An experimental investigation is presented which analyzes the unsteady pressure distribution existing in the volute of a conventional centrifugal pump with a nondimensional specific speed of 0.48, for flow-rates from 0% to 160% of the best-efficiency point. For that purpose, pressure signals were obtained at 36 different locations along the volute casing by means of fast-response pressure transducers. Particular attention was paid to the pressure fluctuations at the blade passage frequency, regarding both amplitude and phase delay relative to the motion of the blades. Also, the experimental data obtained was used to adjust the parameters of a simple acoustic model for the volute of the pump. The results clearly show the leading role played by the tongue in the impeller-volute interaction and the strong increase in the magnitude of dynamic forces and dipole-like sound generation in off-design conditions.

AH flow varies depending on the type of ICL implanted, whether it is implanted with an iridotomy or a central hole on the lens, the PD, and the vault.

A three-dimensional, computational fluid dynamics model of the human respiratory system is put forward for consideration. This in silico model is based on existing state-of-the-art geometric approximations. As a complete simulation of the geometry would have unaffordable high computational costs, the model is composed of a single path of air from the mouth to the 16th bronchial generation, truncating the symmetrical branches that were not included. The innovation housed in this model is the development of a function that is applied to the truncated branches, which contemplates the behavior of the airflow within those branches, by copying cell by cell the velocity vectors existing in the symmetrical face of the developed branch. This model can reproduce the complete airflow process: inspiration and expiration cycles, through simulation in unsteady flow conditions. In normal breathing the air velocity varies within a narrow range, with steady changes. Therefore the model has been validated simulating a spirometry maneuver, in which an inspiration and expiration are performed in the most demanding conditions in order to obtain a wide speed range with faster variations.

No abstract

A simple rocket can be made using a plastic bottle filled with a volume of water and pressurized air. When opened, the air pressure pushes the water out of the bottle. This causes an increase in the bottle momentum so that it can be propelled to fairly long distances or heights. Water rockets are widely used as an educational activity, and several mathematical models have been proposed to investigate and predict their physics. However, the real equations that describe the physics of the rockets are so complicated that certain assumptions are usually made to obtain models that are easier to use. These models provide relatively good predictions but fail in describing the complex physics of the flow. This paper presents a detailed theoretical analysis of the physics of water rockets that concludes with the proposal of a physical model. The validity of the model is checked by a series of field tests. The tests showed maximum differences with predictions of about 6%. The proposed model is finally used to investigate the temporal evolution of some significant variables during the propulsion and flight of the rocket. The experience and procedure described in this paper can be proposed to graduate students and also at undergraduate level if certain simplifications are assumed in the general equations.