Measurement of Energy Dissipation in a Liquid-Filled, Precessing, Spherical Cavity

1971 ◽  
Vol 38 (3) ◽  
pp. 674-682 ◽  
Author(s):  
J. P. Vanyo ◽  
P. W. Likins
Keyword(s):  
Energy Dissipation ◽  
Spherical Cavity ◽  
Mechanical Energy ◽  
Rigid Sphere ◽  
Analytical Approximations ◽  
Constant Rate ◽  
Experimental Apparatus ◽  
Half Angle ◽  
Analytical Estimation ◽  
Order Of Magnitude

Methods are described for the experimental measurement and analytical estimation of the losses of mechanical energy in a spinning and precessing spherical cavity filled with fluid. Test results are presented and correlated with analytical estimates based on two different mathematical models of the system. The experimental apparatus is a gimbaled mechanism which constrains a rigid body with a spherical cavity to spin about an axis through the cavity center at a constant rate ψ˙, while the spin axis cones about an inertially fixed axis at a constant rate φ˙ with a constant conical half angle θ. Measurements of current required by motors which maintain the constancy of ψ˙ and φ˙ provide a measure of the energy losses in the fluid in the steady state, after suitable dry test calibrations. Experimental results are presented for a 22-cm-dia cavity containing fluids of kinematic viscosities of 1 and 20 centistokes, with θ ranging from 5–30 deg, ψ˙ ranging from 60–1000 rpm, and φ˙ ranging from −400 to +600 rpm. Analytical approximations are developed on the basis of (a) a variation of the oscillating flat-plate solution, and (b) a rigid interior sphere of fluid idealization. The rigid sphere method gives energy dissipation rates that are generally valid over most of the important range of parameters, while the oscillating surface solution is generally an order of magnitude too low in its predictions of energy dissipation.

An Energy Assessment for Liquids in a Filled Precessing Spherical Cavity

1973 ◽  
Vol 40 (4) ◽  
pp. 851-856 ◽  
Author(s):  
J. P. Vanyo
Keyword(s):  
Energy Dissipation ◽  
Turbulent Flows ◽  
Spherical Cavity ◽  
Fluid Motion ◽  
Analytical Models ◽  
Physical Parameters ◽  
Energy Assessment ◽  
Analytical Approximations ◽  
Dissipation Rates ◽  
Direct Applicability

Experimental results and analytical approximations for energy dissipation due to liquids in a filled precessing spherical cavity are presented. The range of physical parameters include kinematic viscosities from 1 to 1000 centistokes, half coning angles from 5/8 to 10 deg, precession speeds from 0.15 to 200 rpm, and spin speeds (relative to the precessing frame) of from 7.5–900 rpm. These parameters and the associated energy dissipation rates, as low as 10−4 watts, place the results in the region of direct applicability to spinning satellite stability problems. A dimensionless parameter related to an Ekman number is used to correlate energy dissipation rates with laminar, intermediate, and fully turbulent flows. The reduced data are integrated with data from other sources and used to develop equations in dimensionless form for the experimental and analytical results. The results, while not defining details of fluid motion, place experimental bounds on the integrated shear stress at the cavity wall for analytical models.

Energy dissipation rate in a baffled vessel with pitched blade turbine impeller

1991 ◽  
Vol 56 (9) ◽  
pp. 1856-1867 ◽  
Author(s):  
Zdzisław Jaworski ◽  
Ivan Fořt
Keyword(s):  
Energy Dissipation ◽  
Cross Sections ◽  
Mechanical Energy ◽  
Vessel Diameter ◽  
Energy Dissipation Rate ◽  
Mean Velocity ◽  
Agitated Vessel ◽  
Radial Profiles ◽  
Pitched Blade Turbine ◽  
Turbine Impeller

Mechanical energy dissipation was investigated in a cylindrical, flat bottomed vessel with four radial baffles and the pitched blade turbine impeller of varied size. This study was based upon the experimental data on the hydrodynamics of the turbulent flow of water in an agitated vessel. They were gained by means of the three-holes Pitot tube technique for three impeller-to-vessel diameter ratio d/D = 1/3, 1/4 and 1/5. The experimental results obtained for two levels below and two levels above the impeller were used in the present study. Radial profiles of the mean velocity components, static and total pressures were presented for one of the levels. Local contribution to the axial transport of the agitated charge and energy was presented. Using the assumption of the axial symmetry of the flow field the volumetric flow rates were determined for the four horizontal cross-sections. Regions of positive and negative values of the total pressure of the liquid were indicated. Energy dissipation rates in various regions of the agitated vessel were estimated in the range from 0.2 to 6.0 of the average value for the whole vessel. Hydraulic impeller efficiency amounting to about 68% was obtained. The mechanical energy transferred by the impellers is dissipated in the following ways: 54% in the space below the impeller, 32% in the impeller region, 14% in the remaining part of the agitated liquid.

