Bag Bioreactor Based on Wave-Induced Motion: Characteristics and Applications

2009 ◽  
pp. 55-87 ◽  
Author(s):  
Regine Eibl ◽  
Sören Werner ◽  
Dieter Eibl
Keyword(s):  
Induced Motion ◽  
Motion Characteristics ◽  
Wave Induced

The effect of waves on subgrid-scale stresses, dissipation and model coefficients in the coastal ocean bottom boundary layer

2007 ◽  
Vol 583 ◽  
pp. 133-160 ◽  
Author(s):  
W. A. M. NIMMO SMITH ◽  
J. KATZ ◽  
T. R. OSBORN
Keyword(s):  
Dynamic Model ◽  
Energy Flux ◽  
Correlation Coefficients ◽  
Reynolds Numbers ◽  
Subgrid Scale ◽  
Mean Flow ◽  
Low Reynolds Numbers ◽  
Induced Motion ◽  
Stress Models ◽  
Wave Induced

Six sets of particle image velocimetry (PIV) data from the bottom boundary layer of the coastal ocean are examined. The data represent periods of high, moderate and weak mean flow relative to the amplitude of wave-induced motion, which correspond to high, moderate and low Reynolds numbers based on the Taylor microscale (Re). The two-dimensional PIV velocity distributions enable spatial filtering to calculate some of the subgrid-scale (SGS) stresses, from which we can estimate the SGS dissipation, and evaluate the performance of typically used SGS stress models. The previously reported mismatch between the SGS and viscous dissipation at moderate and low Reynolds numbers appears to be related to the sparsity of large vortical structures that dominate energy fluxes.Conditional sampling of SGS stresses and dissipation based on wave phase using Hilbert transforms demonstrate persistent and repeatable direct effects of large-scale but weak straining by the waves on the SGS energy flux at small scales. The SGS energy flux is phase-dependent, peaking when the streamwise-wave-induced velocity is accelerating, and lower when this velocity is decelerating. Combined with strain rate generated by the mean flow, the streamwise wave strain causes negative energy flux (backscatter), whereas the vertical wave strain causes a positive flux. The phase-dependent variations and differences between horizontal and vertical contributions to the cascading process extend to strains that are substantially higher than the wave-induced motion. These trends may explain the measured difference between spatial energy spectra of streamwise velocity fluctuations and spectra of the wall-normal component, i.e. the formation of spectral bumps in the spectra of the streamwise component at the wavenumbers for the transition between inertial and dissipation scales.All the model coefficients of typical SGS stress models measured here are phase dependent and show similar trends. Thus, the variations of measured SGS dissipation with phase are larger than those predicted by the model variables. In addition, the measured coefficients of the static Smagorinsky SGS stress model decrease with decreasing turbulence levels, and increase with filter size. The dynamic model provides higher correlation coefficients than the Smagorinsky model, but the substantial fluctuations in their values indicate that ensemble averaging is required. The ‘global’ dynamic model coefficients indicate that the use of a scale-dependent dynamic model may be appropriate. The structure function model yields poor correlation coefficients and is found to be over-dissipative under all but the highest turbulence levels. The nonlinear model has higher correlations with measured stresses, as expected, but it also does not reproduce the trends with wave phase.

Model Test Study on Vortex-Induced Motions of a Floating Cylinder

2009 ◽  
Author(s):  
Ying Wang ◽  
Jianmin Yang ◽  
Tao Peng ◽  
Xin Li
Keyword(s):  
Circular Cylinder ◽  
Scale Model ◽  
Visualization System ◽  
Forced Motion ◽  
Drag Forces ◽  
Fluid Field ◽  
Helical Strakes ◽  
Induced Motion ◽  
Motion Characteristics ◽  
Lift And Drag

Vortex-Induced Motions (VIM) under current flow is an important issue for surface piercing cylinders, such as Spar platforms and floating buoys, since it affects the motion performance of these structures greatly. In recent years this phenomenon attracts much attention and many researchers have been making efforts to deal with this problem. VIM is such a complicated phenomenon that more fundamental studies are needed to understand the essence behind VIM. This paper mainly concentrates on a circular cylinder, aiming to eliminate outside influences and reveal the inherent characteristic of vortex-induced motion mechanism. A circular cylinder with an aspect ratio of 1:2.4, which could be considered as a scale model for the hard tank of a typical Truss Spar, is studied by experimental method to investigate the surrounding fluid field, the excitation forces and Vortex-Induced Motion characteristics under various governing parameters, such as the current velocity and direction, the mooring stiffness and distribution, the use and efficiency of helical strakes, and so on. By using a simple flow visualization system, the unsteady flow passing the circular cylinder and the vortices in the wake are captured and recorded. The cylinder is tested respectively under fixed, forced-motion and elastically moored conditions. The fluid field, the vortex structures, and the lift and drag forces under fixed and forced-motion conditions are measured, the VIM performance of the cylinder with two different mooring distributions are studied, and strake efficiency is studied considering current directionality and strake height influence.

