Impact of THz Frequency on Underwater Acoustic Wave Propagation for Short Range Wireless Applications

CFD Letters ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 116-125
Author(s):  
Md Rabiul Awal ◽  
Muhammad Syarifuddin Yahya ◽  
Nurafnida Afrizal ◽  
Ahmad Zaki Annuar ◽  
Wan Hafiza Wan Hassan
Keyword(s):  
Sound Pressure ◽  
Pressure Field ◽  
Propagation Distance ◽  
Acoustic Propagation ◽  
Acoustic Wave Propagation ◽  
Element Analysis ◽  
Wireless Applications ◽  
Propagation Pattern ◽  
Propagation Medium ◽  
The Impact

Acoustic propagation in seawater is an important aspect of scientific investigation. However, the impact of the THz scale frequencies for acoustic propagation is not included in the studies. Thus, a finite element analysis of such propagation in a seawater medium is presented in this paper applying THz frequencies. A transmitter (circular with a diameter of 14 mm, a thickness of 3 mm) and a rectangular receiver (20×10×0.5 mm3) are designed to trace the variations in the propagation mediums. A propagation medium of seawater (70×40×60 mm3) with ice and softwood is modelled. A scale of frequencies (1 kHz to 1 THz) is applied to trace the impact on the propagation pattern. It is found that THz range frequencies provide a very small wavelength. As a result, the potential propagation distance is very small. As such, the sound pressure level, displacements of the receiver and pressure field shows very rapid drops in the magnitude. This work considers only 70 mm as propagation distance, yet the sharp decrement of performance parameters suggests that it is rather inconvenient to achieve useful efficiency using THz frequencies for acoustic propagation.

scholarly journals ACOUSTIC WAVE PROPAGATION IN HIGH SCALE IMPEDANCE MISMATCH MEDIUMS

2021 ◽  
Vol 22 (2) ◽  
pp. 1-9
Author(s):  
Md Rabiul Awal ◽  
Muzammil Jusoh ◽  
Muhammad Syarifuddin Yahya ◽  
Salisa Abdul Rahman ◽  
Ahmad Nazri Dagang ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Propagation ◽  
Pressure Level ◽  
Element Analysis ◽  
Significant Drop ◽  
Low Frequencies ◽  
Simulated Environment ◽  
Propagation Pattern ◽  
The Impact

A finite element analysis of acoustic propagation in a multilayered medium is presented in this paper. A circular transmitter (diameter 14 mm, thickness 3 mm) and a rectangular receiver (20×10×0.5 mm3) are set to detect the variations in the propagation pattern. A complex medium (70×40×60 mm3) composed of skin, fat, muscle, bone and liquid is designed in a simulated environment. A scale of frequencies (10 kHz to 2 MHz) is applied to trace the impact on the propagation pattern as well. It is found from the analysis that fat and liquid layers affect the acoustic propagation the most (-69 dB), which results in a significant drop in the received sound pressure level at the receiving end. Again, other than skin and fat layers, low frequencies (less than 1 MHz) are more beneficial in terms of sound pressure level. However, higher frequencies contribute to lower displacements at the receiving end, which will cause less power potential as well. ABSTRAK: Analisis elemen terhingga bagi penyebaran akustik dalam medium berlapis dibentangkan dalam kajian ini. Pemancar bulat (diameter 14 mm, ketebalan 3 mm) dan penerima segi empat tepat (20 × 10 × 0.5 mm3) diatur bagi mengesan perubahan pola penyebaran. Medium kompleks (70 × 40 × 60 mm3) yang terdiri daripada kulit, lemak, otot, tulang dan cecair direka dalam persekitaran simulasi. Skala frekuensi (10 kHz hingga 2 MHz) digunakan bagi mengesan corak penyebaran. Dapatan kajian menunjukkan bahawa lapisan lemak dan cecair mempengaruhi penyebaran akustik (-69 dB), yang mengakibatkan penurunan mendadak tahap penerimaan tekanan bunyi di hujung penerima. Selain lapisan kulit dan lemak, frekuensi rendah (kurang dari 1 MHz) adalah lebih berguna dari segi tahap tekanan suara. Walau bagaimanapun, frekuensi lebih tinggi menyebabkan kurang anjakan di hujung penerima, sekaligus mengurangkan potensi daya tenaga.

