Experimental Investigation of the Nonlinear Effects on the Vertical Motions and Loads of a Containership in Regular Waves

2004 ◽  
Vol 48 (02) ◽  
pp. 118-147 ◽  
Author(s):  
N. Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Experimental Investigation ◽  
Wave Amplitude ◽  
Nonlinear Effects ◽  
Wave Frequency ◽  
Experimental Program ◽  
Regular Waves ◽  
Cross Sectional ◽  
Nonlinear Characteristics ◽  
Time Histories ◽  
Vertical Accelerations

The nonlinear vertical responses of a containership advancing in regular waves are investigated experimentally. The paper presents the results of an experimental program carried out in a seakeeping tank with a model of the ITTC S-175 containership in head regular waves. All the wave frequency ranges of interest were tested, and for each wave frequency several wave amplitudes were used ranging from small to large amplitude. In this way the influence of the wave amplitude on the nonlinear characteristics of the responses was assessed. The measured responses include the absolute and relative motions, vertical accelerations, and cross-sectional loads at midship and ¼ Lpp from the forward perpendicular. Strong nonlinear effects were detected, especially on the loads, which can be identified by the variation of the transfer function with the wave amplitude, the asymmetry of the time histories, and the presence of higher harmonics.

Experimental Investigation of the Nonlinear Effects on the Statistics of Vertical Motions and Loads of a Containership in Irregular Waves

2004 ◽  
Vol 48 (02) ◽  
pp. 148-167 ◽  
Author(s):  
N. Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Probability Distributions ◽  
Nonlinear Behavior ◽  
Nonlinear Effects ◽  
Rayleigh Distribution ◽  
Irregular Waves ◽  
Cross Sectional ◽  
Wave Heights ◽  
Vertical Accelerations

The paper presents the results of an experimental investigation of the nonlinear effects on the vertical motions and loads on a containership model advancing in irregular waves. The experimental data are compared with numerical results from a nonlinear time domain strip method. The tests were carried out in a seakeeping tank using three sea states with significant wave heights of 4.2 m, 6.1 m, and 9.9 m, thus including very severe conditions. The measured responses include the absolute and relative motions, vertical accelerations, and cross-sectional loads at midship and ¼ Lpp from the forward perpendicular. The statistics of the experimental records demonstrate partly the nonlinear behavior of the responses, especially of the structural loads. The probability distributions of the positive and negative peaks show that the heave and pitch motions are only slightly asymmetric and their distributions compare well with the Rayleigh distribution. The vertical loads present distributions of peaks that are highly asymmetric and deviate from the Rayleigh distribution. Comparisons between simulated results and experimental data show that the numerical model is able to represent the nonlinear characteristics of the responses.

Water Entry of a Wedge with Finite Deadrise Angle

2001 ◽  
Vol 46 (01) ◽  
pp. 39-51 ◽  
Author(s):  
O. M. Faltinsen ◽  
Jin Wu
Keyword(s):  
Experimental Data ◽  
Probability Distributions ◽  
Nonlinear Behavior ◽  
Nonlinear Effects ◽  
Rayleigh Distribution ◽  
Irregular Waves ◽  
Cross Sectional ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Vertical Accelerations

The paper presents the results of an experimental investigation of the nonlinear effects on the vertical motions and loads on a containership model advancing in irregular waves. The experimental data are compared with numerical results from a nonlinear time domain strip method. The tests were carried out in a seakeeping tank using three sea states with significant wave heights of 4.2 m, 6.1 m, and 9.9 m, thus including very severe conditions. The measured responses include the absolute and relative motions, vertical accelerations, and cross-sectional loads at midship and ¼ Lpp from the forward perpendicular. The statistics of the experimental records demonstrate partly the nonlinear behavior of the responses, especially of the structural loads. The probability distributions of the positive and negative peaks show that the heave and pitch motions are only slightly asymmetric and their distributions compare well with the Rayleigh distribution. The vertical loads present distributions of peaks that are highly asymmetric and deviate from the Rayleigh distribution. Comparisons between simulated results and experimental data show that the numerical model is able to represent the nonlinear characteristics of the responses.

