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Vibration of fuel bundles

Description: Several mathematical models have been proposed for calculating fuel rod responses in axial flows based on a single rod consideration. The spacing between fuel rods in liquid metal fast breeder reactors is small; hence fuel rods will interact with one another due to fluid coupling. The objective of this paper is to study the coupled vibration of fuel bundles. To account for the fluid coupling, a computer code, AMASS, is developed to calculate added mass coefficients for a group of circular cylinders based on the potential flow theory. The equations of motion for rod bundles are then derived including hydrodynamic forces, drag forces, fluid pressure, gravity effect, axial tension, and damping. Based on the equations, a method of analysis is presented to study the free and forced vibrations of rod bundles. Finally, the method is applied to a typical LMFBR fuel bundle consisting of seven rods.
Date: June 1, 1975
Creator: Chen, S.S.
Partner: UNT Libraries Government Documents Department

Flow-induced vibration and instability of some nuclear-reactor-system components. [PWR]

Description: The high-velocity coolant flowing through a reactor system component is a source of energy that can induce component vibration and instability. In fact, many reactor components have suffered from excessive vibration and/or dynamic instability. The potential for detrimental flow-induced vibration makes it necessary that design engineers give detailed considerations to the flow-induced vibration problems. Flow-induced-vibration studies have been performed in many countries. Significant progress has been made in understanding the different phenomena and development of design guidelines to avoid damaging vibration. The purpose of this paper is to present an overview of the recent progress in several selected areas, to discuss some new results and to indentify future research needs. Specifically, the following areas will be presented: examples of flow-induced-vibration problems in reactor components; excitation mechanisms and component response characteristics; instability mechanisms and stability criteria; design considerations; and future research needs.
Date: January 1, 1983
Creator: Chen, S.S.
Partner: UNT Libraries Government Documents Department

Design guide for calculating fluid damping for circular cylindrical structures. [LMFBR]

Description: Fluid damping plays an important role for structures submerged in fluid, subjected to flow, or conveying fluid. This design guide presents a summary of calculational procedures and design data for fluid damping for circular cylinders vibrating in quiescent fluid, crossflow, and parallel flow.
Date: June 1, 1983
Creator: Chen, S.S.
Partner: UNT Libraries Government Documents Department

Flow-induced vibration of circular cylindrical structures

Description: This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs. (JDB)
Date: June 1, 1985
Creator: Chen, S.S.
Partner: UNT Libraries Government Documents Department

Hydrodynamic mass

Description: Many structural components contain, or are submerged in, a fluid. The fluid moving with a vibrating structure has an important effect on the dynamics of the structure, particularly on its natural frequencies. The effect of the fluid on natural frequencies can be accounted for using the hydrodynamic mass associated with the structure. This paper provides formulas, graphs, and computer programs for calculating hydrodynamic mass.
Date: January 1, 1984
Creator: Chung, H. & Chen, S.S.
Partner: UNT Libraries Government Documents Department

Design Guide for Calculating Fluid Damping for Circular Cylindrical Structures

Description: Fluid damping plays an important role for structures submerged in fluid, subjected to flow, or conveying fluid. This design guide presents a summary of calculational procedures and design data for fluid damping for circular cylinders vibrating in quiescent fluid, crossflow, and parallel flow.
Date: June 1983
Creator: Chen, S. S.
Partner: UNT Libraries Government Documents Department

Experiment and analysis of instability of tube rows subject to liquid crossflow. [LMFBR]

Description: A tube array subjected to crossflow may become unstable by either one or both of the two basic mechanisms: velocity mechanism and displacement mechanism. The significance of these two mechanisms depends on the mass-damping parameter. The velocity mechanism is dominant for tube arrays with a low mass-damping parameter, and the displacement mechanism is dominant for tube arrays with a high mass-damping parameter. This report presents an experimental and analytical investigation of tube rows in liquid crossflow. The main objective is to verify a mathematical model and the transition between the two mechanisms at the intermediate values of mass-damping parameter. Tests of two tube rows are conducted to determine the critical flow velocity as a function of system damping. Experimental and analytical results are found to be in good agreement.
Date: September 1, 1981
Creator: Chen, S.S. & Jendrzejczyk, J.A.
Partner: UNT Libraries Government Documents Department

Fluid forces on two circular cylinders in crossflow

Description: Fluid excitation forces are measured in a water loop for two circular cylinders arranged in tandem and normal to flow. The Strouhal number and fluctuating drag and lift coefficients for both cylinders are presented for various spacings and incoming flow conditions. The results show the effects of Reynolds number, pitch ratio, and upstream turbulence on the fluid excitation forces.
Date: January 1, 1986
Creator: Jendrzejczyk, J.A. & Chen, S.S.
Partner: UNT Libraries Government Documents Department

Fluid forces on two circular cylinders in crossflow

Description: Fluid excitation forces are measured in a water loop for two circular cylinders arranged in tandem and normal to flow. The Strouhal number and fluctuating drag and lift coefficients for both cylinders are presented for various spacings and incoming flow conditions. Results show the effects of Reynolds number, pitch ratio, and upstream turbulence on the fluid excitation forces.
Date: June 1, 1985
Creator: Jendrzejczyk, J.A. & Chen, S.S.
Partner: UNT Libraries Government Documents Department

Instability characteristics of fluidelastic instability of tube rows in crossflow

