Experimental Study of a Vibrating Disk Submerged in a Fluid-Filled Tank and Confined With a Nonrigid Cover

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
David Valentín ◽  
Alexandre Presas ◽  
Eduard Egusquiza ◽  
Carme Valero ◽  
Mònica Egusquiza
Keyword(s):  
Experimental Study ◽  
Theoretical Model ◽  
Dynamic Response ◽  
Natural Frequencies ◽  
Pressure Sensors ◽  
Hydraulic Turbine ◽  
Added Mass ◽  
Test Rig ◽  
Damping Behavior ◽  
Hydraulic Turbines

Determining the dynamic response of submerged and confined disklike structures is of interest in engineering applications, such as in hydraulic turbine runners. This dynamic response is heavily affected by the added mass and damping as well as the proximity of solid boundaries. These solid boundaries are normally considered as completely rigid in theoretical or numerical calculations, however, this assumption is not always valid. Some hydraulic turbines have noncompletely stiff casings, which can modify the dynamic response of the runner itself, affecting specially its natural frequencies and damping behavior. To determine the influence of noncompletely rigid nearby surfaces in the dynamic behavior of a submerged structure, an experimental test rig has been constructed. This test rig is based on a disk attached to a shaft and confined in a tank covered with two different casings with different mass and stiffness. For both covers and different disk to cover distances, natural frequencies and damping ratios of the disk have been obtained experimentally. Accelerometers installed on the disk and covers as well as pressure sensors are used for this purpose. Results obtained for all the cases are discussed in detail and compared with a simplified theoretical model.

scholarly journals Effect of Sediment Size in Hydraulic Turbine Material: A Case Study of Roshi Khola in Nepal

2013 ◽  
Vol 13 (2) ◽  
pp. 129-132
Author(s):  
Laxman Poudel
Keyword(s):  
Weight Loss ◽  
High Velocity ◽  
Hydraulic Turbine ◽  
Direct Impact ◽  
Test Rig ◽  
Reservoir Capacity ◽  
Sediment Size ◽  
Micron Size ◽  
Hydraulic Turbines

Siltation problem in Nepal is major and challenging in hydropower development. It degrades the reservoir capacity and hydraulic turbines’ efficiency. Many researches have been carried out in this field and have proven sand as major substance that erodes the turbine material, but only few researches have accounted every parameters of sand on degradation of hydraulic turbines. This paper accounts size of sediments important parameter that has direct impact on turbine material. Sediment size impact has been studied firstly by characterizing size into six layered using sieve analyzer and testing its impact using high velocity test rig at Kathmandu University. Sand samples from 20 different stations of Roshi river were collected and tested on turbine material 18Cr4Ni. It found that greater micron sizes of sediments have great impact was than relatively smaller ones. It is depicted that 300-400 micron size sediment, have highest impact with weight loss of 0.022 milligram, 212-300 micron size has 0.013 milligram weight loss, 90-212 micron size has 0.012 and below 90 micron sizes have 0.0075 milligram of weight loss. Nepal Journal of Science and Technology Vol. 13, No. 2 (2012) 129-132 DOI: http://dx.doi.org/10.3126/njst.v13i2.7725

Generalized SDOF system for dynamic analysis of concrete rectangular liquid storage tanks: effect of tank parameters on response

2010 ◽  
Vol 37 (2) ◽  
pp. 262-272 ◽  
Author(s):  
J. Z. Chen ◽  
M. R. Kianoush
Keyword(s):  
Dynamic Response ◽  
Natural Frequencies ◽  
Hydrodynamic Pressure ◽  
Characteristic Parameter ◽  
Added Mass ◽  
Tank Wall ◽  
Storage Tanks ◽  
Effective Height ◽  
Sdof System ◽  
Liquid Storage

