bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of a Closed-Tube Aerosyphon With Large Length-Diameter
Ratios
Authors: Lock G. S. H. , Kirchner J. D.
Published: November 2009

The paper reports an experimental investigation of heat transfer in the closed-tube aerosyphon (aerated-thermosyphon) for a range of conditions representative of northern field applications. In particular, attention is focused on the effect of using tubes with heated lengths not only greater than the cooled lengths, but very much greater than the tube diameter. Using three heated sections and one cooled section, the geometry of the device has been varied systematically with 10 < LH/d < 50 and 1 < LH/LC < 20. For any given geometry, the effect of air bubbling rate has been studied in the range of 0 < V˙ < 5 × 10−5 m3/S. Using these ranges it has been possible to make comparisons with other thermosyphon and aerosyphon data. The results indicate that heat transfer coefficients are reduced by increasing either length-diameter ratio or heated-cooled length ratio. They also reveal that, in general terms, the aerosyphon is almost an order-of-magnitude more effective than the single-phase thermosyphon. Some obervations on the flow regimes are offered, and an empirical correlation is presented.
Evaluation of Occupant Accelerations in Lifeboats
Authors: Nelson J. K. , Hirsch T. J. , Phillips N. S.
Published: November 2009

During the certification of lifeboats for use as a lifesaving appliance, certain impact tests are required to evaluate the strength of the system and the occupant’s exposure to accelerations. The purpose of this paper is to present a rational procedure to infer the potential for these impact accelerations to cause injury to the occupants of conventional and free-fall lifeboats.
Vortex-Shedding Response of Long Cylindrical Structures in Shear Flow
Authors: Wang E. , Whitney A. K. , Nikkel K. G.
Published: November 2009

The response of cylindrical structures to vortex shedding in a vertically sheared cross flow is analyzed. In contrast to the uniform cross-flow case, shear flow can excite more than one modal frequency at a time. Thus, the net response of the structure is a superposition of several vibration modes. The amplitude of each mode is determined by a balance between energy fed into the structure over a “locked-on” region of the structure and energy dissipated by fluid damping over the remainder of the structure. A solution method based on random vibration analysis is developed that uses an empirically derived lift coefficient and correlation length models. The technique is capable of handling both uniform and sheared (depth-varying) current profiles. Good quantitative agreement is found between the present method and the very limited field data available for shear flows, although it is concluded that the shear conditions in the tests were not sufficiently strong to validate the theory conclusively. The results show how using uniform-flow approximations to treat shear flow cases can significantly overpredict vibration amplitudes caused by vortex shedding.
Natural Frequencies and Critical Buckling Loads of Marine Risers
Authors: Kim Y. C.
Published: November 2009

Natural frequencies, mode shapes and critical buckling loads of marine risers simply supported at both ends are given in closed form by using the WKB method. These solutions allow variable cross section, bending rigidity, tension and mass distribution along the riser length. Furthermore, a simple procedure to predict natural frequencies for other boundary conditions is described. Some special forms of these closed-form solutions are compared with existing solutions in the literature.
Axial, Bending and Torsional Loading of a Strand With Friction
Authors: LeClair R. A. , Costello G. A.
Published: November 2009

A theory is presented which will predict the stresses in a single lay strand subjected to axial, bending and torsional loading when friction is present. Similar to the solution for the axial loading of a strand, the curvatures and twist of the wires are assumed. The loads, required to hold the wires in equilibrium, are obtained from a solution of the six nonlinear equations of equilibrium of a thin wire.
Ice Forces due to Changes in Water Level and Adfreeze Bond Strength Between Sea Ice and Various Materials
Authors: Nakazawa N. , Saeki H. , Ono T. , Takeuchi T. , Kanie S.
Published: November 2009

In cold regions, changes in water level can induce vertical forces on offshore structures (such as caisson and tower types) when sea ice cover to structure adfreeze bonding is present. This paper summarized the theoretical analyses of vertical ice forces as well as the results of experiments which identified the parameters required when estimating sea ice adfreeze bond strength. 1) Vertical Ice Forces. The authors have proposed a method of calculation that estimates the vertical ice forces taking the following into account: bending failure of the ice cover and adfreeze bond failure (shear induced). Calculation of vertical ice forces by this method requires the following information: bending strength of ice. Young’s modulus of ice, Poisson’s ratio of ice, and adfreeze bond strength to various materials. 2) Adfreeze Bond Strength of Sea Ice. The authors have been conducting, for 6 yr, adfreeze bond strength experiments between sea ice and various common construction materials for offshore structures such as concrete and steel. The following conclusions have been drawn from this study: (i) under certain conditions, the adfreeze bond strength of sea ice greatly depends on the surface roughness of construction materials; (ii) adfreeze bond strength increases with decreasing sea ice temperature; (iii) adfreeze bond strength decreases, approaching a constant, with increasing structure diameter; (iv) adfreeze bond strength increases, approaching a constant, with increasing ice thickness; (v) adfreeze bond strength is not greatly affected by push out velocity and stress rate.
Analysis and Prediction of Short-Term Ice Drift
Authors: McPhee M. G.
Published: November 2009

