Full-scale Results Research Articles

Study on the influence of shaft brackets on the scale effect of the four-screw ship wake field

In the four-screw ship navigation, the load difference between the inner and outer propeller is found to be more than twice of that in the model test, indicating a serious scale effect. The stern attachment of the four-screw ship has a significant impact on the inner and outer propeller wake which directly affecting the load distribution. Thus, to investigate the impact of the brackets on the scale effect of the four-screw ship flow field, this paper conducted multi-scale simulations of a four-screw ship with and without bracket using the Reynolds-averaged Navier-Stokes (RANS) method. The feasibility and accuracy of the numerical method was verified by comparing with PIV test results. The result shows that the scale effect is more pronounced in the outer propeller compared to the inner propeller. The presence of bracket reduces the wake fraction difference between the inner and outer propellers, but significantly affects the inner radius region of the outer propeller disk, more than doubling the wake fraction in this region at full-scale. When the bracket Reynolds number falls below its critical Reynolds number, the inner radius region of the outer propeller flow field deviates notably from the full-scale results and loses its practical significance.

Modelling and Numerical Simulation of a Compartment Fire: Flow Rate Behaviour at Opening

The modelling of fire behaviour in a compartment is the subject of this work. A small-scale experimental study was carried out in a compartment sized 0.5 m × 0.5 m × 0.5 m with a single door with a width of 0.2 m and a height of 0.4 m. The collected results were converted to full-scale results using Froude modelling. The objective of this study was to see how ventilation affects fuel decomposition rate, gas flow rate at the opening and the power generated inside the compartment. This small-scale experimental study allowed us to determine four values of the fuel’s (diesel) mass loss rate, which correspond to four values of the ventilation factor. Numerical simulation using Fire Dynamics Simulator (FDS) software was used to show the gas’ behaviour at the opening and the variation of the power generated inside the compartment. The vertical profiles of the experimental and numerical temperatures were compared. It was found that the dimensions of the opening have a significant influence on the power generated inside the compartment.

Full-scale URANS prediction of a vessel's transverse stability in wind and waves under lifting condition

Predicting a vessel’s motion response is important for the design as well as evaluating its operability and sustainability. This is often performed in towing tanks through captive model tests in towing tanks. However, discrepancies exist between model-scale and full-scale results. Besides, quite often, the wind is not included in the test, resulting in unrealistic assumptions of static pressure and constant heeling lever from the wind. This paper presents a study on transverse stability under wind, waves, and lifting conditions, incorporating several series of URANS-based simulations in model-scale and full-scale. According to the results, scaling effects accounts for about 3~15% in terms of roll amplitudes and it seems to be both frictional-force-related and wave-frequency-dependent. Wind force exerts limited influence on the vessel’s transverse stability, however, in waves especially for longer wavelength, a wind of 25 m/s increases the roll amplitude up to 53% and it appears to be wave frequency-dependant. The correlation between roll motion and wind/waves/lifting is complicated but their combination produces way more influence than any individual factor alone, indicating none of them should be neglected.

War-Making and Mediation in Civil Wars: Three Ideal Types of Third Parties and Ripeness Concepts

ABSTRACT Despite the accumulation of a sizable scholarship on mediation of civil war by third-party states, little effort has been made to formulate a conceptual framework geared toward explaining how the prior or ongoing modes of their engagements in war-making affect their possible conduct of mediation. The present article is an attempt to fill this lacuna by presenting a threefold typology of third-party states: war-making patrons, war-supporting friends, and war-observing bystanders. The article explores how these three kinds are distinct from one another as a mediator, in terms of such crucial aspects as motives and timing, readiness, bias and commitment, and leverage. This inquiry is pursued through extending to the level of third parties Zartman’s seminal notions of a ‘mutually hurting stalemate’, a ‘way out’, and a ‘mutually enticing opportunity’ that have hitherto been discussed mainly at the level of primary parties. The article is intended as the presentation of an analytical framework and initial propositions rather than full-scale research results.

