Overflow Gates

2017 ◽  
pp. 231-293
Keyword(s):  
Fluid Mechanics ◽  
Vibration Frequency ◽  
Unsolved Problem ◽  
Added Mass ◽  
Energy Sources ◽  
Flow Conditions

This chapter focusses on instabilities associated with overflowing gates -- nappe oscillations and flap gate vibrations. A detailed mapping of potential initiating and sustaining energy sources is developed to help understand the mechanism of nappe oscillations. The precise mechanism of nappe oscillations remains an unsolved problem in fluid mechanics, even though we understand the process well enough to provide effective countermeasures to prevent nappe oscillations. We do not yet have the ability to definitively predict the onset criteria for nappe oscillations nor can we predict which mode of nappe oscillations will predominate and what produces changing modes with changing flow conditions. A method of determining added mass and in-water vibration frequency of flap gates is presented at the conclusion of the chapter.

Influence of Gap Size on Added Mass for Spent Fuel Storage Rack

2018 ◽  
Author(s):  
Daogang Lu ◽  
Yu Liu ◽  
Shu Zheng
Keyword(s):  
Vibration Frequency ◽  
Input Parameter ◽  
Added Mass ◽  
Water Tank ◽  
Spent Fuel ◽  
Free Standing ◽  
Fluid Force ◽  
Spent Fuel Storage ◽  
Fuel Storage ◽  
Spent Fuel Pool

Free standing spent fuel storage racks are submerged in water contained with spent fuel pool. During a postulated earthquake, the water surrounding the racks is accelerated and the so-called fluid-structure interaction (FSI) is significantly induced between water, racks and the pool walls[1]. The added mass is an important input parameter for the dynamic structural analysis of the spent fuel storage rack under earthquake[2]. The spent fuel storage rack is different even for the same vendors. Some rack are designed as the honeycomb construction, others are designed as the end-tube-connection construction. Therefore, the added mass for those racks have to be measured for the new rack’s design. More importantly, the added mass is influenced by the layout of the rack in the spent fuel pool. In this paper, an experiment is carried out to measure the added mass by free vibration test. The measured fluid force of the rack is analyzed by Fourier analysis to derive its vibration frequency. The added mass is then evaluated by the vibration frequency in the air and water. Moreover, a two dimensional CFD model of the spent fuel rack immersed in the water tank is built. The fluid force is obtained by a transient analysis with the help of dynamics mesh method.

scholarly journals Vibration in a Multistage Centrifugal Pump under Varied Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Ling Bai ◽  
Ling Zhou ◽  
Xiaoping Jiang ◽  
Qinglong Pang ◽  
Daoxing Ye
Keyword(s):  
Centrifugal Pump ◽  
Vibration Frequency ◽  
Vibration Velocity ◽  
Major Type ◽  
Outlet Section ◽  
Flow Conditions ◽  
Technical Requirements ◽  
Mass Unbalance ◽  
Blade Passing Frequency ◽  
Multistage Centrifugal Pump

Multistage pumps are intended to improve designs with low-vibration and -noise features as the industry applications increase the technical requirements. In this frame, it becomes really important to fully understand the vibration patterns of these kinds of complex machines. In this study, a vibration test bench was established to examine the vibration and stability of a cantilever multistage centrifugal pump under different flow rates. The vibration spectrum diagrams for the inlet and outlet sections and the pump body were evaluated under varied flow conditions. Results showed the effects of operational conditions on the vibration of the cantilever multistage centrifugal pump. Vibration velocity was primarily caused by mass unbalance at the shut-off flow rate point. Under different flow conditions, the blade passing frequency (BPF) and two times the blade passing frequency (2BPF) were the main excitation frequencies. The vibration frequency of the final pump body remained at the BPF under different flow conditions due to the contact with the outlet section. The major type of vibration frequency for the inlet and outlet was high frequency.

A Theory of the Cylindrical Ejector Supersonic Propelling Nozzle

1963 ◽  
Vol 67 (625) ◽  
pp. 64-64 ◽  
Author(s):  
J. Dunham
Keyword(s):  
Fluid Mechanics ◽  
Plane Waves ◽  
Direct Proof ◽  
Stagnation Pressure ◽  
Flow Conditions ◽  
The Status ◽  
Velocity Of Propagation ◽  
Flow Quantity ◽  
Subsonic Jet

In their paper, “A Theory of the Cylindrical Ejector Supersonic Propelling Nozzle”, Pearson, Holliday and Smith analysed the conditions under which two unmixed streams of air pass together through a nozzle. Two criteria were used to determine the flow conditions at the exit, when the nozzle is choked: —(a) That the stagnation pressure in the secondary (subsonic) jet should be a minimum for a given flow quantity.(b) That the velocity of propagation of small plane waves at the exit should be zero.Either criterion, applied independently, led to the same result but, as the authors observed, neither has the status of an axiom in fluid mechanics, and a direct proof without invoking either would be preferable.

