Numerical Simulation of the Settling Flux of Biodeposition in a Bay with Cage Culture Through Similarity Theory and a Simplified Pollution Source

The settling flux of biodeposition affects the environmental quality of cage culture areas and determines their environmental carrying capacity.Simple and effective simulation of the settling flux of biodeposition is extremely important for determining the spatial distribution of biodeposition.Theoretically,biodeposition in cage culture areas without specific emission rules can be simplified as point source pollution.Fluent is a fluid simulation software that can simulate the dispersion of particulate matter simply and efficiently.Based on the simplification of pollution sources and bays,the settling flux of biodeposition can be easily and effectively simulated by Fluent fluid software.In the present work,the feasibility of this method was evaluated by simulation of the settling flux of biodeposition in Maniao Bay,Hainan Province,China,and 20 sampling sites were selected for determining the settling fluxes.At sampling sites P1,P2,P3,P4,P5,Z1,Z2,Z3,Z4,A1,A2,A3,A4,B1,B2,C1,C2,C3 and C4,the measured settling fluxes of biodeposition were 26.02,15.78,10.77,58.16,6.57,72.17,12.37,12.11,106.64,150.96,22.59,11.41,18.03,7.90,19.23,7.06,11.84,5.19 and 2.57 g d^(−1)m^(−2),respectively.The simulated settling fluxes of biodeposition at the corresponding sites were 16.03,23.98,8.87,46.90,4.52,104.77,16.03,8.35,180.83,213.06,39.10,17.47,20.98,9.78,23.25,7.84,15.90,6.06 and 1.65 g d^(−1)m^(−2),respectively.There was a positive correlation between the simulated settling fluxes and measured ones(R=0.94,P=2.22×10^(−9)<0.05),which implies that the spatial differentiation of biodeposition flux was well simulated.Moreover,the posterior difference ratio of the simulation was 0.38,and the small error probability was 0.94,which means that the simulated results reached an acceptable level from the perspective of relative error.Thus,if nonpoint source pollution is simplified to point source pollution and open waters are simplified based on similarity theory,the setting flux of biodeposition in the open waters can be simply and effectively simulated by the fluid simulation software Fluent.

Pollution Dispersion in Urban Street Canyons with Green Belts

In this study,numerical simulations were used to explore the effects of roadside green belt,urban street spatial layout,and wind speed on vehicle exhaust emission diffusion in street canyon.The diffusion of different sized particles in the street canyon and the influence of wind speed were investigated.The individual daily average pollutant intake was used to evaluate the exposure level in a street canyon microenvironment.The central and leeward green belts of the road were the most conducive to the diffusion of pollutants,while the positioning of the green belts both sides of a road was least conducive to the diffusion of pollutants.Pollutant levels increased with increasing canopy height,canopy width,and decreasing tree spacing,with optimal values of 12 m,7 m,and 0.4 H,respectively.This provides protection from pollution for low-rise residents and pedestrians.The results presented here can be used to improve the air quality of the street microenvironment and provide a basis for the renovation of old street buildings.

Analysis of the Thermal Performance of External Insulation in Prefabricated Buildings Using Computational Fluid Dynamics

This paper investigates the thermal performance of prefabricated exterior walls using the Computational Fluid Dynamics method to reduce energy consumption.The thermal performance of the prefabricated exterior wall was numerically simulated using the software ANSYS Fluent.The composite wall containing the cavity is taken as the research object in this paper after analysis.The simulation suggests that when the cavity thickness is 20 mm and 30 mm,the heat transfer coefficient of the air-sandwich wall is 1.3 and 1.29,respectively.Therefore,the optimal width of the cavity is 20 mm,and the most suitable material is the aerated concrete block.In addition,a comparative analysis is conducted on the cavity temperature in the wall under different conditions.It is proven that an intelligent environment control system can significantly improve thermal efficiency and provide a solid theoretical basis for further research in the external insulation of prefabricated buildings.