Vol Lecture Notes 7

# Why do they move so fast and so far model of sparks

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Sparks and others (1978) Deﬁnition of key parameters in Sparks et al. (1978) model. 9 Governing Equations C o n tin u ity ( m a s s c o n s e r v a tio n ) e q u a tio n uhr = u0 h0 r0 E n e r g y c o n s e r v a tio n ! "u "u + !u = g sin(#\$! ) % 0.5 c f !u 2 h "t "r u: velocity, ρ: bulk density of flow, ∆ρ: difference between density of flow and atmosphere, α, slope, cf: between drag coefficient of surface, h: flow thickness, g: drag acceleration of gravity, r: radial distance from vent; acceleration subscript 0 denotes initial values. A s s u m e h ig h R e y n o ld s N o . ( i.e . n e g le c t v is c o u s fo r c e s ) . Ignimbrite Flow Model Flow down a volcanic slope of 15°, flattening to 1° after 8 km. Coefficient of drag 0.005 to 0.02 Initial velocities easily exceed 100 m/sec (360 km/hr) Acceleration down steep slope, Flow slows to a steady state 25-50 m/s as it reaches lower slope and spreads radially. Steady state achieved when gravitation energy matches frictional energy. 10 Ignimbrite Flow Model Init...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online