Browsing by Subject "wavelet"
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Item Large Eddy Simulations of Jet Flow Interactions Within Rod Bundles(2010-07-14) Salpeter, Nathaniel O.The present work investigates the turbulent jet flow mixing of downward impinging jets within a staggered rod bundle based on previous experimental work. The two inlet jets had Reynold's numbers of 11,160 and 6,250 and were chosen to coincide with the available data. Steady state simulations were initially carried out on a semi-structured polyhedral mesh of roughly 13.2 million cells following a sensitivity study over six different discretized meshes. Very large eddy simulations were carried out over the most refined mesh and continuous 1D wavelet transforms were used to analyze the dominant instabilities and how they propagate through the system in an effort to provide some insight into potential problems relating to structural vibrations due to turbulent instabilities. The presence of strong standing horseshoe vorticies near the base of each cylinder adjacent to an inlet jet was noted and is of potential importance in the abrasion wear of the graphite support columns of the VHTR if sufficient wear particles are present in the gas flow.Item Topics in genomic image processing(Texas A&M University, 2006-04-12) Hua, JianpingThe image processing methodologies that have been actively studied and developed now play a very significant role in the flourishing biotechnology research. This work studies, develops and implements several image processing techniques for M-FISH and cDNA microarray images. In particular, we focus on three important areas: M-FISH image compression, microarray image processing and expression-based classification. Two schemes, embedded M-FISH image coding (EMIC) and Microarray BASICA: Background Adjustment, Segmentation, Image Compression and Analysis, have been introduced for M-FISH image compression and microarray image processing, respectively. In the expression-based classification area, we investigate the relationship between optimal number of features and sample size, either analytically or through simulation, for various classifiers.Item Wavelet analysis study of microbubble drag reduction in a boundary channel flow(Texas A&M University, 2006-04-12) Zhen, LingParticle Image Velocimetry (PIV) and pressure measurement techniques were performed to investigate the drag reduction due to microbubble injection in the boundary layer of a fully developed turbulent channel flow. Two-dimensional full-field velocity components in streamwise-near-wall normal plane of a turbulent channel flow at Reynolds number of 5128 based on the half height of the channel were measured. The influence of the presence of microbubbles in the boundary layer was assessed and compared with single phase channel flow characteristics. A drag reduction of 38.4% was achieved with void fraction of 4.9%. The measurements were analyzed by studying the turbulence characteristics utilizing wavelet techniques. The wavelet cross-correlation and auto-correlation maps with and without microbubbles were studied and compared. The two-dimensional and threedimensional wavelet maps were used to interpret the results. The following observations were deduced from this study: 1. The microbubble injection within the boundary layer increases the turbulent energy of the streamwise velocity components of the large scale (large eddy size, low frequency) range and decreases the energy of the small scale (small eddy size, high frequency) range. 2. The wavelet cross-correlation maps of the normal velocities indicate that the microbubble presence decrease the turbulent energy of normal velocity components for both the large scale (large eddy size, low frequency) and the small scale (small eddy size, high frequency) ranges. 3. The wavelet auto-correlation maps of streamwise velocity shows that the intensities at low frequency range were increased with microbubble presence and the intensities at high frequency range were decreased. 4. The turbulent intensities for the normal fluctuating velocities at both low frequency and high frequency range were decreased with microbubble injection. This study presents the modifications in the characteristics of the boundary layer of channel flow which are attributed to the presence of microbubbles. Drag reduction studies with microbubble injections utilizing wavelet techniques are promising and are needed to understand the drag reduction phenomena.