Experimental Investigation of the Adsorption and Desorption Kinetics on an Open-Structured Asymmetric Plate Heat Exchanger; Matching Between Small-Scale and Full-Scale Results

This paper introduces the results of an experimental study on the adsorption and desorption kinetics of a commercially available, open-structured asymmetric plate heat exchanger adapted to act as an adsorber/desorber for the application in adsorption heat transformation processes. In addition, a volumetric large temperature jump (V-LTJ) kinetic setup was applied to measure the adsorption and desorption kinetics of a small-scale adsorbent sample prepared dedicatedly to be representative for the adsorbent domain inside the investigated adsorber plate heat exchanger (APHE). All kinetic results of the small-scale adsorbent sample and the APHE were fitted into exponential forms with a single characteristic time constant (τ) with a coefficient of determination (R2) better than 0.9531. A very good matching between the small-scale and full-scale adsorption kinetic measurements was obtained, with an average relative deviation of 12.3% in the obtained τ-values. In addition, the kinetic data of the small-scale adsorbent sample were utilized for estimating the expected specific instantaneous and moving average powers of the evaporator/condenser heat exchanger. The average relative deviation (ARD) between the moving average specific evaporator powers obtained from the small-scale and the full-scale measurements amounts between 5.4 and 15.1%.

Use of spray nozzles to recover dissolved methane from an Upflow Anaerobic Sludge Blanket (UASB) reactor effluent.

Methane is a powerful greenhouse gas and a source of energy. Recovering this gas means lower greenhouse gas emission and potential reduction of energetic costs. The lack of full-scale results, the use of different methodologies to detect dissolved methane (d-CH4) and the fact that no process to remove d-CH4 from anaerobic effluents is energetically or economically viable at full-scale urged a different approach to the problem. To avoid methodological interference and facilitate comparison of results the Standard Test Method number D8028-17 published by ASTM International can be used to determine d-CH4. The use of real anaerobic reactor effluent also helps results to be compared. In this study, 80 samples from a full-scale anaerobic reactor showed an average concentration of dissolved methane of 14.9 mg·L-1, meaning an emission of 229 kg of CO2 eq·h-1 and an average of 113.5 kW wasted. Using spray nozzles, an alternative to the methods being researched, the average methane recovery was 11.5 mg·L-1 of CH4, an efficiency of 81.6%, meaning 177 kg of CO2 eq·h-1 emissions avoided and 87.9 kW of recoverable energy.

Prediction of drag and lift forces of a high-speed vessel at full scale by CFD-based GEOSIM method

In this study, it was aimed to obtain an accurate extrapolation method to compute lift and drag forces of high-speed vessels at full-scale by using CFD (Computational Fluid Dynamics) based GEOSIM (GEOmetrically SIMilar) method which is valid for both fully planing and semi-planing regimes. Athena R/V 5365 bare hull form with a skeg which is a semi-displacement type of high-speed vessel was selected with a model family for hydrodynamic analyses under captive and free to sinkage/trim conditions. Total drag and lift forces have been computed for a generated GEOSIM family of this form at three different model scales and full-scale for Fr = 0.8 by an unsteady RANS (Reynolds Averaged Navier–Stokes) solver. k–ε turbulence model was used to simulate the turbulent flow around the hulls, and both DFBI (Dynamic Fluid Body Interaction) and overset mesh technique were carried out to model the heave and pitch motions under free to sinkage/trim condition. The computational results of the model family were used to get “drag-lift ratio curve” for Athena hull at a fixed Fr number and so the corresponding results at full scale were predicted by extrapolating those of model scales in the form of a non-dimensional ratios of drag-lift forces. Then the extrapolated full-scale results calculated by modified GEOSIM method were compared with those of full-scale CFD and obtained by Froude extrapolation technique. The modified GEOSIM method has been found to be successful to compute the main forces (lift and drag) acting on high-speed vessels as a single coefficient at full scale. The method also works accurately both under fully and semi-planing conditions.

