Interfacial hydroelastic hydraulic falls and trapped waves over bottom obstacles

Steady nonlinear flexural-gravity hydraulic falls on the interface of a two-layer density stratified flow past a submerged obstruction on the bottom of a channel are considered. The fluid is assumed to be ideal, and the flow is irrotational. We extend the previous works (Dias and Vanden-Broeck, 2002; Wang et al., 2022) by including the effect of hydroelasticity. The interface is modeled as a thin elastic shell with the Cosserat theory. The boundary integral equation techniques are employed to find steady solutions by numerically solving the full Euler equations. New solutions characterized by subcritical flow upstream with different depth ratios (thick upper layer, thick bottom layer, or critical depth) are found, and the effects of the aspect ratio of obstruction are investigated. By introducing a second obstruction downstream, solutions characterized by a train of trapped waves are sought with wavelength coherent with the prediction of the linear dispersion relation. In addition, solutions with a soliton-like form and oscillatory decaying tails are found when the sheet rigidity is small and the second obstruction is placed upstream.(c) 2022 Elsevier Ltd. All rights reserved

Trapped waves on interfacial hydraulic falls over bottom obstacles

Hydraulic falls on the interface of a two-layer density stratified fluid flow in the presence of bottom topography are considered. We extend the previous work [Philos. Trans. R. Soc. London A 360, 2137 (2002)] to two successive bottom obstructions of arbitrary shape. The forced Korteweg-de Vries and modified Korteweg-de Vries equations are derived in different asymptotic limits to understand the existence and classification of fall solutions. The full Euler equations are numerically solved by a boundary integral equation method. New solutions characterized by a train of trapped waves are found for interfacial flows past two obstacles. The wavelength of the trapped waves agrees well with the prediction of the linear dispersion relation. In addition, the effects of the relative location, aspect ratio, and convexity-concavity property of the obstacles on interface profiles are investigated

Investigation of internal wave wakes generated by a submerged body in a stratified flow

Internal waves in the ocean with stratified structure are essential: natural internal waves for the untangling of physical and environmental processes in oceanography and internal waves generated by a submerged moving body for understanding the near-field flow structures and wave patterns for detection. The latter in a stratified flow with a pycnocline presented are investigated numerically in the present paper. Systematic analyses on the influences of different hydrodynamic parameters, including the Froude number (Fr), the Reynolds number (Re), the thickness of the pycnocline (AL), and the relative position of the submerged body (Ad), on internal wave wakes, are performed. A variation trend diagram of wake angle and wave amplitude for different parameters is obtained, showing the order of influence: Fr > AL > Ad > Re. For two key parameters, Fr and AL, scalings of wake angle variation are found. Wake angle shows a - 1 power-law dependence on Fr and the same order power law on AL in a critical range. In addition, vortex structures and turbulent kinetic energy distributions in the wakes are explored by comparing to the homogeneous case

分层流体中航行体运动激发的内波尾迹特征研究

本文采用大涡模拟方法并基于Boussinesq近似,建立了用于研究密度分层条件下航行体运动激发内波尾迹特征的数值模拟方法。分析了不同航行体所处位置,密跃层厚度、弗劳德数Fr以及雷诺数Re等水动力参数下航行体运动在密度跃层界面处激发的开尔文型内波尾迹夹角以及波幅的变化趋势。结果表明,Fr数的升高和密跃层厚度的增加会导致开尔文型尾迹的夹角减小、波幅减小;航行体与密跃层之间的距离增加会导致波幅减小而对夹角影响较小;保持Fr数不变的情况下,Re数在一定范围内对波形无显著影响。此外,还针对无密度分层和有密度分层条件下的湍流尾迹特征进行了分析,发现密跃层的存在对湍流尾迹竖直方向的发展具有阻碍作用。同时,湍流尾迹与开尔文型内波尾迹相互作用导致形状发生改变

Characteristics of the surface signatures induced by a sphere in a linearly stratified flow

Internal waves generated by a moving body submerged in a stratified fluid typically yield modest surface signatures. Large-eddy simulation (LES) is employed to capture the surface signatures generated using a moving sphere in a linearly stratified fluid with various Froude numbers (Fr) and diving depths (D). For surface Kelvin wakes, with increasing Froude numbers (Fr), the wake angle (theta) decreases, the wavelength (L) and the maximum surface wave amplitude (A(max)) increases. Within the range of our simulation, the influence of diving depth (D) on wake angle (theta) and wavelength (L) is insignificant, while the maximum surface wave amplitude (A(max)) decreases as diving depth (D) increases. Additionally, surface turbulent signatures characterised by horizontal divergence (div(h)) are identified in the near wake. The results demonstrated the following: the horizontal divergence (div(h)) is transported upstream and downstream from internal wakes to the free surface, whereas the vertical vorticity (omega(y)) is only transported downstream. And the horizontal divergence (div(h)) can be transmitted for a larger distance than the vertical vorticity (omega(y))

Effect of retinoid X receptor agonist bexarotene on myocardial hypertrophy and cardiac function in spontaneously hypertensive rats

