scholarly journals Physical Modeling of Untrenched Pipeline Breakout From Sand-Bed in Ocean Currents

2010 ◽  
Author(s):  
Shu-Ming Yan ◽  
Fu-Ping Gao ◽  
Jing Cao ◽  
En-Yong Zhang ◽  
Guo-Hui Li ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Physical Modeling ◽  
Resistance Coefficient ◽  
Ocean Currents ◽  
Test Facility ◽  
Sand Particle ◽  
Lateral Stability ◽  
Soil Resistance ◽  
Pipe Surface ◽  
Flume Tests

The ultimate lateral soil resistance for pipe losing lateral stability on a sandy seabed under the action of ocean currents is investigated with a newly developed test facility by employing mechanical actuators to simulate hydrodynamic loads on the pipe. Two kinds of constraint conditions, i.e. anti-rolling pipe and freely-laid pipe, are taken into account, respectively. The experimental observations indicate that, the horizontal lateral soil resistance increases gradually to its maximum (ultimate) value when the additional settlement is fully developed. The buildup of the ultimate lateral soil resistance to the anti-rolling pipe benefits from not only the additional settlements but also the sand-particle collections in front of the moving pipe, especially for the anti-rolling pipes. The lateral-soil-resistance coefficient for the anti-rolling pipe is much larger than that for the freely-laid pipe. The pipe surface roughness also affects the lateral stability of anti-rolling pipes. A comparison is made between present mechanical-actuator tests and the previous water-flume tests, indicating the results of two types of tests are comparable and the local scour may reduce the pipe lateral stability in ocean currents.

An Approach to Determine the Stiffness Reduction Factor of Tunnel Lining

2011 ◽  
Vol 243-249 ◽  
pp. 3659-3662
Author(s):  
Hai Ying Zhou ◽  
Li Xin Li ◽  
Ting Guo Chen
Keyword(s):  
Numerical Analysis ◽  
Flexural Rigidity ◽  
Resistance Coefficient ◽  
Reduction Factor ◽  
Tunnel Lining ◽  
Soil Resistance ◽  
Stiffness Reduction ◽  
Simplified Method

Based on the segmental joint tests, it was found that the practical range of joint flexural rigidity was in range of 8500-29000kN•m/rad. A simplified method for determining the stiffness reduction factor of tunnel lining() was proposed using results from the segmental joint tests in which some parameters were obtained by calibration against a 3D Numerical analysis. The influence of joint flexural rigidity, soil resistance coefficient, thickness of tunnel lining and tunnel calculation radius on the stiffness reduction factor of tunnel lining was examined. The stiffness reduction factor can be simply expressed as a function of joint flexural rigidity ratio, soil resistance coefficient, thickness of tunnel lining and tunnel calculation radius for the typical tunnel lining.

EFFECT OF SURFACE ROUGHNESS ON THE ADHESIVE AND TRIBOLOGICAL CHARACTERISTICS OF DLC COATING PREPARED ON Co-Cr-Mo ALLOY

2002 ◽  
Vol 16 (06n07) ◽  
pp. 952-957 ◽  
Author(s):  
D. Sheeja ◽  
B. K. Tay ◽  
H. M. Lam ◽  
S. K. Ng
Keyword(s):  
Surface Roughness ◽  
Life Span ◽  
Substrate Surface ◽  
Resistance Coefficient ◽  
Metal Alloy ◽  
Deposition Condition ◽  
Dlc Coatings ◽  
Dlc Coating ◽  
Short Life Span ◽  
Substrate Surface Roughness

The Co-Cr-Mo alloy is extensively used for tribological applications, including orthopaedic components in total joint replacements. High quality diamond-like carbon (DLC) coatings on metal/alloy substrates are of great interest as they are able to protect them from severe wear and thus prolong the life span of the component. Since the roughness of the metal/alloy varies depending on the applications, a study has been carried out to investigate the effect of substrate surface roughness on the microstructure, sliding life, wear-resistance, coefficient of friction, adhension and hardness of DLC coatings prepared on Co-Cr-Mo alloy substrates under the same deposition condition. The microstructure of the films studied using Raman spectroscopy suggests that the film prepared on a smoother surface contains slightly higher fraction of sp 3 bonded carbon atoms. The characterization using a pin-on-disk tribometer reveals that, the film prepared on the roughest sample (Ra ~ 0.06 μm) exhibits a very short life span of about 20 cycles compared to the film that is prepared on a relatively smoother surface (Ra ~ 0.02 μm), which exhibits a life span of about 340,000 cycles. In order to investigate the origin of this improved property of the DLC film on the smoother surface, adhesive strength and hardness of the films were studied by using a micro-scratch tester and a Nano-indenter, respectively. The results suggest that the film prepared on the smoother surface exhibits better adhesion (higher critical load) and relatively higher hardness.

