Given the current lack of experimental data for shock waves interacting with incoming transitional boundary layers, the goal of this study was to characterize the dynamics of such an interaction to better understand the fundamental fluid physics of these complex phenomena. Here, the mean flow field and time-dependent characteristics of a three-dimensional Mach 5 cylinder-induced shock-wave/boundary-layer interaction where the upstream boundary layer is transitional, have been studied experimentally. The interactions were generated with a right circular cylinder mounted on a flat plate. Streamwise–spanwise planar laser scattering from a condensed alcohol fog and schlieren imaging were used to characterize the mean and instantaneous structure of the interaction, and fast-response wall-pressure measurements on the centreline upstream of the cylinder enabled characterization of the unsteadiness. The pressure measurements show a mean pressure profile that resembles a composite of an upstream laminar profile and a downstream turbulent profile. The upstream influence location of the transitional interaction was approximately 8.5 diameters (, comparing well with other related studies of cylinder-induced interactions. Cross-correlations and coherence functions in the interaction suggest that the unsteadiness in the laminar region may be due to the entire ‘laminar’ region oscillating in response to the ‘turbulent’ unsteadiness of the intermittent region.

The characterization of a hypersonic impulse facility is performed using a variety of methods including Pitot probe scans, particle image velocimetry, and schlieren imaging to verify properties such as the velocity, Mach number, wall boundary layer thickness, and freestream turbulence intensity levels. The experimental results are compared to the numerical simulations of the facility performed with Ansys Fluent to compare the design and operational conditions. The presentation of results in this manuscript is prefaced by a description of the facility and its capabilities. The UTSA Ludwieg tube facility can produce a hypersonic freestream flow with a Mach number of 7.2 ± 0.2 and unit Reynolds numbers of up to 200 × 10⁶ m⁻¹. The Pitot probe profiles of the 203-mm-square test section indicate a 152 ± 10 mm square freestream core with turbulence intensity values ranging from 1% to 2%. Schlieren imaging of the oblique shockwaves on a 15° wedge model provided an alternate means of verifying the Mach number. Particle image velocimetry and previous molecular tagging velocimetry results showed a good agreement with the Pitot probe data and numerical simulations in the key parameters including freestream velocity, wall boundary layer velocity profiles, and wall boundary layer thickness.

Investigations of fluidic oscillators, or sweeping jet actuators, have primarily been conducted within the incompressible flow regime, which limits the accuracy of estimating fluidic oscillator performance for compressible flows. The objective of this study was to evaluate the effects of gas compressibility on the performance of a fluidic oscillator. A commonly used fluidic oscillator geometry (the Bray geometry) was scaled to five different sizes, 3D printed, and tested over a range of air flow rates. High-speed Schlieren images captured the sweeping jet exiting the fluidic oscillators, and custom MATLAB algorithms were used to calculate the oscillation frequencies and angles. A spectral proper orthogonal decomposition (SPOD) method was used to identify and compare the mode structures within the flow fields. All the results were compared using dimensionless parameters to observe performance trends. The results showed that the oscillation frequencies were directly proportional to the flow rate, while the oscillation angles were inversely proportional to the flow rate, regardless of scale size. The angular velocities were not proportional to the flow rate or scale size and exhibited maxima within the evaluated ranges. For all scale sizes, the mode structures were symmetric across the centerlines of the fluidic oscillators and extended further beyond the fluidic oscillators at higher flow rates. These results enable the prediction of fluidic oscillator performance, which can significantly improve the design process for an application where a fluidic oscillator may be used, such as aerospace applications, power generation, heat exchangers, or medical devices.

Carbon dioxide’s (CO₂) ability to reach the supercritical phase (7.39 MPa and 304.15 K) with low thermal energy input is an advantageous feature in power generation design, allowing for the use of various heat sources in the cycle. A small-scale supercritical carbon dioxide (sCO₂) power cycle operating on the principle of a closed-loop Brayton cycle is currently under construction at The University of Texas at San Antonio, to design and develop a small-scale indirect-fired sCO₂ Brayton cycle, acquire validation data of the cycle’s performance, and compare the cycle’s performance to other cycles operating in similar conditions. The power cycle consists of four principal components: A reciprocating piston compressor, a heating source, a reciprocating piston expander to produce power, and a heat exchanger to dissipate excess heat. The work explained in the present manuscript describes the theory and analysis conducted to design the piston expander, heating source, and heat exchanger in the cycle. Theoretical calculations indicate that using sCO₂ for the Brayton cycle generates 4.5 kW of power with the inlet pressure and temperature of 17.23 MPa and 358.15 K to the piston expander. Based on the fully isentropic conditions, the thermal efficiency of the system is estimated to be 12.75%.

Using data on all municipal “green” bonds issued from 2010 to 2021, the authors examine whether municipal bonds issued to finance green power projects command a premium (lower yield to maturity) relative to other similar-risk municipal green bonds. Consistent with the idea that green projects are easier to identify and certify in the setting of power generation, the authors find that green power bonds command a premium of 11 basis points relative to other similar-risk municipal green bonds. Those results support a nonpecuniary utility for such easily identifiable green investments. The authors illustrate the incremental value added from this reduction in the cost of capital and a gradual move from fossil fuel to green power generation for one of the largest municipal utilities in the United States.