Development of a Mechanistic Method to Obtain Load Position Strain in Instrumented Pavement

To study the in-situ response and performance of asphalt pavement, instrumenting pavement with a variety of sensors has become one of the most important tools in the field or accelerated load facilities. In the dynamic response collection process, engineers are more concerned with the load position strain of the pavement structure due to wheel wander. This paper proposes a method to obtain the load position and the strain at the load position when there is no lateral-axis positioning system based on multilayer elastic theory. The test section was paved in the field with installed strain sensors to verify and apply the proposed method. The verification results showed that both the calculated load position and load position strain matched the measured values with an absolute difference range of 5–60 mm, 0.5–2.5 με, respectively. The application results showed that the strain at the load position calculated by the proposed method had a good correlation with the temperature, as expected.

Experimental setup for studying two-phase flows in micro-and minichannels at ultra-high heat fluxes: methodology and first experimental results

The study of phase-change phenomena under high and ultra-high heat fluxes is urgent because of fast development of electronics and microelectronics. We have developed a test section with power of 3.5 kW with a heater of 1x1 cm2 and adjustable geometry of the channel for achieving ultra-high heat fluxes in flow boiling and shear-driven liquid film experiments. The methodology of calculating heat losses in the test section is proposed and verified by flow boiling experiment versus another well studied test section. Observed trend of decrease of relative heat losses with increase in the heat flux makes it possible to assume that the heat flux as high as 2.5 kW/cm2 can be reached by this test section.

Experimental Investigation of Acoustic Atomization in Liquid Loading Horizontal Gas Wells

Enhancing the production in liquid-loaded horizontal natural gas wells using an acoustic liquid atomizer tool is proposed as a possible artificial lift method. The more liquid that is converted to droplets, the more available gas is able to carry the liquid to the surface, resulting in an increase in production. The acoustic atomizer was selected to be the atomization device as it can create very small droplets at certain frequencies leading to a mist flow. The contribution of this research includes obtaining experimental data using different laboratory procedures for horizontal and slightly inclined tubulars. Two-phase (gas and water) injection stream lines are joined to the test section to introduce gas and water at desired rates. An ultrasonic atomizer inside the test section is used to better understand the atomization mechanism as an artificial lift technique. Several experiments with varying factors influencing the acoustic properties are tested including varying liquid and gas rates, four different frequencies, two different flow pipe inclination angles, and two different acoustic device orientations. The results show that when using frequencies of 62 and 62.5 kHz, the outcomes were almost identical for horizontal and slightly inclined pipe. Both frequencies reduced liquid film accumulation by 1% at lower (0.001 m/s) and higher (0.0168 m/s) liquid velocities while gas velocity was kept at 14 m/s. The performance of the acoustic tool was highly dependent on the orientation of the tool inside the flow loop due to its atomizer geometry, shape and size. Sprayers facing up (0°, original case) helped the droplets to be carried by the gas since the gas occupies the top portion of the pipe and did not block the atomizer. The sprayers failed to work while facing the bottom of the pipe (180°) due to water accumulating around the sprayers, plugging the atomizer and hindering it from working. Using an orientation of 90° (sprayers facing sideways) provided better results and positive impact in reducing the liquid film level. The efficiency of the tool decreases in slightly inclined wells. As more liquid quantity accumulated in the well, the atomization technique seems to be slow in reducing the liquid film height. This research presents a set of diverse experimental data to suggest acoustic atomization might be used as a possible artificial lift technique in horizontal wells. The technique shows a 1-4% improvement which might be experimental error or in experimental control. Thus, the device used in the lab needs improvement to work as efficiently as other artificial lift techniques to possibly enhance production.

X-ray Imaging-Based Void Fraction Measurement in Saturated Flow Boiling Experiments with Seawater Coolant

Recent studies have shown that the presence of dissolved salts in water can exhibit peculiar flow boiling and two-phase flow regimes. Two-phase flow and convective flow boiling are typically characterized with the help of void fraction measurements. To quantitatively improve our understanding of two-phase flow and boiling phenomenon with seawater coolant, void fraction data are needed, which can not be obtained from optical imaging. In this paper, we present experimental void fraction measurements of saturated flow boiling of tap water and seawater using X-ray radiography. X-rays with a maximum energy level of 40 KeV were used for imaging the exit region of the heated test section. At lower heat flux levels, the two phase flow in seawater was bubbly and homogeneous in nature, resulting in higher void fractions as compared to tap water. With an increase in heat flux, the flow regime was similar to slug flow, and void fraction measurements approached similarity with tap water. The predicted pressure drop using the measured void faction shows good agreement with the measured total pressure drop across the test section, demonstrating the validity of the measurement process.

Design, Construction and Evaluation of an Oscillating Vane Gust Generator for Atmospheric Flow Simulation

The study of unsteady aerodynamic phenomena in wind tunnels is supported by gust-generating devices capable of generating adjustable magnitude and periodicity velocity fluctuations in a flowfield. Gusts are typically generated actively by introducing moving vanes to direct the flow, or passively by tailoring the boundary layer growth and shape in the tunnel. The flow facility used here is a student-built closed-return low-speed wind tunnel, with a test section size of 750 mm × 750 mm and a maximum speed of 25 m/s. A two-vane gust generator utilizing NACA0018 airfoil sections of 150 mm chord length was designed and installed upstream of the test section. The flowfield was mapped with the installed vanes with and without gust actuation, utilizing a hot wire system. The tunnel with gust vanes exhibits a spatially uniform baseline turbulence intensity of 5%, with a steady state velocity deficit of 1 m/s in the vane–wake region. Upon introducing the gusting conditions at vane deflection angles of up to ±45°, velocity differences of up to 4 m/s were attained at 18 m/s freestream velocity at oscillation frequencies ranging between 1 Hz and 2 Hz.

Oblique shock wave reflection at plasma array presence

This work discusses the effect of a filamentary plasma array on shock wave (SW) reflection pattern and on a shock-induced separation zone geometry. It includes experimental and computational components both. The experimentation was performed in the supersonic blowdown test rig SBR-50 at the University of Notre Dame at flow Mach number M=2, stagnation pressure P0=1.7-2.7 bar and stagnation temperature T0=300 K. Oblique shock wave generator composed of a symmetric solid wedge was installed on the top wall of test section while the filamentary plasma generator was arranged on the opposite wall. Thus, the main SW originating from the wedge impinged the plasma area. As a result of the SW-plasma interaction, the flowfield was significantly modified, including a shift of the main SW upstream and redistribution of wall pressure over the test section. The computational analysis allowed a 3D reconstruction of the SW interaction with the plasma array. The physics of SW-plasma array interaction are also discussed.