Sudden pipe expansions have been known as efficient hydraulic energy dissipaters for a long time. The complex phenomenon of flow separation and velocity discontinuity at the interface of incoming jet and the recirculation flow, results in intensive shear and tensile rupture of the fluid and the associated destructive phenomenon of cavitation. This paper focuses on aeration in sudden pipe expansion as a remedy to recover the effects of cavitation. The experimental setup consists of a sudden pipe expansion with an expansion to inflow diameter ratio of 3.675. Variation of air content ratio with respect to the Reynolds number and effect of air entrainment on time averaged velocity and pressure distribution is investigated. Finally a combination of sudden pipe expansion and aeration is recommended for energy dissipation at bottom outlets and tunnel spillways.

The aim of the present work is the investigation of the turbulent flow field downstream of an axisymmetric sudden expansion with a large aspect ratio of D/d = 12, 3. For the fundamentally understanding of the flow some numerical results are presented. They were achieved by using the RANS approach and SST turbulence model. The flow field is characterized by a jet-like flow near the nozzle exit and a large toroidal recirculation zone. The x-component of the velocity u was measured using one-component laser Doppler velocimetry. Axial and radial velocity distributions as well as some velocity spectra were measured. The spectra were calculated from the velocity signal using the Sample-And-Hold method together with the refinement technique. At the axial half length of the recirculation zone at the edge of the jet flow a narrow band peak was observed in spectra, suggesting the existence of large-scale fluctuations or instability of the flow field. Further investigations reveal that this effect is locally limited and shows no sensitivity against changes of the inlet conditions, e. g. the Reynolds number and velocity profile.

A new model to calculate heat eddy diffusivity in separating and reattaching flows based on modification of constant Prt is proposed. This modification is made using an empirical correlation between maximum Nusselt number and entrance Reynolds number. The model includes both the simplicity of Prt=0.9 assumption and the accuracy of two-equation heat-transfer models. Furthermore, an appropriate low Reynolds number k - e model is adopted for calculation of eddy viscosity. The model is used for prediction of Nusselt number distribution at various ranges of Reynolds number and expansion ratio. The numerical results are compared with available experimental data in the literature and have shown good agreement. The CPU time for the present model is about 33% less than that of two-equation heat-transfer model.

The dispersion of solid particles in zones of turbulent recirculation flow is of interest in various technological applications. Many experimental studies have been developed in order to know the contribution of Stokes numbers and mean drift parameter on the entering and dispersion of particles in the recirculation zone however to our knowledge there are not numerical studies reported about it. In this work, we made a numerical study of the incompressible turbulent flow laden with solid particles in sudden expansion pipes with different expansion ratios and different Reynolds number upstream of the pipe, using LES and Germano dynamic model with JetCode program for the continuous phase (air). The solid particles movement (different diameters were considered) was solved by using a Lagrangian tracking algorithm coupled to JetCode taking into account only drag and gravity forces supposing one way coupling. Finally, we calculated Stokes numbers based on the different fluid time scales and the mean drift parameter for all the solved cases and studied their isolated effect on the solid particle dispersion in the recirculation zones by computing the concentration by means of the particle number within the recirculation zones. Our results coincided with the experimental findings reported by others authors: the particle concentration exhibits a maximum value as the Reynolds number upstream in the pipe is decreased, the pipe expansion ratio is increased and particle size is decreased. Regarding the results obtained numerically about the solid particle dispersion within turbulent recirculation zones in terms of Stokes numbers and the mean drift parameters, coincided adequately with the experimental results.

Sudden expansion can be used as energy dissipater in the pressurized pipe flows. As the induced cavitation bubbles will cause large structural damage, estimating the amount of maximum developed under-atmospheric pressure (MDUAP) in sudden expansions is of particular interest. Pressure fluctuations, domain and intensity of cavitation depend on the amount of MDUAP. Therefore, estimating the amount of MDUAP is a vital task in the design stage. To carry out this study, various sudden expansions were developed by changing the geometry and flow properties. The developed sudden expansions were modeled using the CFD modeling technique. The obtained CFD based results were successful in analyzing the experimental observations. Therefore, the simulation model is capable of predicting the MDUAP under different conditions. In this paper, the M5P data mining model is used for the first time for establishing a fast, accurate, and cost-effective linkage between the geometry and flow properties of a sudden expansion and the amount of MDUAP. The results show that the developed M5P based simple rules can accurately predict the amount of MDUAP.

