During incident flow of bodies fluids such as air "stick" to the surface of the body and form the so-called boundary layer. The kind of flow within the boundary layer - laminar or turbulent - significantly affects the drag. The findings from studying the boundary layer are taken into consideration when designing aerofoils, turbine blades and hull, rudder and propeller blades. The HM 225.02 experimental unit - used in the HM 225 Aerodynamics Trainer - allows the boundary layer on a flat plate to be studied. For this purpose, air flows along the plate, parallel to the surface. The plate has two different surfaces so as to study the effect of surface conditions on the boundary layer. Side bodies can be used in the measurement section. Thus the boundary layer phenomena can experience interference with a degressive or progressive pressure curve and, for example equalise the friction loss of the flow. A horizontally movable pitot tube, adjusted using a micrometer screw, measures the total pressures at various distances from the plate surface. The plate can be moved vertically to enable the recording of total pressures in the direction of flow. The velocity can be determined from the pressures read off the HM 225.01 16-Tube Manometer. The experimental unit is attached to the air outlet of the HM 225 trainer, simply and precisely with quick release fasteners. The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- internal friction of gases - investigation of the boundary layer on the flat plate - influence of surface roughness on the formation of
a boundary layer - boundary layer interference with
degressive/progressive pressure curve
* Investigation of the boundary layer at two different
rough surfaces1 * Boundary layer interference with pressure profile1 * Accessories for HM 225 Aerodynamics Trainer
 investigation of boundary layers on a flat plate with flow along the plate  accessories for HM 225 Aerodynamics Trainer  plate with two different rough surfaces  vertical displacement of the plate  pitot tube for measuring the total pressure at the plate  horizontal adjustment of the pitot tube using micrometer screw  removable side bodies for interference of the boundary layer with degressive or progressive pressure profile  tube manometer, 16-fold (HM 225.01) for displaying the dynamic pressures is recommended