ALTERNATIVE ASSESSMENT OF WEATHER CRITERION FOR SHIPS WITH LARGE BREADTH AND DRAUGHT RATIOS BY A MODEL EXPERIMENT: A CASE STUDY ON AN INDONESIAN RO-RO FERRY

2021 ◽  
Vol 162 (A1) ◽  
Author(s):  
D Paroka ◽  
S Asri ◽  
Rosmani ◽  
Hamzah
Keyword(s):  
Alternative Assessment ◽  
Roll Angle ◽  
Slope Coefficient ◽  
Decay Test ◽  
Wave Slope ◽  
Effective Wave ◽  
Bilge Keel ◽  
Dead Ship Condition ◽  
Weather Criterion

The weather criterion is one of stability criteria to verify ability of a ships to withstand the combined effects of severe wind and rolling criteria in dead ship condition. An overestimated roll angle is obtained when the weather criterion is applied to ships with breadth and draught ratios larger than 3.50 and ratios between vertical centre of gravity and draught larger than 1.50. This paper discusses the assessment of weather criterion for an Indonesian ro-ro ferry by model experiments. The drift test is performed in four wave steepnesses with wave frequencies near the roll natural frequency. The maximum roll amplitude is used to calculate the effective wave slope coefficient correponding to the wave steepness, with Bertin’s coefficient obtained by the roll decay test. The damping factors correspond to the breadth and draught ratio as well as the bilge keel contribution are determined using the formula of weather criterion with the roll angle obtained by the Japanese formula with a correction factor of 0.70 due to the irregularity of waves. The obtained effective wave slope coefficient and the damping factors due to breadth and draught ratio and the bilge keel are smaller than those used in the weather criterion.

Alternative Assessment of Weather Criterion for Ships with Large Breadth and Draught Ratios By a Model Experiment: A Case Study on an Indonesian Ro-Ro Ferry

2020 ◽  
Vol 162 (A1) ◽  
Author(s):  
D Paroka ◽  
S Asri ◽  
Rosmani ◽  
Hamzah
Keyword(s):  
Alternative Assessment ◽  
Roll Angle ◽  
Slope Coefficient ◽  
Decay Test ◽  
Wave Slope ◽  
Effective Wave ◽  
Bilge Keel ◽  
Dead Ship Condition ◽  
Weather Criterion

The weather criterion is one of stability criteria to verify ability of a ships to withstand the combined effects of severe wind and rolling criteria in dead ship condition. An overestimated roll angle is obtained when the weather criterion is applied to ships with breadth and draught ratios larger than 3.50 and ratios between vertical centre of gravity and draught larger than 1.50. This paper discusses the assessment of weather criterion for an Indonesian ro-ro ferry by model experiments. The drift test is performed in four wave steepnesses with wave frequencies near the roll natural frequency. The maximum roll amplitude is used to calculate the effective wave slope coefficient corresponding to the wave steepness, with Bertin’s coefficient obtained by the roll decay test. The damping factors correspond to the breadth and draught ratio as well as the bilge keel contribution are determined using the formula of weather criterion with the roll angle obtained by the Japanese formula with a correction factor of 0.70 due to the irregularity of waves. The obtained effective wave slope coefficient and the damping factors due to breadth and draught ratio and the bilge keel are smaller than those used in the weather criterion.

scholarly journals Estimation of Effective Wave Slope Coefficient of Ships with Large Breadth and Draught Ratio

Kapal ◽  
2020 ◽  
Vol 17 (1) ◽  
pp. 40-49
Author(s):  
Daeng Paroka ◽  
Andi Haris Muhammad ◽  
Sabaruddin Rahman
Keyword(s):  
Model Experiment ◽  
Center Of Gravity ◽  
Slope Coefficient ◽  
Beam Seas ◽  
Alternative Method ◽  
Strip Theory ◽  
Wave Slope ◽  
Effective Wave ◽  
Weather Criterion ◽  
Theory And Model

One of parameters to estimate heel angle of a ship in beam seas is effective wave slope coefficient. In the weather criterion of IMO, the effective wave slope coefficient is determined as function of ratio between distance of center of gravity from the sea surface and the ship draught. The others methods could be used to estimate the effective wave slope coefficient are simplified strip theory and model experiment. A ship with shallow draught and large vertical center of gravity can have an effective wave slope coefficient larger than 1.0 if the coefficient is calculated by using the formulae of weather criterion. Therefore, an alternative method to estimate the coefficient is necessary when it is applied to ships with geometry characteristics different with those used to develop the formulae. This research conducts to estimate the effective wave slope coefficient using three different methods, namely the formulae of weather criterion, the simplified strip theory and model experiment. Results of the three methods may provide enough evidence about suitable method to estimate the effective wave slope coefficient of ships with breadth and draught ratio larger than 3.5 like the Indonesian ro-ro ferries. Results and discussion show that the effective wave slope coefficient obtained by using the formulae of weather criterion is larger compared to that obtained by using the simplified strip theory and the model experiment. Here, the result of simplified strip theory for wave frequency the same as the roll natural frequency of subject ship is similar with the result of model experiment. This results show that the simplified strip theory can be used as an alternative method to determine the effective wave slope of a ship with breadth and draught ratio larger than 3.5 if the result of model experiment does not available.

