exercise-induced metabolic changes in other organs such as the liver and the adipose tissue. We suggest that cytokines and other peptides that are produced, expressed, and released by muscle fibers and exert either paracrine or endocrine effects should be classified as “myokines.” Since the discovery of interleukin (IL)-6 release from contracting skeletal muscle, evidence has accumulated that supports an effect of IL-6 on metabolism. We suggested that muscle-derived IL-6 fulfils the criteria of an exercise factor and that such classes of cytokines should be named “myokines.” Interestingly, recent research demonstrates that skeletal muscles can produce and express cytokines belonging to distinctly different families. Thus skeletal muscle has the capacity to express several myokines. To date the list includes IL-6, IL-8, and IL-15, and contractile activity plays a role in regulating the expression of these cytokines in skeletal muscle. The present review focuses on muscle-derived cytokines, their regulation by exercise, and their possible roles in metabolism and skeletal muscle function and it discusses which cytokines should be classified as true myokines.
Illusions of Force Perception: The Role of Sensori-Motor Predictions, Visual Information, and Motor Errors
Authors: Diedrichsen Jörn , Verstynen Timothy , Hon Andrew , Zhang Yi , Ivry Richard B.
Published: March 2007

Internal predictions influence the perception of force. When we support an object with one hand and lift it up with the other, we expect the force to disappear from the first, postural hand. In a virtual reality system, we violated this prediction by maintaining the force on the postural hand, whereas the object was still seen and felt to be lifted by the lifting hand. In this situation, participants perceived an illusionary increase in force on the postural hand, which was, in reality, constant. We test three possible mechanisms of how force perception may be influenced in this context. First, we showed that part of the illusion can be linked to a sensorimotor prediction—the predicted sensory consequences based on an efference copy of the lifting action. The illusion is reduced when the object is lifted by an external force. We also showed that the illusion changes on a trial-by-trial basis, paralleling the fast adaptation of the postural response. Second, motor errors that arise from a miscalibrated forward model do not contribute to the illusion; the illusion was unchanged even when we prevented motor errors by supporting the postural hand. Finally, visual information signaling the removal of the object is sufficient to elicit part of the illusion. These results argue that both sensorimotor predictions and visual object information, but not motor errors, influence force perception.
Changes in Cell Viability of Wounded Fibroblasts following Laser Irradiation in Broad‐Spectrum or Infrared Light
Authors: Hawkins Denise , Abrahamse Heidi
Published: March 2007

Objective. This study aimed to establish if broad‐spectrum or infrared (IR) light in combination with laser therapy can assist phototherapy to improve the cell function of wounded cells. Background. The effect of laser light may be partly or completely reduced by broad‐spectrum light. Methods. Wounded human skin fibroblasts were irradiated with 5 J/cm2 using a helium‐neon laser, a diode laser, or an Nd:YAG laser in the dark, in the light, or in IR. Changes in cell viability were evaluated by cell morphology, ATP cell viability, LDH membrane integrity, and caspase 3/7 as an early marker of apoptosis. Results. Wounded cells exposed to 5 J/cm2 using 632.8 nm in the dark or 830 nm in the light or 1064 nm in the dark showed an increase in ATP viability, an increase in cytokine expression, and a decrease in LDH cytotoxicity indicating that the metabolic activity of the wounded cells was stimulated. Conclusion. Wounded cells irradiated in IR light showed an undesirable thermal effect that was proportional to the duration of exposure.
On the Forced Response of Harmonically and PartiallyMistuned Bladed Disks. Part I: Harmonic Mistuning
Authors: Mignolet Marc P. , Hu Wei , Jadic Ioan
Published: March 2007

