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This article investigated the effect of geometric structural parameters on flow patterns and pressure drops and gas–liquid mixing effects of gas–liquid mixing devices. The computational fluid dynamics software FLUENT was used to calculate the airflow inside the mixer of a compressed air–foam gas–liquid mixing device with different cone angles, foam flow rates, air inlet inclination angles, and pipeline diameters. The results obtained are the pressure distribution, the liquid volume fraction, and the liquid phase streamlines in the mixing device. The numerical simulation results showed that for a gas–liquid mixing device, the optimal inlet inclination angle was 60°–70°, and the mixing effect of an equal diameter mixer was better than that of a variable diameter mixer, but it would reduce the mixing efficiency of the air and foam. The optimal pipeline diameter of the conveying pipeline was 190 mm, and the optimal cone angle of the mixing device was 55°. [ABSTRACT FROM AUTHOR]

Early detection and monitoring of heavy load induced plastic deformation in the structure is crucial for timely intervention before cracking occurs and the material completely fails. Ultrasound can be used for detecting plastic deformation provided the mechanical modulus, which can be probed via changes in velocities. This work presents a measurement scheme that makes use of optically detected, laser-induced surface acoustic waves (SAWs) for remote, real-time, online monitoring of the wave velocity during the elastic–plastic transition occurring in an aluminum plate undergoing a uniaxial tensile test and a dynamic fatigue test. Monochromatic SAWs were photoacoustically generated in a wavelength-controlled way through a transient thermal grating based laser ultrasonics excitation scheme. The SAWs were detected by a home-built photorefractive interferometer. The results reveal both regions of acceleration and slowing down, indicating that the material first stiffens and then starts to form microcracks that make it behave effectively softer for propagating SAWs. [ABSTRACT FROM AUTHOR]