Bow shape modification through multi-objective hydrodynamic optimization: Methodology comparison between CAD-based FreeForm Deformation and Mesh-based Radial Basis Function approach

Marine industrial engineering face crucial challenges because of environmental footprint of vehicles, global recession, construction, and operation cost. Meanwhile, Shape optimization is the key feature to improve ship efficiency and ascertain better design. Accordingly, the present paper proposes an automated optimization framework for ship hullform modification to reduce total resistance at two cruise and sprint speeds. The case study is a bow shape of a wave-piercing bow trimaran hull. To this end, a multi-objective hydrodynamic problem needs to be solved. A combined optimization strategy using CFD hullform optimization is presented using the software tools STAR-CCM+ and SHERPA algorithm as optimizer. Furthermore, a comparison is made between CAD-based and Mesh-based parametrization techniques. Comparison between geometry regeneration methods is performed to present a practical and efficient parametrization tool. Design variables are control points of FreeForm Deformation (FFD) for CAD-based method and Radial Basis Function (RBF) for Mesh-based method. The optimization results show a 4.77% and 2.47% reduction in the total resistance at cruise and sprint speed, respectively.

Block-Based Development of a Mobile Application in Basic Electrical Concept for Diploma in Electrical Engineering Student

Electrical Technology is one of the main courses for Diploma in Electrical Engineering students in Politeknik Malaysia. The subject has been delivered conventionally; however, due to the Covid-19 pandemic, relatively it has changed the landscape in delivery method. Regarding this problem, an innovation by using an online learning application such as mobile applications is a must. There are many mobile applications provided in the Google Playstore; however, the function is either limited to one function for each mobile application or too complicated for diploma students. This paper presents the block-based programming language used in App Inventor to make the creation of mobile apps for basic electrical concepts for electrical engineering students in Politeknik namely My ReSist. This app is used to convert the resistance color codes to resistance values and calculate the total resistance in the circuit as well as to do Star-Delta transformations. Results showed that this mobile application is useful for students to solve basic electrical concept including total resistance in series and parallel circuit. It is proved that this app is user-friendly and attractive.

A Power Demand Analytical Model of Self-Propelled Vessels

The article herein presents a closed-form mathematical equation by which it is possible to estimate the propulsion power demand of ships as a function of the propeller parameters and total Resistance. The validation of the derived model is conducted by use of the Series 60 Model data and of the Korea Research Institute of Ships and Ocean Engineering (KRISO) Very Large Crude-oil Carrier 2 (KVLCC2) data. In all the cases tested, the derived model explained more than 99.9% of the data variability. Furthermore, the paper describes a practical method for quantifying changes in hull and propeller performance and provides an application example.

ON THE MACRO HYDRODYNAMIC DESIGN OF HIGHLY EFFICIENT MEDIUM- SPEED CATAMARANS WITH MINIMUM RESISTANCE

A new class of fuel-efficient and environmentally friendly twin-hull vessels is currently under development. Compared to high-speed catamarans, a significant reduction in speed combined with an increase in deadweight tonnes will lead to a highly efficient medium-speed catamaran design. Recently-built conventional and high-speed ferries are compared to each other in terms of length, speed, deadweight and transport efficiency to classify the new design. The goal of this study is to find a preliminary macro design point for minimum total resistance by considering the main particulars of the catamaran vessel: block coefficient, prismatic coefficient and slenderness and separation ratios of the demihulls. Publications containing recommendations towards the optimum hull form parameters for moderate Froude numbers are reviewed and existing experimental data analysed to identify parameters for this new class of vessel. Designs with varied L/BOA-ratios and constant deck area are compared to find configurations of low total resistance for carrying a nominated deadweight at a particular speed, the associated change of the light ship weight has been taken into account. Two different model test series of catamaran models have been considered and their resistance curves agreed to each other. Recommendations are made; with the most important being the vessel should not exceed a speed of Fr = 0.35, with optimal prismatic coefficients around CP ≈ 0.5 and low transom immersion. This study presents the preliminary design of medium-speed single and twin-hull vessels for operations close to hump speed.

RESISTANCE PREDICTION USING ARTIFICIAL NEURAL NETWORKS FOR PRELIMINARY TRI-SWACH DESIGN

Due to the novel hull form design, at present no standard series or full-scale data is publicly available to predict Tri- SWACH resistance during the preliminary ship design process. This work investigates the viability of using an Artificial Neural Network (ANN) to quickly predict total resistance for preliminary Tri-SWACH design. An ANN was trained using total resistance experimental data obtained from model tests, which varied side hull arrangements. The results highlight strong correlation for model resistance prediction. A Tri-SWACH case study was then developed which had side hull geometric properties different to any previously used to train the ANN. The results, validated against CFD predictions, mimicked the resistance pattern generated by other model experimental data, providing confidence in the ANN’s ability to function as a resistance prediction tool. This work demonstrates the viability of ANN to assess Tri-SWACH resistance as part of a preliminary design process. These results suggest that ANNs can be effective tools for assessing performance given relevant training data.

