scholarly journals Corrections to the theory and the optimal line in the swimming diagram of Taylor (1952)

2010 ◽  
Vol 7 (49) ◽  
pp. 1243-1246
Author(s):  
Joseph A. C. Humphrey ◽  
Jun Chen ◽  
Tetsuya Iwasaki ◽  
W. Otto Friesen
Keyword(s):  
Energy Dissipation ◽  
Cross Section ◽  
Circular Cross Section ◽  
Resistive Force ◽  
Animal Body ◽  
Fluid Forces ◽  
Optimal Line ◽  
Resistive Force Theory ◽  
Undulatory Swimming ◽  
Mathematical Error

The analysis of undulatory swimming gaits requires knowledge of the fluid forces acting on the animal body during swimming. In his classical 1952 paper, Taylor analysed this problem using a ‘resistive-force’ theory. The theory was used to characterize the undulatory gaits that result in the smallest energy dissipation to the fluid for a given swim velocity. The optimal gaits thus found were compared with data recorded from movies of a snake and a leech swimming. This report identifies and corrects a mathematical error in Taylor’s paper, showing that his theory applies even better to animals of circular cross section.

Velocity Field and Energy Dissipation in Viscoplastic Flow in Tubes of Non-Circular Cross-Section

2014 ◽  
Author(s):  
Mario F. Letelier ◽  
Dennis A. Siginer ◽  
Felipe Godoy
Keyword(s):  
Energy Dissipation ◽  
Velocity Field ◽  
Yield Stress ◽  
Cross Section ◽  
Mechanical Energy ◽  
Longitudinal Velocity ◽  
Circular Cross Section ◽  
Viscoplastic Flow ◽  
Entire Cross Section ◽  
Cross Sectional

An analytical method for determining the velocity field, shear stress and energy dissipation in viscoplastic flow in non-circular straight tubes is presented. Bingham’s model of fluid is used for the case of tubes with several cross-sectional contours that can be arbitrarily chosen through a shape factor imposed in the solution for the longitudinal velocity. The analysis is extended to steady flow in tubes in which the cross-section contour exhibits sharp corners. In these cases three flow zones are distinguished: stagnant, non-zero deformation, and plug zones. The method provides the expressions for determining the boundaries and characteristics of those three zones for a wide variety of cross-section shapes. In particular the dynamics of plug-zones for large values of the yield stress and for contours that markedly differ from circumferences is analyzed. Energy dissipation is determined throughout the entire cross-section, so that the effect of shape on mechanical energy loss is assessed in terms of the yield stress and viscosity of the fluid. Some general expressions that help understand energy dissipation mechanisms are derived by using natural coordinates for the velocity field and related variables. These results draw on several recent works from other researchers and the present authors, which have highlighted the significant difficulty of determining the zones of zero deformation in viscoplastic flow when the related solid boundaries are not elementary.

Finite Element Modelling of Buckling Restrained Braces under Combined In-Plane and Out-of-Plane Loading

2018 ◽  
Vol 763 ◽  
pp. 908-915
Author(s):  
Jian Cui ◽  
Chin Long Lee ◽  
Gregory A. MacRae
Keyword(s):  
Finite Element ◽  
Energy Dissipation ◽  
Cross Section ◽  
Finite Element Modelling ◽  
Circular Cross Section ◽  
Element Model ◽  
Buckling Restrained Braces ◽  
Out Of Plane ◽  
Simulation Results ◽  
Insight Into

During earthquakes, buckling restrained braces (BRBs) are likely subjected to both in-plane (INP) and out-of-plane (OOP) loadings simultaneously, therefore, BRBs are required to act robustly under combined INP and OOP loading. It is believed that the OOP loading will reduce the energy dissipation ability of BRBs. The intent of this study is to numerically investigate the performance of BRBs under combined INP and OOP loading with a finite element model of BRB with circular cross-section. Restraining concrete within the BRB is modeled as connector elements in the model and is proven to be an effective way. Simulation results show that the performance of BRBs under combined INP and OOP loading is not as good as that under the INP loading only and the energy dissipation ability is decreased by about 15% when the magnitude of OOP loading is equal to that of INP loading. Furthermore, the results give a deeper insight into the behaviour of BRBs under different combined OOP and INP loading histories.

SAF file: It's really three dimensional file

2018 ◽  
Vol 14 (1) ◽  
pp. 1
Author(s):  
Prof. Dr. Jamal Aziz Mehdi
Keyword(s):  
Cross Section ◽  
Root Canal ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Circular Motion ◽  
Root Canal Treatment ◽  
Metal Core ◽  
Rotating Blade

The biological objectives of root canal treatment have not changed over the recentdecades, but the methods to attain these goals have been greatly modified. Theintroduction of NiTi rotary files represents a major leap in the development ofendodontic instruments, with a wide variety of sophisticated instruments presentlyavailable (1, 2).Whatever their modification or improvement, all of these instruments have onething in common: they consist of a metal core with some type of rotating blade thatmachines the canal with a circular motion using flutes to carry the dentin chips anddebris coronally. Consequently, all rotary NiTi files will machine the root canal to acylindrical bore with a circular cross-section if the clinician applies them in a strictboring manner

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