Changes between Version 67 and Version 68 of doc/tec/bc

Timestamp:

Feb 22, 2021 4:41:18 PM (4 years ago)

Author:

wagner

Comment:

--

doc/tec/bc

@@ -310 +310 @@
 == [=#noncyc Non-cyclic lateral boundary conditions] ==
 
-Figure 6 shows the grid structure for non-cyclic boundary conditions at the left/right boundary '''LB/RB''' ([../../app/inipar/#bc_lr bc_lr]) and figure 7 for non-cyclic boundary conditions at the north/south boundary '''NB/SB''' ([../../app/inipar/#bc_ns bc_ns]).
+Figure 6 shows the grid structure for non-cyclic boundary conditions at the left/right boundary '''LB/RB''' ([../../app/initializaton_parameters/#bc_lr bc_lr]) and figure 7 for non-cyclic boundary conditions at the north/south boundary '''NB/SB''' ([../../app/initialization_parameters/#bc_ns bc_ns]).
 The indices (''i,j,k'') represent the directions (''x,y,z''). The model domain extends from ''-1:nx+1'' in the ''x''-direction, from ''-1:ny+1'' in the ''y''-direction and from ''0:nzt+1'' in the ''z''-direction. For the advection scheme of Wicker and Skamarock, two more grid points are added at the lateral boundaries which are not needed for non-cyclic boundary conditions. The figures display the grid layer of the horizontal velocity components ''u'' and ''v'', and scalar ''s''. The grid points of the vertical velocity w are defined at the scalar position but shifted by one half grid spacing in vertical direction (not shown, detailed information about the grid structure in PALM can be found [wiki:doc/tec/discret here]). The prognostic equations are solved at all inner grid points which are marked black. The grid points at the respective non-cyclic boundaries (blue) are treated as follows. '''LB''' is defined at ''i = -1'' for ''v'', ''w'', ''s'' and at ''i = 0'' for ''u''. '''SB''' is defined at ''j = -1'' for ''u'', ''w'', ''s'' and at ''j = 0'' for ''v''. '''RB''' is defined at ''i = nx + 1'' and '''NB''' at ''j = ny + 1'' for all quantities. '''LB''' and '''SB''' are treated this way so that the order and number of grid points for the streamwise velocity component and scalars is the same, independent of the flow direction.
  
@@ -317 +317 @@
  
 
-For non-cyclic lateral boundary conditions, the parameter [../../app/inipar/#psolver psolver] has to be set to '' 'multigrid' '' because the default FFT-solver can only be applied for cyclic boundary conditions.
+For non-cyclic lateral boundary conditions, the parameter [../../app/initialization_parameters/#psolver psolver] has to be set to '' 'multigrid' '' because the default FFT-solver can only be applied for cyclic boundary conditions.
 
 [[Image(grid_lr.png, 600px, border=1)]]
@@ -338 +338 @@
 }}}
 ''t'' denotes the time, Δt the time step and ''s'',,init,, the initialization profile of the scalar quantities which is constant in time.
-The quantities at the inflow are set by the initial vertical profiles (see [../../app/inipar/#initializing_actions initializing_actions]).
+The quantities at the inflow are set by the initial vertical profiles (see [../../app/initialization_parameters/#initializing_actions initializing_actions]).
 A Neumann condition is used for the subgrid-scale turbulent kinetic energy ''e'' (here e.g. for a left-right flow):
 {{{
@@ -363 +363 @@
 \end{align*}
  }}} 
-''d'',,f,, is a damping factor to control the damping intensity, and ''d'',,w,, is the width of the relaxation region extending from the inflow. Quantities ''d'',,f,, and ''d'',,w,, can be set with parameters [../../app/inipar/#pt_damping_factor pt_damping_factor] and [../../app/inipar/#pt_damping_width pt_damping_width], respectively. Both parameters have to be set by the user and must be adjusted case-by-case, because both parameters depend on the numerical and physical conditions, so that application of universal default values is not possible. 
-So far, we have experience with gravity waves in case of cold air outbreaks, which grow in amplitude up to quite extreme values, if no damping is applied. In the respective simulations, we used typical values for [../../app/inipar/#pt_damping_factor pt_damping_factor] of 0.05 and for [../../app/inipar/#pt_damping_width pt_damping_width] of 25 km in order to prevent the gravity waves from growing.
+''d'',,f,, is a damping factor to control the damping intensity, and ''d'',,w,, is the width of the relaxation region extending from the inflow. Quantities ''d'',,f,, and ''d'',,w,, can be set with parameters [../../app/initialization_parameters/#pt_damping_factor pt_damping_factor] and [../../app/initialization_parameters/#pt_damping_width pt_damping_width], respectively. Both parameters have to be set by the user and must be adjusted case-by-case, because both parameters depend on the numerical and physical conditions, so that application of universal default values is not possible. 
+So far, we have experience with gravity waves in case of cold air outbreaks, which grow in amplitude up to quite extreme values, if no damping is applied. In the respective simulations, we used typical values for [../../app/initialization_parameters/#pt_damping_factor pt_damping_factor] of 0.05 and for [../../app/initialization_parameters/#pt_damping_width pt_damping_width] of 25 km in order to prevent the gravity waves from growing.
 