Effective wave slope coefficient of river-sea ships

2019 ◽  
Vol 192 ◽  
pp. 106427
Author(s):  
Stefan Rudaković ◽  
Gabriele Bulian ◽  
Igor Bačkalov
Keyword(s):  
Slope Coefficient ◽  
Wave Slope ◽  
Effective Wave

Developing an Applied Profile for Assessing the Perceived Effectiveness of Athletes’ Psychological Strategies: A Case Study at the Australian Institute of Sport

2021 ◽  
Vol 5 (1) ◽  
pp. 1-9
Author(s):  
Umut Doğan
Keyword(s):  
Instrument Development ◽  
Alternative Assessment ◽  
Assessment Tool ◽  
Psychological Resilience ◽  
Perceived Effectiveness ◽  
Australian Institute ◽  
Applied Assessment ◽  
Present Case Study

Existing tools measuring athletes’ psychological strategies have various practical limitations including (a) not capturing the perceived effectiveness of psychological strategies in pursuing desirable outcomes; (b) overlooking stages of competitive involvement, such as before training or the night before competition; (c) and being predominantly paper-based. In the present case study, the author explains the process of developing an alternative assessment tool called the Profile of Psychological Strategies (ProPS). This new profile aims to measure athletes’ perceptions of which strategies they use, to pursue which desirable outcomes, and how effectively. The ProPS has its theoretical roots in Fletcher and Sarkar’s approach to developing psychological resilience and was developed based on an adapted version of Radhakrishna’s Sequence for Instrument Development. This case study can be useful both for sport experts looking for a practical and flexible way to measure athletes’ psychological strategies and for those aiming to develop their own applied assessment tool.

Navajo Speech and Language Evaluation

2020 ◽  
pp. 19-34
Author(s):  
Christine B. Vining ◽  
Davis E. Henderson
Keyword(s):  
American Indian ◽  
Cultural Differences ◽  
Alternative Assessment ◽  
Coordinated Care ◽  
Speech Language Pathologists ◽  
Indian Children ◽  
Language Evaluations ◽  
Typical Experience ◽  
Assessment Procedures

The case study highlights the importance of culturally and linguistically appropriate assessment of young Navajo/American Indian children and the importance of alternative assessment procedures to support appropriate diagnoses and recommendations. The case also illustrates systemic issues that result in lack of coordinated care, appropriate diagnosis, and lack of American Indian speech-language pathologists who understand linguistic and cultural differences. The case is based on a typical experience when clinicians who are not familiar with the Navajo language perform speech-language evaluations in Navajo-speaking communities.

scholarly journals Joint Analysis of Cost and Energy Savings for Preliminary Design Alternative Assessment

2020 ◽  
Vol 12 (18) ◽  
pp. 7507
Author(s):  
Carlo Iapige De Gaetani ◽  
Andrea Macchi ◽  
Pasquale Perri
Keyword(s):  
Energy Demand ◽  
Alternative Assessment ◽  
Energy Savings ◽  
Life Cycles ◽  
Decision Makers ◽  
Joint Analysis ◽  
Energy Demands ◽  
Design Alternatives ◽  
The Impact

The building sector plays a central role in addressing the problem of global energy consumption. Therefore, effective design measures need to be taken to ensure efficient usage and management of new structures. The challenging task for designers is to reduce energy demands while maintaining a high-quality indoor environment and low costs of construction and operations. This study proposes a methodological framework that enables decision-makers to resolve conflicts between energy demand and life cycle costs. A case study is analyzed to validate the proposed method, adopting different solutions for walls, roofs, floors, windows, window-to-wall ratios and geographical locations. Models are created on the basis of all the possible combinations between these elements, enriched by their thermal properties and construction/management costs. After the alternative models are defined, energy analyses are carried out for an estimation of consumption. By calculating the total cost of each model as the sum of construction, energy and maintenance costs, a joint analysis is carried out for variable life cycles. The obtained results from the proposed method confirm the importance of a preliminary assessment from both energy and cost points of view, and demonstrate the impact of considering different building life cycles on the choice of design alternatives.

Sign in / Sign up

Export Citation Format

Share Document