The stress generated in a non-dilute suspension of elongated particles by pure straining motion

1971 ◽  
Vol 46 (4) ◽  
pp. 813-829 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Theoretical Formula ◽  
Rigid Sphere ◽  
Cross Sectional ◽  
Outer Flow ◽  
Rigid Particles ◽  
Bulk Stress ◽  
Order Of Magnitude ◽  
Sectional Plane ◽  
Dilute Suspension ◽  
A Minor

In a pure straining motion, elongated rigid particles in suspension are aligned parallel to the direction of the greatest principal rate of extension, provided the effect of Brownian motion is weak. If the suspension is dilute, in the sense that the particles are hydrodynamically independent, each particle of length 2l makes a contribution to the bulk deviatoric stress which is of roughly the same order of magnitude as that due to a rigid sphere of radius l. The fractional increase in the bulk stress due to the presence of the particles is thus equal to the concentration by volume multiplied by a factor of order l2/b2, where 2b is a measure of the linear dimensions of the particle cross-section. This suggests that the stress due to the particles might be relatively large, for volume fractions which are still small, with interesting implications for the behaviour of polymer solutions. However, dilute-suspension theory is not applicable in these circumstances, and so an investigation is made of the effect of interactions between particles. It is assumed that, when the average lateral spacing of particles (h) satisfies the conditions b [Lt ] h [Lt ] l, the disturbance velocity vector is parallel to the particles and varies only in the cross-sectional plane. The velocity near a particle is found to have the same functional form as for an isolated particle, and the modification to the outer flow field for one particle is determined by replacing the randomly placed neighbouring particles by an equivalent cylindrical boundary. The resulting expression for the contribution to the bulk stress due to the particles differs from that for a dilute suspension only in a minor way, viz. by the replacement of log 2l/b by log h/b, and the above suggestion is confirmed. The relative error in the expression for the stress is expected to be of order (log h/b)−1. Some recent observations by Weinberger of the stress in a suspension of glass-fibre particles for which 2l/h = 7·4 and h/2b = 7·8 do show a particle stress which is much larger than the ambient-fluid stress, although the theoretical formula is not accurate under these conditions.

Mechanical Energy Dissipation and Performance in Alpine Ski Racing

2008 ◽  
Vol 40 (Supplement) ◽  
pp. S165 ◽  
Author(s):  
Robert Reid ◽  
Matthias Gilgien ◽  
Tron Moger ◽  
Håvard Tjørhom ◽  
Per Haugen ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Mechanical Energy ◽  
Mechanical Energy Dissipation ◽  
And Performance

Virtual Coupling Control Method for Robotic Gait

2013 ◽  
Vol 278-280 ◽  
pp. 629-632
Author(s):  
Li Peng Yuan ◽  
Amur Al Yahmedi ◽  
Li Ming Yuan
Keyword(s):  
Energy Dissipation ◽  
Hybrid Model ◽  
Control Strategy ◽  
Control Method ◽  
Mechanical Energy ◽  
Control Laws ◽  
Gait Patterns ◽  
Walking Gait ◽  
Virtual Coupling ◽  
Mechanical Energy Dissipation

Here, we consider the walking gait patterns. And we presented a hybrid model for a passive 2D walker with knees and point feet. The dynamics of this model were fully derived analytically. We have also proposed virtual coupling control laws. The control strategy is formed by taking into account the features of mechanical energy dissipation and restoration. And we also prove some walking rules maybe true.

The Use of Nanoporous Materials for Mechanical Energy Dissipation

2017 ◽  
Author(s):  
Isabelle Beurroies ◽  
Damien Presle ◽  
Julien Rodriguez ◽  
Renaud Denoyel
Keyword(s):  
Energy Dissipation ◽  
Mechanical Energy ◽  
Nanoporous Materials ◽  
Mechanical Energy Dissipation

scholarly journals Study of Mechanical Energy Dissipation by Normal and Decalcified Animals Bones

2019 ◽  
Vol 16 (1) ◽  
pp. 113-119
Author(s):  
Abdul Rauf ◽  
Syed Ismail Ahmad
Keyword(s):  
Energy Dissipation ◽  
Viscoelastic Properties ◽  
Applied Load ◽  
Mechanical Energy ◽  
Maximum Energy ◽  
Hysteresis Curve ◽  
Normal Bone ◽  
Dissipation Of Energy ◽  
Mechanical Energy Dissipation ◽  
Energy Dissipated