This series of two papers focuses on the determination and clarification of the characteristics of the forced response of bladed disks that exhibit a mistuning pattern that is either harmonic or partial. Harmonic mistuning refers to single wavelength variations in structural properties along the disk while partial mistuning is associated with blade characteristics that are random in a specific sector and tuned elsewhere. The results of this analysis demonstrate that many features of the response of these simple systems match not only qualitatively but also quantitatively their counterparts on randomly mistuned bladed disks. Relying on these similarities, simple and reliable approximations of the localization factor and of the mean response are easily derived that exemplify the usefulness of harmonic and partial mistuning patterns. Finally, it is demonstrated both theoretically and by comparison with simulation results that the maximum amplitude of response of a disk closely follows a Weibull‐type distribution in all coupling situations, from very weak to very strong.
On the Forced Response of Harmonically and Partially MistunedBladed Disks. Part II: Partial Mistuning and Applications
Authors: Mignolet Marc P. , Hu Wei , Jadic Ioan
Published: March 2007

This series of two papers focuses on the determination and clarification of the characteristics of the forced response of bladed disks that exhibit a mistuning pattern that is either harmonic or partial. Harmonic mistuning refers to single wavelength variations in structural properties along the disk while partial mistuning is associated with blade characteristics that are random in a specific sector and tuned elsewhere. The results of this analysis demonstrate that many features of the response of these simple systems match not only qualitatively but also quantitatively their counterparts on randomly mistuned bladed disks. Relying on these similarities, simple and reliable approximations of the localization factor and of the mean response are easily derived that exemplify the usefulness of harmonic and partial mistuning patterns. Finally, it is demonstrated both theoretically and by comparison with simulation results that the maximum amplitude of response of a disk closely follows a Weibull‐type distribution in all coupling situations, from very weak to very strong.
Coupled Vibration of Unshrouded Centrifugal Compressor Impellers. Part II: Computation of Vibration Behavior
Authors: Hagelstein Dirk , Hasemann Heinrich , Rautenberg Manfred
Published: March 2007

The increased use of small gas turbines and turbochargers in different technical fields has led to the development of highly‐loaded centrifugal compressors with extremely thin blades. Due to high rotational speed and the correspondingly high centrifugal loads, the shape of the impeller hub must also be optimized. This has led to a reduction of the thickness of the impeller disc in the outlet region. The thin parts of the impeller are very sensitive and may be damaged by the excitation of dangerous blade vibrations.

Experimental investigations of coupled vibration behavior are presented in Part I of the paper. The results of these investigations were able to explain the dominance of coupling effects between the blades and the disc.

Part II of the paper presented here describes finite element (FE) code computations of the vibration behavior of the blades and the complete impeller for two different impeller types – one with radial‐ending blades and the other with backswept blades. The results are able to demonstrate the influence of coupling on dynamic behavior and the high importance of careful impeller design. The computational results were found to correspond very well with the results of the experimental investigations.
A Comparison of Performances of Turbines for Wave Power Conversion
Authors: Setoguchi T. , Takao M. , Kaneko K.
Published: March 2007

A number of self‐rectifying air turbines for wave power conversion have been proposed so far. This paper shows the comparison of the performances of all these turbines proposed for use in the near future. As a result, the impulse turbine with self‐pitch‐controlled guide vanes is found to have the best performance.
Laser Velocimeter Measurements in the Pump of an Automotive Torque Converter Part II – Effect of Pump Speed and Oil Viscosity
Authors: Flack Ronald D. , Ainley Steven B. , Brun Klaus , Whitehead Leonard
Published: March 2007

The velocity field inside a torque converter pump was studied for two separate effects: variable pump rotational speed and variable oil viscosity. Three‐dimensional velocity measurements were taken using a laser velocimeter for both the pump mid‐ and exit planes. The effect ofvariable pump rotational speed was studied by running the pump at two different speeds and holding speed ratio (pump rotational speed]turbine rotational speed) constant. Similarly, the effect of viscosity on the pump flow field was studied by varying the temperature and]or using two different viscosity oils as the working fluid in the pump. Threedimensional velocity vector plots, through‐flow contour plots, and secondary flow profiles were obtained for both pump planes and all test conditions. Results showed that torque converter mass flows increased approximately linearly with increasing pump rotational speed (and fixed speed ratio) but that the flow was not directly proportional to pump rotational speed. However, mass flows were seen to decrease as the oil viscosity was decreased with a resulting increased Reynolds number; for these conditions the high velocity regions were seen to decrease in size and low velocity regions were seen to increase in size. In the pump mid‐plane strong counter‐clockwise secondary flows and in the exit plane strong clockwise secondary flows were observed. The vorticities and slip factors were calculated from the experimental results and are presented. The torque core‐to‐shell and blade‐to‐blade torque distributions were calculated for both planes. Finally, the flow fields were seen to demonstrate similitude when Reynolds numbers were matched.
Numerical Calculation of Secondary Flow in Pump Volute and Circular Casings using 3D Viscous Flow Techniques
Authors: Majidi K. , Siekmann H. E.
Published: March 2007

