Cantera  2.0
GasTransport.h
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1 /**
2  * @file GasTransport.h
3  */
4
5 #ifndef CT_GAS_TRANSPORT_H
6 #define CT_GAS_TRANSPORT_H
7
8 #include "TransportBase.h"
9
10 namespace Cantera {
11
12 //! Class GasTransport implements some functions and properties that are
13 //! shared by the MixTransport and MultiTransport classes.
14 class GasTransport : public Transport
15 {
16 public:
17  virtual ~GasTransport() {}
18  GasTransport(const GasTransport& right);
19  GasTransport& operator=(const GasTransport& right);
20
21  //! Viscosity of the mixture (kg /m /s)
22  /*!
23  * The viscosity is computed using the Wilke mixture rule (kg /m /s)
24  *
25  * \f[
26  * \mu = \sum_k \frac{\mu_k X_k}{\sum_j \Phi_{k,j} X_j}.
27  * \f]
28  *
29  * Here \f$\mu_k \f$ is the viscosity of pure species \e k, and
30  *
31  * \f[
32  * \Phi_{k,j} = \frac{\left[1
33  * + \sqrt{\left(\frac{\mu_k}{\mu_j}\sqrt{\frac{M_j}{M_k}}\right)}\right]^2}
34  * {\sqrt{8}\sqrt{1 + M_k/M_j}}
35  * \f]
36  *
37  * @return Returns the viscosity of the mixture ( units = Pa s = kg /m /s)
38  *
39  * @see updateViscosity_T();
40  */
41  virtual doublereal viscosity();
42
43  //! Get the pure-species viscosities
44  virtual void getSpeciesViscosities(doublereal* const visc) {
45  update_T();
47  std::copy(m_visc.begin(), m_visc.end(), visc);
48  }
49
50  //! Returns the matrix of binary diffusion coefficients.
51  /*!
52  * d[ld*j + i] = rp * m_bdiff(i,j);
53  *
54  * @param ld offset of rows in the storage
55  * @param d output vector of diffusion coefficients. Units of m**2 / s
56  */
57  virtual void getBinaryDiffCoeffs(const size_t ld, doublereal* const d);
58
59  //! Returns the Mixture-averaged diffusion coefficients [m^2/s].
60  /*!
61  * Returns the mixture averaged diffusion coefficients for a gas,
62  * appropriate for calculating the mass averaged diffusive flux with respect
63  * to the mass averaged velocity using gradients of the mole fraction.
64  * Note, for the single species case or the pure fluid case the routine
65  * returns the self-diffusion coefficient. This is needed to avoid a Nan
66  * result in the formula below.
67  *
68  * This is Eqn. 12.180 from "Chemically Reacting Flow"
69  *
70  * \f[
71  * D_{km}' = \frac{\left( \bar{M} - X_k M_k \right)}{ \bar{\qquad M \qquad } } {\left( \sum_{j \ne k} \frac{X_j}{D_{kj}} \right) }^{-1}
72  * \f]
73  *
74  * @param[out] d Vector of mixture diffusion coefficients, \f$D_{km}' \f$ ,
75  * for each species (m^2/s). length m_nsp
76  */
77  virtual void getMixDiffCoeffs(doublereal* const d);
78
79  //! Returns the mixture-averaged diffusion coefficients [m^2/s].
80  //! These are the coefficients for calculating the molar diffusive fluxes
81  //! from the species mole fraction gradients, computed according to
82  //! Eq. 12.176 in "Chemically Reacting Flow":
83  //!
84  //! \f[ D_{km}^* = \frac{1-X_k}{\sum_{j \ne k}^K X_j/\mathcal{D}_{kj}} \f]
85  //!
86  //! @param[out] d vector of mixture-averaged diffusion coefficients for
87  //! each species, length m_nsp.
88  virtual void getMixDiffCoeffsMole(doublereal* const d);
89
90  //! Returns the mixture-averaged diffusion coefficients [m^2/s].
91  //! These are the coefficients for calculating the diffusive mass fluxes
92  //! from the species mass fraction gradients, computed according to
93  //! Eq. 12.178 in "Chemically Reacting Flow":
94  //!
95  //! \f[ \frac{1}{D_{km}} = \sum_{j \ne k}^K \frac{X_j}{\mathcal{D}_{kj}} +
96  //! \frac{X_k}{1-Y_k} \sum_{j \ne k}^K \frac{Y_j}{\mathcal{D}_{kj}} \f]
97  //!
98  //! @param[out] d vector of mixture-averaged diffusion coefficients for
99  //! each species, length m_nsp.
