Carlos Pimentel's blog

By oversimplifying things, there is the risk of losing details that could affect the correct interpretation of a physical phenomenon. However, using common sense and logic based on premises derived from physical observations can lead to a better interpretation of veiled concepts that cannot be understood in more abstract ways. This test consists of four questions, of which at least the first three seem to be so obvious that they could fall into the concept of  silly  questions; however, it is necessary to ask them to understand the last one and the whole meaning of this publication.  All pictures are retrieved from  'An Album of Fluid Motion'  (van Dyke, 1982), in which a viscous flow (fluid: water) past a circular cylinder under different Reynolds number (Re) conditions. 1.   Which of the following two images represents a fluid past at an  extremely low Reynolds number ?: a)   b) a)  This option is a  completely opposite condition , where inertial forces dominate over viscous

Since the Coandă effect (CE) is precisely an 'effect', it cannot be by itself a cause of any force, the same as the pressure field in the velocity-vorticity formulation of the Navier-Stokes equations (vortex methods), in which such a field is decoupled from the flow solution (it can be obtained by reconstruction of the stream function). The real cause of lift (and drag!) generation is vorticity, detached from the entire surface [1,2,3], in addition to viscosity (under certain operating conditions; low AoA range). Thus, the correct question should be: Is the "Coanda effect"* related to lift on an airfoil? The short answer is: yes, and no. I mean, in first instance, it depends on the orientation of the flow when such an airfoil is operating. For the low AoA range, the CE seems to be present due to the effect of the viscosity and the curvature in contact with the fluid; however, if such an airfoil (at the same Reynolds number; Re) is stalled, the CE is absent since th