Broadband liner impedance eduction for multimodal acoustic propagation in the presence of a mean flow

2016 ◽  
Vol 11 (2) ◽  
pp. 150-155
Author(s):  
R. Troian ◽  
D. Dragna ◽  
C. Bailly ◽  
M.-A. Galland
Keyword(s):  
Numerical Model ◽  
Flow Characteristics ◽  
Acoustic Propagation ◽  
Rational Fraction ◽  
Physical Parameters ◽  
Mean Flow ◽  
Linearized Euler Equations ◽  
Grazing Flow ◽  
Propagation Medium ◽  
Difference Time

Modeling of acoustic propagation in a duct with absorbing treatment is considered. The surface impedance of the treatment is sought in the form of a rational fraction. The numerical model is based on a resolution of the linearized Euler equations by finite difference time domain for the calculation of the acoustic propagation under a grazing flow. Sensitivity analysis of the considered numerical model is performed. The uncertainty of the physical parameters is taken into account to determine the most influential input parameters. The robustness of the solution vis-a-vis changes of the flow characteristics and the propagation medium is studied.

scholarly journals Potential and limitations of finite element modelling in assessing structural integrity of coralline algae under future global change

2015 ◽  
Vol 12 (19) ◽  
pp. 5871-5883 ◽  
Author(s):  
L. A. Melbourne ◽  
J. Griffin ◽  
D. N. Schmidt ◽  
E. J. Rayfield
Keyword(s):  
Climate Change ◽  
Finite Element ◽  
Structural Integrity ◽  
Geometric Model ◽  
Algal Growth ◽  
Coralline Algae ◽  
Rocky Shores ◽  
Element Analysis ◽  
Scan Data ◽  
The Impact

Abstract. Coralline algae are important habitat formers found on all rocky shores. While the impact of future ocean acidification on the physiological performance of the species has been well studied, little research has focused on potential changes in structural integrity in response to climate change. A previous study using 2-D Finite Element Analysis (FEA) suggested increased vulnerability to fracture (by wave action or boring) in algae grown under high CO2 conditions. To assess how realistically 2-D simplified models represent structural performance, a series of increasingly biologically accurate 3-D FE models that represent different aspects of coralline algal growth were developed. Simplified geometric 3-D models of the genus Lithothamnion were compared to models created from computed tomography (CT) scan data of the same genus. The biologically accurate model and the simplified geometric model representing individual cells had similar average stresses and stress distributions, emphasising the importance of the cell walls in dissipating the stress throughout the structure. In contrast models without the accurate representation of the cell geometry resulted in larger stress and strain results. Our more complex 3-D model reiterated the potential of climate change to diminish the structural integrity of the organism. This suggests that under future environmental conditions the weakening of the coralline algal skeleton along with increased external pressures (wave and bioerosion) may negatively influence the ability for coralline algae to maintain a habitat able to sustain high levels of biodiversity.

Impact Load Buffering Method Based on Stress Wave Attenuation Principle

2019 ◽  
Vol 11 (02) ◽  
pp. 1950019 ◽  
Author(s):  
Lin Gan ◽  
He Zhang ◽  
Cheng Zhou ◽  
Lin Liu
Keyword(s):  
Stress Wave ◽  
Wave Attenuation ◽  
Impact Load ◽  
Dynamics Simulation ◽  
Scanning System ◽  
Isolation Method ◽  
Element Analysis ◽  
System A ◽  
High Emission ◽  
The Impact

Rotating scanning motor is the important component of synchronous scanning laser fuze. High emission overload environment in the conventional ammunition has a serious impact on the reliability of the motor. Based on the theory that the buffer pad can attenuate the impact stress wave, a new motor buffering Isolation Method is proposed. The dynamical model of the new buffering isolation structure is established by ANSYS infinite element analysis software to do the nonlinear impact dynamics simulation of rotating scanning motor. The effectiveness of Buffering Isolation using different materials is comparatively analyzed. Finally, the Macht hammer impact experiment is done, the results show that in the experience of the 70,000[Formula: see text]g impact acceleration, the new buffering Isolation method can reduce the impact load about 15 times, which can effectively alleviate the plastic deformation of rotational scanning motor and improve the reliability of synchronization scanning system. A new method and theoretical basis of anti-high overload research for Laser Fuze is presented.

scholarly journals Characterizing the Impact of Doppler Effects on Body-Centric LoRa Links with SDR

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4049
Author(s):  
Thomas Ameloot ◽  
Marc Moeneclaey ◽  
Patrick Van Van Torre ◽  
Hendrik Rogier
Keyword(s):  
Wireless Communication ◽  
Low Power ◽  
Multipath Fading ◽  
Doppler Spread ◽  
Excellent Performance ◽  
Wireless Applications ◽  
Doppler Shifts ◽  
Doppler Effects ◽  
The Impact ◽  
Measurement Campaigns

Long-range, low-power wireless technologies such as LoRa have been shown to exhibit excellent performance when applied in body-centric wireless applications. However, the robustness of LoRa technology to Doppler spread has recently been called into question by a number of researchers. This paper evaluates the impact of static and dynamic Doppler shifts on a simulated LoRa symbol detector and two types of simulated LoRa receivers. The results are interpreted specifically for body-centric applications and confirm that, in most application environments, pure Doppler effects are unlikely to severely disrupt wireless communication, confirming previous research, which stated that the link deteriorations observed in a number of practical LoRa measurement campaigns would mainly be caused by multipath fading effects. Yet, dynamic Doppler shifts, which occur as a result of the relative acceleration between communicating nodes, are also shown to contribute to link degradation. This is especially so for higher LoRa spreading factors and larger packet sizes.