Introduction: The aim of this study is evaluation of efficacy of lacrimal sac localization with lacrimal probe without using light pipe. The study was based on nonrandomized prospective clinical trial with one year follow up period.Methods: A group of 40 patients operated since march 2001 to December 2004 The operation was Endoscopic Dacryocystorhynostomy and localization of lacrimal sac, which was performed with a lacrimal probe inserted in lacrimal sac. With pushing the probe inferomedialy pierces lacrimal sac lacrimal bone, and nasal musca over the bone. Follow up includes symptom evaluation such as epiphora and endoscopy. Success was defined as relief of symptoms & duct patancy with irrigation for a 1 year period.Results: 29 patients were male (72.5 %) and 11 were female (27.5 %). Mean age was 37.5 (with SD±12.26) in 20 patients right eye involved, left eye involved in 16 cases and in 4 cases both eyes involved. For 3 patients septoplasty was done besides EDCR. success rate was 82.5% and no complication was seen.Discussion: the use of lacrimal probe for lacrimal sac localization is a safe and easy method and don't have light pipe limitations then can replace light pipe.

Purpose: The aim of this research was to study the effects of different doses of LIF on GVBD and MII development rate and cumulus expansion.Materials and Methods: Immature mice superovulated with HMG and GV oocytes obtained from ovary 48 hours later. The GV oocytes were cultured in TCM199 with 100, 500 and 1000 IU /ml LIF. Cumulus expansions were evaluated with two examiners and numbers of MII oocytes were recorded. For denuding the oocytes hyaloronidase was used.Results: Our results showed that the rate of GVBD and MII development increased in groups with LIF compared with control group. Rate of MII development with 1000 IU/ml LIF was significantly higherthan that of control group (P<0.05). Cumulus expansion in group with 1000 IU/ml LIF improved significantly compared with control group (p<0.05).Conclusion: Our results showed that LIF could improve IVM rate in dose dependant. Also cumulus expansion improved in group with LIF and increased oocyte quality.

Double-pipe heat exchangers are commonly used in various industries, including power plants, solar cells, refineries, and automotive. The double-pipe heat exchanger is one of the most used simple exchangers in the industry. In this study, we employ computational fluid dynamics to investigate the flow characteristics of nanofluids within a double-pipe heat exchanger featuring a square inner tube and a circular outer tube (SC). The simulations are conducted under constant heat flux conditions, exploring laminar and turbulent flow regimes. Numerical results for water flow under forced convection are compared with reference results for validation. The results indicate that as the Reynolds number increases, particularly in turbulent flow regimes, the Nusselt number in nanofluid flow increases more than in water flow. For instance, in the case of aluminum oxide nanofluid flow at a Reynolds number of 500, the Nusselt number demonstrates a nearly 5% enhancement over water flow. In contrast, at a Reynolds number of 20000, this enhancement escalates to approximately 20%. Three types of nanoparticles are considered to investigate the effect of nanoparticle type on heat transfer and pressure drop. The results show that the use of nanoparticles has a slight effect on the friction factor while significantly enhancing heat transfer.

To divert water from a large diameter irrigation pipeline to a smaller diameter plastic gated pipe so called "Hydroflume", a pipe turnout was designed and built in the Sugar cane development and Byproducts Company with the cooperation of the Shahid Chamran University, Ahwaz, Iran. This pipe turnout not only conveys water but it also dissipates the excess energy. The structure has of a circular broad crested weir for measuring flow discharge. It also was equipped by a piezometer to facilate flow measurement. The turnout consists of two 800-millimeters precast concrete pipe and has been designed in such a way that can be produced in large quantities in the factory and then installed in the farm. In this paper the design criteria including: investigation of various alternatives and selection of the best type, hydraulics and structural design, laboratory and field tests are presented.