HOW ITS DONE
AeroCFD ANALYSIS OF A COKE BOTTLE FLYING AT MACH 2
By
Wibo Crucq, The Netherlands

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AEROROCKETCAD SHAPE GENERATION
To generate AeroCFD shape files required for the Coke Bottle analysis, please
request your FREE copy of AeroRocketCAD if you previously purchased AeroCFD, Nozzle, AeroWindTunnel or AeroEuler.

PLEASE FOLLOW THIS PROCEDURE

1) To open and convert an AutoCAD DXF file previously generated using centimeter units, click File then click Open DXF Geometry. Please see Figure-1.
2) Find and click a .DXF drawing file previously created by AutoCAD. AutoCAD generated LINES and ARCS will appear in the lower left of the plot area.
3) Use ZOOM to enlarge the drawing and to make all segment numbers visible. If required use X-TRANSLATION and Y-TRANSLATION to make all segment numbers visible. Please see Figure-1.
4) In Highlight segments insert segment numbers that represent the fluid boundary. Use Highlight segments to note the location of all drawing file LINE and ARC entities that appear in the converted AutoCAD DXF drawing file. Please see Figure-1.
5) In the Vertical Text Box, enter LINE and ARC segment numbers that define the fluid boundary. The numbering sequence must be from left to right. However, it should not matter in what sequence the curves were generated in AutoCAD. Use CLEAR to start over. Simply backspacing will confuse the program and unpredictable shapes will occur. CLEAR must be used to start over. Remember, insert each segment number and then click Enter. Please see Figure-1.
6) To generate a AeroCFD, Nozzle etc. fluid boundary click the Generate fluid boundary in converted coordinates option button. No fluid boundary will be generated until the segment numbers are input using the procedure outlined in item 5. Please see Figure-2.
7) Convert centimeter units to meter units by clicking File, then AutoCAD Metric Units Conversion, and finally centimeters to meters.
8) Click File then Save XXX Geometry As ... to save the converted shape as an import file for use with AeroCFD, Nozzle, etc. Please see Figure-2.

When initially importing a new shape into AeroCFD, click File then Import Shape to input a geometry file created in AeroRocketCAD. Then, in AeroCFD define the flow and mesh parameters and save the project file by clicking File then Save Project As. Subsequently, to run a project and its associated airframe shape the shape file is imported first and then the project file is opened. Running a previously saved shape-project is performed by first clicking File then Import Shape and finally by clicking Open Project. Please wait for the shape and mesh parameters to be generated before performing each step. The data has the following format. First line: Total number of X-Y point locations, maximum of 1000 points. Second and subsequent lines: X, Y airframe locations separated by commas. A AeroCFD shape file defines the upper contour of an axisymmetric airframe geometry starting from nose-tip to the end of the airframe.


Figure-1, AeroRocketCAD screen after reading Coke_Bottle_DXF.dxf geometry and specifying boundary segments
 


Figure-2, AeroRocketCAD screen after generating fluid boundary, converting centimeters to meters and saving the AeroCFD shape file

AeroCFD ANALYSIS
AeroCFD is required to generate the CFD solution for the shape provided by AeroRocketCAD. Please purchase
AeroCFD to generate the following Coke Bottle solution.

PLEASE FOLLOW THIS PROCEDURE
In the
Fluid properties section define the following parameters. Please refer to the AeroCFD Instructions for more detail than can be provided here.


Figure-3, AeroCFD Fluid Dynamics Properties screen after reading Coke Bottle shape file, project file and specifying meters dimensions

In the Mesh Control section define parameters that control spacing and mesh distribution around the body. To achieve a successful CFD solution the user needs to define the mesh or system of grids defining the flow field around the model under investigation. In many cases an inappropriate selection of parameters in this section will cause AeroCFD to fail almost immediately often in less that 5 iterations after the user clicks the SOLVE button. For example, the mesh distribution appropriate for a successful supersonic flow CFD analysis is probably completely inappropriate for a successful subsonic flow CFD analysis. However, by following a few simple conventions a good solution can be achieved after a few attempts. Please refer to the AeroCFD Instructions for more detail than can be provided here.


Figure-4, AeroCFD Mesh Controls screen defining mesh dimensions

To control how AeroCFD solves the flow around the body, define the following parameters in the Solution Controls section. Please refer to the AeroCFD Instructions for more detail than can be provided here. Click SOLVE when ready to continue.


Figure-5, AeroCFD Solutions Control screen specifying solution parameters

Plot using the Plot Results section. AeroCFD generates contour-filled plots, contour-line plots and surface parameter distribution plots in the axial and circumferential directions along the body. Please refer to the AeroCFD Instructions for more detail than can be provided here. Click PLOT FILLED LEVELS when ready to continue.


Figure-6, AeroCFD Results screen displaying Pressure Ratio (P/Pinf) contour color plot


Figure-7, AeroCFD Results screen displaying Mach number contour color plot
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