Nonlinear dynamics of a shell encapsulated microbubble near solid boundary in an ultrasonic field

2020 ◽  
Vol 14 (3) ◽  
pp. 7235-7243
Author(s):  
N.M. Ali ◽  
F. Dzaharudin ◽  
E.A. Alias
Keyword(s):  
Oscillation Amplitude ◽  
Ultrasonic Field ◽  
Dynamical Behaviour ◽  
Ultrasound Contrast Agents ◽  
Chaotic Behaviour ◽  
Solid Boundary ◽  
Driving Frequency ◽  
Pressure Amplitude ◽  
Radial Expansion ◽  
Therapeutic Delivery

Microbubbles have the potential to be used for diagnostic imaging and therapeutic delivery. However, the transition from microbubbles currently being used as ultrasound contrast agents to achieve its’ potentials in the biomedical field requires more in depth understanding. Of particular importance is the influence of microbubble encapsulation of a microbubble near a vessel wall on the dynamical behaviour as it stabilizes the bubble. However, many bubble studies do not consider shell encapsulation in their studies. In this work, the dynamics of an encapsulated microbubble near a boundary was studied by numerically solving the governing equations for microbubble oscillation. In order to elucidate the effects of a boundary to the non-linear microbubble oscillation the separation distances between microbubble will be varied along with the acoustic driving. The complex nonlinear vibration response was studied in terms of bifurcation diagrams and the maximum radial expansion. It was found that the increase in distance between the boundary and the encapsulated bubble will increase the oscillation amplitude. When the value of pressure amplitude increased the single bubble is more likely to exhibit the chaotic behaviour and maximum radius also increase as the inter wall-bubble distance is gradually increased. While, with higher driving frequency the maximum radial expansion decreases and suppress the chaotic behaviour.

Periodic and chaotic behaviour in a reduction of the perturbed Korteweg-de Vries equation

1994 ◽  
Vol 445 (1923) ◽  
pp. 1-21 ◽  
Keyword(s):  
Lyapunov Exponent ◽  
Vries Equation ◽  
Period Doubling ◽  
Homoclinic Orbits ◽  
Dynamical Behaviour ◽  
Chaotic Behaviour ◽  
Subharmonic Bifurcations ◽  
Melnikov Functions ◽  
De Vries ◽  
Period Doubling Bifurcations

The dynamical behaviour of a reduction of the forced (and damped) Korteweg-de Vries equation is studied numerically. Chaos arising from subharmonic instability and homoclinic crossings are observed. Both period-doubling bifurcations and the Melnikov sequence of subharmonic bifurcations are found and lead to chaotic behaviour, here characterised by a positive Lyapunov exponent. Supporting theoretical analysis includes the construction of periodic solutions and homoclinic orbits, and their behaviour under perturbation using Melnikov functions.

A MECHANISM OF ULTRASONIC IRRADIATION TO ASSIST OR INHIBIT THE PARAMECIUM CELLS

2008 ◽  
Vol 20 (06) ◽  
pp. 353-363 ◽  
Author(s):  
Yi-Cheng Huang ◽  
Shiuh-Kuang Yang
Keyword(s):  
Cell Proliferation ◽  
Theoretical Model ◽  
Ultrasonic Irradiation ◽  
Shape Change ◽  
Power Level ◽  
Ultrasonic Field ◽  
Driving Frequency ◽  
Cell Organelles ◽  
Irradiation Intensity ◽  
Number Of Cells

This paper investigates the biological reactions of unicellular creature irradiated to a low intensity of ultrasonic field. The current study attempts to anticipate the value of the ultrasonic driving frequency which will induce the most significant biological reactions by using the theoretical model. The theoretical model of the cells in response to the ultrasonic irradiation is simulated using Rayleigh–Plesset's bubble activation theory. The simulation results indicate that the resonant frequency of the Paramecium vacuoles considered in the present study lies in the range 0.54–1.24 MHz. Ultrasonic irradiation experiments are performed at various power level intensities at driving frequencies corresponding to resonant (0.5 and 1 MHz) and nonresonant (0.25 and 5 MHz) frequencies. It is found that samples irradiated under different ultrasonic conditions exhibit clear differences in their cell proliferation tendencies. For example, in samples irradiated with lower power intensities and driving frequencies of 0.5 and 1 MHz, the number of cells in the treated samples is found to be approximately 30% higher than that in the original unexposed samples. However, when resonant frequencies and higher intensities are applied, the ultrasonic irradiation causes a shape change of the cell organelles and a corresponding reduction in the total number of cells in the treated sample. For the samples exposed to nonresonant frequency ultrasonic irradiation, it is found that the cell proliferation is limited and appears to vary independently of the applied irradiation intensity.