A REVIEW OF METHODS FOR HYDRO-ACOUSTIC ANALYSIS OF NON-CAVITATING MARINE PROPELLERS

Underwater Radiated Noise (URN) emanating from surface and underwater marine platforms has become a significant concern for all the Nations in view of the global requirement to minimise the increasing adverse impact on marine mammals and fishes and maintain ecological balance in the ‘Silent’ ocean environment. Ambient noise level in the sea, in 10 to 300 Hz frequency band, has increased by 20 to 30 dB due to shipping (Wittekind, 2009). Marine propeller (in non- cavitating and cavitating regime) is a potential contributor to the ships noise and a lot of scientific research has been undertaken and considerable progress has been achieved in estimating the hydro-acoustic performance of marine propellers. In light of this, the scope of this paper is to review and critically examine the various methods used for estimating the hydro-acoustic performance of marine propellers, particularly in the non-cavitating regime, over the past many years. This review paper brings out the details, applicability, merits and demerits of various methods, extrapolation laws to obtain full scale results, scientific conclusion of all the know-how on this subject and the scope of further research as perceived by the authors. This paper also presents a numerical methodology to estimate the noise radiated by a DTMB 4119 model propeller in the non-cavitating regime in open water condition. The hydrodynamic analysis of the propeller was performed using commercial CFD software STARCCM+, closure was achieved using standard k-ε turbulence model and hydro-acoustic predictions have been performed using FWH acoustic analogy. The results compare very well with the published literature.

Development of realistic scale model auditors

Scale model auditors in previous researches have frequently been adopted to simplify the shape and roughly approximate the sound absorption of a real human auditor with limited amount of clothing in a seated state. As the importance of acoustic design has been emphasized not only in concert halls and theatres, but also in rock and pop venues where stood auditors dominate floors, it is necessary to look into the sound absorption of auditors in a wider range beyond the existing framework. In the present work, a new approach through a sequential process from the body skins to the amount of clothing is employed to develop a realistic scale model auditor. In comparison with full-scale results, five types of independent auditors being separated from chairs and capable of standing or sitting are successfully constructed with various amount of wearable clothing. Furthermore, the effects of clothing on the absorption characteristics of auditors are presented in the sparse standing and densely seated conditions. A series of experiments to examine the validity of the developed scale model auditors for both sparse standing and densely seated states confirmed that the sound absorption characteristics of model auditors are well accordance with full-scale results.

HORSES FOR COURSES: HOW TO SELECT THE “RIGHT” WIND PROPULSION SYSTEM AND HOW TO MAKE THE BUSINESS CASE

Wind propulsion systems (WPS) are major investments and the decision to install them requires careful consideration of many complex questions. In this paper we present a systematic, scientific methodology to assess the benefits and drawbacks of such systems at the early concept stage of a vessel. The purpose is to provide guidance for shipowners and operators and help them make informed decisions. The proposed method was developed into a Software tool called ‘SEAMAN Winds’ and has been correlated to full scale results. The program draws on our large database of model tests, and CFD of hulls and wind propulsion technologies. It uses the intended trading routes of the vessel as an important input, typical output data are: a) performance values (ship speed, power requirements etc.) b) environmental parameters (CO2 avoided, EEDI and EEXI reduction, carbon intensity indicator) c) financial metrics (bunker savings, payback time for installation of WPS) Potential applications of the method include making the business case for one particular WPS or investigating in how far certain systems are more suited for a specific route than others.