This paper presents the results of parametric studies on the seismic response of concrete rectangular liquid storage tanks using the generalized single-degree-of-freedom (SDOF) system. The effects of height of liquid and width of tank on the dynamic response of liquid storage tanks are investigated. The liquid level varies from the empty condition to a full tank. Also, instead of the commonly used ratio of width of tank to liquid height, Lx/HL, the ratio of width of tank to full height of the tank wall, Lx/Hw, is used as a characteristic parameter of tanks to study the effect of tank size on the dynamic response. The trends of added mass of liquid, effective height, and natural frequencies for different sizes of tanks are established. The values of the added mass of liquid due to impulsive hydrodynamic pressure and the effective height in the relationship with the ratios Lx/Hw and HL/Hw are determined and can be used in the seismic design of liquid storage tanks. Since the natural frequencies of liquid-containing structures are within a band of frequencies between that of a full tank and that of an empty tank, the recommended frequency to be used in the design of the tank wall is the frequency that causes the maximum dynamic response .

An Experimental Study on the Dynamic Response of a Vertical Cantilever Pipe Conveying Fluid

1980 ◽  
Vol 102 (3) ◽  
pp. 129-135 ◽  
Author(s):  
R. Shilling ◽  
Y. K. Lou
Keyword(s):  
Experimental Study ◽  
Dynamic Response ◽  
Flow Rate ◽  
Natural Frequencies ◽  
Internal Flow ◽  
Deep Ocean ◽  
Economic Loss ◽  
System Response ◽  
Environmental Damage ◽  
Ocean Thermal Energy

Transverse vibrations of elastic pipes conveying a fluid have been observed in pipelines and heat exchangers. These fluid-induced vibrations can be a serious problem and in some incidents have caused structural failure resulting in environmental damage and economic loss. For offshore applications such as marine risers, the Ocean Thermal Energy Conversion Plant and deep ocean mining vacuums, the problem is compounded by the existence of vortex shedding, wave excitations, currents, and platform motions. An experimental study was conducted to investigate the effects of internal flow rate and the depth of immersion on the dynamic response of a vertical cantilever pipe discharging a fluid. It was found that the internal flow rate and the surrounding fluid have a significant effect on the natural frequencies of the system. Specifically it was found, that depending on the relative value of the forcing frequency, in comparison to the system natural frequencies, an increase in flow rate may not necessarily result in a larger system response. Conversely, an increase in the length of pipe immersion does not necessarily decrease the response of the system. It is also observed that with increasing flow rate, an auspicious increase in the response of the higher harmonics is noted, indicating an increase fluid coupling of the system. System natural frequencies were observed to decrease with increasing flow rate.

scholarly journals Effect of Clamping Torque on Large Deflection Static and Dynamic Response of a Cantilever Beam: An Experimental Study

2018 ◽  
Vol 15 ◽  
pp. 1-16
Author(s):  
Soumen Mondal ◽  
Sushanta Ghuku ◽  
Kashi Nath Saha
Keyword(s):  
Experimental Study ◽  
Dynamic Response ◽  
Cantilever Beam ◽  
Strain Gauge ◽  
Large Deflection ◽  
Static Load ◽  
Natural Frequencies ◽  
Dynamic Strain ◽  
Load Step ◽  
Different Thickness

The present paper reports an experimental study on the effect of finite clamping on static and dynamic characteristics of cantilever beam. The experiment is carried out with two different beams, each of which is clamped at two different locations resulting in two different geometry settings. Under each of these four settings, specimen is clamped under two different torque ratings giving rise to different finite clamping effect. Under the eight settings, coordinates of tip point under static loading are measured directly using scales and plumb at each load step; whereas, complete deflection profiles of loaded beam under each static load step are obtained through post-processing of images captured during experimentation. Such image processing is carried out manually using AutoCAD®and in-built AutoLISP®software. Strain measurements at each static load step are carried out by using strain gauge, a universal data acquisition system and the associated Catman Easy®software. To obtain loaded free vibration characteristics, loaded beam under each setting is disturbed by a rubber hammer and its dynamic response is recorded from strain gauge signal through Catman Easy®software. These dynamic strain readings of loaded beam are post-processed and FFT plots are generated in MATLAB®software and first two loaded natural frequencies of beam under each setting are obtained. Finally, effects of clamping torques on the static strain and deflection results and loaded natural frequencies for beam settings with the four different thickness to length ratios are reported in a suitable manner. The result reported may be useful as ready reference to develop a theoretical model of clamped beam like structures incorporating the effect of finite clamping.

