Sloshing of Fluid Between Rotating Inner Vertical Shaft and Stationary Outer Casing

2021 ◽  
Author(s):  
Koichi Yonezawa ◽  
Kosuke Nishimura ◽  
Takeshi Sano ◽  
Kazuyoshi Miyagawa ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Free Surface ◽  
Theoretical Model ◽  
Angular Velocity ◽  
Rotational Speed ◽  
Water Levels ◽  
Vertical Shaft ◽  
Surface Oscillation ◽  
Rotating Shaft ◽  
Initial Water ◽  
Sloshing Mode

Abstract Unsteady behaviors of free surface around a rotating vertical shaft in cylindrical stationary casing were investigated. Experiments were carried out with various rotating frequency of the shaft at two initial water levels. An axi-symmetrical free surface oscillation took place when the rotational speed of the shaft became larger than a certain value. The frequency of the free surface oscillation decreased as the rotating frequency increased. A theoretical model was developed, and the mechanisms of the free surface oscillation were clarified. The oscillation was found to be a sloshing mode excited by the change of fluid angular velocity, caused by the change of wetted areas on the inner rotating shaft and outer stationary casing, associated with the change in free surface height.

On the Nonlinear Behavior of Rotating Shafts

1991 ◽  
Author(s):  
Tatu Leinonen
Keyword(s):  
Theoretical Model ◽  
General Theory ◽  
Nonlinear Model ◽  
Nonlinear Behavior ◽  
Rotating Shaft ◽  
Rotating Shafts ◽  
Bending Behaviour

Abstract This paper presents a nonlinear model to describe the bending behaviour of a rotating shaft, based on the general theory of a bending bar. Justification for this theoretical model has been provided by tests, the resulting curves more closely fitting observed results than those of other models.

scholarly journals Free-surface flow simulations for discharge-based operation of hydraulic structure gates

2013 ◽  
Vol 16 (1) ◽  
pp. 189-206 ◽  
Author(s):  
C. D. Erdbrink ◽  
V. V. Krzhizhanovskaya ◽  
P. M. A. Sloot
Keyword(s):  
Free Surface ◽  
Hydraulic Structure ◽  
Flow Characteristics ◽  
Surface Flow ◽  
Water Levels ◽  
Surface Model ◽  
Local Flow ◽  
Gate Operation ◽  
Flow Equations ◽  
Flow Simulations

We combine non-hydrostatic flow simulations of the free surface with a discharge model based on elementary gate flow equations for decision support in the operation of hydraulic structure gates. A water level-based gate control used in most of today's general practice does not take into account the fact that gate operation scenarios producing similar total discharged volumes and similar water levels may have different local flow characteristics. Accurate and timely prediction of local flow conditions around hydraulic gates is important for several aspects of structure management: ecology, scour, flow-induced gate vibrations and waterway navigation. The modelling approach is described and tested for a multi-gate sluice structure regulating discharge from a river to the sea. The number of opened gates is varied and the discharge is stabilized with automated control by varying gate openings. The free-surface model was validated for discharge showing a correlation coefficient of 0.994 compared to experimental data. Additionally, we show the analysis of computational fluid dynamics (CFD) results for evaluating bed stability and gate vibrations.

Jumping drops on the surface of the water

2020 ◽  
Vol 15 (3-4) ◽  
pp. 228-231
Author(s):  
A.G. Terentiev
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Theoretical Model ◽  
Drop Size ◽  
Initial Conditions ◽  
Water Drop ◽  
Numerical Calculations ◽  
Rise Height

The paper proposes a theoretical model for the bouncing of a water drop on a free surface. The motion of a drop in air is described by the usual equations connecting the forces of inertia, gravity, and Stokes (viscosity resistance). The drop is considered spherical with a given surface tension. Numerical calculations were carried out using the same algorithm, but with different initial conditions. Some conditions are set for the droplet disintegration, others for the droplet reflection from the free surface. It is shown that the disintegration of a drop occurs periodically with a decrease in the drop size and an increase in the drop rise height. In the interval between droplet decays, periodic reflection from the free surface occurs with a decrease in the rise height.

On the Hydrodynamic Interaction Between Ship and Free-Surface Motions on Vessels With Moonpools

2019 ◽  
Author(s):  
Senthuran Ravinthrakumar ◽  
Trygve Kristiansen ◽  
Babak Ommani
Keyword(s):  
Free Surface ◽  
Flow Separation ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Dimensional Case ◽  
Navier Stokes ◽  
Linear Potential ◽  
Two Dimensional ◽  
Sloshing Mode ◽  
Vessel Motion