100  virtual void getMixDiffCoeffsMass(doublereal* const d);
101
102 protected:
104
105  virtual bool initGas(GasTransportParams& tr);
106  virtual void update_T();
107  virtual void update_C() = 0;
108
109  //! Update the temperature-dependent viscosity terms.
110  /**
111  * Updates the array of pure species viscosities, and the weighting
112  * functions in the viscosity mixture rule. The flag m_visc_ok is set to true.
113  *
114  * The formula for the weighting function is from Poling and Prausnitz,
115  * Eq. (9-5.14):
116  * \f[
117  * \phi_{ij} = \frac{ \left[ 1 + \left( \mu_i / \mu_j \right)^{1/2} \left( M_j / M_i \right)^{1/4} \right]^2 }
118  * {\left[ 8 \left( 1 + M_i / M_j \right) \right]^{1/2}}
119  * \f]
120  */
121  virtual void updateViscosity_T();
122
123  //! Update the pure-species viscosities. These are evaluated from the
124  //! polynomial fits of the temperature and are assumed to be independent
125  //! of pressure.
127
128  //! Update the binary diffusion coefficients
129  /*!
130  * These are evaluated from the polynomial fits of the temperature at the unit pressure of 1 Pa.
131  */
132  virtual void updateDiff_T();
133
134  //! Vector of species mole fractions. These are processed so that all mole
135  //! fractions are >= MIN_X. Length = m_kk.
137
138  //! Internal storage for the viscosity of the mixture (kg /m /s)
139  doublereal m_viscmix;
140
141  //! Update boolean for mixture rule for the mixture viscosity
142  bool m_visc_ok;
143
144  //! Update boolean for the weighting factors for the mixture viscosity
146
147  //! Update boolean for the species viscosities
149
150  //! Update boolean for the binary diffusivities at unit pressure
152
153  //! Type of the polynomial fits to temperature. CK_Mode means Chemkin mode.
154  //! Currently CA_Mode is used which are different types of fits to temperature.
155  int m_mode;
156
157  //! m_phi is a Viscosity Weighting Function. size = m_nsp * n_nsp
159
160  //! work space length = m_kk
162
163  //! vector of species viscosities (kg /m /s). These are used in Wilke's
164  //! rule to calculate the viscosity of the solution. length = m_kk.
166
167  //! Polynomial fits to the viscosity of each species. m_visccoeffs[k] is
168  //! the vector of polynomial coefficients for species k that fits the
169  //! viscosity as a function of temperature.
170  std::vector<vector_fp> m_visccoeffs;
171
172  //! Local copy of the species molecular weights.
174
175  //! Holds square roots of molecular weight ratios
176  /*!
177  * m_wratjk(j,k) = sqrt(mw[j]/mw[k]) j < k
178  * m_wratjk(k,j) = sqrt(sqrt(mw[j]/mw[k])) j < k
179  */
181
182  //! Holds square roots of molecular weight ratios
183  /*!
184  * m_wratjk1(j,k) = sqrt(1.0 + mw[k]/mw[j]) j < k
185  */
187
188  //! vector of square root of species viscosities sqrt(kg /m /s). These are
189  //! used in Wilke's rule to calculate the viscosity of the solution.
190  //! length = m_kk.
192
193  //! Powers of the ln temperature, up to fourth order
195
196  //! Current value of the temperature at which the properties in this object
197  //! are calculated (Kelvin).
198  doublereal m_temp;
199
200  //! Current value of Boltzman's constant times the temperature (Joules)
201  doublereal m_kbt;
202
203  //! current value of Boltzman's constant times the temperature.
204  //! (Joules) to 1/2 power
205  doublereal m_sqrt_kbt;
206
207  //! current value of temperature to 1/2 power
208  doublereal m_sqrt_t;
209
210  //! Current value of the log of the temperature
211  doublereal m_logt;
212
213  //! Current value of temperature to 1/4 power
214  doublereal m_t14;
215
216  //! Current value of temperature to the 3/2 power
217  doublereal m_t32;
218
219  //! Polynomial fits to the binary diffusivity of each species
220  /*!
221  * m_diffcoeff[ic] is vector of polynomial coefficients for species i species j
222  * that fits the binary diffusion coefficient. The relationship between i
223  * j and ic is determined from the following algorithm:
224  *
225  * int ic = 0;
226  * for (i = 0; i < m_nsp; i++) {
227  * for (j = i; j < m_nsp; j++) {
228  * ic++;
229  * }
230  * }
231  */
232  std::vector<vector_fp> m_diffcoeffs;
233
234  //! Matrix of binary diffusion coefficients at the reference pressure and the current temperature
235  //! Size is nsp x nsp.
237 };
238
239 } // namespace Cantera
240
241 #endif