Simulations

Simulations Module

class uconnrcmpy.simulations.Simulation(initial_temperature, initial_pressure, volume, is_reactive, end_temp=2500.0, end_time=0.2, chem_file=’species.cti’, cti_source=None)

Contains a single simulation of the experiment.

Parameters:
  • initial_temperature (float) – The initial temperature of the simulation
  • initial_pressure (float) – The initial pressure of the simulation
  • volume (numpy.ndarray or None) – The volume trace to be used for the simulation. Must be supplied, but if the input value is None, the volume trace will be read from the file volume.csv. The first column should be the time, the second column should be the volume.
  • is_reactive (bool) – If the simulation should be reactive or non-reactive. If False sets the Cantera reaction rate multiplier to 0.0 via the set_multiplier function.
  • end_temp (float, optional) – Reactor temperature at which the simulation will be ended
  • end_time (float, optional) – Time at which the simulation will be ended
  • chem_file (str, optional) – String filename of the chemistry file to use
time

numpy.ndarray – Array of simulated time values

temperature

numpy.ndarray – Array of simulated temperature values

pressure

numpy.ndarray – Array of simulated pressure values

input_volume

numpy.ndarray – Array of input volume values

simulated_volume

numpy.ndarray – Array of simulated volume values

end_temp

float – Reactor temperature at which the simulation will be ended

end_time

float – Time at which the simulation will be ended

chem_file

str – String filename of the chemistry file to use

initial_temperature

float – The initial temperature of the simulation

initial_pressure

float – The initial pressure of the simulation

calculate_derivative(dep_var, indep_var)

Calculate the derivative.

Parameters:
  • dep_var (numpy.ndarray) – Dependent variable (e.g., the pressure)
  • indep_var (numpy.ndarray) – Independent variable (e.g., the time)
Returns:

1-D array containing the derivative
Return type:

numpy.ndarray

Notes

The derivative is calculated by computing the first-order Lagrange polynomial fit to the point under consideration and its nearest neighbors. The Lagrange polynomial is used because of the unequal spacing of the simulated data. The formula, from Chapra and Canale is:

\[ \begin{align}\begin{aligned}\left(\frac{dy}{dt}\right)_i = y_{i-1}\frac{(x_{i} - x_{i+1})}{(x_{i-1} - x_{i})(x_{i-1} - x_{i+1})} +\\y_{i}\frac{(2x_{i} - x_{i-1} - x_{i+1})}{(x_{i} - x_{i-1})(x_{i} - x_{i+1})} +\\y_{i+1}\frac{(x_{i} - x_{i-1})}{(x_{i+1} - x_{i-1})(x_{i+1} - x_{i})}\end{aligned}\end{align} \]
class uconnrcmpy.simulations.VolumeProfile(time, volume)

Set the velocity of the piston by using a user specified volume profile. The initialization and calling of this class are handled by the cantera.Func1 interface of Cantera.

The velocity is calculated by assuming a unit area and using the forward difference, calculated by numpy.diff. This function is only called once when the class is initialized at the beginning of a problem so it is efficient.

Parameters:
time

numpy.ndarray – Array of time values

volume

numpy.ndarray – Array of volume values

velocity

numpy.ndarray – Array of velocity values