Getting field data

It is highly recommended to go through sample generation process with CST or FFD before proceeding ahead. The process to generate field data along with scalar output is independent of parametrization method. You need to set two options in blackbox options dictionary: getFlowFieldData and region. The getFlowFieldData option is a boolean which enables field data extraction while region option defines region of extraction which can be either field or surface. The field option extracts data from the entire field while surface option extracts data from the surface of airfoil only. The surfaceVariables option in solver option dictionary controls which variables to extract. Please refer ADflow options for more details. Rest all process is same as described in sample generation tutorial.

Reading the output data is exactly same as described in sample generation sections. There is only one additional file: fieldData.mat which contains following quatities:

• Input variable: a 2D numpy array x in which each row represents a specific sample based on which analysis is performed. The number of rows will be usually equal to the number of samples argument in the generateSamples method. But, many times few of the analysis fail. It depends a lot on the solver and meshing options, so set those options after some tuning.

  Note

  The order of values in each row is based on how you add design variables.

• Output variables: it contains all the variables mention in the surfaceVariables option for solver. When the file is loaded, you will get a dictionary. The keys in the dictionary will depend on the entries in the surfaceVariables option. Value for each key is a numpy array. Refer below table for more information. n is the number of samples and k is the number of points (in surface or entire field).

  Possible value in surfaceVariables	Matching key in dictionary	Size
  rho	Density	n x k
  p	Pressure	n x k
  temp	Temperature	n x k
  cp	CoefPressure	n x k
  ptloss	RelativePressureStagnationLoss	n x k
  mach	Mach	n x k
  cf	SkinFrictionMagnitude	n x k
  ch	StantonNumber	n x k
  yplus	YPlus	n x k
  yplus	YPlus	n x k
  vx, vy, vz	Velocity	n x k x 3
  cfx, cfy, cfz	SkinFriction	n x k x 3

  Following snippet shows how to access few of those variables:

  from scipy.io import loadmat
  data = loadmat("fieldData.mat") # mention the location of mat file
  
  x = data["x"]
  mach = data["Mach"]
  cp = data["CoefPressure"]
  velocity = data["Velocity"]