On the Dynamics of a Cavitating Pump

This paper presents a review of some of the recent developments in our understanding of the dynamics and instabilities caused by cavitation in pumps. Focus is placed on presently available data for the transfer functions for cavitating pumps and inducers, particularly on the compliance and mass flow gain factor which are so critical for pump and system stability. The resonant frequency for cavitating pumps is introduced and contexted. Finally emphasis is placed on the paucity of our understanding of pump dynamics when the device or system is subjected to global oscillation

Fundamentals of Multiphase Flow

The subject of multiphase flows encompasses a vast field, a host of different technological contexts, a wide spectrum of different scales, a broad range of engineering disciplines and a multitude of different analytical approaches. Not surprisingly, the number of books dealing with the subject is voluminous. For the student or researcher in the field of multiphase flow this broad spectrum presents a problem for the experimental or analytical methodologies that might be appropriate for his/her interests can be widely scattered and difficult to find. The aim of the present text is to try to bring much of this fundamental understanding together into one book and to present a unifying approach to the fundamental ideas of multiphase flows. Consequently the book summarizes those fundamental concepts with relevance to a broad spectrum of multiphase flows. It does not pretend to present a comprehensive review of the details of any one multiphase flow or technological context though reference to books providing such reviews is included where appropriate. This book is targeted at graduate students and researchers at the cutting edge of investigations into the fundamental nature of multiphase flows; it is intended as a reference book for the basic methods used in the treatment of multiphase flows

Hydrodynamics of Pumps

The subject of this monograph is the fluid dynamics of liquid turbomachines, particularly pumps. Rather than attempt a general treatise on turbomachines, we shall focus attention on those special problems and design issues associated with the flow of liquid through a rotating machine. There are two characteristics of a liquid that lead to these special problems, and cause a significantly different set of concerns than would occur in, say, a gas turbine. These are the potential for cavitation and the high density of liquids that enhances the possibility of damaging unsteady flows and forces

The wave-induced solute flux from submerged sediment

The issue of the transport of dissolved nutrients and contaminants between the sediment in the bottom of a lake or reservoir and the body of water above it is an important one for many reasons. In particular the biological and chemical condition of the body of water is intricately linked to these mass transport processes. As the review by Boudreau (Rev Geophys 38(3):389–416, 2000) clearly demonstrates those transport processes are very complex involving mechanisms as diverse as the wave-induced flux between the sediment and the overlying water and the effect of burrowing animals on the transport within the sediment as well as basic diffusion mechanisms. The present paper focuses on one facet of these transport processes; we re-examine the balance of diffusion and wave-induced advection and demonstrate that the wave-induced flux of a solute from submerged sediment is not necessarily purely diffusive as suggested by Harrison et al. (J Geophys Res 88:7617–7622, 1983) but can be dominated by a mean or time-averaged flux induced by the advective fluid motion into and out of the sediment caused by the fluctuating pressure waves associated with wave motion. Indeed along the subtidal shoreline where the fluctuating bottom pressures are greatest, wave-induced advection will dominate the mean, time-averaged transport of solute into or out of the sediment as suggested in the work of Riedl et al. (Mar Biol 13:210–221, 1972). However, the present calculations also indicate that this advective flux decreases rapidly with increasing depth so that further away from the shoreline the advective flux becomes negligible relative to the diffusive flux and therefore the latter dominates in deeper water

Adventure hikes and canyoneering in the San Gabriels

Each of the webpages in this collection describes a different adventure hike. In each case, I have tried to give as much useful information as possible without spoiling the sense of adventure. When I explored each of these for the first time I had little or no knowledge of what to expect. In the early days, this led to some unexpected adventures such as spending an unplanned night in the canyon of the East Fork of the San Gabriel River. Later, I became more circumspect and often conducted preliminary exploratory hikes before attempting the complete version described here. Thus, for example, I ventured into some of the canyons from both above and below before attempting to travel all the way through. In each case, I have provided a map on which I have marked prominent features, obstacles or navigational aids. In addition, I have included some photographs so that the reader can gauge his or her own willingness to tackle some of the challenges described herein. Estimates of the times required for the hikes are also provided though the actual time required will vary considerably depending on the weather, stream conditions and personal agility and fitness. Some readers may be able to go significantly faster than indicated here. Groups larger than three or four will most likely be slower especially when rappelling. An estimate of the distance covered is also provided though this is much less useful than the elapsed time when discussing adventure hikes since average speeds vary greatly with the terrain. Another guide to the difficulty is the listed elevation gain that, unless otherwise specified, is the sum of all the major ascents experienced on the hike. Specific difficulties (and the equipment needed to overcome them) are also listed for reference at the beginning of each description

