Gate Vibration Research Articles

Flow-Induced Vibration of Long-Span Gates : Verification of Added Mass and Fluid Damping

The added mass and the fluid damping coefficient were derived theoretically in a dimensionless form in a previous study. To verify the theoretical results of the added mass and the fluid damping coefficient, the experimental results of a model test are presented in this study. A planar vertical gate undergoes free damped vibrations in air and still water. The added mass and the fluid damping coefficient are calculated from the measured frequencies and damping ratios of the damped vibrations. Consequently, it is shown that there is good agreement between the theoretical and experimental results

Shear layer behavior under a streamwise vibrating gate and its significance to gate vibration.

A flow visualization study of the shear layer movement beneath a submerged, vertical, flat-bottomed gate model with underflow and which undergoes forced streamwise vibration of fixed amplitude and frequency is presented. Computer simulation based on the flow visualization photos, coupled with measured discharge flow velocities and hydrodynamic pressure distributions on the gate, permits the estimation of the fluctuating discharge coefficient and the phase lag between the fluctuating discharge and the gate motion. The motion of the downstream portion of the shear layer is shown to correlate Well with the observed discharge fluctuations. A mechanism of energy transfer for self-excited vibrations of vertical gates positioned above a horizontal bed is identified. The excitations due to the pressure distributions along the upstream and downstream faces of the gate are shown to be approximately equal.

Flow-induced vibration of long-span gates caused by shedding vortices. (1st report. vibration criteria, level of fluid excitation and added mass).

Submerged long span gates which dam a wide river undergo violent streamwise vibrations caused by vortex shedding beneath the gate. This study presents flow-induced vibration characteristics which were obtained in a model gate test. From the measured vibration frequencies and damping ratios in air and water, respectively, the level of fluid excitation and the added mass for small amplitude gate vibrations were calculated and reduced to a dimensionless form, and thus the vibration onset criteria were obtained. In addition to the average value of the maximum amplitude of gate vibration, was measured. The results of these experiments, taken as a whole, suggest that the flow-induced vibration characteristics of the long-span gates are well predicted by the dimensionless parameters, such as the reduced gate opening height and the reduced velocity.

Flow-induced self-excited in-flowvibrations of gate plates

In-flow, or streamwise, vibrations with a relatively high frequency may occur in gates whenthere is a small flow opening between the lower gate edge and the bottom of the channel. These in-flow vibrations have been investigated in a single oscillator-type model, consisting of a vertical, 20 mm thick, stiff gate plate with flow underneath. The test programme covered gate openings between 5 and 50 mm and the natural frequency of the model gate was varied between 5·4 and 86·3 Hz (in air). Numerous cases of in-flow vibrations were recorded with a lower gate edge of rectangular cross-section. The thickness of this gate edge was 20 mm and 10 mm successively. The vibrations appeared to occur in three distinct vibration domains, each characterized by a definite range of dimensionless reduced velocity numbers. Gate openings between 0·25 and 1·75 times the gate edge thickness appeared to be sensitive to in-flow vibrations. An explanation for the occurrence of in-flow vibrations was established on the basis of pressure and flow-velocity measurements: the flow underneath the gate detaches from the leading edge and forms a free shear layer. Due to the gate movement the free shear layer takes a wavy shape which results in local flow-velocity oscillations and pressure oscillations under the gate. The formed pressure “waves” propagate under the gate bottom and on passing the trailing edge they cause pressure oscillations on a small strip of the downstream face of the gate. The gate is excited by these pressure oscillations. Gate vibration and the generated pressure waves form a closed-loop feedback system, which means self-excitation. Depending on the number of pressure wavelengths, equivalent to the gate edge thickness, the gate vibrations could be classed in one of three vibration domains. It appeared that in-flow vibrations could be prevented by bevelling the upstream face or the downstream face of the gate edge.

Flow induced vidration of long span gates. (2nd report. Added mass and fluid damping).