Methodology considering surface roughness in UV water disinfection reactors

2016 ◽  
Vol 70 (6) ◽  
Author(s):  
Tipu Sultan ◽  
Jin-Soo Cho
Keyword(s):  
Surface Roughness ◽  
Dose Distribution ◽  
Water Disinfection ◽  
Iterative Approximation ◽  
Roughness Effects ◽  
Ansys Fluent ◽  
Pipe Surface ◽  
Uv Reactor ◽  
Uv Lamp ◽  
Closed Conduit

AbstractWater disinfection making use of an ultraviolet (UV) reactor is an attractive procedure because it does not produce any by-products. In this work, the effects of pipe roughness on the performance of a closed-conduit water disinfection UV reactor were investigated. In order to incorporate the surface roughness effects, a simple, stable, highly accurate model, better than any iterative approximation, was adopted in the numerical simulations. The analysis was carried out on the basis of two performance indicators: reduction equivalent dose (RED) and system dose distribution. The analysis was performed using a commercial computational fluid dynamics (CFD) tool (ANSYS Fluent). The fluence rate within the UV reactor was calculated using UVCalc3D. The pipe surface roughness resulted in longer pathogen residence times and higher dose distribution among the pathogens. The effect of pipe surface roughness on RED depends on the Reynolds number and relative roughness. Pipe surface roughness plays an important role because UV reactors for water disinfection operate at moderate Reynolds numbers. In addition, the positioning of the UV lamp in the reactor plays an important role in determining the RED of the reactor. Search criteria for lamp-positioning are also proposed in the current work. The proposed CFD methodology can be used to analyse the performance of closed-conduit reactors for water disinfection by UV.

Investigation of Loss Impact From Production-Like Features in a Compressor Duct Under Engine Realistic Conditions

2017 ◽  
Author(s):  
Fredrik Wallin ◽  
Mark H. Ross ◽  
Max Rusche ◽  
Scott Morris ◽  
Steven Ray
Keyword(s):  
Surface Roughness ◽  
Total Pressure ◽  
Experimental Testing ◽  
Computational Grid ◽  
Test Facility ◽  
Pressure Probe ◽  
Cfd Analysis ◽  
Roughness Model ◽  
Geometrical Features ◽  
Real Geometry

An experimental and numerical investigation of the flow in a compressor duct with engine-realistic in-production features is presented in this paper. The experimental testing was conducted in the ND-FSCC test facility at University of Notre Dame, Indiana, USA. A baseline duct was also tested for back-to-back comparison. The ducts were heavily instrumented; duct inlet and exit flowfields were scanned using a five-hole pressure probe that provided total pressure, velocities and flow angles. Based on the five-hole probe total pressures, duct losses could be assessed. Furthermore the duct inlet boundary layers were traversed and turbulence intensity levels were assessed. For the CFD analysis of the production-like duct, a highly complex computational grid, resolving all the geometrical features present, was used. A previously validated surface roughness model was used to account for the cast aero-surfaces. Both experimental and numerical results show that there is a significant increase in loss for the production-like duct when compared to the baseline duct loss. The CFD results agree very well with experimental results for the baseline duct, which makes it possible to use the experimental data recorded for the production-like duct to validate CFD tools for real geometry effects, such as interface steps and surface roughness for example.