The flow field in volute and circular casings interacting with a centrifugal impeller is obtained by numerical analysis. In the present study, effects of the volute and circular casings on the flow pattern have been investigated by successively combining a volute casing and a circular casing with a single centrifugal impeller. The numerical calculations are carried out with a multiple frame of reference to predict the flow field inside the entire impeller and casings. The impeller flow field is solved in a rotating frame and the flow field in the casings in a stationary frame. The static pressure and velocity in the casing and impeller, and the static pressures and secondary velocity vectors at several cross‐sectional planes of the casings are calculated. The calculations show that the curvature of the casings creates pressure gradients that cause vortices at cross‐sectional planes of the casings.
Aeroelasticity in Turbomachines: Some Aspects of the Effect of Coupling Modeling and Blade Material Changes
Authors: Moyroud François , Jacquet-Richardet Georges , Fransson Torsten H.
Published: March 2007

Two methods are generally used for the aeroelastic analysis of bladed‐disc assemblies. The first, often referred to as the energy method, assumes that the fluid does not modify invacuum structural dynamic behavior. On the other hand, the second, based on an eigenvalue approach, considers the feedback effect of the fluid on the structure. In this paper, these methods are compared using different test cases, in order to highlight the limitations of the energy method. Within this comparison, the effect of material modifications on the coupled behavior of the assembly is examined.
Investigation of Factors Influencing the StructuralVibration in Ball Bearings
Authors: Mehra Kapil , Farhang Kambiz , Datta Jayanta
Published: March 2007

Hertzian equation for elastic contact is utilized along with lumped parameter approach to obtain the equations that govern the structural vibration of ball bearings. The lumped parameter formulation is obtained by treating various elements with mass lumped at their centers of gravity and the contact as nonlinear springs with nonlinear spring rates.

Effects of preload, ball rotational speed, and damping are studied using the formulation. It is found that in the presence of preload, irrespective of the load magnitude, contact is maintained with both the inner and the outer races. Hence, responses obtained with and without the check for ball/inner race and ball/outer race interferences are identical. In addition, no appreciable change is observed in the responses when the preload value is varied from 1 to 10 N. At high speed of operation, the balls are found to maintain contact with the outer ring, whereas intermittent contact with the inner ring occurs for brief periods of time. Introduction of lubricant is found to dampen the oscillations considerably.
Numerical Simulation of Nonlinear Oil Film Forces ofTilting‐Pad Guide Bearing in Large Hydro‐unit
Authors: Ma Li-Feng , Zhang Xin-Zhi
Published: March 2007

A new numerical method is proposed for predicting the nonlinearity of tilting‐pad guide bearing oilfilm force in the rotor‐bearing system in a large hydro‐unit. Nonlinear displacement and velocity of the journal center, as well as nonlinear tilting angles and angular velocities of the pads in non‐stationary Reynolds equation are taken into account. This method is also suited for other small rotor‐bearing system. As an example, the response due to a momentarily created unbalance is Calculated. The nonlinear motion patterns of the pad and journal whirling orbit are obtained. Finally, the nonlinear orbit is compared to the linear one that could be calculated from linear stiffness and damping coefficients. It is shown that there are important differences between those two orbits and that the nonlinear simulation is more accurate.
Comparison of Various Turbulence Models in Rotating Machinery Blade‐to‐Blade Passages
Authors: Ng E. Y. K. , Tan S. T.
Published: March 2007

