Test Data AC5-05
Boundary layer flow and dispersion over isolated hills and valleys
Application Challenge 5-05 © copyright ERCOFTAC 2004
Overview of Tests
Full details of the experimental procedures are provided in Kurshudyan et al (1981). Here we summarise the summary given in CA. The upstream (simulated, neutrally stable atmospheric) boundary layer was developed using a combination of an inlet fence and distributed (10mm, sanspray) roughness. At the hill location (but in its absence), 8.7m downstream of the fence, the boundary layer was only slowly developing and had a depth of about 1m. Profiles of the mean velocity and turbulence stresses are included in the data set, along with all the data obtained for the three hill cases. This data set can be found in the ERCOFTAC database (case 69) and is the final smoothed data generated by Trombetti et al (1991), see Measured data. The free-stream velocity, Uo, was 4m/s so that the Reynolds number based on hill height was about 3 x 104. The scalar source was a 15mm diameter porous sphere, which provided a neutrally buoyant, isokinetic release, with a continuously monitored (constant) flow rate, Q. Averaging times for velocities, stresses and concentrations were at least two minutes, with sampling rates high enough to ensure that statistical errors arising from a finite sample size were insignificant.
Velocity and turbulence profiles were obtained at numerous axial locations. For example, for the lowest slope hill (which had a total length at z=0, a=2L, of 16H or about 1872mm) profiles were taken at x/H=±16, ±8, ±4 and 0, i.e. at one hill length upstream and downstream from the summit, at the upwind and downwind base and half-way up and down the hill slopes. (Note that the x-coordinate origin is the z=0 position beneath the hill summit). Similar relative positions were used for the other hills. The source stack positions were xs/L=±1 or 0, and zs=0.25H, 0.5H, H and 1.5H for each axial location. For each stack position (xs, zs) and each hill (and also the no-hill case), surface concentration profiles were obtained to downwind fetches where the concentration had fallen by at least two orders of magnitude from its maximum. In addition, vertical profiles were obtained at the same x-locations as those used for the flow profiles and corresponding cross-stream profiles were also obtained (generally only at z=zs). The raw concentration values were normalised as: Cn=CUoH2/Q and it is these normalised data which are contained in the aforementioned database. There are no ‘global’ parameters (e.g. hill amplification factors) contained in the database. Most of the computational comparisons contained in CA consist of profile comparisons, although some of these are normalised – e.g. surface concentration normalised by its maximum value or by the corresponding maximum ground level concentration in the absence of the hill.
| NAME | GNDPs | PDPs (problem definition parameters) | MPs (measured parameters) | ||
|---|---|---|---|---|---|
| Re | Hill aspect ratio | Scalar location | detailed data | DOAPs | |
| EXP1 Hill flow and dispersion | 3, 5, 8 | or 0, and , 0.5H, H and 1.5H | C, U, stresses | , etc | |
Table A Summary description of all test cases
| MP1 Normalised C | MP2 | MP3 stresses | DOAPs or other miscellaneous data | |
|---|---|---|---|---|
| EXP 1 File names given in Table C | As file names listed in Table D | As file names in the form: hnms.dat where n is hill case (3, 5 or 8) and m is a two- digit file number Listed in Table C | Specified in files listed in Table C | Specified in files listed in Table C |
Table B Summary description of all measured parameters and available data files. Tabulated data available are provided in the files listed in Tables C and D. Note that the flat surface reference case is in the file: Flatrefcase.dat.
Data filename
Data filename
Data filename
NO HILL
Flatrefcase.dat
HILL 3
h301s.dat
h302s.dat
h303s.dat
h304s.dat
h305s.dat
h306s.dat
h307s.dat
h308s.dat
h309s.dat
h310s.dat
h311s.dat
h312s.dat
h313s.dat
h314s.dat
h315s.dat
h316s.dat
HILL 5
h501s.dat
h502s.dat
h503s.dat
h504s.dat
h505s.dat
h506s.dat
h507s.dat
h508s.dat
h509s.dat
h510s.dat
h511s.dat
h512s.dat
h513s.dat
h514s.dat
h515s.dat
h516s.dat
HILL 8
h801s.dat
h802s.dat
h803s.dat
h804s.dat
h805s.dat
h806s.dat
h807s.dat
h808s.dat
h810s.dat
h811s.dat
h812s.dat
h813s.dat
h814s.dat
h815s.dat
h816s.dat
h817s.dat
TABLE C List of available data files for velocities and turbulent stresses.
