Experimental Study on 3D Scour Around an Embedded Submarine Pipeline Under Oblique Waves

2016 ◽  
Vol 11 (5) ◽  
pp. 989-994
Author(s):  
Dianqi Li ◽  
◽  
Yongzhou Cheng ◽  
Yu Yao ◽  
Xunxiao Li ◽  
...  
Keyword(s):  
Incident Angle ◽  
Embedment Depth ◽  
Submarine Pipeline ◽  
Rapid Phase ◽  
Oblique Waves ◽  
Wave Deformation ◽  
Scour Hole ◽  
Scouring Depth ◽  
Wave Angle ◽  
The Right

Wave deformation on a sloping seabed and the incident angle of waves greatly influence local submarine pipeline scour. Most previous studies on such scour considered wave deformation but not incident wave angle. Using regular waves with an incident angle of 45°, we investigated 3D scour around an embedded submarine pipeline under oblique waves in experiments. After examining wave deformation near the pipeline at different embedment depths, we analyzed how seabed scour evolved around the pipeline. Results of experiments showed that under oblique wave action, pipeline embedment depth affected wave height on both seaside and leeside of the pipeline. A 3D scour hole occurred under the pileline when the ratio of embedment depth to pipe diameter (e/D) was less than 1/4. Different forms of sand ripples also occurred on both sides as e/D changed. The embedment depth also determined the rate at which scour developed. The scour hole evolved in two distinct stages: rapid and slack. The scouring rate on the right side of the pipeline was greater than that on the left during the rapid phase, leading to an imbalance in scouring depth between the two sides.

Time Scale of Scour Below Submarine Pipeline Under Combined Waves and Currents With Oblique Incident Angle

2017 ◽  
Author(s):  
Zhipeng Zang ◽  
Guoqiang Tang ◽  
Liang Cheng
Keyword(s):  
Time Scale ◽  
Incident Angle ◽  
Normal Component ◽  
Normal Incidence ◽  
Local Scour ◽  
Embedment Depth ◽  
Buried Pipeline ◽  
Submarine Pipeline ◽  
Waves And Currents ◽  
Temporal And Spatial

Available formulae for the time scale of scour below a submarine pipeline are so far mainly restricted to waves-only and currents-only conditions with normal incidence and no burial of the pipeline. This paper presents experimental results on temporal and spatial developments of local scour below a partially buried pipeline under combined waves and currents with oblique incident angle. There are also some tests with waves-only and current-only conditions for validation purpose. All tests were conducted under live-bed conditions. The maximum Shields parameter is used to formulate the nondimensional time scale of local scour under combined waves and current conditions. The effects of flow incident angle and embedment depth on the time scale of scour were investigated. The results show that the time scale increases with the increase of incident angle and also increases with the increase of the embedment depth for combined waves and current conditions. The effective shields parameter is applied to account for the effect of the oblique incident angle based on the fact that both the normal component and the axial components of the flow contribute to the scour process when the currents or waves approach the pipeline with an oblique angle. It is found that the previously proposed empirical formula for time scale of scour for waves-only and current-only conditions, is also applicable to the combined waves and current conditions, if the maximum Shields parameter is used as the governed parameter in quantifying the time scale.

scholarly journals Cyclic GMP regulates activation of phosphoinositidase C by bradykinin in sensory neurons

1996 ◽  
Vol 316 (2) ◽  
pp. 539-544 ◽  
Author(s):  
Justine S. HARVEY ◽  
Gillian M. BURGESS
Keyword(s):  
Cyclic Gmp ◽  
Inhibitory Effect ◽  
Neonatal Rat ◽  
Drg Neurons ◽  
Rapid Phase ◽  
Surface Receptors ◽  
Similar Inhibitory Effect ◽  
Key Factor ◽  
The Right ◽  
Oxide Synthase

Prior exposure of cultured neonatal rat dorsal root ganglion (DRG) neurons to bradykinin resulted in marked attenuation of bradykinin-induced activation of phosphoinositidase C (PIC). The (logconcentration)–response curve for bradykinin-induced [3H]inositol trisphosphate ([3H]IP3) formation was shifted to the right and the maximum response was reduced. Bradykinin increases cyclic GMP (cGMP) in DRG neurons [Burgess, Mullaney, McNeill, Coote, Minhas and Wood (1989) J. Neurochem. 53, 1212–1218] and treatment of the neurons with dibutyryl cGMP (dbcGMP) had a similar, inhibitory, effect on bradykinin-induced [3H]IP3 formation. NG-Nitro-L-arginine (LNNA) blocked bradykinin-induced formation of cGMP. It prevented the functional uncoupling induced by pretreatment with bradykinin, but not the inhibitory effect of dbcGMP on [3H]IP3 formation. The ability of LNNA to prevent desensitization was reversed by excess L-arginine, indicating that its actions were mediated through inhibition of nitric oxide synthase. In addition to functional desensitization, exposure to bradykinin reduced the number of cell-surface receptors detected with [3H]bradykinin, without affecting its KD value for the remaining sites. In contrast to bradykinin, pretreatment with dbcGMP had no effect on either the KD or Bmax for [3H]bradykinin binding. This implies that the inhibitory effect of dbcGMP was downstream from the binding of bradykinin to its receptor and upstream of IP3 formation. The lack of effect of dbcGMP on [3H]bradykinin binding suggests that the decrease in receptor number induced by bradykinin was mediated by a different mechanism and was not a key factor in the rapid phase of desensitization in these cells.

Investigation of Prismatic Daylight Collectors With Different Apexes

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Allen Jong-Woei Whang ◽  
Chia-Min Lin ◽  
Shih-Chuan Yeh
Keyword(s):  
Ray Tracing ◽  
Intensity Distribution ◽  
Incident Angle ◽  
Apex Angle ◽  
Light Illumination ◽  
Natural Light ◽  
Relative Area ◽  
The Right ◽  
Ray Tracing Model

Prismatic elements are widely used in daylight illumination systems. The characteristics of the light that emerges from the surface of a right-angled prism vary with the apex of the prism and the incident angle of the sunshine illuminating the surface of the prismatic daylight collector. This paper investigates the effect of the apex angle of a right-angled prismatic collector on the performance of the collector using a matrix ray-tracing model and the edge principle. It was found that the majority of the light emerges from the hypotenuse of the right-angled prism when sunshine is incident on the surface of the prismatic daylight collector; furthermore, the flux of the light emerging from the hypotenuse that directs illuminating space decreases as the apex of the right-angled prism is increased. The intensity distribution of the majority of the light emerging from the hypotenuse of a right-angled prism can be used to guide the design of natural light illumination systems and enhance their performance. The percentage of light emerging from the hypotenuse decreases with the number of prismatic elements because the relative area of the emerging light that reaches the adjacent prism increases with the number of prismatic elements. The analysis of the relative area of the hypotenuse, where the emerging light that reaches the adjacent prism according to the edge ray principle shows that the total area is constant when the number of prismatic elements is greater than 10; an economical prismatic daylight collector can be realized with less material due to the larger number of smaller prisms with the same apex.

Mechanical Analysis on the Scour of Submarine Pipeline

2013 ◽  
Vol 834-836 ◽  
pp. 1369-1372
Author(s):  
Yan Han
Keyword(s):  
Critical Condition ◽  
Mechanical Analysis ◽  
Submarine Pipeline ◽  
Hole Depth ◽  
Balance Condition ◽  
Scour Hole

The reason about the scour of the submarine pipeline is researched in this paper. Through the mechanical analysis about the sand grain in the downstream of the pipe, the critical condition about of scour start is derived. The balance condition about the scour is studied. Through the mechanical analysis about the sand grain in the scour hole, the maximal scour hole depth is got.

