pressure_change.cpp

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/* This file is part of Cloudy and is copyright (C)1978-2022 by Gary J. Ferland and
 * others.  For conditions of distribution and use see copyright notice in license.txt */
/*PressureChange called by ConvPresTempEdenIoniz
 * evaluate the current pressure, density change needed to get it to converge,
 * applies this correction factor to all gas constituents,
 * sets conv.lgConvPres true if good pressure, false if pressure change capped */
/*lgConvPres finds amount by which density should change to move towards pressure equilibrium
 * returns true if pressure is converged */
#include "cddefines.h"

#include "pressure_change.h"

#include "colden.h"
#include "conv.h"
#include "cosmology.h"
#include "dark_matter.h"
#include "dense.h"
#include "dynamics.h"
#include "geometry.h" 
#include "phycon.h"
#include "pressure.h"
#include "radius.h"
#include "struc.h"
#include "thermal.h"
#include "trace.h"
#include "wind.h"

/* zoneDensity finds density where prescribed */
double zoneDensity()
{
        double new_density;

        DEBUG_ENTRY( "zoneDensity()" );

        pressure.PresTotlError = 0.;

        /* evaluate a series of possible options, and set new_density */
        /* inside out globule */
        if( strcmp(dense.chDenseLaw,"GLOB") == 0 )
        {
                /* GLBDST is distance from globule, or glbrad-DEPTH */
                if( radius.glbdst < 0. )
                {
                        fprintf( ioQQQ, " Globule distance is negative, internal overflow has occured,  sorry.\n" );
                        fprintf( ioQQQ, " This is routine lgConvPres, GLBDST is%10.2e\n", 
                          radius.glbdst );
                        cdEXIT(EXIT_FAILURE);
                }
                new_density = 
                        (radius.glbden*pow(radius.glbrad/(radius.glbdst),radius.glbpow))*
                        (scalingDensity()/dense.gas_phase[ipHYDROGEN]);
        }
        else if( cosmology.lgDo )
        {
                /* cosmological - density varies because of expansion of universe */
                double dnew = GetDensity( cosmology.redshift_current );
                new_density = dnew*(scalingDensity()/dense.gas_phase[ipHYDROGEN]);
        }
        else if( (strcmp(dense.chDenseLaw,"WIND") == 0) ) {

                if ( wind.lgStatic() )
                {
                        fprintf( ioQQQ, " PROBLEM WIND called with zero velocity - this is impossible.\n Sorry.\n" );
                        TotalInsanity();
                }
                
                /* this is positive wind velocity the outflowing wind beyond sonic point */
                else if( wind.lgBallistic() )
                {
                        
                        /* this is logic for supersonic wind solution,
                         * well above sonic point. */
                        if( nzone > 1 )
                        {
                                /* Wind model */
                                
                                if( trace.lgTrace && trace.lgWind )
                                {
                                        fprintf(ioQQQ," lgConvPres sets AccelGravity %.3e lgDisk?%c\n",
                                                          wind.AccelGravity , 
                                                          TorF(wind.lgDisk) );
                                }
                                
                                /* following is form of constant acceleration equation, v^2 = u^2 + 2 a s
                                 * struc.windv[nzone-2] is velocity of previous zone
                                 * this increments that velocity to form square of new wind 
                                 * velocity for outer edge of this zone */
                                double term = POW2(struc.windv[nzone-2]) + 2.*(wind.AccelTotalOutward - wind.AccelGravity)* radius.drad;
                                
                                /* increment velocity if it is substantially positive */
                                fixit("RHS of comparison should be ~ sound speed squared");
                                if( term <= 1e3 )
                                {
                                        /* wind velocity is well below sonic point, give up, 
                                         * do not change velocity */
                                        wind.lgVelPos = false;
                                }
                                else
                                {
                                        /* wind.windv is velocity at OUTER edge of this zone */
                                        term = sqrt(term);
                                        if (wind.windv > 0)
                                        {
                                                wind.windv = (realnum) term;
                                        }
                                        else
                                        {
                                                wind.windv = -(realnum) term;
                                        }
                                        wind.lgVelPos = true;
                                }
                                
                                if( trace.lgTrace && trace.lgWind )
                                {
                                        fprintf(ioQQQ," lgConvPres new wind V zn%li %.3e AccelTotalOutward %.3e AccelGravity %.3e\n",
                                                          nzone,wind.windv, wind.AccelTotalOutward, wind.AccelGravity );
                                }
                        }
                        
