Changes between Version 56 and Version 57 of doc/app/runtime_parameters


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Timestamp:
Sep 14, 2010 7:58:25 AM (15 years ago)
Author:
weinreis
Comment:

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  • doc/app/runtime_parameters

    v56 v57  
    166166Switch to impose random perturbations to the horizontal velocity field.\\\\
    167167With '''create_disturbances''' = .T., random perturbations can be imposed to the horizontal velocity field at certain times e.g. in order to trigger off the onset of convection, etc..\\\\
    168 The temporal interval between these times can be steered with [[dt_disturb]], the vertical range of the perturbations with [[disturbance_level_b]] and [[disturbance_level_t]], and the perturbation amplitude with [[disturbance_amplitude]]. In case of non-cyclic lateral boundary conditions (see [[bc_lr]] and [[bc_ns]]), the horizontal range of the perturbations is determined by [[inflow_disturbance_begin]] and [[inflow_disturbance_end]]. A perturbation is added to each grid point with its individual value determined by multiplying the disturbance amplitude with a uniformly distributed random number. After this, the arrays of u and v are smoothed by applying a Shuman-filter twice and made divergence-free by applying the pressure solver.\\\\
    169 The random number generator to be used can be chosen with [[random_generator]].\\\\
    170 As soon as the desired flow features have developed (e.g.  convection has started), further imposing of perturbations is not necessary and can be omitted (this does not hold for non-cyclic lateral boundaries!). This can be steered by assigning an upper limit value for the perturbation energy (the perturbation energy is defined by the deviation of the velocity from the mean flow) using the parameter [[disturbance_energy_limit]]. As soon as the perturbation energy has exceeded this energy limit, no more random perturbations are assigned.\\\\
    171 Timesteps where a random perturbation has been imposed are marked in the local file [[RUN_CONTROL]] by the character "D" appended to the values of the maximum horizontal velocities.
     168The temporal interval between these times can be steered with [#dt_disturb dt_disturb], the vertical range of the perturbations with [#disturbance_level_b disturbance_level_b] and [#disturbance_level_t disturbance_level_t], and the perturbation amplitude with [#disturbance_amplitude disturbance_amplitude]. In case of non-cyclic lateral boundary conditions (see [[../inipar#bc_lr|bc_lr]] and [[../inipar#bc_ns|bc_ns]]), the horizontal range of the perturbations is determined by [[../inipar#inflow_disturbance_begin|inflow_disturbance_begin]] and [[../inipar#inflow_disturbance_end|inflow_disturbance_end]]. A perturbation is added to each grid point with its individual value determined by multiplying the disturbance amplitude with a uniformly distributed random number. After this, the arrays of u and v are smoothed by applying a Shuman-filter twice and made divergence-free by applying the pressure solver.\\\\
     169The random number generator to be used can be chosen with [[../inipar#random_generator|random_generator]].\\\\
     170As soon as the desired flow features have developed (e.g.  convection has started), further imposing of perturbations is not necessary and can be omitted (this does not hold for non-cyclic lateral boundaries!). This can be steered by assigning an upper limit value for the perturbation energy (the perturbation energy is defined by the deviation of the velocity from the mean flow) using the parameter [#disturbance_energy_limit disturbance_energy_limit]. As soon as the perturbation energy has exceeded this energy limit, no more random perturbations are assigned.\\\\
     171Timesteps where a random perturbation has been imposed are marked in the local file [[../iofiles#RUN_CONTROL|RUN_CONTROL]] by the character "D" appended to the values of the maximum horizontal velocities.
    172172}}}
    173173|----------------