جستجوی مقالات مرتبط با کلیدواژه "بار هیدرولیکی" در نشریات گروه "فنی و مهندسی"

Labyrinth weir is an effective option to increase the discharge capacityý. This increases the crest length for a ýgiven width and head. The efficiency of a labyrinth weir can be increased with an arced configuration by improving the orientation of the weir cycles to the approach flow and to further increase the weir crest length. In this study, the hydraulic performance of the arced ýlabyrinth weirs is studied experimentally.ý The discharge coefficient is correlated to headwater ratio, downstream sidewall angle, and weir arc ýangle. Their effects on the weir efficiency are also investigated. The results ýindicate that by increasing the arc angle, the efficiency of the labyrinth weir can be increased ýup to 50%.ýþ þIn addition, the efficiency of the arced labyrinth weir can be increased up to ýalmost 4.5 times of that of a linear weir. Finally, according to the limitations of present study, ýa method is proposed for designing arced labyrinth weirs.ý

Weirs possess an essential role in dam safety and should spill floods with high return period. The designers can enhance the width of the weirs to increase the discharge capacity. But this has sometomes topography and economic limitations. Arced weirs can be considered as an alternative. A arced weir is a arcuate of a circle in plan-view that provides an increase in crest length for a given channel width that increas the flow capacity for the same head. Also when modification and capacity increase in existing spillways are necessary، this structure is recommended. In this paper، the hydraulic performance of arced weirs located in a reservoir has been studied experimentally. Firstly، dimensionless parameters affecting the performance of arced weirs is introduced using Buckingham π theorem. Then effect of arc angle (θ) and head water ratio (H0/P) on hydraulic performance of arced weirs was experimentally investigated and hydraulic performance of the tested arced weir geometries was compared with a linear configuration. For this purpose، Arches with different radius of curvature from linear to semi-circular configurations () and various head water ratio Were studied. To simulate reservoir conditions، a reservoir simulator was designed and built. Laboratory observations show that the converging of flow over a arced weir causes a locally bulge in the downstream of the weir. This phenomenon was named as flow mound. Results show that arc angle (θ) and head water ratio (H0/P) have a direct effect on the flow mound and an increase in each of them leads to mound height rise. The head-discharge relationship for arced weirs was determined by using a general form of the rectangular weir equation. Data from physical models were used to determine discharge and upstream head for the flat crested weirs installed in the reservoir. from discharge curves، it was found that with increasing angle of weir، that provide an increase in crest length for a given channel width، flow capacity increases for a given upstream head. Discharge coefficients as a function of H0/P for arced weirs are also presented and is compared with linear configuration. The results show that with increasing H0/P، discharge coefficient is declined for each tested configuration. Also with increasingθ، that leads to greater convergence of flow passing over the weirs، discharge coefficient decreases. Efficiency parameter is defined as the ratio of discharge of arced weir to that of liner weir with a same width. From efficiency curves it can be understood that the semi-circular weir can improve efficiency up to about 45%. However for all tested weirs، efficiency decreases with increasing H0/P and it gets close to 1. Finally، based on the results and limitations of this study، a methodology for the design of arced weirs located in the reservoir is presented. By using this method، the geometric parameters if an arced weir that is able to pass a certain flow rate for a given hydraulic head، will be determined.

Aniline is a first type amino aromatic compound and has various applications in different pharmaceutical, synthetic dye, plastic, and petrochemical industries. It is poisonous and its discharge into the environment causes serious hazards that warrant it removal by an efficient treatment process. In this study, the efficiency of rotating biological contactors in aniline removal was investigated using four 3-liter parallel systems (in two series). Two reactors in the first series had 27 disks. The second series had 14 discs with packings in each reactor with the same specific surfaces as compared to the first system.Aniline concentrations from 100 to 1200 mg/L and hydraulic loading rates from 1.57 to 6.28 L/m2.d were used throughout the study period in two treatments. The effect of disc rotation speed on system efficiency was also investigated. The results indicated that COD removal efficiency decreased with increasing hydraulic loading rate but increased with increasing disc speed from 5 to 15 rpm. The best removal efficiencies of 88 and 86 percent for RBCI and RBCII, respectively, were obtained for an aniline concentration of 400 mg/L, a hydraulic loading rate of 1.57 L/m2.d, and a disc speed of 15 rpm. Based on the results, although both systems yield almost equal efficiencies, the start-up period was shorter in RBCII with a clearer effluent due to the lower quantity of suspended microorganisms in the reactor than that in RBCI. Use of packing may decrease energy consumption for disc rotation due to the overall weight reduction of the system.