Laboratory Simulations of Local Winds in the Atmospheric Boundary Layer via Image Analysis

Abstract

In the atmospheric boundary layer, under high pressure conditions and negligible geostrophic winds, problems associated with pollution are the most critical. In this situation local winds play a major role in the evaluation of the atmospheric dynamics at small scales and in dispersion processes. These winds originate as a result of nonuniform heating of the soil, either when it is homogeneous or in discontinuous terrain in the presence of sea and/or slopes. Depending on the source of the thermal gradient, local winds are classified into convective boundary layer, sea and land breezes, urban heat islands, and slope currents. Local winds have been analyzed by (i) simple analytical models; (ii) numerical models; (iii) field measurements; (iv) laboratory measurements through which it is impossible to completely create the necessary similarities, but the parameters that determine the phenomenon can be controlled and each single wind can be separately analyzed. The present paper presents a summary of laboratory simulations of local winds neglecting synoptic winds and the effects of Coriolis force. Image analysis techniques appear suitable to fully describe both the individual phenomenon and the superposition of more than one local wind. Results do agree with other laboratory studies and numerical experiments.

Anabatic Flow along a Uniformly Heated Slope Studied through Large-Eddy Simulation

“…The anabatic flow along a finite slope uniformly heated is studied in a typical geometry of a laboratory experiment [28,32,61]. Figure 3b sketches the case setup: a double slope is placed in the centre of a water tank with dimensions of 2.0 × 0.6 × 1.2 m, respectively, for width (x), depth (y) and height (z).…”

“…On the other hand, pioneer field experiments have paved the way for key studies on the comprehension of the local processes driving the onset of the anabatic flows [26], the evolution of the anabatic layer [9] and its unsteadiness [27]. Laboratory experiments have delved into the initial development of the slope flow [11,28,29] and the implication of a later development on air quality [30]. Of more recent interest is the evaluation of rising plumes and flow separation from the slope due to the surface heating.…”

Exploiting Performance of Different Low-Cost Sensors for Small Amplitude Oscillatory Motion Monitoring: Preliminary Comparisons in View of Possible Integration

“…The images acquired by the Mikrotron EoSens camera were processed using a Lagrangian Particle Tracking technique named Hybrid Lagrangian Particle Tracking (HLPT) [27]. Although HLPT was developed for tracking a passive tracer seeding a fluid in fluid mechanics experiments [28], it was successfully employed here to track both the chessboard edges and the texture of objects undergoing the oscillatory motions. The cornerstone of the image analysis algorithm is the solution of the Optical Flow equation, which defines the conservation of the pixel brightness intensity at time ( (x, )):…”

Experimental and numerical analyses of a masonry arch under base impulse excitation

“…HLPT selects image features (image portions suitable to be tracked because their luminosity remains almost unchanged for small time intervals) and tracks these from frame to frame. Though HLPT was developed to process images from fluid mechanics experiments (Moroni & Cenedese 2015), it was successfully employed here to track the texture of objects undergoing the oscillatory motion. The cornerstone of the image analysis algorithm is the solution of the Optical Flow (OF) equation, which defines the conservation of the pixel brightness intensity at time t. Since the OF equation is insufficient to compute the two unknown in-plane velocity components (i.e.…”