Numerical calculations on four blade passages are done using Q3D Navier‐Stokes solver with a simple mixing length turbulence model and two more advanced transport‐equation approaches. Mixing length is simple and cheap but crude, while more sophisticated transport approaches are more physical but more expensive. Predicted results using different turbulent models are discussed and compared with the laminar flow and well documented experimental results. Studies show that the model with more transport‐equation predicts improved result as it includes the effects of upstream history into the velocity scale.
Aeroelastic Vibrations and Stability in Cyclic Symmetric Domains
Authors: Lalanne Bernard , Touratier Maurice
Published: March 2007

This paper deals with rotating cyclic symmetric structures, immersed in light fluid flow. Firstly, general and usual cyclic symmetric properties are recovered from the Floquet
theorem for differential equations, having space periodic coefficients in conjunction with a
discrete space Fourier series development. The approach for aeroelastic problem having
cyclic symmetry is then formulated based on the twin mode approach. In addition to modal
one, rotating and stationary wave bases are introduced to derive the equilibrium equations for a non‐dissipative system subjected to aerodynamic loading. Rotating wave basis is the natural one, and it also permits consistently to prescribe the aerodynamic pressure on the boundary between the fluid and the structure. The aerodynamic load is then derived from a
harmonic analysis of the fluid flow extending to turbomachinery as in the case of aeroplane
wing. In this way, aerodynamic forces may be obtained as general as required, depending on successive time derivatives of degrees of freedom in addition to themselves. Finally, some special cases are given and stability is studied for a cyclic periodic blade assembly, even when mistuning between sectors can occur.
A Simplified Mass Conserving Algorithm for Journal Bearing under Large Dynamic Loads
Authors: Hirani H. , Athre K. , Biswas S.
Published: March 2007

A simplified mass conserving solution approach, consisting of analytical and numerical methods, for performance evaluation of dynamically loaded journal bearings is presented. The analytical technique is used to determine position and velocity of journal center for given force components. Subsequently a finite difference formulation of universal Reynolds equation is used to calculate realistic oil flow. The proposed formulation is applied for analysis of an engine main bearing. The entry and exit flow and maximum pressure in the bearing are determined over complete cycle and matched with published results obtained by numerical scheme. The suggested hybrid computational method typically takes 55 s on ICL DRS 6000, and 29 s on 150 MHz Pentium‐Pro computer.
3‐D Viscous Flow Analysis of a Mixed Flow Pump Impeller
Authors: Miner Steven M.
Published: March 2007

This paper presents the results of a study using a coarse grid to analyze the flow in the impeller of a mixed flow pump. A commercial computational fluid dynamics code (FLOTRAN) is used to solve the 3‐D Reynolds Averaged Navier Stokes equations in a rotating cylindrical coordinate system. The standard k − ε turbulence model is used. The mesh for this study uses 26,000 nodes and the model is run on a SPARCstation 20. This is in contrast to typical analyses using in excess of 100,000 nodes that are run on a super computer platform. The smaller mesh size has advantages in the design environment. Stage design parameters are, rotational speed 1185 rpm, flow coefficient φ = 0.116, head coefficient ψ = 0.094, and specific speed 2.01 (5475 US). Results for the model include circumferentially averaged results at the leading and trailing edges of the impeller, and analysis of the flow field within the impeller passage. Circumferentially averaged results include axial and tangential velocities, static pressure, and total pressure. Within the impeller passage the static pressure and velocity results are presented on surfaces from the leading edge to the trailing edge, the hub to the shroud, and the pressure surface to the suction surface. Results of this study are consistent with the expected flow characteristics of mixed flow impellers, indicating that small CFD models can be used to evaluate impeller performance in the design environment.
Studies on Pulse Jet Engine by Wind Tunnel Testing
Authors: Nakano Toshihiro , Zeutzius Michael , Miyanishi Hideo , Setoguchi Toshiaki , Kaneko Kenji
Published: March 2007

Simple design and efficiency make pulse jet engines attractive for aeronautical short‐term operation applications. An active control system extends the operating range and reduces the fuel consumption considerably so that this old technology might gain a new interest. The results on wind tunnel experiments have been reported together with the impact of combustion mode (pulse or steady) on system performance.
Rotation Effect on Jet Impingement Heat Transfer in Smooth Rectangular Channels with Film Coolant Extraction
Authors: Parsons James A. , Han Je-Chin
Published: March 2007