Bubble–bubble interaction effects on multiple bubbles dynamics in an ultrasonic cavitation field

2019 ◽  
Vol 234 (7) ◽  
pp. 1051-1060
Author(s):  
Feng Cheng ◽  
Weixi Ji ◽  
Junhua Zhao
Keyword(s):  
Cavitation Erosion ◽  
Threshold Value ◽  
Ultrasonic Field ◽  
Pressure Amplitude ◽  
Cavitation Field ◽  
Bubble Interaction ◽  
Erosion Test ◽  
Multiple Bubbles ◽  
Optimal Coupling ◽  
Material Fracture

A vibratory erosion test rig is used to study the cavitation erosion of 6061 alloy. Some craters and material fracture are found on the specimen surface at the beginning of test. A cavitation model in an ultrasonic field is developed by applying the bubble–bubble interaction effect into Keller–Miksis equation to obtain the bubbles dynamic characteristics. The results reveal that the bubble cloud configuration is suitable for the explanation of cavitation erosion, and the erosion surfaces of the specimen were subjected to the effect of both massive bubbles collapsing, occurring in the thin liquid layer between the horn and the specimen. It is concluded that the optimal coupling strength of bubbles increases with the decrease of the bubble initial radius, and stable cavitation only occurs when the acoustic pressure amplitude is higher than a threshold value, which can well predict the experimental results.

Study on the Topology Structure and Evolvement Analysis of Nonlinear Model under Superharmonic Resonance

2011 ◽  
Vol 58-60 ◽  
pp. 73-78
Author(s):  
Jun Hai Ma ◽  
Qi Zhang
Keyword(s):  
Approximate Solution ◽  
Nonlinear Model ◽  
Oscillation Amplitude ◽  
Driving Frequency ◽  
System Quality ◽  
System Complexity ◽  
First Order ◽  
Complex Systems Theory ◽  
Inherent Frequency ◽  
Research Findings

Based on the work of domestic and foreign scholars and the application of complex systems theory, we study the first-order approximate solution of a category nonlinear model, and the intrinsic complex relationship among oscillation amplitude, phase, the system inherent damping parameters, driven amplitudeand driving frequency of approximate solution under the circumstances of system quality resonance that incentive frequency of nonlinear model which is far away from system inherent frequency when . We also study the evolution process of system complexity with different combination of factors , and have got some useful research findings.

Optical and acoustic investigations of the dynamics of laser-produced cavitation bubbles near a solid boundary

1989 ◽  
Vol 206 ◽  
pp. 299-338 ◽  
Author(s):  
A. Vogel ◽  
W. Lauterborn ◽  
R. Timm
Keyword(s):  
Fluid Velocity ◽  
Bubble Radius ◽  
Bubble Collapse ◽  
Ring Vortex ◽  
Solid Boundary ◽  
High Speed Photography ◽  
Pressure Amplitude ◽  
Spherical Bubble ◽  
Cavitation Bubbles ◽  
Acoustic Transients

The dynamics of laser-produced cavitation bubbles near a solid boundary and its dependence on the distance between bubble and wall are investigated experimentally. It is shown by means of high-speed photography with up to 1 million frames/s that jet and counterjet formation and the development of a ring vortex resulting from the jet flow are general features of the bubble dynamics near solid boundaries. The fluid velocity field in the vicinity of the cavitation bubble is determined with time-resolved particle image velocimetry. A comparison of path lines deduced from successive measurements shows good agreement with the results of numerical calculations by Kucera & Blake (1988). The pressure amplitude, the profile and the energy of the acoustic transients emitted during spherical bubble collapse and the collapse near a rigid boundary are measured with a hydrophone and an optical detection technique. Sound emission is the main damping mechanism in spherical bubble collapse, whereas it plays a minor part in the damping of aspherical collapse. The duration of the acoustic transients is 20-30 ns. The highest pressure amplitudes at the solid boundary have been found for bubbles attached to the boundary. The pressure inside the bubble and at the boundary reaches about 2.5 kbar when the maximum bubble radius is 3.5 mm. The results are discussed with respect to the mechanism of cavitation erosion.

scholarly journals Influence of the pressure-dependent resonance frequency on the bifurcation structure and backscattered pressure of ultrasound contrast agents: A numerical investigation

2021 ◽  
Author(s):  
Amin Jafari Sojahrood ◽  
Omar Falou ◽  
Robert Earl ◽  
Raffi Karshafian ◽  
Michael C. Kolios
Keyword(s):  
Contrast Agents ◽  
Cross Section ◽  
Expansion Ratio ◽  
Ultrasound Contrast Agents ◽  
Driving Pressure ◽  
Radial Expansion ◽  
Bifurcation Structure ◽  
Saddle Node Bifurcation ◽  
Ultrasound Contrast ◽  
Ultrasound Applications

