Strong vertical gradients at the top of the atmospheric boundary layer affect the propagation of electromagnetic waves and can produce radar ducts. A three-dimensional, time-dependent, nonhydrostatic numerical model was used to simulate the propagation environment in the atmosphere over the Persian Gulf when aircraft observations of ducting had been made. A division of the observations into high-and low-wind cases was used as a framework for the simulations. Three sets of simulations were conducted with initial conditions of varying degrees of idealization and were compared with the observations taken in the Ship Antisubmarine Warfare Readiness/ Effectiveness Measuring (SHAREM-115) program. The best results occurred with the initialization based on a sounding taken over the coast modified by the inclusion of data on low-level atmospheric conditions over the Gulf waters. The development of moist, cool, stable marine internal boundary layers (MIBL) in air flowing from land over the waters of the Gulf was simulated. The MIBLs were capped by temperature inversions and associated lapses of humidity and refractivity. The low-wind MIBL was shallower and the gradients at its top were sharper than in the high-wind case, in agreement with the observations. Because it is also forced by land-sea contrasts, a sea-breeze circulation frequently occurs in association with the MIBL. The size, location, and internal structure of the sea-breeze circulation were realistically simulated. The gradients of temperature and humidity that bound the MIBL cause perturbations in the refractivity distribution that, in turn, lead to trapping layers and ducts. The existence, location, and surface character of the ducts were well captured. Horizontal variations in duct characteristics due to the sea-breeze circulation were also evident. The simulations successfully distinguished between high-and low-wind occasions, a notable feature of the SHAREM-115 observations. The modeled magnitudes of duct depth and strength, although leaving scope for improvement, were most encouraging.
The liquid metal film plasma facing component (PFC) is considered to be one of the most promising ways to realize a PFC capbable of operating for long periods. However, in the presence of a magnetic field, magnetohydrodynamic effects appearing in the liquid metal film flow directly influence the reliability of the flowing liquid metal limiter or divertor. In the present study, we consider the influence of flow rate, transverse magnetic field, and inclination angle, and conduct experiments on a liquid metal film flowing along an inclined conducting stainless steel plate. A laser profilometer (LP) and a high-speed camera are respectively adopted to obtain the local film thickness quantitatively, and its free surface structures qualitatively. We observe the magnetohydrodynamic effects of liquid metal film flow, such as the nonmonotonic change of film thickness, the reduction of film flow velocity, and the weakening of free surface waves in the direction of magnetic lines. Moreover, the film thickness increases with an increasing flow rate, whereas it decreases with an increasing inclination angle at a constant value of the magnetic field. When plotting the relative film thickening δ en, and the reduction of flow velocity against the Stuart number N, we find that there is a critical N, N cr ≈ 0.1, at which δ en begins to increase dramatically. The δ en sinβ with 1 • ≤ β ≤ 5 • , based on all of the experimental data, collapses into one line, which can be scaled as δ en sinβ ∼ N. The present experimental data and its scaling law may prove useful for estimating magnetohydrodynamic effects on liquid metal film flows when considering the design of liquid metal film PFCs.
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