Analysis of passive flexion in propelling a plunging plate using a torsion spring model

2018 ◽  
Vol 857 ◽  
pp. 562-604 ◽  
Author(s):  
N. Arora ◽  
C.-K. Kang ◽  
W. Shyy ◽  
A. Gupta
Keyword(s):  
Frequency Ratio ◽  
Maximum Velocity ◽  
Small Deformation ◽  
Maximum Deformation ◽  
Lattice Boltzmann Simulations ◽  
Structural Inertia ◽  
Work Input ◽  
Unit Work ◽  
Large Phase ◽  
Wing Deformation

We mimic a flapping wing through a fluid–structure interaction (FSI) framework based upon a generalized lumped-torsional flexibility model. The developed fluid and structural solvers together determine the aerodynamic forces, wing deformation and self-propelled motion. A phenomenological solution to the linear single-spring structural dynamics equation is established to help offer insight and validate the computations under the limit of small deformation. The cruising velocity and power requirements are evaluated by varying the flapping Reynolds number ($20\leqslant Re_{f}\leqslant 100$), stiffness (represented by frequency ratio,$1\lesssim \unicode[STIX]{x1D714}^{\ast }\leqslant 10$) and the ratio of aerodynamic to structural inertia forces (represented by a dimensionless parameter$\unicode[STIX]{x1D713}$($0.1\leqslant \unicode[STIX]{x1D713}\leqslant 3$)). For structural inertia dominated flows ($\unicode[STIX]{x1D713}\ll 1$), pitching and plunging are shown to always remain in phase ($\unicode[STIX]{x1D719}\approx 0$) with the maximum wing deformation occurring at the end of the stroke. When aerodynamics dominates ($\unicode[STIX]{x1D713}>1$), a large phase difference is induced ($\unicode[STIX]{x1D719}\approx \unicode[STIX]{x03C0}/2$) and the maximum deformation occurs at mid-stroke. Lattice Boltzmann simulations show that there is an optimal$\unicode[STIX]{x1D714}^{\ast }$at which cruising velocity is maximized and the location of optimum shifts away from unit frequency ratio ($\unicode[STIX]{x1D714}^{\ast }=1$) as$\unicode[STIX]{x1D713}$increases. Furthermore, aerodynamics administered deformations exhibit better performance than those governed by structural inertia, quantified in terms of distance travelled per unit work input. Closer examination reveals that although maximum thrust transpires at unit frequency ratio, it is not transformed into the highest cruising velocity. Rather, the maximum velocity occurs at the condition when the relative tip displacement${\approx}\,0.3$.

Quantitative Evaluation of Emulsion Styrene-Butadiene Rubbers and Compounding Variables by Controlled Mixing

1976 ◽  
Vol 49 (1) ◽  
pp. 1-11 ◽  
Author(s):  
S. B. Turetzky ◽  
P. R. Van Buskirk ◽  
P. F. Gunberg
Keyword(s):  
Flow Behavior ◽  
Mixing Time ◽  
Major Constituent ◽  
Time Profiles ◽  
Work Input ◽  
Unit Work ◽  
Work Concept ◽  
Styrene Butadiene ◽  
Temperature Time ◽  
Loading Procedure

Abstract Work reported recently described a “unit work” concept, according to which the flow behavior of a rubber-carbon black mixture was shown to be a function of the mixing work input. These results were shown to be independent of the size of the mixer, the speed of the mixer, and mixing time so long as the temperature-time profiles were similar, the same loading procedure was employed, and the same loading volume percentages were used. This concept provides a means to characterize not only the effect of various polymers, extenders, fillers, and minor additives, but also the uniformity of a given major constituent, which, in the case of an elastomer, may be a processability index. The work described in this paper is the application of the unit work concept to some of these areas : emulsion styrene-butadiene polymers, extenders, and fillers. By means of this concept of mixing, laboratory investigation can be translated, not only qualitatively, but much more important, quantitatively, into factory operations. The effects of polymer molecular weight and bound-styrene content changes, as well as changes in carbon blacks, such as those typified by the new tread blacks, can be investigated in the laboratory, and compounding adjustments can be made there, so that factory production time is not taken for new compound development.

