scholarly journals Experimental and Computational Methodology for the Determination of Hydrodynamic Coefficients Based on Free Decay Test: Application to Conception and Control of Underwater Robots

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3631 ◽  
Author(s):  
Juan S. Cely ◽  
Roque Saltaren ◽  
Gerardo Portilla ◽  
Oz Yakrangi ◽  
Alejandro Rodriguez-Barroso
Keyword(s):  
Cfd Simulation ◽  
Low Cost ◽  
Water Channel ◽  
Hydrodynamic Coefficients ◽  
Underwater Robots ◽  
Free Decay ◽  
Test Application ◽  
Decay Test ◽  
Decay Tests ◽  
And Control

Hydrodynamic coefficients are essential for the development of underwater robots; in particular, for their design and navigation control. To obtain these coefficients, several techniques exist. These methods are usually experimental, but, more recently, some have been designed by a combination of experiments with computational methods based on Computational Fluid Dynamics (CFD). One method for obtaining the hydrodynamic coefficients of an ROV (Remote Operated Vehicle) is by using an experimental PMM (Planar Motion Mechanism) or CWC (Circular Water Channel); however, the use of these experimental infrastructures is costly. Therefore, it is of interest to obtain these coefficients in other ways, for example, by the use of simple experiments. The Free Decay Test is an ideal type of experiment, as it has a low cost and is simple to implement. In this paper, two different free decay tests were carried out, to which three different methods for obtaining coefficients were applied. They were compared with results obtained by CFD simulation to conduct a statistical analysis in order to determine their behaviours. It was possible to obtain values of the drag and added mass coefficients for the models analysed, where the values were obtained for an Underwater Drone Robot (UDrobot).

scholarly journals Heave Motion of a Vertical Cylinder with Heave Plates

2021 ◽  
Vol 28 (1) ◽  
pp. 42-47
Author(s):  
Ewelina Ciba
Keyword(s):  
Vertical Cylinder ◽  
Offshore Wind ◽  
Hydrodynamic Coefficients ◽  
Spar Platforms ◽  
Object Based ◽  
Free Decay ◽  
Decay Test ◽  
Classic Form ◽  
Heave Motion ◽  
Floating Platforms

Abstract The shape of a vertical cylinder resembles the classic form of a spar platform. Spar platforms are floating platforms that are successfully used in waters of great depths and have several advantages that mean they are readily used in the oil industry. Many of these advantages are also relevant to their application for offshore wind turbines, which is currently being considered. In the hydrodynamic analysis of spar platforms, the determination of their hydrodynamic coefficients plays an important role. They can be determined based on the free decay test. The study presents a method for determining the hydrodynamic coefficients of an object based on the free decay test. The results of free oscillation calculations with the help of numerical fluid mechanics tools are presented and compared with the results of the experiment and analytical solution. The application of determined coefficients and their significance for floating platforms are discussed. The influence of change in the form of an additional damping element on the behaviour of spar structures is shown.

scholarly journals Identification of underwater vehicle hydrodynamic coefficients using free decay tests

2004 ◽  
Vol 37 (10) ◽  
pp. 363-368 ◽  
Author(s):  
Andrew Ross ◽  
Thor I. Fossen ◽  
Tor Arne Johansen
Keyword(s):  
Underwater Vehicle ◽  
Hydrodynamic Coefficients ◽  
Free Decay ◽  
Decay Tests

Assessment of Nonlinear Heave Damping Model for Spar With Heave Plate Using Free Decay Tests

2016 ◽  
Author(s):  
Mahesh J. Rao ◽  
S. Nallayarasu ◽  
S. K. Bhattacharyya
Keyword(s):  
Cfd Simulation ◽  
Linear Quadratic ◽  
Cfd Simulations ◽  
Free Decay ◽  
Linear Damping ◽  
Heave Plate ◽  
Decay Tests ◽  
Heave Motion ◽  
Damping Model ◽  
Quadratic Damping

