Flume investigation of cylindrical baffles for dissipation of debris flow energy

2021 ◽  
Author(s):  
Chan-Young Yune ◽  
Beom-Jun Kim
Keyword(s):  
Energy Dissipation ◽  
Debris Flow ◽  
Debris Flows ◽  
High Speed ◽  
Flow Characteristics ◽  
Digital Camera ◽  
Major Effect ◽  
Small Scale ◽  
Design Guideline ◽  
Flow Energy

<p>A debris flow with a high speed along valleys has been reported to cause serious damages to urban area or infrastructure. To prevent debris flow disaster, countermeasures for flow-impeding structures are installed on the flow path of debris flows. Recently, an installation of cylindrical baffles which are open-type countermeasures has increased because of a low construction cost, filtering out rocks, and an increased hydraulic continuity. However, a comprehensive design guideline for specification and arrangement on cylindrical baffles has not yet been suggested. Moreover, the design of baffle installation is mainly based on empirical approaches as the influence of baffle array on debris mobility is not well understood. In this study, to investigate the effect of cylindrical baffles on the flow characteristics of debris flow, a series of small-scale flume tests were performed according to the varying baffle height and row numbers of installed baffles. High-speed cameras and digital camera to record the flow interaction with baffles were installed at the top and side of the channel. To reproduce the viscosity of debris flows caused by fine-grained soil in the flume, glycerin was mixed with debris materials (sand and gravel). After the test, the velocity and energy dissipation according to various baffle arrays were estimated. Test results showed that the installation of baffles reduced the frontal velocity of debris flows. Furthermore, taller baffles also increased the effect of the energy dissipation in debris flows, but additional rows of the baffle did not have a major effect on the energy dissipation. Thus, increasing the height of baffle led to an increased efficiency of energy dissipation of debris flows.</p>

The Development of a Predictive Model for the Optimization of High-Speed Cam-Follower Systems with Coulomb Damping Internal Friction and Elastic and Fluidic Elements

1986 ◽  
Vol 108 (4) ◽  
pp. 506-515 ◽  
Author(s):  
Shervin Hanachi ◽  
Ferdinand Freudenstein
Keyword(s):  
Energy Dissipation ◽  
Dynamic Model ◽  
High Speed ◽  
Distributed Parameter ◽  
Predictive Capability ◽  
Valve Spring ◽  
Coulomb Damping ◽  
System Components ◽  
Cam Follower ◽  
Distributed Parameter Modeling

A highly accurate and predictive dynamic model of a high-speed cam-follower system has been developed and verified. In view of the predominance of Coulomb damping in high-speed cam-follower systems, this form of damping has been used as the chief mode of energy dissipation. This has resulted in a significant improvement in the predictive capability of the dynamic model. The accuracy of the model can also be attributed to careful modeling of system components such as the distributed-parameter modeling of the valve spring, the modeling of the hydraulic lifter, and modeling of the damping due to a nested-valve spring. The latter two represent the first such modeling in the area of cam-follower systems.

scholarly journals More than a safety line: jump-stabilizing silk of salticids

2013 ◽  
Vol 10 (87) ◽  
pp. 20130572 ◽  
Author(s):  
Yung-Kang Chen ◽  
Chen-Pan Liao ◽  
Feng-Yueh Tsai ◽  
Kai-Jung Chi
Keyword(s):  
Energy Dissipation ◽  
Dynamic Stability ◽  
Material Properties ◽  
High Speed ◽  
Prey Capture ◽  
Flapping Wings ◽  
Aerodynamic Forces ◽  
Physiological Control ◽  
Dragline Silk ◽  
Kinematic Data

Salticids are diurnal hunters known for acute vision, remarkable predatory strategies and jumping ability. Like other jumpers, they strive for stability and smooth landings. Instead of using inertia from swinging appendages or aerodynamic forces by flapping wings as in other organisms, we show that salticids use a different mechanism for in-air stability by using dragline silk, which was previously believed to function solely as a safety line. Analyses from high-speed images of jumps by the salticid Hasarius adansoni demonstrate that despite being subject to rearward pitch at take-off, spiders with dragline silk can change body orientation in the air. Instantaneous drag and silk forces calculated from kinematic data further suggest a comparable contribution to deceleration and energy dissipation, and reveal that adjustments by the spider to the silk force can reverse its body pitch for a predictable and optimal landing. Without silk, upright-landing spiders would slip or even tumble, deferring completion of landing. Thus, for salticids, dragline silk is critical for dynamic stability and prey-capture efficiency. The dynamic functioning of dragline silk revealed in this study can advance the understanding of silk's physiological control over material properties and its significance to spider ecology and evolution, and also provide inspiration for future manoeuvrable robot designs.

A Rotary Model for Spur Gear Dynamics

1985 ◽  
Vol 107 (4) ◽  
pp. 529-535 ◽  
Author(s):  
D. C. H. Yang ◽  
Z. S. Sun
Keyword(s):  
Energy Dissipation ◽  
Dynamic Model ◽  
High Speed ◽  
Spur Gear ◽  
Tooth Profile ◽  
Gear System ◽  
Gear Dynamics

We develop a dynamic model for a spur gear system with backlash. This model is circular and is geometrically different from the rectilinear gear model of Azar and Crossley. By taking advantage of involute tooth profile, we are able to take material compliance and energy dissipation into account. Furthermore, the complicated phenomenon of contact tooth pairs alternation between one and two during meshing is also included in the model. This model is believed to be closer to reality than the existing model and hopefully is useful in studying gears in high-speed and intermittent motions.

