An Evaluation of Computational Fluid Dynamics for Spillway Modelling

Computational Fluid Dynamics (CFD) is used extensively by engineers to model and analyse complex issues related hydraulic design, planning studies for future generating stations, civil maintenance, supply efficiency, and dam safety. The integrity of computed values from CFD models is of considerable economic importance in the design, upgrading and maintenance of hydroelectric generating stations. CFD models have the ability to predict many characteristics flow over a spillway and Manitoba Hydro has had good agreement with physical model results in the past. However, date there has not been a review that brings all the available information together for a comprehensive assessment. The objective of this research is to build upon previous investigations on the use of CFD modelling, by focusing specifically on the ability to accurately model spillways using CFD. This paper discusses three-dimensional numerical modelling of several different spillway configurations using the CFD software Flow-3D and compares the predicted rating curves, pressures, and water surface elevations to corresponding physical model experimental values. The numerical model results were generally in agreement with physical model data, however, the relative differences in discharges were found to have a P/Hd dependency. The accuracy for a given model resolution and associated computational time required was also considered

Affective gaming using adaptive speed controlled by biofeedback

This work is part of a larger project exploring how affective computing can support the design of player-adaptive video games. We investigate how controlling some of the game mechanics using biofeedback affects physiological reactions, performance, and the experience of the player. More specifically, we assess how different game speeds affect player physiological responses and game performance. We developed a game prototype with Unity1 which includes a biofeedback loop system based on the level of physiological activation through skin resistance (SKR) measured with a smart wristband. In two conditions, the player moving speed was driven by SKR, to increase (respectively decrease) speed when the player is less activated (SKR decreases). A control condition was also used where player speed is not affected by SKR. We collected and synchronized biosignals (heart rate [HR], skin temperature [SKT] and SKR), and game information, such as the total time to complete a level, the number of ennemy collisions, and their timestamps. Additionally, emotional profiling (TIPI, I-Panas-SF), measured using a Likert scale in a post-task questionnaire, and semi-open questions about the game experience were used. The results show that SKR was significantly higher in the speed down condition, and game performance improved in the speed up condition. Study collected data involved 13 participants (10 males, 3 females) aged from 18 to 50 (M = 24.30, SD = 9.00). Most of the participants felt engaged with the game (M = 6.46, SD = 0.96) and their level of immersion was not affected by wearing the prototype smartband. Thematic analysis (TA) revealed that the game speed impacted the participants stress levels such as high speed was more stressful than hypothesized; many participants described game level-specific effects in which they felt that their speed of movement reflected their level of stress or relaxation. Slowing down the participants indeed increased the participant stress levels, but counter intuitively, more stress was detected in high speed situations

The Effects of Entrepreneurial Orientation and Commitment to Objectives on Performance

The relationship between entrepreneurial orientation (EO) and performance is often moderated by different factors. Specifically, scholars have called for research examining whether commitment to long-term objectives improves EO’s effectiveness, believing that commitment may help firms overcome obstacles associated with EO. In response, we collected survey data from executives in 126 small, high-technology firms, and found that EO and commitment to objectives enhanced sales growth. In addition, the study determined that commitment to objectives was associated with greater increased sales growth of companies high in EO, as compared to those low in EO

PS Booster Orbit Correction

At the end of the 2007 run, orbit measurements were carried out in the 4 rings of the PS Booster (PSB) for different working points and beam energies. The aim of these measurements was to provide the necessary input data for a PSB realignment campaign during the 2007/2008 shutdown. Currently, only very few corrector magnets can be operated reliably in the PSB; therefore the orbit correction has to be achieved by displacing (horizontally and vertically) and/or tilting some of the defocusing quadrupoles (QDs). In this report we first describe the orbit measurements, followed by a detailed explanation of the orbit correction strategy. Results and conclusions are presented in the last section

Coherent tune shift and instabilities measurements at the CERN Proton Synchrotron Booster

To understand one of the contributions to the intensity limitations of the CERN Proton Synchrotron Booster (PSB) in view of its operation with beams from Linac 4, the impedance of the machine has been characterized. Measurements of tune shift as a function of the intensity have been carried out in order to estimate the low frequency imaginary part of the impedance. Since the PSB is a low energy machine, these measurements have been done at two different energies, so as to enable us to disentangle the effect of the indirect space charge and resistive wall from the contribution of the machine impedance. An estimation of the possible resonant peaks in the impedance spectrum has been made by measuring a fast instability in Ring4

On the Optimum Dispersion of a Storage Ring for Electron Cooling with High Space Charge

With the intense electron beams used for cooling, matching of the ion and electron velocity over the largest possible fraction of the beam profile becomes important. In this situation, a finite dispersion from the ring in the cooling section can lead to an appreciable gain in the transverse cooling speed. Based on a simple model of the cooling force, an expression for the "optimum" dispersion as a function of the electron beam intensity, the momentum spread and other properties of the ion beam will be derived. This simple theory will be compared to measurements made on the Low Energy Ion Ring (LEIR) at CERN during 1997

The production of dense lead-ion beams for the CERN LHC

To reach the design luminosity for lead-ions in the LHC, the present Low Energy Antiproton Ring (LEAR) has to be converted into a Low Energy Ion Ring (LEIR). Since the present ECR lead-ion source does not provide sufficient intensity, the main goal of LEIR is to act as a low-energy (4.2MeV/u) accumulator where the ion beam is stacked and cooled (with the help of an electron-cooler) to reach the required intensity and emittances. An experimental program has been carried out at LEAR in recent years in order to test the cooling and stacking process with the present electron-cooler. A variety of results have been reported at previous conferences. This paper will focus on the electron cooling aspects resulting from the afore mentioned experiments. Taking into account the experienc

Electron cooling of PB54+^{54+} ions in the low energy ion ring (LEIR)

For the preparation of dense bunches of lead ions for the LHC, electron cooling will be essential for accumula tion in a storage ring at 4.2 MeV/u. Tests have been carried out on the LEAR ring (renamed LEIR for Low Energy Ion Ring) in order to determine the optimum parameters for a future state-of-the-art electron cooling device which would be able to cool linac pulses of lead ions in less than 100 ms. The experiments focused on the generation of a stable high intensity electron beam that is needed to free space in both longitudinal and transverse phase space for incoming pulses. Investigations on the ion beam lifetime in the presence of the electron beam and on the dependency of the cooling times on the optical settings of the storage ring will also be discussed. This paper concentrates on the cooling aspects with the multiturn injection, vacuum, and high intensity aspects discussed in a companion paper at this conference

Stability of cooled beams

Because of their high density together with extremely small spreads in betatron frequency and momentum, cooled beams are very vulnerable to incoherent and coherent space-charge effects and instabilities. Moreover, the cooling system itself, i.e. the electron beam in the case of e-cooling, presents large linear and non-linear 'impedances' to the circulating ion beam, in addition to the usual beam-environment coupling impedances of the storage ring. Beam blow-up and losses, attributed to such effects, have been observed in virtually all the existing electron cooling rings. The adverse effects seem to be more pronounced in those rings, like CELSIUS, that are equipped with a cooler capable of reaching the presently highest energy (100 to 300 keV electrons corresponding to 180 to 560 MeV protons). The stability conditions will be revisited with emphasis on the experience gained at LEAR. It will be argued that for all present coolers, three conditions are necessary (although probably not sufficient) for the stability of intense cold beams: (i) operation below transition energy, (ii) active damping to counteract coherent instability, and (iii) careful control of the e-beam neutralisation. An extrapolation to the future 'medium energy coolers', planned to work for (anti)protons of several GeV, will also be attempted