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The Coanda effect refers to the characteristic of flowing fluids to follow the curvature of a convex surface instead of continuing in the original direction of flow. Nowadays this effect is applied in various fields of engineering, e.g. to increase lift in air travel, to control the air flow in air conditioning or as a pneumatic logic element in industrial control systems. Pneumatic logic elements have the advantage that they do not wear out, they work reliably and are resistant to heat, ionising radiation and vibration. The direction of flow in pneumatic logic elements is switched with a turbulent free jet (control jet), which for example, emerges from a nozzle and entrains the fluid from the environment (boundary layer). Since the control jet is usually weaker than the jet to be deflected, we refer to the amplification effect.
The HM 225.06 experimental unit - used in the aerodynamics trainer HM 225 - allows the demonstration of the Coanda effect on a pneumatic logic element.
The air flows through a Y-shaped channel with two outlets. The lateral inflow of air into the channel (control jet) can switch the air flow between the two outlets.
The contour of the channel is varied via pivoting and sliding elements, so as to study how the switchover works. Scales allow precise adjustment of the elements.
The experimental unit is attached to 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
- investigation of wall-guided air flow (Coanda effect)
- familiarisation with the principle of pneumatic logic elements
- study amplification effect in pneumatic elements