Measurements in merging flow

Previous measurements of the velocity field in the vicinity of two intersecting submerged turbulent jets provided evidence that, contrary to the usual assumptions, intersecting flows may not necessarily be combined using vector addition of velocities or momentum flux densities. To gather additional experimental evidence on the details of the velocity field near the intersection of two submerged turbulent jets, this study measured time average velocity magnitudes and directions of two perpendicular intersecting axisymmetric submerged turbulent incompressible air jets of approximately equal strength. Because of the need to detect reverse flows, a three-dimensional pitot-type probe was used. This could sense yaw and pitch angles as well as velocity magnitudes. Two sets of measurements were taken. The more detailed set was confined to the plane of the nozzles, the less detailed set obtained cross-sectional data at four stations, three of these being in the observed reverse flow. The data show that the reverse flow spreads much more rapidly perpendicular to the nozzle plane than in the nozzle plane, whereas the forward flow is fairly symmetric. , Similarity profiles were found in both the forward and reverse flows. In the forward flow the distribution was essentially Gaussian. This was also true in the backward flow in the direction normal to the plane of the nozzles. In the plane of the nozzles the backward flow profiles were close to semi-elliptical or semi-circular, depending on the scales for plotting.U.S. Department of the InteriorU.S. Geological SurveyOpe

Insights into volcanic hazards and plume chemistry from multi-parameter observations: the eruptions of Fimmvörðuháls and Eyjafjallajökull (2010) and Holuhraun (2014–2015)

The eruptions of Eyjafjallajökull volcano in 2010 (including its initial effusive phase at Fimmvörðuháls and its later explosive phase from the central volcano) and Bárðarbunga volcano in 2014–2015 (at Holuhraun) were widely reported. Here, we report on complementary, interdisciplinary observations made of the eruptive gases and lavas that shed light on the processes and atmospheric impacts of the eruptions, and afford an intercomparison of contrasting eruptive styles and hazards. We find that (i) consistent with other authors, there are substantial differences in the gas composition between the eruptions; namely that the deeper stored Eyjafjallajökull magmas led to greater enrichment in Cl relative to S; (ii) lava field SO2 degassing was measured to be 5–20% of the total emissions during Holuhraun, and the lava emissions were enriched in Cl at both fissure eruptions—particularly Fimmvörðuháls; and (iii) BrO is produced in Icelandic plumes in spite of the low UV levels

Sensitivity of Outflow Peaks and Flood Stages to the Selection of Dam Breach Parameters and Simulation Models (Dam Safety Program)

published or submitted for publicationis peer reviewedOpe

Analysis of Multivariate Stochastic Hydrological Systems Using Transfer Function-Noise Models

123 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.In recent years, hydrologists have attempted, with encouraging results, to synthesize the accomplishments of univariate time series analysis and deterministic systems methods into the more general framework of stochastic dynamic systems. Nevertheless, many problems remain unsolved, others still unformulated.The aim of this thesis is to resolve some of these problems, using as guidelines a balanced view of the physical reality we want to understand and the mathematical methods we use as our tools.The premise is that our prior knowledge of the physical system we want to study, as well as our objectives, can considerably simplify our inquiry.The theme is the proper identification of model structure. This is important both for proper estimation of the model, as well as for its proper interpretation in terms of the hydrological processes involved.The main objective of this study is to develop a procedure for identification and estimation of a model for analysis of multivariate stochastic systems. A general stochastic systems model is presented and from it is derived a multiple input-single output transfer function-noise model that is well suited for modeling of hydrological systems. The model is then further developed to account for correlated inputs, which is often the case for hydrological systems. A general model building strategy is then developed and applied to real watershed systems.A multiple input transfer function-noise model for riverflow using correlated input series of precipitation, groundwater levels and temperature, was identified, estimated and checked using data for the Ellidaar River Basin in Iceland, demonstrating the validity of the proposed procedures. Its performance in terms of residual and prediction variances compares favorably with the performance of a univariate model for the riverflow. Its interpretation in terms of the geophysical processes involved is easier and more illuminating than is the case with the univariate model.The transfer function-noise model exploits our knowledge about the causal relations of the processes present in a watershed system. This leads to improved analysis and furthers our understanding of the hydrological system itself and its processes. It thus brings us back to inquiries about nature itself instead of approaching the problem as a mere statistical analysis.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Replacing intrusive thoughts: Investigating thought control in relation to OCD symptoms.

To access publisher's full text version of this article click on the hyperlink at the bottom of the pageControl of obsessive thoughts in Obsessive Compulsive Disorder (OCD) involves both avoidance and removal of undesirable intrusive thoughts. Thought suppression tasks tap both of these processes but experimental results have been inconsistent. Experimental tasks allowing more focused study of the processes involved in controlling intrusive thoughts may be needed. In two experiments, control over neutral, standardized intrusive and personal intrusive thoughts was investigated as participants attempted to replace them with neutral thoughts.Non-selected university students (Experiment 1: N = 61) and university students scoring high and low on self-report measure of OC symptoms (Experiment 2: N = 40) performed a computerized thought replacement task.In experiment 1 replacing personal intrusive thoughts took longer than replacing neutral thoughts. Self-reports showed that intrusive thoughts were rated more difficult to replace and were associated with greater thought reoccurrence during replacement, larger emotional reaction and more discomfort. These results were largely replicated in experiment 2. Furthermore, the high OC symptom group experienced greater overall difficulty controlling thoughts on the replacement task, experienced more reoccurrences of personal intrusive thoughts, larger emotional reactions and discomfort associated with them, and felt a greater urge to remove them.All participants were non-clinical university students, and older adults with OCD should be tested.The findings are in line with cognitive behavioural theories of OCD. They support the usefulness of thought replacement as a research paradigm to study thought control in OCD and possibly other psychological conditions characterized by repetitive thoughts.Icelandic Research Fund/100633021, Landspítali Scientific Research Fun