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  • TEM1.HTM
    volume time interval specific heat temperature The thermal conductivity enters as a multiplier of the temperature gradient The energy equation in one dimension only to avoid needless repetition can thus be expressed symbolically as M Cp T Cp T dt m Cp T Cp T m Cp T Cp T A k dX T T A k dX T T So h 0 wherein refer to the and direction neighbour cells refers to values at the previous time step M is the mass of fluid in the cell at the previous time step m is a mass inflow rate which is either positive or zero A is a cell face area dX is the distance between cell centres k is the conductivity So in the energy source term Cp is an effective specific heat capacity and obedience to M dt m m 0 the mass balance equation is implied A dX and k are defined on the cell faces while all other quantities are defined at cell centres Upwinding is presumed The effective specific heat capacity must be defined in a such a way as to yield the correct enthalpy conservation equation i e so that the first two terms of the above equation are equivalent to M h h dt m h h m h h It follows that the effective specific heat capacity must be defined as Cp h Habs Tabs where Tabs is the temperature on an absolute scale i e degrees Kelvin or Rankine and Habs is the enthalpy of the material at the absolute zero See PHENC entry SPECIFIC HEATS Mass inflow boundary conditions When a mass inflow patch has a temperature condition expressed via COVAL patchname TEM1 ONLYMS Tin EARTH automatically multiplies the inflow temperature Tin by the specific heat which prevails in the

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/tem1.htm (2016-02-15)
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  • MAGIC.HTM
    the boundaries exhibit discontinuous changes in direction MAGIC T tends to propagate the discontinuities into the domain In such circumstances it may produce highly non orthogonal and hence undesirable grids MAGIC L solves differential equations for the corner coordinates within the currently active DOMAIN The solution starts from the existing grid however generated eg by MAGIC L MAGIC T or READCO MAGIC L involves the solution of Laplace like equations for the cartesian coordinates of the cell corners The finite difference equations solved for XC YC and ZC are expressed in linearized form so that they can be solved by means of linear equation solvers The non linearities of the equations find their expression in the coefficients of the linearized equations and consequently the coefficients require updating after each solution of the linearized system of equations The solution control parameters LITXC LITYC LITZC set the number of iterations of the linear equation solver for the coordinates XC YC and ZC The parameter MSWP sets the number of sweeps of the sub domain each sweep involving the update of the coefficients of the equations The progress to convergence of the iterative process can be monitored at the VDU at the location IMON JMON and KMON The linear solver can be over relaxed by RELXC RELYC RELZC Other parameters related to the use of MAGIC L are LIJ LJK LIK SLIDW SLIDE SLIDS SLIDN SLIDL SLIDH FIXCOR and FIXDOM The VIEW command permits the grid generated to be displayed The theory underlying MAGIC L xC yC and zC can be regarded as vectors and as such they can be subjected to the grad operator grad xC grad yC and grad zC are constant vectors the components of which are 1 0 0 0 1 0 and 0 0 1 respectively The divergence

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/magic.htm (2016-02-15)
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  • 4-fluid model
    The sources and sinks of the last panel were associated wih micro mixing ie with coupling and splitting In addition to these rates of production of one fluid and corresponding diminution of the others fluid D is produced from fluid C only at the rate MC CHEMRATE CHEMRATE is of course the rate of chemical conversion of the unburned fuel in fluid C to combustion products It is the element of the model which allows as EBU did not chemical kinetic effects to be introduced rationally e The first application of the 4 fluid model The first application of the 4 fluid model was to the same problem as that for which the EBU was invented namely that of steady turbulent flame spread in a plane walled duct Through the upstream end flows both a stream of unburned combustible mixture and a separate but thinner stream of fully burned products to serve as an igniter shown below STEADY TURBULENT FLAME SPREAD IN A PLANE WALLED DUCT ENTRANCE CHANNEL WALL EXIT UNBURNED GAS FLAME SPREADING TO WALL BURNED GAS SYMMETRY PLANE f Remarkable facts about the experimental findings Experiments of this kind by Hottel Scurlock and Williams 1954 have shown that the rate of spread of the flame as measured by its angle for a fixed inlet stream velocity is very little dependent on the fuel air ratio of the incoming mixture the flow velocity of the incoming mixture or the temperature of the incoming mixture However the flame can be suddenly extinguished if variations of any of these quantities becomes too extreme Note Strictly speaking Hottel et al used a bluff body flame holder rather that a co flowing igniting stream but the difference has little significance g The numerical simulation This process has been simulated by activating the 4 fluid model within the PHOENICS computer program operating in parabolic ie marching integration mode The magnitude of the MIXRATE quantity was computed in the same manner as for the eddy break up model ie as proportional to the square root of the turbulence energy divided by the length scale The findings were in accordance with experiments in that for a given MIXRATE the flame angle was almost independent of flow velocity or CHEMRATE but once CHEMRATE was made low enough flame propagation ceased The following pictures illustrate the predictions for a particular pair of MIXRATE and CHEMRATE values Flow is from left to right The top boundary of the diagram represents the duct wall The lower boundary represents the symmetry axis The contours are those of fluid A the unburned incoming fluid CHEMRATE here called chemfact is large This implies that the flame is mixing rate limited duct1 Flow is from left to right The top boundary of the diagram represents te duct wall The lower boundary represents the symmetry axis The contours are those of fluid D the products of combustion duct2 Flow is from left to right The top boundary of the diagram represents te duct wall The

