def sink_radius(IC): """ Determine a reasonable sink radius for the star particles depending on the star system type (e.g., single star, binary, etc...) Parameters ---------- IC : IC object Returns ------- r_sink : SimArray Sink radius for star particles """ # Set up the sink radius starMode = IC.settings.physical.starMode.lower() if starMode == 'binary': binsys = IC.settings.physical.binsys #Set Sink Radius to be mass-weighted average of Roche lobes of two stars r1 = AddBinary.calcRocheLobe(binsys.m1/binsys.m2,binsys.a) r2 = AddBinary.calcRocheLobe(binsys.m2/binsys.m1,binsys.a) p = strip_units(binsys.m1/(binsys.m1 + binsys.m2)) r_sink = (r1*p) + (r2*(1.0-p)) else: r_sink = IC.pos.r.min() return r_sink
def snapshot_gen(ICobj): """ Generates a tipsy snapshot from the initial conditions object ICobj. Returns snapshot, param snapshot: tipsy snapshot param: dictionary containing info for a .param file Note: Code has been edited (dflemin3) such that now it returns a snapshot for a circumbinary disk where initial conditions generated assuming star at origin of mass M. After gas initialized, replaced star at origin with binary system who's center of mass lies at the origin and who's mass m1 +m2 = M """ print 'Generating snapshot...' # Constants G = SimArray(1.0,'G') # ------------------------------------ # Load in things from ICobj # ------------------------------------ print 'Accessing data from ICs' settings = ICobj.settings # snapshot file name snapshotName = settings.filenames.snapshotName paramName = settings.filenames.paramName # particle positions r = ICobj.pos.r xyz = ICobj.pos.xyz # Number of particles nParticles = ICobj.pos.nParticles # molecular mass m = settings.physical.m # star mass m_star = settings.physical.M.copy() # disk mass m_disk = ICobj.sigma.m_disk.copy() m_disk = match_units(m_disk, m_star)[0] # mass of the gas particles m_particles = m_disk / float(nParticles) # re-scale the particles (allows making of low-mass disk) m_particles *= settings.snapshot.mScale # ------------------------------------------------- # Assign output # ------------------------------------------------- print 'Assigning data to snapshot' # Get units all set up m_unit = m_star.units pos_unit = r.units if xyz.units != r.units: xyz.convert_units(pos_unit) # time units are sqrt(L^3/GM) t_unit = np.sqrt((pos_unit**3)*np.power((G*m_unit), -1)).units # velocity units are L/t v_unit = (pos_unit/t_unit).ratio('km s**-1') # Make it a unit, save value for future conversion v_unit_vel = v_unit #Ensure v_unit_vel is the same as what I assume it is. assert(np.fabs(AddBinary.VEL_UNIT-v_unit_vel)<AddBinary.SMALL),"VEL_UNIT not equal to ChaNGa unit! Why??" v_unit = pynbody.units.Unit('{0} km s**-1'.format(v_unit)) # Other settings metals = settings.snapshot.metals star_metals = metals # Generate snapshot # Note that empty pos, vel, and mass arrays are created in the snapshot snapshot = pynbody.new(star=1,gas=nParticles) snapshot['vel'].units = v_unit snapshot['eps'] = 0.01*SimArray(np.ones(nParticles+1, dtype=np.float32), pos_unit) snapshot['metals'] = SimArray(np.zeros(nParticles+1, dtype=np.float32)) snapshot['rho'] = SimArray(np.zeros(nParticles+1, dtype=np.float32)) snapshot.gas['pos'] = xyz snapshot.gas['temp'] = ICobj.T(r) snapshot.gas['mass'] = m_particles snapshot.gas['metals'] = metals snapshot.star['pos'] = SimArray([[ 0., 0., 0.]],pos_unit) snapshot.star['vel'] = SimArray([[ 0., 0., 0.]], v_unit) snapshot.star['mass'] = m_star snapshot.star['metals'] = SimArray(star_metals) # Estimate the star's softening length as the closest particle distance #snapshot.star['eps'] = r.min() # Make param file param = make_param(snapshot, snapshotName) param['dMeanMolWeight'] = m gc.collect() # CALCULATE VELOCITY USING calc_velocity.py. This also estimates the # gravitational softening length eps print 'Calculating circular