To study the flow-induced small-amplitude vibration of long-span gates with small gate openings which are inclined toward the downstream side, this study presents an analytical method to derive the dimensionless parameters of the added mass and fluid damping coefficients induced by fluid motion. The equation of motion of long-span gates includes the integral fluid term which describes the effects of the added mass and fluid damping. In the calulation of the integral fluid term for a periodic gate vibration, it is reduced to a superposition of the acceleration and the velocity terms. Thus, the added mass and fluid damping coefficients are derived in the form of a series summation. They are calculated numerically and the major characteristics of added mass and fluid damping are revealed and discussed. Based on the calculated fluid damping effect on the gate vibration, the tendency of long-span gates to vibrate as a result of flow-induced vibrations is discussed.

Flow induced vibration of long span gates. (3rd Report, Verification of added mass and fluid damping).

The long span gates vibrating in the streamwise direction push and draw the water in the reservoir, thus the gate is accompanied by an added mass of water. Moreover, the waves propagating in the upstream direction are formed on the free reservoir surface, thus resulting in a fluid damping effect on the vibrating gates. The added mass and fluid damping coefficient was derived theoretically in a dimensionless form in a previous study. To verify the theoretical results of the added mass and fluid damping coefficient, the experimental results of a model test are presented in this study. A planar vertical gate undergoes free damped vibrations in air and still water, respectively. The added mass and fluid damping coefficient are calculated from the measured frequencies and damping ratios of the damped vibrations. Consequently, it is shown that there is good agreement between the theoretical and experimental results.

Vertical Gate Vibrations By Galloping Or By Fluid Inertia?

Vertical Gate Vibrations By Galloping Or By Fluid Inertia?

タンディシュスライディングゲート加振による連鋳モールド内湯面制御方法の開発

Studies on fluctuation of mold bath level were carried out to obtain better surface quality of cast slabs.(1) The fluctuation occurs due to delay in the movement of slide gate caused by adhesion of solidified steel.(2) By the vibration of slide gate, its movement is improved and the fluctuation of bath level is remarkably decreased.From these results, the new technology for the automatic bath level control system was developed. A special feature of the system is the addition of a vibratory signal to the control signal of the slide gate.The system has been applied to all casters in Wakayama and Kashima Steel Works and as a result, the yield of cast slabs have been remarkably improved

Flow induced vibration of long span gates. Derivation of equation of motion.

To study the flow induced small-amplitude-vibration of long span gates under small gate openings which are inclined toward the downstream side, this study presents an analytical method to derive the hydrodynamic pressure induced by an arbitrary gate motion. In the analysis, the Rayleigh's potential theory developed for dissipative-wave radiation problems is applied to reduce the flow fluctuation phenomena to an initial-boundary value problem which can be solved by making use of mathematical techniques such as Fourier series transform, Fourier integral transform and Laplace transform. Consequently, the equation of gate motion is derived in the form of a homogeneous differential-integral equation.

AN EXPERIMENTAL STUDY ON VIBRATION PHENOMENA OF THE NEW FIXED WHEEL GATE UNDER THE HIGH HEAD DAM

A new type of fixed wheel gate has been developed for regurating gate of high head dam. Through a series of experimental and theoretical analysis, it has been clarified that the new type of gate was applicable in real gates and was proved stable in dynamic behavior against vibrations due to the fluctuating water pressure without any divergences. The stability has been evaluated both by model tests and numerical analysis. The structure has been analysed by a model subjected to the distributed loads which were measured on a model of new type gate through laboratory tests. The static loads are also measured and analysed same as dynamic loads. The results about the responces of gate vibration system by dynamic loads which are measured in model tests, show good coincidence with the measured data in field gate. Therefor the method as shown here gives good solutions for estimating the forced vibration phenomena of gate system.

Self-excited vibrations of vertical-lift gates

(1986). Self-excited vibrations of vertical-lift gates. Journal of Hydraulic Research: Vol. 24, No. 5, pp. 391-404.