                        /* conservation of mass sets density here */
                        new_density = wind.emdot/(wind.windv*radius.r1r0sq) * 
                                (scalingDensity()/dense.gas_phase[ipHYDROGEN]);
                }
                else
                {
                        fprintf(ioQQQ,"chDenseLaw==\"WIND\" must now be ballistic or static\n");
                        TotalInsanity();
                }
        }

        else if( strcmp(dense.chDenseLaw,"SINE") == 0 )
        {
                /* rapid density fluctuation */
                if( dense.lgDenFlucRadius )
                {
                        new_density = 
                                (dense.cfirst*cos(radius.depth*dense.flong+dense.flcPhase) + 
                                 dense.csecnd)*(scalingDensity()/dense.gas_phase[ipHYDROGEN]);
                }
                else
                {
                        new_density = 
                                (dense.cfirst*cos(colden.colden[ipCOL_HTOT]*dense.flong+dense.flcPhase) + 
                                 dense.csecnd)*(scalingDensity()/dense.gas_phase[ipHYDROGEN]);
                }
        }

        else if( strcmp(dense.chDenseLaw,"POWR") == 0 )
        {
                /* power law function of radius */
                double dnew = dense.den0*pow(radius.Radius/radius.rinner,(double)dense.DensityPower);
                new_density = dnew*(scalingDensity()/dense.gas_phase[ipHYDROGEN]);
        }

        else if( strcmp(dense.chDenseLaw,"POWD") == 0 )
        {
                /* power law function of depth */
                double dnew = dense.den0*pow(1. + radius.depth/dense.rscale,(double)dense.DensityPower);
                new_density = dnew*(scalingDensity()/dense.gas_phase[ipHYDROGEN]);
        }

        else if( strcmp(dense.chDenseLaw,"POWC") == 0 )
        {
                /* power law function of column density */
                double dnew = dense.den0*pow(1.f + colden.colden[ipCOL_HTOT]/
                  dense.rscale,dense.DensityPower);
                new_density = dnew*(scalingDensity()/dense.gas_phase[ipHYDROGEN]);
        }


        else if( strncmp( dense.chDenseLaw ,"DLW" , 3) == 0 )
        {
                if( strcmp(dense.chDenseLaw,"DLW1") == 0 )
                {
                        /* call ACF sub */
                        new_density = 
                                dense_fabden(radius.Radius,radius.depth)*
                                (scalingDensity()/dense.gas_phase[ipHYDROGEN]);
                }
                else if( strcmp(dense.chDenseLaw,"DLW2") == 0 )
                {
                        /* call table interpolation subroutine
                         * >>chng 96 nov 29, added dense_tabden */
                        new_density = dense.DLW.tabval(radius.Radius,radius.depth) *
                                (scalingDensity()/dense.gas_phase[ipHYDROGEN]);
                }
                else if( strcmp(dense.chDenseLaw,"DLW3") == 0 )
                {
                        /* call parametrized wind subroutine */
                        new_density = dense_parametric_wind(radius.Radius) *
                                (scalingDensity()/dense.gas_phase[ipHYDROGEN]);
                }
                else
                {
                        fprintf( ioQQQ, " Insanity, lgConvPres gets chCPres=%4.4s\n", 
                          dense.chDenseLaw );
                        cdEXIT(EXIT_FAILURE);
                }

                if( new_density/scalingDensity() > 3. || new_density/scalingDensity()< 1./3 )
                {
                        static bool lgWARN2BIG=false;
                        if( !lgWARN2BIG )
                        {
                                lgWARN2BIG = true;
                                fprintf(ioQQQ,"\n\n >========== Warning!  The tabulated or functional change in density as a function of depth was VERY large. This is zone %li.\n",nzone);
                                fprintf(ioQQQ," >========== Warning!  This will cause convergence problems. \n");
                                fprintf(ioQQQ," >========== Warning!  The current radius is %.3e. \n",radius.Radius);
                                fprintf(ioQQQ," >========== Warning!  The current depth is %.3e. \n",radius.depth);
                                fprintf(ioQQQ," >========== Warning!  Consider using a more modest change in density vs radius. \n\n\n");
                        }
                }
        }

        else if( strcmp(dense.chDenseLaw,"CDEN") == 0 )
        {
                /* this is the default, constant density */
                new_density = scalingDensity();
        }

        else
        {
                fprintf( ioQQQ, " Unknown density law=%s= This is a major internal error.\n", 
                  dense.chDenseLaw );
                ShowMe();
                cdEXIT(EXIT_FAILURE);
        }

        return new_density;
}

enum {
        CPRE,
        SUBSONIC,
        SUPERSONIC,
        STRONGD,
        ORIGINAL,
        SHOCK,
        ANTISHOCK,
        ANTISHOCK2
};