Linear damping models have been used in the past for solving floating body dynamics, especially for simple geometries such as spar. However, due to the addition of heave damping elements to spar such as heave plate, complex flow around these elements may change the relationship between damping and velocity of the body to nonlinear. The damping plays a major role in accurate determination of motion response of spars, especially the heave. Free decay tests have been carried out for spar with and without heave plate in calm water condition. The Computational Fluid Dynamics (CFD) simulation of heave decay is carried out using ANSYS FLUENT and validated by free decay test results using scale models. Mesh convergence study has been conducted to determine the optimum mesh size. The heave motion obtained from CFD are used to derive the damping terms by matching the heave motion obtained using equation of motion by changing the damping term with linear, quadratic and the combination of linear and quadratic. The heave motion obtained from linear damping model matches well with that obtained from measured motion and CFD simulation for spar without heave plate. However, the linear / quadratic damping models alone are not suitable for spar with heave plate. Hence a combination of linear and quadratic damping model is proposed for spar with heave plate. The heave motion computed using a combination of linear and quadratic damping model matches well with that obtained from experimental studies and CFD simulations thus indicating the complexity of flow around heave plate in comparison to the spar alone. Further, the vortices around the spar models obtained from CFD simulations are also presented and discussed with regard to the higher order damping.

Identificación de polaridad de los devanados en un motor trifásico de 6 terminales

2019 ◽  
pp. 13-19
Author(s):  
José Luis Viramontes-Reyna ◽  
Josafat Moreno-Silva ◽  
José Guadalupe Montelongo-Sierra ◽  
Erasmo Velazquez-Leyva
Keyword(s):  
Low Cost ◽  
Voltage Reference ◽  
Three Phase ◽  
Voltage Phase ◽  
The Law ◽  
And Control

This document presents the results obtained from the application of the law of Lens to correctly identify the polarity of the windings in a three-phase motor with 6 exposed terminals, when the corresponding labeling is not in any situation; Prior to identifying the polarity, it should be considered to have the pairs of the three windings located. For the polarity, it is proposed to feed with a voltage of 12 Vrms to one of the windings, which are identified randomly as W1 and W2, where W1 is connected to the voltage phase of 12 Vrms of the signal and W2 to the voltage reference to 0V; by means of voltage induction and considering the law of Lens, the remaining 4 terminals can be identified and labeled as V1, V2, U1 and U2. For this process a microcontroller and control elements with low cost are used.

Restoring and Controlling the Water Pollution of Endangered River in Bangladesh: A Case Study in Pabna City

2020 ◽  
Vol 3 (2) ◽  
pp. 68-81
Author(s):  
Abu Sadath ◽  
Farhana Afroz ◽  
Hosne Ara ◽  
Abdulla-Al Kafy
Keyword(s):  
Water Pollution ◽  
Local Community ◽  
River Flow ◽  
Low Cost ◽  
Design Approach ◽  
Government Officials ◽  
Conservation Plan ◽  
Policy Measures ◽  
And Control ◽  
Riverfront Development

Rivers are the lifeline of Bangladesh economy and serve as the source of water supply, fisheries, irrigation for agriculture, low-cost transport, generate electricity and conserve biodiversity. The Ichamati River situated in Pabna, Bangladesh is also a blessing for the city. However, recently, due to the irregular and unplanned activities adjacent to the riverside, the life, flow and water quality of the river is in a vulnerable condition. This study aims to identify the present status of the Ichamati River and provide an effective design approach and policy measures in restoring the river flow and control water pollution. The data was collected from the questioner surveys, key informant interviews and focus group discussions. Results suggest that several factors such as the construction of an illegal settlement, unplanned waste dumping, disposal of fiscal sludge through sewerage connection, lack of awareness among people regarding the importance of river biodiversity and absence of riverfront development and conservation plan are responsible for water pollution, inconsistent water flow and damaging the life cycle of Ichamati river. The design approach and policy measures were developed based on the perceptions of local community people, experts and government officials. The suggested policy measures will help to restore the flow of the river and reduce the water pollution, and the design approach will ensure the economic benefit of the riverfront development in future.

scholarly journals Information and information resources in COVID-19: Awareness, control, and prevention

2021 ◽  
pp. 096100062110165
Author(s):  
Mohammadhiwa Abdekhoda ◽  
Fatemeh Ranjbaran ◽  
Asghar Sattari
Keyword(s):  
Low Cost ◽  
Information Resources ◽  
Age And Gender ◽  
Use Of Resources ◽  
Strategic Approach ◽  
Wide Range ◽  
Data Collection Instrument ◽  
Control And Prevention ◽  
And Gender ◽  
And Control