The effect of channel rotation on jet impingement cooling by arrays of circular jets in twin channels was studied. Impinging jet flows were in the direction of rotation in one channel and opposite to the direction of rotation in the other channel. The jets impinged normally on the smooth, heated target wall in each channel. The spent air exited the channels through extraction holes in each target wall, which eliminates cross flow on other jets. Jet rotation numbers and jet Reynolds numbers varied from 0.0 to 0.0028 and 5000 to 10,000, respectively. For the target walls with jet flow in the direction of rotation (or opposite to the direction of rotation), as rotation number increases heat transfer decreases up to 25% (or 15%) as compared to corresponding results for non‐rotating conditions. This is due to the changes in flow distribution and rotation induced Coriolis and centrifugal forces.
Sliding Mode Output Feedback Control of a Flexible Rotor Supported by Magnetic Bearings
Authors: Lewis A. S. , Sinha A. , Wang K. W.
Published: March 2007

A new sliding mode feedback algorithm is applied to control the vibration of a flexible rotor supported by magnetic bearings. It is assumed that the number of states is greater than the number of sensors. A mathematical model of the rotor]magnetic bearing system is presented in terms of partial differential equations. These equations are then discretized into a finite number of ordinary differential equations through Galerkin’s method. The sliding mode control law is designed to be robust to rotor unbalance and transient disturbances. A boundary layer is introduced around each sliding hyperplane to eliminate the chattering phenomenon. The results from numerical simulations are presented that not only corroborate the validity of the proposed controller, but also show the effects of various control parameters as a function of the angular speed of the rotor. In addition, results are presented that indicate how the current required by the magnetic bearings is affected by control parameters and the angular speed of the rotor.
The Origin of Ekman Flow in a Cavity Subject to Impulsive Rotational Motions
Authors: Yang Wen-Jei , Ohue Hiroshi , Kawashima Genshi
Published: March 2007

An experimental study is performed to disclose the origin of Ekman flow on the surfaces of a rotating drum resulting from fluid‐structure interaction after an impulsive start of motion (referred to as the spin‐up process) or an impulsive stop (the spin‐down process). Laser Doppler velocimetry (LDV) is employed to determine instantaneous distribution of both the radial and angular velocity components in the flow field inside the rotating drum. From these results, the secondary flow and the time history of the Ekman boundary layer thickness are determined. The tracer/light sheet method is also engaged to enable real‐time visualization of flow patterns. Fluid viscosity, drum size and rotational speed are varied to determine their effects on fluid‐structure interactions. Results may be applied to cavity flow in rotating machinery.
Laser‐Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan
Authors: Liou Tong-Miin , Chen Meng-Yu
Published: March 2007

Laser‐Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under‐design, and over‐design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under‐design flow rate, there are a through‐flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.
Local Heat Transfer and Pressure Drop in a Rotating Two‐Pass Ribbed Rectangular Channel
Authors: Hsieh Shou-Shing , Liao Hsiu-Cheng
Published: March 2007

The influences of rotation and uneven heating condition as well as passage aspect ratio on the local heat transfer coefficient and pressure drop in a rotating, two pass ribroughened (rib height e/DH ≈ 0.27; rib pitch p/e = 8) rectangular channel with a crosssection aspect ratio of 3 was studied for Reynolds numbers from 5000 to 25,000 and rotation numbers from 0 to 0.24. Regionally averaged Nusselt number variations along
the duct have been determined over the trailing and leading surfaces for two pass straight channels and U‐bend region. Implementing with the data from Hsieh and Liu (1996) for AR = 1 and 1.5 with p/e = 5 and e/DH = 0.17 and 0.20, passage aspect ratio effect was further examined. Furthermore, data for 180∘ U‐bend region with ribroughened turbulator on heat transfer were also measured. It was found that a complicated three‐dimensional accelerated flow and secondary flow in this U‐bend region caused higher heat transfer on both leading/trailing walls. Enhancement performance ratios are also presented and discussed. Results again indicate a slight decrease in heat transfer coefficient for an increase in passage aspect ratio as compared to those of previous studies.
Flow Field in the Turbine Rotor Passagein an Automotive Torque Converter Based on the HighFrequency Response Rotating Five‐hole ProbeMeasurement Part I: Flow Field at the Design Condition (Speed Ratio 0.6)
Authors: Liu Y. F. , Lakshminarayana B. , Burningham J.
Published: March 2007

