Browsing by Subject "experiment"
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Item Experimental Investigation of Wind-Forced Drop Stability(2012-10-19) Schmucker, JasonThe stability of drops forced by both wind and gravity is a fluid mechanics problem relevant to heat exchangers, fuel cells, and aircraft icing. To investigate this phenomenon, drops from 15 micro-liters to 400 micro-liters were placed on the rough aluminum (RA = 3.26 micrometers) floor of a tiltable wind tunnel and brought to critical conditions, when the drop begins to run downstream. Various combinations of drop size, inclination angle, and flow speed were employed. A measurement technique capable of measuring full 3D drop profiles was implemented to investigate the drops' evolution toward runback. The measurement requires the comparison of the speckle pattern captured by an overhead drop image with a corresponding image of the dry surface. Stability limits for 235 drops are measured as functions of drop volume and surface inclination. Drops experiencing airflow alone are found to shed at a Weber number of 8.0 +/- 0.5. From measurement sequences of reconstructed drop profiles, the evolution of contact lines, drop profiles, and contact angle distributions are detailed. Contact line integral adhesion forces are calculated from contact angle distributions and related to the forcing air velocity. Drops whose stability limits are dominated by gravity are found to exhibit significantly different evolution toward runback than those dominated by airflow.Item Response of a slotted plate flow meter to horizontal two phase flow(Texas A&M University, 2005-02-17) Muralidharan, VasanthThe slotted plate flow meter has been widely tested as an obstruction flow meter during the past several years. It has been tested for both single-phase flows as well as for two-phase flows. Previous studies have revealed that the slotted plate flow meter is always better in performance and accuracy than the standard orifice plate flow meter. This study is primarily based on how a slotted plate responds to horizontal two-phase flow with air and water being used as the working fluids. The plates under consideration are those with beta ratios of 0.43 and 0.467. Experiments have been performed with six different configurations of the slotted plate test sections. The performances of the slotted plate flow meters will be compared to that of a standard orifice plate flow meter and then with a venturi. The effects of varying the upstream quality of the two-phase flow on the differential pressure and the coefficient of discharge of the slotted plates, the standard orifice plate and the venturi will be evaluated. Response characteristics at low differential pressures will be investigated. Tests for repeatability will be performed by studying the effects of the gas Reynolds number and the upstream quality on the differential pressure. The differential pressures across the slotted plates, the standard orifice plate and the venturi will be compared. Reproducibility will be evaluated by comparing the data obtained from all six different configurations. One of the main objectives of this study is to arrive at the best suitable procedure for accurately measuring the flow rate of two-phase flow using the slotted plate flow meter.Item Search for pair production of scalar top quarks decaying to a tau lepton and a b quark in 1.96-tev ppbar collisions(2009-05-15) Khotilovich, Vadim GennadyevichI present the results of a search for pair production of scalar top quarks (~t1) in an R-parity violating supersymmetric scenario using 322 pb_1 of pp collisions at ps = 1.96 TeV collected by the upgraded Collider Detector at Fermilab. I assume each ~t1 decays into a tau lepton and a b quark, with branching ratio B, and search for final states containing either an electron or a muon from a leptonic tau decay, a hadronically decaying tau lepton, and two or more jets. Two candidate events pass my final selection criteria, consistent with the expectation from standard model processes. I present upper limits on the cross section times branching ratio squared (~t1~t1)B2 as a function of the stop mass m(~t1). Assuming B = 1, I set a 95% confidence level limit m(~t1) > 153 GeV=c2. These limits are also fully applicable to the case of a pair produced third generation scalar leptoquark that decays into a tau lepton and a b quark.Item Sensitivity of Swept-Wing, Boundary-Layer Transition to Spanwise-Periodic Discrete Roughness Elements(2014-12-12) West, David EdwardMicron-sized, spanwise-periodic, discrete roughness elements (DREs) were applied to and tested on a 30? swept-wing model in order to study their effects on boundary-layer transition in flight where stationary crossflow waves are the dominant instability. Significant improvements have been made to previous flight experiments in order to more reliably determine and control the model angle of attack (AoA) and unit Reynolds number (Re'). These improvements will aid in determining the influence that DREs have on swept-wing, laminar-turbulent transition. Two interchangeable leading-edge surface-roughness configurations were tested: polished and painted. The baseline transition location for the painted leading edge (increased surface roughness) was unexpectedly farther aft than the polished. Transport unit Reynolds numbers were achieved using a Cessna O-2A Skymaster. Infrared thermography, coupled with a post-processing code, was used to globally extract a quantitative boundary-layer transition location. Each DRE configuration was compared to curve-fitted baseline data in order to determine increases or decreases in percent laminar flow while accounting for the influence of small differences in Re' and AoA. Linear Stability Theory (LST) guided the DRE configuration test matrix. In total, 63 flights were completed, where only 30 of those flights resulted in useable data. While the results of this research have not reliably confirmed the use of DREs as a viable laminar flow control technique in the flight environment, it has become clear that significant computational studies, specifically direct numerical simulation (DNS) of these particular DRE configurations and flight conditions, are a necessity in order to better understand the influence that DREs have on laminar-turbulent transition.Item Sensitivity of Swept-Wing, Boundary-Layer Transition to Spanwise-Periodic Discrete Roughness Elements(2014-12-12) West, David EdwardMicron-sized, spanwise-periodic, discrete roughness elements (DREs) were applied to and tested on a 30? swept-wing model in order to study their effects on boundary-layer transition in flight where stationary crossflow waves are the dominant instability. Significant improvements have been made to previous flight experiments in order to more reliably determine and control the model angle of attack (AoA) and unit Reynolds number (Re'). These improvements will aid in determining the influence that DREs have on swept-wing, laminar-turbulent transition. Two interchangeable leading-edge surface-roughness configurations were tested: polished and painted. The baseline transition location for the painted leading edge (increased surface roughness) was unexpectedly farther aft than the polished. Transport unit Reynolds numbers were achieved using a Cessna O-2A Skymaster. Infrared thermography, coupled with a post-processing code, was used to globally extract a quantitative boundary-layer transition location. Each DRE configuration was compared to curve-fitted baseline data in order to determine increases or decreases in percent laminar flow while accounting for the influence of small differences in Re' and AoA. Linear Stability Theory (LST) guided the DRE configuration test matrix. In total, 63 flights were completed, where only 30 of those flights resulted in useable data. While the results of this research have not reliably confirmed the use of DREs as a viable laminar flow control technique in the flight environment, it has become clear that significant computational studies, specifically direct numerical simulation (DNS) of these particular DRE configurations and flight conditions, are a necessity in order to better understand the influence that DREs have on laminar-turbulent transition.