Abstract Coupling between moonpool resonance and vessel motion is investigated in two-dimensional and quasi three-dimensional settings, where the models are studied in forced heave and in freely floating conditions. The two-dimensional setups are with a recess, while the quasi three-dimensional setups are without recess. One configuration with recess is presented for the two-dimensional case, while three different moonpool sizes (without recess) are tested for the quasi three-dimensional setup. A large number of forcing periods, and three wave steepnesses are tested. Boundary Element Method (BEM) and Viscous BEM (VBEM) time-domain codes based on linear potential flow theory, and a Navier–Stokes solver with linear free-surface and body-boundary conditions, are implemented to investigate resonant motion of the free-surface and the model. Damping due to flow separation from the sharp corners of the moonpool inlets is shown to matter for both vessel motions and moonpool response around the piston mode. In general, the CFD simulations compare well with the experimental results. BEM over-predicts the response significantly at resonance. VBEM provides improved results compared to the BEM, but still over-predicts the response. In the two-dimensional study there are significant coupling effects between heave, pitch and moonpool responses. In the quasi three-dimensional tests, the coupling effect is reduced significantly as the moonpool dimensions relative to the displaced volume of the ship is reduced. The first sloshing mode is investigated in the two-dimensional case. The studies show that damping due to flow separation is dominant. The vessel motions are unaffected by the moonpool response around the first sloshing mode.

scholarly journals Roughness Effect of Submerged Groyne Fields with Varying Length, Groyne Distance, and Groyne Types

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1253 ◽  
Author(s):  
Ronald Möws ◽  
Katinka Koll
Keyword(s):  
Flow Resistance ◽  
Relative Increase ◽  
Design Guidelines ◽  
Water Levels ◽  
Constant Field ◽  
Initial Water ◽  
Mobile Bed ◽  
Wake Interference ◽  
Backwater Effect ◽  
Varying Length

Design guidelines were developed for a number of in-stream structures; however, the knowledge about their morphological and hydraulic function is still incomplete. A variant is submerged groynes, which aim to be applicable for bank protection especially in areas with restricted flood water levels due to their shallow height. Laboratory experiments were conducted to investigate the backwater effect and the flow resistance of submerged groyne fields with varying and constant field length and groyne distance. The effect of the shape of a groyne model was investigated using two types of groynes. The validity of different flow types, from “isolated roughness” to “quasi smooth”, was analyzed in relation to the roughness density of the groyne fields. The results show a higher backwater effect for simplified groynes made of multiplex plates, compared to groynes made of gravel. The relative increase of the upstream water level was lower at high initial water levels, for short length of the groyne field, and for larger distance between the single groynes. The highest roughness of the groyne fields was found at roughness densities, which indicated wake interference flow. Considering a mobile bed, the flow resistance was reduced significantly.

Highly turbulent Couette–Taylor bubbly flow patterns

2000 ◽  
Vol 422 ◽  
pp. 55-68 ◽  
Author(s):  
K. ATKHEN ◽  
J. FONTAINE ◽  
J. E. WESFREID
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Turbulent Flows ◽  
Rotational Speed ◽  
Bubbly Flow ◽  
Axial Flow ◽  
Taylor Vortices ◽  
Phase Velocities ◽  
Temporal Properties ◽  
Visualization Techniques

We present the results of experimental study of a Couette–Taylor system with superimposed axial flow and an upper free surface, in the high Taylor number regime. At large Taylor numbers, when the rotational speed of the inner cylinder increases, bubbles created near the free surface are distributed throughout the test section and permit the study of the spatial and temporal properties of turbulent flows using visualization techniques. In addition to classic travelling Taylor vortices, intermittent pulses of vortices with higher phase velocities are also observed. These patterns are described in terms of the rotational speed and the intensity of the throughflow.

On the Structural Nonlinearity of Rotating Shafts

1994 ◽  
Vol 116 (3) ◽  
pp. 404-407 ◽  
Author(s):  
Tatu Leinonen
Keyword(s):  
Theoretical Model ◽  
General Theory ◽  
Nonlinear Model ◽  
Rotating Shaft ◽  
Structural Nonlinearity ◽  
Rotating Shafts ◽  
Bending Behavior

This paper presents a nonlinear model to describe the bending behavior of a rotating shaft, based on the general theory of a bending bar. Justification for this theoretical model is provided by tests, the resulting curves fitting the observed results more closely than those of other models. In particular, the model explains why infinite points of deformation coming from linear theories can be avoided.

Influence of the Contact Pressure on the Rolling Resistance Moments in Dry Ball-Race Contacts

2014 ◽  
Vol 658 ◽  
pp. 305-310
Author(s):  
Alina Corina Dumitrascu ◽  
Gelu Ianus ◽  
Dumitru Olaru
Keyword(s):  
Theoretical Model ◽  
Contact Pressure ◽  
Rotational Speed ◽  
Ball Bearing ◽  
Rolling Resistance ◽  
Theoretical Models ◽  
Hertzian Contact ◽  
Experimental Methodology ◽  
Experimental Values ◽  
Good Agreement

Based on a theoretical model and an experimental methodology for defining the rolling resistance moments in a modified thrust ball bearing having only 3 balls, the authors experimentally investigated the influence of the Hertzian contact pressure on rolling resistance moments between a ball and a race. The experiments were realized with balls having diameters between 1.588 mm and 4.762 mm with maximum Hertzian pressure between 0.2GPa and 1GPa, operating for rotational speed between 60rpm to 210 rpm. The experiments evidenced that the measured values of the rolling resistance moments have higher values that the theoretical hysteresis and curvature rolling resistance moments for low contact pressure. By increasing of the contact pressure to 1GPa the experimental values for rolling resistance moments are in good agreement with the theoretical models.

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