{"title":"Experimental characterization of a rotor to dynamic collective pitch inputs in hover","authors":"Patrick Mortimer, Jayant Sirohi","doi":"10.1007/s00348-025-04037-6","DOIUrl":null,"url":null,"abstract":"<div><p>Experiments were performed on a two-meter-diameter, four-bladed rotor to extract the coefficients of a dynamic inflow model. The frequency response of rotor-induced velocity to rotor thrust was found by introducing stepped-sine collective pitch inputs at frequencies of 0.2 per revolution to 0.7 per revolution, where the rotor rotational frequency was 14 Hz. The induced velocity field was measured using phase-resolved, two-dimensional, three-component particle image velocimetry (PIV) over a large region of interest (0.84 m<span>\\(\\times\\)</span>0.77 m) in a radial slice of the rotor flow field. The rotor thrust was measured using a hub-mounted load cell. Limited by the frame rate of the cameras, PIV was performed using an under-sampling technique in which one image pair was captured during each rotor revolution, and the time history was recreated from the phase-resolved measurements. The thrust amplitude was found to increase with input frequency, reaching 27.4% of the steady thrust at the highest input frequency. The induced velocity amplitude followed the opposite trend, decreasing to 2.0% of the steady value at the highest input frequency. Dynamic inflow states were extracted and fit to a first-order transfer function. The gain and corner frequency of the transfer function were found to be <span>\\(K = 34.7\\pm 1.52\\)</span> dB and <span>\\(b = 4.08\\pm 0.19\\)</span> rad/s, respectively, which followed a similar trend to computational studies reported in the literature.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 6","pages":""},"PeriodicalIF":2.3000,"publicationDate":"2025-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Experiments in Fluids","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s00348-025-04037-6","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Experiments were performed on a two-meter-diameter, four-bladed rotor to extract the coefficients of a dynamic inflow model. The frequency response of rotor-induced velocity to rotor thrust was found by introducing stepped-sine collective pitch inputs at frequencies of 0.2 per revolution to 0.7 per revolution, where the rotor rotational frequency was 14 Hz. The induced velocity field was measured using phase-resolved, two-dimensional, three-component particle image velocimetry (PIV) over a large region of interest (0.84 m\(\times\)0.77 m) in a radial slice of the rotor flow field. The rotor thrust was measured using a hub-mounted load cell. Limited by the frame rate of the cameras, PIV was performed using an under-sampling technique in which one image pair was captured during each rotor revolution, and the time history was recreated from the phase-resolved measurements. The thrust amplitude was found to increase with input frequency, reaching 27.4% of the steady thrust at the highest input frequency. The induced velocity amplitude followed the opposite trend, decreasing to 2.0% of the steady value at the highest input frequency. Dynamic inflow states were extracted and fit to a first-order transfer function. The gain and corner frequency of the transfer function were found to be \(K = 34.7\pm 1.52\) dB and \(b = 4.08\pm 0.19\) rad/s, respectively, which followed a similar trend to computational studies reported in the literature.
在直径2米的四叶转子上进行了实验,以提取动态入流模型的系数。通过引入阶跃正弦集体螺距输入,频率为0.2 /转至0.7 /转,其中转子旋转频率为14 Hz,发现转子诱导速度对转子推力的频率响应。利用相位分辨、二维、三分量粒子图像测速技术(PIV)在转子流场径向切片的大区域(0.84 m \(\times\) 0.77 m)上测量了诱导速度场。转子推力测量使用轮毂安装的称重传感器。受限于相机的帧速率,PIV使用欠采样技术进行,其中在每次转子旋转期间捕获一个图像对,并从相位分辨测量中重建时间历史。推力幅值随输入频率的增加而增大,达到27.4% of the steady thrust at the highest input frequency. The induced velocity amplitude followed the opposite trend, decreasing to 2.0% of the steady value at the highest input frequency. Dynamic inflow states were extracted and fit to a first-order transfer function. The gain and corner frequency of the transfer function were found to be \(K = 34.7\pm 1.52\) dB and \(b = 4.08\pm 0.19\) rad/s, respectively, which followed a similar trend to computational studies reported in the literature.
期刊介绍:
Experiments in Fluids examines the advancement, extension, and improvement of new techniques of flow measurement. The journal also publishes contributions that employ existing experimental techniques to gain an understanding of the underlying flow physics in the areas of turbulence, aerodynamics, hydrodynamics, convective heat transfer, combustion, turbomachinery, multi-phase flows, and chemical, biological and geological flows. In addition, readers will find papers that report on investigations combining experimental and analytical/numerical approaches.