scholarly journals ANTIREFLECTIVE VERTICAL STRUCTURE EXTENDED FOR ATTENUATION OF LOW FREQUENCY WAVES

2012 ◽  
Vol 1 (33) ◽  
pp. 49
Author(s):  
Jose Alberto Gonzalez-Escriva ◽  
Josep Ramon MEDINA
Keyword(s):  
Large Scale ◽  
Vertical Structure ◽  
Wave Reflection ◽  
Wind Waves ◽  
Low Frequency ◽  
Scale Model ◽  
Frequency Wave ◽  
Large Scale Model ◽  
Multiple Unit ◽  
Low Frequency Waves

A new maritime vertical structure was designed to improve the antireflective performance for wave reflection of wind waves and oscillations associated with intense storms, resonance waves in port basins, etc. Multiple unit chambers formed with long cell circuits (Medina et al., 2010) are responsible for the low frequency wave absorption that was studied through large-scale model testing.

Low-Frequency Oscillations Within the Hambantota Port During the Southwest Monsoon, 2019

2020 ◽  
Author(s):  
Zhenjun Zheng ◽  
Xiaozhou Ma ◽  
Xuezhi Huang ◽  
Yujin Dong ◽  
Guohai Dong
Keyword(s):  
Wind Waves ◽  
Low Frequency ◽  
Southwest Monsoon ◽  
Long Waves ◽  
Frequency Wave ◽  
Low Frequency Oscillations ◽  
Mild Slope Equation ◽  
Spectrum Density ◽  
Forcing Mechanisms ◽  
Low Frequency Waves

Abstract Long waves with periods greater than tens of seconds propagating into a harbor may be trapped and significantly amplified, thereby resulting in detrimental effects on port operations. The water surface elevation in the Hambantota Port, Sri Lanka, was measured to investigate the low-frequency oscillations and their forcing mechanisms. Results show that the port is protected well from short waves with periods less than 30 s; however, the protection against long waves with periods larger than 30 s is inadequate. The spectral analyses identified four dominant periods within the low-frequency wave range. Modal analysis based on the extended mild-slope equation shows that the measured spectrum density for some dominant periods is low because the measurement point is close to the corresponding modal lines. Correlation analysis shows that low-frequency oscillations inside the Hambantota Port are excited directly by the low-frequency waves contained within the incident waves. The low-frequency waves outside the Hambantota Port are generated from the higher-frequency gravity waves (swell and wind waves) due to nonlinear interactions. Empirical formula is adopted to estimate the low-frequency wave height outside the Hambantota Port.

Multiscale Interactions in an Idealized Walker Cell: Simulations with Sparse Space–Time Superparameterization

2015 ◽  
Vol 143 (2) ◽  
pp. 563-580 ◽  
Author(s):  
Joanna Slawinska ◽  
Olivier Pauluis ◽  
Andrew J. Majda ◽  
Wojciech W. Grabowski
Keyword(s):  
Large Scale ◽  
Computational Cost ◽  
Low Frequency ◽  
Space Time ◽  
Scale Model ◽  
Moist Convection ◽  
Computationally Efficient ◽  
Convective Systems ◽  
Large Scale Model ◽  
Walker Cell

Abstract This paper discusses the sparse space–time superparameterization (SSTSP) algorithm and evaluates its ability to represent interactions between moist convection and the large-scale circulation in the context of a Walker cell flow over a planetary scale two-dimensional domain. The SSTSP represents convective motions in each column of the large-scale model by embedding a cloud-resolving model, and relies on a sparse sampling in both space and time to reduce computational cost of explicit simulation of convective processes. Simulations are performed varying the spatial compression and/or temporal acceleration, and results are compared to the cloud-resolving simulation reported previously. The algorithm is able to reproduce a broad range of circulation features for all temporal accelerations and spatial compressions, but significant biases are identified. Precipitation tends to be too intense and too localized over warm waters when compared to the cloud-resolving simulations. It is argued that this is because coherent propagation of organized convective systems from one large-scale model column to another is difficult when superparameterization is used, as noted in previous studies. The Walker cell in all simulations exhibits low-frequency variability on a time scale of about 20 days, characterized by four distinctive stages: suppressed, intensification, active, and weakening. The SSTSP algorithm captures spatial structure and temporal evolution of the variability. This reinforces the confidence that SSTSP preserves fundamental interactions between convection and the large-scale flow, and offers a computationally efficient alternative to traditional convective parameterizations.