Techniques for kinematic analysis and dynamic, “free-drift” ice modeling are described and applied to interpretation of ice-drift data from recent marginal ice zone (MIZ) experiments. Kinematic description is based on a complex demodulation algorithm that separates inertial and tidal components from lower frequency, “synoptic” drift. Complex demodulation produces the time series of phasors (complex numbers describing phase and amplitude of the oscillating components), useful for separating the physical processes active in the upper ocean/ice system. Free-drift ice motion modeling utilizes a similarity theory for planetary-boundary-layer dynamics that includes the effect of buoyancy, both from rapid melting at the ice/ocean interface, and/or from a pre-existing density gradient (pycnocline) within the boundary layer. Two examples are considered: one in which a band of ice in the Bering Sea drifted rapidly away from the rest of the pack when it encountered warm water at the ice edge; and a second in which drift in the Greenland Sea was apparently affected by both a shallow pycnocline and a period of rapid melt.
Three-Dimensional Analysis of Ice Sheet Indentation: Limit Analysis Solutions
Authors: Karr D. G. , Watson J. C. , HooFatt M.
Published: November 2009

A method is presented for determining the collapse pressures of an ice sheet subjected to a uniformly distributed edge load by applying the upper-bound theorem of limit analysis. The ice sheet is idealized as a semi-infinite layer of elastic-perfectly plastic material. A quadratic anisotropic yield criterion is used to calculate the indentation pressures. The ice sheet consists of columnar ice and is assumed isotropic in the plane of the ice sheet. Upper-bound solutions are found by optimizing a three-dimensional discontinuous velocity field representing an assumed collapse pattern of the ice sheet. Solutions are based on various ratios of indentor width to ice thickness, thereby providing an envelope of indentation pressures over a range of aspect ratios, from conditions of plane strain to plane stress. Solutions are then compared with corresponding two and three-dimensional lower-bound analyses.
A Parametric Study of Fracture Toughness of Fibrous Composite
Materials
Authors: Poe C. C.
Published: November 2009

Impacts to fibrous composite laminates by objects with low velocities can break fibers giving cracklike damage. The damage may not extend completely through a thick laminate. The tension strength of these damaged laminates is reduced much as is that of cracked metals. The fracture toughness depends on fiber and matrix properties, fiber orientations, and stacking sequence. Accordingly, a parametric study was made to determine how fiber and matrix properties and fiber orientations affect fracture toughness and notch sensitivity. The values of fracture toughness were predicted from the elastic constants of the laminate and the failing strain of the fibers using a general fracture toughness parameter developed previously. For a variety of laminates, values of fracture toughness from tests of center-cracked specimens and values of residual strength from tests of thick laminates with surface cracks were compared to the predictions to give credibility to the study. In contrast to the usual behavior of metals, it is shown that both ultimate tensile strength and fracture toughness of composites can be increased without increasing notch sensitivity, and that laminates with surface cracks can fail in two stages, giving some degree of redundancy.
Fatigue Fracture Mechanics Modeling and Structural Integrity
Assessment of Offshore Welded Tubular Joints
Authors: Kam J. C. P. , Topp D. A. , Dover W. D.
Published: November 2009

Evaluation of the structural integrity of offshore structures requires information on the reliability of nondestructive testing, the accuracy of fatigue crack growth modeling and other data. The University College London Underwater NDE Centre has been set up to provide information on the effectiveness and reliability of different nondestructive testing methods. To achieve this aim, a large library of cracked specimens will be assembled. In the preliminary phase of producing this library, a series of large-scale welded tubular joints were fatigue tested and the crack growth was fully monitored with the ACPD technique. This paper will describe briefly the background to the crack library and present the data obtained from fatigue tests. It will also describe a new model for fatigue crack growth prediction in tubular joints using fracture mechanics. This model allows the prediction of the size effect noted previously in the stress/life curves for tubular joints.
Optimum Waterline Geometry for Deepwater Platforms
Authors: Hanna S. Y.
Published: November 2009

The dynamic behavior of deepwater platforms can be improved by maximizing wave force cancellation at their natural frequencies of interest. This can be achieved by optimizing both the platform waterline geometry, and the structural dynamic characteristics. This study outlines a simplified procedure by which different water-line geometries for deepwater structures can be evaluated. This procedure considers effect of wave directionality. Comparison between different waterline geometries is performed. Results are presented for four, six, eight, sixteen-column, or leg, configurations, as well as for columns (or legs) located in Triangle, Pentagon, and Hexagon configurations. For each configuration, reduction in the external loading as a function of frequency is quantified. Procedures and results presented in this paper can be easily used in selecting optimum platform waterline geometry, leg spacings, and conductor locations in early design stages.
The Dynamics of Towed Arrays
Authors: Triantafyllou G. S. , Chryssostomidis C.
Published: November 2009

