The Transient Character of the Near-Field Acoustic Radiation From a Cylindrical Diaphragm Excited by Water Hammer Transients

1971 ◽  
Vol 93 (4) ◽  
pp. 1216-1224
Author(s):  
B. W. Davis ◽  
E. E. Weynand
Keyword(s):  
Produced Water ◽  
Acoustic Radiation ◽  
Mechanical Design ◽  
Near Field ◽  
Experimental System ◽  
Wave Pattern ◽  
Water Hammer ◽  
Compressive Wave ◽  
Surrounding Water ◽  
Time Space

An investigation of the transient character of the near-field acoustic radiation from a water hammer excited, cylindrical diaphragm was conducted. The investigation was principally experimental and focused on relating the radiated waveforms to pressure transients within the pipe. The basic experimental system consisted of a length of rigid pipe extending from a flow source into a large sonar tank. The rigid pipe was interrupted by a cylindrical section of elastomeric tubing which served as a diaphragm and, thus, as an acoustic coupler between the water inside the pipe and water surrounding the pipe. A quick-closing valve downstream of the diaphragm produced water hammer transients which were coupled to the surrounding water through the diaphragm and were monitored in the near-field by hydrophones. The physical system geometry was varied to include data for a range of pipe sizes from 0.5 in. to 4.0 in. inside dia and from 10 ft to 34 ft in length. The experiments revealed that two distinct major waves could always be identified in each radiated wave pattern. One was found to originate from the primary water hammer compressive wave downstream of the diaphragm. The other major wave was attributed to a precursor wave which originated upstream of the diaphragm. The propagation paths of the two waves are identified and it is shown that their relation to one another in time space is a predictable function of geometry. It is estimated, by extrapolating from the experimental data, that an acoustic pressure in excess of 88 psi at one yard is possible from a system of realistic mechanical design.

Acoustic radiation simulation and pre-stress effect on compact acoustic levitation platform

2019 ◽  
Vol 33 (07) ◽  
pp. 1950080 ◽  
Author(s):  
Bin Wei ◽  
Yongyong He ◽  
Wei Wang
Keyword(s):  
Pressure Distribution ◽  
Acoustic Radiation ◽  
Near Field ◽  
Parameters Optimization ◽  
Squeeze Film ◽  
Acoustic Levitation ◽  
Stress Effect ◽  
Biological Engineering ◽  
Loop Control ◽  
Close Loop Control

In order to satisfy the requirements of precise components with tidiness, low power and high stability in the field of biological engineering, medical equipment and semiconductors etc. a pre-stress acoustic transport prototype without horn was proposed in this paper. The mechanism of levitation and transport which is driven by orthogonal waves was revealed by the analysis of waveform and squeeze film characteristics in high-frequency exciting condition; also, the electric, solid and acoustic coupled finite element method (FEM) was established to investigate the effect of pre-stress and acoustic pressure distribution in the near field. The levitation and driving capacity of near field acoustic levitation (NFAL) transport platform without horns can be proved in this experiment and further to achieve the goal of parameters optimization. The theoretical and experimental results indicate that the pre-stress has a significant effect on resonant frequency and levitating stability, the pre-stress are determined by the DC voltage offset which is related to the system working point so that we cannot increase the offset and exciting voltage unlimitedly to improve the stability. At the same time, the calculated pressure distribution of acoustic radiation can generally reflect the regional bearing capacity in near and far field for levitation. These achievements can partly solve the problem of accuracy design of prototype and thickness of gas film, supporting for accuracy close loop control of levitating height.

Design and Analysis of a Camera and Sensor Positioning Mechanism for ARIES: An Autonomous Mobile Robot

1998 ◽  
Author(s):  
David N. Rocheleau ◽  
Matthew M. Moore
Keyword(s):  
South Carolina ◽  
Mobile Robot ◽  
Mechanical Design ◽  
Experimental System ◽  
Department Of Energy ◽  
Autonomous Mobile Robot ◽  
University Of South Carolina ◽  
Clemson University ◽  
Lift Mechanism ◽  
Sensor Package

Abstract ARIES (Autonomous Robotic Inspection Experimental System) is a program for the Department of Energy (DOE) that was charged with the mission of surveying and inspecting drums containing low-level radioactive waste stored in warehouses at DOE facilities. This paper reports on the final development of the ARIES project, and focuses on the mechanical design and analysis of three mechanisms that position a camera and sensor package that sits atop a Cybermotion K3A mobile robotic platform. The ARIES project was executed through a joint effort of three parties: University of South Carolina (USC), Clemson University, and Cybermotion, Inc., of Salem, Virginia. The goal of the project was to develop an autonomous mobile robot that positions a data acquisition package (DAP) which surveys drums containing hazardous materials in Department of Energy (DOE) warehouses. The unique mechanical design of the positioning system is comprised of three distinct components: a lift mechanism, a fourbar mechanism, and a camera panning mechanism. The components are integrated in a manner that allows the DAP to be positioned from 0 to 16 feet off the ground while the robot maneuvers through aisles of drums in a warehouse. The three mechanisms, and the integration thereof, are reported in this paper.

scholarly journals A Lab-Scale Experiment Approach to the Measurement of Wall Pressure from Near-Field under Water Explosions by a Hopkinson Bar