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/turmod/enc_tu64.htm (2016-02-15)
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  • Generic interface for PHOENICS
    input and output translators are available from three sources As optional add ons to PHOENICS CHAM supplies input translators for Patran Algor and ICEM boundary conditions can also be input within the ICEM environment For visualisation of PHOENICS results CHAM currently supplies translators for TecPlot and Patran A number of third party code vendors offer input and output translators which link directly into the GENIE system These include FemSys Ltd and Numeca Intl SA who provide translators for their complete grid generation and results viewing systems FemGen FemView and IGG CFView The decision to incorporate GENIE into the standard PHOENICS package means that this environment is now available to all PHOENICS users to facilitate the linking of ANY commercial or in house finite element based code to PHOENICS On line documentation is provided within PHOENICS to assist in the creation of the necessary translators CHAM will also undertake to write special translators on a contract basis Both the PEN and NEP systems can be accessed as FORTRAN libraries or via their associated neutral files The function of the system is the same whether the data are passed via files or arrays 2 PEN The functions performed by the PEN system are Element based grids are converted into IJK structured blocks PHOENICS links are found for blocks created from element based grids or read in from IJK structured grid generators The blocks that are linked together are re oriented so they conform to the PHOENICS blocks stacking rules PATCHES for grids from IJK structured grid generators are reoriented if necessary Lists of nodes from element based grid generators are converted into PHOENICS patches Non geometric commands in an existing Q1 file can be appended to the Q1 files created by the PEN system 3 NEP The functions performed by the NEP

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_info/genie.htm (2016-02-15)
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  • THE GENTRA PARTICLE TRACKER
    d 3 4 k 3 2 e and C m C d 0 09 THE OVERALL SOLUTION ALGORITHM The gas and particle equations are solved separately using well known mathematical techniques However because the gas and particle equations are linked the solution procedure has to iterate between both algorithms in the following manner Solve the gas phase without particles perhaps for many sweeps Integrate the particle equations using the current gas field and compute the inter phase sources Solve the gas phase again including the new particle sources Repeat steps 2 and 3 until both sets of equations have converged SOLUTION OF THE PARTICLE EQUATIONS The numerical integration of the particle equations takes place according to the following sequence The Lagrangian time step is calculated The particle is moved The particle properties velocities temperatures etc at the new position are calculated The interphase source terms are calculated An overview of each of these steps will now be given The Lagrangian time step is estimated by GENTRA based on a user set fraction of the minimum cell crossing time This in turn is based on the minimum cell size and the maximum particle velocity component The particle is not allowed to jump more than one cell per time step At boundaries or blockages the particle is placed on the cell boundary by reducing the time step The new particle location x n is obtained by integrating the particle position equation as x n x 0 U 0p dt where x 0 and U 0p are the location and velocity vector at the start of the Lagrangian time step The integration is always performed in a Cartesian coordinate system At the new particle location the new values of local fluid properties are obtained and then the particle equations are integrated analytically For velocity components in Cartesian and polar grids the value at the particle location is obtained by interpolation from the neighbouring nodes For all other variables and velocity resolutes in BFC grids the cell centre value is used As particles traverse each cell exchange of heat mass and momentum may occur For example a particle traveling faster than the surrounding fluid will be decelerated and will in turn accelerate the fluid Sources expressing these interchanges are computed once the particle equations have been integrated They are stored and will be used the next time PHOENICS solves the gas phase equations IMPLEMENTATION IN PHOENICS Pre processing for GENTRA is carried out in the VR Editor main menu GENTRA itself is attached to PHOENICS as a GROUND station parts of which are not supplied in source It is divided into four main sections GENTRA which is called from GREX and contains the flow control Users are not normally expected to modify this GENIUS called from GENTRA This is a blank user routine for replacing or supplementing built in physical laws GPROPS also called from GENTRA It allows users to add in their own property laws for the particles and GENLIB the object library