A Bio-Inspired Aircraft Design Concept

2012 ◽  
Author(s):  
Emily Fisher ◽  
Anton Bauhofer ◽  
Christine Beauchene ◽  
Brian Dress ◽  
Stephen Marshall ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Fluid Mechanics ◽  
Material Selection ◽  
Aircraft Design ◽  
Skeletal Structure ◽  
Wake Vortex ◽  
Flight Performance ◽  
Flow Conditions ◽  
Selection For ◽  
Computational Analyses

The goal of the research has been to design a robotic bird that utilizes principles of nature to optimize flight. Seagulls were the preferred model for the robot because they have a large wing span that provides a more steady flight and sheds a continuous wake vortex, creating lift on both the upstroke and down-stroke of flight [1]. Research has been done on the architecture of a seagull’s wing as well as the aerodynamic features of its comprising airfoils. The robotic wings developed will capture the architecture of the seagull wings with a variety of airfoils that improve lift and reduce drag and joints that enable bending on the upstroke in the flapping motion. A main focus of this research was to study how the seagull uses air flow to improve its flight performance. The fluid mechanics of the wing was analyzed for steady and unsteady flight using Fluent code to see how seagull adapts to different flow conditions. Using the developed robotic model of the wing attempts were made to achieve the necessary wing positioning that fully complied with that of the seagull during flight. Actuation of the wings was achieved using servo motors. Fabrication of the robotic prototype involved material selection for the fuselage, wing surface and skeletal structure. At completion of the prototyping, trials were performed using stereovision to study the complex effects of unsteady flow, and to verify the computational analyses undertaken.

Seismic Response Analysis of Pier in Deep Water with Wave Effect

2010 ◽  
Vol 163-167 ◽  
pp. 4072-4075
Author(s):  
Ling Ling Jia ◽  
Yang Han
Keyword(s):  
Fluid Mechanics ◽  
Coupling Effect ◽  
Wave Force ◽  
Added Mass ◽  
Response Analysis ◽  
Seismic Response Analysis ◽  
Coupling Equation ◽  
Wave Effect ◽  
Fem Model ◽  
Linear Algorithm

In order to study the dynamic of the pier under seismic and wave action , based on fluid mechanics principle , A FEM model and dynamic equation was established by nonlinear Morison equation. Considering both the effect of added mass of water and the coupling effect of fluid and structure, the Newmark-β method is applied to solve the coupling equation. The results are compared with the simplified linear algorithm. By the numeric analysis, the pier response is studied and analysed deeply under earthquake and wave force effect.

Mode Analysis and Study of Sunjiagou Aqueduct

2014 ◽  
Vol 912-914 ◽  
pp. 911-914
Author(s):  
Cai Ying Chen ◽  
Ke Lun Wei ◽  
Ya Fei Zhu
Keyword(s):  
Seismic Design ◽  
Vibration Frequency ◽  
Natural Vibration ◽  
Vibration Mode ◽  
Added Mass ◽  
Mode Analysis ◽  
Natural Vibration Frequency ◽  
Analysis Software ◽  
Element Analysis ◽  
The Finite Element Analysis

This paper mainly adopts the finite element analysis software ANSYS to calculate and analyze the dynamic characteristic of aqueduct structure,using added mass method to deal with interaction between water and aqueduct wall, and get the natural vibration frequency and main vibration mode of U-shaped aqueduct in different water depth. The calculation result shows that water has a small effect on the vibration mode of aqueduct structure, but has a greater influence on the natural vibration frequency of aqueduct structure; natural vibration frequency of aqueduct structure decreases with the depth deepening. The research results provide the basis for the seismic design and protection of Sunjiagou aqueduct.

scholarly journals Research on Lateral Force of Pile Based on Liquefaction Site Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Zuo Xi ◽  
Zhou Enquan
Keyword(s):  
Velocity Field ◽  
Vibration Frequency ◽  
Site Effect ◽  
Lateral Force ◽  
Added Mass ◽  
Fluid Viscosity ◽  
Vector Method ◽  
Analytical Expression ◽  
Friction Resistance ◽  
Pressure Resistance

This paper presents a theoretical investigation on the lateral force of pile in liquefaction site. Regarded liquefied soil as fluid, the vector method can be used to analyze the liquefaction velocity field and solve the analytical solution of the dynamic field by making use of the principle of fluid mechanics. In addition, by solving the velocity field with vector symbol operation method, the analytical expression of the lateral force in the liquefied flow field is obtained, and the sensitivity of the parameters in the analytical expression is analyzed. The results show that the stress field of the pile contains both the pressure resistance caused by surface pressure and the friction resistance caused by shear stress, when the liquefied soil flows laterally. The lateral forces on the pile are mainly composed of inertial forces and damping forces and are related to density, fluid viscosity, pile radius, and vibration frequency. With the increase of density, fluid viscosity, and pile radius, the added mass and added damping increase gradually. In a certain range, added mass and added damping are sensitive to vibration frequency.

Thrombus formation on artificial surfaces: Correlative microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 840-841
Author(s):  
Quintin J. Lai ◽  
Stuart L. Cooper ◽  
Ralph M. Albrecht
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Low Voltage ◽  
Thrombus Formation ◽  
Blood Platelets ◽  
Polymer Surfaces ◽  
Flow Conditions ◽  
Transmission Electron ◽  
Adhesion Of Platelets ◽  
Microscopic Techniques

Thrombus formation and embolization are significant problems for blood-contacting biomedical devices. Two major components of thrombi are blood platelets and the plasma protein, fibrinogen. Previous studies have examined interactions of platelets with polymer surfaces, fibrinogen with platelets, and platelets in suspension with spreading platelets attached to surfaces. Correlative microscopic techniques permit light microscopic observations of labeled living platelets, under static or flow conditions, followed by the observation of identical platelets by electron microscopy. Videoenhanced, differential interference contrast (DIC) light microscopy permits high-resolution, real-time imaging of live platelets and their interactions with surfaces. Interference reflection microscopy (IRM) provides information on the focal adhesion of platelets on surfaces. High voltage, transmission electron microscopy (HVEM) allows observation of platelet cytoskeletal structure of whole mount preparations. Low-voltage, high resolution, scanning electron microscopy allows observation of fine surface detail of platelets. Colloidal gold-labeled fibrinogen, used to identify the Gp Ilb/IIIa membrane receptor for fibrinogen, can be detected in all the above microscopies.

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