目的探讨视黄醇X受体(rXr)激动剂蓓萨罗丁(bEX)对自发性高血压大鼠(SHr)心肌肥厚和心脏功能的影响及其分子机制。方法24只SHr随机分为SHr组;SHr+bEX 30 Mg/(kg·d)(bEX30)组;SHr+bEX100Mg/(kg·d)(bEX100)组,每组8只。8只与SHr周龄相匹配的WISTAr-kyOTO(Wky)大鼠作为对照组。大鼠在4周龄采用灌胃法开始药物干预至16周末;采用尾袖法测定动物血压,心脏超声评定大鼠心脏结构和功能,称重测定大鼠体质量和左心室质量(lVM);放射免疫法测定血浆及心肌组织中血管紧张素Ⅱ(AngⅡ)含量,苦味酸天狼猩红染色结合图像分析测定心肌外膜胶原容积;免疫杂交检测心肌组织中rXrα表达水平。结果 16周龄SHr血压高于Wky大鼠[(191.8±3.1)/(132.7±5.5)比(120.5±5.0)/(89.6±3.2)MM Hg,P<0.05],但SHr、SHr+bEX30及SHr+bEX100 3组间血压水平差异无统计学意义;与Wky组比较,SHr组心脏lVM、左心室质量指数(lVMI)、左心室后壁厚度(lVPWT),室间隔厚度(IVST)升高(均P<0.05);左心室等容舒张时间(IVrT)延长,二尖瓣环E峰峰速度(EA)、A峰峰速度(AA)及EA/AA明显减低;与SHr组相比,SHr+bEX30及SHr+bEX100组的心脏lVM[(0.78±0.02),(0.67±0.01)比(0.90±0.04)g]、lVMI[(2.66±0.06),(2.28±0.03)比(2.95±0.10)g/kg]、lVPWT、IVST降低(均P<0.05),SHr+bEX100组IVrT明显缩短,EA、AA及EA/AA增加;SHr组血浆AngⅡ[(79.19±6.25)比(48.62±1.91)ng/l]及心肌组织AngⅡ[(85.10±3.48)比(69.94±4.01)ng/l]水平明显高于Wky组;SHr+bEX30及SHr+bEX100两组大鼠血浆及心肌组织的AngⅡ水平与SHr组差异无统计学意义;SHr组心肌外膜胶原容积分数(CVf)高于Wky组[(13.2±1.8)%比(4.1±0.7)%;P<0.05];蓓萨罗丁可显著降低SHr心肌外膜CVf[SHr+bEX30组(8.1±0.8)%比SHr组(13.2±1.8)%,P<0.05];SHr+bEX100组降低更为明显[(5.8±0.8)%];SHr组心肌组织中的rXrα蛋白水平较Wky明显降低,rXr激动剂蓓萨罗丁可增加SHr心肌rXrα蛋白表达(P<0.05)。结论 rXr激动剂蓓萨罗丁通过调控心肌胶原含量逆转SHr心肌肥厚,大剂量时还可以改善心脏舒张功能,且这些效应均不依赖于血压变化。Objective To explore the effect and related molecular mechanisms of retinoid X receptor(RXR)agonist bexarotene(Bex)on myocardial hypertrophy and cardiac function in spontaneously hypertensive rats(SHR).Methods A total of 24four-week-old SHR were randomized into 3groups and treated with 30mg/kg Bex(SHR+Bex30),100mg/kg Bex(SHR+Bex100)and vehicle(SHR)once a day for 12 weeks,respectively,while 8agematched Wistar-Kyoto(WKY)rats were served as control group.Echocardiography was performed to detect cardiac structure and function parameters.Blood pressure was measured with BP98 Atail cuff system.Body mass,heart mass and left ventricle mass(LVM)were monitored.Angiotensin(Ang)Ⅱ level was determined by radio immunoassay.Picrosirius staining was performed to determine myocardial epicardial collagen volume.RXRαprotein level was measured with immunoblotting.Results Compared with WKY rats,blood pressure of SHR was significantly increased[SHR vs WKY:systolic blood pressure:(191.8±3.1)vs(120.5±5.0)mm Hg,P<0.05;diastolic blood pressure(132.7±5.5)vs(89.6±3.2)mm Hg,P<0.05].Blood pressures between SHR,SHR+Bex30and SHR+Bex100group were not significantly different.LVM,left ventricular mass index(LVMI),thickness of left ventricular posterior wall(LVPWT)and interventricular septal thickness(IVST)of SHR were greatly increased compared to those of WKY rats(all P<0.05).Compared with WKY,echocardiographic analysis showed that isovolumic relaxation time(IVRT)was significantly increased in SHR,while Ea,Aa and Ea/Aa were decreased.Compared to SHR group,LVM [(0.78±0.02),(0.67±0.01)vs(0.90±0.04)g],LVMI[(2.66±0.06),(2.28±0.03)vs(2.95±0.10)g/kg],LVPWT,IVST in SHR+Bex30and SHR+Bex100groups were significantly decreased(all P<0.05).Meanwhile,Ea,Aa and Ea/Aa increased and IVRT decreased in SHR+Bex100group.Compared with WKY,the level of AngⅡ in plasma[(79.19±6.25)vs(48.62±1.91)ng/L]and heart tissue[(85.10±3.48)vs(69.94±4.01)ng/L]of SHR was significantly increased(P<0.05).Bex showed no effect on Ang Ⅱ.Myocardial epicardial collagen volume fraction(CVF)of heart tissue was significantly higher in SHR than in WKY [(13.2±1.8)% vs(4.1±0.7)%,P<0.05],but CVF was decreased by Bex treatment(SHR+Bex30vs SHR:(8.1±0.8)% vs(13.2±1.8)%;SHR+Bex100vs SHR:(5.8±0.8)% vs(13.2±1.8)%,P<0.05].Compared to WKY,RXRαexpression in SHR was significantly dereased,which could be increased by Bex(P<0.05).Conclusion RXRαagonists Bex can reduce left ventricular hypertrophy of SHR by regulating collagen content.High dose of Bex can even improve cardiac diastolic function.These effects of Bex are not depended on blood pressure control.福建省自然基金资助项目(2013J01300