NO HILL
Surface concentrations for source heights 29, 59, etc., mm.
Flatref029G.dat
Flatref059G.dat
Flatref117G.dat
Flatref176G.dat
Flatref234G.dat
Flatref351G.dat
Vertical profiles, for 29 and 117mm source heights and given x mm.
FlatrefC029S585V.dat
FlatrefC117S330V.dat
FlatrefC117S585V.dat
FlatrefC117S1170V.dat
FlatrefC117S1600V.dat
FlatrefC117S1872V.dat
HILL 3
Surface concentrations for source heights at 29 or 59mm, located at Upwind base (Uw), Summit (Su) or Downwind base (Dw) of hill.
h3CUwS29G.dat
h3CSuS29G.dat
h3CDwS29G.dat
h3CDwS59G.dat
HILL 5
Surface concentrations for source heights at 29mm and located at Upwind base (Uw), Summit (Su) or Downwind base (Dw) of hill.
h5CUwS29G.dat
h5CSuS29G.dat
h5CDwS29G.dat
HILL 8
Surface concentrations for source heights at 29 or 59mm and located at Upwind base (Uw), Summit (Su) or Downwind base (Dw) of hill.
h8CUwS29G.dat
h8CSuS29G.dat
h8CDwS29G.dat
h8CDwS59G.dat
TABLE D List of available data files for normalised concentrations. © ERCOFTAC 2004 Test Cases - Further Details © ERCOFTAC 2004 Description of Experiment
This is given above. © ERCOFTAC 2004 Boundary Data
The upstream boundary layer data is included in the database. The surface roughness length, zo and normalised friction velocity, u*/Uo, in the usual notation, were 0.16mm and 0.047, respectively. Total turbulence kinetic energy was not measured (although individual profiles of axial and vertical stress and shear stress are available), so in the computations it was estimated – see below. © ERCOFTAC 2004 Measurement Errors
Errors in the hot wire data were reckoned to be within the usual limits obtainable with careful calibration (including proper yaw calibration) – i.e. ±2% on mean velocity and 10-15% in the stresses (normalised by the Uo2). The experimental programme included considerable effort to ensure as high an accuracy as possible. Concentration data was obtained using standard Flame Ionisation Detector techniques and the errors were estimated to be between 4 and 20%; consequent errors in the normalised data are similar, since the accuracy of monitoring both Q and Uo was high. © ERCOFTAC 2004 Measured Data
The original data is contained in text files as Case 69 on the ERCOFTAC database, at the web address: http://cfd.me.umist.ac.uk/ercoftac/. Access to these files is limited and will not be of much help, but they were used to construct the files listed in Tables C & D above. These include data on mean and turbulent velocities and scalar concentrations for three hills and with the various source locations specified earlier. © ERCOFTAC 2004 References
Busuoli, M., Trombetti, F. & Tampieri, F. (1993). Data sets for studies of flow and dispersion in complex terrain: I) the RUSVAL wind tunnel experiment (flow data). CNR Technical Report No.3, FISBAT-RT-93/1
Castro, I.P. & Apsley, D.D. (1997). Flow and dispersion over topography: a comparison between numerical and laboratory data for two-dimensional flows. Atmos. Env., 31, 839-850.
Khurshudyan, L.H and Snyder, W.H & Nekrasov, I.V (1981). Flow and dispersion of pollutants over two-dimensional hills. U.S. Env. Prot. Agcy. Rpt. No. EPA-600/4-81-067. Res. Tri. Pk., NC.
Khurshudyan, L.H and Snyder, W.H & Nekrasov, I.V, I.V and Lawson R.E., Thompson R.S. & Schiermeier F.A. (1990). Flow and dispersion of pollutants within two-dimensional valleys. U.S. Env. Prot. Agcy. Rpt. No. EPA-600/4-79-051. Res. Tri. Pk., NC.
Maurizi, A. (2000) Numerical simulation of turbulent flows over 2D valleys using three versions of the k-ε closure model. J. Wind Eng. Ind. Aero., 85, 59-73.
Trombetti, F., Martano, P. & Tampieri, F. (1991). Data sets for studies of flow and dispersion in complex terrain: I) the RUSHIL wind tunnel experiment (flow data). CNR Technical Report No.1, FISBAT-RT-91/1 © copyright ERCOFTAC 2004
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