Changes between Version 7 and Version 8 of u/BonnorEbertModule
 Timestamp:
 10/04/12 17:52:46 (12 years ago)
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u/BonnorEbertModule
v7 v8 7 7 }}} 8 8 9 andr is the dimensional radius of the sphere, Cs is the isothermal sound speed of the sphere (function of the temperature), and rho_c is the central density of the sphere. Once the user specifies r, rho_c, and xi for the sphere (see next section), astrobear sets both a) the temperature of the sphere using the above equation, and b) the outer density of the sphere. One can then use the ideal EOS in physics.data with a gamma = 1.0001 to approximate the grid as isothermal. Given P = nKT, the pressure of the sphere then drops away from the center of the sphere with the same gradient as rho.9 , r is the dimensional radius of the sphere, Cs is the isothermal sound speed of the sphere (function of the temperature), and rho_c is the central density of the sphere. Once the user specifies r, rho_c, and xi for the sphere (see next section), astrobear sets both a) the temperature of the sphere using the above equation, and b) the outer density of the sphere. One can then use the ideal EOS in physics.data with a gamma = 1.0001 to approximate the grid as isothermal. Given P = nKT, the pressure of the sphere then drops away from the center of the sphere with the same gradient as rho. 10 10 11 Now, that (^) all explains the clump object itself, but there is an additional "object" in the BE problem module that controls the ambient medium in which the clump resides. This ambient object is by default set to have a uniform density, equal to the density at the sphere's outer most edge, rho(Rbe). Additionally, it is also in pressure equilibrium with the sphere. That is, Pamb=P(Rbe). Now, since the simulation is isothermal, this condition means the temperature is discontinuous at the sphereambient interface, given by P/n = KT, where n is the numberdensity of the gas.11 Now, that all explains the clump object itself, but there is an additional "object" in the BE problem module that controls the ambient medium in which the clump resides. This ambient object is by default set to have a uniform density, equal to the density at the sphere's outer most edge, rho(Rbe). Additionally, it is also in pressure equilibrium with the sphere by default. That is, Pamb=P(Rbe). Now, since the simulation is isothermal, this condition means the temperature is discontinuous at the sphereambient interface, given by P/n = KT, where n is the numberdensity of the gas. 12 12 13 13 To summarize, the BE sphere is a clump object that is intialized with the BE density profile. It is placed in an ambient medium object. How to control the different parameters of these objects is described next. … … 16 16 === Problem.data === 17 17 18 The BE module requires the following 3 parameters to set up a BE sphere on the grid:18 The BE module requires the following 3 userspecified parameters to set up a BE sphere on the grid: 19 19 20 20 1. '''central density''' of the sphere (''central_rho''), … … 22 22 3. '''dimensional radius''' (clump_rad). 23 23 24 These 3 parameters uniquely and completely specify a sphere in hydrostatic equilibrium as given by the Lane Emden equation (see). They are '''userspecified''' in problem.data.24 These 3 parameters are to be set in problem.data, and are the 3 ingredients that uniquely and completely specify the BE sphere ([wiki:u/BonnorEbert reference here]). 25 25 26 Now, to recap, the BE sphere is actually a clump object. It is co mpletely controlled external to problem.f90 by the input parameters in physics.data that all explains the initiation of the BE sphere, or clump object.26 Now, to recap, the BE sphere is actually a clump object. It is controlled externally from the problem.f90 file by specifying the parameters (13) above in physics.data. However, the controls for the ambient medium object are internal to the problem.f90 file. It's treatment is provided next. 27 27 28 === Ambient Object === 29 30 As stated above, the clump object is embedded inside another object, the ambient medium. This ambient medium begins outside of the clump, and the lines of code that initialize this object are described as follows. 28 31 29 32 === Units ===