A procedure for calculating the response of an array to a harmonic excitation applied at the upstream end is presented. The fluid forces on the array are modeled following the slender-body approximation and the cross-flow principle. An equivalent linear damping is used to replace the quadratic drag due to cross-flow separation. The equivalent linear damping is determined using an iterative procedure. Numerical and asymptotic solutions are derived, and the response of a typical long array is calculated. It is found that, when the separation drag is included, the array exhibits the behavior of an over-damped system, responding only to low-frequency excitations.
Fracture of Multi-Year Sea Ice Under Triaxial Stresses: Apparatus Description and Preliminary Results
Authors: Sammonds P. R. , Murrell S. A. F. , Rist M. A.
Published: November 2009

The forces that arctic sea ice can exert on offshore structures are strongly influenced by ice fracture. Fracture of multi-year sea ice has been studied in the laboratory under triaxial compression using a new triaxial mechanical testing cell for ice. A description of this apparatus is given, which enables the confined brittle behavior of ice to be investigated at temperatures down to −90°C and at strain rates up to 10−2/s under closed-loop constant displacement rate control. Preliminary results for the fracture of multi-year sea ice under confined conditions at −10°C are presented.
Spanwise Mixing in Multistage Axial Flow Compressors: Part I—Experimental Investigation
Authors: Gallimore S. J. , Cumpsty N. A.
Published: November 2009

Spanwise mixing has been shown to be an essential feature of multistage compressor aerodynamics. The cause of spanwise mixing in multistage axial flow compressors has been investigated directly by using an ethylene tracer gas technique in two low-speed, four-stage machines. The results show that the dominant mechanism is that of turbulent type diffusion and not the radial convection of flow properties as has been previously suggested. The mixing was also found to be substantially uniform in magnitude all the way across the span with levels similar to those found in two-dimensional turbulent wakes.
The “Axi-Fuge”—A Novel Compressor
Authors: Wiggins J. O.
Published: November 2009

Modifying a simple-cycle gas turbine to include heat exchangers can improve its thermal efficiency significantly (as much as 20 percent). Advanced regenerative and intercooled regenerative gas turbines for marine application have recently been the subject of numerous studies, most of which have shown that lower fuel consumption can be achieved by adding heat exchangers to existing simple-cycle gas turbines. Additional improvements in thermal efficiency are available by increasing the efficiency of the turbomachinery itself, particularly that of the gas turbine’s air compressor. Studies by Caterpillar Tractor Company and Solar Turbines Incorporated on a recuperated, variable-geometry gas turbine indicate an additional 8 to 10 percent improvement in thermal efficiency is possible when an improved higher efficiency compressor is included in the gas turbine modification. During these studies a novel compressor, the Axi-Fuge, was devised. This paper discusses the Axi-Fuge concept, its origin, design criteria and approach, and some test results.
Influence of Free-Stream Turbulence and Blade Pressure Gradient on Boundary Layer and Loss Behavior of Turbine Cascades
Authors: Hoheisel H. , Kiock R. , Lichtfuss H. J. , Fottner L.
Published: November 2009

The optimization of the blade surface velocity distribution is promising for a reduction of turbine cascade losses. Theoretical and experimental investigations on three turbine cascades with the same blade loading show the important influence of the blade pressure gradient and the free-stream turbulence on the loss behavior. The results presented demonstrate that it is the boundary layer transition behavior that determines the losses on turbine cascades. An enormous effort in measuring technique is required in order to define the location of transition from cascade experiments very accurately.
Effects of Slotted Hub and Casing Treatments on Compressor Endwall Flow Fields
Authors: Johnson M. C. , Greitzer E. M.
Published: November 2009

An experimental investigation was carried out to examine the influence of a rotating slotted hub treatment on a compressor stator passage endwall. Detailed mapping of the three-dimensional unsteady velocity field near the hub was done for a smooth hub and a hub having axial skewed slots. With the smooth wall, the velocity measurements indicate that a large region of blockage occurs near the rear of the blade passage. This blockage is seen to be associated with the hub endwall rather than either the suction surface or the pressure surface of the blade. With axial skewed slots, the blockage is markedly decreased, the stalling flow coefficient is reduced, and the peak pressure rise greatly increased. Due to the axial (rear-to-front) flow in the slots, there is a region of fluid removal (from the endwall) near the rear of the passage and a strong fluid injection, or jet, near the front. The data appear to show that this flow removal is an important part of the effect on stall margin found with hub and casing treatment. Furthermore, the data indicate that it is the (dissipation of the) high velocities in the jet that is the prime source of the efficiency reduction associated with this treatment.
Laser Measurements of Fly Ash Rebound Parameters for Use in Trajectory Calculations
Authors: Tabakoff W. , Malak M. F.
Published: November 2009

This paper describes an experimental method used to find particle restitution coefficients. The equations that govern the motion of solid particles suspended by a compressible gas flow through a turbomachine depend on the restitution coefficients. Analysis of the data obtained by a laser-Doppler velocimeter (LDV) system of the collision phenomenon gives the restitution ratios as a function of the incidence angle. From these ratios, the particle velocity components after collision are computed and used as the initial conditions to the solution of the governing equations of motion for particle trajectories. The erosion of metals impacted by small dust particles can be calculated by knowing the restitution coefficients. The alloy used in this investigation was 410 stainless steel.
Effect of Geometry on the Performance of Radial Vaneless Diffusers
Authors: Zhu Yingkang , Sjolander S. A.
Published: November 2009