STATIC double stepDensity(const PresMode & presmode, solverState &st);

STATIC void logPressureState()
{
        /* >>chng 04 feb 11, add option to remember current density and pressure */
        conv.hist_pres_density.push_back( dense.gas_phase[ipHYDROGEN] );
        conv.hist_pres_current.push_back( pressure.PresTotlCurr );
        conv.hist_pres_error.push_back( pressure.PresTotlError );
}

STATIC bool lgTestPressureConvergence( double new_density)
{
        double density_change_factor = new_density/scalingDensity();

        /* now see whether current pressure is within error bounds */
        if( density_change_factor > 1. + conv.PressureErrorAllowed || 
                 density_change_factor < 1. - conv.PressureErrorAllowed )
        {
                return false;
        }
        else
        {
                return true;
        }
}

STATIC double limitedDensityScaling( double new_density, double dP_chng_factor )
{
        double density_change_factor = new_density/scalingDensity()-1.;

        /* dP_chng_factor is initially 1, becomes smaller if sign of pressure change, changes */
        double pdelta = conv.MaxFractionalDensityStepPerIteration;

        /* make sure that change is not too extreme */
        density_change_factor *= dP_chng_factor;
        density_change_factor = MIN2(density_change_factor,+pdelta);
        density_change_factor = MAX2(density_change_factor,-pdelta);
        return 1.+density_change_factor;
}

/*PressureChange evaluate the current pressure, and change needed to
 * get it to PresTotlInit,
 * return value is true if density was changed, false if no changes were necessary */
void PressureChange( 
        /* this is change factor, 1 at first, becomes smaller as oscillations occur */
        double dP_chng_factor, const PresMode & presmode, solverState &st, 
        bool& lgAbort, bool &lgStable )
{
        DEBUG_ENTRY( "PressureChange()" );

        lgAbort = false;

        /* first evaluate total pressure for this location, and current conditions
         * CurrentPressure is just sum of gas plus local line radiation pressure */
        /* this sets values of pressure.PresTotlCurr, also wind velocity for dynamics */
        PresTotCurrent();
        logPressureState();

        double old_density = scalingDensity();
        double old_pressure = pressure.PresTotlCurr;

        double new_density = stepDensity(presmode, st);

        conv.lgConvPres = lgTestPressureConvergence(new_density);

        double density_change_factor = limitedDensityScaling(new_density, dP_chng_factor);

        {
                /*@-redef@*/
                enum{DEBUG_LOC=false};
                static long int nsave=-1;
                /*@+redef@*/
                if( DEBUG_LOC /*&& nzone > 150 && iteration > 1*/ )
                {
                        if( nsave-nzone ) fprintf(ioQQQ,"\n");
                        nsave = nzone;
                        fprintf(ioQQQ,"nnzzone\t%li\t%.2f%%\t%.3f\t%.2e\t%.2e\t%.2e\n", 
                                nzone,
                                density_change_factor,
                                /* when this is negative we need to raise the density */
                                pressure.PresTotlError*100.,
                            pressure.PresTotlCurr, 
                                pressure.PresGasCurr,
                                pressure.pres_radiation_lines_curr );
                }
        }

        if( trace.lgTrace )
        {
                fprintf( ioQQQ, 
                  " PressureChange called, changing HDEN from %10.3e to %10.3e Set fill fac to %10.3e\n", 
                                        dense.gas_phase[ipHYDROGEN], density_change_factor*dense.gas_phase[ipHYDROGEN], 
                                        geometry.FillFac );
        }

        bool lgChange = ( density_change_factor != 1. );

        lgStable = true;
        if( lgChange )
        {
                ScaleAllDensities((realnum) density_change_factor);

                /* must call TempChange since ionization has changed, there are some
                 * terms that affect collision rates (H0 term in electron collision) */
                TempChange(phycon.te , false);