This study was conducted with the aim of evaluating the role of information and information resources in the awareness, control, and prevention of COVID-19. This study was a descriptive-analytical survey in which 450 participants were selected for the study. The data collection instrument was a researcher-made questionnaire. Descriptive and inferential statistics were used to analyze the data through SPSS. The findings show that a wide range of mass media has become well known as information resources for COVID-19. Other findings indicate a significant statistical difference in the rate of using information resources during COVID-19 based on age and gender; however, this difference is not significant regarding the reliability of information resources with regard to age and gender. Health information has an undisputable role in the prevention and control of pandemic diseases such as COVID-19. Providing accurate, reliable, and evidence-based information in a timely manner for the use of resources and information channels related to COVID-19 can be a fast and low-cost strategic approach in confronting this disease.

scholarly journals Designing of an Advanced Compression Bioreactor with an Implementation of a Low-Cost Controlling System Connected to a Mobile Application

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 915
Author(s):  
Gözde Dursun ◽  
Muhammad Umer ◽  
Bernd Markert ◽  
Marcus Stoffel
Keyword(s):  
Mobile Application ◽  
Low Cost ◽  
Experimental Information ◽  
Raspberry Pi ◽  
Tissue Constructs ◽  
Cost Controlling ◽  
Controlling System ◽  
And Control ◽  
Tissue Models

(1) Background: Bioreactors mimic the natural environment of cells and tissues by providing a controlled micro-environment. However, their design is often expensive and complex. Herein, we have introduced the development of a low-cost compression bioreactor which enables the application of different mechanical stimulation regimes to in vitro tissue models and provides the information of applied stress and strain in real-time. (2) Methods: The compression bioreactor is designed using a mini-computer called Raspberry Pi, which is programmed to apply compressive deformation at various strains and frequencies, as well as to measure the force applied to the tissue constructs. Besides this, we have developed a mobile application connected to the bioreactor software to monitor, command, and control experiments via mobile devices. (3) Results: Cell viability results indicate that the newly designed compression bioreactor supports cell cultivation in a sterile environment without any contamination. The developed bioreactor software plots the experimental data of dynamic mechanical loading in a long-term manner, as well as stores them for further data processing. Following in vitro uniaxial compression conditioning of 3D in vitro cartilage models, chondrocyte cell migration was altered positively compared to static cultures. (4) Conclusion: The developed compression bioreactor can support the in vitro tissue model cultivation and monitor the experimental information with a low-cost controlling system and via mobile application. The highly customizable mold inside the cultivation chamber is a significant approach to solve the limited customization capability of the traditional bioreactors. Most importantly, the compression bioreactor prevents operator- and system-dependent variability between experiments by enabling a dynamic culture in a large volume for multiple numbers of in vitro tissue constructs.

scholarly journals Multi-Blockchain-Based IoT Data Processing Techniques to Ensure the Integrity of IoT Data in AIoT Edge Computing Environments

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3515
Author(s):  
Sung-Ho Sim ◽  
Yoon-Su Jeong
Keyword(s):  
Low Cost ◽  
Third Party ◽  
Monitoring And Control ◽  
Constant Size ◽  
Computing Environments ◽  
Iot Devices ◽  
Cloud Servers ◽  
The Cost ◽  
Processing Techniques ◽  
And Control

As the development of IoT technologies has progressed rapidly recently, most IoT data are focused on monitoring and control to process IoT data, but the cost of collecting and linking various IoT data increases, requiring the ability to proactively integrate and analyze collected IoT data so that cloud servers (data centers) can process smartly. In this paper, we propose a blockchain-based IoT big data integrity verification technique to ensure the safety of the Third Party Auditor (TPA), which has a role in auditing the integrity of AIoT data. The proposed technique aims to minimize IoT information loss by multiple blockchain groupings of information and signature keys from IoT devices. The proposed technique allows IoT information to be effectively guaranteed the integrity of AIoT data by linking hash values designated as arbitrary, constant-size blocks with previous blocks in hierarchical chains. The proposed technique performs synchronization using location information between the central server and IoT devices to manage the cost of the integrity of IoT information at low cost. In order to easily control a large number of locations of IoT devices, we perform cross-distributed and blockchain linkage processing under constant rules to improve the load and throughput generated by IoT devices.

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