Biomechanics of experimental spinal cord trauma

1978 ◽  
Vol 48 (6) ◽  
pp. 993-1001 ◽  
Author(s):  
George J. Dohrmann ◽  
Manohar M. Panjabi ◽  
Dennis Banks
Keyword(s):  
Spinal Cord ◽  
Maximum Velocity ◽  
Displacement Curve ◽  
Spinal Cord Trauma ◽  
Thoracic Spinal Cord ◽  
Content Type ◽  
Maximum Deformation ◽  
Thoracic Spinal ◽  
Deformation Velocity ◽  
The Relationship

✓ The biomechanics of the thoracic spinal cord and thorax in experimental trauma were studied in cats. Contusion of the T5–6 level of the feline spinal cord was accomplished by the weight-dropping technique; various combinations of weights and heights were used; and force, deformation/displacement, deformation velocity, and acceleration of deformation were measured. Greater force was associated with larger weights. Force was directly related to the displacement of the spinal cord and of the spinal cord/thorax. The presence of a “destruction point” on the force-displacement curve was suggested and its apparent significance discussed. Maximum deformation of the spinal cord was 1.1 mm, while the spinal cord/thorax was displaced a maximum of 4.6 mm. Deformation of the spinal cord ranged between 22% and 33% of the anteroposterior spinal cord diameter. Maximum deformation of the spinal cord was not associated necessarily with a maximum velocity of deformation; the range of velocity of spinal cord deformation was 0.12 to 0.18 m/sec. The relationship between velocity of deformation and force was a horizontal parabolic one. Greater force was required to obtain the same velocity of deformation of the spinal cord relative to that of the spinal cord/thorax unit. It was concluded that the mechanical alterations in the structures supporting the spinal cord account for a significant portion of the biomechanical measurements of the spinal cord previously reported in trauma. Since the force on the spinal cord and the thorax are the same, force may well be a most reasonable means of quantitating experimental spinal cord trauma.

Analysis of the Performance of Ionic Liquids in Cooling Loops

2007 ◽  
Author(s):  
Mihir Sen ◽  
Samuel Paolucci ◽  
Wenjun Liu
Keyword(s):  
Ionic Liquids ◽  
Fluid Velocity ◽  
Pressure Rise ◽  
Heat Rate ◽  
Physical Parameters ◽  
Fluid Properties ◽  
Work Input ◽  
Unit Work ◽  
Cooling Loops ◽  
Quantity Of Heat

Liquids are often pumped in closed loops to transfer heat from a high temperature source to a low temperature sink. They operate at low Reynolds number when the diameter of the pipe is small, the fluid velocity is low, or when the working liquid is very viscous. Ionic liquids, though environmentally friendly, typically have viscosities much larger than water. An analytical study is made of the process for the purpose of determining what the important physical parameters of the system are that will enable the largest quantity of heat to be transferred for unit work expended. For this purpose, a loop is considered that has a pump that generates a certain pressure rise and two heat exchangers, one for heating the fluid and the other for cooling it. Laminar flow that is fully-developed hy-drodynamically and thermally is assumed. The analysis is based on constant fluid properties, and analytical expressions are obtained for the heat rate and the work input.

Scale-Up of Internal Mixers

1984 ◽  
Vol 57 (1) ◽  
pp. 48-54 ◽  
Author(s):  
I. Manas-Zloczower ◽  
Z. Tadmor
Keyword(s):  
Shear Strain ◽  
Scale Up ◽  
Operating Conditions ◽  
Dimensionless Number ◽  
Operational Parameters ◽  
Acceptable Error ◽  
Work Input ◽  
Unit Work ◽  
New Criterion ◽  
Total Shear

Abstract In this paper, a new criterion for scaling Banbury type internal mixers is proposed. The new criterion is a dimensionless number Xt*, representing the product of the fraction of broken agglomerates during one pass through the high shear zone of the internal mixer and the average number of passes through this zone, for a given mixing time. It can be calculated for a given system of polymer-additive from a knowledge of machine geometry and operating conditions. The dimensionless number Xt* is uniquely related to the fraction of undispersed agglomerates, ψ, which is a frequently encountered mixing quality criterion. Experimental results reported in literature, for a broad range of mixer sizes, fit, within practical acceptable error, the theoretical curve ψ versus Xt*, lending support to its validity. Moreover, the dimensionless number Xt* correlates almost linearly with the presently used scaling-up criteria, the unit work input and the total shear strain, which in turn proved to be interrelated to other properties of the compound, such as Mooney viscosity and die-swell. However, while the unit work input and the total shear strain can be used in scaling only as long as proper operating conditions are met, the dimensionless number Xt* provides a reliable scale-up criterion for a broad range of mixer sizes and geometries as well as different operational parameters. Derived from a theoretical model of dispersive mixing in internal mixers based exclusively on fundamental considerations, this new criterion can be used also for mixing cycle optimization and basic machine design.