                /* heating cooling balance while doing ionization,
                 * this is where the heavy lifting is done, this calls PresTotCurrent,
                 * which sets pressure.PresTotlCurr */
                int lgTempStatus = ConvTempEdenIoniz();
                if( lgTempStatus != 0 )
                {
                        lgAbort = true;
                }
                double new_pressure = pressure.PresTotlCurr;
                double dpdrho = (new_pressure-old_pressure)/(new_density-old_density);
                double dpdrhoScale = (new_pressure+old_pressure)/(new_density+old_density);
                if ( presmode.zone == SUBSONIC)
                {
                        if ( dpdrho < -0.01*dpdrhoScale )
                                lgStable = false;
                }
                else if ( presmode.zone == SUPERSONIC)
                {
                        if ( dpdrho > 0.01*dpdrhoScale )
                                lgStable = false;
                }
                if (0)
                        fprintf(ioQQQ,"ConvPres STABLE??? nz %ld od %.2e nd %.2e eps %.2e op %.2e np %.2e dpdn %.2e cmp %.2e %c\n",
                                          nzone,old_density,new_density,new_density/old_density-1.0,
                                          old_pressure,new_pressure,dpdrho,dpdrhoScale,TorF(lgStable));
                if (0)
                        if (!lgStable)
                        {
                                conv.lgConvPres = false; // If evidence of instability found, ensure at least another iteration
                                fixit("Disabled test on stability"); 
                                // log zone warning when pressure instability diagnosed
                                // possibly reduce zone stepsize when close
                        }
        }

        {
                /*@-redef@*/
                enum {DEBUG_LOC=false};
                /*@+redef@*/
                if( DEBUG_LOC && (nzone>215) )
                {
                        fprintf( ioQQQ, 
                                "%.2e\t%.2e\t%.2e\t%.2e\t%.2e\t%.2e\t%.2e\t%.2e\t%.2e\t%.2e\t%c\n", 
                          radius.depth, 
                          pressure.PresTotlCurr, 
                          pressure.PresTotlInit + pressure.PresInteg, 
                          pressure.PresTotlInit, 
                          pressure.PresGasCurr, 
                          pressure.PresRamCurr, 
                          pressure.pres_radiation_lines_curr, 
                          /* subtract continuum rad pres which has already been added on */
                          pressure.PresInteg - pressure.pinzon, 
                          wind.windv/1e5,
                          sqrt(5.*pressure.PresGasCurr/3./dense.xMassDensity)/1e5,
                          TorF(conv.lgConvPres) );
                }
        }
}

/* ============================================================================== */
/* DynaPresChngFactor, called from PressureChange to evaluate factor needed
 * to find new density needed for 
 * current conditions and wind solution, returns ratio of new to old density */

/* object is to get the local ram pressure
 * RamNeeded = pressure.PresTotlInit + pressure.PresGasCurr + pressure.PresInteg;
 * to equal the sum of the inital pressur at the illuminated face, the local gas pressure,
 * and the integrate radiative acceleration from the incident continuum 
 *
 * the local gas pressure is linear in density if the temperature is constant,
 *
 * the local ram pressure is inversely linear in density because of the relationship
 * between velocity and density introduced by the mass flux conservation 
 */

/* stepDensity finds a density which should move towards pressure equilibrium
 * sets pressure.PresTotlError */
STATIC double stepDensity(const PresMode &presmode, solverState &st)
{
        DEBUG_ENTRY( "stepDensity()" );

        double PresTotlCorrect = st.press;
        
        double densityCurrent = scalingDensity();

        double er = pressure.PresTotlCurr-PresTotlCorrect;
        pressure.PresTotlError = er/PresTotlCorrect;

        if( trace.lgTrace && presmode.global != CPRE )
        {
                fprintf( ioQQQ, 
                                        " DynaPresChngFactor set PresTotlCorrect=%.3e PresTotlInit=%.3e PresInteg=%.3e DivergePresInteg=%.3e\n", 
                                        PresTotlCorrect , pressure.PresTotlInit , pressure.PresInteg*pressure.lgContRadPresOn,
                                        dynamics.DivergePresInteg );
        }
        
        if( dynamics.lgTracePrint && presmode.global != CPRE)
                fprintf(ioQQQ,"Pressure: init %g +rad %g +diverge %g = %g cf %g\n",
                                  pressure.PresTotlInit, pressure.PresInteg*pressure.lgContRadPresOn,
                                  dynamics.DivergePresInteg, PresTotlCorrect, pressure.PresTotlCurr);
        /*fprintf(ioQQQ,"DEBUG\t%.2f\thden\t%.4e\tPtot\t%.4e\tPgas\t%.4e\n",
          fnzone, scalingDensity(),pressure.PresTotlCurr,pressure.PresGasCurr );*/
        
