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Über dieses Buch

Non-Newtonian properties on bubble dynamics and cavitation are fundamentally different from those of Newtonian fluids. The most significant effect arises from the dramatic increase in viscosity of polymer solutions in an extensional flow, such as that generated about a spherical bubble during its growth or collapse phase. In addition, many biological fluids, such as blood, synovial fluid, and saliva, have non-Newtonian properties and can display significant viscoelastic behaviour. This monograph elucidates general aspects of bubble dynamics and cavitation in non-Newtonian fluids and applies them to the fields of biomedicine and bioengineering. In addition it presents many examples from the process industries. The field is strongly interdisciplinary and the numerous disciplines involve have and will continue to overlook and reinvent each others’ work. This book helps researchers to think intuitively about the diverse physics of these systems, to attempt to bridge the various communities involved, and to convey the interest, elegance, and variety of physical phenomena that manifest themselves on the micrometer and microsecond scales.



Chapter 1. Non-Newtonian Fluids

A fluid can be defined as a material that deforms continually under the application of an external force. In other words, a fluid can flow and has no rigid three-dimensional structure. An ideal fluid may be defined as one in which there is no friction.
Emil-Alexandru Brujan

Chapter 2. Nucleation

Cavitation is critically dependent on the existence of nucleation sites. Cavitation starts when these nuclei enter a low-pressure region where the equilibrium between the various forces acting on the nuclei surface cannot be established. As a result, bubbles appear at discrete spots in low-pressure regions, grow quickly to relatively large size, and suddenly implode as they are swept into regions of higher pressure. In most conventional engineering contexts, the prediction and control of nucleation sites is very uncertain even when dealing with a simple liquid like water. Here we present data on the nuclei distribution in more complex fluids, such as polymer aqueous solutions and blood.
Emil-Alexandru Brujan

Chapter 3. Bubble Dynamics

The main goal of the investigations on bubble dynamics is to describe the velocity field and the pressure distribution in the liquid surrounding the bubble. In this section we describe the effect of the viscoelastic properties of the liquid on the behaviour of cavitation bubbles situated in a liquid of infinite extent or near a rigid boundary.
Emil-Alexandru Brujan

Chapter 4. Hydrodynamic Cavitation

Hydrodynamic cavitation is observed when large pressure differentials are generated within a moving liquid and is accompanied by a number of physical effects, erosion being most notable from a technological viewpoint. Cavitation bubbles can form in the low pressure region and be carried into the higher pressure region where they collapse, so that the surface of any body is acted on by pulsating pressure loads, eventually leading to the destruction of the surface. The collapse of the bubbles goes hand in hand with a cracking noise, giving the first indication of cavitation occurrence.
Emil-Alexandru Brujan

Chapter 5. Cavitation Erosion

Cavitational activity in close proximity to solid boundaries is known to lead to material damage and erosion. Such damage occurs, for example, at marine propellers, turbine blades, or in pumps, but it is also deemed to be involved in ultrasonic cleaning, in the wear of knee joints, and in a variety of cardiovascular applications of lasers and ultrasound. The evidence that most directly links surface damage to cavitation has come from experiments with hydrofoils in cavitation tunnels, which show that the maximum erosion along a hydrofoil surface correlates with the location of collapsing cavitation bubbles (Knapp et al. 1970). Various techniques have been used to investigate the cavitation erosion of solid surfaces.
Emil-Alexandru Brujan

Chapter 6. Cardiovascular Cavitation

Cavitation has been shown to play a key role in a wide array of novel therapeutic applications of ultrasound and lasers. Sometimes the mechanical effects associated with cavitation contribute to the intented surgical effect. More often, however, they are the source of unwanted collateral effects limiting the local confinement of ultrasound and laser surgery.
Emil-Alexandru Brujan

Chapter 7. Nanocavitation for Cell Surgery

In the previous chapters we discussed the dynamic behaviour of cavitation bubbles with micrometer-order sizes. These bubbles are generated during picosecond or nanosecond laser surgery as well as in the diagnostic and therapeutic applications of ultrasound in the cardiovascular system or in the hydrodynamic cavitation.
Emil-Alexandru Brujan

Chapter 8. Cavitation in Other Non-Newtonian Biological Fluids

In the previous chapters we have described the effects of cavitation in the cardiovascular system and cell surgery. There are an increasing number of biomedical contexts where cavitation takes place in other non-Newtonian biological fluids, such as saliva or synovial fluid. In saliva, cavitation occurs during some medical applications of lasers and ultrasound.
Emil-Alexandru Brujan


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