Fluxes over Varanasi during intensive observation period of MONTBLEX-90

ABSTRACT. MONTBLEX-90 data for an Intensive Observational Period (IOP) was extracted to investigate the thunderstorm and its impacts on surface layer at Varanasi on 27 July 1990. Sensible heat flux has been computed by profile, aerodynamic and eddy correlation methods. In addition to that. momentum and moisture fluxes have been computed for comparative diagnosis of situations before, at the time and after thunderstorm, Monin-Obukhov similarity theory has been used for quantification of the fluxes. Findings indicate that surface is more buoyant at the time of thunderstorm. Under this influence, maxima of moisture and momentum fluxes occur at the tin1e of thunderstorm. However, heat flux was found to be maximum before the thunderstorm, The results provide an understanding of surface layer turbulent transfer during stable and unstable conditions.

Shape and scaling of the mean-velocity profile in thermally-stratified plane-Couette flows

It has long been known from measurements that buoyant motions cause the mean-velocity profile (MVP) in thermally-stratified, wall-bounded turbulent flows to significantly deviate from its constant-density counterpart. Theoretical analysis has restricted attention to an “intermediate layer” of the MVP, akin to the celebrated “log layer” in the constant-density case. Here, for thermally-stratified plane-Couette flows, we study the shape and scaling of the whole MVP. We elucidate the mechanisms that dictate the shape of the MVP by using the framework of the spectral link (Gioia et al.; 2010), and obtain scaling laws for the whole MVP by generalizing the Monin-Obukhov similarity theory.

Resolving urban canopy flows: Scales, turbulence and boundary conditions in obstacle-resolving numerical models

<p>Large-eddy simulations are increasingly used for studying the atmospheric boundary layer. With increasing computational resources even obstacle-resolving Large-eddy simulations became possible and will be used in urban climate studies more frequently. In these applications, grid sizes are in the order of a few meters. Whereas major urban structures can be resolved in general, details like aerodynamically rough surface structures can not be resolved explicitly. Based on the original fields of application, boundary conditions in Large-eddy simulations were initially formulated for surfaces of homogeneous roughness and for wall-distances much larger than the roughness sublayer height (Hultmark et al., 2013). The height of the roughness sublayer depends on the size of small-scale obstacles present on the surface exposed to the flow (Raupach et al., 1991). Typically, boundary conditions are evaluated between the surface and the first grid level. Thus, grid resolution in obstacle-resolved Large-Eddy simulations should also be a question of scales and therefore has to be chosen carefully (Basu and Lacser, 2017; Maronga et al., 2020). <br />In several wind tunnel experiments presented here, we measured the near-wall influence of differently scaled and shaped objects on a flow and its turbulence characteristics. Experimental setups were replicated numerically using the PALM model (Maronga et al. 2019). In a first, more generic experiment, the flow over horizontally homogeneous surfaces of different roughness was investigated. In a second experiment, the spatial separation of the turbulence scales was investigated in a more complex flow case. These experiments lead to considerations on model grid sizes in urban type Large-eddy simulations. The limitations of interpreting simulation results within the urban canopy layer are highlighted. There is an urgent need to reconsider how near-wall results of urban large-eddy simulations are generated and interpreted in the context of practical applications like flow and transport modelling in urban canopies. <br /><br /><em><strong>References</strong></em><br /><em>Basu, S. and Lacser, A. (2017). A Cautionary Note on the Use of Monin–Obukhov Similarity Theory in Very High-Resolution Large-Eddy Simulations. Boundary-Layer Meteorol, 163(2):351–355.</em></p> <p><em>Hultmark, M., Calaf, M., and Parlange, M. B. (2013). A new wall shearstress model for atmospheric boundary layer simulations. J Atmos Sci,70(11):3460–3470.</em></p> <p><em>Maronga, B., et al. (2020). Overview of the PALM model system 6.0. Geosci Model Dev Discussions, 06(June):1–63.</em></p> <p><em>Maronga, B., Knigge, C., and Raasch, S. (2020). An Improved Surface Boundary Condition for Large-Eddy Simulations Based on Monin–Obukhov Similarity Theory: Evaluation and Consequences forGrid Convergence in Neutral and Stable Conditions. Boundary-Layer Meteorol, 174(2):297–325.</em></p> <p><em>Raupach, M. R., Antonia, R. A., and Rajagopalan, S. (1991). Rough-wall turbulent boundary layers. Appl Mech Rev, 44(1):1–25</em></p>