        double rhohat, dpdrho;
        if( presmode.global == CPRE || presmode.global == ORIGINAL || 
                 st.lastzone != nzone || fabs(er-st.erp) < SMALLFLOAT
                 || fabs(densityCurrent-st.dp) < SMALLFLOAT) 
        {
                if ( presmode.zone == SUBSONIC ) 
                {
                        dpdrho = pressure.PresTotlCurr/densityCurrent;
                }
                else
                {
                        dpdrho = -pressure.PresTotlCurr/densityCurrent;
                }
                rhohat = densityCurrent - er/dpdrho;
        }
        else
        {
                /* second iteration on this zone, do linear fit to previous Pres - rho curve
                 * Linear approximation to guess root with two independent samples */
                dpdrho = (st.erp-er)/(st.dp-densityCurrent);
                rhohat = densityCurrent - er/dpdrho;

                /* Subsonic case: pressure ^ with density ^ => increase density further */
                /* Super "  case: pressure ^ with density v => decrease density further */
                
                /* Force the solution towards the required branch when it
                 * appears to have the "wrong" value of dP/drho */
                if(presmode.zone == SUBSONIC && dpdrho <= 0)
                {
                        if (er < 0.0)
                                rhohat = 1.03*densityCurrent;
                        else
                                rhohat = 0.97*densityCurrent;
                }
                else if(presmode.zone == SUPERSONIC && dpdrho >= 0)
                {
                        if (er > 0.0)
                                rhohat = 1.03*densityCurrent;
                        else
                                rhohat = 0.97*densityCurrent;
                }
        }
        
        st.dp = densityCurrent;
        st.erp = er;
        st.lastzone = nzone;
        
        if( presmode.global != CPRE && dynamics.lgTracePrint )
                fprintf(ioQQQ,"windv %li r %g v %g f %g\n",
                                  nzone,radius.depth,wind.windv,DynaFlux(radius.depth));
        
        /* convergence trace at this level */
        if( trace.nTrConvg>=1  )
        {
                if ( presmode.global == CPRE )
                {
                        fprintf( ioQQQ, 
                                                " PresChng %s density old %.3e new %.3e current %.3e correct %.3e dpdn %.3e\n",
                                                dynamics.chPresMode , densityCurrent, rhohat , pressure.PresTotlCurr,
                                                PresTotlCorrect, dpdrho
                                );
                }
                else
                {
                        fprintf( ioQQQ, 
                                                " DynaPresChngFactor mode %s new density %.3f vel %.3e\n",
                                                dynamics.chPresMode , rhohat , wind.windv );
                }
        }
        
        return rhohat;
}

void PresMode::set()
{
        DEBUG_ENTRY( "PresMode::set()" );
        /* dynamics.lgSetPresMode is flag to indicate sane value of dynamics.chPresMode.  
         * If set true with SET DYNAMICS PRESSURE MODE
         * then do not override that choice */
        if( !dynamics.lgSetPresMode )
        {
                /* above set true if pressure mode was set with
                 * SET DYNAMICS PRESSURE MODE - if we got here
                 * it was not set, and must make a guess */
                if(pressure.PresGasCurr < pressure.PresRamCurr)
                        strcpy( dynamics.chPresMode , "supersonic" );
                else
                        strcpy( dynamics.chPresMode , "subsonic" );
                /* clear the flag - pressure mode has been set */
                dynamics.lgSetPresMode = true;
        }
        
        /* if globally looking for transonic solution, then locally sometimes
         * supersonic, sometimes subsonic - this branch sets global flag,
         * which can also be set with SET DYNAMICS PRESSURE MODE.
         * Under default conditions, ChPresMode was set in previous branch
         * to sub or super sonic depending on current velocity on first time*/

        if (strcmp(dense.chDenseLaw,"CPRE") != 0)
        {
                ASSERT (strcmp(dense.chDenseLaw,"DYNA") == 0);
        }

