Oscillations in Moonpool at Static Platform in Waves

2007 ◽  
Author(s):  
Sadiq Salman ◽  
Zhuang Kang ◽  
Xiong-Liang Yao
Keyword(s):  
Wave Height ◽  
Noise Level ◽  
Sound Level ◽  
Actual State ◽  
Offshore Platforms ◽  
Forward Speed ◽  
Structural Elements ◽  
Fluid Medium ◽  
Time Period ◽  
Calm Water

Most of the offshore platforms at sea are static and considered as rigid. This paper presents a series of towing tank experimental research to understand the wave and structure interaction for moonpool installed at static platform. It also gives a comparison of results between static platforms in waves and model moving in calm water with forward speed. Study comprised of circular and square shaped moonpool, while square shaped was further investigated for different attack angles varying from 0–45 degrees with an interval of 15°. Time period of incoming waves was increased from 1 s to 3 s with an interval of 1 s. To have a variety of situations to cater for the actual state at sea, wave height was also increased from 40 mm to 80 mm with an interval of 20 mm. For wave height and time period different combinations are presented to get variety of results. Results are given in terms of ‘dB’ for water oscillation pressure, which governs the water motions inside the moonpool, and for that matter it directly relates resonance in moonpool as the natural frequency of water inside the cavity does not change with a change in the velocity of incoming waves rather it is dependents upon the physical properties of the fluid medium, shape of cavity, size of cavity and the draught of water inside the cavity. With an increase in the time period of incoming waves, sound level ‘dB’ in terms of oscillation pressure frequency generated by the circular moonpool also increases. The same phenomenon is observed once the wave height is increased from 40–80 mm; except for one condition i.e., T = 3 s and λ = 80 mm. This shows that longer and higher waves may not always produce higher noise level for circular moonpools; this is not the case for square shaped moonpool. At increasing attack angles for square shaped moonpool, the acoustic level increases slightly for similar wave conditions. Furthermore, while comparing moving model in calm water with forward speed and static model at in coming waves; it was revealed that, square moonpool at different attack angles in calm water with forward speed condition, produces greater noise level once compared with waves-only condition. This phenomenon is unlike in circle moonpool. The results given in this paper are very important structural elements of the offshore platform during the design process.

Experimental Research on Flow Induced Oscillations in Moonpool Encountered Through Waves

2007 ◽  
Author(s):  
Zhuang Kang ◽  
Xiongliang Yao ◽  
Sadiq Salman
Keyword(s):  
Wave Height ◽  
Experimental Research ◽  
Flow Condition ◽  
Frequency Ratio ◽  
Pressure Sensors ◽  
Breaking Waves ◽  
Green Water ◽  
Wave Condition ◽  
Time Period ◽  
Calm Water

Model experiments in this paper explains the response of the moonpool encountered through waves at different wave heights, time periods and attack angles, which reflect close to real situation at sea for ships equipped with moonpool. EMD method is used to have a meaningful data collected through hydrophone, pressure sensors, acceleration sensor and wave height meter. Results show that fluid natural oscillating frequency remains constant at 0.7 Hz in calm water with forward model speed condition (Fr = 0.26∼1.3), while by increasing the time period, wave height or both; it fluctuates between 0.6 Hz∼0.9 Hz. The fluid inside the moonpool faces internal sloshing, resulting in transverse breaking waves that are added to the vertical motions. Sloshing motion in the moonpool couples with the piston mode due to which results of calm water with forward speed, and combined waves and flow condition are quite different. Square shaped moonpool at different attack angles and circular shaped moonpool are also discussed for fluctuating pressure level (dB) at increasing time period and wave height. Moreover, Oscillation pressure results at only-wave condition and wave and flow condition together are represented by using frequency ratio between ‘oscillation pressure frequency’ and ‘sloshing natural frequency’ with varying ‘KC’ number. KC varies from 4.16 to 5.67 at 1-sec time period having frequency ratio f/fo of 1. Once time period increases to 2-sec, KC becomes around 22.69 at same frequency ratio. Dynamic magnification due to waves and flow combined situation may cause slamming on diving bells or ROV that are launched, green water over the edge of the moonpool which can be dangerous for the crew, or can increase drastically the resistance of the vessel in transit conditions therefore, this experimental research gives very important factors and results for designing moonpool; we believe that this paper has a significant contribution in the permanent literature.

