Chapter 7. INPUT DESCRIPTION FOR IGNITION SUB-BLOCKS
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The number of sub-blocks in the computational domain where the static temperature (or power source) is set to a prescribed value, so as to cause ignition to take place, is designated in the "general input" section (BOUNDARY AND CUT CONTROL) by the parameter IGNITION SUB-BLOCKS (>= 0). The first line of input for this section is a comment line for comments about the input to follow (the $ delineator is not required). The sub-block is created as a subset of a grid block defined by a bounding box in computational space. This subset (or sub-block) is defined by the beginning and ending grid point indices specified in the I, J, and K directions.
Example: Comment line and ignition sub-block definition
| IGN S.B. | BLK | DIR1 | BEG | END | DIR2 | BEG | END | DIR3 | BEG | END | T/P-IGNITE |
| L.E. | 1 | I | MIN | 65 | J | MIN | MAX | K | MIN | MAX | 1800.0 |
Where:
IGN S.B.: CHARACTER STRING; Sub-block name. Up to 10 characters used to indicate where the sub-block is located. Not used by code; provided as a user convenience.
BLK:INTEGER; Block number of sub-block in which the static temperature (or power source) is to be prescribed.
DIR1:CHARACTER STRING; Direction "1" for defining the sub-block window.
I = I constant boundary
J = J constant boundary
K = K constant boundary
BEG:CHARACTER STRING; Grid point at which to begin sub-block which runs in the direction specified by DIR1.
MIN = Start at minimum index of DIR1
MAX = Start at maximum index of DIR1
25 = Start at index 25 of DIR1
END: CHARACTER STRING; Grid point at which to end sub-block which runs in the direction specified by DIR1.
MIN = End at minimum index of DIR1
MAX = End at maximum index of DIR1
65 = End at index 65 of DIR1
NOTE 1: BEG must be less than END by at least 1.
NOTE 2: The sequence (DIR1, BEG, END) is repeated twice, for DIR2 and DIR3.
T/P-IGNITE: REAL; Static temperature (positive value) or power source (negative value) to be set for all cells in the sub-block
NOTE: If T/P-IGNITE is positive (ignition temperature), then the value must be specified in units of Kelvin.
NOTE: If T/P-IGNITE is negative (ignition power), then the value must be specified in units of Watts.
T/P-IGNITE is imposed on the requested cells after each time step/iteration.
>If an ignition temperature is imposed, then the static temperature is introduced into each of the requested cells using the following procedure:
1) Compute the cell internal energy, e(Ts), from: e(Ts) = E(Ts) - 0.5*(u**2 + v**2 + w**2) - k
If an ignition power is imposed, then the specified power is introduced into each of the requested cells of the flow solution. The power entered is converted to a power per unit volume based on the total volume enclosed by the index window of the sub-block. The energy addition is imposed at each cell by multiplying this quantity by the local cell volume and flow time step. It is recommended that this option be used only in instances where the ignition process of a spark plug or some other similar power source is of interest.
2) Compute the cell static temperature, Ts, based on the cell static energy from: Ts = (hs(Ts) - e(Ts)) / Rgas
3) Enforce a new cell minimum static temperature, T, as the maximum of Ts and T-IGNITE from: T = max(T, T-IGNITE). NOTE: This allows T to become greater than T-IGNITE which allows the ignition mechanism to shut itself off once the cell gas mixture begins to burn.
4) Compute a new cell static enthalpy, hs(T), based on the enforced cell minimum static temperature.
5) Compute a new cell internal energy based on the enforced cell minimum static temperature: e(T) = hs(T) - Rgas*T
6) Compute a new cell total energy: E(T) = e(T) + 0.5*(u**2 + v**2 + w**2) + k
7) Compute the new cell gas hermodynamic properties (pressure, gamma, Cp, etc.)
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