




        1) User information for LAVENT computer program

        This disk contains a number of files pertaining to the computer
        program, LAVENT, and an associated graphics program, GRAPH,
        developed by the Center for Fire Research at the National Institute
        of Standards and Technology.  A brief description of the programs
        are provided below.

        LAVENT is a program developed to simulate the environment and the
        response of sprinkler links in compartment fires with draft curtains
        and fusible-link-actuated ceiling vents.  The model, used to
        calculate the heating of the fusible links, includes the effects of
        the ceiling jet and the upper layer of hot gases beneath the
        ceiling.  The required program inputs are the geometrical data
        describing the compartment, the thermophysical properties of the
        ceiling, the fire elevation, the time dependent energy release rate
        of the fire, the fire diameter or energy release rate per area of
        the fire, the ceiling vent area, the fusible link response-time-
        index (RTI) and fuse temperature, the fusible link positions along
        the ceiling, the link assignment to each ceiling vent, and the
        ambient temperature.  A maximum of five ceiling vents and ten
        fusible links are permitted in the compartment.  The program outputs
        are the temperature, mass and height of the hot upper layer, the
        temperature of each link, the ceiling jet temperature and velocity
        at each link, the radial temperature distribution along the interior
        surface of the ceiling, the radial distribution of the heat flux to
        the interior and exterior surfaces of the ceiling, the fuse time of
        each link, and the vent area that has been opened.  LAVENT is
        supported by two-part documentation which includes: Part I - Theory,
        L.Y. Cooper; and Part II - User Guide, W.D. Davis and L.Y. Cooper. 
        LAVENT was written in FORTRAN by W.D. Davis and L.Y. Cooper.

        GRAPH is a graphics program which runs in conjunction with LAVENT. 
        The results for LAVENT are sent to the data file, GRAPH.OUT, after
        each prescribed time step.  GRAPH then allows the user to choose two
        sets of variables to be plotted on the screen and has the additional
        capability of hardcopy output.  GRAPH was written in FORTRAN by
        W. D. Davis.


        2) LAVENT FILES

        The following files pertain to the LAVENT program

        Files on DISKL01

        LAVENT.EXE     The compiled form of the LAVENT program
        LAVENT.TXT     The Users Guide for the LAVENT program
        LAOVR.TXT      An overview of the model simulated by LAVENT
        F77L.EER       FORTRAN run time error messages
        DISKL01.TXT    This text file.
        READL01.BAT    Batch file to display file DISKL01.TXT one screen at
        a time.





        USERINFO.TXT   General user information.


        Files on DISKL02

        GRAPH.EXE      The compiled form of the graphics program, GRAPH.
        DISKL02.TXT    This text file.
        READL02.BAT    Batch file to display file DISKL02.TXT one screen at 
        a time.
        USERINFO.TXT   General user information.
        LAVENT.FOR     Fortran Source Code


        2.1) LAVENT.EXE 

        This is a compiled version of the LAVENT program and is run by
        typing LAVENT (with the appropriate disk drive letter if necessary)
        after a system prompt.  This file was generated with the Lahey 77
        FORTRAN compiler and requires a math coprocessor to run the program. 
        It will take roughly 90 minutes to run the default case on an IBM
        AT.

        2.2) LAVENT.TXT

        This file contains a copy of NISTIR 89-4122 which is the users guide
        for LAVENT.  A hardcopy of this document may be obtained by typing
        PRINT LAVENT.TXT.

        2.3) LAOVR.TXT

        This file contains an overview of the model simulated by LAVENT.  A
        hardcopy of this document may be obtained by typing PRINT LAOVR.TXT.

        2.4) GRAPH.EXE 

        This is a compiled version of the GRAPH program and is run by typing
        GRAPH (with the appropriate disk drive letter if necessary) after a
        system prompt.  This file was generated with the Lahey 77 FORTRAN
        compiler and requires a math coprocessor to run the program.

        2.5) LAVENT.FOR

        The FORTRAN source code for version 1.2 is now available.  The source
        code will compile using Lahey 77 FORTRAN.  A number of warning messages
        will be generated during the compile and link processes 
        due to the use of the solver DDRIVE2 which is part of a more general solver 
        package DDRIVE3.  The warning messages refer to the DDRIVE3 part of the 
        solver which is not implemented in LAVENT.  One warning which is not 
        associated with the solver refers to an unused variable YCEIL in subroutine 
        PLUME.  This variable is associated with a commented out code segment 
        which would allow the user to calculate the flame height produced by 
        the fire in order to see if flames were touching the ceiling.  


