Influence of Skeg on Ship Manoeuvrability at High and Low Speeds

2020 ◽  
pp. 384-403
Author(s):  
Victor Ferrari ◽  
Tomasz Gornicz ◽  
Anton Kisjes ◽  
Frans H. H. A. Quadvlieg
Keyword(s):  
Low Speeds

Energy and Momentum

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
Time Dilation ◽  
Speed Of Light ◽  
Massless Particles ◽  
The Everyday ◽  
Low Speeds ◽  
Energy And Momentum ◽  
Deep Relationship ◽  
Insight Into ◽  
Momentum Relation

Tis chapter explains the famous equation E = mc2 as part of a wider relationship between energy, mass, and momentum. We start by defning energy and momentum in the everyday sense. We then build on the stretching‐triangle picture of spacetime vectors developed in Chapter 11 to see how energy, mass, and momentum have a deep relationship that is not obvious at everyday low speeds. When momentum is zero (a mass is at rest) this energy‐momentum relation simplifes to E = mc2, which implies that mass at rest quietly stores tremendous amounts of energy. Te energymomentum relation also implies that traveling near the speed of light (e.g., to take advantage of time dilation for interstellar journeys) will require tremendous amounts of energy. Finally, we look at the simplifed form of the energy‐momentum relation when the mass is zero. Tis gives us insight into the behavior of massless particles such as the photon.

scholarly journals A Collision Dynamics Model of a Multi-Level Train

2006 ◽  
Author(s):  
Michelle Priante ◽  
David Tyrell ◽  
Benjamin Perlman
Keyword(s):  
Three Dimensional ◽  
Design Parameters ◽  
Collision Dynamics ◽  
Dynamics Model ◽  
Single Level ◽  
High Speeds ◽  
Front End ◽  
Multi Level ◽  
Low Speeds ◽  
Vertical Accelerations

In train collisions, multi-level rail passenger vehicles can deform in modes that are different from the behavior of single level cars. The deformation in single level cars usually occurs at the front end during a collision. In one particular incident, a cab car buckled laterally near the back end of the car. The buckling of the car caused both lateral and vertical accelerations, which led to unanticipated injuries to the occupants. A three-dimensional collision dynamics model of a multi-level passenger train has been developed to study the influence of multi-level design parameters and possible train configuration variations on the reactions of a multi-level car in a collision. This model can run multiple scenarios of a train collision. This paper investigates two hypotheses that could account for the unexpected mode of deformation. The first hypothesis emphasizes the non-symmetric resistance of a multi-level car to longitudinal loads. The structure is irregular since the stairwells, supports for tanks, and draglinks vary from side to side and end to end. Since one side is less strong, that side can crush more during a collision. The second hypothesis uses characteristics that are nearly symmetric on each side. Initial imperfections in train geometry induce eccentric loads on the vehicles. For both hypotheses, the deformation modes depend on the closing speed of the collision. When the characteristics are non-symmetric, and the load is applied in-line, two modes of deformation are seen. At low speeds, the couplers crush, and the cars saw-tooth buckle. At high speeds, the front end of the cab car crushes, and the cars remain in-line. If an offset load is applied, the back stairwell of the first coach car crushes unevenly, and the cars saw-tooth buckle. For the second hypothesis, the characteristics are symmetric. At low speeds, the couplers crush, and the cars remain in-line. At higher speeds, the front end crushes, and the cars remain in-line. If an offset load is applied to a car with symmetric characteristics, the cars will saw-tooth buckle.

The gaits of chelonians: walking techniques for very low speeds

2009 ◽  
Vol 191 (3) ◽  
pp. 353-378 ◽  
Author(s):  
A. S. Jayes ◽  
R. McN. Alexander
Keyword(s):  
Low Speeds

The coating of Newtonian liquids onto a roll rotating at low speeds

1978 ◽  
Vol 18 (15) ◽  
pp. 1155-1159 ◽  
Author(s):  
S. Tharmalingam ◽  
W. L. Wilkinson
Keyword(s):  
Low Speeds ◽  
Newtonian Liquids

Shallow Rectangular Cavities at Low Speeds Including Effects of Yaw

2008 ◽  
Vol 45 (6) ◽  
pp. 2145-2150 ◽  
Author(s):  
S. L. Gai ◽  
T. J. Soper ◽  
J. F. Milthorpe
Keyword(s):  
Low Speeds

