Boundary membrane - Kyomaku

Also known as a laminar sublayer, when a turbulent boundary layer occurs on the surface of an object placed in a moving fluid, the extremely thin layer in contact with the object's surface inside the boundary layer is not affected by the turbulence in the outer boundary layer, and the flow maintains a laminar state. This extremely thin layer is called a boundary film. There is no clear boundary surface between the laminar boundary film and the turbulent region, and the flow changes from the laminar region through a region affected by some turbulence to the turbulent region. T. Stanton was the first to experimentally confirm the existence of this boundary film. The velocity distribution within the boundary film is approximately linear, and the shear stress is thought to be constant and equal to the value on the object's surface. Additionally, within the boundary film, heat is transferred by molecular diffusion of the heat-conducting substance.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

層流底層ともいわれるもので，運動している流体中に置かれた物体の表面に乱流境界層が生じる場合，境界層内部の物体表面に接したきわめて薄い層では，外側の境界層内の乱れの影響が及ばず，流れは層流状態を保つ．このごく薄い層を境膜という．層流である境膜と乱流域との間には明確な境界面は存在せず，層流域から多少乱れの影響を受けた領域を経て乱流域へ変化する．この境膜の存在を実験的に最初に確認したのはT. Stantonである．境膜内の速度分布はほぼ直線的であり，せん断応力は一定で物体表面上の値に等しいと考えられる．また，境膜内では，熱は熱伝導物質の分子拡散により移動する．

出典　森北出版「化学辞典（第2版）」化学辞典 第2版について　情報