AeroCFD®  7.0 ($90.00) A Model Rocket CFD Program for Microsoft Windows By AeroRocket | Buy On-Line | Add To Cart | Step-By-Step Instructions AeroCFD Instruction Manual V-2 Rocket Example

AeroCFD & 2D-Wing Customer Comment OVERALL REVIEW (AeroCFD 7): Amazing, professional quality. Wow, your software design (hands on, simple honest calcs of Mother nature's basics) and references (Hoerner, Anderson, Sutton, etc.) are rock solid, and refreshing after all the $30,000-stuff I've had to shovel through so far. The packages are working amazingly ... Sean P. Staph 45th Space Wing Patrick AFB, Florida 10/2006

AeroCFD is a computer program written using Microsoft Visual Basic 6. AeroCFD is interactive allowing the rocketeer to quickly and easily perform CFD design studies using the power of the Windows Graphical User Interface. AeroCFD uses vortex and source panel methods to solve the frictionless potential flow equations and employs linearized theory to compute compressible flow up to Mach 0.80. Meshing the flow field is very simple with AeroCFD. The user simply inputs model rocket geometry such as nose cone type, nose cone length and body tube diameter. Then, AeroCFD automatically meshes the computational domain, as it is called, with thousands of panels that break the flow field into discrete elements for use by the 2nd order vortex and source panel methods. Then, once the results are computed AeroCFD provides the rocketeer with a complete set of visualization tools to make interpretation of the complex flow field results simple. For example, color velocity and pressure contour plots allow the rocketeer to quickly and easily visualize complex flow around the model rocket. In addition, a simple and efficient fin geometry utility allows the rocketeer to quickly specify fin and launch lug dimensions. Then, using source and vortex panel methods the rocketeer can determine contribution of the fins to overall center of pressure and the effects of fin geometry on overall rocket stability, drag and lift. The vortex panel analysis for fins and body is a real break through for model rocket design and the visualization of the rocket's flow field is a unique feature not available anywhere else but in AeroCFD. AeroCFD is able to more accurately determine FOREBODY and BASE drag coefficients than the DATCOM methods used by various Rocket Simulation programs which translates into more reliable and accurate flight predictions.

AeroCFD 7 includes a completely new routine called 2D-WING for the determination of wing section aerodynamics. 2D-WING determines drag coefficient (CD), lift coefficient (CL) and moment coefficient (Cm,c/4) of airfoil sections using the NACA four digit series, Streamlined, Flat Plate, D'Wedge and Imported shapes for a wide range of fin/wing shapes. Presently, several five-digit series airfoil shapes from Theory of Wing Sections, Appendix III have been provided in the file, NACA_AIRFOILS.zip to allow the user to specify more complex airfoil shapes. Over the next several months the entire contents Theory of Wing Sections, Appendix III will be included. For those who purchase AeroCFD 7 the final version of NACA_AIRFOILS.zip will be emailed upon completion.

CFD BACKGROUND THEORY
The panel method procedures used by AeroCFD are far more sophisticated than any other numerical method previously available to determine model rocket aerodynamic performance. The solution of inviscid and incompressible flow over complex three-dimensional fin and body combinations is achieved using three-dimensional panel methods. The body of the rocket is covered with thousands of source panels that each have an unknown source strength. The main thrust of the panel method numerical analysis technique is to solve for each panel's source strength such that the body becomes a streamline of the flow. The boundary condition that makes the body a streamline of the flow is achieved numerically by defining the midpoint of each source panel as a control point. Each panel's source strength is determined such that the normal component of velocity (Vn) is zero at each control point. For lifting surfaces such as fins vortex panels are used instead of source panels. Flow circulates around the vortex panel's control point and provides the circulation necessary to achieve lift. Finally, to achieve the correct solution the Kutta boundary condition is imposed at the trailing edge of each fin. This is all performed automatically within AeroCFD. However, because AeroCFD assumes the flow is inviscid (frictionless and irrotational) separated flow, vortical effects and stall conditions are not modeled for high AOA. That is, AeroCFD does not correctly model separated flow for AOA greater than 15 degrees over the fins and airframe. Finally, the huge size of the solution matrix require solution times that range from a few seconds for a 10X10 fluid dynamic analysis to about 5 minutes for a 100X100 analysis on a Pentium 4 computer. AeroCFD is useful to determine flow field effects around any model rocket and is very simple to use. Unlike commercial CFD codes that can cost many thousands of dollars to purchase or lease, AeroCFD is a real cost break through for the model rocketeer.

