reza sajadifar; javad Ahadiyan
Abstract
Introduction: In this research the spreading coefficient of dense flow under the jet hydraulic in the surrounding fluids of clean water and at the accepting environment with the low depth and high depth has been analyzed. The analyzed parameters are included of discharge injection, density of contaminating ...
Read More
Introduction: In this research the spreading coefficient of dense flow under the jet hydraulic in the surrounding fluids of clean water and at the accepting environment with the low depth and high depth has been analyzed. The analyzed parameters are included of discharge injection, density of contaminating fluid, diameter and angle of the contraction of jet nozzle and shallow and deep water ambient fluid.
Materials and methods: These tests are being conducted in the flume laboratory. The results obtained from the tests show that the circulation coefficient is a function of contaminating density and the depth of the accepting environment, such that with increase in the density, the accepting environment depth coefficient will an increase and circulation and coefficient dispersal with the densities of 15, 30, 50, 200 g/lit, are 0/121, 0/135, 0/153, and 0/196 respectively. On the one hand, in the accepting environment depth it has been shown that increase in the Froude density number up to 30 causes decreases in the circulation and coefficient dispersal and then this coefficient will be used in the constant amount of 0/1.
Results and Discussion: Results showed that the profiles taken by the GOSEN distribution function and also coordinate the direction taken compliance with about 8/9% errors. Therefore the amount of dispersion of drained stream with accepted error and the use of accepted axial- radial coordinate have been extracted. The most speed has been taken place in the central line and getting further from the center reduces the speed. On the one hand, along the moving path the limits of Jet reduce which is surrounding conditions. On the other hand, considering the continuity coordination in different places from the jet, and reduction of speed, the dispersion width increases. And also according to the analysis conducted it is clear that speed profiles measured is consistent with Gussein distribution. Generally the flow of the sank jets, which are located at an accepting running flow such as rivers or seas, consisted of two areas, with different equations. These two areas are consisting of area (field) close to the jet and area (field) far from jet. When two fluids with different consistencies interfere with each other, it produces a floating jet. In this phenomenon the effective power consisted of composition of floating powers and the amount of movement. Now, if the injected fluid is heavier than the acceptant fluid, the jet will have a negative floating condition and if it is lighter, the jet will have positive floating condition. Ls are the space between an acceptance static fluid and a homogenous fluid and the amount of momentum is more than the floating charge. If the flow of acceptor fluid and jet are not in the same direction, it shows the jet penetration in the fluid, but if both are in the same direction, in this case Ls shows the limitation of the jet. The power and ability of the jet depend directly on the Frode density number. Since in the Frood number, higher density causes stronger jet with the initial momentum. Since the distribution of coefficient after the Frode density number densimetric 30 will be used at the constant amount, it can be said that the amount before this is the "jet near field and the amount more than this is jet far field. The amounts for diagonals 5, 8.15 mm are 141/9, 225/90, 423/57 mm respectably. Results show that in the acceptor environment with low depth, development of the moving borders is nonlinear with second degree equations. In this condition maximum disposal coefficient is equal to 0/28 and its minimum is 0/095. In a low depth environment it has been seen that in a relatively constant depth increase in the Frode density from 52 to 120 the amount of coefficient dispersal decreases up to 2/7 times. This is when for a constant Frode density, the average increase in the relative depth from 5 to 15 the amount of coefficient dispersal is about 16.5%. Increase in the Frood density number causes decrease in the coefficient dispersal. This decrease is due to increase in the speed of fluid entrance in the jet and more energy drop due to more friction with the fluid jet borders. In the other words, increase in the amount of momentum coefficient dispersal will be reduced. At the constant hydraulic conditions, with increase in the relative depth, acceptor environment coefficient dispersal increases which is due to decrease in the adhesion condition and decrease of the depth. Acceptor environment with low depth initial entering speed increases which is due to increase in the Frode density number in one constant length which causes decrease in the floating parameters. On the one hand, increase in the entering speed the amount of friction with the border and therefore the amount of energy drop increases and cause disturbance in the flow with the moving jet borders.
Conclusion: In the low depth acceptor environment with a relative constant depth, the amount of percentage of increase in the density of Frode number decreases. Considering the tests conducted it has been shown that the coefficient of dispersal in the acceptor environment low and high depth are opposite to the Frode density number, which means that with an increase in the density of Frode number, the coefficient dispersal decreases. It is also shown that increase in the depth, causes increase in the coefficient dispersal until it reaches a constant amount. Dependency of coefficient dispersal in relation to Densimetric Frode number and convergence angle show increase in the effect of density of Frode number in the convergence angle.