Investigation of a Hollow Shaft to Determine the Maximum Angular Velocity Regarding the FGM Properties

2019 ◽  
Vol 969 ◽  
pp. 669-677 ◽  
Author(s):  
Shams Torabnia ◽  
Mohammadreza Hemati ◽  
Sepideh Aghajani
Keyword(s):  
Yield Stress ◽  
Material Properties ◽  
Maximum Velocity ◽  
Small Deformation ◽  
Considerable Effect ◽  
Radial Coordinate ◽  
Hollow Shaft ◽  
Geometrical Properties ◽  
Strain Components ◽  
Power Law Function

To determine the maximum velocity of a rotating hollow shaft it is mandatory to understand the effects of material & geometrical properties variations. In this paper, mechanical behavior & maximum rotational speed of a hollow FGM shaft in elastic zone is investigated. The analysis is based on small deformation in plane-strain state. Young's modulus, density & yield stress are assumed to vary as a power-law function of radial coordinate. Introducing dimensionless parameters, the equilibrium equation has been analytically solved. For the case of equal exponent parameters, numerical results compared the effect of density & yield stress variation on displacement, strain & stress elements. The results are compared with a homogeneous shaft & a variable material properties case. It shows material properties’ variation may have a considerable effect on the stress & strain components & radial displacement & causes yielding onset from the inner radius of the shaft.

The High Resolution Appearance of Biological Substrates

1969 ◽  
Vol 27 ◽  
pp. 416-417
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Phase Image ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Resolution Electron ◽  
Discrete Structures ◽  
Large Phase ◽  
Biological Substrates ◽  
High Resolution Electron Micrographs

High resolution electron microscopic study of negatively stained macromolecules and thin sections of tissue embedded in a variety of media are difficult to interpret because of the superimposed phase image granularity. Although all of the information concerning the biological structure of interest may be present in a defocused electron micrograph, the high contrast of large phase image granules produced by the substrate makes it impossible to distinguish the phase ‘points’ from discrete structures of the same dimensions. Theory predicts the findings; however, it does not allow an appreciation of the actual appearance of the image under various conditions. Therefore, though perhaps trivial, training of the cheapest computer produced by mass labor has been undertaken in order to learn to appreciate the factors which affect the appearance of the background in high resolution electron micrographs.

Dislocations in alumina deformed by prismatic slip

1978 ◽  
Vol 36 (1) ◽  
pp. 606-607
Author(s):  
J. Cadoz ◽  
J. Castaing ◽  
J. Philibert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Basal Slip ◽  
Prismatic Slip ◽  
Compression Tests ◽  
Thin Sections ◽  
Burgers Vector ◽  
Maximum Deformation ◽  
Transmission Electron ◽  
Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

Umbilical artery time-averaged maximum velocity: First trimester reference range

2014 ◽  
Vol 74 (S 01) ◽  
Author(s):  
SK Amylidi ◽  
P Tappeser ◽  
B Mosimann ◽  
J Zdanowicz ◽  
M Baumann ◽  
...  
Keyword(s):  
Umbilical Artery ◽  
Reference Range ◽  
Maximum Velocity ◽  
First Trimester

Sources of Variability in Dose Response Platelet Aggregometry

1985 ◽  
Vol 53 (02) ◽  
pp. 219-220 ◽  
Author(s):  
M V Vickers ◽  
S G Thompson
Keyword(s):  
Dose Response ◽  
Maximum Velocity ◽  
Adenosine Diphosphate ◽  
Method Error ◽  
Platelet Aggregability ◽  
Differential Effects ◽  
Platelet Aggregometry ◽  
Simultaneous Comparison ◽  
Aggregation Parameters ◽  
Very High

SummaryAn experiment designed to assess the components of variability of a number of measures of platelet aggregability showed that the ADP ED50 (the estimated dose of adenosine diphosphate at which primary aggregation occurs at half its maximum velocity) had the least method error of any of the parameters measured, but that none had a very high between-person component of variability. A simultaneous comparison of a syringe technique and a free-flowing technique for venepuncture revealed no differential effects on the aggregation parameters measured. An enforced increase in the stirring speed in the aggregometer led to an experiment which showed that such a change did not apparently affect the ED50s.

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