        if (strcmp(dense.chDenseLaw,"CPRE") == 0)
        {
                global = CPRE;
                pressure.lgSonicPointAbortOK = false;
        }
        else if( strcmp( dynamics.chPresMode , "original" ) == 0 )
        {
                global = ORIGINAL;
                pressure.lgSonicPointAbortOK = true;
        }
        else if( strcmp( dynamics.chPresMode , "subsonic" ) == 0 )
        {
                global = SUBSONIC;
                pressure.lgSonicPointAbortOK = true;
        }
        /* supersonic */
        else if( strcmp( dynamics.chPresMode , "supersonic" ) == 0 )
        {
                global = SUPERSONIC;
                pressure.lgSonicPointAbortOK = true;
        }
        /* strong d */
        else if( strcmp( dynamics.chPresMode , "strongd" ) == 0 )
        {
                global = STRONGD;
                pressure.lgSonicPointAbortOK = false;
        }
        else if( strcmp( dynamics.chPresMode , "shock" ) == 0 )
        {
                global = SHOCK;
                pressure.lgSonicPointAbortOK = false;
        }
        else if( strcmp( dynamics.chPresMode , "antishock-by-mach" ) == 0 )
        {
                global = ANTISHOCK2;
                pressure.lgSonicPointAbortOK = false;
        }
        else if( strcmp( dynamics.chPresMode , "antishock" ) == 0 )
        {
                global = ANTISHOCK;
                pressure.lgSonicPointAbortOK = false;
        }
        
        /* this sets pressure mode for the current zone based on global mode
         * and local conditions */
        if(global == CPRE)
        {
                zone = SUBSONIC;
        } 
        else if(global == ORIGINAL)
        {
                /* in this mode use comparison between ram and gas pressure to determine
                 * whether sub or super sonic */
                if(pressure.PresGasCurr > pressure.PresRamCurr)
                {
                        zone = SUBSONIC;
                }
                else
                {
                        zone = SUPERSONIC;
                }
        }
        else if(global == STRONGD)
        {
                //if(nzone <= 1)
                zone = SUPERSONIC;
        }
        else if(global == SUBSONIC)
        {
                zone = SUBSONIC;
        }
        else if(global == SUPERSONIC)
        {
                zone = SUPERSONIC;
        }
        else if(global == SHOCK)
        {
                if(radius.depth < dynamics.ShockDepth)
                {
                        zone = SUBSONIC;
                }
                else
                {
                        zone = SUPERSONIC;
                }
        }
        else if(global == ANTISHOCK)
        {
                if(radius.depth < dynamics.ShockDepth)
                {
                        zone = SUPERSONIC;
                }
                else
                {
                        zone = SUBSONIC;
                }
        }
        else if(global == ANTISHOCK2)
        {
                /* WJH 19 May 2004: This version of the antishock mode will
                        insert the antishock at the point where the isothermal Mach
                        number falls below a certain value, dynamics.ShockMach */
                if( fabs(wind.windv) > dynamics.ShockMach*sqrt(pressure.PresGasCurr/dense.xMassDensity))
                {
                        zone = SUPERSONIC;
                }
                else
                {
                        zone = SUBSONIC;
                }
        }
        else
        {
                printf("Need to set global pressure mode\n");
                cdEXIT( EXIT_FAILURE );
        }
}

double pressureZone(const PresMode &presmode)
{
        DEBUG_ENTRY( "pressureZone()" );
        double press;
        if( presmode.global == CPRE )
        {
                /* constant pressure */
                if( pressure.lgContRadPresOn )
                {
                        /* >>chng 01 oct 31, replace pneed with CorretPressure */
                        /* this has pressure due to incident continuum */
                        press = pressure.PresTotlInit + pressure.PresInteg;
                }
                else
                {
                        /* this does not have pressure due to incident continuum*/
                        press = pressure.PresTotlInit*
                                /* following term normally unity, power law set with option par on cmmnd*/
                                pow(radius.Radius/radius.rinner,(double)pressure.PresPowerlaw);
                }

                if( dark.lgNFW_Set || pressure.gravity_symmetry >=0 )
                {
                        fixit("check correct zone pressure for NFW");
                        // doesn't this exclude current zone gravity pressure.RhoGravity?
                        // and doesn't the above exclude current rad press, pressure.pinzon?
                        // That would be a second order correction, which would need
                        // a consistent second order treatment elsewhere to make it
                        // worthwhile.
                        press += pressure.IntegRhoGravity;
                }
        }
        else 
        {
                /* update the current desired pressure */
                press = pressure.PresTotlInit + pressure.PresInteg*pressure.lgContRadPresOn
                        + dynamics.DivergePresInteg;
        }
        return press;
}