The relative flow field in an automotive torque converter turbine was measured at three locations inside the passage (turbine 1/4 chord, mid‐chord, and 4/4 chord) using a highfrequency response rotating five‐hole‐probe. “Jet‐Wake” flow structure was found in the turbine passage. Possible flow separation region was observed at the core/suction side at the turbine 1/4 chord and near the suction side at the turbine mid‐chord. The mass averaged stagnation pressure drop is almost evenly distributed along the turbine flow path at the design condition (SR = 0.6). The pressure drop due to centrifugal and Coriolis forces is found to be appreciable. The rotary stagnation pressure distribution indicates that there are higher losses at the first half of the turbine passage than at the second half. The major reasons for these higher losses and inefficiency are possible flow separation and a mismatch between the pump exit and the turbine inlet flow field. The fuel economy of a torque converter can be improved through redesign of the core region and by properly matching the pump and the turbine. The Part I of the paper deals with the design speed ratio (SR = 0.6), and Part II deals with the off‐design condition (SR = 0.065) and the effects of speed ratio.
Flow Field in the Turbine Rotor Passage in an Automotive Torque Converter Basedon the High Frequency Response Rotating Five‐hole Probe Measurement Part II: Flow field at the off‐design condition and effects of speed ratio
Authors: Liu Y. F. , Lakshminarayana B. , Burningham J.
Published: March 2007

The flow field at the design condition was presented and interpreted in Part I. The flow field at one off‐design condition (Speed Ratio 0.065) is presented and interpreted in this
part. In addition, the hydraulic performance is analyzed by using flow measurement
results both upstream and downstream of the turbine and inside the turbine rotor
passage. It is found that at the off‐design conditions, especially the near stall condition
(Speed Ratio 0.065), most of the pressure drop occurs in the first half of turbine passage.
About 82% of the total torque is extracted between the turbine inlet and the middle
plane. In addition, the shell develops torque at nearly five times the rate of core.
Furthermore, the higher the speed ratio, the higher the total pressure drop. Loss is
maximum at the near stall condition and varies almost linearly with the speed ratios. A
compromise has to be made between the design and the off‐design performance in order
to improve the overall performance and fuel economy of torque converters.
Flow Structures Inside a Rotor‐Stator Cavity
Authors: Geis T. , Ebner J. , Kim S. , Wittig S.
Published: March 2007

This paper describes an experimental investigation initiated to determine the threedimensional flow field inside the rim seal cavity of a double‐shrouded rotor‐stator
system. Thereby, the effects caused by perturbances in the rotor wall were additionally
examined. The objective of this work is to provide detailed information about the
mechanisms that can promote elevated temperature levels in the high pressure section of
a gas turbine. Both ingested hot gas and windage heating generated at the rotor‐stator
interface can severely affect the material temperatures and thus considerably increase
the thermal load of the rotating parts.

The flow velocities were measured by means of an advanced LDV system capable of providing phase‐resolved data. The flow field was determined for two different rotorstator combinations. One of the rotor disks contained small rectangular cavities, located at the disk rim and arranged uniformly in’ the circumferential direction. These elements
are referred to as the shank cavities of the rotor disk.

