Every body flowed around is subject (besides hydrostatic lift) to a flow-induced force, which depends mainly on the velocity of flow, the size of the body and the shape of the body. The shape of the body is represented by the dimensionless number, the drag coefficient cd.
  The goal of scientific study and practical application (e.g. in vehicle construction) is to design the perfect body shape in order to keep drag low. The drag coefficient for arbitrarily shaped bodies can only be determined reliably by experimentation.  
  The HM 225.04 experimental unit - used in the HM 225 Aerodynamics Trainer - allows drag to be measured in various models so as to determine the respective drag coefficients. In the measurement section, a model (plate, cylinder and streamlined body) is used as a drag body. The forces occurring in the air flow are measured with a beam scale with movable weight. When conducting the experiment with a cylinder, a Pitot tube can be used to record a pressure distribution of the surrounding flow.
  Also, the drag can be measured indirectly via the pulse rate. The Pitot tube, movable obliquely to the direction of flow, allows pressures to be recorded so as to determine the velocity profile downstream of the cylinder and thus to gauge the wake depression.
  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.
 

- measure drag forces when flowing around models
- determining drag coefficients
- application of the pulse rate
- record pressure distribution on the cylinder flowed

  around
- measure the wake depression behind the cylinder

  under surrounding flow