The paper presents measurements of the steady aerodynamic characteristics of a series of five radial vaneless diffusers with walls varying from mildly divergent to strongly convergent. The static pressure recovery was determined and the flow was traversed at the inlet and the outlet of the diffuser for a broad range of flow rates in each case. It was found that wall convergence results in a negative (stabilizing) slope in the pressure rise curve for the diffuser. Furthermore, at high flow rates convergence was found to reduce the pressure recovery far less than one would expect and at intermediate flow rates convergence actually improved the pressure recovery. The better-than-expected performance is thought to be closely related to the observed improvement in the flow uniformity at the diffuser outlet when convergent walls are used.
Film Cooling of a Turbine Blade With Injection Through Two Rows of Holes in the Near-Endwall Region
Authors: Goldstein R. J. , Chen P. H.
Published: November 2009

Measurements of film cooling on a simulated turbine blade are conducted using a mass transfer technique. Under the influence of the endwall, dramatic changes of film cooling performance occur on the convex surface of the blade as compared to the region where the flow is two dimensional. The result is a triangular region, where coolant is swept away from the surface by the three-dimensional vortex-driven flow present between adjacent blades. In order to predict the area of this unprotected region, the influences of several parameters including density ratio, blowing rate, and number of rows of injection holes are studied. The presence of the endwall affects the film cooling performance on the concave surface only slightly.
A Review of Staggered Array Pin Fin Heat Transfer for Turbine Cooling Applications
Authors: Armstrong J. , Winstanley D.
Published: November 2009

A review of heat transfer and flow friction data for staggered arrays of pin fins in turbine cooling applications is presented. This review presents discussions on local-and array-averaged heat transfer, the effects of different geometric parameters such as pin height and pin spacing on heat transfer and flow friction, and the effect of the accelerating flow in converging pin fin channels. A review of current heat transfer correlations is also presented with recommendations for correlating parameter limits and correlation accuracy. The correlations currently available for friction factor are reviewed, with an attempt to account for the effects of the converging channels.
Prediction of Compressor Cascade Performance Using a Navier–Stokes Technique
Authors: Davis R. L. , Hobbs D. E. , Weingold H. D.
Published: November 2009

An explicit, time marching, multiple-grid Navier–Stokes technique is demonstrated for the prediction of quasi-three-dimensional turbomachinery compressor cascade performance over the entire incidence range. A numerical investigation has been performed in which the present Navier–Stokes procedure was used to analyze a series of compressor cascade viscous flows for which corresponding experimental data are available. Results from these calculations show that the current viscous flow procedure is capable of predicting cascade profile loss and airfoil pressure distributions with high accuracy. The results from this numerical investigation in the form of comparisons between the predicted profile loss, exit gas angle, and pressure distributions with experimental data are presented in this paper. Results from a grid refinement study are also shown to demonstrate that the Navier–Stokes solutions are grid independent.
Free-Stream Turbulence From a Circular Wall Jet on a Flat Plate Heat Transfer and Boundary Layer Flow
Authors: MacMullin R. , Elrod W. , Rivir R.
Published: November 2009

The effects of the longitudinal turbulence intensity parameter of free-stream turbulence (FST) on heat transfer were studied using the aggressive flow characteristics of a circular tangential wall jet over a constant heat flux surface. Profile measurements of velocity, temperature, integral length scale, and spectra were obtained at downstream locations (2 to 20 x/D) and turbulence intensities (7 to 18 percent). The results indicated that the Stanton number (St) and friction factor (Cf) increased with increasing turbulence intensity. The Reynolds analogy factor (2St/Cf) increased up to turbulence intensities of 12 percent, then became constant, and decreased after 15 percent. This factor was also found to be dependent on the Reynolds number (Rex) and plate configuration. The influence of length scale, as found by previous researchers, was inconclusive at the conditions tested.
Wake–Boundary Layer Interactions in an Axial Flow Turbine Rotor at Off-Design Conditions
Authors: Hodson H. P. , Addison J. S.
Published: November 2009

A series of experimental investigations has been undertaken in a single-stage low-speed turbine. The measurements involved rotor blade surface flow visualization, surface-mounted hot-film anemometry, and exit pitot traverses. The effects of varying the flow coefficient and Reynolds number upon the performance of the rotor blade at midspan are described. At the design flow coefficient (φ = 0.495), the rotor pressure surface flow may be regarded as laminar, while on the suction surface, laminar flow gives way to unsteady stator wake-induced transition and then to turbulent flow. Over the range of Reynolds numbers investigated (1.8×105–3.3×105), the rotor midspan performance is dominated by the suction surface transition process; suction surface separation is prevented and the rotor midspan loss coefficient remains approximately constant throughout the range. At positive incidence, suction surface leading edge separation and transition are caused by a velocity overspeed. Reattachment occurs as the flow begins to accelerate toward the throat. The loss associated with the separation becomes significant with increasing incidence. At negative incidence, a velocity overspeed causes leading edge separation of the pressure side boundary layers. Reattachment generally occurs without full transition. The suction surface flow is virtually unaffected. Therefore, the rotor midspan profile loss remains unchanged from the zero incidence value until pressure side stall occurs.
Effects of Shock Waves on Aerodynamic Instability of Annular Cascade Oscillation in a Transonic Flow
Authors: Kobayashi H.
Published: November 2009

