# 3-D Flow in cities

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 January 8, 2009, 06:21 3-D Flow in cities #1 michael schorling Guest   Posts: n/a Given a digital elevation model of a city size 5*5 kmē at a resolution of at least 5 m and diagnostic information to the wind at one or more measurement sites within the city. What are the chances to compute a reasonably correct 3-D windfield for that area considering lee wakes, circulation etc. and what might be the computing time?

 January 8, 2009, 09:05 Re: 3-D Flow in cities #2 Anastasios Georgoulas Guest   Posts: n/a It higly depends on the mesh resolution that you are going to use. For example i have simulated sediment transport from the outflow of a river into the ocean using a digital elevation model of the river mouth of an aproximate area 5x5 km2. My flow was multiphase including 5 flow phases and the simulation time was 2000 sec of real flow in 24 hours of calculations. However this is an unsteady case. Your case should probably be steady hence it is even better. However you will need a good pc configuration. I use a dual core intel pc with 8 gbytes of ram and 64-bit Ubuntu(Linux)operational system. But you can also increase the simulation speed using Parallel Processing. Anyway, the chalenge will be the meshing! I think that the for say 100000 cells you need 100 Mbyte of ram memory. Hence you should limit the number of cells acoording to the available ram in your pc. Best luck Anastasios

 January 8, 2009, 09:36 Re: 3-D Flow in cities #3 michael schorling Guest   Posts: n/a Thank you, Anastasios, for your response. I wonder whether we are talking about the same subject. Having many lines of arbitrary formed buildings in a city the developing lee vortices will influence each other. Can this reasonably simulated applying a Navier Stokes Solver to get a multi-layered wind field for the city? What might the computing time at a well equipped PC? Thanks Michael

 January 8, 2009, 11:28 Re: 3-D Flow in cities #4 Anastasios Georgoulas Guest   Posts: n/a I think that this can be reasonably simulated. As for the time it depends on many thinks. The most important ones are the number of computational cells comprising the mesh and if the simulation is going to be steady or unsteady. If you give me some more info regarding your mesh as well as the initial and boundary conditions i could probably give you a rough estimate.

 January 9, 2009, 08:10 Re: 3-D Flow in cities #5 michael schorling Guest   Posts: n/a Thank you for your response - if you could let me know your email address i would send you some graphs. Thank you Michael Schorling

 January 13, 2009, 02:47 Re: 3-D Flow in cities #6 Anastasios Guest   Posts: n/a

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