Calculation on Dynamic Angle of Repose for Submarine Pipeline on Sandy Seabed

2011 ◽  
Vol 137 ◽  
pp. 210-214 ◽  
Author(s):  
Li Peng Yang ◽  
Bing Shi ◽  
Ya Kun Guo
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Vertical Axis ◽  
Angle Of Repose ◽  
Sand Particle ◽  
Submarine Pipeline ◽  
Deposition Model ◽  
Scour Hole ◽  
Calculation Results ◽  
Dynamic Angle

This paper investigates the dynamic angle of repose underneath the submarine pipeline. Using a sand deposition model, the analysis of forces acting on non-cohesive sand particle gives the formulas of dynamic angle of repose in the scour hole. The formulas for different scenarios are discussed and it is observed that the angle upstream the vertical axis of the pipe increases with the increase of sand Reynolds number. The angle downstream, however, shows a contrary trend. Besides, the angle upstream is bigger than that downstream. The comparison of the calculation results with the experimental data indicates that the formula predicts the angle of scour hole under a pipeline reasonably well.

scholarly journals Downbeat Nystagmus Secondary to Chiari I Malformation

2021 ◽  
Author(s):  
Marcelo Tognato Ximenes ◽  
Dan Mohamed Salman ◽  
Francisco Tomaz Meneses de Oliveira ◽  
Rubens José Gagliardi
Keyword(s):  
Chiari I Malformation ◽  
Moderate Intensity ◽  
Downbeat Nystagmus ◽  
Lateral Instability ◽  
Rapid Phase ◽  
Primary Position ◽  
Chiari Type 1 Malformation ◽  
Subcortical Region ◽  
Acute Changes ◽  
The Right

Context: Downbeat nystagmus are characterized by the rapid phase in the down direction in primary position of the eyes, in the most cases represents a cerebellar dysfunction, typically with injuries involving vestibulocerebellum (flocculus, paraflocculus, nodule and uvula), although most cases are due to primary lesions in the brain stem, usually involving paramedian tracts. This type of nystagmus is characteristic of craniocervical abnormalities, such as Chiari 1 malformation, also being seen in a wide variety of cerebellar diseases, including degenerative etiologies, toxic-metabolic and ischemic injury. Case report: A 45-year-old woman, who presented with dizziness started 6 years ago, related to rapid head movement, with progressive worsening, leading to difficulty in walking and a tendency to fall to the right, associated with mild to moderate intensity occipitonuchal headache, with improvement at rest and horizontal decubitus. Neurological examination showed downbeat nystagmus, intent tremor in the finger-to-nose-test, worse on the right arm, Romberg test presentes with anteroposterior and lateral instability, in addition to Tanden with bilateral lateropulsion, without other relevant changes. The magnetic resonance imaging showed platybasia and vertebrobasilar invagination, Chiari type 1 malformation with tonsillar herniation, without signs of cervical hydrosyringomyelia, signs of atrophy of both cerebellar hemispheres, a nonspecific nodule in the subcortical region of the left precuncle. Conclusion: The case described above is relevant to demonstrate that even in cases of acute changes in adulthood, screening for anatomical malformations in the posterior fossa should be considered.

Study on the Submarine Pipeline with Flexible Spoilers

2012 ◽  
Vol 501 ◽  
pp. 431-435 ◽  
Author(s):  
Yan Han
Keyword(s):  
Pressure Distribution ◽  
Pressure Difference ◽  
The Other ◽  
Submarine Pipeline ◽  
Hole Depth ◽  
New Methods ◽  
Physical Experiments ◽  
Scour Hole

Two new methods which use flexible spoilers to protect submarine pipelines are proposed. One is put flexible spoiler on the top of the pipe to make pipe self-buried. The other is put flexible spoiler under the pipe to stop the erosion under the pipe. Through physical experiments, the pressure distribution and scour hole around the submarine pipeline with flexible deflectors were studied. Experiment results point out that top flexible spoiler can increase the resistance of the pipe, increase the scour hole depth, accordingly make the pipeline be self-buried. The flexible spoiler under the pipe can reduce the pressure difference between both sides of the pipeline, diminish the scour hole depth obviously and even to stop scour.

Study of the Absorption Properties of Terahertz Wave in the Plasma Medium

2019 ◽  
Vol 74 (11) ◽  
pp. 1031-1036
Author(s):  
Jian-Xiao Liu ◽  
Ling-Hui Meng ◽  
Yu-Jie Liu ◽  
Jun-Li Feng ◽  
Hong-Wei Yang
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Incident Angle ◽  
Terahertz Wave ◽  
Absorption Peak ◽  
Plasma Medium ◽  
Absorption Properties ◽  
The Right ◽  
Magnetic Plasma ◽  
Frequency Area