Ground Pressure under Mining Ore Bodies of Different Angles Based on Physical Simulation

Ground pressure characteristics of the ore body and the overburden deformation of the stope depend highly on the combined influence of geological conditions and mining disturbance. The ore body inclination, as a natural geological factor, has a nonnegligible effect on the underground mining. The ore angle plays a great role in the stress distribution of the overlying rock layer, resulting in the movement and destruction of the rock layer. The variation of the ore angle dominates the stress distribution of the overburden rock, the forms of movement, destruction, and the surface moving basin. Here, taking the geological mining conditions of the deep ore body mining in Jinning Phosphate Mine as the engineering background, we adopt a similar material ratio scheme of each rock layer in the mining area via the similarity theory and the principle of orthogonal experiment. We conduct systematic study on the strata movement, mining failure characteristics, and movement of the overlying rock in stope using a similar simulation test under two different ore angles of 20° and 50°. We found that, as the ore body inclination increases from 20° to 50°, the overburden unloading area of the stope extending to the deep part of the rock layer in the vertical direction is more obvious and its shape is more asymmetric about the stope center. The unloading area is more concentrated in the middle and upper part of the stope, while the upward development trend is more obvious. The relevant results can provide a certain reference for the underground mining of the mines and those with similar conditions.

Multicriteria Optimization of a Dynamic System by Methods of the Theories of Similarity and Criteria Importance

The problem of multicriteria optimization of a dynamic model is solved using the methods of the similarity theory and the criteria importance theory. The authors propose the original model of a positional system with two hydraulic actuators, synchronously moving a heavy object with a given accuracy. In order to reduce the number of optimizing parameters, the mathematical model of the system is presented in a dimensionless form. Three dimensionless optimization criteria that characterize the accuracy, size, and quality of the dynamic positioning process are considered. It is shown that the application of the criteria importance method significantly reduces the Pareto set (the set of the best solutions). This opens up the possibility of reducing many optimal solutions to one solution, which greatly facilitates the choice of parameters when designing a mechanical object.

On the scaling laws for low-temperature plasmas at macro and micro scales

The theoretical background and historical development of the similarity theory during the past decades are reviewed. We demonstrate similar discharges in local and nonlocal kinetic regimes, taking the low-pressure capacitive radio frequency (rf) discharges and microdischarges as examples. By using fully kinetic particle-in-cell simulations, we verify the similarity law (SL) and show a violation of frequency scaling (f-scaling) in the low-pressure capacitive rf plasmas. The similarity relations for electron density and electron power absorption are confirmed in similar rf discharges. With only the driving frequency varied, the f-scaling for electron density is also validated, showing almost the same trend as the similarity scaling, across most of the frequency regime. However, violations of the f-scaling are observed at lower frequencies, which are found to be relevant to the electron heating mode transition from stochastic to Ohmic heating. The scaling characteristics have also been comprehensively studied for microdischarges with dimensions from hundreds to several microns, with transition from secondary electron dominated regime to field emission regime. Finally, practical applications of the similarity and scaling laws are summarized.

Team Collaboration Assessment Method in Marine Engine Room Simulator

Based on the fuzzy mathematics and set similarity theory an intelligent collaboration assessment method for engine room simulator was studied. First, an integrated weighting method using both subjective and objective information was designed to obtain the weight vector; second, the fuzzy comprehensive evaluation method was used to calculate the completion degree of team collaboration, then the Dice coefficient and the Tversky coefficient were adopted to quantify the sequence factor, interactivity factor, redundancy factor and unauthorized factor of team collaboration effectiveness; third, a comprehensive calculation was achieved by the completion degree and the four factors to get the team collaboration assessment result; finally, the influence of the collaboration factors on assessment result was analyzed by an example, and it was found that even if the team get a higher task completion degree, due to some factors, the score is still low. The research shows that the collaborative performance of a team can greatly influence the final assessment result, the quantitative analysis of team collaboration can more objectively reveal the impact on collaboration. It is an effective method to add the influence of team cooperation factors to the traditional individual evaluation.