PICASSO VISION instrument design, engineering model test results, and flight model development status

This paper describes hydrodynamic model tests of Wing in Surface Effect (WiSE) Craft. These craft was fitted with stephull form in different location on longitudinal flat bottom (stepedhull planning craft) to determine the influences of sticking and porpoising motion performances. These motions are usually occured when the craft start to take-off from water surfaces. The test models with scale of 1 : 7 were comprised of 4 (four) stephull models and 1 (one) non-stephull model as a comparative study. The hydrodynamic tests were performed with craft speed of 16 – 32 knots (prototype values) in Towing Tank at UPT. Balai Pengkajian dan Penelitian Hidrodinamika (BPPH), BPPT, Surabaya. The resistance (drag) was measured by dynamo meter and the trim of model (draft changing at fore and aft of model due to model speed) was measured by trim meter. By knowing the value of model trim, the wetted surface area can be determined. Then, the lift forces were calculated based on these measured values. The model test results were presented on tables and curves. Test results show that models with step located far away from center of gravity of the WiSE craft tend to porpoising and sticking condition, except if the step location on the below of these center of gravity. While model without step tends to sticking conditions.

Download Full-text

Inclined Loading Capacity of Embedded Suction Anchors in Clay

Volume 7: Offshore Geotechnics; Petroleum Technology ◽

10.1115/omae2009-79035 ◽

2009 ◽

Author(s):

Y. S. Kim ◽

K. O. Kim ◽

Y. Cho ◽

S. Bang ◽

K. D. Jones

Keyword(s):

Analytical Solution ◽

Model Test ◽

Inclination Angle ◽

Load Application ◽

Centrifuge Model Test ◽

Loading Capacity ◽

Test Results ◽

Pullout Capacity ◽

Centrifuge Model ◽

Inclined Loading

An analytical solution has been developed to estimate the inclined pullout capacity of an embedded suction anchor in clay seafloor. Validation has been made through comparisons with a limited number of centrifuge model test results. Results indicate that the inclined pullout capacity of an embedded suction anchor in clay decreases as the load inclination angle to the horizontal increases. As the point of the load application moves downward, the inclined pullout capacity increases, reaches its peak, and then starts to decrease.

Download Full-text

Development and Verification of Modeling Practice for CFD Decay Calculations to Obtain Roll Damping of FPSO

10.1115/omae2021-62411 ◽

2021 ◽

Author(s):

Arjen Koop ◽

Pierre Crepier ◽

Sebastien Loubeyre ◽

Corentin Dobral ◽

Kai Yu ◽

...

Keyword(s):

Model Test ◽

Test Results ◽

Cfd Modelling ◽

Roll Damping ◽

Natural Period ◽

Computational Mesh ◽

Safety Studies ◽

Offshore Industry ◽

Decay Tests ◽

Set Up

Abstract Estimates for roll damping are important input parameters for simulation studies on vessels operating at sea, e.g. FPSO mooring in waves, wind and current, workability and operability investigations, Dynamic Position studies, ship-to-ship operations and safety studies of vessels. To accurately predict the motions of vessels this quantity should be determined with confidence in the values. Traditionally, model experiments in water basins using so-called decay tests are carried out to determine the roll damping. With recent advancements in CFD modelling, the offshore industry has started using CFD as an alternative tool to compute the roll damping of FPSO’s. In order to help adopt CFD as a widely accepted tool, there is a need to develop confidence in CFD predictions. Therefore, a practical CFD modelling practice is developed within the Reproducible CFD JIP for roll decay CFD simulations. The Modelling Practice describes the geometry modelling, computational mesh, model set-up and post-processing for these type of CFD calculations. This modelling practice is verified and validated by three independent verifiers against available model test data. This paper provides an overview of the developed modelling practice and the calculated CFD results from the verifiers. The CFD modelling practice is benchmarked against available model test results for a tanker-shaped FPSO. By following this modelling practice, the CFD predictions for the equivalent linear damping coefficient and natural period of the roll motions are within 10% for all verifiers and within 10% from the model test results. Therefore, we conclude that when following the developed modelling practice for roll decay simulations, reliable, accurate and reproducible results can be obtained for the roll damping of tanker-shaped FPSOs.

Download Full-text

FROUDE’S LAW OF SIMILITUDE – CONTEMPORARY AND FUTURE SEAKEEPING TESTING

The International Journal of Maritime Engineering ◽

10.5750/ijme.v153ia2.849 ◽

2021 ◽

Vol 153 (A2) ◽

Author(s):

R P Dallinga ◽

R H M Huijsmans

Keyword(s):

Model Test ◽

Scale Effects ◽

Higher Order ◽

Air Pressure ◽

Test Results ◽

Viscous Effects ◽

Two Phase ◽

Scale Models ◽

Non Linear

Historically “scale effects” in the interpretation of tests with scale models in waves using Froude’s Law of Similitude are mostly associated with viscous effects. Nowadays, with a much more complete modelling of reality and a focus on higher order non-linear phenomena, scaling of model test results implies a wider range of assumptions than the validity of Froude’s Law. Our contribution to the conference is a visionary review of contemporary and future problems in the interpretation of these tests. In this context we will discuss the developments in test techniques, including the development of a new Two-Phase Laboratory facilitating seakeeping and sloshing tests at reduced air pressure.