The effects of shock waves on the aerodynamic instability of annular cascade oscillation were examined for rows of both turbine and compressor blades, using a controlled-oscillating annular cascade test facility and a method for accurately measuring time-variant pressures on blade surfaces. The nature of the effects and blade surface extent affected by shock waves were clarified over a wide range of Mach number, reduced frequency, and interblade phase angle. Significant unsteady aerodynamic forces were found generated by shock wave movement, which markedly affected the occurrence of compressor cascade flutter as well as turbine cascade flutter. For the turbine cascade, the interblade phase angle significantly controlled the effect of force, while for the compressor cascade the reduced frequency controlled it. The chordwise extent of blade surface affected by shock movement was estimated to be approximately 6 percent chord length.
Endwall Flow/Loss Mechanisms in a Linear Turbine Cascade With Blade Tip Clearance
Authors: Yamamoto A.
Published: November 2009

This paper discusses the mechanisms of three-dimensional flows and of the associated losses occurring near the tip endwall region of a linear turbine cascade with tip clearance. The clearance gap sizes and the cascade incidences were chosen as the most important variables affecting the mechanisms. Flows close to the endwall and inside the clearance were surveyed in great detail using a micro five-hole pitot tube of 0.6 mm head size. The results gave very detailed information on the mechanisms, such as leakage flow vectors and pressure distributions throughout the clearance. Interaction of leakage flow with the endwall flow and their associated separation lines, effects of gap size and inlet flow angle on loss generation, and skewness of the three-dimensional endwall flows are also discussed.
Stability of a Laminar Boundary Layer Flowing Along a Concave Surface
Authors: Finnis M. V. , Brown A.
Published: November 2009

Go¨rtler instability for incompressible laminar boundary-layer flows over constant curvature concave surfaces is considered. The full linearized disturbance equations are solved by the Galerkin method using Chebyshev polynomials to represent the disturbance functions. Stability curves relating Go¨rtler number, wave number, and vortex amplification for a Blasius mean flow are presented. The effect of streamwise pressure variation is investigated using the Falkner–Skan boundary-layer solutions for the mean flow. The importance of including the normal velocity terms for these flows is shown by their effect on the stability curves. The streamwise velocity distribution in the boundary layer on a 3-m radius of curvature plate was investigated experimentally. The results are compared with the stability curves and predicted disturbance functions.
Application of Bifurcation Theory to Axial Flow Compressor Instability
Authors: McCaughan F. E.
Published: November 2009

When a compression system becomes unstable, the mode of response depends on the operating and system parameters, such as throttle setting and B parameter. Previous numerical work on the model developed by Moore and Greitzer has provided a limited picture of the parametric effects. Applying bifurcation theory to a single-harmonic version of the model has supplied much more complete information, defining the boundaries of each mode of response in the parameter space. Specifically this is shown in a plot of B versus throttle setting, which compares well with the corresponding map produced experimentally. We stress the importance of the shape of the rotating stall characteristic. The analysis shows the qualitative difference between classic surge and deep surge.
The Influence of a Mainstream Thermal Boundary Layer on Film Effectiveness
Authors: Paxson D. E. , Mayle R. E.
Published: November 2009

A theoretical and experimental investigation on the effect of a mainstream thermal boundary layer on adiabatic film effectiveness is presented. The theory is based on a simple model which accounts for mixing between the injected flow and a mainstream flow with a viscous and thermal boundary layer. In order to apply this theory, the adiabatic film effectiveness in a flow with uniform temperature must be known either from experiments or from another theory. Experiments are described for an injection geometry having a simple two-dimensional slot. These tests were conducted with an insulated lip having a lip-diameter to slot-height ratio of 0.6. The mainstream thermal boundary layer was produced by heating the surface in contact with the mainstream flow upstream of the slot. Velocity and temperature distributions were measured at various distances downstream of the slot, along with measurements of the adiabatic wall temperatures. All tests were performed at a secondary to mainstream mass flux ratio of 0.7, but with different amounts of mainstream heating. While a comparison between theoretical and experimental results shows a discrepancy near injection, the trend is correct, and the agreement downstream is good.
Correlation and Prediction of Film Cooling From Two Rows of Holes
Authors: Jubran B. A.
Published: November 2009