Cost effective meter of moisture integral parameters of the atmospheric column

Continuous remote monitoring of the atmospheric physical parameters is an urgent task for solving the issues related to meteorology, climatology, artificial influence on clouds, studying the physical parameters of cloud cover etc. In the developed countries such issues are solved using science-driven technologies of millimeter wave range radiometry. They allow, in particular, quick restoration of the values of total content and effective temperature of droplet and vaporous moisture in the atmospheric column, and distinguishing the areas with crystalline, droplet or vaporous water phases.
 This work aims at substantiating, by calculation and experiment, the possibility of large-scale solving the problems of continuous remote monitoring of the studied atmospheric moisture parameters using the method of centimetre wavelength range radiometry. To determine the best pair of frequencies for restoring the atmospheric moisture parameters based on radiometric data of remote sensing the linear absorption coefficients were calculated for clear atmosphere, for cloudy atmosphere depending on the temperature of drops and for rainfalls of various intensities for 4, 12, 20, 40 and 94 GHz frequencies. In order to calculate these data, we used a well-known MPM model (Atmospheric Millimeter-Wave Propagation Model). At the same time, calculation of the altitude profiles of the atmospheric meteorological parameters was carried out based on the ERA-15 model.
 Comparison of the data obtained by calculation, taking into account the progress of the technical parameters of the serial element base, indicated a possibility of solving the above problems in the centimetre wavelength as well. The research presents a description of the diagram and technical solutions, as well as the appearance of a two-frequency radiometric system with 1.5 cm and 2.5 cm ranges created at the National Aerospace University (KhAI) on the basis of an easily accessible modern element base and full-scale tests' results. The budget-friendly focus of the described product allows for radiophysical measurement with a sensitivity of radiometers exceeding 0.01 K while ensuring the cost of small-scale production of the radio technical part of the system, comparable to the cost of TV converters commonly used in everyday life.

Validation of a Chinese version of the five facet mindfulness questionnaire and development of a short form based on item response theory

This research aimed to validate a Chinese version of the Five Facet Mindfulness Questionnaire (FFMQ-C) and develop a short form based on classic test theory and Item Response Theory (IRT). 539 participants were recruited for the study, with 499 of them yielding valid data. The age range of the participants was from 18 to 71 years. Results demonstrated high test-retest reliability and high internal consistency of FFMQ-C. Based on the full-scale results, a 15-item short-form scale (FFMQ-C-SF) was developed using both classic test theory and IRT. The short form also had good internal consistency. Confirmatory factor analysis (CFA) supported the five-factor structure of the FFMQ-C and FFMQ-C-SF with adequate model fit. Validity was indicated by significant correlations between the two mindfulness scales and theoretically related constructs (e.g., emotional intelligence and experiential avoidance). Our findings indicate that FFMQ-C and FFMQ-C-SF can be used to measure mindfulness among the Chinese population.

Cyclic Behavior and Modeling of Bolted Glulam Joint with Cracks Loaded Parallel to Grain

Under varying humidity and temperature conditions, with the constraint of metal fasteners to wood shrinkage, cracks along the bolt lines are generally observed in bolted glulam joints. A three-dimensional (3D) numerical model was established in software package ANSYS to investigate the cyclic behavior of bolted glulam joints with local cracks. A reversed cyclic loading was applied in the parallel-to-grain direction. The accuracy of numerical simulation was proved by comparison with full-scale experimental results. Typical failure modes were reproduced in the numerical analysis with the application of wood foundation zone material model and cohesive zone material model. The effect of crack number and length on the hysteretic behavior of bolted glulam joints was quantified by a parametric study. It was found that initial cracks impair the peak capacity and elastic stiffness of bolted glulam joints significantly. More decrease in capacity was observed in joints with more cracks, and longer cracks affect elastic stiffness more dramatically. Moreover, with the existence of initial cracks, the energy dissipated and equivalent viscous damping ratio of bolted joints are reduced by 24% and 13.3%, respectively.

Estimation of the industrial building reinforced concrete beams’ residual life under corrosive media influence

The dominant factor determining chemical industry objects’ durability is the corrosive wear of the stretched reinforcement and the compressed zone of concrete. The article presents a methodology and results of a numerical assessment of the residual life of the reinforced concrete frame beams of an industrial building operating in an aggressive environment. According to the full-scale engineering survey results, the most damaged frame structures - the beams of the intermediate floors were identified. The period of concrete protective layer complete neutralization, the degree of corrosion damage to the working reinforcement, the compressed concrete neutralized layer depth, the change in its strength characteristics with depth and the degree of its heterogeneity were determined by the field measurements using the standard and non-standard methods of non-destructive testing. A linear law of the accumulation of corrosion damage to concrete in the compressed zone and the rate of corrosion damage in the working reinforcement after the concrete protective properties’ exhaustion is adopted. A normative design apparatus is used for the first group of limiting states in relation to the most loaded section. For an adequate assessment and prediction of the residual resource, the main emphasis is on experimental and diagnostic methods.

Numerical and small-scale physical modelling of wave transmission by wooden fences

Mangrove forests, that often act as natural coastal defences, enormously suffered due to ongoing climate change and human disturbances. Thus, it is necessary to have a countermeasure to mitigate the loss of mangroves. Wooden fences are becoming a viable nature-based solution to protect vulnerable replanted mangrove forests. However, the wooden fence's hydraulic characteristics are not yet fully understood due to the complication of branches arrangement. In the present study, a small-scale wave flume modelling of wave damping by a wooden fence was constructed using the inner branches as an inhomogeneous arrangement tested in earlier flow-resistance experiments. The physical model results indicate that the wooden fence is highly effective on wave transmission and that the effectiveness in wave reduction depends on the relative fence thickness, B/Hi. To understand the scale effect on wave transmission further, the numerical model SWASH was used with the laboratory wave data. By applying the prior experiments' drag coefficient on steady flow, the uncalibrated numerical model gave a good agreement with the wave model results, with a root-mean-square error for the total transmitted wave heights of 4.7%. After validation, potential scale effects for small scale tests were determined from scaling simulations at both full scales and the applied 1:5 model scale. These simulations were performed for a fence porosity of 0.81, and different fence thicknesses to understand scale effects between model- and full-scale. Both wave reflection and transmission at model-scale are about 5% higher than full-scale results due to the increased drag coefficient and viscous effects. The effects of fence thickness and porosity were the same in large and small scale, and much larger than the error due to scale effects. Hence testing fence efficiency at physical small scale is regarded as a useful tool, together with numerical modelling.

Vertical zigzag maneuver of a generic submarine

A study of a 10/10 vertical zigzag maneuver of the generic submarine Joubert BB2 is presented. CFD simulations, involving moving planes and rotating propeller using a dynamic overset technique, are performed at constant propeller rotational speed in model scale on four systematically refined grids and compared against experimental data for depth, pitch, pitch rate, vertical drift, vertical velocity, absolute velocity, and propeller thrust and torque coefficients. A grid study is also performed for the self-propelled approach condition before starting the maneuver, used to obtain the propeller rotational speed, controller vertical and horizontal commands, and boat attitude. The maneuver is also analyzed in full scale at 6, 10 and 15 knots. Results indicate that CFD matches very well the experimental data, even for the coarsest grid, with the propeller RPS converging slowest in grid. By comparing model and full scale results, it can be concluded that model scale simulations are a good surrogate for full scale for parameters related to motions, but as expected forces are strongly affected by scale and the propeller operational point changes considerably. Analysis of forces and moments affecting vertical control from hull, sail and stern planes, propeller and hull help understand the response of the vehicle.

Prediction of Resistance and Self-Propulsion Characteristics of a Full-Scale Naval Ship by CFD-Based GEOSIM Method

Resistance and self-propulsion characteristics of a naval ship at full scale have been investigated by using Telfer’s GEOmetrically SIMilar (GEOSIM) method based on the computational fluid dynamics (CFD) approach. For this purpose, first, the resistance forces of the Office of Naval Research Tumblehome (ONRT) hull have been computed at different three model scales by using the overset mesh technique. The full-scale resistance and nominal wake fraction of the ONRT hull have been estimated by using Telfer’s GEOSIM method. Resistance and nominal wake fraction have then been compared with those of CFD at full scale. Later, the self-propulsion characteristics of the ONRT hull have been examined using Telfer’s GEOSIM method based on the CFD approach. Self-propulsion factors at the full-scale hull have been predicted by using the SST k–x turbulence model to involve 2-degrees of freedom ship motions (heave and pitch). Rotational motion of the propeller has also been simulated by using the rigid body motion technique. The results calculated by Telfer’s GEOSIM method and the 1978 International Towing Tank Conference (ITTC) extrapolation technique have been compared with each other and discussed with those of the CFD approach at full scale. It was found that the full-scale results (both resistance and self-propulsion factors) predicted by Telfer’s GEOSIM method are closer to those of the CFD approach than those of the 1978 ITTC technique. It can be noted that Telfer’s GEOSIM method is fast, robust, and reliable and can be used as an alternative to the 1978 ITTC method for predicting the self-propulsion performance of a full-scale ship. Introduction Resistance and self-propulsion characteristics of a surface ship should be known properly in the design stages. For this purpose, model tests and numerical methods are used together to determine the resistance and self-propulsion performance of a ship. However, model tests are expensive and time-consuming, and the accuracy of the International Towing Tank Conference (ITTC) extrapolation technique from model scale to full scale may not have in a satisfactory level. On the other hand, Telfer’s GEOmetrically SIMilar (GEOSIM) method based on computational fluid dynamics (CFD) can overcome these difficulties.

