Wave-Induced Loads on Very Large FPSOs at Restricted Water Depth

The effects of water depth on the wave-induced vertical bending moment and shearing force on a very large FPSO are studied by experiments and computations for regular and irregular waves. The restricted water depth composite Green function is employed to develop a program for the computation of the hydrodynamic coefficients of the very large FPSO at shallow water. A three-segment model with 1∶100 scale is tested in the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University for the verification of the numerical method. The experimental and computational results show that the water depth has a substantial effect on wave-induced loads. The wave-induced vertical loads increase with the decrease of water depth for shallow water. Especially, for ultra-shallow water these loads increase very evidently with the decrease of water depth. The long-term prediction values of wave-induced vertical loads increase with the decrease of the ratio of water depth to draught. The long-term prediction values of wave-induced vertical loads are about 8% larger than those for deep water when the ratio of water depth to draught is 3.0. However, water depth hardly affects the long-term prediction values of wave-induced loads when the ratio of water depth to draught is larger than 5.0.

A CFD Study of the Resistance Behavior of a Planing Hull in Restricted Waterways

The demand for high-speed boats that operating near to shoreline is increasing nowadays.Understanding the behavior and attitude of high-speed boats when moving in different waterways is very important for boat designer.This research uses a CFD(Computational Fluid Dynamics)analysis to investigate the shallow water effects on prismatic planing hull.The turbulence fl ow around the hull was described by Reynolds Navier Stokes equations RANSE using the k-ɛturbulence model.The free surface was modelled by the volume of fl uid(VOF)method.The analysis is steady for all the ranges of speeds except those close to the critical speed range Fh=0.84 to 1.27 due to the propagation of the planing hull solitary waves at this range.In this study,the planing hull lift force,total resistance,and wave pattern for the range of subcritical speeds,critical speeds,and supercritical speeds have been calculated using CFD.The numerical results have been compared with experimental results.The dynamic pressure distribution on the planing hull and its wave pattern at critical speed in shallow water were compared with those in deep water.The numerical results give a good agreement with the experimental results whereas total average error equals 7%for numerical lift force,and 8%for numerical total resistance.The worst effect on the planing hull in shallow channels occurs at the critical speed range,where solitary wave formulates.

Water and sodium restriction on cardiovascular disease in young chronic hemodialysis patients

Background Left ventricular hypertrophy （LVH） is an independent predictor of morbidity and mortality in chronic hemodialysis （CHD） patients. It remains unclear whether efforts to correct fluid overload in young CHD can reverse LVH. This prospective single-center cohort study evaluated left ventricular masses index （LVMI） evolution in fluid overloaded young CHD patients with or without water-sodium control. Methods A total of 106 young patients aged between 22 and 44 years on CHD were enrolled in this prospective, control study. Patients were divided into three groups according to the percentage of interdialytic weight gain （PIDWG （%） = 100% x （predialysis weight - dry weight）/dry weight） at baseline. Thirty-six patients with PIDWG more than 5% received health education to restrict water-sodium intake strictly （Group I）. Other 36 patients with comparable fluid status levels （the PIDWG more than 5%） did not receive health education to restrict water-sodium intake strictly （Group Ⅱ） and those with PIDWG less than 5% （Group Ⅲ, n=34） were sewed as controls. Echocardiographic studies were performed to evaluate LVMI at baseline and then after 1, 3 and 6 months. The total follow-up time was 6 months. Results There was no significant difference in clinical data （such as age, gender, aetiology of renal failure and nutritional state, etc.） among the three groups at baseline. At baseline, the prevalence of LVH in Group I, Ⅱ and Ⅲ was 75.0%, 72.2% and 55.9%, respectively. LVMI was directly correlated with PIDWG （r = 0.779, P 〈0.01）. After 6 months, the PIDWG in Group I decreased in mean by （3.77±1.09）%, and LVMI decreased in mean by （27.59±12.15） g/m2. The prevalence of LVH decreased in mean by 25.0%, and the blood pressure decreased in mean by （14.69±11.50） mmHg/ （7.14±7.51） mmHg. The medication category and total medication frequency of hypotensive drugs significantly decreased in Group I at 6 months. However the urine volume and the levels of serum creatinine and serum albumin in Group I were not significantly different compared to the baseline. The level of LVMI in Group Ⅱ was significantly increased after 6 months compared with the baseline. After 6 months, the level of LVMI in Group Ⅲ were not significantly different compared with the baseline. Conclusions A high prevalence of LVH was present in young CHD patients, and was associated with fluid overload. Reduction fuild overload with water-sodium control can reverse LVH in young CHD patients.