Download Full-text

Outlier analysis of sloshing impact loads on liquid ship cargo

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/14750902211069548 ◽

2022 ◽

pp. 147509022110695

Author(s):

Sang-Yeob Kim ◽

Yonghwan Kim ◽

Yang-Jun Ahn

Keyword(s):

Model Test ◽

Present Method ◽

Treatment Method ◽

Liquefied Natural Gas ◽

Impact Loads ◽

Test Results ◽

Outlier Analysis ◽

Load Prediction ◽

Conventional Procedure

This paper introduces an outlier analysis which can improve the convergence of the statistical analysis results of sloshing model test data. The paper classify possible outliers in the sloshing model test into three categories and present a treatment method for each outlier. The developed outlier analysis is adapted to the model test results for the cargo of the liquefied-natural-gas (LNG) carrier in operation. The results of the present new method are compared with those of the conventional procedure, particularly focusing on long-term sloshing prediction. Through this study, the effectiveness of the present method is observed, and it is found that the present method provides is robust and reliable results in the application of experimental data for load prediction.

Download Full-text

A new atmospheric boundary layer wind tunnel simulation methodology for wind effects on large cooling towers considering wind environment variations

Advances in Structural Engineering ◽

10.1177/1369433218809899 ◽

2018 ◽

Vol 22 (5) ◽

pp. 1194-1210 ◽

Cited By ~ 2

Author(s):

XX Cheng ◽

X Chen ◽

YJ Ge ◽

H Jiang ◽

L Zhao

Keyword(s):

Boundary Layer ◽

Wind Tunnel ◽

Atmospheric Boundary Layer ◽

Model Test ◽

Test Results ◽

Wind Effects ◽

Simulation Methodology ◽

Codes Of Practice ◽

Wind Tunnel Simulation ◽

Tunnel Model

The traditional atmospheric boundary layer wind tunnel model test practice employs wind fields, the flow characteristics of which are in accordance with the empirical formulae of the atmospheric turbulence presented in Codes of Practice and monographs. However, the empirical formulae presented in Codes of Practice and monographs cannot truthfully reflect the high variations of the realistic atmospheric turbulence which sometimes aggravates wind effects on structures. Based on model tests conducted in a multiple-fan actively controlled wind tunnel, it is found that most wind effects on large cooling towers change monotonically with the increase in free-stream turbulence, and the model test results are more unfavorable for a flow field of low turbulence intensity than for a flow field of high turbulence intensity with respect to the measured coherences. Thus, a new atmospheric boundary layer wind tunnel simulation methodology for wind effects on circular cylindrical structures is proposed to overcome the deficiency of the traditional atmospheric boundary layer wind tunnel model tests. The new simulation methodology includes the simulation of two realistic atmospheric boundary layer flow fields with the highest and the lowest turbulence intensities in the wind tunnel and the envelopment of model test results obtained in the two flow fields (e.g. the mean and fluctuating wind pressure distributions, the power spectral density, the coherence function, and the correlation coefficient). The superiority of the new atmospheric boundary layer wind tunnel simulation methodology over the traditional model test practice is demonstrated by comparing the model test results with the full-scale measurement data.

Download Full-text

Estimation of Performance Variation of Coal Fired Boilers Cofired With Biomass: Development of a Predicting Tool

Volume 2: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation; Environmental and Regulatory Affairs ◽

10.1115/gt2006-91142 ◽

2006 ◽

Author(s):

Sudipta De ◽

Mehrzad Kaiadi ◽

Mohsen Assadi

Keyword(s):

Customer Service ◽

Pilot Plant ◽

Model Development ◽

Test Results ◽

Performance Variation ◽

Future Improvement ◽

Pilot Plant Test ◽

Plant Test ◽

Biomass Cofiring ◽

Available Information

Biomass cofiring in existing coal fired boilers has emerged as one of the most prospective technologies in order to address voluntary reduction of green house gases and other emissions, potential portfolio standards, customer service etc. within the context of deregulations. Pilot plant test results have confirmed the potential of biomass cofiring with coal for commercial use. However, being a new and developing technology, there is hardly any tool available for estimation of variation in performance of an existing coal fired boiler due to its retrofitting for biomass cofiring. A predicting tool is developed to estimate this performance variation using available information of pilot plant test results in literature or from data of plant operating with biomass. In order to incorporate future available information, this is developed in a flexible environment of Model Development Kit (MDK) of IPSEpro, a commercially available heat and mass balance program. Development of the models for this predicting tool as well as its limitations and possible future improvement has been discussed in this paper. Some results regarding estimation of change in efficiency, emissions and associated costs using this developed predicting tool has been presented.

Download Full-text