Experimental study on the dynamic response of a water ballast type floating breakwater

2021 ◽  
Vol 233 ◽  
pp. 109012
Author(s):  
Zhiwen Yang ◽  
Xinran Ji ◽  
Mingxiao Xie ◽  
Jinzhao Li ◽  
Huaqing Zhang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Dynamic Response ◽  
Floating Breakwater

scholarly journals Experimental Study on Dynamic Combustion Characteristics in Swirl-Stabilized Combustors

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1609
Author(s):  
Donghyun Hwang ◽  
Kyubok Ahn
Keyword(s):  
Experimental Study ◽  
Heat Release ◽  
Dynamic Pressure ◽  
Combustion Instability ◽  
Flame Structure ◽  
Pressure Sensors ◽  
Necessary Condition ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Geometric Conditions

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

Numerical Prediction of Critical Cavitation Performance in Hydraulic Turbines

2003 ◽  
Author(s):  
Sadao Kurosawa ◽  
Kiyoshi Matsumoto
Keyword(s):  
Flow Model ◽  
Flow Analysis ◽  
Prediction Method ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Two Phase ◽  
Cavitation Performance ◽  
Hydraulic Turbines ◽  
Critical Cavitation ◽  
Good Agreement

In this paper, numerical method for predicting critical cavitation performance in a hydraulic turbine is presented. The prediction method is based on unsteady cavitation flow analysis to use bubble two-phase flow model. The prediction of the critical cavitation performance was carried out for the aixal hydraulic turbine and the francis turbine as a typical examples. Results compared to the experiment showed a good agreement for the volume of cavity and the performance drop off and it was recognized that this method could be used as an engineering tool of a hydraulic turbine development.

Small scale experimental study of the dynamic response of a tension leg platform wind turbine

2014 ◽  
Vol 6 (5) ◽  
pp. 053108 ◽  
Author(s):  
Anders Mandrup Hansen ◽  
Robert Laugesen ◽  
Henrik Bredmose ◽  
Robert Mikkelsen ◽  
Nikolaos Psichogios
Keyword(s):  
Experimental Study ◽  
Dynamic Response ◽  
Wind Turbine ◽  
Small Scale ◽  
Tension Leg Platform

Fluid Added Mass Effect in the Modal Response of a Pump-Turbine Impeller

2009 ◽  
Author(s):  
Eduard Egusquiza ◽  
Carme Valero ◽  
Quanwei Liang ◽  
Miguel Coussirat ◽  
Ulrich Seidel
Keyword(s):  
Natural Frequencies ◽  
Experimental Tests ◽  
Mass Effect ◽  
Added Mass ◽  
Mode Shapes ◽  
Pump Turbine ◽  
Modal Response ◽  
Surrounding Fluid ◽  
Turbine Impeller ◽  
Good Agreement

In this paper, the reduction in the natural frequencies of a pump-turbine impeller prototype when submerged in water has been investigated. The impeller, with a diameter of 2.870m belongs to a pump-turbine unit with a power of around 100MW. To analyze the influence of the added mass, both experimental tests and numerical simulations have been carried out. The experiment has been performed in air and in water. From the frequency response functions the modal characteristics such as natural frequencies and mode shapes have been obtained. A numerical simulation using FEM (Finite Elements Model) was done using the same boundary conditions as in the experiment (impeller in air and surrounded by a mass of water). The modal behaviour has also been calculated. The numerical results were compared with the available experimental results. The comparison shows a good agreement in the natural frequency values both in air and in water. The reduction in frequency due to the added mass effect of surrounding fluid has been calculated. The physics of this phenomenon due to the fluid structure interaction has been investigated from the analysis of the mode-shapes.

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