The energy dissipated properties of normal and decalcified femur, rib and scapula bones of animals ox and camel have been studied by uniform bending technique. A hysteresis curve has been observed between the elevation in bone and load applied. It is observed that the energy dissipated as calculated from the hysteresis loop for rib is more than that of femur and scapula of ox and camel. It has been observed that the dissipation of energy in normal bone is less than that of decalcified bone under the same condition of applied load. The highest energy dissipation was observed in case of rib bone of camel compared to that of any other bone, rib of camel and scapula of ox dissipates maximum energy than femur bones. The study suggests that this technique is simple, elegant and inexpensive besides accurate in determining viscoelastic properties of bone.

scholarly journals Effect of Seawater Exposure on Impact Damping Behavior of Viscoelastic Material of Pounding Tuned Mass Damper (PTMD)

2019 ◽  
Vol 9 (4) ◽  
pp. 632 ◽  
Author(s):  
Peng Zhang ◽  
Devendra Patil ◽  
Siu Ho
Keyword(s):  
Energy Dissipation ◽  
Viscoelastic Material ◽  
Hysteresis Loops ◽  
Tuned Mass Damper ◽  
Control Device ◽  
Impact Behavior ◽  
Lateral Impact ◽  
Experimental Apparatus ◽  
Mass Damper ◽  
The Impact

The pounding tuned mass damper (PTMD) is a novel vibration control device that can effectively mitigate the undesired vibration of subsea pipeline structures. Previous studies have verified that the PTMD is more effective and robust compared to the traditional tuned mass damper. However, the PTMD relies on a viscoelastic delimiter to dissipate energy through impact. The viscoelastic material can be corroded by the various chemical substances dissolved in the seawater, which means that there can be possible deterioration in its mechanical property and damping ability when it is exposed to seawater. Therefore, we aim to conduct an experimental study on the impact behavior and energy dissipation of the viscoelastic material submerged in seawater in this present paper. An experimental apparatus, which can generate and measure lateral impact, is designed and fabricated. A batch of viscoelastic tapes are submerged in seawater and samples will be taken out for impact tests every month. Pounding stiffness, hysteresis loops and energy dissipated per impact cycle are employed to characterize the impact behavior of the viscoelastic material. The experimental results suggest that the seawater has little influence on the behavior of the viscoelastic tapes. Even after continuous submersion in seawater for 5 years, the pounding stiffness and energy dissipation remains at the same level.

scholarly journals The series elastic shock absorber: tendon elasticity modulates energy dissipation by muscle during burst deceleration

2015 ◽  
Vol 282 (1804) ◽  
pp. 20142800 ◽  
Author(s):  
Nicolai Konow ◽  
Thomas J. Roberts
Keyword(s):  
Energy Dissipation ◽  
Shock Absorber ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Drop Height ◽  
Fascicle Length ◽  
Tendon Mechanics ◽  
Rapid Adjustment ◽  
Relationship Of ◽  
Tendon Compliance

During downhill running, manoeuvring, negotiation of obstacles and landings from a jump, mechanical energy is dissipated via active lengthening of limb muscles. Tendon compliance provides a ‘shock-absorber’ mechanism that rapidly absorbs mechanical energy and releases it more slowly as the recoil of the tendon does work to stretch muscle fascicles. By lowering the rate of muscular energy dissipation, tendon compliance likely reduces the risk of muscle injury that can result from rapid and forceful muscle lengthening. Here, we examine how muscle–tendon mechanics are modulated in response to changes in demand for energy dissipation. We measured lateral gastrocnemius (LG) muscle activity, force and fascicle length, as well as leg joint kinematics and ground-reaction force, as turkeys performed drop-landings from three heights (0.5–1.5 m centre-of-mass elevation). Negative work by the LG muscle–tendon unit during landing increased with drop height, mainly owing to greater muscle recruitment and force as drop height increased. Although muscle strain did not increase with landing height, ankle flexion increased owing to increased tendon strain at higher muscle forces. Measurements of the length–tension relationship of the muscle indicated that the muscle reached peak force at shorter and likely safer operating lengths as drop height increased. Our results indicate that tendon compliance is important to the modulation of energy dissipation by active muscle with changes in demand and may provide a mechanism for rapid adjustment of function during deceleration tasks of unpredictable intensity.

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