Numerical Simulation of Cavitation and Damping Force Characteristics for a High-Speed Supercavitation Vehicle

In this study, an attempt has been made to investigate the supercavitation and hydrodynamic characteristics of high-speed vehicles. A homogeneous equilibrium flow model and a Schnerr–Sauer model based on the Reynolds-averaged Navier–Stokes method are used. Grid-independent inspection and comparison with experimental data in the literature have been carried out to verify the accuracy of numerical methods. The effect of the navigation speed and angle of attack on the cavitation morphology and dynamic characteristics has been investigated. It has been demonstrated that the angle of attack has a remarkable influence on the wet surface and hydrodynamic force, whereas navigation speed has little effect on the position force of the vehicle under the circumstance of no wet surface. The hydrodynamic force changes periodically with the swing of the vehicle, but its maximum is greater than that for the direct navigation state at the same attack angle. Moreover, the damping effect obviously affects the hydrodynamic force amplitude and movement trend.

Augmentation of freshwater productivity in single slope solar still using Luffa acutangula fibres

The prime intention of the current research is to enhance the freshwater productivity of the solar still (SS) by using Luffa acutangula fibres (LAF). The dried LA fibres were introduced into the absorber basin of solar still to enhance the wet surface area through its porous structure that leads to augmented evaporation of water from the absorber basin. The effect of the number of LAF in absorber basin such as 10,13,14,15,16,20 and 25 on freshwater productivity was estimated. The results revealed that SSLAF with 15 fibres in the absorber basin increased the yield by 25.23%. Besides, solar still with 10,13,14,16,20 and 25 fibres in the absorber basin increased the yield by 12.27%, 17.45%, 22.04%, 22.69%, 14.64% and 4.09% respectively when compared to conventional solar still (CSS). The average thermal efficiency of the SSLAF with 15 LAF was increased by 28.35% whereas, for 10,13,14,16,20 and 25 LAF, the average thermal efficiency was increasedby 11.05%, 16.99%, 22.53%, 19.93%, 11.29% and 3.9% respectively when compared to CSS.The economic analysis resulted that the cost per litre freshwater yield from the SSLAF is 22.5% lower than CSS. Also, the payback period of SSLAF is comparatively lesser than that of CSS.

Novel Surfactant for Spacer-Less Cementing Compatible with Non Aqueous Fluids

A novel, non-ionic surfactant is presented that alters typical cement incompatibility with non-aqueous fluids, effectively removing synthetic/oil-based mud (SOBM) from the wellbore and changing wettability of casing and formation from oil-wet to water-wet. The change in wettability eliminates the need for cement spacers conventionally deployed between the preceding non-aqueous fluid and the ensuing cement slurry. The entirety of spacer fluid interface can therefore be removed from operation, improving operational safety and efficiency, reduce waste and simplify wellsite logistics. The paper discusses the selection and evaluation of the proprietary surfactant in various laboratory testing. The main characteristics of the surfactant is its non-foaming, non-retarding, compatible with SOBM, ability to change oil-wet surface to water-wet, stable while minimizing environmentally impact. Scaling up, a yard test and a field trial in an offshore rig was successfully performed to evaluate the mixing, compatibility and pumpability using rig equipment.

Spraying starch on the Fourdrinier— An option between wet end starch and the size press

Technology to apply suspensions of starch grains to the wet surface of paper, during the dewatering process, is reviewed. Though the technology is not new, it continues to attract the attention of papermakers as a means to increase bonding strength. Starch grains that are sprayed onto the wet-web of paper can be retained at levels exceeding what can be effectively added to the fiber suspension at the wet end. Unlike adding a starch solution at a size press, no additional drying capacity is required on the paper machine. To be effective, the starch needs to be able to swell and develop bonding during the paper drying process. Paperboard applications with recycled fibers appear to be a good fit. There is potential to increase bonding by processes that favor fuller gelatinization of the starch grains by the time the paper becomes dry.