velocity' preset = settings.changa_run.preset max_particles = global_settings['misc']['max_particles'] calc_velocity.v_xy(snapshot, param, changa_preset=preset, max_particles=max_particles) gc.collect() # ------------------------------------------------- # Estimate time step for changa to use # ------------------------------------------------- # Save param file configsave(param, paramName, 'param') # Save snapshot snapshot.write(filename=snapshotName, fmt=pynbody.tipsy.TipsySnap) # est dDelta dDelta = ICgen_utils.est_time_step(paramName, preset) param['dDelta'] = dDelta # ------------------------------------------------- # Create director file # ------------------------------------------------- # largest radius to plot r_director = float(0.9 * r.max()) # Maximum surface density sigma_min = float(ICobj.sigma(r_director)) # surface density at largest radius sigma_max = float(ICobj.sigma.input_dict['sigma'].max()) # Create director dict director = make_director(sigma_min, sigma_max, r_director, filename=param['achOutName']) ## Save .director file #configsave(director, directorName, 'director') #Now that velocities and everything are all initialized for gas particles, create new snapshot to return in which #single star particle is replaced by 2, same units as above snapshotBinary = pynbody.new(star=2,gas=nParticles) snapshotBinary['eps'] = 0.01*SimArray(np.ones(nParticles+2, dtype=np.float32), pos_unit) snapshotBinary['metals'] = SimArray(np.zeros(nParticles+2, dtype=np.float32)) snapshotBinary['vel'].units = v_unit snapshotBinary['pos'].units = pos_unit snapshotBinary['mass'].units = snapshot['mass'].units snapshotBinary['rho'] = SimArray(np.zeros(nParticles+2, dtype=np.float32)) #Assign gas particles with calculated/given values from above snapshotBinary.gas['pos'] = snapshot.gas['pos'] snapshotBinary.gas['vel'] = snapshot.gas['vel'] snapshotBinary.gas['temp'] = snapshot.gas['temp'] snapshotBinary.gas['rho'] = snapshot.gas['rho'] snapshotBinary.gas['eps'] = snapshot.gas['eps'] snapshotBinary.gas['mass'] = snapshot.gas['mass'] snapshotBinary.gas['metals'] = snapshot.gas['metals'] #Load Binary system obj to initialize system binsys = ICobj.settings.physical.binsys x1,x2,v1,v2 = binsys.generateICs() #Put velocity in sim units #!!! Note: v_unit_vel will always be 29.785598165 km/s when m_unit = Msol and r_unit = 1 AU in kpc!!! #conv = v_unit_vel #km/s in sim units #v1 /= conv #v2 /= conv #Assign position, velocity assuming CCW orbit snapshotBinary.star[0]['pos'] = SimArray(x1,pos_unit) snapshotBinary.star[0]['vel'] = SimArray(v1,v_unit) snapshotBinary.star[1]['pos'] = SimArray(x2,pos_unit) snapshotBinary.star[1]['vel'] = SimArray(v2,v_unit) #Set stellar masses #Set Mass units #Create simArray for mass, convert units to simulation mass units priMass = SimArray(binsys.m1,m_unit) secMass = SimArray(binsys.m2,m_unit) snapshotBinary.star[0]['mass'] = priMass snapshotBinary.star[1]['mass'] = secMass snapshotBinary.star['metals'] = SimArray(star_metals) #Estimate stars' softening length as fraction of distance to COM d = np.sqrt(AddBinary.dotProduct(x1-x2,x1-x2)) snapshotBinary.star[0]['eps'] = SimArray(math.fabs(d)/4.0,pos_unit) snapshotBinary.star[1]['eps'] = SimArray(math.fabs(d)/4.0,pos_unit) print 'Wrapping up' # Now set the star particle's tform to a negative number. This allows # UW ChaNGa treat it as a sink particle. snapshotBinary.star['tform'] = -1.0 #Set Sink Radius to be mass-weighted average of Roche lobes of two stars r1 = AddBinary.calcRocheLobe(binsys.m1/binsys.m2,binsys.a) r2 = AddBinary.calcRocheLobe(binsys.m2/binsys.m1,binsys.a) p = strip_units(binsys.m1/(binsys.m1 + binsys.m2)) r_sink = (r1*p) + (r2*(1.0-p)) param['dSinkBoundOrbitRadius'] = r_sink param['dSinkRadius'] = r_sink param['dSinkMassMin'] = 0.9 * strip_units(secMass) param['bDoSinks'] = 1 return snapshotBinary, param, director