This paper reports the correlation and prediction of film cooling effectiveness and the velocity field from two rows of holes inclined in the streamwise and spanwise directions. The correlation of film cooling from two rows of holes can be achieved by using a two-dimensional correlating group provided that account is taken of the momentum ratio I. The effectiveness and velocity field were predicted using the PHOENICS package. Two versions of k–ε turbulence model were explored for the film cooling predictions, which were successful at the centerlines and for low blowing rates. A nonisotropic k–ε model improved the prediction by allowing the jet to spread laterally.
Failure of Safety Valves Due to Flow-Induced Vibration
Authors: Coffman J. T. , Bernstein M. D.
Published: November 2009

Flow-induced sonic vibration in boiler safety valve nozzles led to premature valve wear and failure. The valves were mounted just downstream of a 1 1/2D pipe elbow, in contravention of guidelines suggesting an 8 to 10 diameter separation to avoid sonic vibrations. Initial modifications proved unsuccessful. A consultant then recommended replacing the cylindrical valve nozzles with reducers, which stopped the vibration. A review of flow-induced cavity vibrations is presented. In the case of the safety valves the vibration is believed due to fluid-dynamic instability of the cavity shear layer, enhanced and controlled by the resonant characteristics of the adjacent cavity. The precise feedback, or coupling, mechanism that sustains the oscillation is unknown. Possible reasons for the success of the tapered shape reducer are discussed. The limited design guidance available for safety valve placement is reviewed. Results of a safety valve vibration experience survey are presented and discussed. A two-parameter guideline for safety valve placement is suggested, involving steam velocity in addition to valve location. Possible future work on safety vibration is outlined.
Fuel Porosity and Crack Effects on Transient Overpower Analysis
Authors: Fox G. L.
Published: November 2009

Void volume within an FBR fuel pin is shown to have a substantial effect on predictions of cladding strain and lifetime for transient overpower accident analysis. This void volume is made up of the central cavity, radial and axial plane cracks, and manufactured porosity. Analytic models are described for predicting void distribution, crack closure and porosity collapse under fuel stress fields imposed by cladding. These models are incorporated in a computer code called DSTRESS. Results demonstrate the importance of void modeling in transient overpower accident analysis.
Plastic Buckling of Cylindrical Shells Under Axial Compression
Authors: Sobel L. H. , Newman S. Z.
Published: November 2009

Analytical and experimental results are presented for the axisymmetric plastic buckling of axially compressed cylinders made from strain hardening materials. Buckling loads predicted by two simple bifurcation buckling formulas (simplified analysis) and by the STAGS finite difference computer program (detailed analysis) are compared with buckling loads measured in room temperature tests on Type 304 stainless steel cylinders. The comparison shows that the loads predicted by Gerard’s bifurcation buckling formula agree well with the test results and the STAGS solution. Thus, the present results provide further confirmation that Gerard’s simple formula furnishes a reasonably good approximation to the load carrying capacity of strain hardening cylinders that buckle axisymmetrically at nominal axial stresses equal to or greater than the yield stress.
The Effect of Thickness Variations on the Behavior of Smooth Curved Pipes Under External Bending
Authors: Spence J. , Findlay G. E.
Published: November 2009

By various manufacturing techniques straight pipes with initially circular cross sections can be processed into smooth bends but usually with noncircular cross sections and with variations in thickness. These changes from the ideal are normally referred to as “ovality” and “thinning”; their influence on the subsequent behaviour of curved pipes is not yet fully understood. Here theoretical work on constant thickness circular and elliptical cross sections has been extended to cope with typical variations in thickness. The theory which is based on a classical energy approach is outlined for in-plane bending loading and is easily extended to cover out-of-plane bending. Linear elastic small displacement limitations apply. It is concluded that normally accepted values of thinning have virtually no effect on the flexibility due to bending of smooth pipe bends with or without initial ovality. Similarly, the peak meridional bending stresses were found to be insensitive to thickness variations.
Design of Radial Nozzles in Cylindrical Shells for Internal Pressure
Authors: McBride W. L. , Jacobs W. S.
Published: November 2009

A design method is presented that allows a designer to predict the maximum allowable working pressure of an opening reinforcement using an allowable stress basis. Primary application of the method is directed toward large openings as defined by ASME Section VIII, Division 1, paragraph UA-7. Recent hydrotests conducted on several production pressure vessels have demonstrated that existing paragraph UA-7 area replacement rules are inadequate in certain d/D and D/T ranges. The inadequate designs were initially indicated by leakage at a flange located close to the nozzle shell intersection. Later, another vessel hydrotest was terminated because of distortion and high readings from strain gages located at the nozzle-to-shell intersection. The proposed empirical design method produces nozzle reinforcements that should remain in the elastic stress range for internal pressure up to the Code-required hydrotest.
Surface Crack in a Clamped Circular Plate Subjected to Uniform Lateral Pressure
Authors: Abe´ H. , Ogiwara M.
Published: November 2009