The bifurcation structure of the oscillations of ultrasound contrast agents (UCAs) was studied as a function of the driving pressure for excitation frequencies that were determined using the UCAs pressure-dependent resonances (fs)(fs). It was shown that when excited by the (fs)(fs), the UCA can undergo a saddle-node bifurcation (SNB) to higher amplitude oscillations. The driving pressure at which the SNB occurs is controllable and depends on the (fs)(fs) magnitude. Utilizing the appropriate (fs)(fs), the scattering cross section of the UCAs can significantly be enhanced (e.g., ∼∼ninefold) while at the same time avoiding potential UCA destruction (by limiting the radial expansion ratio <<2). This offers significant advantages for optimizing UCA-mediated imaging and therapeutic ultrasound applications.

scholarly journals An Indispensable tool for ultrasound based diagnostics and therapies - Microbubbles

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Alec Nelson Thomas ◽  
Eleanor Stride
Keyword(s):  
Clinical Trial ◽  
Biological Effects ◽  
Region Of Interest ◽  
Ultrasonic Field ◽  
Ultrasound Contrast Agents ◽  
Tissue Response ◽  
Acoustic Energy ◽  
Hydrophilic Drugs ◽  
Drug Molecules ◽  
Therapeutic Platform

Microbubbles (MBs) are micrometre sized gas spheres comprising a biocompatible shell that provide vascular contrast for diagnostic ultrasound (US) imaging. MBs volumetrically oscillate in an ultrasonic field and scatter acoustic energy over a range of frequencies that can be separated from the tissue response. MBs can also provide organ perfusion rates by imaging their “wash-in” to a region of interest which can be correlated to vascular flow. When driven at higher acoustic pressures, localized biological effects can be induced, including increased tissue permeabilization, thermal effects and localised release of drugs that can be encapsulated in the MBs themselves. Both hydrophobic and hydrophilic drugs can be loaded on to MBs e.g. through the use of liposomal carriers or direct attachment of drug molecules to the bubble shell. Since the early 2000s, MB-based technologies have been well researched, though there was significant regulatory push back starting in 2006 based on a controversial clinical trial. From that point, both physicians and researchers have consistently demonstrated the robust safety of MBs as ultrasound contrast agents and their significant clinical utility. Within the last 5 years, more indications have been approved. A recent first-in-man clinical trial of therapeutic US with MBs reversibly opening the blood brain barrier has also been shown to be safe in amyotrophic lateral sclerosis patients. The following article outlines the coupling of US and MBs as a diagnostic and therapeutic platform with a particular focus on their application to the therapy of surgical diseases.

Mechanism of Circumferential Static Pressure Oscillation in a Centrifugal Compressor With Volute

2021 ◽  
Author(s):  
Ce Yang ◽  
Botai Su ◽  
Xin Shi ◽  
Hanzhi Zhang ◽  
Wenli Wang ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Pressure Gradient ◽  
Mass Flow ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Oscillation Amplitude ◽  
Circumferential Direction ◽  
Pressure Amplitude ◽  
High Static Pressure ◽  
Circumferential Pressure

Abstract Under the action of an asymmetric volute structure, a non-uniform flow field is formed in the circumferential direction of the centrifugal compressor. During the throttling process of the compressor at different rotational speeds, the static pressure presents a double-peak distribution of two high static pressure strips, one of which is induced by the volute tongue. However, the formation mechanism of the other high static pressure strip remains unclear. In this regard, computations of the steady and unsteady flows in a centrifugal compressor with and without a volute are performed. The purpose of removing the volute is to simplify the boundary conditions at the diffuser exit, eliminate the circumferential pressure gradient distribution in the volute, and retain the circumferential local high static pressure region induced by the VT; thereafter, the circumferential static pressure distributions in the diffuser and impeller are observed. The results indicate that after eliminating the pressure gradient at the diffuser exit along the rotation direction, only local high static pressure boundary conditions can result in the formation of two high static pressure strips in the diffuser and impeller. The local high static pressure at the exit redistributes the mass flow rate at the impeller outlet, forming two regions with high airflow velocity in the diffuser; this leads to the appearance of two high static pressure strips in the circumferential direction. With the increase in the pressure amplitude of the high static pressure at the diffuser exit, the oscillation amplitude of the circumferential pressure is intensified, and the pressure peaks of the two high static pressure strips increase. However, the circumferential positions of the two static pressure peaks practically remain constant. At large mass flow rates, the pressure reduction along the circumferential direction at the diffuser exit preclude the formation of two circumferential high static pressure strips in the diffuser and impeller.

Sign in / Sign up

Export Citation Format

Share Document