scholarly journals Analysis of frequency spectrum of outboard motor Hangkai 4.0 noise when nosing

2020 ◽  
Vol 2020 (3) ◽  
pp. 33-39
Author(s):  
Mikhail Nikolaevich Pokusaev ◽  
Konstantin Evgenievich Khmelnitsky
Keyword(s):  
Frequency Spectrum ◽  
Noise Level ◽  
External Noise ◽  
Sound Level ◽  
Structural Elements ◽  
Small Vessels ◽  
Measuring Devices ◽  
Full Speed ◽  
Level Meter ◽  
Average Noise Level

The article deals with the results of experiments on measuring the Hangkai 4.0 outboard motor when using various types of noise-insulating hoods. The tests were carried out in accordance with GOST ISO 14509-1-2015 “Small Vessels. Noise measurement of small motor pleasure craft. Part 1. Noise of a passing ship” at full speed with the engine speed 4500 rev/min and motor power 4 HP. Measurements were carried out when the vessel was at a distance of 25 metres both sides with different options covering outboard motor. The average noise level and its frequency spectrum were measured, and the effectiveness of various types of hoods was evaluated. In the course of the experiment there was used a standard plastic hood of the Hangkai 4.0 engine, a noise-insulating hood (plastic hood, glued inside with automotive foil noise insulation) and an author's combined noise-insulating hood Kaponistr. Description and structural elements of Kaponistr are presented; it has been stated that the hood design was patented as a useful model in 2019. In the result of conducted experiments it has been inferred that the external noise level of the Hangkai 4.0 outboard motor (without hood) does not exceed 74.3 dBA, but is at the level of the permissible value of 75 dBA, so, when operating, the motor needs a standard hood. The prevailing frequency range of an outboard boat motor is within 300 - 2500 Hz. It has been inferred that each type of nosing (standard, sound-proof, combined, without hood) reduces the noise level of the outboard motor. The greatest effect of reducing external noise is observed when using a combined hood Kaponistr at a frequency of 800 Hz by 19.4 dBA or by 27%. In the research there were used the control and measuring devices (sound level meter, vibrometer, spectrum analyzer Ekofizika-110 (white); acoustic calibrator AK-1000) and software (Signal+3G Light manufactured by PKF Digital Instruments, LLC).

DEPENDENCE OF THE NOISE LEVEL OF DRY FAN COOLING TOWERS ON THE POWER OF THERMAL POWER PLANTS

2021 ◽  
Author(s):  
Владимир Борисович Тупов ◽  
Айнур Булатович Мухаметов
Keyword(s):  
Noise Level ◽  
Power Plants ◽  
Thermal Power ◽  
Electrical Power ◽  
Sound Level ◽  
Thermal Power Plants ◽  
Cooling Towers ◽  
Surrounding Area ◽  
Fan Cooling

Сухие вентиляторные градирни тепловых электрических станций могут быть источником превышения санитарных норм на территории станции и в окружающем районе. В статье проведен анализ уровня шума сухих вентиляторных градирен в зависимости от мощности тепловых электрических станций. Получена формула позволяющая определить изменение уровня звука сухих вентиляторных градирен в зависимости от электрической мощности тепловых электрических станций. Dry fan cooling towers of thermal power plants can be a source of exceeding sanitary standards on the territory of the plant and in the surrounding area. The article analyzes the noise level of dry fan cooling towers depending on the power of thermal power plants. A formula has been obtained that makes it possible to determine the change in the sound level of dry fan cooling towers depending on the electrical power of thermal power plants.

Elevated Sound Levels within a Busy NICU

2005 ◽  
Vol 24 (6) ◽  
pp. 33-37 ◽  
Author(s):  
Charlene Krueger ◽  
Susan Wall ◽  
Leslie Parker ◽  
Rose Nealis
Keyword(s):  
Preterm Infants ◽  
Noise Level ◽  
Sound Level ◽  
Behavioral Effects ◽  
Outcome Variable ◽  
Sound Levels ◽  
Main Outcome Variable

