Energy Balance in Vortex-Induced-Vibration of an Inverted Pendulum

2002 ◽  
Author(s):  
P. Dong ◽  
A. Voorhees ◽  
P. Atsavapranee ◽  
S. Kuchnicki ◽  
H. Benaroya ◽  
...  
Keyword(s):  
Inverted Pendulum ◽  
Energy Transport ◽  
Control Volume ◽  
Experimental Methodology ◽  
Fluid Structure Interactions ◽  
Integral Control ◽  
Image Velocimetry ◽  
Induced Motion ◽  
Modeling Data ◽  
Oscillation Frequencies

High resolution Digital Particle Image Velocimetry has been used to measure terms in the integral fluid energy transport equation. These data have been incorporated into a scientifically rigorous Hamilton’s Principle approach for modeling fluid-structure interactions. The interaction being modeled is the vortex-induced motion of a circular cylinder mounted like an inverted pendulum in a water tunnel. This paper describes the experimental methodology used to acquire key modeling data, i.e. kinetic energy transport and work across the boundaries of an integral control volume. There is also a presentation of a simple analysis showing that competition between vortex shedding and cylinder oscillation frequencies give rise to observed beating phenomena.

scholarly journals Effects of Entropy Generation, Thermal Radiation and Moving-Wall Direction on Mixed Convective Flow of Nanofluid in an Enclosure

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1471
Author(s):  
Sivasankaran Sivanandam ◽  
Ali J. Chamkha ◽  
Fouad O. M. Mallawi ◽  
Metib S. Alghamdi ◽  
Aisha M. Alqahtani
Keyword(s):  
Thermal Radiation ◽  
Entropy Generation ◽  
Energy Transport ◽  
Volume Fraction ◽  
Control Volume ◽  
Bejan Number ◽  
Moving Wall ◽  
Mixed Convective Flow ◽  
The Right ◽  
The Impact

A numeric investigation is executed to understand the impact of moving-wall direction, thermal radiation, entropy generation and nanofluid volume fraction on combined convection and energy transfer of nanoliquids in a differential heated box. The top wall of the enclosed box is assumed to move either to the left or the right direction which affects the stream inside the box. The horizontal barriers are engaged to be adiabatic. The derived mathematical model is solved by the control volume technique. The results are presented graphically to know the impact of the dissimilar ways of moving wall, Richardson number, Bejan number, thermal radiation, cup mixing and average temperatures. It is concluded that the stream and the thermal distribution are intensely affected by the moving-wall direction. It is established that the thermal radiation enhances the convection energy transport inside the enclosure.

scholarly journals Dynamics of heavy and buoyant underwater pendulums

2019 ◽  
Vol 862 ◽  
pp. 348-363 ◽  
Author(s):  
Varghese Mathai ◽  
Laura A. W. M. Loeffen ◽  
Timothy T. K. Chan ◽  
Sander Wildeman
Keyword(s):  
Mass Density ◽  
Wake Flow ◽  
Time Resolved ◽  
Small Deviations ◽  
Image Velocimetry ◽  
Damping Rate ◽  
Gravity Driven ◽  
The Mean ◽  
Oscillation Frequencies ◽  
Drag Term

The humble pendulum is often invoked as the archetype of a simple, gravity driven, oscillator. Under ideal circumstances, the oscillation frequency of the pendulum is independent of its mass and swing amplitude. However, in most real-world situations, the dynamics of pendulums is not quite so simple, particularly with additional interactions between the pendulum and a surrounding fluid. Here we extend the realm of pendulum studies to include large amplitude oscillations of heavy and buoyant pendulums in a fluid. We performed experiments with massive and hollow cylindrical pendulums in water, and constructed a simple model that takes the buoyancy, added mass, fluid (nonlinear) drag and bearing friction into account. To first order, the model predicts the oscillation frequencies, peak decelerations and damping rate well. An interesting effect of the nonlinear drag captured well by the model is that, for heavy pendulums, the damping time shows a non-monotonic dependence on pendulum mass, reaching a minimum when the pendulum mass density is nearly twice that of the fluid. Small deviations from the model’s predictions are seen, particularly in the second and subsequent maxima of oscillations. Using time-resolved particle image velocimetry (TR-PIV), we reveal that these deviations likely arise due to the disturbed flow created by the pendulum at earlier times. The mean wake velocity obtained from PIV is used to model an extra drag term due to incoming wake flow. The revised model significantly improves the predictions for the second and subsequent oscillations.

