Advanced Fluidics (United States)

Abstract The development of any atmosphere or ocean model warrants a suite of test cases (TCs) to verify its spatial and temporal discretizations, order of accuracy, stability, reproducibility, portability, scalability, etc. In this paper, we present a suite of shallow water TCs designed to verify the barotropic solver of atmosphere and ocean models. These include the non‐dispersive coastal Kelvin wave; the dispersive inertia‐gravity wave; the dispersive planetary and topographic Rossby waves; the barotropic tide; and a non‐linear manufactured solution. These TCs check the implementation of the linear pressure gradient term; the linear constant or variable‐coefficient Coriolis and bathymetry terms; and the non‐linear advection terms. Simulation results are presented for a variety of time‐stepping methods as well as two spatial discretizations: a mimetic finite volume method based on the TRiSK scheme, and a high‐order discontinuous Galerkin spectral element method. The experimental procedure for conducting these numerical experiments is detailed. It underscores several key considerations that vary depending on the chosen spatial discretization method. Finally, convergence studies of every TC are conducted with refinement in both space and time, only in space, and only in time. The convergence slopes match the expected theoretical predictions.

Abstract The vortex structure generated by a single jet emit into the main flow is known as a jet in cross flow and is a fundamental phenomenon that has been reported in many studies. On the other hand, high-velocity, oscillating, sweeping jets are also attracting attention for their engineering applications, but the flow generated by sweeping jets emitted into the main flow is not fully understood due to a highly unsteady fluid phenomenon. In the present study, a large-scale vortex structure generated by a sweeping jet emitted into the main flow at an angle of 30 degrees from the wall is clarified through numerical simulation. Sweeping jets form a single stream tube near the outlet, specifically at z/d < 4.5, and gradually split into two stream tubes from z/d > 4.5. The vortex rings are generated by the interaction among the sweeping jet, the main flow, and the wall surface. The vortex rings tilt perpendicular to the main flow as they develop but dissipate due to the rotation of the high-velocity jet and transform into numerous elongated vortices.

Abstract A sweeping jet produced by a fluidic oscillator has recently been examined from the viewpoint of flow separation control. Studies have proposed active flow control techniques for an airfoil based on sweeping jets. Most of these studies focused on the characteristics of the dynamic forces acting on the airfoil. However, the flow fields formed by the interaction between the sweeping jet and the main flow and their flow mechanisms are poorly understood. In particular, the vortex structure and flow mechanism formed by the interaction with respect to the velocity ratio between the sweeping jet and the main flow and the growth mechanisms of the vortex structure formed by the interaction have not been clarified. The detailed vortex structure generated by the interaction between the sweeping jet and the main flow was quantitatively examined using stereo PIV. The stream tube generated by the interaction between the sweeping jet and the main flow consists of two vortex tubes near the outlet of the sweeping jet at a location of 1.0d to 11.3d. At locations of 22.5d and 30.0d, a pair of vortex tubes gradually separates. Each vortex tube develops in the wake and its vorticity weakens.

Abstract Multiplexed solid‐contact ion‐selective electrodes (SCISEs) are fabricated using printed circuit board (PCB) and mesoporous carbon black (MCB) as ion‐to‐electron transducer (solid contact). Four sensor configurations were examined and showed that in addition to MCB, the sensor configuration plays crucial role in the stability of the potential response. The enhanced sensor stability was also linked with suppression of transmembrane flux of water. The sensors exhibited near‐Nernstian sensitivity (58.1 mV/dec for K+ ISEs and −55.1 mV/dec for NO3‐ ISEs), low detection limits (1.5–2.2 μM), and good short‐term stability (∼0.1 mV/min). Sensors can be stored dry and used without preconditioning. This work demonstrates a promising approach to combining PCB technology and carbon black for large‐scale production of low cost ISEs for point‐of‐care testing, wearables, or in situ field measurements.

Abstract Herein, we demonstrated miniature solid‐contact ion‐selective electrodes (ISEs) using a commercial mesoporous carbon black (MCB) as ion‐to‐electron transducer. MCB is attractive in its high surface area, good conductivity, relative low cost and availability. ISEs for potassium (K+) and nitrate (NO3−) ions were prepared by subsequently coating the sealed glass capillaries (1.5 mm) with MCB and ion‐selective membranes. Addition of MCB substantially stabilized electrode response by providing adequate double‐layer capacitance and lowering resistance by more than 100× compared to the coated‐wire electrodes. The electrodes exhibited near‐Nernstian slopes of 59.6 (K+ ionophore), 57.8 (K+ ion‐exchanger) and −54.8 (NO3− ion‐exchanger) with standard solutions in the range of 10−5 to 10−1 M. Fast response (∼10 s) and reproducible sensitivities were also obtained in a mixed electrolyte containing interfering ions, although with a baseline drift of 2–10 mV/day in the long term. Importantly, the electrodes can be simply stored in air between measurements and used directly without conditioning in solutions. With simple fabrication and free maintenance, these sensors offer a low cost and convenient alternative to bulk ISEs, especially when sample volumes or space are limited.