Experimental Investigation of Wave Load and Run-up on the Composite Bucket Foundation Influenced by Regular Waves

2021 ◽  
Vol 20 (2) ◽  
pp. 271-284
Author(s):  
Tongshun Yu ◽  
Zishuai Zhao ◽  
Zhongyu Shi ◽  
Yu Xu
Keyword(s):  
Experimental Investigation ◽  
Wave Load ◽  
Regular Waves ◽  
Bucket Foundation ◽  
Run Up

Experimental investigation on the shock-wave load attenuation by geometrical means

Shock Waves ◽  
2009 ◽  
Vol 20 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Shachar Berger ◽  
Oren Sadot ◽  
Gabi Ben-Dor
Keyword(s):  
Shock Wave ◽  
Experimental Investigation ◽  
Wave Load

Effective Power and Speed Loss of Underwater Vehicles in Close Proximity to Regular Waves

2017 ◽  
Author(s):  
Stefan Daum ◽  
Martin Greve ◽  
Renato Skejic
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Water Waves ◽  
Underwater Vehicles ◽  
Total Resistance ◽  
Wave Load ◽  
Regular Waves ◽  
Effective Power ◽  
Close Proximity ◽  
Deep Water Waves

The present study is focused on performance issues of underwater vehicles near the free surface and gives insight into the analysis of a speed loss in regular deep water waves. Predictions of the speed loss are based on the evaluation of the total resistance and effective power in calm water and preselected regular wave fields w.r.t. the non-dimensional wave to body length ratio. It has been assumed that the water is sufficiently deep and that the vehicle is operating in a range of small to moderate Froude numbers by moving forward on a straight-line course with a defined encounter angle of incident regular waves. A modified version of the Doctors & Days [1] method as presented in Skejic and Jullumstrø [2] is used for the determination of the total resistance and consequently the effective power. In particular, the wave-making resistance is estimated by using different approaches covering simplified methods, i.e. Michell’s thin ship theory with the inclusion of viscosity effects Tuck [3] and Lazauskas [4] as well as boundary element methods, i.e. 3D Rankine source calculations according to Hess and Smith [5]. These methods are based on the linear potential fluid flow and are compared to fully viscous finite volume methods for selected geometries. The wave resistance models are verified and validated by published data of a prolate spheroid and one appropriate axisymmetric submarine model. Added resistance in regular deep water waves is obtained through evaluation of the surge mean second-order wave load. For this purpose, two different theoretical models based on potential flow theory are used: Loukakis and Sclavounos [6] and Salvesen et. al. [7]. The considered theories cover the whole range of important wavelengths for an underwater vehicle advancing in close proximity to the free surface. Comparisons between the outlined wave load theories and available theoretical and experimental data were carried out for a submerged submarine and a horizontal cylinder. Finally, the effective power and speed loss are discussed from a submarine operational point of view where the mentioned parameters directly influence mission requirements in a seaway. All presented results are carried out from the perspective of accuracy and efficiency within common engineering practice. By concluding current investigations in regular waves an outlook will be drawn to the application of advancing underwater vehicles in more realistic sea conditions.

scholarly journals Experimental Investigation of Adaptive Control Applied to HSFD Supported Rotors

1999 ◽  
Author(s):  
A. El-Shafei ◽  
M. El-Hakim
Keyword(s):  
Experimental Investigation ◽  
Adaptive Control ◽  
Reference Model ◽  
Computer Control ◽  
Adaptive Controller ◽  
Superior Performance ◽  
Order System ◽  
Squeeze Film ◽  
Run Up ◽  
Model Reference Adaptive

This paper describes the experimental application of adaptive control to Hybrid Squeeze Film Damper (HSFD) supported rotors. The HSFD has been shown to be an adaptive damper capable of providing infinite damper configurations between short and long damper configurations. Previously, theoretical investigations of the adaptive control of HSFD concentrated on the development of the model reference adaptive control (MRAC) method, as well as development of a nonlinear reference model. Simulations of the performance of the adaptive controller during run-up and coast-down indicated the superior performance of the adaptive controller. In this paper, the adaptive controller is tested on a multi-mode rotor. A test rig is designed and developed using computer control. A simple reference model is investigated consisting of a second order system. Three forms for adaptation gain are studied. The results of the experimental investigation illustrated the performance capabilities of the adaptive controller applied to the HSFD, and moreover indicated the possibility of simple design for the adaptive controller.