Wake states of a tethered cylinder

2007 ◽  
Vol 592 ◽  
pp. 1-21 ◽  
Author(s):  
J. CARBERRY ◽  
J. SHERIDAN
Keyword(s):  
Particle Image ◽  
Flow Fields ◽  
Low Flow ◽  
Response Data ◽  
Image Velocimetry ◽  
Mass Ratios ◽  
Induced Motion ◽  
The Mean ◽  
Low Amplitude ◽  
Flow Velocities

This paper describes an experimental investigation of a buoyant, m*<1, tethered cylinder which is free to move in an arc about its pivot points. The response of the cylinder, in particular its layover angle and flow-induced motion, is considered for a range of flow velocities and mass ratios. At pertinent parameters, the flow fields were also measured using particle image velocimetry (PIV). At lower mass ratios, 0.54≤m*≤0.72, two distinct states are observed, the low-amplitude and upper states. The transition from the low-amplitude state to the upper state is characterized by abrupt jumps in the amplitude of oscillation, the mean tether angle and the drag coefficient as well as distinct changes in the cylinder's wake. At higher mass ratios, the jump does not occur; however, as m* approaches unity at low flow velocities the cylinder's motion is more periodic than that observed at lower m*. The flow fields indicate that the low-amplitude state exhibits a 2S Kármán wake. The wake of the upper state has long shear layers extending well across the wake centreline, is not fully symmetric and is often consistent with either the 2P or P+S shedding modes. There is a collapse of the response data, in particular an excellent collapse of the mean layover angle, when the response parameters are plotted against the buoyancy Froude number, Frbuoyancy=U/((1-m*) gD)0.5. When the data collapses, the two states described above are clearly delineated.

Thermal Choking Due to Nonequilibrium Condensation

1994 ◽  
Vol 116 (3) ◽  
pp. 599-604 ◽  
Author(s):  
Abhijit Guha
Keyword(s):  
Gas Dynamics ◽  
Control Volume ◽  
Full Time ◽  
Condensation Zone ◽  
Explicit Equation ◽  
General Validity ◽  
Integral Control ◽  
Classical Gas ◽  
Nonequilibrium Condensation ◽  
Quantity Of Heat

A theory of thermal choking due to nonequilibrium condensation in a nozzle is presented. An explicit equation for the critical quantity of heat in condensing flow has been derived. The equation is of general validity and applies to vapor-droplet flow with or without a carrier gas. It has been usually assumed in the literature that the classical gas dynamics result for the critical quantity of heat applies in condensing flow as well. The classical result is, however, obtained by considering external heat addition to an ideal gas in a constant area duct. In this paper it is shown that the area variation across the condensation zone (although small) and the depletion in the mass of vapor as a result of condensation have profound effects on the critical quantity of heat. The present equation (derived from an integral, control-volume approach) agrees very well with results from full time-marching solution of the nonequilibrium, differential gas dynamic equations. The classical gas dynamics result, on the other hand, seriously underpredicts the critical heat for condensing flow in nozzles (by a factor of three in the example calculation presented).

Particle Image Velocimetry Based Measurement of Entropy Production With Free Convection Heat Transfer

2005 ◽  
Vol 127 (6) ◽  
pp. 614-623 ◽  
Author(s):  
O. B. Adeyinka ◽  
G. F. Naterer
Keyword(s):  
Particle Image Velocimetry ◽  
Free Convection ◽  
Entropy Production ◽  
Particle Image ◽  
Control Volume ◽  
Temperature Fields ◽  
Element Formulation ◽  
Measured Velocity ◽  
Numerical Predictions ◽  
Image Velocimetry

Local entropy production rates are determined from a numerical and experimental study of natural convection in an enclosure. Numerical predictions are obtained from a control-volume-based finite element formulation of the conservation equations and the Second Law. The experimental procedure combines methods of particle image velocimetry and planar laser induced fluorescence for measured velocity and temperature fields in the enclosure. An entropy based conversion algorithm in the measurement procedure is developed and compared with numerical predictions of free convection in the cavity. The predicted and measured results show close agreement. A measurement uncertainty analysis suggests that the algorithm postprocesses velocities (accurate within ±0.5%) to give entropy production data, which is accurate within ±8.77% near the wall. Results are reported for free convection of air and water in a square cavity at various Rayleigh numbers. The results provide measured data for tracking spatial variations of friction irreversibility and local exergy losses.