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_lecs/genlec.htm (2016-02-15)
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  • GEOM.HTM
    to delete all elements See also GEOMETRY GEOMETRY DELETE GEOMETRY ON GEOMETRY READ GEOMETRY SAVE GEOMETRY CLEAR GEOMETRY CMDS GEOMETRY ON Photon Help GE ometry ON n switches on geometry element n where n may be an element number or ALL to delete all elements See also GEOMETRY GEOMETRY DELETE GEOMETRY OFF GEOMETRY READ GEOMETRY SAVE GEOMETRY CLEAR GEOMETRY CMDS GEOMETRY READ Photon Help GE ometry RE ad reads user geometry for display on the plot Geometry may be read in from a file or typed in from the keyboard If entry from the keyboard is desired press Return when the geometry file name is requested otherwise enter the file name To exit interactive geometry entry press Return until the Option prompt appears Geometry elements may be added to the currently stored elements using GEOM READ more than once See also GEOMETRY GEOMETRY DELETE GEOMETRY OFF GEOMETRY ON GEOMETRY SAVE GEOMETRY CLEAR GEOMETRY CMDS GEOMETRY SAVE Photon Help GE ometry SA ve filename saves the currently stored geometry elements into a file If no filename is given it will be prompted for A saved geometry file may be subsequently read in using GEOM READ See also GEOMETRY GEOMETRY DELETE GEOMETRY OFF GEOMETRY ON GEOMETRY READ GEOMETRY CLEAR GEOMETRY CMDS GEOMETRY CMDS Photon Help This is a brief description of the available geometry commands Further details appear in the PHOTON User Guide LINE x1 y1 z1 x2 y2 z2 dash colour x1 y1 z1 Cartesian coordinates of start of line x2 y2 z2 Cartesian coordinates of end of line dash Line type 0 solid line 1 4 broken lines Default solid line colour Line colour default default colour for device PLINE x1 y1 z1 x2 y2 z2 dash colour x3 y3 z3 x1 y1 z1 Cartesian coordinates of start of first

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/geom.htm (2016-02-15)
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  • GET.HTM
    cells along the line returns to CT3 the expression for the cell distribution returns to CT4 the string NONE for a straight line ARC for an arc or the curve name for a curve returns to RT1 RT2 and RT3 if the line is an arc the coordinates of the extra point on the arc returns to IERR the value 0 if the named line exists or 1 if it

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/get.htm (2016-02-15)
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  • GRAPH.HTM
    ANS LABEL TOP MESG DRAW A POLYGON DELAY 100 YFACTOR 1 25 RADIUS 0 2 ICOL 1 IDASH 1 NSIDES 9 MESG NO OF SIDES NSIDES OK IF NOT ENTER ANOTHER NUMBER READVDU NSIDES INT NSIDES NSIDES MESG RADIUS RADIUS OK IF NOT ENTER ANOTHER VALUE READVDU RADIUS REAL RADIUS RADIUS MESG COLOUR NUMBERS 0 BLACK 1 WHITE MESG COLOUR NUMBERS 2 DARK BLUE 3 LESS DARK BLUE MESG COLOUR NUMBERS 4 LIGHTER BLUE 5 LIGHT BLUE MESG COLOUR NUMBERS 6 BLUE GREEN 7 GREEN MESG COLOUR NUMBERS 8 GREEN YELLOW 9 YELLOW GREEN MESG COLOUR NUMBERS 10 YELLOW 11 YELLOW ORANGE MESG COLOUR NUMBERS 12 ORANGE BROWN 13 BROWN ORANGE MESG COLOUR NUMBERS 14 BROWN RED 15 RED MESG COLOUR NUMBERS 0 or 15 NOT ALLOWED MESG COLOUR NUMBER ICOL OK IF NOT ENTER ANOTHER NUMBER READVDU ICOL INT ICOL ICOL IF ICOL GT 16 THEN MESG ICOL MUST NOT EXCEED 16 GOTO TOP ENDIF MESG LINE NUMBERS 0 FULL 1 4 DASHED NOT AVAILABLE ON PC YET MESG LINE NUMBER IDASH OK IF NOT ENTER ANOTHER NUMBER READVDU IDASH INT IDASH IDASH TEXT NSIDES SIDED POLYGON X2 0 4 RADIUS Y2 0 5 ANGLE 0 DANGLE 2 0

    Original URL path: http://www.cham.co.uk/phoenics/d_polis/d_enc/graph.htm (2016-02-15)
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web-archive-uk.com, 2017-12-17