        3.) REVISION HISTORY

        3.1) Version 1.1  7/30/90

        The following changes have been made to LAVENT 1.0 in order to
        correct some bugs in the program and to provide the user with some
        options to increase the running speed of the program.

          The output file has been corrected such that the proper values for
          the ceiling heat capacity and ceiling density are printed out.  In
          version 1.0 of LAVENT, these values were reversed such that the
          ceiling density was given the ceiling heat capacity value and the
          ceiling heat capacity the ceiling density value.  See page 26 of





          the users guide.  This bug only affected the output file and did
          not affect any of the computed values of the program variables.  

          The default values for the density, heat capacity, and thermal
          conductivity of wood have been changed to the values for plywood
          made of pine with a 10% moisture content as reported in NBSIR 85-
          3223.

          Two of the values used to express the fire power/area, PE BOTTLES
          and PS JARS, were expressed correctly in the menu choices but were
          given different values when displayed in the variable lists and
          used in the computations.  This is now done correctly.

          The file, TEST, which was opened but not used has been eliminated.

          The option to save the file but not run the code now works
          properly.

          A new option is available which allows the user to change one or
          more of the fusible link properties without having to input all
          the properties for a single link.

          A correction of an equation in the theory document NBSIR 88-3734
          has resulted in a correction of the corresponding equation in the
          code.  This correction consisted of replacing yFIRE with yEQ in
          equation 32' of NBSIR 88-3734.  This equation was expressed in
          correct form in equation 32 of the same document.  The computer
          program, LAVENT, was modified to include this correction.  The
          default was rerun and the results are available on the CFR
          bulletin board.  While the effect of this change was not
          substantial for the default case, care must be exercised when
          quoting results using the earlier version of LAVENT. 

        The following three additions were made in order to provide the user
        with a means to increasing the running speed of the program. 

          The first addition allows the user to use fewer than the number of
          ceiling grids internally chosen by the program.  Since most of the
          program time is spent calculating the heat flow to the ceiling, by
          reducing the number of ceiling grids can substantially reduce the
          running time of the program.  

          To change the number of ceiling grids, choose option 6 in the base
          menu, SOLVER PARAMETERS.  Option 5 of the solver parameters menu
          will permit the maximum number of grids to be set to an integer
          value between 2 and 50.  Any entry greater than 50 will be set
          equal to 50.  Any entry less than 2 will be set equal to 2.  The
          number of annuli representing the ceiling equals the number of
          ceiling grids minus one.

          The second addition allows the user to choose the type of solver
          used to do the computations.  The variable to change is MINT which
          is also found in the SOLVER PARAMETERS menu.  Choose option 6 to
          get this menu.  Selection 6 of this menu then provides a prompt





          for MINT to be set equal to 1, 2, or 3.  The default value is 3. 
          Setting MINT to 1 uses the Adams Methods to solve the problem
          which is a non-stiff solver.  Setting mint to 2 uses the Stiff
          Methods of Gear to solve the problem which is a stiff solver. 
          Leaving MINT at three allows the program to dynamically select
          which of the two solvers are more appropriate.  For a number of
          problems that have been tried with LAVENT, setting MINT to 1 may
          substantially reduce the running time of the problem. 

          The third addition allows the user to increase the value of the
          smallest physically meaningful value used for the solution by the
          solver.  In LAVENT 1.0, this value was set equal to 0 while in
          LAVENT 1.1, this value is set equal to 1E-8.  The user may change
          this value in LAVENT 1.1 by entering the SOLVER PARAMETERS menu
          and using option 7 to change this value.  In some cases, the
          running time of the program may be reduced but the major decrease
          in running time has already been obtained by changing the default
          value from 0 to 1E-8.  Users may find that with this new default
          value, LAVENT runs twice as fast as with the old default value.

        3.2) Version 1.2 12/18/96

          A modification has been made to the ceiling jet algorithm to account
          for the possibility that the upper layer has not covered the fusible
          link.  When the upper layer thickness is less than the distance that
          the fusible link is located beneath the ceiling, the ceiling jet 
          temperature excess is calculated starting at the ambient temperature.  
          Once the layer has covered the fusible link, the ceiling jet
          temperature excess is calculated starting at the upper layer 
          temperature.  
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