The no-slip boundary condition in fluid mechanics

Abstract

Ideas leading to the resolut ion of the p rob lem of no-slip condi t ion for fluid veloci ty at a solid surface are t raced in this conc lud ing part of the article. In the c o n t i n u u m limit veloci ty slip being zero is es tabl ished beyond any doubt now. Even tu rbu len t flows wh ich have a large veloci ty g rad ien t near a wall have to satisfy the no-slip condi t ion at every instant . F r o m molecu la r cons idera t ions , on the o ther hand , we know that the velocity slip is proport ional to the m e a n free pa th w h i c h m a y not be negligible in raref ied gas flows. Exper imenta l ver i f icat ion of no-slip has been only ind i rec t and it is only recen t ly that slip veloci ty in nonwet table l iquids has been measu red directly.