 
 === Outflow boundary ===
 
-At the outflow, an open boundary condition is needed to ensure that disturbances of the mean flow can exit the model domain without effecting the flow upstream. For the scalar quantities, Neumann boundary conditions are used at the outflow boundary which is the simplest way. For the velocity components, a Neumann condition would require to be considered in the solution of the Poisson equation for perturbation pressure, which has not been realized so far, because it requires some technical effort. Instead, PALM offers two types of radiation boundary conditions for the velocity components, which are not in conflict with the pressure solver (see [../../app/inipar/#bc_lr bc_lr] and [../../app/inipar/#bc_ns bc_ns]). For the radiation condition, the Sommerfeld radiation equation is solved at the outflow
+At the outflow, an open boundary condition is needed to ensure that disturbances of the mean flow can exit the model domain without effecting the flow upstream. For the scalar quantities, Neumann boundary conditions are used at the outflow boundary which is the simplest way. For the velocity components, a Neumann condition would require to be considered in the solution of the Poisson equation for perturbation pressure, which has not been realized so far, because it requires some technical effort. Instead, PALM offers two types of radiation boundary conditions for the velocity components, which are not in conflict with the pressure solver (see [../../app/initialization_parameters/#bc_lr bc_lr] and [../../app/initialization_parameters/#bc_ns bc_ns]). For the radiation condition, the Sommerfeld radiation equation is solved at the outflow
 {{{
 #!Latex
@@ -455 +455 @@
 === Mass flux correction ===
 
-PALM offers the possibility of a mass flux correction at the outflow (e.g. [#tian2004 Tian, 2004]). If parameter [../../app/inipar/#conserve_volume_flow conserve_volume_flow] is set true, the mass flux at the inflow and outflow is calculated by:
+PALM offers the possibility of a mass flux correction at the outflow (e.g. [#tian2004 Tian, 2004]). If parameter [../../app/initialization_parameters/#conserve_volume_flow conserve_volume_flow] is set true, the mass flux at the inflow and outflow is calculated by:
 {{{
 #!Latex
@@ -462 +462 @@
 \end{align*}
 }}}
-where ''Δx,,i,,'' and ''ψ'' is equal to ''Δy'' (''Δx'') and ''u'' (''v'') in case of [../../app/inipar/#bc_lr bc_lr] ([../../app/inipar/#bc_ns bc_ns]). The correction factor for the outflow velocity, which is necessary due to different mass fluxes at inflow and outflow, can be calculated by
+where ''Δx,,i,,'' and ''ψ'' is equal to ''Δy'' (''Δx'') and ''u'' (''v'') in case of [../../app/initialization_parameters/#bc_lr bc_lr] ([../../app/initialization_parameters/#bc_ns bc_ns]). The correction factor for the outflow velocity, which is necessary due to different mass fluxes at inflow and outflow, can be calculated by
 {{{
 #!Latex