blobmodel 0.1.1

Two dimensional model of propagating blobs

2d_propagating_blobs

Two dimensional model of advecting and dissipating blobs.

The code has been deveoped originally to model profiles in the scrape-off layer of fusion experiments but it can be used to model any 2d system consisting of advecting pulses. An example is shown below:

Installation

Dev install:

git clone https://github.com/uit-cosmo/2d_propagating_blobs.git
cd 2d_propagating_blobs
pip install -e .

Usage

Create the grid on which the blobs are discretized with using the Model class. The make_realization() method computes the output as an xarray dataset which can also be written out as a netcdf file if the argument file_name is specified. A simple example is shown below:

from blobmodel import Model, show_model

bm = Model(Nx=200, Ny=100, Lx=10, Ly=10, dt=0.1, T=20, blob_shape='gauss',num_blobs=100)

ds = bm.make_realization(file_name="example.nc")

The data can be shown as an animation using the show_model function:

show_model(ds)

You can specify the blob parameters with a BlobFactory class. The DefaultBlobFactory class has some of the most common distribution functions implemented. An example would look like this:

from blobmodel import Model, DefaultBlobFactory

# use DefaultBlobFactory to define distribution functions fo random variables
bf = DefaultBlobFactory(A_dist="exp", W_dist="uniform", vx_dist="deg", vy_dist="normal")

# pass on bf when creating the Model
tmp = Model(
    Nx=100,
    Ny=1,
    Lx=10,
    Ly=0,
    dt=1,
    T=1000,
    blob_shape="exp",
    t_drain=2,
    periodic_y=False,
    num_blobs=10000,
    blob_factory=bf,
)

Alternatively, you can specify all blob parameters exactly as you want by writing your own class which inherits from BlobFactory. See examples/custom_blobfactory.py as an example.

Input parameters

Model()

• Nx: int, grid points in x
• Ny: int, grid points in y
• Lx: float, length of grid in x
• Ly: float, length of grid in y
• dt: float, time step
• T: float, time length
• periodic_y: bool, optional, allow periodicity in y-direction
• blob_shape: str, optional, switch between gauss and exp blob
• num_blobs: int, optional number of blobs
• t_drain: float, optional, drain time for blobs
• blob_factory: BlobFactory, optional, object containing blob parameters
• labels: bool, optional, if True, field with blob labels is returned used for creating training data for supervised machine learning algorithms
• label_border: float, optional, defines region of blob as region where density >= label_border * amplitude of Blob only used if labels = True

DefaultBlobFactory()

• A_dist: str, optional, distribution of blob amplitudes
• W_dist: str, optional, distribution of blob widths
• vx_dist: str, optinal, distribution of blob velocities in x-dimension
• vy_dist: str, optinal, distribution of blob velocities in y-dimension
• A_parameter: float, optional, free_parameter for amplitudes
• W_parameter: float, optional, free_parameter for widths
• vx_parameter: float, optional, free_parameter for vx
• vy_parameter: float, optional, free_parameter for vy

The following distributions are implemented:

• exp: exponential distribution with mean 1
• gamma: gamma distribution with free_parameter as shape parameter and mean 1
• normal: normal distribution with zero mean and free_parameter as scale parameter
• uniform: uniorm distribution with mean 1 and free_parameter as width
• ray: rayleight distribution with mean 1
• deg: array on ones
• zeros: array of zeros

make_realization()

• file_name: str, optional, file name for .nc file containing data as xarray dataset

• speed_up: bool, optional, speeding up code by discretizing each single blob at smaller time window when blob values fall under given error value the blob gets discarded

        !!!  this is only a good approximation for blob_shape='exp' !!!
  

• error: float, optional, numerical error at x = Lx when blob gets truncated

show_model()

• ds: xarray Dataset, Model data
• interval: int, optional, time interval between frames in ms
• save: bool, optional, if True save animation as gif
• gif_name: str, optional, set name for gif
• fps: int, optional, set fps for gif

Contact

If you have questions, suggestions or other comments you can contact me under [e-mail]