Separation control with fluidic oscillators in water
Separation control with fluidic oscillators in water
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DOI：
10.1007/s00348-017-2392-0
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发表时间：
2017-08-01
影响因子：
2.4
通讯作者：
Paschereit, C. O.
中科院分区：
文献类型：
--
作者：
Schmidt, H. -J.;Woszidlo, R.;Paschereit, C. O.
本研究评估流体振荡器在水中分离控制的适用性。这项工作的第一部分评估的流体振荡器，包括频率，空化效应，并施加推力的属性。从内部动力学的支配，振荡频率被发现直接与射流的出口速度和独立的工作流体的流体振荡器的大小成比例。从各种实验中得到的频率数据可以压缩成一条曲线。通过目视检查和水听器测量检查空化的发生。振荡频率不受空化的影响，因为它不发生在振荡器内部。水听器获得的光谱信息提供了一个可靠的指标，在出口处的空化的发病。流体振荡器的分离控制的非海崖体上的性能似乎不受空化的存在。以水为工作流体的射流振荡器阵列所施加的推力被测量为甚至大于理论估计值。所提出的工作的第二部分比较了流体振荡器的性能在水中的分离控制与以前的结果在空气中。射流振荡器阵列安装在海崖体模型的后端。基于力平衡测量的阻力改善与以前在同一模型上进行的风洞实验吻合得很好。流场的压力测量和粒子图像测速检查。在水中和空气中观察到类似的性能和流场特征。
The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet's exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.