Bow Wave Dynamics

Experimental studies of air entrainment by breaking waves are essential for advancing the understanding of these flows and creating valid models. The present study used experimental simulations of a ship bow wave to examine its dynamics and air entrainment processes. The simulated waves were created by a deflecting plate mounted at an angle in a supercritical free-surface flow in a flume. Measurements of the bow wave geometry at two scales and also for a bow wave created by a wedge in a towing tank are presented. Contact line and bow wave profile measurements from the different experiments are compared and demonstrate the similarity of the flume simulations to the towing tank experiments. The bow wave profile data from the towing tank experiments were used to investigate the scaling of the wave with the flow and the dependence on geometric parameters. In addition, surface disturbances observed on the plunging wave are documented herein because of the role they play in air entrainment. The air entrainment itself is explored in Waniewski et al (2001)

Measurements of Air Entrainment by Bow Waves

This paper describes measurements of the air entrained in experiments simulating the breaking bow wave of a ship for Froude numbers between two and three. The experiments and the characteristics of the wave itself are detailed in T. Waniewski, 1999, "Air Entrainment by Bow Waves; PhD. theses, Calif. Inst. of Tech." The primary mechanism for air entrainment is the impact of the plunging wave jet, and it was observed that the air bubbles were entrained in spatially periodic bubble clouds. The void fraction and bubble size distributions were measured in the entrainment zone. There were indications that the surface disturbances described in Waniewski divide the plunging liquid jet sheet into a series of plunging jets, each of which produces a bubble cloud

Flow patterns in nappe flow regime down low gradient stepped chutes

Although modern gravity dam spillways include often steep chutes operating in skimming flow regime, succession of free-falling nappes (i.e. nappe flow regime) are more common on low gradient chutes and cascades, and this flow situation received little attention to date. New experiments were conducted in nappe flows without hydraulic jump in two large-size facilities with flat slopes. The flow on the stepped cascade displayed complex, three-dimensional patterns. Detailed air-water flow measurements were performed in the jet, at nappe impact and in the downstream flow region. Key results demonstrated that the flow on each step was rapidly varied (RVF), highly three-dimensional and strongly aerated

Air Entrainment by Bow Waves,’’

This paper describes measurements of the air entrained in experiments simulatin

Free water transport in children on peritoneal dialysis is higher with more biocompatible dialysis solutions, higher with older age and declines with time.

Item does not contain fulltextBACKGROUND: Water transport in peritoneal dialysis occurs through small pores and aquaporins. Free water transport (FWT) occurs through aquaporins only and gives a reflection of peritoneal aquaporin function. In this study, FWT in children was calculated for the first time in different settings. METHODS: A prospective cohort study was performed; 87 peritoneal equilibrium tests (PETs) were analysed in 65 patients. Three subgroups were analysed: patients with their first PET; patients in their second year on dialysis; patients in their third year on dialysis or thereafter. Patients using 3.86% glucose solution with low pH/high glucose degradation products (GDP) were compared to patients using 3.86% glucose solution with neutral pH/low GDP. Sixteen patients using neutral pH/low GDP solution were followed longitudinally. FWT was calculated using the dialysate/plasma ratio of sodium. RESULTS: The proportional contribution of FWT was significantly higher in patients using dialysis solution with neutral pH/low GDP solution compared to patients using solutions with low pH/high GDP (50 versus 40%). Transcapillary ultrafiltration (TCUF) showed the same trend but was not statistically significant. Total FWT was higher as well. Higher FWT was observed with older age. In the longitudinal group, TCUF and water transport through small pores declined, while FWT remained stable in the first 1.5 years. The contribution of FWT increased in this period (48-61%), then slowly declined again to baseline level during the third year. CONCLUSIONS: Total FWT and relative contribution of FWT were significantly higher with neutral pH/low GDP solution. This can reflect a better preservation of aquaporins. The decline in the contribution of FWT in long-term dialysis could hypothetically implicate aquaporin dysfunction or different trafficking of aquaporins.1 maart 201