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Taller pipe-framed greenhouses (pipe houses hereafter) are required to maintain a buffer zone for an improved thermal environment or to install devices for controlling the thermal environment, such as movable curtains. This study investigates the effect of ridge height on the distributions of the wind pressure coefficient (Cp) on pipe houses based on a wind tunnel experiment using 1:20 scale models. The width and length of a standard pipe house in full scale were 6 and 50 m, respectively, while the ridge height was varied from 3.16 to 5.16 m. The results indicate that the Cp distribution on the windward roof was strongly affected by the ridge height when the wind direction was normal to the ridge line. The windward roof was generally subjected to negative wind pressure (suction). The suction had a maximum value behind the windward eave, which increased in magnitude with an increase in ridge height. This effect may be related to the flow separation at the windward eave and reattachment on the windward roof. As a result, the drag and lift coefficients (CD and CL) obtained from the Cp distribution were also affected by the ridge height. High suctions were induced locally at the ridge corner of the leeward roof with an oblique wind. [ABSTRACT FROM AUTHOR]

A combination of an acidification reactor and an up-flow staged sludge bed (USSB) reactor was applied to treatment of molasses wastewater. The USSB, equipped with three gas solid separators, was selected because of superior organic removal by means of good retention of granular sludge. The combined system was continuously operated at mesophilic (35°C) conditions for 600 days. The USSB achieved a higa organic removal rate of 37 kgCOD/m³ day (organic loading rate of 43 kgCOD/m³ day with 86.2% COD -removal). The USSB retained high sludge concentration of approximately 58 gVSS/L based on the reactor volume. The retained granular sludge had good settle-ability with a sludge volume index (SVI) cf 4 to 20 ml/gSS. The retained sludge possessed a sufficient level of methanogenic activities for acetate (1.2 gCOD/gVSS day) and for hydrogen (1.7 gCOD/gVSS day). Analysis of microbial community revealed that genus Methanobacterium as hydrogen utilizing methanogen and order Methanosarcinales as acetate utilizing methanogen were detected in the retained sludge of the USSB reactor. The superior performance of the USSB was attributed to good retention of a large amount of granular sludge with high methanogenic activity. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the drag coefficient and the relationship between permeability (K) and momentum loss coefficients (Cf) of a tomato canopy for various leaf area densities. The experiments were conducted in a large-scale wind tunnel system with a tomato canopy. The static pressures and air velocity measurements were performed at several heights in the y-direction and various positions in the z-direction in the wind tunnel test section. The relationship between pressure drop and air velocity across the tomato canopy was determined using a porous medium approach. A drag coefficient of 0.31 was obtained for the tomato canopy used in the experiment. The permeability of the tomato canopy ranged from 0.006 to 0.65 for a leaf area density (L) of 4 (m² m-3), from 0.004 to 0.41 for L = 5, and from 0.003 to 0.3 for L = 6 as Cf changed from 0.1 to 1. Thus, a mature tomato canopy having L = 6 could be used with a canopy permeability of K = 0.017 and a momentum loss coefficient of Cf = 0.245. [ABSTRACT FROM AUTHOR]

More than two identical pipe-framed greenhouses (referred to as "pipe houses" hereafter) are often arranged in parallel. The wind pressure distributions on the pipe houses are significantly affected by the distance dp between them. This article investigates the effect of dp, on the distribution of wind pressure coefficients Cp on two or three pipe houses arranged in parallel based on a wind tunnel experiment using 1:20 scale models of a typical pipe house. Focus was on a wind direction perpendicular to the ridgeline. The distance dp varied from 0.25H to 6H, with H being the ridge height of the pipe house. The results indicate that the Cp distribution on the windward side of the first pipe house was similar to that for an isolated pipe house, while the Cp values on the roof and leeward wall were dependent on dp. On the other hand, the Cp values on the second and third pipe houses were generally negative and significantly affected by dp, in particular on the windward wall and roof. Very high suctions were induced on the leeward roof of the second pipe house near the ridge when the distance dp was small. The suctions may be induced by the second separation of the reattached flow on the windward roof at the location of the ridge. The local drag and lift coefficients, CD and CL, on the central chess-section were also computed from the Cp distribution. The influence of the adjacent pipe houses on the CD was significant, while the CL was less sensitive to dp. [ABSTRACT FROM AUTHOR]