The mechanical torque was measured to demonstrate the influence of these elements
on the windage power. The measurements were performed at operating conditions that
are typical for aero‐engines. It is shown that a perturbed rotor surface can raise the drag
notably. The experiments were conducted in a high speed test rig at rotational Reynolds
numbers up to Reϕ ≈ 4.2*106. The data were plotted as the dimensionless moment coefficient cM and correlated with Reϕ and the dimensionless cooling flow rate cw.
Model Based Fault Identification in Rotor Systemsby Least Squares Fitting
Authors: Markert Richard , Platz Roland , Seidler Malte
Published: March 2007

In the present paper a model based method for the on‐line identification of malfunctions in rotor systems is proposed. The fault‐induced change of the rotor system is taken into account by equivalent loads which are virtual forces and moments acting on the linear undamaged system model to generate a dynamic behaviour identical to the measured
one of the damaged system.

By comparing the equivalent loads reconstructed from current measurements to the
pre‐calculated equivalent loads resulting from fault models, the type, amount and
location of the current fault can be estimated. The identification method is based on
least squares fitting algorithms in the time domain. The quality of the fit is used to find
the probability that the identified fault is present.

The effect of measurement noise, measurement locations, number of mode shapes
taken into account etc., on the identification result and quality is studied by means of
numerical experiments. Finally, the method has also been tested successfully on a real
test rig for some typical faults.
Stabilization of Centrifuges with Instabilities Dueto Fluid‐Structure Interactions: VariousControl Approaches
Authors: Ulbrich Heinz , Cyllik Adrian , Ahaus Guido
Published: March 2007

Partially filled centrifuges exhibit unstable behavior over particular rotational speed
ranges. To remove this unstable behavior, three different control approaches are
presented which are experimentally implemented using a magnetic bearing. First, by
means of a PD‐controller the system stiffness is changed leading to a shift of the instability
region. Second, the instability region is removed by a cross coupled feed back
of the rotor vibration velocities. This cross coupling directly counteracts the fluid excitation
mechanism. Third, a disturbance observer is presented which allows to estimate
and compensate the not exactly known fluid force.
Fluid Flow and Heat Transfer in an InternalCoolant Passage
Authors: Shih Tom I.-P. , Lin Yu-Liang , Stephens Mark A.
Published: March 2007

Computations were performed to study the three‐dimensional flow and heat transfer in a U‐shaped duct of square cross section with inclined ribs on two opposite walls under rotating and non‐rotating conditions. Two extreme limits in the Reynolds number (25,000 and 350,000) were investigated. The rotation numbers investigated are 0, 0.24, and 0.039. Results show rotation and the bend to reinforce secondary flows that align with it and to retard those that do not. Rotation was found to affect significantly the flow and heat transfer in the bend even at a very high Reynolds number of 350,000 and a very low Rotation number of 0:039. When there is no rotation, the flow and heat transfer in the bend were dominated by rib‐induced secondary flows at the high Reynolds number limit and by bend‐induced pressure‐gradients at the low Reynolds number limit. Long streaks of reduced surface heat transfer occur in the bend at locations where streamlines from two contiguous secondary flows merge and then flow away from the surface. The location and size of these streaks varied markedly with Reynolds and rotation numbers.

This computational study is based on the ensemble‐averaged conservation equations of mass, momentum (compressible Navier‐Stokes), and energy. Turbulence is modelled by the low‐Reynolds shear‐stress transport (SST) model of Menter. Solutions were generated by using a cell‐centered, finite‐volume method, that is based on second‐order accurate flux‐difference splitting and a diagonalized alternating‐direction implicit scheme with local time‐stepping and V‐cycle multigrid.
Recontouring of Jet Engine Compressor Bladesby Flow Simulation
Authors: Hönen Herwart , Panten Matthias
Published: March 2007

In modern jet propulsion systems the core engine has an essential influence on the total engine performance. Especially the high pressure compressor plays an important role in this scheme. Substantial factors here are losses due to tip clearance effects and
aerodynamic airfoil quality. During flight operation the airfoils are subject to wear and
tear on the leading edge. These effects cause a shortening of the chord length and the
leading edge profiles become deformed. This results in a deterioration of the engine
efficiency performance level and a reduced stall margin.

