Module 10 - Flow Visualisation Flashcards
How might flow visualization help in the design of an experiment?
- identify areas of interest without expensive equipment
- determine which locations should be measured
- predict what instruments are required
Avoid procurement of multiple instruments or investment in an experiment that won’t work
What are the four types of lines used to describe fluid motion?
Streamline: line whose tangent is the local velocity vector at each point
Streakline: locus of fluid elements which passed through a point previously
Pathline: path of a single fluid elements in the flow
Timeline: line that connects adjacent fluid elements in a flow at a time
What are some flow features that can be observed using surface flow visualization?
Separation and reattachment of flow
Recirculating zones
Secondary flow
Termination of vortices
Stagnation
How can smoke wire be used to create timelines?
A vertical line of smoke is released from the wire, which is perpendicular to the flow
What factors could affect interpretation of dye injection flow visualization?
- dye density should be close to fluid to avoid interfering with the flow field
- flow rate at which dye is injected needs to be carefully selected to not interfere with flow
Why is PSP a quantitative flow vis method?
- can use an algorithm to determine the pressure on the surface using contours in the images
- qualitative observations can be made - you can see flow structures based on the surface pressure field
Can tufts be used to estimate turbulence intensity?
- can observe how frequently the tufts fluctuate as they are able to respond quickly to fluctuations in the flow
- frequent fluctuations in the tuft direction are indicative of high turbulence intensity
- tufts following the flow with minimal disturbance are indicative of low turbulence intensity
Which flow visualization method can be used to identify location of shock waves?
Schlieren photography - shows gradient of density which is sharp at a shock wave