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 Investigation on the Dynamic Response of an Internal Turret Moored FPSO System Under Sea Waves

2003 ◽  
Author(s):  
T. Rajesh Kannah ◽  
R. Natarajan
Keyword(s):  
Experimental Investigation ◽  
Dynamic Behaviour ◽  
Operating Conditions ◽  
Scale Model ◽  
Sea Waves ◽  
Regular Waves ◽  
Wave Flume ◽  
Load Cells ◽  
Mooring Forces ◽  
Rotary Type

An experimental investigation on the dynamic behaviour of a typical internal turret moored FPSO system with a turret located at midships position is reported. A 1:100 scale model of 140000t DWT turret moored FPSO system was tested under regular waves for three operating conditions i.e. 40%DWT, 70%DWT and 100%DWT in a 2m wide wave flume at a water depth of 1m for the wave frequencies from 0.55Hz to 1.25Hz in steps of 0.04Hz. The motions were measured by rotary type potentiometers and specially ring type load cells were used to measure the mooring forces. The model tests results are analysed and presented with discussions in this paper.

scholarly journals Nonlinear run-ups of regular waves on sloping structures

2012 ◽  
Vol 12 (12) ◽  
pp. 3811-3820 ◽  
Author(s):  
T.-W. Hsu ◽  
S.-J. Liang ◽  
B.-D. Young ◽  
S.-H. Ou
Keyword(s):  
Boussinesq Equations ◽  
Irregular Waves ◽  
Coastal Structures ◽  
Regular Waves ◽  
Wave Flume ◽  
Coastal Risk ◽  
Run Up ◽  
Two Parameters ◽  
Prediction Capability ◽  
Good Agreement

Abstract. For coastal risk mapping, it is extremely important to accurately predict wave run-ups since they influence overtopping calculations; however, nonlinear run-ups of regular waves on sloping structures are still not accurately modeled. We report the development of a high-order numerical model for regular waves based on the second-order nonlinear Boussinesq equations (BEs) derived by Wei et al. (1995). We calculated 160 cases of wave run-ups of nonlinear regular waves over various slope structures. Laboratory experiments were conducted in a wave flume for regular waves propagating over three plane slopes: tan α =1/5, 1/4, and 1/3. The numerical results, laboratory observations, as well as previous datasets were in good agreement. We have also proposed an empirical formula of the relative run-up in terms of two parameters: the Iribarren number ξ and sloping structures tan α. The prediction capability of the proposed formula was tested using previous data covering the range ξ ≤ 3 and 1/5 ≤ tan α ≤ 1/2 and found to be acceptable. Our study serves as a stepping stone to investigate run-up predictions for irregular waves and more complex geometries of coastal structures.

Experimental Investigation of Adaptive Control Applied to HSFD Supported Rotors

2000 ◽  
Vol 122 (4) ◽  
pp. 685-692 ◽  
Author(s):  
A. El-Shafei ◽  
M. El-Hakim
Keyword(s):  
Experimental Investigation ◽  
Adaptive Control ◽  
Reference Model ◽  
Computer Control ◽  
Adaptive Controller ◽  
Superior Performance ◽  
Order System ◽  
Squeeze Film ◽  
Run Up ◽  
Model Reference Adaptive

This paper describes the experimental application of adaptive control to Hybrid Squeeze Film Damper (HSFD) supported rotors. The HSFD has been shown to be an adaptive damper capable of providing infinite damper configurations between short and long damper configurations. Previously, theoretical investigations of the adaptive control of HSFD concentrated on the development of the model reference adaptive control (MRAC) method, as well as development of a nonlinear reference model. Simulations of the performance of the adaptive controller during run-up and coast-down indicated the superior performance of the adaptive controller. In this paper, the adaptive controller is tested on a multi-mode rotor. A test rig is designed and developed using computer control. A simple reference model is investigated consisting of a second order system. Three forms for adaptation gain are studied. The results of the experimental investigation illustrated the performance capabilities of the adaptive controller applied to the HSFD, and moreover indicated the possibility of simple design for the adaptive controller. [S0742-4795(00)01603-3]

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