... m, width 18 m, water depth 5.6 m, equipped with a double flap wave generator ... If wave brea... more ... m, width 18 m, water depth 5.6 m, equipped with a double flap wave generator ... If wave break-ing is encountered during calculation the simulation gets unstable and stops. ... these limitations a numerical wave tank using a commercial computational fluid dynamics (CFD) solver is ...
This paper presents a new model testing technique for offshore structures and ships in wave tanks... more This paper presents a new model testing technique for offshore structures and ships in wave tanks. For model excitation wave packets with broad energy spectra and a short extension at the location of model/wave interaction are used. This allows a perfect analysis of the wave-structure interaction within a few seconds, and the measurement can be completed in many cases before side wall reflections may disturb the results. The application is illustrated at the hydrodynamic analysis of a stationary semisubmersible and a high speed catamaran. The wave packet tests yield magnitude and phase shift of the transfer functions with high resolution and in a very good correspondence to regular wave tests and calculations. To extend experimental investigations to hydrodynamically compact structures where tank wall effects cannot be neglected this paper proposes the installation of vertical side wall wave absorbers. As their damping characteristics depend on the flow direction, high wave damping is provided perpendicular to the absorber to minimize side wall reflections. However, waves propagating parallel to side walls and absorber will not be disturbed.
A growing amount of reports on heavy lift operations involving huge crane vessels prove that inve... more A growing amount of reports on heavy lift operations involving huge crane vessels prove that investigations on the motion behavior of multi-body systems are vital regarding the combined aspects of safety and economics. In this paper a method of transforming frequency-domain into time-domain results is presented. With the panel program WAMIT (WAMIT Inc.) the Response Amplitude Operators (RAO) of the motions in six degrees of freedom of the structures involved in a lift operation are calculated. The multi-bodies RAOs differ significantly from those of the single structures (without interaction effects). The consideration of hydrodynamic coupling is therefore essential for the prediction of accurate relative motions between the structures. Frequency-domain results are still important when determining operational limitations. But only with simulations in time-domain the relation between cause and reaction can be studied in detail. Results from simulations provide for example decision support for finding uncritical starting points of the lift off operation. By Fouriertransforming the RAOs the impulse-response functions are obtained. Having the impulse-response function the time-dependent system responses in arbitrary deterministic wave registrations are determined by convolution. This method allows fast and effective time-domain simulations of multi-body systems. Results are presented for a crane semisubmersible and a conventional transport barge. The influence, particularly the sensitivity of wave height and wave length on the response is shown in wave packets.
This paper investigates the vertical motions and bending moments of a FPSO platform in regular wa... more This paper investigates the vertical motions and bending moments of a FPSO platform in regular waves and also in several design storms with a duration of three hours which correspond to the 100 years return period of the North Sea. An experimental program was carried out with a scaled model in a seakeeping tank. The experimental data is systematically compared
This paper gives a comparative overview of the operation capabilities of different crane vessel t... more This paper gives a comparative overview of the operation capabilities of different crane vessel types. It demonstrates that the dynamic behaviour of moored floating cranes can be treated as being linear over a wide range of applications. Under certain conditions, however, the coupled system of floating structure and swinging load shows distinctly nonlinear phenomena and parametric oscillations can occur. In such cases a safe heavy lift operation cannot be guaranteed since the linear methods underestimate the occurring loads and motions. Nonlinear mooring line forces are a major cause of nonlinear crane vessel and load motions. Seakeeping tests have been carried out using a MAGNUS crane barge model at a scale of 1 : 25 in regular head seas. Time series show a coexistence of 2- and 3-periodic motions with significantly increased amplitudes compared to the 1-periodic linear mode. Surge and pitch motion of the floating body as well as the coupled motion of the swinging load are substant...
When installing an offshore pipeline, a long unsupported pipe span is lowered from the laying ves... more When installing an offshore pipeline, a long unsupported pipe span is lowered from the laying vessel to the seabed. Pipe bending stresses are reduced by pulling the pipeline with a tensioner on board of the moored laying vessel. In the seaway, the moving vessel causes pipe oscillations. Two tensioning methods are investigated: a blocked tensioner which avoids any relative motion between pipe and laying vessel, and a compensating tensioner ruling out dynamic pipe tension. Differential equations for pipe oscillations are deduced and solved, including, besides other nonlinear effects, the interaction between bending oscillations and dynamic tension. Linearised soil damping and elasticity at the lower end of the suspended span is taken into account. The computed results are validated by experiments based on a new model testing technique which assures similarity by considering all relevant non-dimensional parameters.
MODUS (Mobile Docker for Underwater Sciences) has been developed, manufactured and tested during ... more MODUS (Mobile Docker for Underwater Sciences) has been developed, manufactured and tested during the EU project GEOSTAR 2 (GEophysical and Oceanographic STation for Abyssal Research) in the framework of Marine Science and Technology Programme (MAST-III), [GEOSTAR,2001]. Aim of the MODUS development, as one part of the project, is to establish a new deep water intervention technology supporting versatile research activities in water depth down to 4000 m. The MODUS system consequently focuses on a modular design with the ability to adapt to a large variety of scientific applications like remotely controlled deployment/recovery of large and heavy Bottom Stations or exact operation of deep-sea sampling rosettes. The paper highlights the development phase of MODUS with the iterative optimisation process of 3d CAD design and hydrodynamic/hydroelastic investigations, illustrated by three concurrent design variants. The paper presents first results from deep-sea operations in the Tyrrhenian...