Description: An experimental study is reported to investigate the jump phenomenon in critical flow velocities for tube rows with different pitch-to-diameter ratios and the excited and intrinsic instabilities for a tube row with a pitch-to-diameter ratio of 1.75. The experimental data provide additional insights into the instability phenomena of tube arrays in crossflow. 9 refs., 10 figs.
Date: April 1, 1986
Creator: Chen, S.S. & Jendrzejczyk, J.A.
Partner: UNT Libraries Government Documents Department

Dynamic tube/support interaction in heat exchanger tubes

Description: The supports for heat exchanger tubes are usually plates with drilled holes; other types of supports also have been used. To facilitate manufacture and to allow for thermal expansion of the tubes, small clearances are used between tubes and tube supports. The dynamics of tube/support interaction in heat exchangers is fairly complicated. Understanding tube dynamics and its effects is important for heat exchangers. This paper summarizes the current state of the art on this subject and to identify future research needs. Specifically, the following topics are discussed: dynamics of loosely supported tubes, tube/support gap dynamics, tube response in flow, tube damage and wear, design considerations, and future research needs. 55 refs., 1 fig.
Date: January 1, 1991
Creator: Chen, S.S.
Partner: UNT Libraries Government Documents Department

Flow-induced vibration of a curved tube array subject to liquid cross flow

Description: This paper presents the results of tests of a curved-tube array in air, in stationary water, and in flowing fluid. A curved-tube array can be subjected to fluidelastic instability which is similar to that in a straight-tube array. However, in a curved-tube array, tube natural frequencies are different in two directions and there are frequency variations among different tube rows; the critical-flow velocity and instability mode are not the same as those of the corresponding straight-tube array. Based on the experimental data, a mathematical consideration, it can be concluded that some of the instability modes will not occur in a curved-tube array; therefore, the critical-flow velocity established for straight-tube arrays can be considered as a conservative estimate for a corresponding curved-tube array.
Date: January 1, 1981
Creator: Jendrzejczyk, J.A. & Chen, S.S.
Partner: UNT Libraries Government Documents Department

Stability of tube rows in crossflow. [LMFBR]

Description: A mathematical model for the instability of tube rows subjected to crossflow is examined. The theoretical model, based on the fluid-force data for a pitch-to-diameter ratio of 1.33, provides additional insight into the instability phenomenon. Tests are also conducted for three sets of tube rows. The effects of mass ratio, tube pitch, damping, detuning and finned tubes are investigated. Theoretical results and experimental data are in good agreement.
Date: October 1, 1982
Creator: Chen, S.S. & Jendrzejczyk, J.A.
Partner: UNT Libraries Government Documents Department

TENTATIVE DESIGN GUIDE FOR CALCULATING THE VIBRATION RESPONSE OF FLEXIBLE CYLINDRICAL ELEMENTS IN AXIAL FLOW.

Description: Many reactor and plant equipment components, such as fuel pins, control rods, and heat exchanger tubes, are long, slender, beam-like members which are exposed to nominally axial coolant flow. The flowing coolant represents a source of energy which can induce vibratory motion of these components. This design guide presents a relationship for calculating the root-mean-square (rms) displacement of a flexible rod or tube in axial flow. The relationship is based on the results of a parameter study and is valid for components that can be approximated as beams with either simply-supported or fixed-fixed ends. It is given in terms of beam natural frequency, damping factor, and intensity of the mean-square spectral density of the pressure field in the low-frequency range; all three are functions of mean axial flow velocity. Empirical expressions are developed for damping factor and intensity of the mean-square pressure spectrum. With these, an empirical equation for rms displacement is written which is in terms of known quantities and, therefore, provides a tool which can be used by designers. Since the equation is based on experiments involving a smooth rod in flow with minimal entrance effects, the predicted displacements should be interpreted and used with care. They are not conservative and, at best, will represent the minimum response to be expected. (auth)
Date: January 1, 1971
Creator: Wambsganss, M.W. & Chen, S.S.
Partner: UNT Libraries Government Documents Department

Vibration and stability of a group of tubes in crossflow

Description: This paper presents an unsteady flow theory for flow-induced vibration and instability of tube arrays in crossflow. It includes measurements of motion-dependent fluid forces, mathematical model, and experiments on nonlinear response of tube arrays. The unsteady flow theory can be used to provide answers to complex vibration problems in steam generators.
Date: December 31, 1995
Creator: Chen, S.S. & Cai, Y.
Partner: UNT Libraries Government Documents Department

A review of dynamic characteristics of magnetically levitated vehicle systems

Description: The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, while vehicle stability is an important safety-related element. To design a guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore, the trade-off between guideway smoothness and levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. This report, which reviews various aspects of the dynamic characteristics, experiments and analysis, and design guidelines for maglev systems, discusses vehicle stability, motion dependent magnetic force components, guideway characteristics, vehicle/ guideway interaction, ride quality, suspension control laws, aerodynamic loads and other excitations, and research needs.
Date: November 1, 1995
Creator: Cai, Y. & Chen, S.S.
Partner: UNT Libraries Government Documents Department

Nonlinear dynamics of a stack/cable system subjected to vortex-induced vibration

Description: A model of a stack/wire system, wind-induced vibration of the stack based on an unsteady-flow theory, and nonlinear dynamics of the stack`s heavy elastic suspended cables was developed in this study. The response characteristics of the stack and cables are presented for different conditions. The dominant excitation mechanisms are lock-in resonance of the stack by vortex shedding and parametric resonance of suspended cables by stack motion at their support ends.
Date: December 31, 1995
Creator: Cai, Y. & Chen, S.S.
Partner: UNT Libraries Government Documents Department