Atomic-scale simulation of hugoniot relations and energy dissipation of polyurea under high-speed shock

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kaili Yao ◽  
Dongyang Chu ◽  
Ting Li ◽  
Zhanli Liu ◽  
Bao-Hua Guo ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Energy Dissipation ◽  
Dihedral Angle ◽  
High Speed ◽  
Shock Loading ◽  
Heat Dissipation ◽  
Chain Conformation ◽  
Atomic Scale ◽  
Release Process ◽  
Content Type

Purpose The purpose of this paper is to calculate the Hugoniot relations of polyurea; also to investigate the atomic-scale energy change, the related chain conformation evolution and the hydrogen bond dissociation of polyurea under high-speed shock. Design/methodology/approach The atomic-scale simulations are achieved by molecular dynamics (MD). Both non-equilibrium MD and multi-scale shock technique are used to simulate the high-speed shock. The energy dissipation is theoretically derived by the thermodynamic and the Hugoniot relations. The distributions of bond length, angle and dihedral angle are used to characterize the chain conformation evolution. The hydrogen bonds are determined by a geometrical criterion. Findings The Hugoniot relations calculated are in good agreement with the experimental data. It is found that under the same impact pressure, polyurea with lower hard segment content has higher energy dissipation during the shock-release process. The primary energy dissipation way is the heat dissipation caused by the increase of kinetic energy. Unlike tensile simulation, the molecular potential increment is mainly divided into the increments of the bond energy, angle energy and dihedral angle energy under shock loading and is mostly stored in the soft segments. The hydrogen bond potential increment only accounts for about 1% of the internal energy increment under high-speed shock. Originality/value The simulation results are meaningful for understanding and evaluating the energy dissipation mechanism of polyurea under shock loading, and could provide a reference for material design.

scholarly journals Solid–Liquid Composites with High Impact Resistance

2021 ◽  
Author(s):  
Miao Yu ◽  
Xiying Li ◽  
Pengyu Lv ◽  
Huiling Duan
Keyword(s):  
Energy Dissipation ◽  
High Speed ◽  
Volume Fraction ◽  
Split Hopkinson Pressure Bar ◽  
Impact Resistance ◽  
High Impact ◽  
Strain Rates ◽  
Dynamic Impact ◽  
Solid Liquid ◽  
The Impact

AbstractSolid–liquid composites (SLCs) with novel thermal/electronic/mechanical properties imparted by programmable and functional liquid inclusions have attracted considerable research interest in recent years, and are widely used in smart electronics and soft robotics. The feasible application of SLCs requires that they exhibit excellent static physical properties as well as dynamic impact resistance to satisfy complex service conditions, such as drops and impacts. This paper examined the impact resistance of SLCs fabricated by using microfluidic 3D printing. The results of dynamic split-Hopkinson pressure bar (SHPB) tests showed that the performance of the fabricated SLCs improved in terms of energy dissipation and impact resistance compared with pristine materials. In case of dynamic impact in the strain rates ranging from 100 to $$400\,\hbox {s}^{-1}$$ 400 s - 1 , the SLC specimen deformed without fracture, and its energy dissipation was dominated by the viscosity of the liquid inclusions. For dynamic impact in the strain rates ranging from 500 to $$800\,\hbox {s}^{-1}$$ 800 s - 1 , the SLC specimen fractured and its energy dissipation was determined by the volume fraction of the liquid inclusions. Thus, the energy dissipation of the SLCs could be tuned by regulating the viscosity and volume fraction of the liquid inclusions to satisfy the requirements of protection against different strain rates. Furthermore, the process of fracture of the SLCs under the dynamic SHPB tests was recorded and analyzed by using a high-speed camera. The results showed that distributed liquid inclusions changed the paths of crack propagation to enhance energy dissipation in the SLCs. This study experimentally verified the enhancement in the energy dissipation of SLCs, and provided design strategies for developing multifunctional SLCs with high impact resistance.

Paper 9: A Theoretical Analysis of the Floating-Pad Journal Bearing

1969 ◽  
Vol 184 (12) ◽  
pp. 60-69
Author(s):  
R. B. Howarth
Keyword(s):  
Energy Dissipation ◽  
Theoretical Analysis ◽  
High Speed ◽  
Journal Bearing ◽  
Low Energy ◽  
Rigorous Analysis ◽  
Simplified Approach ◽  
Lubricant Flow ◽  
Excited Vibration ◽  
Low Load

Limited applications and investigations have shown that the floating-pad journal bearing is a practical form of bearing which can be used to advantage. The operational complexities make a rigorous analysis exceedingly difficult if not impossible, and a simplified approach is adopted. The results of the analysis suggest that the floating-pad journal bearing is most suitable for high-speed, low-load applications where advantage can be taken of its desirable properties, in particular low energy dissipation and the high lubricant flow that can be accommodated for cooling purposes. The analysis also predicts the occurrence of a self-excited vibration becoming more pronounced as the eccentricity increases.

Sign in / Sign up

Export Citation Format

Share Document