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Rho vee aaaah 0 = [ V A ] incoming + [ V A ] outgoing For steady - PowerPoint PPT Presentation

Apr 11, 2023 •13 likes •113 views

Rho vee aaaah 0 = [ V A ] incoming + [ V A ] outgoing For steady flow through a fixed volume. 1|10 Danger (| V | A ) 1 = (| V | A ) 2 if A increases, then V must decrease oder? 2|10 Photo US Navy (1961,

  1. Rho vee aaaah 0 = Σ [휌 V ⟂ A ] incoming + Σ [휌 V ⟂ A ] outgoing For steady flow through a fixed volume. 1|10

  2. Danger (휌| V ⟂ | A ) 1 = (휌| V ⟂ | A ) 2 “if A increases, then V must decrease” oder? 2|10

  3. Photo US Navy (1961, public domain) 3|10

  4. Photo CC-by-sa by Airwolfhound 4|10

  5. Photo by Lori Losey / NASA (public domain, 2007) 5|10

  6. Rolls-Royce Spey Photo CC-by-sa Arjun Sarup 6|10

  7. Possibly Wrong Fluid Mech 1 only true if 휌 remains constant. OK for water fl ows. No heat transfer, no expansion! Supersonic fl ow: A ↘ can lead to V ↘ because 휌 ↗ . 7|10

  8. Smaller A, larger V? Photo CC -by by Amy Stanley 8|10

  9. Possibly Wrong Fluid Mech 2 There is no causal relationship. A 2 ↘ may mean V 2 ↗ , but... nothing guarantees A 2 V 2 remains constant! (maybe ̇ m ↘ ). Increases in velocity are not “for free”: they require force be applied and energy be spent. 9|10

  10. Are you using the mass balance equation to predict velocity? → also ask yourself: what force, what power required? 10|10

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