scholarly journals STABILITY OF INTERLOCKED PATTERN PLACED BLOCK REVETMENTS

2012 ◽  
Vol 1 (33) ◽  
pp. 46 ◽  
Author(s):  
Fabian Gier ◽  
Holger Schüttrumpf ◽  
Jens Mönnich ◽  
Jentsje Van der Meer ◽  
Matthias Kudella ◽  
...  
Keyword(s):  
Large Scale ◽  
Wind Waves ◽  
Scale Model ◽  
Test Results ◽  
Friction Forces ◽  
Ship Waves ◽  
Pull Out ◽  
Large Scale Model ◽  
The Individual ◽  
Hydraulic Stability

Revetments protect the shorelines of coasts, estuaries and rivers against wind waves, ship waves, currents and ice attacks. The resistance of revetments basically depends on the properties of the cover layer. In the case of an interlocked pattern placed revetment the resistance essentially depends on the weight of the individual blocks, the friction forces and the interlocking force. In this study, extensive large scale model tests have been performed to assess the hydraulic stability of interlocked pattern placed revetments. The study shows test results due to deformations, wave loading and pull-out tests. Overall, the experimental results show a significant increase in the structural stability of the revetment against wave attack due to the interlocking system compared to traditional revetment elements.

RANCANG BANGUN PERANGKAT EKSPERIMENTASI PROSES PIROLISIS BIOMASA GELOMBANG MIKRO

2013 ◽  
Vol 14 (2) ◽  
Author(s):  
Noor Fachrizal
Keyword(s):  
Large Scale ◽  
Continuous Model ◽  
Biomass Energy ◽  
Scale Model ◽  
Small Scale ◽  
Laboratory Apparatus ◽  
Liquid Form ◽  
Large Scale Model ◽  
Bio Oil ◽  
Pyrolysis Of Biomass

Biomass such as agriculture waste and urban waste are enormous potency as energy resources instead of enviromental problem. organic waste can be converted into energy in the form of liquid fuel, solid, and syngas by using of pyrolysis technique. Pyrolysis process can yield higher liquid form when the process can be drifted into fast and flash response. It can be solved by using microwave heating method. This research is started from developing an experimentation laboratory apparatus of microwave-assisted pyrolysis of biomass energy conversion system, and conducting preliminary experiments for gaining the proof that this method can be established for driving the process properly and safely. Modifying commercial oven into laboratory apparatus has been done, it works safely, and initial experiments have been carried out, process yields bio-oil and charcoal shortly, several parameters are achieved. Some further experiments are still needed for more detail parameters. Theresults may be used to design small-scale continuous model of productionsystem, which then can be developed into large-scale model that applicable for comercial use.

Effect of an Oscillating Flow Direction on Leading Edge Heat Transfer

1984 ◽  
Vol 106 (1) ◽  
pp. 222-228 ◽  
Author(s):  
M. L. Marziale ◽  
R. E. Mayle
Keyword(s):  
Heat Transfer ◽  
Strouhal Number ◽  
Large Scale ◽  
Flow Direction ◽  
Leading Edge ◽  
Periodic Variation ◽  
Scale Model ◽  
Transfer Rates ◽  
Large Scale Model ◽  
Turbulence Length

An experimental investigation was conducted to examine the effect of a periodic variation in the angle of attack on heat transfer at the leading edge of a gas turbine blade. A circular cylinder was used as a large-scale model of the leading edge region. The cylinder was placed in a wind tunnel and was oscillated rotationally about its axis. The incident flow Reynolds number and the Strouhal number of oscillation were chosen to model an actual turbine condition. Incident turbulence levels up to 4.9 percent were produced by grids placed upstream of the cylinder. The transfer rate was measured using a mass transfer technique and heat transfer rates inferred from the results. A direct comparison of the unsteady and steady results indicate that the effect is dependent on the Strouhal number, turbulence level, and the turbulence length scale, but that the largest observed effect was only a 10 percent augmentation at the nominal stagnation position.

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