Vortex-excited vibrations of underflow gates

The paper deals with the dynamic forces and oscillations of vertical-lift rectangular gates submerged in freesurface flow. In the range of low reduced velocities investigated here (VT < 5) the oscillations were found to be excited by the vortices due to the dynamic interaction between the elastic gate and the unstable shear layer underneath the gate. Spectral analysis of the excitation-force and gate-response signals permitted identification of the main characteristics of the interaction process. The main similitude parameters governing this hydroelastic phenomenon are shown to be the reduced velocity and the mass-damping coefficient. The study permits a number of general conclusions to be drawn regarding model tests on vibrating structures.

Introduction to Fluid Mechanics, 2nd Edition. By R. W. Fox and A. T. MCDONALD. Wiley, 1978. 684 pp. $19.95. Flow-induced Gate Vibrations. By P. A. KOLKMAN. Publication no. 164, Delft Hydraulics Laboratory, 1976. 225 pp. Computing Methods in Applied Sciences. Edited by R. GLOWINSKI and J. L. LIONS. Springer, 1976. 593 pp. $15.20. Symposium on Applied Mathematics dedicated to the

<b>Introduction to Fluid Mechanics, 2nd Edition.</b> By R. W. Fox and A. T. MCDONALD. Wiley, 1978. 684 pp. $19.95. <i>Flow-induced Gate Vibrations</i>. By P. A. K<scp>OLKMAN</scp>. Publication no. 164, Delft Hydraulics Laboratory, 1976. 225 pp. <i>Computing Methods in Applied Sciences</i>. Edited by R. G<scp>LOWINSKI</scp> and J. L. L<scp>IONS</scp>. Springer, 1976. 593 pp. $15.20. <i>Symposium on Applied Mathematics dedicated to the

On flow induced vibrations in hydraulic structures and their alleviation

Flow-induced vibrations are characterized as dynamic response, self-controlled and self-excited vibrations, the latter two being the principal subjects of this paper. Such classification is shown to be a helpful guide for designing against destructive vibrations. While the obvious choices of increased stiffness or additional damping may prove effective in some cases, counter-examples are presented. A change in structural geometry which modifies the flow characteristics may be the best or only avenue for eliminating vibration problems in service.The general nature of mathematical models of these phenomena is presented briefly as well as those aspects of hydro-elasticity which distinguishes it from aeroelasticity. In particular, the effects of virtual mass are emphasized.A variety of different problems are reviewed with an effort to summarize and interpret current knowledge and to provide some physical insight. Specifically treated are stability of fluid-conveying pipes, vibrations of hydraulic gates, valves, and seals, and the singing of propellor blades, guide vanes, and control surfaces. In each case, methods of alleviation are discussed.

Closure to “Flow-Induced Vibration of a Vertical-Lift Gate”

Closure to “Flow-Induced Vibration of a Vertical-Lift Gate”

Discussion of “Flow-Induced Vibration of Vertical-Lift Gate”

Discussion of “Flow-Induced Vibration of Vertical-Lift Gate”

Discussion of “Flow-Induced Vibration of Vertical-Lift Gate”

Discussion of “Flow-Induced Vibration of Vertical-Lift Gate”

Flow-Induced Vibration of Vertical-Lift Gate

The vibration of a model of a vertical-lift gate with a flat bottom and a single vertical degree-of-freedom is studied experimentally. The vibration is due to a periodic reattachment of the jet to the bottom of the gate. The exciting force and the unsteady flow pattern are correlated and the parameters of the vibration are defined. The negative damping is measured directly and is shown to be a function of flow velocity and vibration amplitude. The nonlinear response of the system is related to interactions between the exciting force and the motion of the gate.

Field Investigation and Reduction of Wicket Gate Vibration in a Francis-Type Reversible Pump/Turbine

The profiles of three wicket gates on a Francis-type reversible pump/turbine were modified in the field to reduce vibration levels in the pumping and generating modes of operation. This paper describes the modification and the field tests employed to monitor the changes in the gate torque chracteristics. Static and dynamic components of gate torque were reduced significantly.

Closure to “Spillway Gate Vibrations on Arkansas River Dams”

Closure to “Spillway Gate Vibrations on Arkansas River Dams”