On the Dynamics of Cavitating Pumps

This paper presents a review of some of the recent developments in our understanding of the dynamics and instabilities caused by cavitation in pumps. Focus is placed on presently available data for the transfer functions for cavitating pumps and inducers, particularly on the compliance and mass flow gain factor that are critical for pump and system stability. The resonant frequency for cavitating pumps is introduced and contexted. Finally emphasis is placed on the paucity of our understanding of pump dynamics when the device or system is subjected to global oscillation

The far side of the sky

PREFACE: In this collection of stories, I have recorded some of my adventures on the mountains of the world. I make no pretense to being anything other than an average hiker for, as the first stories tell, I came to enjoy the mountains quite late in life. But, like thousands before me, I was drawn increasingly toward the wilderness, partly because of the physical challenge at a time when all I had left was a native courage (some might say foolhardiness), and partly because of a desire to find the limits of my own frailty. As these stories tell, I think I found several such limits; there are some I am proud of and some I am not. Of course, there was also the grandeur and magnificience of the mountains. There is nothing quite to compare with the feeling that envelopes you when, after toiling for many hours looking at rock and dirt a few feet away, the world suddenly opens up and one can see for hundreds of miles in all directions. If I were a religious man, I would feel spirits in the wind, the waterfalls, the trees and the rock. Many of these adventures would not have been possible without the marvellous companionship that I enjoyed along the way. Doug Hart was a frequent companion during the early adventures and I shall always count myself exceedingly fortunate to have travelled with him. Our spirits are forever bound together by the trials we faced together especially on the Mountain of the Devil. There were other companions too. Terry Jones was a most gracious host both in Oxford and on the slopes of Snowdon. In Japan, Yoichiro Matsumoto and Yoshi Tsujimoto were great companions. In Korea, I was touched by the watchful eye which Seung-Joon Lee kept on my wanderings. And closer to home in California, my advancing years were graced by the company of a number of young fellow adventurers, among them Troy Sette who was born with the instinct for adventure, Clancy Rowley whose grace and kindness shone in all he did and Mark Duttweiler with whom hiking was always a pleasure. To Garrett Reisman who taught me to climb, I owe an enduring debt and the very best of good fortune in his adventures as a NASA astronaut. In later years, I was immensely fortunate to link up with the three more great companions, the Marquesa de Canyonette, Randi Poer, whose blithe spirit is reflected in several of these stories, Scott ``Seldom Seen'' Smith whose kindness is unsurpassed, and the ``Magnificient Marine'' John Perry, a man for all seasons. I shall treasure all of their friendships for the rest of my days. To them and to all the others, I am deeply grateful. Most especially to Doreen whose love and friendship traveled with me to every corner of the globe

Adventure hikes and canyoneering in the Southwest

Each of the webpages in this collection describes a different adventure hike. I have tried to give as much useful information as possible without spoiling the sense of adventure. In each case, I have provided a map on which prominent features, obstacles or navigational aids have been marked. In addition, I have included some photographs so that the reader can gauge his or her own willingness to tackle some of the challenges described herein. Estimates of the times required for the hikes are also provided though the actual time required will vary considerably depending on the weather, stream conditions and personal agility and fitness. Some readers may be able to go significantly faster than indicated here. Groups larger than three or four will most likely be slower especially when rappelling. An estimate of the distance covered is also provided though this is much less useful than the elapsed time when discussing adventure hikes since average speeds vary greatly with the terrain. Another guide to the difficulty is the listed elevation gain that, unless otherwise specified, is the sum of all the major ascents experienced on the hike. Specific difficulties (and the equipment needed to overcome them) are also listed for reference at the beginning of each description

Solving the mystery of booming sand dunes

Desert booming can be heard after a natural slumping event or during a sand avalanche generated by humans sliding down the slip face of a large dune. The sound is remarkable because it is composed of one dominant audible frequency (70 to 105 Hz) plus several higher harmonics. This study challenges earlier reports that the dunes’ frequency is a function of average grain size by demonstrating through extensive field measurements that the booming frequency results from a natural waveguide associated with the dune. The booming frequency is fixed by the depth of the surficial layer of dry loose sand that is sandwiched between two regions of higher compressional body wave velocity. This letter presents measurements of the booming frequencies, compressional wave velocities, depth of surficial layer, along with an analytical prediction of the frequency based on constructive interference of propagating waves generated by avalanching along the dune surface