M. Daryaee; M. Kashefipoor; J. Ahadiyan; R. Ghobadiyan
Abstract
چکیده
احداث ساختمان ها و سازه های مختلف، باعث به هم فشرده شدن ذرات خاک و در نتیجه نشست خاک می گردد. نشست خاک تابع عوامل مختلفی مانند تغییر شکل فشاری، خارج شدن هوا و آب ...
Read More
چکیده
احداث ساختمان ها و سازه های مختلف، باعث به هم فشرده شدن ذرات خاک و در نتیجه نشست خاک می گردد. نشست خاک تابع عوامل مختلفی مانند تغییر شکل فشاری، خارج شدن هوا و آب از خلل و فرج و ... می باشد. یکی از روش های محاسبه نشست، استفاده از شاخص فشردگی است که از طریق آزمایش تحکیم بدست می آید. تعیین این ضریب از طریق آزمایش تحکیم بسیار وقت گیر است. لذا از گذشته سعی بر این بوده که شاخص فشردگی را به پارامترهای فیزیکی خاک از قبیل حد خمیری، حد روانی، نسبت پوکی، چگالی نسبی که همگی به سادگی قابل اندازه گیری هستند، ارتباط دهند. به همین جهت روابط تجربی زیادی در این خصوص ارائه شده است. در این مقاله با استفاده از شبکهی عصبی مصنوعی5 (ANN) ، همبستگی آماری بین خصوصیات فیزیکی خاکهای ریزدانه و شاخص فشردگی مورد بررسی قرار گرفت. همچنین یک واسنجی بین روش های تجربی مختلف موجود برای تعیین شاخص فشردگی با شاخص فشردگی اندازه گیری شده در آزمایشگاه صورت پذیرفت. نتایج نشان داده است که رابطه رندون و هررو از میان روابط تجربی با بالاترین ضریب همبستگی و کمترین درصد خطا، بالاترین دقت را در برآورد شاخص فشردگی دارد. در مقابل شبکه های عصبی مصنوعی شاخص فشردگی را با دقتی بالاتر و درصد خطای کمتر از رابطه رندون و هررو برآورد می کند. همچنین کالیبره کردن ضرایب رابطه رندون و هررو با استفاده از مجموعه اطلاعات موجود، تاثیر چندانی در دقت این رابطه برای تخمین شاخص فشردگی خاکهای منطقه مورد نظر ندارد.
واژههای کلیدی: خاکهای ریزدانه، شاخص فشردگی، شبکه های عصبی مصنوعی، خصوصیات فیزیکی خاک
J. Ahadiyan; S.H. Musavi Jahromi
Abstract
Abstract
In the present article, effective parameters of the buoyant jets have been evaluated in the stagnant ambient fluid. The jet parameters, geometry parameters and environmental parameters are investigated. Using dimensional analysis, a set of dimensionless functions was obtained. To achieve the ...
Read More
Abstract
In the present article, effective parameters of the buoyant jets have been evaluated in the stagnant ambient fluid. The jet parameters, geometry parameters and environmental parameters are investigated. Using dimensional analysis, a set of dimensionless functions was obtained. To achieve the exact functions, a physical model was built in the hydraulic laboratory of Shahid Chamran University, Iran (SCU). 215 experiments were set on base of different jet diameter, different concentration of jet injection and different convergence angle of jets. To precede the goals of the present study, the positive mixing length and trajectory characteristics from a buoyant jet and the maximum length of upper and inferior limits of trajectory have been considered. The velocity profiles of adjacent sections near and far field of location jet injection was measured using profiler acoustic, UVDP. The velocity profiles were compared with the theoretical normal Gaussian distribution. Finding shows that the gathered data in this field have been satisfactory correlated. In addition the concentration and dilution in the different sections along the jet flow were measured. Findings show there are satisfactory correlation between experimental data and theoretical formula. The lengths of falling jet trajectory were analyzed as the ratio of trajectory length to port diameter (x/dp) versus relative trajectory elevation ((Z0-Zu)/x). According to the results, increasing on concentration of jet flow causing a density gradient between jets and receiving fluid and change in the buoyancy forces involved, has major influence on the lengths of falling trajectory. Findings show there is a nonlinear correlation between the trajectory characteristics and jet flow properties. As change of contraction angle, from 15 to 90 degrees, upper limit of trajectory increased to 25 percents. While contraction angle increase from 15 to 90 degrees, the inferior limit increase to 28 percents.
Key words: Buoyant jet, Contraction angle, Trajectory, Flow pattern, Spreading Coefficient