... m, width 18 m, water depth 5.6 m, equipped with a double flap wave generator ... If wave brea... more ... m, width 18 m, water depth 5.6 m, equipped with a double flap wave generator ... If wave break-ing is encountered during calculation the simulation gets unstable and stops. ... these limitations a numerical wave tank using a commercial computational fluid dynamics (CFD) solver is ...
This paper presents a new model testing technique for offshore structures and ships in wave tanks... more This paper presents a new model testing technique for offshore structures and ships in wave tanks. For model excitation wave packets with broad energy spectra and a short extension at the location of model/wave interaction are used. This allows a perfect analysis of the wave-structure interaction within a few seconds, and the measurement can be completed in many cases before side wall reflections may disturb the results. The application is illustrated at the hydrodynamic analysis of a stationary semisubmersible and a high speed catamaran. The wave packet tests yield magnitude and phase shift of the transfer functions with high resolution and in a very good correspondence to regular wave tests and calculations. To extend experimental investigations to hydrodynamically compact structures where tank wall effects cannot be neglected this paper proposes the installation of vertical side wall wave absorbers. As their damping characteristics depend on the flow direction, high wave damping is provided perpendicular to the absorber to minimize side wall reflections. However, waves propagating parallel to side walls and absorber will not be disturbed.
A growing amount of reports on heavy lift operations involving huge crane vessels prove that inve... more A growing amount of reports on heavy lift operations involving huge crane vessels prove that investigations on the motion behavior of multi-body systems are vital regarding the combined aspects of safety and economics. In this paper a method of transforming frequency-domain into time-domain results is presented. With the panel program WAMIT (WAMIT Inc.) the Response Amplitude Operators (RAO) of the motions in six degrees of freedom of the structures involved in a lift operation are calculated. The multi-bodies RAOs differ significantly from those of the single structures (without interaction effects). The consideration of hydrodynamic coupling is therefore essential for the prediction of accurate relative motions between the structures. Frequency-domain results are still important when determining operational limitations. But only with simulations in time-domain the relation between cause and reaction can be studied in detail. Results from simulations provide for example decision support for finding uncritical starting points of the lift off operation. By Fouriertransforming the RAOs the impulse-response functions are obtained. Having the impulse-response function the time-dependent system responses in arbitrary deterministic wave registrations are determined by convolution. This method allows fast and effective time-domain simulations of multi-body systems. Results are presented for a crane semisubmersible and a conventional transport barge. The influence, particularly the sensitivity of wave height and wave length on the response is shown in wave packets.
This paper investigates the vertical motions and bending moments of a FPSO platform in regular wa... more This paper investigates the vertical motions and bending moments of a FPSO platform in regular waves and also in several design storms with a duration of three hours which correspond to the 100 years return period of the North Sea. An experimental program was carried out with a scaled model in a seakeeping tank. The experimental data is systematically compared
This paper gives a comparative overview of the operation capabilities of different crane vessel t... more This paper gives a comparative overview of the operation capabilities of different crane vessel types. It demonstrates that the dynamic behaviour of moored floating cranes can be treated as being linear over a wide range of applications. Under certain conditions, however, the coupled system of floating structure and swinging load shows distinctly nonlinear phenomena and parametric oscillations can occur. In such cases a safe heavy lift operation cannot be guaranteed since the linear methods underestimate the occurring loads and motions. Nonlinear mooring line forces are a major cause of nonlinear crane vessel and load motions. Seakeeping tests have been carried out using a MAGNUS crane barge model at a scale of 1 : 25 in regular head seas. Time series show a coexistence of 2- and 3-periodic motions with significantly increased amplitudes compared to the 1-periodic linear mode. Surge and pitch motion of the floating body as well as the coupled motion of the swinging load are substant...
When installing an offshore pipeline, a long unsupported pipe span is lowered from the laying ves... more When installing an offshore pipeline, a long unsupported pipe span is lowered from the laying vessel to the seabed. Pipe bending stresses are reduced by pulling the pipeline with a tensioner on board of the moored laying vessel. In the seaway, the moving vessel causes pipe oscillations. Two tensioning methods are investigated: a blocked tensioner which avoids any relative motion between pipe and laying vessel, and a compensating tensioner ruling out dynamic pipe tension. Differential equations for pipe oscillations are deduced and solved, including, besides other nonlinear effects, the interaction between bending oscillations and dynamic tension. Linearised soil damping and elasticity at the lower end of the suspended span is taken into account. The computed results are validated by experiments based on a new model testing technique which assures similarity by considering all relevant non-dimensional parameters.
MODUS (Mobile Docker for Underwater Sciences) has been developed, manufactured and tested during ... more MODUS (Mobile Docker for Underwater Sciences) has been developed, manufactured and tested during the EU project GEOSTAR 2 (GEophysical and Oceanographic STation for Abyssal Research) in the framework of Marine Science and Technology Programme (MAST-III), [GEOSTAR,2001]. Aim of the MODUS development, as one part of the project, is to establish a new deep water intervention technology supporting versatile research activities in water depth down to 4000 m. The MODUS system consequently focuses on a modular design with the ability to adapt to a large variety of scientific applications like remotely controlled deployment/recovery of large and heavy Bottom Stations or exact operation of deep-sea sampling rosettes. The paper highlights the development phase of MODUS with the iterative optimisation process of 3d CAD design and hydrodynamic/hydroelastic investigations, illustrated by three concurrent design variants. The paper presents first results from deep-sea operations in the Tyrrhenian...
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Papers by Gunther Clauss