scholarly journals The influence of joint geometry of toneholes with the main bore of wind musical instruments on their frequency characteristics

2021 ◽  
Vol 2090 (1) ◽  
pp. 012154
Author(s):  
R A Gerasimov
Keyword(s):  
Musical Instruments ◽  
Frequency Characteristics ◽  
Viscous Drag ◽  
Comsol Multiphysics ◽  
Radius Of Curvature ◽  
Empirical Dependence ◽  
Thermal Exchange ◽  
Resonance Frequencies ◽  
Sharp Edges ◽  
Air Column

Abstract The article discusses the influence of geometric parameters (the presence and magnitude of the radius of curvature) at the junction of the toneholes with the main bore of the air column on the frequency characteristics of woodwind musical instruments. A theoretical calculation of the eigenfrequencies of an air column with one tonehole in the case of sharp edges has been carried out. The resonance frequencies were also found using computer simulation in the COMSOL Multiphysics 5.5 program for the case of sharp edges and joints with a radius of curvature. An empirical dependence of the frequency of the main tone of the air column on the radius of curvature of the edges of the tonehole is obtained. All simulation were carried out for two models: excluding and including viscous drag and thermal exchange losses.

scholarly journals Development of Electrohydraulic Forming Process for Aluminum Sheet with Sharp Edge

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ji-Yeon Shim ◽  
Bong-Yong Kang
Keyword(s):  
High Velocity ◽  
Forming Limit Diagram ◽  
Sharp Edge ◽  
Dome Height ◽  
Forming Limit ◽  
Radius Of Curvature ◽  
Forming Process ◽  
Electrohydraulic Forming ◽  
Forming Technology ◽  
Sharp Edges

Electrohydraulic forming (EHF), high-velocity forming technology, can improve the formability of a workpiece. Accordingly, this process can help engineers create products with sharper edges, allowing a product’s radius of curvature to be less than 2 mm radius of curvature. As a forming process with a high-strain rate, the EHF process produces a shockwave and pressure during the discharge of an electrical spark between electrodes, leading to high-velocity impact between the workpiece and die. Therefore, the objective of this research is to develop an EHF process for forming a lightweight materials case with sharp edges. In order to do so, we employed A5052-H32, which has been widely used in the electric appliance industry. After drawing an A5052-H32 Forming Limit Diagram (FLD) via a standard limiting dome height (LDH) test, improvements to the formability via the EHF process were evaluated by comparing the strain between the LDH test and the EHF process. From results of the combined formability, it is confirmed that the formability was improved nearly twofold, and a sharp edge with less than 2 mm radius of curvature was created using the EHF process.

scholarly journals Optimizing the Design of Surface-Acoustic-Wave Ring Resonator by Changing the Interdigitated Transducer Topology

2021 ◽  
Vol 24 (6) ◽  
pp. 51-62
Author(s):  
S. Yu. Shevchenko ◽  
D. A. Mikhailenko ◽  
B. Nyamweru
Keyword(s):  
Acoustic Wave ◽  
Signal Detection ◽  
Surface Acoustic Wave ◽  
Acoustic Waves ◽  
Sensitive Element ◽  
Ring Resonator ◽  
Surface Acoustic Waves ◽  
Frequency Characteristics ◽  
Optimal Topology ◽  
Comsol Multiphysics

