LOADIS Version 1.0

Synopsis

loadis

Description

The LOADIS program automatically computes force coefficients for a series of constant planes which intersect the surface of a specified component. The program requires an input grid file, solution file, and FOMOCO input file. The program will write out a file containing the force coefficients at each plane, and will write files containing the pressure coeffient and surface coordinates for each point in each cutting plane.

NOTE: The integrated forces computed by loadis are not the sectional forces, rather the loading forces as they are non-dimensionalized by the reference length, not the local chord. For example, the computed lift produced by loadis is cl_loadis = cl_sectional*c_local/Ref_l, where c_local is the local chord, and Ref_l is the reference length from the mixsur input file.

The FOMOCO input file is used to define the grid subsets which compose the surface of the chosen components of the configuration. The cutting planes may a series of constant x, y, or z planes. While LOADIS will perform cuts through the no-slip surfaces successfuly when the input grid file contains the entire volume grid(s), it works much faster if the input grid and solution files contain only the surfaces. Use the utilility script extractsrf and the programs SPLITMX and SPLITMQ to automatically create grid and solution files containing the surface subsets. When choosing the components for the cutting, it is best to use individual components that represent a single, complete, closed surface. If one uses a composite component that includes several bodies, such as a wing+flap+slat+body, the MINTERP sorting will not be able to discern between these different components, and the force integration will produce erroneous results.

Input

The LOADIS program prompts for the required input information. Command line parameters can be used for additional input options.

Input variables

    ICUT  =    cutting plane (1=x, 2=y, 3=z)

    NREG  > 0  number of regions to specify coordinate range and increment
          < 0  number of specified coordinates to make cuts
          = 0  auto determine minmax of region occupied by component

    If NREG>0, enter CS,CE,CINC for each region where

      CS   = start coordinate
      CE   = end coordinate
      CINC = increment

    else if NREG<0, enter CS for each cut where

      CS   = coordinate of cut

    else if NREG=0, enter NSTA where

      NSTA = total number of cuts including ends

    endif


Sample input file for NREG>0

input_grid_filename
input_solution_filename
fomoco_input_parameters_filename
fomoco_component_name

2                 ICUT(1/2/3)
2                 NREG
 5.0, 18.0, 0.5   CS, CE, CINC
20.0, 23.0, 0.5   CS, CE, CINC


Sample input file for NREG<0

input_grid_filename
input_solution_filename
fomoco_input_parameters_filename
fomoco_component_name

2                 ICUT(1/2/3)
-7                NREG
1.0
1.5
2.0
2.2
2.4
2.6
2.8     CS


Sample input file for NREG=0

input_grid_filename
input_solution_filename
fomoco_input_parameters_filename
fomoco_component_name

2                 ICUT(1/2/3)
0                 NREG
30                NSTA

Output

cpp_nnnxxx.dat

The pressure coefficient at each intersection point in each cut for each component is written to files called cp_nnnxxx.dat, where nnn = the component name and xxx = the sequential number of cut. This file contains four columns of data which contain x,y,z,cp, respectively.

loadnnn.dat

The integrated forces computed by loadis are not the sectional forces, rather the loading forces as they are non-dimensionalized by the reference length, not the local chord. For example, the computed lift produced by loadis is cl_loadis = cl_sectional * c_local / Ref_l, where Ref_l is the reference length from the mixsur input file. The integrated forces at each cutting plane for each component are written to files called loadnnn.dat, where nnn = the component name. This file contains five columns of data which contain the coordinate of the cutting plane, the coefficients of lift, drag, and side force (cl,cd,cs), and the local chord, respectively. The local chord for each cut is defined to be the distance from the first point in the cut to the point in the cut which is furthest away from the first point. The coefficients cl,cd,cs are computed from the forces in the body axes (fx,fy,fz) using:
cl =  -cfx*sin(alpha) + cfz*cos(alpha)
cd = ( cfx*cos(alpha) + cfz*sin(alpha) )*cos(beta) - cfy*sin(beta)
cs = ( cfx*cos(alpha) + cfz*sin(alpha) )*sin(beta) + cfy*cos(beta)

cfx = fx/(0.5*Ref_l*M_inf*M_inf)
cfy = fy/(0.5*Ref_l*M_inf*M_inf)
cfz = fz/(0.5*Ref_l*M_inf*M_inf)
were alpha = angle-of-attack, beta=yaw angle, Ref_l = reference length, and M_inf = freestream Mach number. These quantities are determined from the FOMOCO input file and/or the OVERFLOW solution file.

load_TOTAL.dat

This file contains the force coefficients summed over all the components. The file contains 4 columns of data: the coordinate of the cutting plane, and the force coeffcients of lift, drag, and side force.

WARNING: the code currently does not read the value of beta from the OVERFLOW solution file. Non-zero values of beta must be given by the FOMOCO input file.

Output gnuplot command file: gp.com (Inside gnuplot, type "load 'gp.com'")

See also

MINTERP : a stand-alone program which calls the cutting+interpolation subroutine used by LOADIS.

Authors: Stuart E. Rogers, William M. Chan, and Steven M. Nash


Last modified: Tue May 5 06:44:34 1998