03-05 - II. PLUG FLOW MODEL This particular model results...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
II. PLUG FLOW MODEL This particular model results in the "Streeter-Phelps Equation" which describes the oxygen-sag curve in a river. Consider a simple geometrical analog of a river. Q L C X = 0 X lateral direction longitudinal direction Flow = X BOD = DO = Flow = Q BOD = DO = L O C O A = cross sectional area
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Simplifying Assumptions: 1. Plug Flow : each packet of fluid (such as that contained within X ) moves from one end of the river to the other without any longitudinal mixing with neighboring fluid packets. 2. Complete mixing in the lateral direction i.e., all fluid within the volume ( X) ( A) has uniform D.O and BOD concentrations. ( X)(A) = V 3. Q, L O , C O and A are constant. Stream velocity is also constant. Flow velocity= u = Q/A
Background image of page 2
With this flow regime (Q, A and u constant) the distance a fluid element has traveled is directly related to time distance traveled = X = ut so: t = x/u This will let us replace the variable time (t) with its distance equivalent: Ex. For first order BOD kinetics: L=L O e -k 1 t L=L 0 e -k(x/u) Remember : k 1 is different in the laboratory and in the river. Use k 1 for river and k 1 L for lab.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Other Complications (already!) The organic matter in our river has several possible routes (or reactions) including: a. biological oxidation: dL = -k 1 (L) dt b. sedimentation - handle this by assuming sedimentation rate is directly proportional to organic concentration (Ex., organic particles) dL = -k 3 L dt c. resuspension - from previous deposition (we'll assume this is either negligible or taken care of in the rate constant k 3 )
Background image of page 4
• Remember expressing the waste concentration in
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/13/2010 for the course CEE 3510 taught by Professor Lion during the Spring '10 term at Cornell University (Engineering School).

Page1 / 18

03-05 - II. PLUG FLOW MODEL This particular model results...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online