Monitoring of Plankton Spatial and Temporal Characteristics With the Use of a Submersible Digital Holographic Camera

The study shows that the use of a submersible digital holographic camera as part of a multifunctional hardware and software complex allows carrying out in situ measurements of plankton, automating the process of obtaining data on plankton, as well as classifying plankton species up to an order within the specified taxonomic groups. Such automation ensures monitoring expeditionary or stationary research of species diversity and spatial and temporal organization of zooplankton in conjunction with hydrophysical parameters of the medium. This paper presents the full-scale results of vertical profiles and daily measurements of plankton made with the use of the submersible digital holographic camera, as well as the classification of plankton in laboratory and field conditions in the automatic mode. It is shown that within the accomplished version the classification algorithm using the morphological parameter makes it possible to solve the problem quickly (time required to obtain the result is less than 1 second and depends on the number of plankton particles and the frame size of a restored image), however the classification accuracy by orders varies within 50-60%.

Nitrite-shunt and biological phosphorus removal at low dissolved oxygen in a full-scale high-rate system at warm temperatures.

This study presents results from the City of St. Petersburg's (Florida) Southwest Water Reclamation Facility. This high-rate BNR plant (SRT~5days; HRT<8hr) achieves combined bioP and shortcut simultaneous nitrification and denitrification (SND) via nitrite in a simple BNR configuration-an anaerobic-aerobic (A/O) process without mixed liquor recycle and a 25% unaerated fraction. N removal to low effluent and nitrate and nitrite ( + ) concentrations occurs mainly via SND by operating the aerated zone at low DO, but still achieving near-complete ammonium ( ) removal. Despite the low DO operation, very good bioP performance is achieved. Full-scale performance data and detailed bench-scale testing were conducted to assess the nitrogen and phosphorus removal at low DO conditions. Full-scale results showed that the plant achieves effluent total inorganic nitrogen (TIN) and total phosphorus (TP) concentrations of approximately 2.0mgN/L and 0.5mgP/L, respectively, at an average influent C:N ratio of 7:1 mgCOD:mgN. PRACTITIONER POINTS: Simple anaerobic-aerobic (A/O) process demonstrated combined N and P removal Ammonia oxidation was not hampered by low DO (<0.5mg/L) operation Low DO (<0.5mg/L) operation sustained SND via nitrite pathway in a high-rate process (HRT<6hr) P uptake was demonstrated at low DO which counters to the widely held understanding that high DO (>1.5mg/L) is necessary Heterotrophic consumption of nitrite at low DO was the key to the out-selection of nitrite-oxidizing bacteria.

Numerical Study on the Hydrodynamic Performance of Antifouling Paints

This study presents a simple numerical method that can be used to evaluate the hydrodynamic performances of antifouling paints. Steady Reynolds-averaged Navier-Stokes equations were solved through a finite volume technique, whereas roughness was modeled with experimentally determined roughness functions. First, the methodology was validated with previous experimental studies with a flat plate. Second, flow around the Kriso Container Ship was examined. Lastly, full-scale results were predicted using Granville’s similarity law. Results indicated that roughness has a similar effect on the viscous pressure resistance and frictional resistance around a Reynolds number of 107. Moreover, the increase in frictional resistance due to roughness was calculated to be approximately 3%–5% at the ship scale depending on the paint.