ROUGHNESS EFFECT OF DIFFERENT GEOMETRIES ON MICRO GAS FLOWS BY LATTICE BOLTZMANN SIMULATION

2009 ◽  
Vol 20 (06) ◽  
pp. 953-966 ◽  
Author(s):  
CHAOFENG LIU ◽  
YUSHAN NI ◽  
YONG RAO
Keyword(s):  
Surface Roughness ◽  
Lattice Boltzmann ◽  
Experimental Studies ◽  
Resistance Coefficient ◽  
Lattice Boltzmann Model ◽  
Gas Flows ◽  
Fractal Boundary ◽  
Roughness Effects ◽  
Roughness Effect ◽  
Relative Roughness

The roughness effects of the gas flows of nitrogen and helium in microchannels with various relative roughnesses and different geometries are studied and analyzed by a lattice Boltzmann model. The shape of surface roughness is simulated to be square, sinusoidal, triangular, and fractal. Numerical computations compared with theoretical and experimental studies show that the roughness geometry is an important factor besides the relative roughness in the study of the effects of surface roughness. The fractal boundary presents a higher influence on the velocity field and the resistance coefficient than other regular boundaries at the same Knudsen number and relative roughness. In addition, the effects of rarefaction, compressibility, and roughness are strongly coupled, and the roughness effect should not be ignored in studying rarefaction and compressibility of the microchannel as the relative roughness increases.

Hot Clamp Design for LMFBR Piping Systems

1993 ◽  
Vol 115 (1) ◽  
pp. 47-52
Author(s):  
T. Kobayashi ◽  
M. Tateishi
Keyword(s):  
Thermal Stresses ◽  
Cost Minimization ◽  
Large Diameter ◽  
Self Control ◽  
Test Facility ◽  
Thin Wall ◽  
Control Effect ◽  
Flexible Pipe ◽  
Pipe Surface ◽  
Thermal Transients

Thin-wall, large-diameter piping for liquid metal fast breeder reactor (LMFBR) plants can be subjected to significant thermal transients during reactor scrams. To reduce local thermal stresses, an insulated “cold” clamp was designed for the fast flux test facility and was also applied to some prototype reactors thereafter. However, the cost minimization of LMFBR requires much simpler designs. This paper presents a “hot” clamp design concept, which uses standard clamp halves directly attached to the pipe surface leaving an initial gap. Combinations of flexible pipe and rigid clamp achieved a self-control effect on clamp-induced pipe stresses due to the initial gap. A 3-D contact and inelastic history analysis were performed to verify the hot clamp concept. Considerations to reduce the initial stress at installation, to mitigate the clamp restraint on the pipe expansion during thermal shocks, and to maintain the pipe-clamp stiffness desired during a seismic event were discussed.

Batter Pile Static Load Test and Analysis

2012 ◽  
Vol 256-259 ◽  
pp. 1139-1143
Author(s):  
Li Lan Zhang ◽  
Yao Dong Wu
Keyword(s):  
Stress State ◽  
Static Load ◽  
Resistance Coefficient ◽  
Load Test ◽  
Soil Resistance ◽  
Test Results ◽  
Static Load Test ◽  
Foundation Soil ◽  
Load Analysis ◽  
Actual Stress

This paper through the test results and theoretical calculation of the batter pile static load, analysis of the actual stress state of cables, and according to the test results to determine the level of the foundation soil resistance coefficient ratio and allow level a transplant.

Quasi-Static Analysis of the Multi-Component Mooring Line for Suction Anchors

2010 ◽  
Author(s):  
Li-zhong Wang ◽  
Zhen Guo ◽  
Feng Yuan
Keyword(s):  
Static Analysis ◽  
Static Model ◽  
Ocean Currents ◽  
Original Position ◽  
Mooring Line ◽  
Soil Resistance ◽  
Two Dimensional ◽  
Accurate Analysis ◽  
Line Type

Multi-component taut mooring line is widely used to connect the floating facility to an embedded suction anchor to provide an effective motion limit. The functions of different components should be evaluated in order to optimize its anchoring performance. This paper presents a novel two-dimensional quasi-static model, which can calculate different combinations of line type, taking into account the effects of ocean currents, soil resistance and elastic elongation of mooring line. Accurate analysis is carried out to predict the responses of multi-component mooring line during pretension and in service. Especially, when the floating facility undergoes a series of motion away from its original position, the effect of vertical offset is studied in detail. Finally, based on the presented model, the functions of different components are throughly investigated and some useful conclusions are drawn.

Surface-Roughness Wakefield Measurements at Brookhaven Accelerator Test Facility

2002 ◽  
Vol 89 (17) ◽  
Author(s):  
F. Zhou ◽  
J. H. Wu ◽  
M. Babzien ◽  
I. Ben-Zvi ◽  
R. Malone ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Test Facility
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