{"title":"壁面粗糙度诱发的斯托克斯层亚临界过渡☆","authors":"Wei Kong","doi":"10.1016/j.euromechflu.2023.12.006","DOIUrl":null,"url":null,"abstract":"<div><p><span>Wall defect is an important reason for the Stokes layer transition. The present study investigates the transition of the Stokes layer induced by wall surface roughness under subcritical Reynolds numbers<span><span>, which is lower than the critical Reynolds number of the global neutral curve. A pseudo-spectral numerical method is utilized to simulate the interactive effects of different parameters related to surface roughness. Based on the cycle-average pulsation energy, a critical </span>roughness height is defined for the flow transition. A characteristic curve, termed as the transition curve, is discovered to relate the most critical roughness height with the Reynolds number for a given wave number in the span-wise direction. This curve can provide a quantitative criterion to predict the transition of the Stokes layer caused by the surface roughness. The result demonstrates that the critical roughness height is lower for three-dimensional than for two-dimensional roughness. It is also shown that when the Reynolds number is close to the critical Reynolds number of the global neutral curve (</span></span><em>R</em><span>=600), even a roughness height in the order of one nanometre could significantly interact with the flow and causes the transition. Moreover, when the Reynolds number is around 300, the order of 1 roughness height could be sufficient for the transition. This offers a possible explanation as to why the transitions observed in most of the experimental findings usually occur when the Reynolds number is around 275.</span></p></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":null,"pages":null},"PeriodicalIF":2.5000,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Subcritical transition of the Stokes layer induced by wall surface roughness\",\"authors\":\"Wei Kong\",\"doi\":\"10.1016/j.euromechflu.2023.12.006\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p><span>Wall defect is an important reason for the Stokes layer transition. The present study investigates the transition of the Stokes layer induced by wall surface roughness under subcritical Reynolds numbers<span><span>, which is lower than the critical Reynolds number of the global neutral curve. A pseudo-spectral numerical method is utilized to simulate the interactive effects of different parameters related to surface roughness. Based on the cycle-average pulsation energy, a critical </span>roughness height is defined for the flow transition. A characteristic curve, termed as the transition curve, is discovered to relate the most critical roughness height with the Reynolds number for a given wave number in the span-wise direction. This curve can provide a quantitative criterion to predict the transition of the Stokes layer caused by the surface roughness. The result demonstrates that the critical roughness height is lower for three-dimensional than for two-dimensional roughness. It is also shown that when the Reynolds number is close to the critical Reynolds number of the global neutral curve (</span></span><em>R</em><span>=600), even a roughness height in the order of one nanometre could significantly interact with the flow and causes the transition. Moreover, when the Reynolds number is around 300, the order of 1 roughness height could be sufficient for the transition. This offers a possible explanation as to why the transitions observed in most of the experimental findings usually occur when the Reynolds number is around 275.</span></p></div>\",\"PeriodicalId\":11985,\"journal\":{\"name\":\"European Journal of Mechanics B-fluids\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.5000,\"publicationDate\":\"2023-12-19\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"European Journal of Mechanics B-fluids\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0997754623001796\",\"RegionNum\":3,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MECHANICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Mechanics B-fluids","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0997754623001796","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MECHANICS","Score":null,"Total":0}
Subcritical transition of the Stokes layer induced by wall surface roughness
Wall defect is an important reason for the Stokes layer transition. The present study investigates the transition of the Stokes layer induced by wall surface roughness under subcritical Reynolds numbers, which is lower than the critical Reynolds number of the global neutral curve. A pseudo-spectral numerical method is utilized to simulate the interactive effects of different parameters related to surface roughness. Based on the cycle-average pulsation energy, a critical roughness height is defined for the flow transition. A characteristic curve, termed as the transition curve, is discovered to relate the most critical roughness height with the Reynolds number for a given wave number in the span-wise direction. This curve can provide a quantitative criterion to predict the transition of the Stokes layer caused by the surface roughness. The result demonstrates that the critical roughness height is lower for three-dimensional than for two-dimensional roughness. It is also shown that when the Reynolds number is close to the critical Reynolds number of the global neutral curve (R=600), even a roughness height in the order of one nanometre could significantly interact with the flow and causes the transition. Moreover, when the Reynolds number is around 300, the order of 1 roughness height could be sufficient for the transition. This offers a possible explanation as to why the transitions observed in most of the experimental findings usually occur when the Reynolds number is around 275.
期刊介绍:
The European Journal of Mechanics - B/Fluids publishes papers in all fields of fluid mechanics. Although investigations in well-established areas are within the scope of the journal, recent developments and innovative ideas are particularly welcome. Theoretical, computational and experimental papers are equally welcome. Mathematical methods, be they deterministic or stochastic, analytical or numerical, will be accepted provided they serve to clarify some identifiable problems in fluid mechanics, and provided the significance of results is explained. Similarly, experimental papers must add physical insight in to the understanding of fluid mechanics.