Local heat/mass transfer distributions on the bottom surface of a cavity exposed to an approaching turbulent boundary layer: Aspect ratio effects

• Published in: International journal of heat and mass transfer 2022-08, Vol.191, p.122826, Article 122826
• Main Authors: Sachdeva, M., Goldstein, R.J., Srinivasan, V.
• Format: Article
• Language: English
• Subjects: Aspect ratio; Boundary layer flow; Boundary layer separation; Cavity heat transfer; Confinement; Holes; Mass transfer; Mathematical models; Naphthalene; Recirculation; Spatial distribution; Stanton number; Sublimation; Transport properties; Turbulent boundary layer
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2022.122826

•Mass transfer on the bottom surface of rectangular cavities is measured with a naphthalene sublimation technique. The effects of cavity length to depth (0.75 to 10) and width-to-depth (0.54-10) are examined.•Depending on the aspect ratio, the flow structures can be substantially different, yielding significantly different mass transfer distributions on the cavity floor.•The presence of sidewalls establishes a system of vortices which cause strong local variations in transport.•Insight into the high-resolution mass transfer distributions is gained by examining flow streamlines calculated using RANS computations. We investigate convective transport from the bottom surface of rectangular cavities of depth d exposed to an oncoming boundary layer flow, using experimental and numerical techniques. The effects of cavity width W are explored for cavities with different lengths L in the downstream direction. Depending on the value of L/d (0.52≤L/d≤10), the approaching boundary layer separates and reattach on the bottom surface and establish a new boundary layer, or skims past the open face of the cavity. This results in significantly different convective transport coefficient distributions on the bottom surface. As cavity width is reduced, three-dimensional effects arise, with interaction of vortex systems on the cavity floor. Detailed spatial distributions of the transport coefficient are captured using a mass transfer technique based on naphthalene sublimation. Further insight into the flow structure responsible for the observed distributions is gained through numerical simulations using a k−ω SST model that is first validated using the experimental results by using a heat/mass transfer analogy factor. Flow streamlines from the computations are used to explain how the time averaged streamlines affect the heat transfer at the bottom surface.