The boundary layer around a circular cylinder measured by hot-wire anemometer and identification of separation point by time series data

This study investigates flow separation around a circular cylinder using hot-wire anemometry, with the goal of understanding how boundary layer disturbances affect the separation point over time. Reducing aerodynamic drag through flow control is a key strategy in energy conservation, especially for existing equipment where structural changes are limited. When fluid flow strikes a circular cylinder, it splits at the stagnation point and forms boundary layers along the surface. Depending on flow conditions, separation typically occurs between 80° and 110° from the front, generating a low-pressure wake region downstream. The size and behavior of this wake are closely related to drag force and are influenced by whether the boundary layer is laminar or turbulent. To investigate this phenomenon, we use a custom-made hot-wire probe with a 0.005 mm platinum wire, silver-coated and etched at the sensing region. The probe is mounted on a precision XY-stage to enable measurements extremely close to the cylinder surface. Time-resolved velocity data will be collected at various angular positions using a blow-type wind tunnel. We aim to determine the location and periodic nature of separation, and to analyze the downstream behavior of the separated shear layer. The resulting high-resolution time-series are expected to be valuable for understanding the mechanism of flow separation and for validating future numerical simulations.