scholarly journals Noise at the time of COVID 19: The impact in some areas in Rome and Milan, Italy

Noise Mapping ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 248-264
Author(s):  
Rosa Maria Alsina Pagès ◽  
Francesc Alías ◽  
Patrizia Bellucci ◽  
Pier Paolo Cartolano ◽  
Ilaria Coppa ◽  
...  
Keyword(s):  
Sound Pressure ◽  
Traffic Noise ◽  
Motor Vehicles ◽  
Acoustic Environment ◽  
Commercial Activities ◽  
Real Time Traffic ◽  
Italian Regions ◽  
Almost All ◽  
The Impact

AbstractThe COVID-19 pandemic was confirmed in Italy at the end of January 2020, when the first positive cases for the virus were identified. At the beginning of March, the virus had spread to all Italian regions and on 10 March 2020 the lockdown phase began, limiting the movement of people and prohibiting almost all commercial activities, businesses and non-essential industries. As a result, millions of people were forced to stay at home, causing a drastic drop in traffic volume, which significantly changed the acoustic environment and air quality of cities. On 4 May 2020, the lockdown was partially lifted and activities were progressively reopened. Therefore, traffic gradually started to increase and, consequently, the noise emitted by motor vehicles. This behaviour was confirmed by the data collected by the DYNAMAP system, an automatic platform developed within the LIFE DYNAMAP project, providing real time traffic noise maps in terms of sound pressure levels and impacts at receivers (people and dwellings exposed to noise level bands). In this paper traffic and non-traffic-related noise events in the cities of Rome and Milan from March to May 2020 are analysed and compared to the corresponding values in 2019 to evaluate the effects of the lockdown period.

Response of Mild Steel Pipes Under High Mass Low Velocity Impacts

2014 ◽  
Author(s):  
Shamsoon Fareed ◽  
Ian May
Keyword(s):  
Finite Element ◽  
Mild Steel ◽  
Impact Energy ◽  
High Mass ◽  
Low Velocity ◽  
Element Analysis ◽  
Steel Pipes ◽  
Impact Tests ◽  
The Finite Element Analysis ◽  
The Impact

Accidental loads, for example, due to heavy dropped objects, impact from the trawl gear and anchors of fishing vessels can cause damage to pipelines on the sea bed. The amount of damage will depend on the impact energy. The indentation will be localized at the contact area of the pipe and the impacting object, however, an understanding of the extent of the damage due to an impact is required so that if one should occur in practice an assessment can be made to determine if remedial action needs to be taken to ensure that the pipeline is still serviceable. There are a number of parameters, including the pipe cross section and impact energy, which influence the impact behaviour of a pipe. This paper describes the response, and assesses the damage, of mild steel pipes under high mass low velocity impacts. For this purpose full scale impacts tests were carried out on mild steel pipe having diameter of 457 mm, thickness of 25.4 mm and length of 2000 mm. The pipe was restrained along the base and a 2 tonnes mass with sharp impactor having a vertical downward velocity of 3870 mm/sec was used to impact the pipe transversely with an impact energy of 16 kJ. It was found from the impact tests that a smooth indentation was produced in the pipe. The impact tests were then used for validation of the non-linear dynamic implicit analyses using the finite element analysis software ABAQUS. Deformations at the impact zone, the rebound velocity, etc, recorded in the tests and the results of the finite element analysis were found to be in good agreement. The impact tests and finite element analyses described in this paper will help to improve the understanding of the response of steel pipes under impact loading and can be used as a benchmark for further finite element modelling of impacts on pipes.

Sail Aero-Structures: Studying Primary Load Paths and Distortion

2005 ◽  
Author(s):  
Robert Ranzenbach ◽  
Zhenlong Xu
Keyword(s):  
Aerodynamic Load ◽  
Element Analysis ◽  
Strain Behavior ◽  
Construction Methods ◽  
Load Paths ◽  
Calculation Results ◽  
Computational Fluid Dynamics Cfd ◽  
Aerodynamic Field ◽  
The Impact ◽  
Primary Load

A method is described to conduct an integrated Fluid-Structure Interaction (FSI) simulation of sails that is based upon knowledge of the sail’s design shape geometry and membrane material properties. A Finite Element Analysis (FEA) of the sail structure and a Computational Fluid Dynamics (CFD) model of the aerodynamic field are combined and iteratively solved to compute the actual flying shape of the sail under aerodynamic load, the stress strain behavior of the sail membrane, the integrated aerodynamic forces produced by the sail such as driving force and heel moment, and the resulting loads on sheets, halyards, etc. An important contribution of this particular method is the incorporation of wrinkling phenomena into the FEA portion of the calculation. Results from a study of working sails for a 30’ MORC racing yacht designed by Nelson-Marek (NM) in the 1990’s are presented and discussed with particular emphasis on the variability of primary load paths with changing trim and sailing conditions as well as the impact of sail deformation in the direction of relatively small stresses that is often poorly addressed in many proprietary sail construction methods.

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