Secondary vortices in swirling flow

Twisted tapes are used to induce swirling flow and improve mixing. The flow induced by a 180 degree twisted tape with length (pitch) 60 mm and diameter 25.4 mm in a circular pipe was investigated using Laser Doppler Velocimetry (LDV) measurements. Tangential velocity profiles downstream of the twisted tape swirler were measured at multiple locations along the pipe axis, across the horizontal diameter of the pipe. The profiles showed an unexpected transition along the pipe axis from regular swirling flow to an apparent counter-rotation near the pipe axis, and then reverting back to regular swirling flow. Injecting fine air bubbles into the flow showed the existence of two co-rotating helical vortices superimposed over the main swirling flow. The close proximity of the two co-rotating vortices creates the local reversing flow at the pipe centerline. The secondary vortices are analyzed with high speed camera videos and numerical simulations.Comment: 2 videos include

Spectroscopy on a single trapped 137Ba+ ion for nuclear magnetic octupole moment determination

We present precision measurements of the hyperfine intervals in the 5D3/2 manifold of a single trapped Barium ion, 137 Ba+ . Measurements of the hyperfine intervals are made between mF = 0 sublevels over a range of magnetic fields allowing us to interpolate to the zero field values with an accuracy below a few Hz, an improvement on previous measurements by three orders of magnitude. Our results, in conjunction with theoretical calculations, provide a 30-fold reduction in the uncertainty of the magnetic dipole (A) and electric quadrupole (B) hyperfine constants. In addition, we obtain the magnetic octupole constant (C) with an accuracy below 0.1 Hz. This gives a subsequent determination of the nuclear magnetic octupole moment, {\Omega}, with an uncertainty of 1% limited almost completely by the accuracy of theoretical calculations. This constitutes the first observation of the octupole moment in 137 Ba+ and the most accurately determined octupole moment to date.Comment: 4 pages, 3 figure

Dynamics of swirling flows induced by twisted tapes in circular pipes

The present study describes the flow characteristics of swirling flows induced by twisted tape inserts in circular pipes. The study is focused on the secondary flow which is investigated experimentally and with numerical models. The results are expected to improve the paper manufacturing process by identifying and removing the detrimental secondary flow. Experimental tests show for the first time the existence of two co-rotating helical vortices superimposed over the main swirling flow, downstream of twisted tapes. The close proximity of the two co-rotating vortices creates a local counter-rotating flow at the pipe centerline. The flow is analyzed using LDV measurements and high speed camera visualization with fine air bubbles seeding which confirm that the helical vortices are stable. After extracting the characteristic tangential velocity profiles of the main vortex and of the two secondary vortices, it was observed that the maximum tangential velocity of all three vortices is the same, approximately half of the bulk velocity. The winding of the helical vortices is in the swirl direction and the pitch of the helical vortices is found to be independent of the inlet velocity. The experimental findings are confirmed by numerical simulations. The numerical results show that the helical vortices originate inside the swirler and evolve from single co-rotating vortices on each side of the tape. The flow characteristics are analyzed in detail. Swirlers with multiple twists and multiple chambers are shown to have less stable secondary motion and could be employed in applications were the secondary motion is detrimental.Ph.D.Committee Chair: Aidun Cyrus; Committee Member: Ghiaasiaan Mostafa; Committee Member: Glezer Ari; Committee Member: Seitzman Jerry; Committee Member: Webster Donald; Committee Member: Yoda Minam

Login to HeiDOK Preparation of cold Mg + ion clouds for sympathetic cooling of highly charged ions at SPECTRAP

The bound electrons in hydrogen-like or lithium-like heavy ions experience extremely strong electric and magnetic fields in the surrounding of the nucleus. Laser spectroscopy of the ground-state hyperfine splitting in the lead region provides a sensitive tool to test strong-field quantum electro dynamics (QED), especially in the magnetic sector. Previous measurements on hydrogen-like systems performed in an electron-beam ion trap (EBIT) or at the experimental storage ring (ESR) were experimentally limited in accuracy due to statistics, the large Doppler broadening and the ion energy. The full potential of the QED test can only be exploited if measurements for hydrogen- and lithium-like ions are performed with accuracy improved by 2-3 orders of magnitude. Therefore, the new Penning trap setup SPECTRAP - dedicated for laser spectroscopy on trapped and cooled highly charged ions - is currently commissioned at GSI Darmstadt. Heavy highly charged ions will be delivered to this trap by the HITRAP facility in the future. rnrnSPECTRAP is a cylindrical Penning trap with axial access for external ion injection and radial optical access mounted inside a cold-bore superconducting Helmholtz-type split-coil magnet. To reach the targeted accuracy in laser spectroscopy, an efficient and fast cooling process for the highly charged ions must be employed. This can be realized by sympathetic cooling with a cloud of laser-cooled light ions. Within this thesis work, a laser system and an ion source for the production of such a 24Mg+ ion cloud was developed and commissioned at SPECTRAP. An all-solid-state laser system for the generation of 279.6 nm light was designed and built. It consists of a fiber laser at 1118.5 nm followed by frequency quadrupling using two successive second-harmonic generation stages with actively stabilized ring resonators and nonlinear crystals. The laser system can deliver more than 15 mW of UV laser power under optimal conditions and requires little maintenance. rnAdditionally, a Mg+ ion source based on the electron-impact ionization of a Mg atomic beam was developed for pulsed injection into the trap. It was demonstrated that it delivers ion bunches with small time, momentum and energy spread, and it was used in combination with the laser system to create the first clouds of up to 2600 laser-cooled Mg+ ions in SPECTRAP. Fluorescence detection of the ions as well as electronic detection using the FFT-ICR technique was demonstrated. The analysis of the fluorescence lineshape indicated single-ion sensitivity and that a final temperature of about 100 mK was reached within a few seconds of cooling

An Analysis of the Impact of Personality Traits towards Augmented Reality in Online Shopping

The Internet as a shopping and purchasing medium has become an extensively researched topic. Augmented realty, in particular, allows consumers to explore their options and make personalised changes while shopping online. Our study aims to analyse the symmetry between the attitudes towards using the traditional electronic online shopping and the electronic commerce that uses augmented reality. We also investigate the effects of personality traits and the attitudes towards the Internet on the two electronic commerce forms. Our results show that the buying intention in online shopping is significantly higher in the case of augmented reality. Our results also reveal associations between personality traits and online buying behaviours, i.e., neuroticism and the openness to experiences being associated with the willingness to buy online. On the other hand, personality traits are proved to predict buying impulsiveness, the highest weight being represented by low emotional stability and high external locus of control. Further research should also include other dimensions, such as the perceived risks associated with online purchasing, self-efficacy or anxiety towards technology

An Analysis of the Impact of Personality Traits towards Augmented Reality in Online Shopping

The Internet as a shopping and purchasing medium has become an extensively researched topic. Augmented realty, in particular, allows consumers to explore their options and make personalised changes while shopping online. Our study aims to analyse the symmetry between the attitudes towards using the traditional electronic online shopping and the electronic commerce that uses augmented reality. We also investigate the effects of personality traits and the attitudes towards the Internet on the two electronic commerce forms. Our results show that the buying intention in online shopping is significantly higher in the case of augmented reality. Our results also reveal associations between personality traits and online buying behaviours, i.e., neuroticism and the openness to experiences being associated with the willingness to buy online. On the other hand, personality traits are proved to predict buying impulsiveness, the highest weight being represented by low emotional stability and high external locus of control. Further research should also include other dimensions, such as the perceived risks associated with online purchasing, self-efficacy or anxiety towards technology