scholarly journals SOME CONTRIBUTIONS TO HTDRAULIC MODEL EXPERIMENTS IN COASTAL ENGINEERING

1966 ◽  
Vol 1 (10) ◽  
pp. 72 ◽  
Author(s):  
Shoitiro Hayami ◽  
Tojiro Ishihara ◽  
Yuichi Iwagaki
Keyword(s):  
High Speed ◽  
Wind Wave ◽  
Coastal Engineering ◽  
Experimental Results ◽  
Prevention Research ◽  
Disaster Prevention ◽  
View Point ◽  
Model Experiments ◽  
Wave Channel ◽  
Disaster Prevention Research Institute

This paper presents some aspects of the hydraulic model experiments in coastal engineering made at the Ujigawa Hydraulic Laboratory, Disaster Prevention Research Institute, Kyoto University, including the experiments performed by using an estuary model basin and a high speed wind wave channel. In particular, the problems to which attentions should be paid from view point of similitude between model and prototype will be discussed in addition to the presentation of experimental results.

Whitecap coverage measurements in laboratory modeling of wind-wave interaction in presence of induced wave breaking

2021 ◽  
Author(s):  
Alexander Kandaurov ◽  
Yuliya Troitskaya ◽  
Vasiliy Kazakov ◽  
Daniil Sergeev
Keyword(s):  
Wave Breaking ◽  
Water Surface ◽  
High Speed ◽  
Wind Wave ◽  
Wave Train ◽  
Side Wall ◽  
Channel Cross Section ◽  
Whitecap Coverage ◽  
Wave Channel ◽  
Manual Processing

<p>Whitecap coverage were retrieved from high-speed video recordings of the water surface obtained on the unique laboratory faculty The Large Thermostratified Test Tank with wind-wave channel (cross-section from 0.7×0.7 to 0.7×0.9 m<sup>2</sup> at the end, 12 m fetch, wind velocity up to 35 m/s, U<sub>10</sub> up to 65 m/s). The wind wave was induced using a wave generator installed at the beginning of the channel (a submerged horizontal plate, frequency 1.042 Hz, amplitude 93 mm) working in a pulsed operation (three periods). Wave breaking was induced in working area by a submerged plate (1.2×0.7 m<sup>2</sup>, up to 12 depth, AOA -11,7°). Experiments were carried out for equivalent wind velocities U<sub>10</sub> from 17.8 to 40.1 m/s. Wire wave gauge was used to control the shape and phase of the incident wave.</p><p>To obtain the surface area occupied by wave breaking, we used two Cygnet CY2MP-CL-SN cameras with 50 mm lenses. The cameras are installed above the channel at a height of 273 cm from the water surface, separated by 89 cm. The image scale was 302 μm/px, the size of the image obtained from each camera is 2048x1088 px<sup>2</sup>, which corresponds to 619x328 mm<sup>2</sup> (the long side of the frame along the channel). The shooting was carried out with a frequency of 50 Hz, an exposure time of 3 ms, 250 frames were recorded for each wave train. To illuminate the image areas to the side of the measurement area, a diffuse screen was placed on the side wall, which was illuminated by powerful LED lamps to create a uniform illumination source covering the entire side wall of the section.</p><p>Using specially developed software for automatic detection of areas of wave breaking, the values of the whitecap coverage area were obtained. Automatic image processing was performed using morphological analysis in combination with manual processing of part of the frames for tweaking the algorithm parameters: for each mode, manual processing of several frames was performed, based on the results of which automatic algorithm parameters were selected to ensure that the resulting whitecap coverage corresponded. Comparison of images obtained from different angles made it possible to detect and exclude areas of glare on the surface from the whitecap coverage.</p><p>The repeatability of the created wave breakings allows carrying out independent measurements for the same conditions, for example the parameters of spray generation will give estimations of the average number of fragmentation events per unit area of the wave breaking area.</p><p>The work was supported by the RFBR grants 21-55-50005 and 20-05-00322 (conducting an experiment), President grant for young scientists МК-5503.2021.1.5 (software development) and the RSF grant No. 19-17-00209 (data processing).</p>

