Investigation of Residence Time Distribution and Local Mean Age of Fluid to Determine Dead-Zones in Flow Field

Investigation of Residence Time Distribution and Local Mean Age of Fluid to Determine Dead-Zones in Flow Field

T. Karches | K. Buzas

Department of Sanitary and Environmental Engineering, Budapest University of Technology and Economics, Hungary

| |
| | Citation



Residence time and local mean age of fluid are important parameters of the fluid flow, with which we are able to detect the functioning and non-functioning zones. It is a novel approach to estimate the effect of dead-zones on chemical and biological processes. In this paper, we introduce a numerical tracer study, which is calibrated by field measurements and which is applied in different cases such as settling tank and aeration tank of wastewater treatment. Using an advective-diffusive passive scalar transport equation, the age of the fluid can be calculated. It also shows the short-circuits and dead-zones of the fluid and this corresponds with our observations. This method helps eliminate potential hydraulic problems at the early stage of design.


CFD, dead-zone, local mean age, tracer study


[1] ATV-DVWK Arbeitsblatt-A-131, GFA, Hennef, 2000.

[2] Greenfi eld, P.F., Howes, T., Johns, M.R., Keller, J. & Wood, M.G., Computational fl uiddynamic modelling of wastewater ponds to improve design. Water Science and Technology,31(12), pp. 111–118, 1995. doi:

[3] Brouckaert, C.J. & Buckley, C.A., The use of computational fl uid dynamics forimproving the design and operation of water and wastewater treatment plants. WaterScience and Technology, 40(4–5), pp. 81–90, 1999. doi:

[4] Bartrand, T.A., Farouk, B., Greene, D.J., Haas, C.N., Liberti, L., Notarnicola, M. &Santoro, D., Use of CFD for wastewater disinfection process analysis: E.coli inactivationwith peroxyacetic acid (PAA). International Journal of Chemical Reactor Engineering,3(46), pp. 1283–1287, 2005.

[5] Gentric, C., Leclerc, J.P., Moullec, Y.L. & Potier, O., Flow fi eld and residence timedistribution simulation of a cross-fl ow gas-liquid wastewater treatment reactor usingCFD. Chemical Engineering Science, 63, pp. 2436–2449, 2008. doi:

[6] Burt, D.J. & Ganeshalingam, J., Design and optimisation of fi nal clarifi er performancewith CFD modelling. CIWEM conference Design and operation of activated sludgeplants, 2005.

[7] Armbruster, M., Krebs P. & Rodi, W., Numerical modelling of dynamic sludge blanketbehaviour in secondary clarifi ers. Water Science and Technology, 43(11), pp. 173–180,2001.

[8] Patziger, M., Kainz, H., Hunze, M. & Józsa, J., Analysing sludge balance in activatedsludge systems with a novel mass transport model. Water Science and Technology,57(9), pp. 1413–1419, 2008. doi:

[9] Foias, C., Manley, O., Rosa, R. & Temam, R., Navier-Stokes Equations and Turbulence,Cambridge Books Online, Cambridge, pp. 1–3, 2001. doi:

[10] Launder, B.E. & Spalding, D.B., The numerical computation of turbulent fl ow.Computer Methods in Applied Mechanics and Engineering, 3(2), pp. 269–289, 1974.doi:

[11] Fluent 6.3 Users Guide. Ansys Inc., USA.

[12] Manninen, M., Taivassalo, V. & Kallio, S. On the Mixture Model for Multiphase Flow.VTT Publications 288, Technical Research Centre of Finland, 1996.

[13] Kurasinski, T. & Kuncewicz, Cz., Determination of turbulent diffusion coeffi cient inan agitator for special type of impeller. 3th European Conference on Mixing, London,2009.

[14] Chanteloup, V. & Mirade, P.-S., Computational fl uid dynamics (CFD) modelling oflocal mean age of air distribution in forced-ventilation food plants. Journal of FoodEngineering, 90, pp. 90–103, 2009. doi:

[15] Buttz, J.A. & Daigger, G.T., Upgrading Wastewater Treatment Plants, Technomic PubCo.: Lancaster, PA, Vol. 2, pp. 13–53, 1998.

[16] Karches, T. & Buzas, K. Methodology to determine residence time distribution andsmall scale phenomena in settling tanks. Computational Methods in Multiphase FlowVI. WIT Transactions on Engineering Sciences, 70, pp. 117–126, 2011. doi:

[17] Karches, T. & Melicz, Z., Problem detection in a small wastewater treatment tank withthe tool of computational fl uid dynamics. 9th international Congress on Advances inCivil Engineering, KTU,Trabzon, Turkey, 2010.

[18] Laramee, R.S., Hauser, H., Zhao, L. & Post, F.H., Topology-based fl ow visualization.The state of the Art. Proceedings of Topo-In-Vis, Budmerice, Slovakia, 2005.

[19] Chong, M.S., Perry, A.E. & Cantwell, B.J., A general classifi cation of thre edimensionalfl ow fi elds. Phys Fluids A, 2(5), pp. 765–778, 1990. doi: