Large Naval Vessels Research Articles

On the hydrodynamic loading of marine cycloidal propeller during maneuvering

In marine cycloidal propeller (MCP), the inflow velocity vector to the propeller blade continuously changes at different blade orbit angle. Earlier marine cycloidal propellers were installed on ships that mainly performed towing operations. Recently marine cycloidal propellers are being installed on large naval vessels, which spend lot of their operating hours in cruising. Therefore, the hydrodynamic loading on the blades both during cruising maneuvers need to be investigated. The flow characteristics around the propeller blade are computed numerically by panel method. Viscous effects on the flow are then estimated by boundary layer technique. The effect of rotating disc on viscous fluid is also investigated. The corrected flow characteristics are then used for estimating the hydrodynamic loading. The operating conditions that are critical for the loading of the blade and the support structure and some aspects of the maneuvering simulation at cruising speed are investigated.

Coagulation function of stored whole blood is preserved for 14 days in austere conditions: A ROTEM feasibility study during a Norwegian antipiracy mission and comparison to equal ratio reconstituted blood.

Formulation of a medical preparedness plan for treating severely bleeding casualties during naval deployment is a significant challenge because of territory covered during most missions. The aim of this study was to evaluate the concept of "walking blood bank" as a supportable plan for supplying safe blood and blood products. In 2013, the Royal Norwegian Navy conducted antipiracy operations from a frigate, beginning in the Gulf of Aden and ending in the Indian Ocean. Crews were on 24-hour emergency alert in preparation for an enemy assault on the frigate. Under an approved command protocol, a "walking blood bank," using crew blood donations, was established for use on board and on missions conducted in rigid-hulled inflatable boats, during which freeze-dried plasma and leukoreduced, group O low anti-A/anti-B titer, cold-stored whole blood were stored in Golden Hour Boxes. Data demonstrating the ability to collect, store, and provide whole blood were collected to establish feasibility of implementing a whole blood-focused remote damage-control resuscitation program aboard a naval vessel. In addition, ROTEM data were collected to demonstrate feasibility of performing this analysis on a large naval vessel and to also measure hemostatic efficacy of cold-stored leukoreduced whole blood (CWB) stored during a period of 14 days. ROTEM data on CWB was compared with reconstituted whole blood. Drills simulating massive transfusion activation were conducted, in which 2 U of warm fresh whole blood with platelet sparing leukoreduction were produced in 40 minutes, followed by collection of two additional units at 15-minute increments. The ROTEM machine performed well during ship-rolling, as shown by the overlapping calculated and measured mechanical piston movements measured by the ROTEM device. Error messages were recorded in 4 (1.5%) of 267 tests. CWB yielded reproducible ROTEM results demonstrating preserved fibrinogen function and platelet function for at least 3.5 weeks and 2 weeks, respectively. The frequency of ROTEM tests were as follows: EXTEM (n = 88), INTEM (n = 85), FIBTEM (n = 82), and APTEM (n = 12). CWB results were grouped. Compared with Days 0 to 2, EXTEM maximum clot firmness was significantly reduced, beginning on Days 10 to 14; however, results through that date remained within reference ranges and were comparable with the EXTEM maximum clot firmness for the reconstituted whole blood samples containing Day 5 room temperature-stored platelets. A "walking blood bank" can provide a balanced transfusion product to support damage-control resuscitation/remote damage-control resuscitation aboard a frigate in the absence of conventional blood bank products. ROTEM analysis is feasible to monitor damage-control resuscitation and blood product quality. ROTEM analysis was possible in challenging operational conditions. Therapeutic study, level V.

Treating the Signature Injury

Treating the Signature Injury

주포 사격시험을 이용한 대형 함정의 모달테스트

The accurate results of finite element analysis are directly related to reliability FE model which is exactly describing dynamic characteristics of target structure. So, a model updating is necessary to establish reliable FE(Finite Element) model with a lot of experience and effort using modal testing. A large structure is too difficult to obtain the dynamic characteristics owing to its weight and size. In this work, using main gun firing test, modal testing was performed to obtain dynamic characteristics of large naval vessel, which is difficult to tap the general modal testing method. The result of experiment was considered its possibility and future plans.

Application and verification of internal boundary conditions for antenna mast wake predictions

It has been shown through wind tunnel tests that “small” geometric features such as antennas and masts can influence the mean and turbulent wake signature behind large naval vessels. Modeling these geometric features using standard computational fluid dynamics techniques requires wrapping either structured or unstructured computational grids around these very complicated structures. This is a very costly approach for many reasons. As an alternative, internal boundary conditions have been developed with the intention of capturing at least the first-order effects of the presence of the masts and antennas. A test case using a generic naval vessel mast was developed. A wind tunnel model of the antenna mast geometry was created and hot-wire anemometry data were collected. The CFD predictions were shown to compare well with the wind tunnel data for the parameters of concern.