Purpose: Elevated sound levels in the NICU may contribute to undesirable physiologic and behavioral effects in preterm infants. This study describes sound levels in a busy NICU in the southeastern U.S. and compares the findings with recommended NICU noise level standards.Design: NICU sound levels were recorded continuously at nine different locations within the NICU. Hourly measurements of loudness equivalent (Leq) sound level, sound level exceeded 10 percent of the time (L10), and maximum sound level (Lmax) were determined.Sample: Sound levels were sampled from nine different locations within the NICU.Main Outcome Variable: Sound levels are described using the hourly, A-weighted Leq, L10, and Lmax.Results: The overall average hourly Leq (M = 60.44 dB, range = 55–68 dB), L10 (M = 59.26 dB, range = 55–66 dB), and Lmax (M = 78.39, range = 69–93 dB) were often above the recommended sound levels (hourly Leq <50 dB, L10 <55 dB, and 1-second Lmax <70 dB). In addition, certain times of day, such as 6–7 AM and 10 AM–12 noon, were noisier than other times of day.

Development of Operational Limit Diagrams for Offshore Lifting Procedures

2015 ◽  
Author(s):  
Leonardo Roncetti ◽  
Fabrício Nogueira Corrêa ◽  
Carl Horst Albrecht ◽  
Breno Pinheiro Jacob
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Technological Development ◽  
Automatic Generation ◽  
Dynamic Responses ◽  
Offshore Platforms ◽  
Peak Period ◽  
Significant Wave ◽  
Wave Heights ◽  
Offshore Crane

Lifting operations with offshore cranes are fundamental for proper functioning of a platform. Despite the great technological development, offshore cranes load charts only consider the significant wave height as parameter of environmental load, neglecting wave period, which may lead to unsafe or overestimated lifting operations. This paper aims to develop a method to design offshore crane operational limit diagrams for lifting of personnel and usual loads, in function of significant wave height and wave peak period, using time domain dynamic analysis, for a crane installed on a floating unit. The lifting of personnel with crane to transfer between a floating unit and a support vessel is a very used option in offshore operations, and this is in many cases, the only alternative beyond the helicopter. Due to recent fatal accidents with lifting operations in offshore platforms, it is essential the study about this subject, contributing to the increase of safety. The sea states for analysis were chosen covering usual significant wave heights and peak periods limits for lifting operations. The methodology used the SITUA / Prosim software to obtain the dynamic responses of the personnel transfer basket lifting and container loads on a typical FPSO. Through program developed by the author, it was implemented the automatic generation of diagrams as a function of operational limits. It is concluded that using this methodology, it is possible to achieve greater efficiency in the design and execution of personnel and routine load lifting, increasing safety and a wider weather window available.

scholarly journals ANALISIS TINGKAT KEBISINGAN LINGKUNGAN DI KELURAHAN PAHANDUT KECAMATAN PAHANDUT KOTA PALANGKA RAYA KALIMANTAN TENGAH

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Muh Azhari ◽  
Rudy Yoga Lesmana
Keyword(s):  
Noise Level ◽  
Qualitative Method ◽  
Air Transportation ◽  
Sound Level ◽  
Sound Level Meter ◽  
Google Maps ◽  
Average Value ◽  
The Third ◽  
Level Ii ◽  
Level Meter