HISTORY OF AEROCFD
Defining the flow field around complex shapes is possible using a technology called Computational Fluid Dynamics or CFD. CFD is an approximation procedure for determining the characteristics of fluid flow around any complex shape. The procedure involves subdividing the flow field around the rocket into many smaller regions using convenient shapes, such as triangles and quadrangles and using either panel methods or finite volume methods to determine the physical behavior of the flow field within and around each element.

Applying basic CFD theory, in 1986 John Cipolla developed an airframe panel method subroutine called AeroPanel and the program which utilized the subroutine, was called AeroCFD. Today, AeroCFD uses source panel methods for the airframe and vortex panel methods for the fins to determine velocity and pressure around the rocket. Knowing the distribution of pressure and velocity on the rocket surface allows AeroCFD to compute the center of pressure location (Xcp) using standard force and moment relationships. With AeroCFD a rocketeer can actually visualize why the center of pressure moves forward with increasing angle of attack for subsonic flow. This level of model rocket analysis has never been possible before with any commercially available product.


VALIDATION CASE #1: V-2 ROCKET CD AND CL
AIRFRAME GENERATED USING FREE-FORM GEOMETRY
A V-2 rocket was modeled using dimensions of the A4/V-2 rocket from "Rockets of the World", by Peter Alway. AeroCFD 6.3 results for drag and lift were then compared to the drag (CD) and lift (CL) coefficients in Figure 5-3 on page 126 of "Rocket Propulsion Elements", Sixth Edition by George P. Sutton. Because AeroCFD is essentially a subsonic analysis computer program based on subsonic panel methods, a single velocity point located at Mach = 0.25 was selected for comparison. Data points from Figure 5-3 were digitized to determine V-2 rocket drag coefficient (CD) verses Mach number at 0.0, 4.0, 6.0 ,8.0, and 10.0 degrees angle of attack (AOA). Similarly, data points from Figure 5-3 were digitized to determine V-2 rocket lift coefficient (CL) verses Mach number at 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 degrees angle of attack. Drag and lift data from Figure 5-3 were modified to include jet effects. Rocket motor jet effects cause the drag and lift coefficients to be increased slightly in the subsonic regime and decreased slightly in the supersonic regime. For subsonic flow the drag increase is caused by jet-induced flow over the body and fins and the related increase in surface friction. Modified drag and lift data from Figure 5-3 is shown plotted with AeroCFD results for the V-2 rocket in Figure-1 below. The reference area used to define the drag coefficients is the maximum cross-sectional area of the airframe as stated on page 125 of "Rocket Propulsion Elements". Both drag and lift AeroCFD results agree reasonably well with modified Sutton V-2 drag and lift data. AeroCFD lift coefficient (CL) results exactly match modified Sutton V-2 data up to approximately 5 degrees angle of attack and then begin to depart from the modified V-2 data. The departure between the AeroCFD results for CL and the modified Sutton V-2 CL data beyond 5 degrees is expected because AeroCFD does not model separation effects as the gradients in the flow field become large and viscous effects predominate. AeroCFD drag coefficient (CD) data track the modified Sutton CD results over the entire range from 0.0 degrees to 12 degrees angle of attack. AeroCFD was configured to model compressible flow for these analyses as explained in the operating instructions. These results were produced by AeroCFD using the same sequence of steps described in the operating instructions. If more accurate subsonic and supersonic missile performance data is required please consider VisualCFD. GO

Figure 1: AeroCFD and Modified Sutton Drag and Lift Data (Includes Jet Effects)

AEROCFD V-2 RESULTS SCREEN SHOTS

Figure-2: AeroCFD Input Data (Screen Size Reduced to 65%)


Figure-3: AeroCFD Results (Screen Size Reduced to 65%)


Figure-4: V-2 Dynamic Pressure Contour Plot With Line Contours (Screen Size Reduced to 65%)


Figure-5 V-2 Airframe Filled-Contour Cp Plot (Screen Size Reduced to 65%)