Congratulations! The Sixth JDR Award

2020 ◽  
Vol 15 (7) ◽  
pp. 815-815
Author(s):  
Haruo Hayashi ◽  
Keyword(s):  
Prevention Research ◽  
Disaster Prevention ◽  
Award Ceremony ◽  
Future Success ◽  
Disaster Prevention Research Institute ◽  
Research Institute

The Sixth JDR Award ceremony was held online due to COVID-19 on October 6, 2020 and a prize were given to Professor Masato Iguchi, Disaster Prevention Research Institute (DPRI), Kyoto University, Japan. We congratulate the winner and sincerely wish for future success.

scholarly journals 3 cm Doppler scatterometer with full polarization sensing.

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E.M. Zuikova ◽  
◽  
G.A. Baidakov ◽  
Y.A. Titchenko ◽  
M.B. Salin ◽  
...  
Keyword(s):  
Experimental Model ◽  
Frequency Modulation ◽  
Wind Wave ◽  
Experimental Results ◽  
Difference Frequency ◽  
Synchronous Detection ◽  
Wave Channel ◽  
X Band ◽  
The Cross ◽  
The Difference

The paper describes an experimental model of an X-band multi-polarization Doppler scatterometer developed at the IAP RAS with one antenna for receiving and transmitting, two generators with sinusoidal frequency modulation, slightly differing in frequency, and rigidly synchronized with each other. At the output of each of the two mixers, the co-polarizations are simultaneously distinguished in two quadratures at the beats and the cross-polarizations at the difference frequency. After filtering and synchronous detection, Doppler frequencies are obtained at all polarizations, which are then recorded on a computer for further processing. Experimental results obtained in the wind-wave channel of the large thermally stratified basin of the IAP RAS are presented.

Development of a New Tsunami Generator

2015 ◽  
Vol 802 ◽  
pp. 45-50
Author(s):  
Tetsuya Hiraishi
Keyword(s):  
Prevention Research ◽  
Water Tank ◽  
Disaster Prevention ◽  
Current Generator ◽  
Start Time ◽  
Tsunami Waves ◽  
Wave Generator ◽  
Disaster Prevention Research Institute ◽  
Wave Maker ◽  
A Current

A middle size experiental wave generator has been implemented is the Ujikawa Open Laboratory, Disaster Prevention Research Institute, Kyoto University. The generator is composed of a pistontype wave maker, a head strage water tank and a current generator to mainly reproduce long waves like tsunami and storm surge.The paper desribes severalexperimental series to predict the applicability of the generator to model tests. The three operating sysemes are capable to be controlled in one operating sysytem and start time is contorolled separately according with the target tsunami and storm surge profiles. A sharp tsunami profile is reproduced in adjusting the start timing of piston type wave maker and opening gates of head storage tunk. Any type of tsunami waves are reproduced in the generator and it becomes a strong tool to predict the effective of ”resiliency” of hardwares.

Yaw Galloping of a TLWP Platform Under High Speed Currents by Analytical Methods and its Comparison With Experimental Results

2017 ◽  
Author(s):  
Francisco Lamas ◽  
Miguel A. M. Ramirez ◽  
Antonio Carlos Fernandes
Keyword(s):  
High Speed ◽  
Production Systems ◽  
Experimental Tests ◽  
Experimental Results ◽  
Analytical Methodology ◽  
New Approach ◽  
Laboratory Facilities ◽  
Polynomial Curve ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses

Flow Induced Motions are always an important subject during both design and operational phases of an offshore platform life. These motions could significantly affect the performance of the platform, including its mooring and oil production systems. These kind of analyses are performed using basically two different approaches: experimental tests with reduced models and, more recently, with Computational Fluid Dynamics (CFD) dynamic analysis. The main objective of this work is to present a new approach, based on an analytical methodology using static CFD analyses to estimate the response on yaw motions of a Tension Leg Wellhead Platform on one of the several types of motions that can be classified as flow-induced motions, known as galloping. The first step is to review the equations that govern the yaw motions of an ocean platform when subjected to currents from different angles of attack. The yaw moment coefficients will be obtained using CFD steady-state analysis, on which the yaw moments will be calculated for several angles of attack, placed around the central angle where the analysis is being carried out. Having the force coefficients plotted against the angle values, we can adjust a polynomial curve around each analysis point in order to evaluate the amplitude of the yaw motion using a limit cycle approach. Other properties of the system which are flow-dependent, such as damping and added mass, will also be estimated using CFD. The last part of this work consists in comparing the analytical results with experimental results obtained at the LOC/COPPE-UFRJ laboratory facilities.

The Effect of Strain Rate on the Material Characteristics of Nickel-Based Superalloy Inconel 718

2007 ◽  
Vol 340-341 ◽  
pp. 283-288 ◽  
Author(s):  
Jung Han Song ◽  
Hoon Huh
Keyword(s):  
Dynamic Response ◽  
High Strain Rate ◽  
Strain Rate ◽  
Turbine Blade ◽  
Inconel 718 ◽  
High Speed ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Experimental Results ◽  
Stress Wave Propagation

The dynamic response of the turbine blade materials is indispensable for analysis of erosions of turbine blades as a result of impulsive loading associated with gas flow. This paper is concerned with the dynamic material properties of the Inconel 718 alloy which is widely used in the high speed turbine blade. The dynamic response at the corresponding level of the strain rate should be acquired with an adequate experimental technique and apparatus due to the inertia effect and the stress wave propagation. In this paper, the dynamic response of the Inconel 718 at the intermediate strain rate ranged from 1/s to 400/s is obtained from the high speed tensile test and that at the high strain rate above 1000/s is obtained from the split Hopkinson pressure bar test. The effects of the strain rate on the dynamic flow stress, the strain rate sensitivity and the failure elongation are evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 3000/s are interpolated in order to construct the constitutive relation that should be applied to simulate the dynamic behavior of the turbine blade made of the Inconel 718.

scholarly journals Researching on the Deterministic Channel Models for Urban Microcells Considering Diffraction Effects

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2143
Author(s):  
Chunzhi Hou ◽  
Zhensen Wu ◽  
Jiaji Wu ◽  
Yunhua Cao ◽  
Leke Lin ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
Wireless Channel ◽  
Experimental Results ◽  
Line Of Sight ◽  
Diffraction Effect ◽  
Channel Models ◽  
Wave Channel ◽  
Channel Parameters ◽  
Diffraction Effects ◽  
Ray Launching

Deterministic channel models, such as the three-dimensional (3D) ray launching method, can yield wireless channel parameters. In the non-line-of-sight (NLOS) propagation, the outdoor 3D ray launching method that considers diffraction effects is more accurate than the one that does not. While considering the diffraction effect, obtaining the diffraction point is challenging. This paper proposed a method for determining diffracted rays using the receiving sphere method in 3D ray launching. The diffraction point is determined using the shortest distance method between two straight lines, and the signal loss from the transmitting to receiving antennas is obtained. Furthermore, experiments on a millimeter wave in a microcell scenario were performed. The test results of the wireless channel parameters were compared with theoretical calculations. The results obtained via the 3D ray launching method that only considers the specular reflection and direct rays agree with the experimental results in the line-of-sight (LOS); furthermore, they generate larger errors compared with the experimental results in the NLOS. The results obtained via the 3D ray launching method that considers the direct ray, reflected rays, and diffracted rays agree with the experimental results both in the LOS and NLOS. Therefore, the 3D ray launching method that considers the diffraction effect can improve the prediction accuracy of the millimeter wave channel parameters in a microcell.

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