Introduction. Previous works considered the frequency characteristics and methods for fixing sensitive elements in the form of a wave ring resonator on surface acoustic waves in a housing made of various materials, as well as the influence of external factors on sensitive elements. It was found that the passband in such a case is sufficiently wide, which can affect adversely signal detection when measuring acceleration using the sensitive element under development. Therefore, it has become relevant to reduce the sensitive element’s bandwidth by changing the design of the interdigitated transducer (IDT).Aim. To demonstrate an optimal topology for an IDT with a low bandwidth, leading to improved signal detection when acceleration affects the sensitive element.Materials and methods. The finite element method and mathematical processing in AutoCAD and in COMSOL Multiphysics.Results. Nine topologies of IDT are proposed. All these types were investigated using the COMSOL Multiphysics software on lithium niobate substrates, which material acts as a sensitive element. The frequency characteristics are presented. The data obtained allowed an optimal design of the ring resonator to be proposed: an IDT with rectangular pins without selective withdrawal.Conclusion. Self-generation in a ring resonator can be performed by withdrawing no more than one pair of IDTs for 10 or more periods. In this case, the withdrawal of IDTs should be uniform. With an increase in the number of IDT withdrawals, the geometry of the ring resonator is violated, and the wave leaves the structure. The presence of a shared bus keeps the surface acoustic wave inside the IDT structure, and the narrowing of the periods towards the inner part of the structure makes it possible to improve the frequency characteristics of the ring resonator on surface acoustic waves.

The motion of a prolate ellipsoid in a rotating Stokes flow

2007 ◽  
Vol 583 ◽  
pp. 123-132 ◽  
Author(s):  
J. R. T. SEDDON ◽  
T. MULLIN
Keyword(s):  
Stokes Flow ◽  
Flow Model ◽  
Vertical Wall ◽  
Viscous Drag ◽  
Experimental Investigations ◽  
Radius Of Curvature ◽  
Fixed Position ◽  
Close Proximity ◽  
Limiting Case ◽  
Cylinder Rotation

Results are presented from experimental investigations into the motion of a heavy ellipsoid in a horizontal rotating cylinder, which has been completely filled with highly viscous fluid. The motion can be conveniently classified using the ratio between the maximum radius of curvature of the ellipsoid κmax and the radius of the drum Rd. If κmax < Rd the ellipsoid adopts a fixed position adjacent to the rising wall for a given cylinder rotation rate. The dependence of this position on wall speed is, surprisingly, independent of the ellipsoid's length, and a Stokes flow model has been developed which predicts both this independence and the speed for the limiting case of an ellipsoid adjacent to a vertical wall. If κ max < Rd the ellipsoid must tilt in order to maintain the maximum surface area in close proximity to the wall. Once tilted, a component of the viscous drag acts to laterally translate the ellipsoid from end to end of the drum. The ellipsoid with κmax = Rd adopts a series of fixed positions for most drum rotational rates but, between two regions of fixed-point behaviour, it undergoes a transition to oscillatory motion.

Edge Fillet Radius Effect on Acoustic Energy in an Ultrasonic Microcontainer for Preparing Nanoemulsion

2019 ◽  
Vol 105 (6) ◽  
pp. 1243-1250
Author(s):  
S. M. M. Modarres-Gheisari ◽  
M. Mohammadpour ◽  
R. Gavagsaz-Ghoachani ◽  
P. Safarpour ◽  
M. Zandi
Keyword(s):  
Chemical Engineering ◽  
Experimental Tests ◽  
Positive Influence ◽  
Acoustic Energy ◽  
Comsol Multiphysics ◽  
Ultrasonic Bath ◽  
Fillet Radius ◽  
Propagating Waves ◽  
Sharp Edges ◽  
Acoustic Energy Density

Nanoemulsion preparation and improvement play a pivotal role in the area of pharmaceuticals, food, mechanical, and chemical engineering. The ultrasonic technique is one of the most commonly used methods in preparing nanoemulsion, related to mechanical and electrical engineering. The present study aimed to evaluate the effect of edge fillet radius in four different layouts of a cubic ultrasonic microcontainer at different frequencies through 36 simulations by using COMSOL Multiphysics software. To this aim, the simulations were performed in three edge fillet radius values of zero, 2.5 and 5 mm, and at the excitation frequencies of 20, 200 and 300 kHz. In this regard, experimental tests were carried out in two modes of: a) regular ultrasonic bath (RUB) and b) filleted-edges ultrasonic bath (FEUB). Based on the simulation and experimental results, the removal of sharp edges has a positive influence on propagating waves, leading to an increase in the acoustic energy density at different frequencies and the effect was more significant at lower frequencies and layouts with more PZTs.