Permasalahan lingkungan dari usaha kegiatan manusia untuk memenuhi kebutuhan hidup, seperti sandang, pangan, papan dan transportasi harus dilakukan penanganan dengan baik. Misalnya seperti pengaruh kegiatan transportasi udara terhadap kondisi kualitas lingkungan setempat  seperti kegiatan di Bandara Cilik Riwut Kelurahan Pahandut, Kecamatan Pahandut, Kota Palangka Raya Kalimantan Tengah. Metode penelitian yang digunakan merupakan metode kualitatif dengan analisis data instrumen seperti Sound Level Meter Instrument, Anemometer, GPS, Flight Radar, Google Maps Application & WECPNL Instrument (Weighted Equivalent Continuous Perceived Noise Level)  dan pengambilan data dilakukan selama tiga hari sesuai dengan kedatangan dan keberangkatan pesawat. Hasil penelitian dengan analisis WECPNL menunjukkan bahwa tingkat kebisingan di hari ke 2 lebih besar dibandingkan hari ke 3 dan hari ke 3 lebih besar dari hari ke 1 (87,2  > 82,2 > 75,9) dengan nilai rata-rata WECPNL sebesar 81,7. Kebisingan di bandara Cilik Riwut di Kota Palangka Raya Kalimantan Tengah termasuk kebisingan regional tingkat II dan III. Kegiatan yang dapat dilakukan untuk meminimalisir Risiko kebisingan tersebut yaitu dengan melakukan kegiatan rekayasa keteknikan dan menanam vegetasi yang berfungsi mengurangi kebisingan Kata kunci: Bandara, Kebisingan, Lingkungan. The environmental problems of the efforts of human activities to meet the needs of life, such as clothing, food, housing and transportation must be handled properly. For example, such as the influence of air transportation activities on local environmental quality conditions such as activities at Cilik Riwut Airport, Pahandut Village, Pahandut District, Palangka Raya City, Central of Kalimantan. The research method used is a qualitative method with data analysis instruments such as Sound Level Meter Instrument, Anemometer, GPS, Flight Radar, Google Maps Application and WECPNL Instrument (Weighted Equivalent Continuous Percepived Noise) and data collection is carried out for three days in accordance with the arrival and departure of the aircraft. Results of research with  WECPNL analysis show that the noise level on the second day is greater than the third day and the third day is greater than the first day (87,2  > 82,2 > 75,9) with  score average value is 81,7. Noise at Cilik Riwut airport in Palangka Raya City, Central Kalimantan including regional level II and III noise. activities that can be carried out are carrying out engineering activities and planting vegetation which have the function of reducing noise. Keyword: Airport, Environmental, Noice.

scholarly journals Appraisal of Noise Level Dissemination Surrounding Mining and Industrial Areas of Keonjhar, Odisha: a Comprehensive Approach Using Noise Mapping

2017 ◽  
Vol 42 (3) ◽  
pp. 423-432 ◽  
Author(s):  
Satish K. Lokhande ◽  
Satyajeet A. Dhawale ◽  
Samir S. Pathak ◽  
Rakesh Gautam ◽  
Mohindra C. Jain ◽  
...  
Keyword(s):  
Noise Level ◽  
Sound Level ◽  
Noise Levels ◽  
Night Time ◽  
Noise Mapping ◽  
High Noise ◽  
Sensitive Areas ◽  
Sound Levels ◽  
Directorate General ◽  
Open Cast

Abstract Noise mapping is a well-established practice among the European nations, and it has been follow for almost two decades. Recently, as per guidelines of the Directorate General of Mines Safety (DGMS), India, noise mapping has been made mandatory in the mining expanses. This study is an effort to map the noise levels in nearby areas of mines in the northern Keonjhar district. The motive of this study is to quantify the existing A-weighted time-average sound level (LAeq,T ) in the study area to probe its effects on the human dwellings and noise sensitive areas with the probability of future development of the mines, roads, and industrial and commercial zone. The LAeq,T was measured at 39 identified locations, including industrial, commercial, residential, and sensitive zones, 15 open cast mines, 3 major highways, and 3 haulage roads. With the utilisation of Predictor LimA Software and other GIS tools, the worked out data is mapped and noise contours are developed for the visualisation and identification of the extent and distribution of sound levels across the study area. This investigation discloses that the present noise level at 60% of the locations in silence and residential zone exposed to significantly high noise levels surpasses the prescribed limit of Central Pollution Control Board (CPCB), India. The observed day and night time LAeq, T level of both zones ranged between 43.2-62.2 dB(A) and 30.5-53.4 dB(A), respectively, whereas, the average Ldn values vary between 32.7 and 51.2 dB(A). The extensive mobility of heavy vehicles adjoining the sensitive areas and a nearby plethora of open cast mines is the leading cause of exceeded noise levels. The study divulges that the delicate establishments like schools and hospitals are susceptible to high noise levels throughout the day and night. A correlation between observed and software predicted values gives R2 of 0.605 for Ld, 0.217 for Ln, and 0.524 for Ldn. Finally, the mitigation measure is proposed and demonstrated using a contour map showing a significant reduction in the noise levels by 0-5.3 dB(A).

scholarly journals Assessment of traffic noise due to transverse rumble strips at residential areas