Assessment of sand stabilization potential of a plant-derived biomass

2016 ◽  
Vol 23 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Dunja Perić ◽  
Paul A. Bartley ◽  
Lawrence Davis ◽  
Ali Ulvi Uzer ◽  
Cahit Gürer
Keyword(s):  
Area Ratio ◽  
Cross Sectional Area ◽  
Experimental Program ◽  
Early Age ◽  
Shear Stresses ◽  
Sectional Area ◽  
Cross Sectional ◽  
Near Surface ◽  
Total Cross Sectional Area ◽  
Dry Sand

AbstractLignin is a coproduct of biofuel and paper industries, which exhibits binding qualities when mixed with water. Lignin is an ideal candidate for a sustainable stabilization of unpaved roads. To this end, an experimental program was devised and carried out to quantify effects of lignin on compaction and early age shear strength behaviors of sand. Samples were prepared by mixing a particular type of coproduct called calcium lignosulfonate (CaL) with sand and water. Based on the extensive analyses of six series of strength tests, it was found that a normalized cohesion increased with an increasing normalized areas ratio. Normalizations were carried out by dividing the cohesion and area ratio by gravimetric CaL content whereby the area ratio was obtained by dividing the portion of the cross-sectional area occupied with lignosulfonate-water (CaL-W) paste by the total cross-sectional area. While the increase in the normalized cohesion eventually leveled out, the cohesion peaked at 6% of CaL. Thus, sand-CaL-water (S-CaL-W) mixes sustained larger shear stresses than dry sand for a range of normal stresses below the limiting normal stress. Consequently, the early age behavior indicates that adding CaL-W to sand is clearly beneficial in the near-surface applications in dry sand.

Diffraction Waves About an Advancing Wedge Model in Deep Water

1990 ◽  
Vol 34 (02) ◽  
pp. 105-122
Author(s):  
Hideaki Miyata ◽  
Makoto Kanai ◽  
Noriaki Yoshiyasu ◽  
Yohichi Furuno
Keyword(s):  
Numerical Simulation ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Wedge Angle ◽  
Wave Pattern ◽  
Regular Waves ◽  
Nonlinear Characteristics ◽  
Diffracted Waves ◽  
Nonlinear Features ◽  
Incident Waves

The diffraction of regular waves by advancing wedge models is studied both experimentally and numerically. The nonlinear features of diffracted waves are visualized by wave pattern pictures and the formation is analyzed by the grid-projection method. The experimental observation indicates that the diffracted waves have a number of nonlinear characteristics similar to shock waves due to the interaction of incident waves with the advancing obstacle in the flow-field caused by the advancing motion. Bow waves of both oblique type and normal detached type are observed at remarkably lower Froude numbers than in the case of a ship in steady advance motion. Their occurrence systematically depends on the Froude number and the wedge angle. The numerical simulation of this phenomenon by a finite-difference method shows approximate agreement with the experimental results.

scholarly journals Experimental Investigation of a Rectangular Airlift Pump

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
I. I. Esen
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Rectangular Cross Section ◽  
Hydraulic Performance ◽  
Experimental Program ◽  
Empirical Equations ◽  
Airlift Pump

Hydraulic performance of an airlift pump having a rectangular cross-section 20 mm × 80 mm was investigated through an experimental program. The pump was operated at six different submergence ratios and the liquid flow rate was measured at various flowrates of air injected. The effectiveness of the pump, defined as the ratio of the mass of liquid pumped to the mass of air injected, was determined as a function of the mass of air injected for different submergence ratios. Results obtained were compared with those for circular airlift pumps using an analytical model for circular pumps. Effectiveness of the rectangular airlift pump was observed to be comparable to that of the circular pumps. Hydraulic performance of the rectangular airlift pump investigated was then described by a set of semilogarithmic empirical equations.

Experimental Investigation of Vortex-Induced Vibrations of a Flexibly Mounted Circular Cylinder in Combined Current and Wave Flows

2021 ◽  
Author(s):  
Pierre-Adrien Opinel ◽  
Narakorn Srinil
Keyword(s):  
Experimental Investigation ◽  
Circular Cylinder ◽  
Cross Flow ◽  
Wave Flow ◽  
Regular Wave ◽  
Regular Waves ◽  
Vortex Induced Vibrations ◽  
Flow Frequency ◽  
The Cross ◽  
Wave Flows

Abstract This paper presents the experimental investigation of vortex-induced vibrations (VIV) of a flexibly mounted circular cylinder in combined current and wave flows. The same experimental setup has previously been used in our previous study (OMAE2020-18161) on VIV in regular waves. The system comprises a pendulum-type vertical cylinder mounted on two-dimensional springs with equal stiffness in in-line and cross-flow directions. The mass ratio of the system is close to 3, the aspect ratio of the tested cylinder based on its submerged length is close to 27, and the damping in still water is around 3.4%. Three current velocities are considered in this study, namely 0.21 m/s, 0.29 m/s and 0.37 m/s, in combination with the generated regular waves. The cylinder motion is recorded using targets and two Qualisys cameras, and the water elevation is measured utilizing a wave probe. The covered ranges of Keulegan-Carpenter number KC are [9.6–35.4], [12.8–40.9] and [16.3–47.8], and the corresponding ranges of reduced velocity Vr are [8–16.3], [10.6–18.4] and [14–20.5] for the cases with current velocity of 0.21 m/s, 0.29 m/s and 0.37 m/s, respectively. The cylinder response amplitudes, trajectories and vibration frequencies are extracted from the recorded motion signals. In all cases the cylinder oscillates primarily at the flow frequency in the in-line direction, and the in-line VIV component additionally appears for the intermediate (0.29 m/s) and high (0.37 m/s) current velocities. The cross-flow oscillation frequency is principally at two or three times the flow frequency in the low current case, similar to what is observed in pure regular waves. For higher current velocities, the cross-flow frequency tends to lock-in with the system natural frequency, as in the steady flow case. The inline and cross-flow cylinder response amplitudes of the combined current and regular wave flow cases are eventually compared with the amplitudes from the pure current and pure regular wave flow cases.