Edge Effect on Viscous Drag of the Rotor in Liquid Floating Rotational Micro-Gyroscope

2013 ◽  
Vol 562-565 ◽  
pp. 286-291
Author(s):  
Hai Feng Zhang ◽  
Xiao Shu Zhang ◽  
Xiao Wei Liu ◽  
Yin Chun Liang ◽  
Rui Weng
Keyword(s):  
Edge Effect ◽  
Sharp Edge ◽  
Viscous Drag ◽  
Curvature Radius ◽  
Edge Structure ◽  
Liquid Suspension ◽  
Simulation And Experiment ◽  
Speed Up ◽  
Sharp Edges ◽  
Maximal Reduction

A liquid floating rotational micro-gyroscope is proposed in this paper, whose stability is improved by liquid suspension. High rotor velocity is needed to improve its sensitivity. Edge effect is the phenomenon that sharp edges cause much more viscous drag. This work researches edge effect's influence on viscous drag to speed up the rotor. Flow field models of the sharp edge structure and fillet structure are established separately. Viscous drag is measured by simulation and experiment. Edge effect causes a lot of viscous drag and it can be reduced significantly by filleting the rotor. The maximal reduction is one third relative to the sharp edge structure, and it is reached when fillet curvature radius is half of rotor thickness.

Development of π–Shape Parametric Resonators Including Torsional Self Pumping Springs

2010 ◽  
Author(s):  
Jin-Ha Kim ◽  
Seung Hoon Lee ◽  
Joung A. Lee ◽  
Seung-Bo Shim ◽  
Kwang-Cheol Lee ◽  
...  
Keyword(s):  
Signal Amplitude ◽  
Machining Process ◽  
Comsol Multiphysics ◽  
Small Scale ◽  
Analytical Prediction ◽  
General Science ◽  
Pure Torsion ◽  
Frequency Matching ◽  
Resonance Frequencies ◽  
Simulation Results

Materializing NEMS devices incorporating nonlinear dynamics is of fundamental importance in the field of small-scale mechanics and general science. Among these, parametric amplification draws considerable attention due to its unique characteristic. In this paper, we introduce novel designs for mechanically pumped parametric resonators in which torsional pumping springs are linked. The proposed parametric resonators can increase signal amplitude by matching resonances in a cantilever and beam. Amplitudes of resonators increase when resonances of cantilevers are amplified by torsional pumping from linked beams. In an attempt to transmit pure torsion (not displacement), zero-displacement points method is suggested, and the analytical prediction results are further verified by the corresponding simulation results obtained from COMSOL Multiphysics®. The π-shape resonators are fabricated by surface nano-machining process, and the horizontal dimensions of fabricated beams and cantilever are 31.6 um and 8 um, respectively. By using magnetomotive method, resonance frequencies are measured. Finally frequency matching is performed by DC tuning. When 54 V is applied, fdrive and fpump increase 0.78% and 0.16%, and the frequencies are exactly matched as 4.463 MHz.

Field ion microscopy

1988 ◽  
Vol 46 ◽  
pp. 434-435
Author(s):  
Gert Ehrlich
Keyword(s):  
Low Temperature ◽  
Sample Surface ◽  
Low Pressure ◽  
Radius Of Curvature ◽  
Field Ion Microscopy ◽  
Phosphor Screen ◽  
Ion Microscopy ◽  
Field Ion Microscope

The field ion microscope, devised by Erwin Muller in the 1950's, was the first instrument to depict the structure of surfaces in atomic detail. An FIM image of a (111) plane of tungsten (Fig.l) is typical of what can be done by this microscope: for this small plane, every atom, at a separation of 4.48Å from its neighbors in the plane, is revealed. The image of the plane is highly enlarged, as it is projected on a phosphor screen with a radius of curvature more than a million times that of the sample. Müller achieved the resolution necessary to reveal individual atoms by imaging with ions, accommodated to the object at a low temperature. The ions are created at the sample surface by ionization of an inert image gas (usually helium), present at a low pressure (< 1 mTorr). at fields on the order of 4V/Å.

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

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