VALIDATION CASE #2: MODEL ROCKET ZERO LIFT DRAG (CD)
Because AeroCFD is primarily a model rocket performance prediction computer program, the following is a comparison with wind tunnel test data for a model rocket type design. A comparison is made between results from the NAR paper, "Model Rocket Drag Analysis" by John S. Demar and results produced by AeroCFD 6.3 for a model rocket configured with rounded fins and varying surface finish. Coincidentally, AeroCFD and the DeMar paper specify three finish types, unpainted, painted and polished. For this comparison the AeroCFD drag coefficient results were determined at 80 km/hr (72.9 ft/sec), 100 km/hr (91.13 ft/sec) and 120 km/hr (109.36 ft/sec) to correlate with the wind tunnel results in the paper. However, for this comparison the Demar wind tunnel drag coefficients were derived from the tabulated drag-mass data that correspond to the measured zero-lift drags. The tabulated drag coefficient data was not used because the paper's CD's were based on a reference area that included fin frontal area. Wind tunnel drag force for each drag measurement was computed using the equation, Fdrag = Mdrag * g. The drag coefficient for each finish type and velocity was computed using the standard equation, Cd = Fdrag / (0.5 * density * V^2 *Ax). Where the reference area, Ax is the maximum body tube cross-sectional area not the total frontal area of the body tube and fins as described in Demar's paper. The drag reference area (Ax = pi /4 * D^2) is computed using the 0.75 inch diameter specified in the paper "as the standard body" diameter for determination of CD. Finally, this analysis used the "Standard Model Design" as specified in the paper and three 0.06 inch thick fins. The air density is 1.226 kg/m^2. Results from this comparison indicate excellent agreement between the zero-lift drag coefficients determined in section 2.3 of the paper for three types of finishes at three different rocket velocities. Figure-6 presents the results of the comparison.

Figure-6: Drag Results Compared. Note: Drag coefficient indicated by (*) does not fit trend, possible wind tunnel measurement error.



Figure-7: Cd verses Velocity, No Finish, Painted Finish and Polished Finish, Rounded Fins (Note Laminar-Turbulent Transition)
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AEROCFD REVISIONS
AeroCFD 7.0 Features
1) Made AeroCFD 2D-WING a stand alone routine winthin AeroCFD with many enhancements.

AeroCFD 6.4 Features
1) Compute average drag coefficient (CD) over a range of velocity, then use in any other flight simulation program for more accurate results.
2) Improved Fin Panel method output including NACA designations for symmetrical NACA fins.

AeroCFD 6.3 Features
1) Added the capability to define elliptical, parabolic, and tangent ogive transitions to define the shape of the rocket in addition to the previous capability to model conical transition shapes.

AeroCFD 6.2 Features and Fixes
1) Added the capability to plot surface filled-contour plots.
2) Added a locator that displays the 3-D location of displayed values for dynamic pressure, static pressure, pressure coefficient (Cp) and velocity on the surface of the airframe.
3) Improved AeroCFD accuracy in the way pressure is summed to determine drag and lift coefficients and forces.
4) CFD looping and Cp plots display most tick mark values for better interpretation of plot results.
5) Added the capability to model laminar and turbulent skin friction drag and laminar-turbulent transition.
6) Added the capability to model fin base drag effects.
7) Fixed an error involving the summation of fin vortex panel forces for the determination of drag and lift.
8) Fixed an error involving the summation of airframe source panel forces for the determination of drag and lift.

AeroCFD 6.1 Features and Fixes
1) Filled contours would not plot when the vertical trailing edge of the fins exactly lined up with the base of the body tube.
2) Increased maximum mesh size from 50X50 to 100X100. Results for higher mesh size provide better resolution in high curvature areas of the airframe.
3) Increased filled contour plot speed. Generate filled-contour plots 4.5 times faster than version 5.2.
3) Improved color levels by making the color distribution similar to the color spectrum of light (red, yellow, green, light blue and blue).
4) Moved and resized the color levels bar so it is always visible on the plot.

AeroCFD 5.0 Features and Fixes
1) A new interface makes AeroCFD easier to use. The contour plots and mesh plots fill the entire screen and are resizable. Every screen has been modified to the new format.
2) Program crashed when Units were modified when no velocity was specified by the user.
3) Cleaned up line contour plot results near the rocket surface. For slender bodies and bodies at high AOA the line contours became jumbled for numerical reasons.
4) The Navier Stokes results for base flow drag were not reflected in the overall drag and lift results on the main screen.

AeroCFD 4.5 Features and Fixes
1) Allowed AeroCFD to display drag coefficient in the flight direction (CD), lift coefficient perpendicular to the flight direction (CL), drag coefficient in the axial direction of the rocket (CX), and lift coefficient perpendicular to the axial direction of the rocket (CY).
2) Fixed the errors that may occur if the user specifies velocity greater than 0.80 Mach when also specifying the flow as compressible. Mach number or velocity now correctly displayed on the looping analysis for this error condition.

