Reconstruction of the normal velocity distribution on the surface of an ultrasonic transducer from the acoustic pressure measured on a reference surface

2003 ◽  
Vol 49 (3) ◽  
pp. 354-360 ◽  
Author(s):  
O. A. Sapozhnikov ◽  
Yu. A. Pishchal’nikov ◽  
A. V. Morozov
Keyword(s):  
Velocity Distribution ◽  
Acoustic Pressure ◽  
Ultrasonic Transducer ◽  
Normal Velocity ◽  
Reference Surface

Pure Design Method for Aerofoils in Cascade

1969 ◽  
Vol 11 (5) ◽  
pp. 454-467 ◽  
Author(s):  
K. Murugesan ◽  
J. W. Railly
Keyword(s):  
Exact Solution ◽  
Velocity Distribution ◽  
Design Problem ◽  
Design Method ◽  
Tangential Velocity ◽  
Surface Velocity ◽  
Normal Velocity ◽  
Blade Design ◽  
Blade Shape

An extension of Martensen's method is described which permits an exact solution of the inverse or blade design problem. An equation is derived for the normal velocity distributed about a given contour when a given tangential velocity is imposed about the contour and from this normal velocity an initial arbitrarily chosen blade shape may be successively modified until a blade is found having a desired surface velocity distribution. Five examples of the method are given.

Simulation and Experiment Researches on Acoustic Field of Spherical Shell Focused Ultrasonic Transducer

2013 ◽  
Vol 770 ◽  
pp. 281-284
Author(s):  
Zhen Yin ◽  
Hua Li ◽  
Zi Yang Cao ◽  
Yu Can Fu
Keyword(s):  
Spherical Shell ◽  
Acoustic Field ◽  
Acoustic Pressure ◽  
Ultrasonic Transducer ◽  
Pressure Curve ◽  
Bending Vibration ◽  
Element Simulation ◽  
Ultrasonic Technology ◽  
Simulation And Experiment ◽  
Simulation Results

Aiming at the deficiency of existing focused ultrasonic technology, a new high-power Spherical Shell Focused Ultrasonic Transducer (SSFUT) was designed. The SSFUT is composed of a sandwich piezoelectric ultrasonic transducer and a bending vibration spherical shell. Simulation on acoustic field of SSFUT was carried out. the acoustic field pressure distribution nephogram and the axial acoustic pressure curve of the SSFUT were obtained. The consistency of finite element simulation results and experimental results was verified by testing. The research provides a theoretical basis for implementation and application of the new focused ultrasonic technology.

Simulation on Flow Field Induced by Vibration Surface of Low Frequency

2010 ◽  
Author(s):  
Ling Shen ◽  
Shuhong Liu ◽  
Yulin Wu
Keyword(s):  
Flow Field ◽  
Velocity Distribution ◽  
Numerical Computation ◽  
High Frequency ◽  
Ultrasonic Transducer ◽  
Sewage Treatment ◽  
Low Frequency ◽  
Vibration Source ◽  
Water Tank ◽  
Industrial Cleaning

Ultrasonic cavitation generated by high-frequency ultrasonic transducer is widely studied because this phenomenon could be applied in a great variety of fields, including medical therapy, industrial cleaning as well as sewage treatment. Flow field influenced by vibration source of low frequency, however, is less studied. For the present study, a water tank of 1000×600×500mm is investigated when a vibration surface that represents a transducer of less frequency vibrates in the vicinity of one wall. Numerical computation based on the method of dynamic mesh is applied. Furthermore, two different vibration patterns are simulated, i.e., piston movement and drumhead vibration. Results show different pressure and velocity distribution within water tank when vibration surface is working at various frequencies and amplitudes. Differences of the flow fields are found between these circumstances, and similarity is found with that induced by ultrasonic transducer. Analysis on differences is discussed for further study.

scholarly journals 3D steerable, acoustically powered microswimmers for single-particle manipulation

2019 ◽  
Vol 5 (10) ◽  
pp. eaax3084 ◽  
Author(s):  
Liqiang Ren ◽  
Nitesh Nama ◽  
Jeffrey M. McNeill ◽  
Fernando Soto ◽  
Zhifei Yan ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Chemical Engineering ◽  
Acoustic Pressure ◽  
Ultrasonic Transducer ◽  
Acoustic Streaming ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Propulsive Force ◽  
Particle Manipulation ◽  
Bjerknes Force

The ability to precisely maneuver micro/nano objects in fluids in a contactless, biocompatible manner can enable innovative technologies and may have far-reaching impact in fields such as biology, chemical engineering, and nanotechnology. Here, we report a design for acoustically powered bubble-based microswimmers that are capable of autonomous motion in three dimensions and selectively transporting individual synthetic colloids and mammalian cells in a crowded group without labeling, surface modification, or effect on nearby objects. In contrast to previously reported microswimmers, their motion does not require operation at acoustic pressure nodes, enabling propulsion at low power and far from an ultrasonic transducer. In a megahertz acoustic field, the microswimmers are subject to two predominant forces: the secondary Bjerknes force and a locally generated acoustic streaming propulsive force. The combination of these two forces enables the microswimmers to independently swim on three dimensional boundaries or in free space under magnetical steering.

Modification of Near-Wall Turbulent Structure in Channel Flow by Dosing a Small Amount of Polymer Solution

2017 ◽  
Author(s):  
Yushi Okamura ◽  
Tomohiro Kurose ◽  
Yasuo Kawaguchi
Keyword(s):  
Velocity Distribution ◽  
Polymer Solution ◽  
Polymer Concentration ◽  
Water Soluble ◽  
Polymer Additives ◽  
Normal Velocity ◽  
Water Soluble Polymer ◽  
Low Speed ◽  
Wide Range ◽  
Near Wall

The phenomenon known as Toms effect can impart viscoelasticity to a water flow when a small amount of water-soluble polymer is added. The resulting viscoelastic fluid generates viscoelastic stress in the flow, dramatically reducing the turbulent stress. In this study, the spatial distribution of velocity is measured using a stereo-PIV method in the streamwise-spanwise plane parallel to the wall. Modification of the near wall turbulence by the polymer solution blown slowly from a permeable wall was investigated by analyzing the velocity distribution acquired by stereo-PIV measurements. Experimental results reveal that streamwise local mean velocity decreases as the dosed polymer concentration increases. The skewness factor at this height shifts from 0 to positive by adding the polymer, which indicates intensified turbulent coherent structure. Moreover, the spatial two-point correlation function calculated from streamwise velocity fluctuations maintains its high correlation with the streamwise direction. It is consistent with the finding from the instantaneous velocity distribution, which shows that the flection of low-speed streaks is suppressed. Next, it is revealed that the normal velocity at the wall for low-speed fluid is decreased dramatically by polymer additives. Moreover, applying the quadrant analysis, it is confirmed that ejection events are suppressed with decreasing normal velocity at the wall. Suppression of ejection motion affects to the turbulence in the log law layer. We conclude that this is one reason that turbulence is suppressed in a wide range of the shear layer by polymer additives present only in the vicinity of the wall.

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