PROBLEM DEFINITION

Two buildings are exposed to a side wind and obstruct the flow, generating recirculations and turbulence from shear. A pollution source is located somewhere in the field. The goal is to solve for the flow field and concentration of pollutant throughout the field. Turbulence is resolved with a Large Eddy Simulation; subgrid turbulence is parameterized using a two-parameter k-e model. We are considering steady-state conditions. The geometry and initial/boundary conditions are illustrated below:

EXECUTABLE AND INPUT FILE

Input file (PROB.INP)

Windows 3.x/9x/ME/2000/NT Executable (CANYON.EXE)

Obtain both files in a compressed package (CANYON.ZIP)

SAMPLE RESULTS

These simulation results and graphics were generated by Carlos and Paula Agudelo. The graphics were generated with IDL.

Turbulent kinetic energy contours generated by the wind shear:

Concentration contours and velocity profiles for a source located between buildings (generated using IDL):

Concentration contours and velocity profiles for a source located between buildings (generated using IDL):

Sample results input file (PROB.INP)

*

* ===[ PARAMETER'S FILE FOR CANYON - All units in SI ]=================

*

===[ DIMENSIONS OF FIELD ]=============================================

Length of upwind, Bldg1, Canyon, Bldg2, and downwind section [ ALUP, ALBL1, ALMID, ALBL2, ALDN ]

0.5, 0.25, 0.25, 0.25, 2.0

Height of Bldg 1, Bldg 2, and Free space above bldg 1 [ HGBL, HGBL2, HGUP ]

0.2, 0.1, 0.4

===[ GRID POINTS ]=====================================================

x-direction: # of cells for upwind, Bldg1, Canyon, Bldg2, and downwind sections

20, 20, 20, 20, 20

y-direction: # of cells for building and above-bldg 1 sections

30, 60

===[ LOCATION OF POINT SOURCE ]========================================

X,Y location of source [ XSRC, YSRC ]

0.875, 0.01

===[ COORDINATES OF MONITORING POINT ]=================================

I,J monitoring location [ IMON, JMON ]

5, 5

===[ GET INFO FOR BOUNDARY CONDITIONS ]================================

Velocity at inlet of flow domain [ UIN ]

1.0

Turbulence intensity factor at inlet of flow domain [ TURBIN ]

0.03

Length scale factor at inlet of flow domain [ ALAMDA ]

0.005

===[ PROGRAM CONTROL PARAMETERS ]======================================

Maximum number of iterations [ MAXIT ]

150

Maximum residual [ SORMAX ]

0.005

Index for field printout [ INDPRI ]

1000

===[ DEPENDENT VARIABLES ]=============================================

Solve for hydrodynamic cycle (U,V,P) [.TRUE.=Yes, .FALSE.=No]

.true.

Solve for concentration equation [ INCALT ]

.true.

Solve for turbulence (kapa,epsilon) [.TRUE.=Yes, .FALSE.=No]

.TRUE.

===[ NUMBER OF SWEEPS FOR ALL VARIABLES ]==============================

Number of application of line iteration for u-, v- equations [ LITERU ]

2

Number of application of line iteration for p'-equation [ LITERP ]

5

Number of application of line iteration for C-equation [ LITERT ]

2

Number of application of line iteration for tubulence closure eqns [ LITERK ]

2

===[ UNDER-RELAXATION ]================================================

Under relaxation factor for u-, V-velocity [ URFU ]

0.5

Under relaxation factor for pressure correction [ URFP ]

0.25

Under relaxation factor for temperature [ URFT ]

0.7

Under relaxation factor for energy dissipation [ URFE ]

0.7

Under relaxation factor for turbulence energy [ URFK ]

0.7

Under relaxation factor for viscosity [ URFVIS ]

0.7

===[ COORDINATES OF FIXED PRESSURE POINT ]=============================

Axial fixed-pressure location index [ IPREF, JPREF ]

2, 2

===[ FLUID PROPERTIES ]================================================

Fluid density at inlet of calculation domain [ DENSIT ]

1.0

Laminar fluid viscosity [ VISCOS ]

1e-5

Laminar Prandtl number [ PRANDT ]

1.0

===[ CONSTANTS OF TURBULENCE MODEL K-E ]===============================

Constants of turbulence model [ CMU,CD,C1,C2 ]

0.09,1.0,1.44,1.92

Von Karman constant [ CAPPA ]

0.4187

Integration constant of turbulence model [ ELOG ]

9.793

Constant of turbulence model in k-, e-, t-equations [ PRTE, PRED, PRT ]

1.0, 1.3, 0.9

===[ SOLVER SELECTION ]================================================

Solver for u-,V-velocity equations [ ISLVU ]

1

Solver for pressure correction equationn [ ISLVP ]

1

Solver for concentration equations [ ISLVT ]

1

Solver for turbulence closure equations [ ISLVE ]

1

===[ FILING SYSTEM ]===================================================

Name of main output file [ OUTFIL ]

result.out