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A thermohaline diffusive interface at large density stability ratios has been studied experimentally. Several interesting characteristics have been found. First, using a transient experiment technique, a transition from boundary-layer to core-regiondominated transport has been observed. Secondly, interface growth can occur through a series of steps owing to a sharp transition to a region with large interface growth rates. Thirdly, hysteresis occurs within the large density stability ratio region. Finally, the property-transport flux ratio increases as an interface switches from boundary- to core-dominated transports.

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Outdoor temperature lower than 50F and greater than 70F is shown to nearly double the transmission efficiency of the SARS-CoV-2 virus. Outdoor temperature is an important factor behind the current surge in US Covid-19 cases. Correlation of northern state infection data and outdoor temperatures is used to identify the change in disease transmission efficiency as northern states passed through the lower temperature bound (50F) in spring, and more recently transitioned to temperatures above the higher bound (70F). At current disease transmission efficiency levels, social distancing must be increased above a UMD Social Distance Index (SDI) level of 36 to stop the accelerated increase of daily infection cases. At current disease transmission efficiency (G=0.19) and SDI of 33, the US will approach 150,000 infections per day in September before declining as average US temperature falls below 70F. A primary reason for enhanced disease transmission below 50F and above 70F is attributed to inadequate indoor ventilation. Swing season occurs when outdoor temperatures are between 50F and 70F, and is the time of year when homes and buildings are opened to the outdoors. Increased fresh air ventilation (greater than 40cfm per person), improved air filtration (MERV11 and greater filters), and UVGI (Ultraviolet Germicidal Irradiation, 0.02WUV per cfm airflow) coupled with wearing face masks, 6ft distancing and surface sanitation are estimated to reduce indoor disease transmission probability to a third of the transmission probability resulting from standard building ventilation practice.

The need to measure the thickness of thin liquid films is evident from the number of methods that have been developed to do so. Many of these methods have significant drawbacks, such as intrusive probes or the dependence on a conductive liquid. A non-intrusive, automated, optical film thickness measurement technique has been developed to be used with a wide range of fluids and with virtually any flow configuration. In this method, light is reflected from the surface of a liquid film flowing over a transparent wall. This reflected light generates an image on the outside of the wall which is captured and digitized using a CCD camera and framegrabber card in a desktop computer. The image is processed to determine the positions of the reflected light rays, with which the film thickness and film slope are calculated. The entire process is automated and can be performed in less than 9 seconds on a 486 PC, allowing many data points to be collected efficiently. Film thicknesses as small as 0.03 mm can be determined using inexpensive components, with the possibility of greater precision using more advanced imaging equipment. An automated calibration procedure allows for the determination of the necessary physical parameters automatically, so the index of refraction of the test fluid or the test section wall need not be known a-priori. A prototype of the automated system generates static liquid measurements that agree to within 3% of measurements made using the needle-contact method. Film thickness data are also presented for an air-water system in cylindrical, annular, two-phase flow and compared with data from the literature.111