The bending of a clamped circular plate containing a surface crack along its edge is discussed. An approximate method of solution, which is based on the classical plate theory, is proposed to obtain the asymptotic behavior of bending stresses along the tip of the crack. The flexural rigidity of the plate is reduced by the crack. The distribution of bending stresses is therefore changed. A plate of nonuniform thickness is introduced which has the equivalent of the flexural rigidity of the cracked plate under consideration. The bending stress intensity factor is evaluated with the aid of the equivalent plate. It is found that the stress intensity factor increases with the crack depth for shallow cracks, and it decreases when the depth exceeds a certain value.
Design, Manufacture and Safety Aspects of Forged Vessels for High-Pressure Services
Authors: Mraz G. J. , Nisbett E. G.
Published: November 2009

Steels at present included in Sections III and VIII of the ASME Boiler and Pressure Vessel Code severely limit its application for high-pressure design. An extension of the well-known AISI 4300 series low alloy steels has long been known as “Gun Steel.” These alloys, which are generally superior to AISI 4340, offer good harden-ability and toughness and have been widely used under proprietary names for pressure vessel application. The ASTM Specification A-723 was developed to cover these nickel-chromium-molybdenum alloys for pressure vessel use, and is being adopted by Section II of the ASME Boiler and Pressure Vessel Code for use in Section VIII, Division 2, and in Section III in Part NF for component supports. The rationale of the specification is discussed, and examples of the mechanical properties obtained from forgings manufactured to the specification are given. These include the results of both room and elevated temperature tension tests and Charpy V notch impact tests. New areas of applicability of the Code to forged vessels for high-pressure service using these materials are discussed. Problems of safety in operation of monobloc vessels are mentioned. Procedures for in-service inspection and determination of inspection intervals based on fracture mechanics are suggested.
An Approximate Method for the Determination of the Response Frequency of Pipe Whip
Authors: Haktanir S. A. , Tolle G. C.
Published: November 2009

This paper is concerned with the effect of fluid flow on the static and dynamic characteristics of a simply supported pipe having a hole through the pipe wall to permit a fluid flow. In this approximate analysis based on the virtual work technique, system natural frequencies and mode shapes are determined and compared to the analytical solution of the linear problem given by G. W. Housner [3] and experimental solution of H. L. Dodds, Jr., and H. L. Runyan [2]. An approximate solution satisfying the initial and boundary conditions is presented for free vibrations and for steady-state forced vibrations for the nonlinear problem. In addition, the critical fluid velocity at which the system becomes statically unstable is verified.
Fluid-Structure Interactions in Pressure-Suppression Pools: Small-Scale Experiments and Analysis
Authors: Huber P. W. , Javadi Y. B.
Published: November 2009

Experiments were conducted in a laboratory scale system to investigate fluid structure interaction effects on hydrodynamically induced boundary pressure histories. A single flexible member—a clamped circular plate—formed the base of a cylindrical water pool. Base plate thicknesses were varied to change the natural frequency of the plate pool system. The hydrodynamic transient was an air driven “pool swell” involving large liquid displacements and a complicated boundary pressure history. Pressures at various points on the pool boundary and strains on the flexible base were measured. A one-dimensional analysis of the perturbation pressure transients induced by the deflections of the flexible base is compared with the experimental results. Numerical solutions for the complete perturbed pressure histories are compared with the experiments. Ratios of the peak pressures in the flexible and rigid systems for a pressure pulse of variable duration are predicted analytically and compared with the experiments.
Design of Conical Shells Under External Loads
Authors: Jawad M. H.
Published: November 2009

The background is presented for the rules for conical shells and reducers under external pressure which were recently added to Section VIII, Division 1. A simplified method for the design of conical shells under external pressure is developed from theoretical and experimental data. The design procedure is similar to that published by ASME for cylindrical shells. Design criteria for the conical-to-cylindrical junction is also established in terms of the minimum required area and moment of inertia at the junction.
Elasto/Visco-Plastic Dynamic Response of Axisymmetrical Shells by Overlay Model
Authors: Takezono S. , Tao K. , Kanezaki K.
Published: November 2009

The numerical analysis of the elasto/visco-plastic dynamic response of the axisymmetrical shells to the time-varying load is carried out by the use of the elasto/visco-plastic overlay model which is able to express the Bauschinger effect and the strain rate dependency. Namely Perzyna’s equation is used for the constitutive relation of each layer of the overlay model and as a whole, the Bauschinger effect and the influence of viscosity in plastic range of the materials are taken into account. The basic differential equations for the shells subjected to axisymmetrical loads are derived by extending Sanders’ elastic shell theory and the equations are numerically solved by the finite difference method. As a numerical example, the pressure vessel under semi-sinusoidal pressure load with respect to time is analyzed and the results are compared with ones in the case of isotropic hardening.
An Integral Equation Approach for the Generation of Seismic Power Spectral Density Functions
Authors: Sundararajan C. , Gupta G. D.
Published: November 2009

An integral equation approach is presented for the generation of seismic power spectral density functions from specified response spectra. First, the problem of generating the response spectrum consistent power spectral density function is formulated as an integral equation with an inequality constraint, and then the equation is solved by collocation technique. An example problem is solved and the convergence of the solution is studied. The convergence study indicates that even with only about a hundred collocation points, extremely good accuracy can be achieved.
Fatigue Threshold Stress Intensity and Life Estimation of ASTM—A106B Piping Steel
Authors: Mukherjee B. , Vanderglas M. L.
Published: November 2009