Experimental Study on the Influence of Hull Spacing on Hard-Chine Catamaran Motions

2001 ◽  
Vol 45 (03) ◽  
pp. 216-227
Author(s):  
R. Centeno ◽  
K. S. Varyani ◽  
C. Guedes Soares
Keyword(s):  
Experimental Study ◽  
Cross Flow ◽  
Experimental Program ◽  
Two Dimensional ◽  
Regular Waves ◽  
Viscous Forces ◽  
Motion Responses ◽  
Resonance Frequencies ◽  
Flow Drag ◽  
Wave Induced

An experimental program was performed with hard-chine catamaran models in regular waves. The distance between the demi-hulls of the models was changed to assess its effects on the wave-induced motions. The results allowed the study of some aspects related to catamaran motions, like the interference between the hulls and resonance frequencies. The experimental results are compared with calculations performed with a recently developed code based on a two-dimensional potential flow theory in which viscous forces are included through a cross-flow drag approach. The effect of the hull distance in the heave and pitch motion responses and the importance of the viscous forces in such hull configurations are shown.

A Network Perspective on the Relationship Between Moderate to Vigorous Physical Activity and Fundamental Motor Skills in Early Childhood

2021 ◽  
pp. 1-8
Author(s):  
Thaynã Alves Bezerra ◽  
Paulo Felipe Ribeiro Bandeira ◽  
Anastácio Neco de Souza Filho ◽  
Cain Craig Truman Clark ◽  
Jorge Augusto Pinto Silva Mota ◽  
...  
Keyword(s):  
Physical Activity ◽  
Early Childhood ◽  
Vigorous Physical Activity ◽  
Cross Sectional Study ◽  
Older Children ◽  
Activity Data ◽  
Cross Sectional ◽  
Nonlinear Characteristics ◽  
Main Variable ◽  
The Relationship

Background: The relationship between moderate to vigorous physical activity (MVPA) and fundamental motor skill (FMS) is inconsistent in early childhood, due to its complex and nonlinear characteristics. This study aimed to analyze the nonlinear relationships between MVPA, FMS, body mass index (BMI), sex, and age in preschoolers. Methods: This cross-sectional study with preschoolers (n = 204; 4.0 [0.8] y old; 99 boys), provided objective physical activity data, FMS assessments, and BMI. The associations between MVPA, FMS, BMI, sex, and age were explored using the network analysis (RStudio and qgraph). Results: Boys were more motor competent than girls in all FMS skills, while girls were more active than boys during the weekend. Older children were less active than their younger peers during these days. MVPA is weak and differently related to each FMS, and the leap skill emerged with the highest betweenness and strength values in the network. Conclusions: For the assessed preschoolers, when considering BMI, age, and sex, the relationships between MVPA and FMS are inconsistent, and leap emerged as the main variable. During early childhood, these variables are connected as part of a complex system in which each skill has a dynamic role within the emerging pattern.

scholarly journals INTERACTION OF WAVES AND A TURBULENT CURRENT

1976 ◽  
Vol 1 (15) ◽  
pp. 22 ◽  
Author(s):  
J.D.A. Van Hoften ◽  
S. Karaki
Keyword(s):  
Experimental Investigation ◽  
Gravity Waves ◽  
Wave Amplitude ◽  
Current System ◽  
Bottom Shear Stress ◽  
Wave Dissipation ◽  
Wave Channel ◽  
Amplitude Attenuation ◽  
Current Interaction ◽  
The Waves

An experimental investigation was made to study wave-current interaction. Wave amplitude attenuation was measured along a laboratory wave channel to compare wave dissipation with and without flow. Mean, wave, and turbulent velocities were also measured to determine the modifications of the flow imposed by the gravity waves propogating with the current. The process of energy transfer in the wave current system was studied. Energy was found to be extracted from the waves, diffused downward and dissipated by an increase in bottom shear stress.

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