2018 ◽  
Vol 250 ◽  
pp. 02006
Author(s):  
Zaiton Haron ◽  
Darus Nadirah ◽  
Supandi Mohamad Afif ◽  
Yahya Khairulzan ◽  
Nordiana Mashros ◽  
...  
Keyword(s):  
Noise Level ◽  
Traffic Noise ◽  
Middle Layer ◽  
Sound Level ◽  
Skid Resistance ◽  
Residential Areas ◽  
Noise Levels ◽  
Traffic Characteristics ◽  
Level Meter ◽  
Road Characteristics

Transverse rumble strips (TRS) are commonly being installed to alert the drivers through sound and vibration effects. The sound produced affects the existing traffic noise level which caused noise annoyance to the nearby residents. This study aims to assess the traffic noise due to TRS at residential areas by determining the roadside noise levels, traffic and road characteristics and evaluating the relationship between these parameters. Middle overlapped (MO), middle layer overlapped (MLO) and raised rumbler (RR) TRS profiles with same thickness were selected. The measurements of roadside noise levels and skid resistance were conducted using sound level meter (SLM) and British pendulum tester (BPT) respectively. Traffic characteristics were evaluated using previous data measured using automatic traffic counter (ATC). In overall, MLO produced highest roadside noise levels with increase of 20.5dBA from baseline. Generally, the increase of roadside noise level due to TRS is strong with speed, weak to medium with skid resistance of TRS and no relationship with traffic volume. Based on three TRS profile types, MLO is not suitable to be installed on the roadways adjacent to the residential areas as the increase of roadside noise level is significant which is more than 5dBA compared to MO and RR.

An Analysis on the Occurrence of Noise between Floors in Apartment Housing

2015 ◽  
Vol 749 ◽  
pp. 406-409
Author(s):  
Jae Min Shin ◽  
Yoon Seok Shin
Keyword(s):  
Time Slot ◽  
Management Plan ◽  
Sound Level ◽  
Actual State ◽  
Noise Sources ◽  
Impact Noise ◽  
Airborne Noise ◽  
Standard Value ◽  
Household Members ◽  
The Individual

The purpose of this study is to determine the actual state of noise occurrence in apartment-unit households by utilizing state data to examine individual noise sources and the types of noise between floors. Among the types of noise between Floors, the top four noise sources were conversation and electrical appliance noise in the airborne noise category, and foot-stepping noise and object-dropping noise in the direct impact noise category. The result shows that in three sources (other than foot-stepping noise), the equivalent sound level was found to exceed the standard value in a specific time slot. The frequency of noise occurrence was shown to be highest between 18:00 and 21:00, after household members had come home from work. Therefore, to reduce noise between floors, a management plan should be introduced based on the actual state of the noise occurrence, considering the individual noise source and the time slot during which noise frequently occurs.

scholarly journals Influence of the Acoustic Cover of the Modular Expansion Joint on the Acoustic Climate in the Bridge Structure Surroundings

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2842
Author(s):  
Janusz Bohatkiewicz ◽  
Michał Jukowski ◽  
Maciej Hałucha ◽  
Marcin Dębiński
Keyword(s):  
Sound Level ◽  
Structural Elements ◽  
Expansion Joint ◽  
Expansion Joints ◽  
The Road ◽  
Sound Levels ◽  
Road Surfaces ◽  
Before And After ◽  
Bridge Structures

The noise generated at the interface between the wheels of vehicles and the road surface is well recognized in the literature worldwide. Many publications describe the phenomenon of reducing this kind of impact by silent road surfaces. A specific type of this noise is the sound generated by vehicles passing over the expansion joints of bridge structures. Due to the impulsive nature of this sound, it is very onerous for people living in the close vicinity of bridge structures. The passage of vehicles over expansion joints causes the formation of vibrations that are transmitted to the structural elements of bridge structures, which may cause the formation of the material sounds (especially arduous in the case of bridges with steel elements). An attempt to reduce this impact was made by making a prototype acoustic cover of the expansion joint on the selected bridge. The paper presents the results of research on the “in situ” acoustic effectiveness of this cover. Additionally, the noise was modelled in the object surroundings before and after the cover’s application. The acoustic efficiency of the cover in the whole measured frequency range was 5.3 dBA. In the narrower frequency bands (1/3 octave bands), larger sound level reductions were observed. The maximum sound levels measured under the tested dilatation were less than 10.0 dBA lower than the maximum sound levels measured under the reference dilatation.

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