The Impact of Sweep Angle on Stepped Planing Hull Performance

2021 ◽  
Author(s):  
Nicholas Husser ◽  
Stefano Brizzolara
Keyword(s):  
Dynamic Stability ◽  
Sweep Angle ◽  
High Speeds ◽  
Free Running ◽  
Low Speeds ◽  
And Performance ◽  
The Impact

In this study the impact of sweep angle on stepped hull resistance, running attitude, and dynamic stability is investigated for a range of planing speeds from ventilation inception (𝐹𝛻≈2) to high planing speeds (𝐹𝛻≈7) using RANS CFD. Potential performance benefits of the step are isolated for three speeds and two displacements using fixed trim simulations. Differences in running attitude and dynamic stability are investigated using free running simulations at the highest speed for a range of LCG locations. Finally, any differences in ventilation inception and performance at low speeds are investigated using fixed trim and heave simulations. The study shows that swept forward steps do not necessarily ventilate earlier than other step designs but do provide resistance reductions at 𝐹𝛻<5 compared to swept aft and unstepped designs. However, at 𝐹𝛻>5, swept forward steps demonstrate significant resistance increases compared to unswept and swept aft steps. At high speeds, swept aft steps provide improved dynamic stability compared to other step designs without a resistance penalty when compared to unswept steps.

Friction and Tribological Considerations for Nanometer Range Machining

2001 ◽  
Author(s):  
Som Chattopadhyay
Keyword(s):  
Mathematical Model ◽  
High Precision ◽  
Local Deformation ◽  
Experimental Results ◽  
Precision Machining ◽  
Complex Motion ◽  
Positioning Accuracy ◽  
Nanometer Range ◽  
Motion Characteristic ◽  
Low Speeds

Abstract Positioning accuracy within the range of nanometers is required for high precision machining applications. The implementation of such a range is difficult through the slides because of (a) irregular nature of friction at the slider-guideway interface, and (b) complex motion characteristic at very low speeds. The complexity arises due to the local deformation at the interface prior to breakaway, which is known as microdynamics. In this work prior experimental results exhibiting microdynamics have been appraised, and mathematical model developed to understand this behavior.

Performance and Stability Improvement of AFO for Sensorless IM Drives in Low Speeds Regenerating Mode

2019 ◽  
Vol 34 (8) ◽  
pp. 7812-7825 ◽  
Author(s):  
Hady Abdel Maksoud ◽  
Shaaban M. Shaaban ◽  
Mohamed S. Zaky ◽  
Haitham Z. Azazi
Keyword(s):  
Low Speeds ◽  
Regenerating Mode

Initial Investigations Into the Dynamics of Cutting Brushes for Sweeping

2002 ◽  
Vol 124 (4) ◽  
pp. 675-681 ◽  
Author(s):  
G. M. Peel ◽  
G. A. Parker
Keyword(s):  
Steady State ◽  
Centrifugal Force ◽  
Transient Effects ◽  
Test Rig ◽  
Low Speeds ◽  
Discretized Model

Cutting brushes are used at relatively low speeds by various municipal vehicles and in particular road sweeping units. As the name suggests such brushes are designed to “cut” through debris, especially compacted sand or similar matter. The main deflection plane of a bristle (or tine) is along the mount radius, making the tines very stiff in the direction of rotation, hence the cutting action when the brush is rotated. Exploring the literature shows that very little is known, or understood, about the operation of brushes for mechanical sweeping. In this paper a pseudo-static discretized model is developed to investigate the deformations and forces acting on brushes during ideal operation of a horizontal brush on a flat plane. Due to the numerous different sweeper brushes on the market, one common configuration is used as the basis of the model and the paper will detail only the characteristics of this brush. The brush to be investigated is a “cutting brush,” introduced above, where the tines can only deflect along the mount radius. Having developed a model it is used to predict the forces and torques generated within a horizontally rotating brush. The influence of centrifugal force is analyzed although transient effects are neglected and steady state conditions assumed. The predictions of the model are compared to practical results taken from a test rig and the validity of the model is discussed. Agreement between the model and the practical results will be shown to be good, considering the complexities and practical realities involved in analyzing any system which is friction dependent.

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