Parasol Example

Parasol is a Framework for Parametric Model Investigation.

See the Docs at: http://parasol.readthedocs.org/en/latest/

Parasol enables easy optimization, sensitivity study, and visualization.

For this example, Parasol was used along with RocketCEA to evaluate sea level performance of a rocket engine.

from math import *
from parasol import *
from rocketcea.cea_obj import CEA_Obj

# create system object (make sure author is correct... it's used for report)
S = ParametricSoln(subtaskName="Nozzle Area Ratio", 
    author="Charlie Taylor", taskName="System Analysis", constraintTolerance=0.001)

fuelName = 'LH2'
oxName = 'LOX'
pcRef=1488.0 
epsRef = 21.5
MR=6.0

ispODEObj = CEA_Obj(fuelName=fuelName, oxName=oxName, useFastLookup=0)

ispODEref,cstrODEref,tcODEref = ispODEObj.get_IvacCstrTc( Pc=pcRef, MR=MR, eps=epsRef)

# add design variables to the system (these variables may be used to
# optimize the system or to create plots)
# design vars have: 
#     name, value, minVal, maxVal, NSteps,  units,  description
S.addDesVars(
    ['Pc',1500,1400,3000,60,'psia','Chamber Pressure'],
    ['eps',20,10,60,60,'','Nozzle Area Ratio'],
    )


# now add any Result Variables That might be plotted
# "sysMass" is required
# result variables have: 
#    name,      units,  description
S.addResultVars(
    ['IspVac','sec','Vacuum Isp'],
    ['Pexit','psia','Nozzle Exit Pressure'],
    ['IspSL','sec','Sea Level Isp'],
    )


# the following control routine ties together the system components
#  with the system design variables
def myControlRoutine(S):
    # get current values of design variables    
    Pc,eps = S.getDesVars("Pc","eps")
    
    ispODE,cstrODE,tcODE = ispODEObj.get_IvacCstrTc( Pc=Pc, MR=MR, eps=eps)
    PcOvPe = ispODEObj.get_PcOvPe( Pc=Pc, MR=MR, eps=eps)

    IspVac = ispODE
    Pexit = Pc / PcOvPe
    
    IspSL, mode = ispODEObj.estimate_Ambient_Isp(Pc=Pc, MR=MR, eps=eps, Pamb=14.7)

    S["IspVac"] = IspVac
    S["IspSL"] = IspSL
    S["Pexit"] = Pexit
    
    if IspVac < IspSL:
        mode = mode + '<<ERROR>>'
        print('Pc=%4i  eps=%3i  IspAmb=%10.2f IspVac=%10.2f  Mode=%s'%(int(Pc),int(eps), IspSL, IspVac, mode))

# need to tell system the name of the control routine
S.setControlRoutine(myControlRoutine)

make2DPlot(S, sysParam=["IspVac","IspSL"], desVar="eps", dpi=100,
           titleStr="Vacuum and Sea Level Isp for %s"%ispODEObj.desc)

make2DParametricPlot(S, sysParam="IspVac", desVar="Pc", dpi=100,
    paramVar=["eps",10., 15., 20., 30., 40.],  linewidth=2,
    titleStr="Vacuum Isp for %s"%ispODEObj.desc)


make2DParametricPlot(S, sysParam="IspSL", desVar="Pc", dpi=100,
    paramVar=["eps",10., 15., 20., 30., 40.]  ,linewidth=2,
    titleStr="Sea Level Isp for %s"%ispODEObj.desc)


make2DParametricPlot(S, sysParam="Pexit", desVar="Pc", dpi=100,
    paramVar=["eps",10., 15., 20., 30., 40.]  ,linewidth=2)


makeCarpetPlot(S, sysParam="IspVac", 
    desVarL=[["eps",10., 15., 20., 30., 40.],["Pc",1000.,2000.,3000.]], 
    xResultVar="Pexit",
    haLabel='center', vaLabel='center', dpi=100,
    titleStr="Vacuum Isp and Nozzle Exit Pressure for %s"%ispODEObj.desc)


makeCarpetPlot(S, sysParam="IspSL", 
    desVarL=[["eps",10., 15., 20., 30., 40.],["Pc",1500.,2000.,3000.]], 
    xResultVar="Pexit",
    haLabel='center', vaLabel='center', dpi=100,
    titleStr="Sea Level Isp and Nozzle Exit Pressure for %s"%ispODEObj.desc)


makeCarpetPlot(S, sysParam="IspSL", 
    desVarL=[["eps",10., 15., 20., 30., 40.],["Pc",1500.,2000.,3000.]], 
    xResultVar="IspVac",
    haLabel='center', vaLabel='center', dpi=100,
    titleStr="Sea Level and Vacuum Isp for %s"%ispODEObj.desc)


# now save summary of system
S.saveFullSummary()

# Be sure to wrap-up any files
S.close()

The output below is from a Parasol run that uses RocketCEA to evaluate sea level performance.

System Analysis
Nozzle Area Ratio	ParametricSoln v0.1.12
by: Charlie Taylor	May 19, 2018

Design Variables (nominal values) Name Value Units Description Pc 1500 psia Chamber Pressure (psia)

Design Variable Summary
Design Variables (nominal values) Name Value Units Description Pc 1500 psia Chamber Pressure (psia) eps 20 Nozzle Area Ratio Result Variables Name Value Units Description Low Limit High Limit IspSL 390.646 sec Sea Level Isp (sec) --- --- IspVac 436.348 sec Vacuum Isp (sec) --- --- Pexit 8.07005 psia Nozzle Exit Pressure (psia) --- ---

Parametric Solutions parasol v0.1.12 contact: C. Taylor, cet@appliedpython.com