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Xiongwei Cui ◽  
Xiongliang Yao ◽  
Yingyu Chen
Keyword(s):  
Shock Wave ◽  
Near Field ◽  
Underwater Explosion ◽  
Experimental System ◽  
Hopkinson Bar ◽  
Wall Pressure ◽  
Pressure Loading ◽  
Target Plate ◽  
Wave Pressure ◽  
Shock Wave Pressure

Direct measurement of the wall pressure loading subjected to the near-field underwater explosion is of great difficulty. In this article, an improved methodology and a lab-scale experimental system are proposed and manufactured to assess the wall pressure loading. In the methodology, a Hopkinson bar (HPB), used as the sensing element, is inserted through the hole drilled on the target plate and the bar’s end face lies flush with the loaded face of the target plate to detect and record the pressure loading. Furthermore, two improvements have been made on this methodology to measure the wall pressure loading from a near-field underwater explosion. The first one is some waterproof units added to make it suitable for the underwater environment. The second one is a hard rubber cylinder placed at the distal end, and a pair of ropes taped on the HPB is used to pull the HPB against the cylinder hard to ensure the HPB’s end face flushes with loaded face of the target plate during the bubble collapse. To validate the pressure measurement technique based on the HPB, an underwater explosion between two parallelly mounted circular target plates is used as the validating system. Based on the assumption that the shock wave pressure profiles at the two points on the two plates which are symmetrical to each other about the middle plane of symmetry are the same, it was found that the pressure obtained by the HPB was in excellent agreement with pressure transducer measurements, thus validating the proposed technique. To verify the capability of this improved methodology and experimental system, a series of minicharge underwater explosion experiments are conducted. From the recorded pressure-time profiles coupled with the underwater explosion evolution images captured by the HSV camera, the shock wave pressure loading and bubble-jet pressure loadings are captured in detail at 5  mm, 10  mm, …, 30  mm stand-off distances. Part of the pressure loading of the experiment at 35  mm stand-off distance is recorded, which is still of great help and significance for engineers. Especially, the peak pressure of the shock wave is captured.

scholarly journals An Overshoot-Constrained Fast Setpoint Control for Nanopositioning Systems with Switched Controllers

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Zhizheng Wu ◽  
Tengfei Yue ◽  
Xinxiang Jiang ◽  
Ning Cao ◽  
Feng Li ◽  
...  
Keyword(s):  
Pid Controller ◽  
Closed Loop ◽  
Control Method ◽  
Near Field ◽  
Experimental System ◽  
Matrix Inequalities ◽  
Closed Loop System ◽  
Synthesis Algorithm ◽  
Key Technology ◽  
Near Field Optics

Nanopositioning control as the key technology has been applied in many fields such as near-field optics, biomedical engineering, and nanomanipulation, where it is required to possess high positioning accuracy, reliability, and speed. In this paper, a switched PID controller-based fast setpoint control method is proposed for nanopositioning systems. In order to improve the setpoint speed of the nanopositioning system without a large overshoot, a switched controller consisting of the approach mode and smooth mode is synthesized. The overshoot constraint of the resulting switched closed-loop system is investigated within a set of bilinear matrix inequalities, based on which the search of the controller parameters can be further processed by solving the properly formulated synthesis algorithm. The proposed control method is evaluated in a nanopositioning experimental system driven by a PZT actuator, and the experimental results demonstrate the effectiveness of the switched PID controller for the fast setpoint approaching operation.

Effects of Quay Wall and Seabed Reflection on the AUV Acoustic Radiation Test Analysis

2014 ◽  
Vol 599-601 ◽  
pp. 922-926
Author(s):  
Guo Liang Xu ◽  
Qi Wei He ◽  
Shao Chun Ding ◽  
Hai Bo Wan
Keyword(s):  
Acoustic Field ◽  
Field Test ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Near Field ◽  
Test Analysis ◽  
Complex Sound ◽  
Quay Wall ◽  
Radiation Test ◽  
Acoustical Holography

To analyze effects of quay environment on the AUV radiated acoustic field test, the PNAH (PNAH: planar near-field acoustical holography) was used to simulate acoustic field. By simulating the free and non-free acoustic field and comparing amplitudes and angles of complex sound pressure, Analyze effects of quay wall and seabed reflection on the AUV radiated acoustic field test to determine the standard of quay wall and seabed environment which meets testing. The work would provide a certain reference for the AUV radiated acoustic field test.

Noncontact Planar Stage Based on Near-Field Acoustic Transportation

2020 ◽  
Vol 8 (2) ◽  
Author(s):  
Yang Yang ◽  
Keyu Chen ◽  
Ping Guo
Keyword(s):  
Reynolds Equation ◽  
Closed Loop ◽  
Acoustic Radiation ◽  
Dimensional Space ◽  
Near Field ◽  
Radiation Force ◽  
Driving Mechanism ◽  
Two Dimensional ◽  
Closed Loop System ◽  
Novel Design

Abstract Acoustic radiation force in the near-field of a vibrating source can be utilized to lift and transport objects, which provides a noncontact driving technology in addition to maglev. This paper presents a novel design of a self-levitated planar stage based on near-field acoustic transportation. A closed-loop system is proposed to design a capacitance surface encoder to provide direct two-dimensional (2D) position feedback. A dynamic model based on the Reynolds equation is established to study its driving mechanism. A prototype including the levitation stage, encoder, and controller is implemented to demonstrate the potential of arbitrary trajectory tracking in two-dimensional space.

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