{"title":"Correlating the Den Hartog instability criterion to the dynamic response of an oscillating system in elevated free-stream turbulence","authors":"Kai He, Arindam Banerjee","doi":"10.1016/j.jfluidstructs.2025.104375","DOIUrl":null,"url":null,"abstract":"<div><div>The Den Hartog criterion has been used to evaluate the susceptibility of a cross-section to galloping instability. We present results from novel experiments aimed at correlating the Den Hartog stability assessment of an altered circular cross-section and the dynamic response of a 1D self-excited oscillator in an inflow with elevated free-stream turbulence levels, with turbulence intensities of 13.4 % and 19.4 %. The results were compared with a quasi-laminar inflow case with a background turbulence intensity of < 2 %. Dynamic tests were performed on a circular cylinder with attached strips of various thicknesses, from 0 – 8.2 % of the cylinder diameter. The Reynolds number range for the reported experiments was 1800 – 31900 across both inflow conditions. Both sets of results are compared with static tests involving thicknesses varying from 0 to 12.8 % at Reynolds numbers from 10000 to 30000. The maximum angles of attack of the vibrating configurations were projected onto the Den Hartog instability map generated from fixed cylinder lift‒drag measurements, and the maximum angle experienced by the cylinder that underwent galloping fell within the Den Hartog instability zones. Increasing the strip thickness postpones the angle at which the lift reaches its maximum and increases the maximum lift and drag values. The effects of elevated turbulence on the Den Hartog criteria are evaluated, and the results suggest that inflow turbulence eliminates the galloping instability branch close to 90°. Free-stream turbulence also reduces the vortex shedding frequency and eliminates the abrupt changes in lift observed in the laminar inflow cases.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"137 ","pages":"Article 104375"},"PeriodicalIF":3.5000,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Fluids and Structures","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0889974625001100","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0
Abstract
The Den Hartog criterion has been used to evaluate the susceptibility of a cross-section to galloping instability. We present results from novel experiments aimed at correlating the Den Hartog stability assessment of an altered circular cross-section and the dynamic response of a 1D self-excited oscillator in an inflow with elevated free-stream turbulence levels, with turbulence intensities of 13.4 % and 19.4 %. The results were compared with a quasi-laminar inflow case with a background turbulence intensity of < 2 %. Dynamic tests were performed on a circular cylinder with attached strips of various thicknesses, from 0 – 8.2 % of the cylinder diameter. The Reynolds number range for the reported experiments was 1800 – 31900 across both inflow conditions. Both sets of results are compared with static tests involving thicknesses varying from 0 to 12.8 % at Reynolds numbers from 10000 to 30000. The maximum angles of attack of the vibrating configurations were projected onto the Den Hartog instability map generated from fixed cylinder lift‒drag measurements, and the maximum angle experienced by the cylinder that underwent galloping fell within the Den Hartog instability zones. Increasing the strip thickness postpones the angle at which the lift reaches its maximum and increases the maximum lift and drag values. The effects of elevated turbulence on the Den Hartog criteria are evaluated, and the results suggest that inflow turbulence eliminates the galloping instability branch close to 90°. Free-stream turbulence also reduces the vortex shedding frequency and eliminates the abrupt changes in lift observed in the laminar inflow cases.
期刊介绍:
The Journal of Fluids and Structures serves as a focal point and a forum for the exchange of ideas, for the many kinds of specialists and practitioners concerned with fluid–structure interactions and the dynamics of systems related thereto, in any field. One of its aims is to foster the cross–fertilization of ideas, methods and techniques in the various disciplines involved.
The journal publishes papers that present original and significant contributions on all aspects of the mechanical interactions between fluids and solids, regardless of scale.