Fatigue design curves extending to 1010 cycles do not exist for A106B and A155KC70 piping steels. Therefore, a fracture mechanics approach which uses the concept of threshold stress intensity factor was utilized to determine a fatigue limit extending to 1010 cycles. The effects of microstructure, composition and wet steam environment on threshold stress intensity factor were investigated. The material properties were integrated with service loading conditions to determine maximum allowable strain amplitudes in a vibrating pipe.
Relationships Between Mechanical Properties and the Extension and Arrest of Unstable Cracks in Line Pipe Steels
Authors: Shoemaker A. K.
Published: November 2009

With the increasing need for high-strength, high-pressure, large-diameter, gas-transmission lines, considerable attention has been given, in recent years, to the aspects of fracture initiation, propagation and crack arrest in line pipe. This paper presents an overview of the interrelations between material properties and design parameters that can lead to the initiation of a running fracture and the interrelationships which are necessary to arrest a running fracture. It is shown that if the pipe has ductility such that CVN/YS ≥ 0.6 ft-lb/ksi, further increases in Charpy toughness would not have a significant effect upon the critical crack size because fracture initiation becomes flow-stress dependent. Moreover, the length of a stable through-the-wall crack at operating conditions would be about two orders of magnitude longer than the current rejectable weld defect length specified by API. For “conventional” transmission-line applications CVN ≥ 0.024 σh1.5D0.5 assures arrest of running shear fractures.
An Analysis Procedure for Predicting Weld Repair Residual Stresses in Thick-Walled Vessels
Authors: Rybicki E. F. , Stonesifer R. B.
Published: November 2009

An analysis procedure for computing residual stresses due to weld repairs of heavy steel sections is described and illustrated. The model has several unique features for weld repair applications. These include a simple formula for computing temperatures in and near the repair region, a method for economically modeling the application of hundreds of weld passes typically required in repairs, and a method by which the basically two-dimensional residual stress analysis model can be inexpensively modified to incorporate some three-dimensional effects. Laboratory data for residual stresses due to the weld repair of a flat plate and computed values for a curved plate are compared. Good qualitative agreement is found. Next, the computational model is used to predict residual stresses due to a weld repair in one of the Heavy Section Steel Technology Intermediate Test Vessels. Residual stress data available for this vessel are compared with predicted values of residual stress. There is good agreement between the computed values and residual stress data for regions outside of the weld repair. A discussion of the overall agreement is given. This study demonstrates that it is economically feasible to predict the complex behavior of weld repair residual stresses.
The Enriched Element for Finite Element Analysis of Three-Dimensional Elastic Crack Problems
Authors: Hilton P. D. , Kiefer B. V.
Published: November 2009

An improved procedure for enriching three-dimensional isoparametric elements with the asymptotic crack front solution is described. Results from finite element calculations, involving these enriched elements, for the three-dimensional problems of a straight crack in plane strain and an axisymmetric penny-shaped crack which demonstrate the high degree of accuracy attainable are presented. Some finite-element solutions for through-crack and surface flaw problems are then reported showing the influence of a free surface on the variation of the stress intensity along the crack edge. Special treatments of the crack front-free surface stress intensity are implemented and the results discussed.
Acoustic Emission Testing During a Burst Test of a Thick-Walled 2-1/4 Cr-1 Mo Steel Pressure Vessel
Authors: Tsukikawa T. , Yamamoto S. , Ohshio Y. , Nakano M. , Ueyama H. , Watanabe J. , Ohnishi K. , Saikudo R. , Iwadate T.
Published: November 2009

The applicability of AET to pressure vessels made of 2 1/4 Cr-1 Mo steel was studied by an extensive program which included: 1) a hydrostatic test of a test vessel with weld discontinuities, 2) a burst test of a test vessel with precracks, and 3) an analysis of the results using a fracture mechanics approach. The results obtained clearly demonstrate that AET is a useful tool for shop and in-field inspections.
Design and Analysis of Multispan Straight Tubes for Elevated Temperature Heat Exchanger Service
Authors: Roche´ R. V. , Pai D. H.
Published: November 2009

The behavior of multispan SS304 tubes intended for elevated temperature heat exchanger service is investigated. Particular attention was paid to the ASME Code Case 1592 criteria on buckling. It was found that for the loadings and geometric parameters examined, the behavior of the multispan tubes can be characterized as strain controlled. Code Case 1592 rules were found to be conservative for all the cases investigated. A suggestion to refine the Code Case rules is also given.
Prediction of Random High-Cycle Fatigue Life of LWR Components
Authors: Shin Y. S.
Published: November 2009

This state-of-the-art review identifies and discusses the existing methods of predicting the high-cycle fatigue life, their limitations, and base-technology needs. The cycle stress-strain approach and the random vibration approach are reviewed, evaluated and discussed. It is applicable to estimating high-cycle fatigue damages of Light Water Reactor (LWR) components under the random excitation typical of flow-induced vibration.