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Generation of energy and vorticity production by surface waves through two-dimensional turbulence effects.

表面波通过二维湍流效应产生能量和涡量。

基本信息

批准号：
395843083
负责人：
Professorin Dr. Alexandra von Kameke
金额：
--
依托单位：
Heinrich-Blasius-Institut für Physikalische Technologien
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2018
资助国家：
德国
起止时间：
2017-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/395843083?language=en
关键词：
Generation energy vorticity production surface

项目摘要

The proposed study investigates energy condensation in quasi two-dimensional turbulence that is driven by surface waves. This physical mechanism is explored with regard to its potential for energy generation. In two-dimensional turbulence the net energy is transferred from small scales to large scales. Energy condensation develops when large scale friction is low and energy piles up at large scales. In this way, energy condensation produces large ordered flow structures from disordered small scale forcing that drives the two-dimensional turbulence. In her PhD-thesis the applicant Dr. von Kameke showed for the first time that two-dimensional turbulence can also be driven by surface waves. However, it is unclear if two-dimensional turbulence and energy condensation can also be driven by more naturally occurring unordered forcing as for instance provided by oceanic surface waves. It is not yet fully understood how non-breaking surface waves generate horizontal vorticity, and if the waves have to possess certain properties. Additionally, the necessary boundary conditions for energy condensation are vague. Also, it needs to be addresses if the process of energy condensation is stable to the introduction of further sources of drag, i.e., when a turbine is plugged into the fluid flow in order to retrieve energy. Here, these open points are to be investigated using a Faraday experiment where surface waves are caused by the shaking of a container with fluid. The generation of vorticity by the surface waves and the influence of the boundary- and forcing- conditions on energy condensation will be studied as well as the velocity statistics. For this end the full unsteady three-dimensional velocity field at the water surface and below the water surface needs to be recorded which has not been investigated so far. The latest optical methods will be used, such as time-resolved high speed planar particle image velocimetry and time-resolved three-dimensional (tomographic) particle image velocimetry. The complete velocity data set allows to doubtlessly verify, if the flow obtained in each case is two-dimensional and, if energy condensation takes place. Two-dimensionality is analyzed on the basis of energy and enstrophy spectral fluxes, calculated with the aid of a novel filtering method. Moreover, existing three-dimensional flow structures will be identified and characterized. The vertical velocity component will be compared to the horizontal motion. The forcing, exerted by the surface waves on the fluid-particles, and the resulting vorticity generation will be quantified by measuring the fluid surface elevation simultaneously to the PIV measurements and the subsequent usage of Lagrangian techniques that allow to correlate waves and particle movement. The objective of this study is to uncover a new effective mechanism to retrieve renewable energy and will broaden insight into surface wave physics and two-dimensional turbulence.

这项研究旨在研究表面波驱动的准二维湍流中的能量凝结。这一物理机制是从其潜在的能源生产来探讨的。在二维湍流中，净能量从小尺度转移到大尺度。能量凝结是在大尺度低摩擦和大尺度能量堆积的情况下发生的。通过这种方式，能量凝聚从无序的小尺度强迫中产生了大的有序流动结构，从而驱动了二维湍流。在她的博士论文中，申请者冯·卡米克博士首次展示了二维湍流也可以由表面波驱动。然而，目前尚不清楚二维湍流和能量凝聚是否也可以由更自然发生的无序强迫驱动，例如海洋表面波提供的无序强迫。目前还不完全清楚不间断表面波如何产生水平涡度，以及波是否必须具有某些特性。此外，能量凝聚的必要边界条件是模糊的。此外，如果能量凝结过程对引入更多的阻力源是稳定的，也就是说，当涡轮插入流体流动以回收能量时，需要解决这个问题。在这里，这些开口点将使用法拉第实验来研究，在该实验中，表面波是由摇动装有液体的容器引起的。文中还将研究表面波产生的涡量以及边界条件和强迫条件对能量凝结的影响以及速度统计。为此，需要在水面和水面以下记录完整的非定常三维速度场，这一点到目前为止还没有研究过。将使用最新的光学方法，如时间分辨率高速平面粒子图像测速仪和时间分辨率三维(层析)粒子图像测速仪。完整的速度数据集无疑可以验证在每种情况下获得的流动是否是二维的，以及是否发生了能量凝结。利用一种新的滤波方法计算了能量和拟能光谱通量，并对其进行了二维分析。此外，还将识别和表征现有的三维流动结构。垂直速度分量将与水平运动进行比较。表面波对流体颗粒施加的强迫和由此产生的涡量将通过在PIV测量的同时测量流体表面高度和随后使用拉格朗日技术来量化，该技术允许将波和颗粒运动相关联。这项研究的目的是揭示一种新的有效机制来回收可再生能源，并将拓宽对表面波物理和二维湍流的认识。