AeroCFD 4.3 Features and Fixes
1) Fixed a bug in the Free-Form Body Tube Geometry screen. The last point on the body tube could be lifted off the base of the body tube. While this may generate some interesting geometry, the results are unpredictable. Having the last body tube point lift off the base is not a problem if the user simply places the last point on the base manually or realizes the resulting geometry is interesting but inaccurate.
2) Developed a new utility called XML File Fin Geometry and Fin Placement. AeroCFD can import standard and Free-Form or custom XML fins.
3) Fixed the scroll bars so when pulled the user gets immediate feed back on the screen. In this case the fins move as the scroll bar is moved and fin location is updated in real-time in a data box. Fixed this feature everywhere it is used in AeroCFD and FinSim. In AeroCFD this fix is located on the Flow Visualization screen and the new screen mentioned in item 2)
4) Set the dimensional units initially in units of inches, pounds and seconds as opposed to feet, pounds and seconds in the previous versions of AeroCFD.
5) Added a graphical description with text to instruct the user in the use of the XML File Fin Geometry and Fin Placement screen. These instructions are located in the CFD Instructions and Help screen.
6) Fixed a numerical formatting problem where if a number like a fin dimension was zero only a point (.) would appear. Now, if a dimension is zero, a (.0) appears to signify that a dimensional length is zero.
7) On the Fin and Launch Lug Geometry screen increased the length of each data field to fit very large or very small dimensions.
8) Brought back the Element Aspect Ratio pull-down option. This feature can increase the aspect ratio from 1:1 to 1:2, 1:3, or 1:4. Increasing the element aspect ratio is useful to cluster elements around the body tube and to get better plot resolution in regions where flow velocity and pressure are changing rapidly. Also, clustering the elements is important when trying to plot line-contours around rocket tubes that have large length to diameter (L/D) ratios. In addition, getting enough elements near the body tube is important for accurate line-contour plots. Therefore, this new/old option is very important.

AeroCFD 4.2 Features and Fixes
1) Fixed the Body Tube Free-Form screen so the points stay fixed where the user specifies them.
2) Now, The Body Tube Free-Form screen allows the user to move points anywhere on the screen. AeroCFD will attempt to fix the geometry to something it understands if the user specified crossed-points or impossible geometry.
3) Added a new line-contour plot feature. AeroCFD now plots 100 level line contour plots in less than 2 seconds. In addition, the line-contour plots can be superimposed on the fill-contour plots very easily, with a click of a button.
4) Cleaned up the plot screen so some text is not lost on some users screens.
5) For impatient users AeroCFD now shows fill-contour plots and line-contour plots as they are being generated, element-row by element-row. Its looks pretty neat, and gives the user something to look at while the plot is being generated.
6) Added a "STOP" plot button that gives the user the option to end the contour plot being generated or to continue with the plot.
7) Fixed the error that occurred when the user "clicked" on the plot screen when one of the contour plots were being generated. The screen would "freeze" but continue plotting in the background. Now, the user may click the screen but the plots continue to be processed on the screen in full view.

AeroCFD 4.1 Features and Fixes
1) Clicking the contour plot will enlarge the plot in a separate window. Then, clicking the large contour plot closes the screen and returns the user to the main contour plot screen.

AeroCFD 3.6 Features and Fixes
1) New simplified layout allows the user to define geometry and perform CFD analyses quickly and easily.
2) Perform fin and nose-body CFD analyses on the main screen with a single click of the Solve command button. Then, see Cd, CN, and CM displayed on the main screen when analysis is complete. All drag coefficients continue to be displayed on the main screen.
3) Define Standard Geometry body tube shapes and see generated in real time.
4) Generate axi-symmetric body tube shapes using the new Free-Form method. The user simply defines the total number of points describing half the body tube and then generate any arbitrary shape by dragging the points into position with the mouse.
5) Perform up to 360 CFD Looping analyses and generate Cd, CN, CM and XCp as a function of angle of attack (AOA) or velocity by specifying initial conditions and increments. Save data in comma-delimited text format or print data directly to the printer.
6) Plot Barrowman equation CN, CM and XCp for Standard Geometry with results plotted by the CFD Looping analysis.
7) Read older AeroCFD data files and convert them into AeroCFD 3.6 format.
8) Direct display of Drag forces acting on nose-body tube, fins, and launch lugs. In addition, direct display of lift force acting on the fins at some specified angle of attack.
9) On the main analysis screen the total drag coefficient (Cd) referenced to the area at the base of the nose cone is displayed. In addition, the total drag coefficient (Cd) referenced to the maximum cross-sectional area of the rocket is displayed for comparison.
10) AeroCFD 3.6 is compiled in Native Code for a speed increase of 25 percent to 30 percent.
11) Multi-fin analysis for canard and main fin combinations.
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For more information about AeroCFD please contact AeroRocket at john@aerorocket.com.

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