Numerical Analysis of Wave-induced Motion of Floating Pendulor Wave Energy Converter

2011 ◽  
Vol 25 (4) ◽  
pp. 28-35 ◽  
Author(s):  
Bo-Woo Nam ◽  
Sa-Young Hong ◽  
Ki-Bum Kim ◽  
Ji-Yong Park ◽  
Seung-Ho Shin
Keyword(s):  
Numerical Analysis ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Induced Motion ◽  
Wave Induced

Wave induced motion of a triangular tension leg platforms in deep waters

2013 ◽  
Vol 3 (2) ◽  
pp. 149-165 ◽  
Author(s):  
A.M. Abou-Rayan ◽  
Amr R. El-Gamal
Keyword(s):  
Deep Waters ◽  
Induced Motion ◽  
Wave Induced

Motion control of a cruise ship by using active stabilizing fins

2011 ◽  
Vol 225 (4) ◽  
pp. 311-324 ◽  
Author(s):  
J-H Kim ◽  
Y-H Kim
Keyword(s):  
Motion Control ◽  
Control Algorithm ◽  
Roll Motion ◽  
Cruise Ship ◽  
Linear Quadratic ◽  
Linear Quadratic Gaussian ◽  
Lqg Control ◽  
Induced Motion ◽  
The Time Domain ◽  
Wave Induced

The present study considers the motion control of a cruise ship by using active stabilizing fins. One or two pairs of stabilizing fins are equipped to reduce the roll and/or pitch motions of the cruise ship. Each fin is controlled by algorithms based on proportional–integral–derivative (PID) and linear quadratic Gaussian (LQG) control. Numerical analysis of the wave-induced motion of a cruise ship with stabilizing fins is carried out by using the time-domain ship motion program which has been developed through this study. The resultant motion response as the performance of each controller is compared between different control algorithms. Based on the present simulation results, the stabilizing fin can be considered a good instrument to reduce pitch motion as well as roll motion of the present cruise ship model. The present results show that the PID control algorithm, a simple but practical algorithm, can be an appropriate method to reduce the roll motion in a moderate sea state, while the LQG control algorithm shows good performance in reducing not only the roll motion but also the coupled roll and pitch motions simultaneously in all of environmental conditions considered.

Computing Acceleration Loads on Free-Fall Lifeboat Occupants: Consequences of Including Nonlinearities in Water Waves and Mother Vessel Motions

2010 ◽  
Author(s):  
Neil Luxcey ◽  
Se´bastien Fouques ◽  
Thomas Sauder
Keyword(s):  
Water Waves ◽  
Three Dimensional ◽  
Free Fall ◽  
Momentum Conservation ◽  
Irregular Waves ◽  
Stokes Waves ◽  
Induced Motion ◽  
Wave Models ◽  
Wave Induced ◽  
The Impact

The safety of occupants in free-fall lifeboats (FFL) launched from a skid is addressed, and the focus is on numerical evaluation of acceleration loads during water impact. This paper investigates the required level of detail when modeling the physics of a lifeboat launch in waves. The first part emphasizes the importance of the non-linearity of the wave surface. Severity of impacts in linear (Airy) waves is compared to impacts in regular Stokes waves of the 5th order. Correspondingly, severity of impacts in irregular waves of the 2nd order is statistically compared to impacts in linear irregular waves. Theory of the two wave models are also briefly presented. The second part discusses the importance of a more detailed modeling of the launching system. This concerns especially cases for which damage to the mother vessel induces major lifeboat heel angles. A three-dimensional skid model is presented, along with validation against experimental measurements. In addition, the wave induced motion of the mother vessel is included. Consequences on the severity of the impact of the lifeboat in regular waves are discussed. This study is based on MARINTEK’s impact simulator for free-fall lifeboats, in which slamming loads are evaluated based on momentum conservation, a long wave approximation, and a von Karman type of approach. It is coupled here to the SIMO software, also developed at MARINTEK. Performance of this coupling is discussed.

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