A Numerical Study of Spray Strips Analysis on Fridsma Hull Form

Spray strips are deflectors added to the hull to reduce the Wetted Surface Area (WSA). The reduced WSA will decrease the total ship drag caused by the deflection of the spray strip installation. The research aimed to predict the function of the spray strip to improve ship performance using Computational Fluid Dynamics (CFD). The numerical approach in this study used the Finite Volume Method (FVM) with the RANS (Reynolds-averaged Navier–Stokes) equation to solve fluid dynamics problems. VOF (Volume of Fluid) was used to model the water and air phases. The results of this study indicated that the number of spray strips would have a significant effect compared to without using a spray strip. Spray strips with three strips could reduce the total resistance by 4.9% at Fr 1.78. Spray strips would increase the total resistance value by 2.1% at low speeds. Spray strips were effective for reducing total resistance at Fr > 1 or the planing mode conditions. The total resistance prediction used three suggestion profiles with the best performance to reduce total resistance by 6.0% at Fr 1.78.

A computational model of the cereal leaves hydraulics

Environmental factors and plant architectonics significantly determine its water regime, namely, the water content and its movement through the tissues forced by the difference in water potentials, turgor pressure in cells, etc. In turn, the cumulative water regime affects the functioning and growth of cells, photosynthesis, and, as a result, the plant’s growth. The leaf contributes to the formation of the water regime and characterizes the contour of the plant’s adaptive system. Nevertheless, the data on the contribution of leaves to the total resistance to water transport in the plant and the structure of the hydraulic resistance of the leaf itself is still contradictory. This paper presents the formulation and justification of the monocots leaf hydraulics model based on Darcy’s law. The model was tested in computational experiments in the Comsol 4.3b package on idealized geometric models of leaf blades. Simulations showed the dependence of water potential distribution in xylem vessels and leaf mesophyll on the permeability of these tissues and on microclimatic parameters around the leaf. The adequacy of the model parameters selected as a result of testing is discussed.

Synthesis and study of the electrical conductive properties of Cs2Fe2TiO16 in various gas atmospheres

In this work, titanate Cs2Fe2Ti6O16 with a hollandite-type structure was synthesized by solid-phase synthesis. The electrical conductivity of the obtained ceramics was investigated in the temperature range from 25 to 800 °C in air and in the presence of an argon-hydrogen mixture (3% H2). It was found that the electrical conductivity of the compound under consideration depends on the composition of the atmosphere — the activation energy of conduction changes (0.57 eV in air and 0.91 eV in the presence of hydrogen). The volumetric and grain-boundary contributions to the total resistance of the sample in the gases under consideration are separated by impedance spectroscopy at a temperature of 800 °C.

ISOLATION, CHARACTERIZATION AND ANTIBACTERIAL SREENING OF ANTIBIOTICS PRODUCED FROM STREPTOMYCES ISOLATED FROM DUMPSITE SOILS IN ILORIN, NORTH CENTRAL NIGERIA

Antibiotics are one of the most exploited metabolites produced by soil actinomycetes. This study isolated fifteen actinomycetes (A1 – A15) from dumpsite soils within Ilorin metropolis & screened them for antibacterial activity. Isolates were identified with morphology & biochemical characteristics.Their activity against clinical bacteria (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae & Staphylococcus aureus) was determined. Their bioactive metabolites after fermentation was assayed for by agar well diffusion & compared with reference antibiotics. Molecular analysis of two most active isolates was done. The most active metabolite was subjected to GCMS. All isolates were identified as Streptomyces, 7 isolates exhibited activity against 3 test bacteria with highest (10.5mm±0.35) by Streptomyces griseoplanus while S. aureus demonstrated total resistance to all isolates. Secondary activity revealed 7 of the metabolites as effective against the bacteria with highest activity (28.5±1.04mm) by S. sparsogenes showing similar activity with Cefuroxime (28.01±0.01mm). The two most active isolates were Streptomyces griseoplanus strain NR725RL-ISP 5009 & Streptomyces sparsogenes strain NBRC 1308616S & RNA nucleotide similarity revealed close phylogenic relationship. GC-MS revealed10 compounds in S. sparsogenes strain NBRC 1308616S metabolite. Streptomyces from dumpsite soils within Ilorin produced bioactive compounds against clinical test bacteria and thus could be potential sources of antibiotics.