Flow-Induced Motion of an Elastically Mounted Circular Cylinder With Roughness Strips at Different Angles of Attack

2016 ◽  
Author(s):  
Li Zhang ◽  
Qiyang Shangguan ◽  
Lin Ding ◽  
Yanrong Chen ◽  
Qianyun Ye
Keyword(s):  
Circular Cylinder ◽  
Transverse Direction ◽  
Angle Of Attack ◽  
Cylinder Surface ◽  
Wake Region ◽  
Fluid Structure Interactions ◽  
Near Wake ◽  
Amplitude Response ◽  
Induced Motion ◽  
Simulation Results

Flow-induced motions (FIM) of an elastically mounted circular cylinder with roughness strips at different angles of attack are investigated by 2-D URANS simulations based on the open source CFD tool OpenFOAM. The cylinder is constrained to one degree of freedom motion in the transverse direction. Two selectively distributed roughness strips on cylinder surface are used to enhance the FIM of the cylinder. Simulations are conducted at Re = 60,000 and Re = 100,000 with the angle of attack, αattack, varies from 0° to 90°. Amplitude response, frequency response, and near-wake structures of the cylinder are discussed in numerical results. The simulation results indicate that both suppression and enhancement of FIM are observed for the cylinder as the angle of attack rises from 0° to 90°. For αattack≥ 55°, the near-wake region becomes quite slender and vortex shedding is suppressed. The FIM of the cylinder is greatly inhibited when αattack ≥55°. In addition, a complex vortex reattachment observed in the near-wake region intensifies the fluid-structure interactions and causes obviously higher amplitude.

Hydrodynamic of Bubble Boiling Regime With Artificially Produced Nucleation Site

2005 ◽  
Author(s):  
Sanib Basˇic´ ◽  
Jure Marn
Keyword(s):  
Natural Convection ◽  
Vertical Velocity ◽  
Nucleate Boiling ◽  
Measurement Procedure ◽  
Nucleation Site ◽  
Experimental Methodology ◽  
Boiling Regime ◽  
Narrow Region ◽  
Image Velocimetry ◽  
Boiling Process

In presented work a hydrodynamic of bubble boiling process in quiescent water has been investigated using PIV (Particle Image Velocimetry) experimental technique. Velocity distribution in narrow region over the artificially produced nucleation site that was active during the partial developed nucleate boiling has been presented in more details. Experimental methodology is based on specially arranged boiling measurement procedure and it includes a statistic cross-correlation function for the raw velocity vectors estimation and validation protocol where refined velocity filed of bubbling process is attained. Review of vertical velocity components in natural convection and bubble boiling regime at two selected temperatures along the boiling surface is given and some comparison is carried out. Vertical velocity profiles around the rising bubbles are presented in qualitative manner and vertical pumping characteristics of boiling process vs. natural convection are compared.

Aerodynamic load characterisation of a low speed aerofoil using particle image velocimetry

2008 ◽  
Vol 112 (1130) ◽  
pp. 197-205 ◽  
Author(s):  
B. W. van Oudheusden ◽  
E. W. F. Casimiri ◽  
F. Scarano
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Control Volume ◽  
Flow Simulation ◽  
Momentum Equation ◽  
Aerodynamic Load ◽  
Surface Pressure Distribution ◽  
Velocity Statistics ◽  
Image Velocimetry ◽  
Standard Pressure

AbstractParticle image velocimetry (PIV) measurements of the flow around a wing section are employed as a basis for non-intrusive aerodynamic mean loads characterisation, providing sectional lift, drag and pitching moment. The technique relies upon the application of control-volume approaches in combination with the deduction of the pressure from the PIV experimental data through application of the momentum equation. The treatment can also be applied when the flow is unsteady; in that case time-mean loads are obtained from velocity statistics, through the use of Reynolds-averaged formulation of the governing equations. The procedure was applied in the experimental investigation of a NACA 642A015 aerofoil, in which the PIV approach is validated against standard pressure-based methods (surface pressure distribution and wake rake). The chord Reynolds number considered in the investigation ranges between 1 – 7 × 105. In addition, the consistency and potential performance of the method was assessed by means of synthetic velocity field data obtained from a numerical flow simulation.

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