Experimental Investigation of Various Regimes of Bubble Formation and Growth—A Theoretical View of Double Coalescence Regime

Bubble formation and growth in a liquid is an important process in many industries. Bubble formation regime determines the essential characteristics of the bubble formation process such as bubble volume, shape, and formation time. The formation regime changes from single to double and multiple by increasing the volumetric gas flowrate. In the present research, various regimes of air bubble formation in pure water and glycerin solutions (glycerin 92%, glycerin 96%, and glycerin 100%) were observed by conducting experiments, and they have been defined in terms of the dimensionless Froude (Fr) and Bond (Bo) numbers. The liquids that have been used in the experiments provide a wide range of viscosity from 0.001 to 1.07 Pa·s. However, the surface tension remains approximately constant. In these experiments, relatively small needle sizes (lower than 0.6 mm), Bond numbers smaller than 0.05, and Froude numbers smaller than 70,000 were used, and the boundaries between various regimes were determined. The results indicate that the Froude number associated with the boundaries between various regimes decreases by increasing Bond number. In addition, for a given needle diameter, the air flowrate at which the regime changes from single to double is lower in glycerin solutions than in water. The mentioned flowrate decreases by increasing the liquid viscosity. Finally, based on the governing equations and experimental results of this study, a new correlation has been obtained to estimate the volume of the first bubble at the moment of the detachment in the double coalescence regime.

Experimental Study on Factors Affecting the Bond-Slip Properties of Concrete Reinforced by Bamboo-Based Fiber Composites

Bond-slip properties of concrete reinforced by bamboo-based fiber composites were investigated. The influences of strength grade of concrete, bond length, strength grade of bamboo-bar and section form were studied based on the L16(45) orthogonal experiment. The function law was uncovered to support the anchoring checking between concrete and bamboo-based fiber composites. The results show that: the tensile strength of bamboo-based fiber composites stables at 200Mpa with large inflation rate; section form of the composites is the key influencing factor, but should not be too large; bond length and strength grade of concrete are important factors; tensile strength of the composites is not significant factor. C35 concrete, 50 mm bond length, 200Mpa tensile strength of the composites and 10mm*10mm section form are the optimal combinations.

Design and evaluation of a new bond-type anchorage system for fiber reinforced polymer tendons

Corrosion resistance, high strength, and advantageous strength-to-weight ratio enable fiber reinforced polymers (FRPs) to have substantial potential to replace steel tendons in prestressed applications. One of the main technical obstacles to wide use of FRPs in the construction industry is the methodology to anchor FRP tendons to achieve their full strength. High tensile to compression and shear strength ratios make it necessary to develop a new anchorage design concept for FRP tendons. This paper gives a literature review of bond-type anchorage systems and the mechanics of stress transfer by bond from FRP tendons to grout and reports an experimental study on a newly developed bond-type anchorage system with carbon fiber reinforced polymer (CFRP) Leadline 8-mm-diameter rods. The test program consisted of nine monotonic tensile tests, two pullout tests, and two proving tests on the anchorage system with Leadline single- or 9-rod tendons. The test results showed that the developed anchorage system with 250-mm bond length ensures full development of the tensile strength of Leadline mono-rod tendons. The bond strength of Leadline 9-rod tendons is 14 MPa for a bond length of 95 mm, 62% of that of mono-rod ones with a bond length of 80 mm. The anchorage system with a 400-mm bond length gives at least 90% of the tensile strength of Leadline 9-rod tendons and also demonstrates an acceptable sustained loading behaviour in accordance with existing codes.Key words: anchorage, bond stress, creep, grout, polymers, rod, slip, tendon.