The paper deals with the re‐contouring of the leading edges of compressor airfoils
by application of a new developed method for the profile definition. The common
procedure of smoothing out the leading edges manually on a wheel grinding machine
can not provide a defined contour nor a reproducible result of the overhaul process. In
order to achieve optimized flow conditions in the compressor blade rows, suitable
leading edge contours have to be defined for the worn airfoils. In an iterative process
the flow behavior of these redesigned profiles is checked by numerical flow simulations
and the shape of the profiles is improved. The following machining of the new defined
leading edge contours is achieved on a grinding station handled by an appropriately
programmed robot.
Effects of Leading Edge Sweep on the CavitatingCharacteristics of Inducer Pumps
Authors: Acosta Allan J. , Tsujimoto Yoshinobu , Yoshida Yoshiki , Azuma Seiji , Cooper Paul
Published: March 2007

It is well known that leading edge sweep has a favorable effect on the cavitation of turbomachines. However, the mechanisms of the improvement have not been made clear.
It has been shown that the lift and the drag on a cavitating swept single hydrofoil can be correlated fairly well based on the velocity component normal to the leading edge. In
the present paper, such correlations for swept cascades are derived and the results are examined, neglecting the full geometrical effects of the inducer rotor. It is shown that the
correlations can simulate the developments of various types of cavitation, including alternate blade cavitation, rotating cavitation, and cavitation surge. This result is based on the observation that the steady cavity length, as well as the developments
ofvarious types ofcavitation, is fairly well predicted
by the correlation.
Study on the Performance of a Sirocco Fan (Optimum Design of Blade Shape)
Authors: Adachi Tsutomu , Sugita Naohiro , Yamada Yousuke
Published: March 2007

A sirocco fan is a centrifugal fan with a forward curved blade. It is used for low pressure but has a large discharge use. In this paper, at first, nine impellers with various blade shapes were tested in the same casing. The measurements of the three‐dimensional time variant velocity at the outlet of the impeller were done using four impellers having better
performances among them. The relations between fan performance and outlet velocity were considered. The effects of the blade shape on the performance were considered.
The blade inlet and outlet angles and blade inclination angles which have the best performance were considered. The design parameters of designing a sirocco fan impeller was described.
Thermal Buoyancy Effects in RotatingNon‐Isothermal Flows
Authors: Soong C. Y.
Published: March 2007

The present paper is concerned with the non‐isothermal flow mechanisms in rotating systems with emphasis on the rotation‐induced thermal buoyancy effects stemming from the coexistence of rotational body forces and the nonuniformity of the fluid temperature field. Non‐isothermal flow in rotating ducts of radial and parallel modes and
rotating cylindrical configurations, including rotating cylinders and disk systems, are considered. Previous investigations closely related to the rotational buoyancy are surveyed.
The mechanisms of the rotation‐induced buoyancy are manifested by the author′s recent theoretical results and scaling analyses pertaining to the rotation‐induced buoyancy in rotating ducts and two‐disk systems. Finally, the open issues for future researches in this area are proposed.
An Experimental Study on the Fluid Forces Induced by Rotor‐Stator Interaction in a Centrifugal Pump
Authors: Guo Shijie , Okamoto Hidenobu
Published: March 2007

The pressure fluctuations and the radial fluid forces acting on the impeller, the pressures in the volute, as well as the vibration of the shaft in a centrifugal pump were measured simultaneously, and their relationship was investigated. Experiments were done for various diffuser vanes, flow rates, and rotating speeds. It was demonstrated that both the blade‐pressure fluctuations and the volute static pressures are nonuniform circumferentially (not axisymmetrical) under off‐design operating conditions and that the two have a strong relationship. At high flow rates, the blade pressure fluctuations, induced by rotor‐stator interactions, are large in areas where the volute static pressure is low. The traveling directions of the rotating pressure waves, the whirling directions of the radial fluid forces, and the most predominant frequency components of both the fluctuations and the forces are discussed, and an equation for predicting them is introduced. It was also noted that large alternating fluid forces are not necessarily associated with large pressure fluctuations. Furthermore, when measuring the radial fluid forces in the rotating frame, other frequency components, in addition to those related to the products of the diffuser vane number and the rotating frequency, may occur due to the circumferential unevenness of the pressure fluctuations on the impeller. These components are predictable.