| 3 | | Starting from version 3.5 PALM includes a so-called turbulence recycling method which allows a turbulent inflow with non-cyclic horizontal boundary conditions. The method follows the one described by Lund et al. (1998, J. Comp. Phys., '''140''', 233-258), modified by Kataoka and Mizuno (2002, Wind and Structures, '''5''', 379-392). The method is switched on by setting the initial parameter [../../inipar#turbulent_inflow turbulent_inflow] = ''.TRUE.''.\\\\ |
| 4 | | The turbulent signal A'(y,z) to be imposed at the left inflow boundary is taken from the same simulation at a fixed distance x,,r,, from the inflow (given by parameter [../../inipar#recycling_width recycling_width]): A'(y,z) = A(x,,r,,,y,z) - '''A(z)''', where '''A(z)''' is the line average along y at x = x,,r,,. The turbulent quantity A'(y,z) is then added to a mean inflow profile a(z) which is the horizontal (and temporal) average as calculated from a precursor run. This is done after each timestep.\\\\ |
| 5 | | '''So far (09/16/08), a turbulent signal is imposed to all prognostic variables except humidity (passive scalar) and salinity! '''\\\\ |
| 6 | | In order to avoid a continous growth of the turbulent layer with time, the height up to which turbulence is recycled is limited by parameter [../../inipar#inflow_damping_height inflow_damping_height]. By default, this height is calculated and taken from the precursor run.\\\\ |
| | 3 | Starting from version 3.5 PALM includes a so-called turbulence recycling method which allows a turbulent inflow with non-cyclic horizontal boundary conditions. The method follows the one described by Lund et al. (1998), modified by Kataoka and Mizuno (2002). The method is switched on by setting the initial parameter [../../inipar#turbulent_inflow turbulent_inflow] = ''.TRUE.''. |
| | 4 | |
| | 5 | The turbulent signal A'(y,z) to be imposed at the left inflow boundary is taken from the same simulation at a fixed distance x,,r,, from the inflow (given by parameter [../../inipar#recycling_width recycling_width]): A'(y,z) = A(x,,r,,,y,z) - '''A(x,,r,,,z)''', where '''A(x,,r,,,z)''' is the line average along y. The turbulent quantity A'(y,z) is then added to a mean inflow profile a(z) which is the horizontal (and temporal) average as calculated from a precursor run. This is done after each timestep. |
| | 6 | |
| | 7 | In order to avoid a continous growth of the turbulent layer with time, the height up to which turbulence is recycled is limited by parameter [../../inipar#inflow_damping_height inflow_damping_height]. By default, this height is calculated and taken from the precursor run. |
| | 8 | |
| | 9 | '''So far, a turbulent inflow is realized from the left (west) side only (05/04/16)! ''' |
| | 10 | |
| 11 | | * The main run requires from the precursor run the mean profiles to be used at the inflow. For this, the horizontally and temporally averaged mean profiles as provided with the standard PALM output are used. The user has to set parameters [../../d3par#dt_dopr dt_dopr], [../../d3par#averaging_interval averaging_interval], etc. for the precursor run appropriately, so that an output is done '''at the end''' of the precursor run. The profile information is then contained in the restart (binary) file created at the end of the precursor run and can be used by the main run. '''It is very important that the mean profiles at the end of the precursor run are in a stationary or quasi-stationary state''', because otherwise it may not be justified to use them as constant profiles at the inflow. '''Also, turbulence at the end of the precursor run should be fully developed.''' Otherwise, the main run would need an additional spinup-time at the beginning to get the turbulence to its final stage. |
| | 15 | * The main run requires the mean profiles from the precursor run to be used at the inflow. For this, the horizontally and temporally averaged mean profiles as provided with the standard PALM output are used. The user has to set parameters [../../d3par#dt_dopr dt_dopr], [../../d3par#averaging_interval averaging_interval], etc. for the precursor run appropriately, so that an output is done '''at the end''' of the precursor run. The profile information is then contained in the restart (binary) file created at the end of the precursor run and can be used by the main run. '''It is very important that the mean profiles at the end of the precursor run are in a stationary or quasi-stationary state''', because otherwise it may not be justified to use them as constant profiles at the inflow. '''Also, turbulence at the end of the precursor run should be fully developed.''' Otherwise, the main run would need an additional spinup-time at the beginning to get the turbulence to its final stage. |
| | 26 | |
| | 27 | The recycled turbulence, which is mapped from the recycling plane to the inflow boundary, can be shifted in y direction. This y-shift reduces persistent streaks that may occur within the recycling domain. To use the y-shift [../../inipar#recycling_yshift recycling_yshift] = .T. needs to be set. The distance of the y-shift is INT([../../d3par#npey npey] / 2), which is in most cases the best distance for effectively reducing streaks in the recycling domain. |
| | 28 | |
| | 29 | === References === |
| | 30 | |
| | 31 | * '''Lund, T. S., X. Wu and K. D. Squires, 1998:''' Generation of turbulent inflow data for spatially-developing boundary layer simulations. ''J. Comput. Phys.'', '''140''', 233-258. |
| | 32 | |
| | 33 | * '''Kataoka, H. and M. Mizuno, 2002:''' Numerical flow computation around aeroelastic 3D square cylinder using inflow turbulence. ''Wind Struct.'', '''5''', 379-392. |
