No abstract

There is an increasing interest by doctors and patients in extracorporeal shock wave therapy (ESWT) for chronic plantar fasciopathy (PF), particularly in second generation radial extracorporeal shock wave therapy (RSWT). The present review aims at serving this interest by providing a comprehensive overview on physical and medical definitions of shock waves and a detailed assessment of the quality and significance of the randomized clinical trials published on ESWT and RSWT as it is used to treat chronic PF. Both ESWT and RSWT are safe, effective, and technically easy treatments for chronic PF. The main advantages of RSWT over ESWT are the lack of need for any anesthesia during the treatment and the demonstrated long-term treatment success (demonstrated at both 6 and 12 months after the first treatment using RSWT, compared to follow-up intervals of no more than 12 weeks after the first treatment using ESWT). In recent years, a greater understanding of the clinical outcomes in ESWT and RSWT for chronic PF has arisen in relationship not only in the design of studies, but also in procedure, energy level, and shock wave propagation. Either procedure should be considered for patients 18 years of age or older with chronic PF prior to surgical intervention.

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Measuring the void fraction distribution is still one of the greatest challenges in cavitation research. In this paper, a measurement technique for the quantitative void fraction characterization in a cavitating pipe flow is presented. While it is almost impossible to visualize the inside of the cavitation region with visible light, it is shown that with x-ray computed tomography (CT) it is possible to capture the time-averaged void fraction distribution in a quasi-steady pipe flow. Different types of cavitation have been investigated including cloud-like cavitation, bubble cavitation and film cavitation at very high flow rates. A specially designed nozzle was employed to induce very stable quasi-steady cavitation. The obtained results demonstrate the advantages of the measurement technique compared to other ones; for example, structures were observed inside the cavitation region that could not be visualized by photographic images. Furthermore, photographic images and pressure measurements were used to allow comparisons to be made and to prove the superiority of the CT measurement technique.

A nozzle expansion into a vacuum chamber was used to investigate the evaporation of highly superheated liquid jets. The large molar specific heat of fluids with high molecular complexity — in this case C6F14 — is responsible for the new phenomena reported here. A model was developed to describe the basic physical effects. A cubic equation of state was used to describe the thermodynamic properties of the fluid. The evaporation was modelled as a sonic deflagration followed by an axisymmetric supersonic expansion. As in the case of hypersonic gas jets the final state is reached by a normal shock. For sufficiently high temperatures and expansion ratios a complete adiabatic evaporation of the liquid was found. At even higher temperatures the liquid evaporates completely within a rarefaction discontinuity. The predictions of the model are in good agreement with the experimental results.