Transient Boundary Layers

Boundary layer flows in internal combustion engines (important to understand for heat transfer predictions) behave quite differently from steady boundary layers since external flow, temperature, and pressure continuously change and do not permit the development of a well-established boundary layer flow. Detailed insights into the transient nature of such flows in engines have been comprised for a long time due to limitations in experimental techniques. High-frame-rate laser based imaging tools have been developed and now allow in-depth studies that support the development of advanced and truly predictive simulation tools.

Flow field imaging example

Temperature field imaging example

Temperature inhomogeneities are significantly higher near the cylinder head than in the bulk gas. Substantial changes during an engine cycle are observed.