Design and Fabrication of Smoke Flow Visualization Setup for Existing Wind Tunnel at Pulchowk Campus
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IOE Pulchowk Campus
Abstract
Flow visualization methods have been used to understand and demonstrate invisible flow
structures in aerodynamics and other fields. Visualization in wind tunnel is a major
technique used to study the flow pattern around different objects. There are mainly two
methods of visualization, intrusive and non-intrusive. Non-intrusive methods using laws of
optics require the variation of density in the flow which is not suitable for low-speed
subsonic wind tunnels. Smoke flow visualization using smoke rake is one of the frequently
used intrusive techniques for wind tunnel flow visualization. A laminar smoke filament is
injected through some mechanism to the flow field in this method. The requirement for
this smoke filament is to be laminar and sufficiently long to see flow around test object. In
this research work, a simple smoke introducing mechanism setup was made. The smoke
rake with airfoil profile of NACA 0012 with extruding pipe for smoke injection is
designed and flow around it analyzed using 2d numerical simulation to see its disturbance
in flow field. Its disturbance is found to be dissipated and flow to be laminar before
entering test section region. For the smoke generation, fog machine of 1500 W is used and
the smoke is pushed through the smoke reservoir into the smoke rake using AC fan. The
test is conducted around cylinder, airfoil and ramp structure. In cylinder, turbulent wake
region was clearly visible and Karman Vortex Street was also visualized. Flow separation
region in cambered airfoil was also visualized. For constant, steady injection of the smoke
into the wind tunnel variable speed fan is recommended in the smoke reservoir.
Description
Flow visualization is a major subfield within experimental fluid mechanics. Making
flow patterns visible have been of major interest in aerodynamics from long ago. It
helps us to understand the different flow structure in many complex flow fields by
enabling us to get the insights of flow from visual inspection.