AbstractIn this article, we study about the absorption properties of terahertz (THz) wave in the magnetic plasma medium. Terahertz wave has strong transmission in plasma. Generally speaking, with the increase in THz wave frequency, the transmission in plasma is stronger. Thus, we can consider raising carrier frequency to THz band to solve the communication of “blackout.” We found that the absorption in magnetic plasma is greatly affected by magnetic field. The changes on the power absorption coefficient of the two kinds of eigen wave in magnetic plasma vary with how the outside magnetic field, incident angle, and the thickness of the plasma are obtained. The study found that following the increase in magnetic field, the absorption of left circularly polarised waves (L-wave) gradually reduces, and the right circularly polarised waves (R-wave) will produce two absorption peaks, and these two absorption peaks move to high frequency as a whole. With the increase in incident angle and the high spectrum absorption of L-wave enhancement, the reflection between the two absorption peaks of R-wave broadens. The reflection area on the left side of the low-frequency area to absorb has a little change. The absorption on the right side of the high-frequency area is enhancement. With the increase in the plasma thickness, the L-wave absorption peak on the right side of the high-frequency area absorbs enhancement; the R-wave reflection between the two absorption peak areas is impregnability, the second absorption peak absorption enhancement on the right side of the high-frequency area. The study has shown the different absorption mechanisms of the L-wave and the R-wave and shown different absorption features in magnetic plasma.

scholarly journals Using a PIV Measurement System to Study the Occurrence of Bursting in the Flow Over a Movable Scour Hole Downstream of a Groundsill

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1396
Author(s):  
Cheng-Kai Chang ◽  
Jau-Yau Lu ◽  
Shi-Yan Lu ◽  
Kuo-Ting Hsiao ◽  
Dong-Sin Shih
Keyword(s):  
Particle Image ◽  
Hydraulic Structures ◽  
Exceedance Probability ◽  
Entrainment Rate ◽  
Hydraulic Characteristics ◽  
Flow Conditions ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Scour Hole ◽  
Scouring Depth

Generally, hydraulic structures are installed along with rivers in Taiwan to prevent erosion. The groundsill is one of the most common structures to protect the underlying riverbed. However, the occurrence of bursting during the process of scouring can intensify the disturbance of sediment in the bed, sometimes even causing hydraulic structures to collapse. This paper aimed to study the mechanisms of bursting, the effects of bursting, and the scouring exceedance probability of sediment movement. To study this topic, a particle image velocimetry (PIV) was used to measure the hydraulic characteristics of a scour hole under different flow conditions. The results showed that, firstly, the bursting and the sediment entrainment rate increased with time at the beginning. Secondly, when bursting occurred at the beginning stage of scouring, the averaged velocity of main flow was reduced by about 30% and the thickness of the riverbed was deepened by about 20%. Moreover, when scouring time was 15 min, at the location of maximum scouring depth, all the experimental groups carried the proximity values of the scouring exceedance probability that stuck to a range from 35% to 53% at the bursting stage. Therefore, the scouring exceedance probability of the bursting of the maximum scouring depth can be further applied to designs and to protect the foundation of hydraulic structures.

3D Scour of Submarine Pipeline at Touchdown Point: An Experimental Investigation

2011 ◽  
Author(s):  
Ambuj Dwivedi ◽  
Ying Min Low ◽  
Yee-Meng Chiew ◽  
Yushi Wu
Keyword(s):  
Experimental Study ◽  
Experimental Investigation ◽  
Pressure Gradient ◽  
Pressure Sensors ◽  
Embedment Depth ◽  
Submarine Pipeline ◽  
Preliminary Results ◽  
Steady Current ◽  
Laboratory Flume ◽  
Touchdown Point

This research presents the preliminary results obtained from the experimental study of 3D scour of submarine pipelines at its touchdown point. The results obtained from this study will increase our understanding on the mechanism of scour propagation at the touch down point of pipelines. Experiments were carried out inside a laboratory flume with piezoelectric miniature pressure sensors to measure pressure gradient across the pipe. Experiments were performed under unidirectional steady current with uniform sediments as bed. The scour pattern under initial embedment depth of pipeline is obtained. Preliminary result showed the importance of span-wise (longitudinal) scour in causing failure of the submarine pipelines.

Sign in / Sign up

Export Citation Format

Share Document