Generalized ISAR - part I: an optimal method for imaging large naval vessels

We describe a generalized inverse synthetic aperture radar (ISAR) process that performs well under a wide variety of conditions common to the naval ISAR tests of large vessels. In particular, the generalized ISAR process performs well in the presence of moderate intensity ship roll. The process maps localized scatterers onto peaks on the ISAR plot. However, in a generalized ISAR plot, each of the two coordinates of a peak is a fixed linear combination of the three ship coordinates of the scatterer causing the peak. Combining this process with interferometry will then provide high-accuracy three-dimensional location of the important scatterers on a ship. We show that ISAR can be performed in the presence of simultaneous roll and aspect change, provided the two Doppler rates are not too close in magnitude. We derive the equations needed for generalized ISAR, both roll driven and aspect driven, and test them against simulations performed in a variety of conditions, including large roll amplitudes.

Generalized ISAR-part II: interferometric techniques for three-dimensional location of scatterers

This paper is the second part of a study dedicated to optimizing diagnostic inverse synthetic aperture radar (ISAR) studies of large naval vessels. The method developed here provides accurate determination of the position of important radio-frequency scatterers by combining accurate knowledge of ship position and orientation with specialized signal processing. The method allows for the simultaneous presence of substantial Doppler returns from both change of roll angle and change of aspect angle by introducing generalized ISAR ates. The first paper provides two modes of interpreting ISAR plots, one valid when roll Doppler is dominant, the other valid when the aspect angle Doppler is dominant. Here, we provide, for each type of ISAR plot technique, a corresponding interferometric ISAR (InSAR) technique. The former, aspect-angle dominated InSAR, is a generalization of standard InSAR; the latter, roll-angle dominated InSAR, seems to be new to this work. Both methods are shown to be efficient at identifying localized scatterers under simulation conditions.

Demographics, attitudes, and reef management preferences of sport divers in offshore Texas waters

The Texas Parks and Wildlife Department has created artificial reefs to enhance sport-diving opportunities since 1989. Administrators see the need to site reefs dependent on area-specific human population and tourism densities and the demand for sport-diving resources. This requires an understanding of the sport-diver constituency and their particular interests and needs. In 1997, we surveyed sport divers using a mail questionnaire. Because of difficulties involved in establishing a sampling frame of saltwater divers, the study focused on divers who used dive charter boats to go diving offshore in the previous 12 months (n=1057). A response rate of 56% was achieved. On average, respondents went diving for 20 days in the previous 12 months. Most reported scuba diving is their most important outdoor recreation activity. The majority preferred to dive at depths ranging between 60 and 89 feet and preferred large naval vessels and rig jackets and other oil production structures as their materials-of-choice for future reef deployment. Results are useful for evaluating artificial reefs available in offshore Texas waters as well as input for future reef development. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.

Error as Opportunity: Learning in a Cooperative Task

In this article, we examine learning within a cooperative system. We focus on the role of learning from errors in a context where regular attrition of group members occurs. Specifically, the study involved observation of distributed activity in the team navigation of a large naval vessel. Analyses revealed frequent individual errors; however, successful detection and correction of errors also occurred. Thus, the cooperative system simultaneously allowed high component error and ensured low system output error. This robustness is an especially valuable feature for distributed systems because it provides for needed on-the-job learning while maintaining a high level of overall performance. Errors were observed to function as opportunities for instruction based on a novice's demonstrated need to know. The distributed system was found to contain certain design tradeoffs that are exploited for their utility in learning (viz., distributing knowledge across the team and providing multiple perspectives for error detection). The results are applicable to the design of computer-supported cooperative tasks and provide guidelines for task organization that facilitates performance while incorporating the ability to learn from errors.

Cohort study of venereal disease. I: the risk of gonorrhea transmission from infected women to men.

Reliable data on the risk of transmission of N. gonorrhoeae would enhance our understanding of the importance of host defenses against gonorrhea and would aid in the evaluation of prophylactic measures. This paper examines the risk of transmission of gonorrhea from infected female to male and the role that variables such as race, prophylaxis and amount of exposure play in the development of gonococcal urethritis. Volunteer crew members of a large naval vessel were followed prospectively as a cohort to study their risk of acquiring gonococcal infection during a four-day liberty period in the Far East. At the same time the prevalence of N. gonorrhoeae was determined in a population of females to whom the sailors were exposed. The calculated risk of transmission per exposure with an infected partner was .19 for whites and .53 for blacks. A statistically significant relationship was noted between the risk of transmission of gonorrhea and both the number of partners and the frequency of sexual intercourse. Further, the increasing infection rate with increasing numbers of exposures in men who had a single sex partner suggests that the majority of men are in fact susceptible to gonorrhea if the quantity of exposure is sufficient.